mover will be forced to match their speed and position to be or become identical with the ... frequency matching, and provides the breaker closing output contact.
EMPIRICAL IMPLEMENTATION OF INTERNET OF THINGS BASED TRANSACTIVE ENERGY AND INTELLIGENT CONTROL AUTOMATION FOR POWER GENERATION A PROJECT REPORT Submitted by
KIRAN RAJ. R
412512105036
LILLI PRASATH. J
412512105041
DRAVIA VEMAL. M
412512105307
In partial fulfillment for the award of the degree Of
BACHELOR OF ENGINEERING in ELECTRICAL AND ELECTRONICS ENGINEERING
SRI SAI RAM ENGINEERING COLLEGE CHENNAI – 600 044
ANNA UNIVERSITY::CHENNAI 600 025 APRIL 2016
ANNA UNIVERSITY::CHENNAI 600 025 BONAFIDE CERTIFICATE Certified that this project report “EMPIRICAL IMPLEMENTATION OF INTERNET OF THINGS BASED TRANSACTIVE ENERGY AND INTELLIGENT CONTROL AUTOMATION FOR POWER GENERATION” is the bonafide work of
KIRAN RAJ. R
412512105036
LILLI PRASATH. J
412512105041
DRAVIA VEMAL. M
412512105307
who carried out the project work under my supervision.
SIGNATURE
SIGNATURE
Prof. AL. KUMARAPPAN
Prof. AL. KUMARAPPAN
Head of the Department
Head of the Department
Department of EEE
Department of EEE
Sri Sairam Engineering College
Sri Sairam Engineering College
West Tambaram, Chennai – 44.
West Tambaram, Chennai – 44.
Submitted for VIVA-VOCE Examination held on ____________
Internal Examiner
External Examiner
ACKNOWLEDGEMENT
We take immense pleasure in expressing our sincere thanks to our respected Founder and Chairman Thiru. MJF. Ln. LEO MUTHU, our Chief Executive Officer Mr. J.SAI PRAKASH and our Principal Dr. C.V. JAYAKUMAR for their encouragement and all the facilities provided for carrying our project. We feel extremely happy to convey our genuine thanks to the Head of the Department Prof. AL. KUMARAPPAN, for his support throughout this project. We express our profound gratitude and deep regards to our internal guide, Prof. AL. Kumarappan, Head of Department, for his exemplary guidance, monitoring, constant encouragement and whole hearted support throughout the course of the project. We express our sincere thanks to our Project Coordinators Mr. SIVAPRASAD, Mr. Prathik and Ms. Ajitha for their valuable suggestions and their support. We also thank all the faculty members, non-teaching staff of our department and our parents and friends, who offered an unflinching moral support for the completion of the project. Finally, we are grateful to God Almighty for giving us the grace to complete the project successfully.
ABSTRACT The modern power systems incorporate the idea of load sharing by multiple generators and isolated generators are a very rare occurrence. Nowadays power plants are highly interconnected by employing multiple transmission and distribution strategies. The tricky part of the inter network is synchronizing of the new generators to an existing bus. The parallel operation of generators involves certain prerequisites like the source generator must have equal Line Voltage, Frequency, Phase Sequence, Phase Angle, and Waveform to that of the system to which it is being synchronized. The term "transactive energy" is used here to refer to techniques for managing the generation, consumption or flow of electric power within an electric power system through the use of economic or market based constructs while considering grid reliability constraints The proposed work involves development of a cloud based automatic synchronizing device for the parallel operation of the generators with remote access to the power system. An advanced supervisory control and data acquistation interface with the concept of Internet of Things is established for real time monitoring and data analysis. The recent development in Internet of Things has enabled Time based Metering for the power consumed and direct consumer integration. Vital physical conditions like vibration and temperature of the generators are also taken into account to enhance the generator’s efficiency. The project finds its applicability in micro grid integration which paves way for intelligent grids in the future. One major benefit is data and communications that enable customer-side resources to participate in electricity programs—i.e., transact with the electric grid. IV
TABLE OF CONTENTS
CHAPTER NO.
1.
2.
3.
4.
TITLE ABSTRACT
IV
LIST OF FIGURES
VIII
LIST OF TABLES
IX
LIST OF ABBBREVATIONS
X
INTRODUCTION
1
1.1
1
GENERAL
SCADA (Supervisory Control and Data Acquisition)
2
PARALLEL OPERATION OF GENERATORS
4
3.1
4
Conditions for parallel operation
SYNCHRONIZATION
5
4.1
Definition
5
4.2
Damage in case of asynchronization
5
4.2.1
System Problems
6
4.2.2
Generator damage
6
Synchronizing methods
8
Manual Synchronizing
8
4.4
Synchroscope
10
4.5
Automatic Synchronizing
12
4.3 4.3.1
5.
PAGE NO.
INTERNET OF THINGS 5.1
Internet of Things in Power System
14 14
6.
5.2
Internet of Things Energy
5.3
The Concept of Smart Grid and Internet of Things 15
5.4
Power Monitoring
16
TRANSACTIVE ENERGY GRID
18
6.1
Introduction
18
6.2
Working of Transactive Energy
19
6.3
Attributes of Transactive Energy
20
6.4
Differentiation of Transactive Energy from Smart Grid
21
Need for transactive energy
23
6.5 7.
DEMAND RESPONSE
25
7.1
Demand Response
25
7.2
Types of Demand Response
26
7.3
Tariff Options
27
7.4
Program Options
28
7.5
The Role of Demand Response in Electric Power Systems
29
Benefits of Demand Response
31
7.6 8.
15
CIRCUIT DIAGRAM
34
8.1
Overall Block Diagram
34
8.2
Overall Circuit Layout of the Proposed System
35
8.3
Arduino Uno
36
8.4
Raspberry Pi 2 - Model B
37
8.5
Development of Voltage Sensor Using Voltage Divider Circuit
39
Development of Auto Synchronizer
40
8.6
9.
10.
8.7
Proximity Sensor
41
8.8
Current Sensor
42
WORKING OF AN INDIVIDUAL GENERATOR
43
9.1
Stepper Motor Control
43
9.2
Relay Circuitry
44
9.3
Voltage and Current Sensor
44
MATLAB SIMULATION
46
10.1
Matlab Simulation using SimPowerSystem
46
10.2
Simulation Output Results
47
10.3
Matlab SimPowerSystems
48
11.
CONCLUSION
49
12.
FUTURE WORK
50
REFERENCES
51
LIST OF FIGURES FIGURE NO.
TITLE
PAGE NO.
4.1
Connecting two generators
5
4.2
A wiring diagram for the parallel operation of the two alternators
8
4.3
Manual synchronizing
10
4.4
Synch-Check block diagram
11
5.1
Applications of Internet of Things in Smart Grid
17
6.1
Working Model of Transactive Grid
20
8.1
Block Diagram
34
8.2
Overall Circuit Layout of the Proposed System
35
8.3
Arduino and pin diagram
36
8.4
Location of connectors and ICS on Raspberry Pi 2
38
8.5
Voltage Sensor using Voltage Divider Circuit
39
8.6
Development of Auto Synchronizer using Arduino Uno
40
8.7
Inductive Type Proximity Sensor
41
8.8
Current Sensor
42
9.1
Rheostat arrangement for automatic variable control
43
10.1
Physical Modelling using SimPowerSystems
46
10.2
Simulation output (scope values)
47
VIII
LIST OF TABLES TABLE NO.
TITLE
PAGE NO.
6.1
Attributes of Transactive Energy
21
6.2
Comparison between existing grid and smart grid
22
IX
LIST OF ABBREVIATIONS
DC
-
Direct Current
AC
-
Alternating Current
IC
-
Integrated Circuits
IOT
-
Internet of Things
IOTE
-
Internet of Things Energy
TE
-
Transactive Energy
DR
-
Demand Response
PLC-
-
Programmable Logic Controller
SCADA
-
Supervisory Control and Data Acquisition
RTU
-
Remote Terminal Unit
LAN
-
Local Area Network
WAN
-
Wide Area Network
IDE
-
Integrated Development Environment
X
CHAPTER 1 INTRODUCTION 1.1 General
Electrical power system mainly consists of a generator, transmission lines, and supplies large numbers of widely distributed loads. In many cases, there is a need to connect more than one generator to the system. Some of the benefits of operating multiple generators in parallel include increased reliability, expandability, flexibility, serviceability and efficiency. Parallel operation allows operating generators around their rated load resulting in operating with high efficiency.
When connecting a generator to an interconnected system containing many other generators, the voltage, phase and frequency at its terminals should meet the operating ones. Severe damage to the generator as well as system disturbances may result if the generator is allowed to connect to the system outside of established safe levels. Therefore, the automatic synchronizing device plays an important role in the generator synchronizing. For many years, the researchers have paid great attention to develop the high performance-synchronizing device.
The main problems of connecting a synchronous generator to an electrical system to establish safe limits for each of the delta phase angle, the delta frequency, and the delta voltage magnitude.
Synchronization of two generators or more means that their characteristics should be matched as closely as possible before the generators are connected together. They may be rotating at different frequencies. This difference in rotation is called “slip frequency”. 1
CHAPTER 2 SCADA SCADA is an acronym for Supervisory Control and Data Acquisition. SCADA systems are used to monitor and control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil and gas refining and transportation. These systems encompass the transfer of data between a SCADA central host computer and a number of Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs), and the central host and the operator terminals. A SCADA system gathers information (such as where a leak on a pipeline has occurred), transfers the information back to a central site, then alerts the home station that a leak has occurred, carrying out necessary analysis and control, such as determining if the leak is critical, and displaying the information in a logical and organized fashion. These systems can be relatively simple, such as one that monitors environmental conditions of a small office building, or very complex, such as a system that monitors all the activity in a nuclear power plant or the activity of a municipal water system. Traditionally, SCADA systems have made use of the Public Switched Network (PSN) for monitoring purposes. Today many systems are monitored using the infrastructure of the corporate Local Area Network (LAN)/Wide Area Network (WAN). Wireless technologies are now being widely deployed for purposes of monitoring.
SCADA systems consist of: • One or more field data interface devices, usually RTUs, or PLCs, which interface to field sensing devices and local control switchboxes and valve actuators. • A communications system used to transfer data between field data interface devices and control units and the computers in the SCADA central host. The system can be radio, telephone, cable, satellite, etc., or any combination of these.
2
• A central host computer server or servers (sometimes called a SCADA Center, master station, or Master Terminal Unit (MTU) • A collection of standard and/or custom software [sometimes called Human Machine Interface (HMI) software or Man Machine Interface (MMI) software] systems used to provide the SCADA central host and operator terminal application, support the communications system, and monitor and control remotely located field data interface devices.
3
CHAPTER 3 PARALLEL OPERATION OF GENERATORS
Generator paralleling is a frequent and essential operation in the power system. In order to connect dual synchronous generators to the system (commonly referred to as paralleling operation), the two generators must first be synchronized by an automatic synchronizer. Severe damage to the generators as well as system disturbances may result if the generators are allowed to be connected to the system outside of established safe levels. There are many methods available for generator’s parameters measuring and synchronization; most of them can be categorized into either hardware based or software based methods. Each method has its own characteristics. With hardware based methods, the generator parameters are measured by a special hardware circuit, while, with software based methods, the parameters are estimated by data acquisition and signal processing, the proposed device in the project is a combination between the hardware and software methods.
3.1 Conditions for parallel operation
There are five conditions that must be met before the synchronization process takes place. The source (generator or sub-network) must have equal line voltage, frequency, phase sequence, phase angle, and waveform to that of the system to which it is being synchronized. Waveform and phase sequence are fixed by the construction of the generator and its connections to the system. During installation of a generator, careful checks are made to ensure the generator terminals and all control wiring are correct so that the order of phases (phase sequence) matches the system.
4
CHAPTER 4 SYNCHRONIZATION Generators are removed or connected from service due to several factors such as variations in load, maintenance and emergency outages. Each time that a generator is connected to a power system, it must be synchronized with it before the interconnecting breaker can be closed.
4.1
Definition Synchronizing, in its simplest form, is the process of electrically connecting and
matching dual generators to each other as shown. To be precise, synchronizing is the act of matching the voltage magnitude, phase angle and frequency of the first generator to the second generator values.
Figure 4.1 Connecting two generators
4.2 Damage in case of asynchronization A properly failure in synchronization can result from electrical and mechanical transients that can damage the generator, prime mover, generator step-up “GSU” transformer, and severely perturbate the power system. We will only focus on the damages that occurred to the system and the generator. 5
4.2.1 System Problems Along with the transient torques to the mechanical system, there will be electrical power oscillations [23]. These oscillations will relatively increase when the generator is synchronizing to a weak system. On the other hand, the generator constitutes a large dynamic source/sink for reactive power. If the generator’s voltage is lower than the system voltage, and the connected system cannot supply the reactive power to hold the voltage up until the generator increase its voltage, the generator’s voltage can cause a voltage dip to the local power system. The situation can actually be worse if the generator regulates its voltage during synchronization. As soon as the generator is synchronized to the system, the generator could immediately back off excitation to try to bring the voltage down to its set point, resulting in an extreme under excited condition. The weak magnetic field can result in the generator not pulling into synchronism or pulling back out of synchronism shortly after synchronization
4.2.2 Generator damage When the generator is connected to the power system, the electrical and mechanical systems are tied together. Prior to closing the generator breaker during synchronizing, the angular velocity of the rotating magnetic field and therefore the frequency of the voltage induced in the stator are governed by the rotor speed. When the breaker is closed the frequency of the power system govern the rotating magnetic field. So the rotor and prime mover will be forced to match their speed and position to be or become identical with the power system. If the speed and position of the rotor are closely matched at the instant the generator is connected to the power system, the transient torque required bringing the rotor and prime mover into synchronism is acceptable.
6
Two situations can have happened if there is mismatch between the generator speed and the power system speed:
First: If the position, as measured by the angular difference between the incoming and running voltages, is close and the angular velocity (frequency) is significantly off, as measured by the slip between the incoming and running voltages, there will be a large transient torque on the mechanical systems to accelerate or decelerate the rotating masses to match the power system angular velocity. Second: If the rotor position is also off (voltage phase angle difference is large), there can be an even higher transient torque required to snap the rotor and prime mover position into phase with the power system. These transient torques can cause instantaneous and/or cumulative fatigue damage to the generator and prime mover over the life of the system Note that the generator standards, and allow ± slip. However, from the mechanical perspective, it is desirable to limit synchronization from zero to positive slip to reduce shock in the mechanical system because of drive-train lash. There can be clearances in the mechanical drive train that cause a small amount of free play between forward and reverse torques. When the prime mover is driving the generator prior to synchronization, the entire drive-train lash is made up in the forward direction. If the generator is running slightly faster than the system, the generator and prime mover will decelerate, and the lash is made up in the correct direction. If the generator is running slower than the system, it will have to accelerate, and the drive-train lash will now have to shift to the opposite direction. Finally, the instantaneous current associated with a severely faulty synchronization can exceed the three-phase bolted fault duty that the generator and transformer must be designed to withstand. Large forces in the generator and transformer windings caused by the current surge can damage the windings and associated blocking, leading to catastrophic failure or reduced life. 7
4.3 Synchronizing methods
Synchronizing methods can be classified into two general categories, manual synchronizing and automatic synchronizing. During a manual synchronizing, the operator has a full control over generator speed and voltage, and after meeting the synchronization conditions, he initiates the breaker closure command. In its simple form, manual synchronizing is completely performed by the operator. This type of synchronizing method is quite simple. However, the main disadvantage of this method is that it requires well trained operators at the controls to prevent costly damage to system components due to improper synchronizing command. In many cases, the loads in the system increase based on random demand and they require immediate connection of the standby emergency generator sets. This demand for immediate attention excludes the use of operating personnel and manual synchronizing, which therefore leads us to automatic synchronizing. With automatic synchronizing, the automatic monitors frequency, voltage and phase angle, provides correction signals for voltage matching and frequency matching, and provides the breaker closing output contact. 4.3.1 Manual Synchronizing Synchronizing equipment has come a long way from the dark lamp synchronizer used in the early days of parallel generator operation.
Figure 4.2 A wiring diagram for the parallel operation of the two alternators 8
This method uses three lamps connected across like phases of the open breaker, and two voltmeters one to measure the first generator voltage, and the other to measure second generator voltage to satisfy the first condition of paralleling as shown. Satisfying other conditions of phase sequence, voltage opposition, and frequency may be determined by the use of the incandescent lamps. The lamp would be at maximum brilliance when the generators were completely out of phase (180 displacements) and completely extinguished when the two voltages were in phase (zero-degree displacement) with identical magnitudes. At any instant, it is seen that the voltage across the lamp is the sum of the individual phase voltages. The procedural steps for putting incoming generator in parallel with the running one are as follows: Step1: The prime mover of the incoming machine starts, and the generator is brought up to near its rated speed. Step2: By adjusting the field current, the terminal voltage of the incoming machine is made the same as that of the running generator. The lamp in the circuit will now flicker at a rate equal to the difference in frequency of the two generators. Correct connection of the phases result on synchronous brightening and blacking of the lamps. If this is not the case, then it means two of the lines are connected wrongly and they need to be interchanged. Step3: Further adjustment of the incoming prime mover is now necessary, until the lamps flicker at a very low rate; the lamps pulsed as the generator voltage rotated with respect to the system voltage at slip frequency. Step4: Final adjustment the operator would initiate a breaker close when the lamps were dark, indicating matching voltages and phase alignment.
The alternative practice is to supervise manual synchronizing with protective functions to prevent out-of-phase closures that would result from operator error. Sophisticated protective
9
functions with settable parameters have become a necessary part of manual synchronizing scheme. A voltage is provided from step-down potential transformers (in high voltage applications) for the input signal to these devices.
Synchronizing meter panels are used to provide
information to operators. The metering devices typically include individual bus and generator frequency meters for matching frequency, individual bus and generator a-c voltmeters for matching voltage, asynchroscope, and two indicator lamps. Synchroscope 2
Sync-check
Circuit breaker PRIME MOVER
GEN
Speed control
Voltage control Sync-check switch
Close Command
OPERATOR
Control switch
Figure 4.3 Manual synchronizing The frequency and phase angle match between the two systems are now determined by observation of a synchroscope, which is shown.
4.4 Synchroscope
The synchroscope is a multiple parameter information source. It indicates if there is a slip rate (a frequency difference between generator and bus), if the generator frequency exceeds the system frequency, the indicator on the scope will rotate in a clockwise direction. If the 10
generator frequency is below that of the power system, rotation will be in the counterclockwise direction.
In a pure manual synchronizing scheme, the operator initiates an unsupervised close command to the breaker from the breaker control switch. This operator-only design has become nearly extinct.
The relay's output contacts are placed in series with the operator's control switch. Closure of the circuit breaker only occurs when 1)
The operator manually attempts to close the circuit breaker, and
2)
The supervisory relay contacts are closed. A functional block diagram of the
supervisory type relay is shown,
Phase Phase AND Comparison Live Bus and Live GEN
Voltage Monitor
Variable Time Delay
Live GEN and Dead Bus
Figure 4.4 Synch-Check block diagram
11
OR
K
The manual system uses two types of sync-check relay: The first one is the electromechanical sync-check relays use the induction disk principle, with two sets of coils acting on the disk. Operating torque proportional to the vector sum of the two input voltages is produced by one set of coils. The other coil set produces restraining torque in proportion to the vector difference of the voltages. The assembly also includes a restraint spring and drag magnet. Electromechanical sync-check relays should not be applied such that both inputs are continuously energized. This will result in vibration that will over time damage the relay. Instead, one relay input should be connected through the contact of the synchronizing switch. The second type is the solid-state and microprocessor technology. This type allowed the development of algorithms to monitor a host of voltage and frequency conditions applicable to safe synchronization. The most important of these is the direct slip calculation afforded by many microprocessor-based relays.
4.5
Automatic Synchronizing For the first 40-year of the power industry, the synchronizing was entrusted to the skill of a
well-trained operator. Such responsibility would not be delegated to an automatic scheme that could malfunction and initiate a disastrous out-of-phase closure. However, as generator size increased and designs became more efficient, both electrical and mechanical systems became less tolerant of the manual synchronization. A less-tolerant design is reflected by the tight limits now placed on closing angle, voltage difference and slip frequency by manufacturers.
Plant complexity also increased significantly, putting more demands on the operating staff and diverting the operator from the act of synchronizing. These changes and the disastrous damage resulting from some operator misjudgements led to the evolution of synchronizing equipment from unrestricted operator-controlled to the fully automated synchronizing schemes that have now become common.
12
The intent is that the automatic system is preferred and the manual system is used only when the automatic system is unavailable. However, in practice, the method actually implemented is dependent on individual plant philosophy and, in some cases, the level of frustration with the automatic synchronizing equipment.
The operator controls the initial startup and early acceleration of the generator. As the generator accelerates, voltage rises. At about of 70% to 80% rated voltage, the automatic synchronizer is capable of measuring generator frequency and takes control of the synchronizing. The auto synchronizer actuates the governor and voltage regulator to meet slip, voltage magnitude and phase angle limits set within the synchronizer. When operating parameters are within the preset limits, the synchronizer issues a close command to the synchronizing breaker. Most electronic synchronizers are of the anticipatory type, when all limits are satisfied, the synchronizer will use real-time slip measurements and the breaker closing time to calculate the close initiation angle necessary to produce a closure at the zerodegree position. At the calculated angle, the synchronizer issues the close command. Anticipatory synchronizers require some minimum system slip to operate. State-of-the art synchronizers can operate with slip as low as 0.0001 Hz. This equates to one synchroscope revolution in 2.8 h.
Speed matching to this accuracy is not normally achieved. Although such a close match is ideal for a smooth synchronization, at this slip breaker closing will be delayed about 5 min for every 10ο the generator voltage must travel to reach the in-phase position. In order to speed up the breaker closing, most preventive synchronizers issue a start pulse to the governor if voltage is within acceptable closure limits but slip is very low. Automatic synchronizers include a variety of settable closing limit parameters to assure safe synchronization. In case of malfunctioned synchronizer, these limits are certainly useless. This is often the same synccheck relay that supervises manual synchronizing. 13
CHAPTER 5 INTERNET OF THINGS 5.1 Internet of Things in Power System Internet of Things (IoT) technology is a new information processing and acquisition method, including radio frequency identification technology, sensor technology, smart technology, nanotechnology and other technologies. It has been considered as the third wave of the information industry after computer, Internet and mobile communication network. Now it has been widely used in intelligent transportation, industrial monitoring, environmental monitoring, defence and military, digital family and other fields. For electrical power system, smart grid is the latest trend of development and reform in today’s world, and it is also a major technological innovation and development trend in the 21st century. The implementation of smart grid must rely on the line monitoring and real-time control in all aspects of the grid important operating parameters, and the basic characteristics are grid information, automation and communication. Meanwhile, Internet of Things technology also has many characteristics, such as comprehensive perception, reliable transmission and intelligent processing, so they two have good space to fusion.
At present, the application research of Internet of Things technology in smart grid has been a hot research topic in the global field. In June 2009, the United States announced a smart grid standards and interoperability principles called "ieeep2030", it would largely promote the applications of Internet of Things technology in smart grid. Under the U-Japan strategic conception, Japan further proposed the I-Japan to vigorously develop the Internet of things and built smart grid. In 2010, the World Expo successfully held in Shanghai. Through a variety of simulation, it made people experience the smart and convenient which are after the perfect combination of Internet of Things technology and smart grid.
14
Therefore, If China want to build a strong and smart grid, which treats UHV power grid as the backbone with the coordinated development at all the levels of power, the research about applications of IoT technology in smart grid is imperative.
5.2 Internet of Things Energy
Internet of Things (IOT) is an emerging concept which promises universal connectivity of all devices and processes necessary to give users holistic intelligent interaction in their daily lives and creating a better and more efficient life experiences. As applied to the Energy production, delivery and consumption Internet of Things Energy (IoT-E) holds great promise in revolutionizing the Power Grid and consumer interactions resulting in economic efficiencies, positive environmental impacts and improvements in reliability.It is a complete integration of all power systems and power grid apparatus, entire utility supply chain, production, transport and delivery processes, consumers and consumers' energyusing gadgets and appliances and any and all systems which contribute to production of the electron to the consumption of the electron. Currently many disjointed processes and systems are used to manage this life cycle of production to consumption with many inefficiencies and gaps which impact all involved.
A non-efficient process has eminent impacts on the utility company bottom line, reliability of service, cost to consumers and most importantly the impact to the environment. In the not too distant future, millions of intelligent controllers, sensors and applications will be used to monitor, control, schedule, dispatch and optimize the flow of energy in a centralized and decentralized manner, taking into account not macro decision parameters, but micro decision parameters down to a single individual consumer's real-time and forecasted actions.
15
5.3 The Concept of Smart Grid and Internet of Things Smart grid is a new and modern power grid, which is highly integrated with advanced sensor measurement technology, information and communication technology, analysis of the decision-making technology, automatic control technology, and energy power technology and grid infrastructures. Compared with the traditional grid, smart grid has been improved distinctly in the optimization of power control, the flexibility of grid structure, optimizing the allocation of resources, and improving the power quality of services. Therefore, smart grid has many characteristics including strong, self-healing, compatibility, economy, integration and optimization and so forth. Internet of Things, namely “the Internet in which the things connected to each other”, is the extension and expansion of Internet-based network. According to the agreed protocols, with IoT key technologies: radio frequency identification technology, sensor technology, smart technology and nanotechnology, the communication information can be exchanged, and the intelligent recognition, positioning, tracking, monitoring and management can be achieved.
5.4 Power Monitoring
Power monitoring is mainly based on the distribution network of IoT technology and electricity comprehensive data-aware management system. The system which consists of power monitor, front and computer, multi network fusion terminal, electric control center and any other things, can achieve the remote monitoring about electricity consumption of electrical equipment’s in the factories, enterprises and institutions and families, meanwhile can give starting and stopping control instruction to the remote equipment’s.
16
By monitoring electricity equipment’s connected to grid, power monitor sends data, such as its load conditions, power consumption and other information, to a specific front end computer through the network concentrator and wireless communication. As the control center of power data acquisition, transmission and power equipment, front end computer sends the pre-processed data to the data communication network from multi network fusion terminal, and finally uploads to electric control center of the son station layer. Electric control center builds management information systems, analyzes and processes electricity data, and opens data interface, so that it can remote inquire the electrical equipment’s’ operation, power consumption and so on, so as to realize the remote control.
Figure 5.1 Applications of Internet of Things in Smart Grid
17
CHAPTER 6 TRANSACTIVE ENERGY GRID SYSTEMS 6.1 Introduction The GridWise Architecture Council’s Framework defines TE as follows: “A set of economic and control mechanisms that allows the dynamic balance of supply and demand across the entire electrical infrastructure using value as a key operational parameter.”
Another source, 5th edition of the Smart Grid Dictionary, provides the following definition: “A software-defined grid managed via market-based incentives to ensure grid reliability and resiliency. This is done with software applications that use economic signals and operational information to coordinate and manage devices’ production and/or consumption of electricity in the grid. Transactive energy describes the convergence of technologies, policies, and financial drivers in an active prosumer [Rickerson et. al. (2014) define prosumers as consumers who also produce their own power from a range of different onsite generators (e.g. diesel generators, combined heat-and-power systems, wind turbines, and solar photovoltaic (PV) systems] market where prosumers are buildings, EVs, micro grids, VPPs or other assets.”
Accordingly, TE is a vision of an intelligent device-enabled-grid where each device can utilize economic signals in order to optimize allocation of resources subject to the constraints of the grid. It can be applied within a localized area, e.g., microgrid, or be utilized to manage the whole power system. One example of an application of a transactive energy technique is the double auction market used to control responsive demand side assets in the GridWise Olympic Peninsula Project.
18
Taking it one step further, some TE visionaries simplify the picture even further by operationalizing it through the use of a market exchange platform, where all parties are networked through it. This operationalization reflects four ideas of the TE world: 1. There are two products: energy and transport services; 2. Forward transactions are used to manage risk and coordinate investment decisions; 3. Spot transactions are used to coordinate operating decisions; and, 4. All parties act autonomously
6.2 Working of Transactive Energy
It is often argued that the TE model is not new and has been successfully implemented in other areas such as wholesale electricity markets and events, e.g., baseball, ticket purchases. The main idea of a TE construct is to integrate retail and wholesale markets and market signals into a single platform by utilizing forward and spot transactions, thereby guiding investment and operating decisions.
In a TE construct, there will be three groups of players: Energy services (customers, producers, prosumers, storage, owners), transport services (transmission and distribution owners), and intermediaries (exchanges, market makers, system operators), as opposed to the traditional categorization of customer types: residential, commercial, and industrial. In this TE vision, all parties will have sophisticated energy management systems and/or third party assistance that will help them optimize their energy use and production based on value and grid constraints. If they do not want to participate in market exchanges, they can acquire fixed-price subscriptions on a forward-looking basis
19
Figure 6.1 Working Model of Transactive Grid. 6.3 Attributes of Transactive Energy Architecture
All transactive energy tools and methodologies are described as constituents or subsystems of system architecture.
Extent
An implementation of transactive energy technology will typically apply within some geographic, organizational, political, or other measure of extent.
Transacting
TE involves transacting parties, mostly automated systems.
Parties Temporal
Transactive elements interact across multiple time scales, ranging
Variability
from sub-second to five minutes or to some longer periodicity.
Interoperability Transactions are enabled through the exchange of information between transacting parties. There are two elements to consider here:
technical
interoperability
and
cognitive
(semantic)
interoperability. The systems must be able to connect and exchange information (emphasizing format and syntax). 20
Value
A value discovery mechanism is a means of establishing the
Discovery
economic or engineering value (such as profit or performance) that
Mechanism
is associated with a transaction.
Assignment of
For sub-elements of a transactive energy mechanism, a means may
Value
be needed for assigning value to those objectives that cannot be addressed through a discovery mechanism or for values that do not have a common dimension that can be used for valuation.
Assuring
The stability of grid control and economic mechanisms is required
Stability
and must be assured. Considerations of control system stability must be included in the formulation of transactive energy techniques and should be demonstrable.
Transaction
The transaction is the central mechanism by which transactive energy systems achieve their objectives; by linking multiple individual operations into a single, indivisible transaction, which optimizes the objectives and ensures that all operations in the transaction are completed without error.
Table 6.1 Attributes of Transactive Energy
6.4 Differentiation of Transactive Energy from Smart Grid
It is pretty straightforward to see the differences between a traditional grid and a smart grid. For example, a brief comparison between existing grid and smart grid can be made as follows
21
Existing Grid
Smart Grid
Electromechanical
Digital
One-way
Two-way
communication
communication
Centralized
Distributed
generation
generation
Few sensors
Sensors throughout
Manual
Self-
monitoring
monitoring
Manual
Self-healing
restoration Failures and
Adaptive and
blackouts
islanding
Limited control
Pervasive control
Few customer
Many
choices
customer choices
Table 6.2 Comparison between existing grid and smart grid
22
Even though some define SG as transactive in itself, there are additional characteristics that make SG transactive: 1. Allowing for the faster transmission of information, including prices, across the grid, through communication component of the smart grid; 2. Empowering consumers by enabling consumers’ active participation; 3. Accommodating all new generation devices needed for a functional decentralized supply model; and, 4. Accommodating two-way power flows. 6.5 Need for transactive energy TE advocates typically cite the changing nature of the power grid, increasing penetration of distributed resources, variability of power generation, and penetration of intelligent devices as factors that create new challenges and opportunities for the existing grid. As a customer-oriented solution, TE is perceived as a tool that responds to the need to manage such a complex system. It is indisputable that the nature of the power grid is ever-changing. Even though we are not facing imminent blackouts due to the factors contributing to this change, the expected increasing complexity of the grid, furtherance of environmental goals which implies deeper penetration of renewable resources, EVs, etc., is motivating stakeholders to be more proactive and to create solutions to potential problems. For example, due to variability and unpredictability of some renewable resources, greater flexibility and more reliable customer resources are being sought. Due to the nature and the amount of new demands on the grid, it is argued that it is almost impossible for utilities and independent system operators (ISOs) to manage the increasingly complex system as it is operated and constructed today, as these new systems are mostly controlled by consumers and can be challenging to monitor and manage in real time. 23
It is expected that “with the right design in place, distributed systems, organized in a hierarchy of control layers but all sharing commonly understood sets of data, could create what the framework describes as ‘a loosely coupled set of controls with just enough information exchange to allow for stability and global optimization through local action.’ That is with the right design of engineering and economics, a transactive energy network aims to create a perfect market where fully informed actors will make fully rational decisions, benefitting themselves as well as the grid. The table illustrates how TE can accommodate more flexibility and reliability by allowing exchanges up to the real time, as opposed to traditional demand response resources.
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CHAPTER 7 DEMAND RESPONSE 7.1 Demand Response
Demand Response (DR) is voluntary load curtailments by large Commercial and industrial consumers during peak hours when requested by Utility in order to create a curtail able capacity during high demand months. It is a primary demand side resource for smart grid solution. It Creates opportunity to use demand side assets. Financial incentives are offered to consumers participating in load curtailment when demanded. As consumers, we don’t always pay close attention to when we use energy. Demand for electricity continues to rise. We all tempt to use it at the same time and in similar ways. Demand response programs are designed to elicit changes in customers’ electric usage patterns. Some types of demand response, implemented through approved utility tariffs or through contractual arrangements in deregulated markets, vary the price of electricity over time to motivate customers to change their consumption patterns; this approach is termed price based demand response. Other demand response programs reward customers for reducing their electric loads upon request or for giving the program administrator some level of control over the customer’s electricity-using equipment. These are termed incentive- or event-based demand response. Demand response programs are being used by electric system planners and operators as resource options for balancing supply and demand. Such programs can lower the cost of electricity in wholesale markets, and in turn, lead to lower retail rates. Methods of engaging customers in demand response efforts include offering time-based rates such as time-of-use pricing, critical peak pricing, variable peak pricing, real time pricing, and critical peak rebates. It also includes direct load control programs which provide the ability for power companies to cycle air conditioners and water heaters on and off during periods of peak demand in exchange for a financial incentive and lower electric bills. 25
The electric power industry considers demand response programs as an increasingly valuable resource option whose capabilities and potential impacts are expanded by grid modernization efforts. For example, sensors can perceive peak load problems and utilize automatic switching to divert or reduce power in strategic places, removing the chance of overload and the resulting power failure. Advanced metering infrastructure expands the range of time-based rate programs that can be offered to consumers and smart customer systems such as in-home displays or home-area-networks can make it easier for consumers to changes their behaviour and reduce peak period consumption from information on their power consumption and costs. These programs also have the potential to help electricity providers save money through reductions in peak demand and the ability to defer construction of new power plants and power delivery systems specifically, those reserved for use during peak times.
7.2 Types of Demand Response Demand response can be classified according to how load changes are brought about. Price-based demand response refers to changes in usage by customers in response to changes in the prices they pay and include real-time pricing, critical-peak pricing, and timeof-use rates. If the price differentials between hours or time periods are significant, customers can respond to the price structure with significant changes in energy use, reducing their electricity bills if they adjust the timing of their electricity usage to take advantage of lower-priced periods and/or avoid consuming when prices are higher. Customers’ load use modifications are entirely voluntary.
Incentive-based demand response programs are established by utilities, load serving entities, or a regional grid operator. These programs give customers load reduction incentives that are separate from, or additional to, their retail electricity rate, which may be fixed (based on average costs) or time-varying. The load reductions are needed and 26
requested either when the grid operator thinks reliability conditions are compromised or when prices are too high. Most demand response programs specify a method for establishing customers’ baseline energy consumption level, so observers can measure and verify the magnitude of their load response. Some demand response programs penalize customers that enroll but fail to respond or fulfill their contractual commitments when events are declared.
7.2 Tariff Options (price-based demand response) Time-of-use (TOU): a rate with different unit prices for usage during different blocks of time, usually defined for a 24-hour day. TOU rates reflect the average cost of generating and delivering power during those time periods. TOU rates often vary by time of day (e.g., peak vs. off peak period), and by season and are typically pre-determined for a period of several months or years. Time-of use rates are in widespread use for large commercial and industrial (C/I) customers and require meters that register cumulative usage during the different time blocks. Real-time pricing (RTP): a rate in which the price for electricity typically fluctuates hourly reflecting changes in the wholesale price of electricity. RTP prices are typically known to customers on a day-ahead or hour-ahead basis. Critical Peak Pricing (CPP): CPP rates include a pre-specified high rate for usage designated by the utility to be a critical peak period. CPP events may be triggered by system contingencies or high prices faced by the utility in procuring power in the wholesale market, depending on the program design. CPP rates may be super-imposed on either a TOU or time-invariant rate and are called on relatively short notice for a limited number of days and/or hours per year. CPP customers typically receive a price discount during nonCPP periods. CPP rates are not yet common, but have been tested in pilots for large and small customers in several states. 27
7.3 Program Options (“incentive-based” demand response) Direct load control: a program in which the utility or system operator remotely shuts down or cycles a customer’s electrical equipment (e.g. air conditioner, water heater) on short notice to address system or local reliability contingencies. Customers often receive a participation payment, usually in the form of an electricity bill credit. A few programs provide customers with the option to override or opt-out of the control action. However, these actions almost always reduce customer incentive payments. Direct load control programs are primarily offered to residential and small commercial customers. Interruptible/curtailable (I/C) service: programs integrated with the customer tariff that provide a rate discount or bill credit for agreeing to reduce load, typically to a pre-specified firm service level (FSL), during system contingencies. Customers that do not reduce load typically pay penalties in the form of very high electricity prices that come into effect during contingency events or may be removed from the program. Interruptible programs have traditionally been offered only to the largest industrial (or commercial) customers. Demand Bidding/Buyback Programs: programs that (1) encourage large customers to bid into a wholesale electricity market and offer to provide load reductions at a price at which they are willing to be curtailed, or (2) encourage customers to identify how much load they would be willing to curtail at a utility-posted price. Customers whose load reduction offers are accepted must either reduce load as contracted (or face a penalty). Emergency Demand Response Programs: programs that provide incentive payments to customers for measured load reductions during reliability-triggered events; emergency demand response programs may or may not levy penalties when enrolled customers do not respond. 28
7.5 The Role of Demand Response in Electric Power Systems In assessing the benefits of demand response, it is important for policymakers to be cognizant of the physical infrastructure and operational requirements necessary to construct and reliably operate an electric power system as well as regional differences in market structure and industry organization.
In all market structures, the management of electric power systems is largely shaped by two important physical properties of electricity production. First, electricity is not economically storable, and this in turn requires maintaining the supply/demand balance at the system level in real time. Mismatches in supply and demand can threaten the integrity of the electrical grid over extremely large areas within seconds. Second, the electric power industry is very capital intensive. Generation and transmission system investments are large, complex projects with expected economic lifetimes of several decades that often take many years to develop, site and construct. These features of electric power systems necessitate management of electricity on a range of timescales, from years (or even decades) for generation and transmission planning and construction, to seconds for balancing power delivery against fluctuations in demand.
Demand response options can be deployed at all timescales of electricity system management and can be coordinated with the pricing and commitment mechanisms appropriate for the timescale of their commitment or dispatch. For example, demand response programs designed to alert customers of load response opportunities on a day ahead basis should be coordinated with either a day-ahead market or, in a vertically integrated market structure, with the utility’s generator scheduling process. Like generation resources, the actual delivery of customer load reductions occurs in real time.
29
Energy efficiency is a demand-side resource that can be integrated and valued as part of the system planning process and time horizon. Though not dispatchable, energy-efficiency measures often create permanent demand-reduction impacts as well as electricity savings.
If utility resource planners and system operators have a good sense of how their customers respond to changes in the price of electricity, price-based demand response options may be incorporated into system planning at different time scales. TOU rates, which reflect diurnal and seasonal variations in electricity costs but are fixed months in advance, may be valued and integrated as part of operations planning.
RTP provides hourly prices to customers with day-ahead or near-real-time notice, depending on the tariff design.23 In wholesale markets with ISOs/RTOs, RTP prices are typically indexed to transparent, location-based, day-ahead or real-time hourly energy market prices; absent an organized spot market, utilities establish RTP “prices” based on the utility’s marginal procurement costs.
CPP rates are essentially TOU rates with the addition of a critical peak price that is called on a day-of basis. Incentive-based demand response programs may be introduced at virtually all timescales of electric system management.
Capacity programs involve load reduction commitments made ahead of time (e.g., months), which the system operator has the option to call when needed. The call option is usually exercised with two or less hours of notice, depending on the specific program design. Participants receive up-front capacity payments, linked to capacity market prices, from entities that otherwise would need to purchase comparable levels of generation to satisfy capacity reserve obligations. Ancillary services programs also involve establishing customer load commitments ahead of time. Customers whose reserve market bids are accepted must then be “on call” to provide load reductions, often with less than an hour’s notice. 30
Load reductions from demand buyback or bidding programs are typically scheduled dayahead, and incentive payments are valued and coordinated with day-ahead energy markets.
Emergency programs are reliability-based, and payments for load reductions are often linked to real-time energy market prices (in regions with organized wholesale markets) or values that reflect customer’s outage cost or the value of lost load. Program events are usually declared within 30 minutes to 2 hours of power delivery.
7.6 Benefits of Demand Response
The benefits of demand response can be classified into three functional categories: direct, collateral and other benefits. Direct benefits accrue to consumers that undertake demand response actions, and collateral and other benefits are enjoyed by some or all groups of electricity consumers. Direct and collateral benefits can be quantified in monetary terms. Other benefits are more difficult to quantify and monetize.
Participant Benefits: Customers who adjust their electricity usage in response to prices or demand response program incentives do so primarily to realize financial benefits. In addition, they may be motivated by implicit reliability benefits Financial benefits include cost savings on customers’ electric bills from using less energy when prices are high, or from shifting usage to lower-priced hours, as well as any explicit financial payments the customer receives for agreeing to or actually curtailing usage in a demand response program.
Reliability benefits refer to the reduced risk of losing service in a blackout. This benefit may be associated with an internalized benefit, in cases where the customer perceives (and monetized) benefits from the reduced likelihood of being involuntarily curtailed and 31
incurring even higher costs, or societal, in which the customer derives satisfaction from helping to avoid widespread contingencies. Both are difficult to quantify but may nonetheless be important motivations for some customers. The level of direct benefits received by participating customers depends on their ability to shift or curtail load and the incentives afforded by time-varying electricity prices and any additional program incentives that are offered.
Collateral Benefits: Demand response, through its impacts on supply costs and system reliability, produces collateral benefits that are realized by most or all consumers. It is these collateral benefits, which have system-wide impacts, that provide the primary motivation for policymakers’ interest in demand response. Collateral benefits can be categorized functionally as short-term and long-term market impacts as well as reliability benefits: Short-term market impacts are the most immediate and easily measured source of financial benefits from demand response. Broadly speaking, they are savings in variable supply costs brought about by more efficient use of the electricity system, given available infrastructure. More efficient resource use, enabled by building better linkages between retail rates and marginal supply costs, translates to short term bill savings to consumers from avoided energy and, in some cases, capacity costs. Where customers are served by vertically integrated utilities, short-term benefits are limited to avoided variable supply costs. In areas with organized spot markets, demand response also reduces wholesale market prices for all energy traded in the applicable market. Reductions in usage during high-priced peak periods result in a lower wholesale spot market clearing price. The amount of savings from lowered wholesale market prices depends on the amount of energy traded in spot markets, rather than being committed in forward contracts.
32
Long-term market impacts hinge on the ability of demand response to reduce system or local peak demand, thereby displacing the need to build additional generation, transmission or distribution capacity infrastructure. Because the electricity sector is extremely capitalintensive, avoided capacity investments can be a significant source of savings. However, for demand response resources to reduce capacity costs, it must be available and perform reliably at high-demand periods throughout the year because it is displacing other capacity resources. Reliability benefits refer to reducing the probability and severity of forced outages when system reserves fall below desired levels. By reducing electricity demand at critical times (e.g., when a generator or a transmission line unexpectedly fails), demand response that is dispatched by the system operator on short notice can help return electric system (or localized) reserves to precontingency levels.
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CHAPTER 8 CIRCUIT DIAGRAM 8.1 Overall Block Diagram
Figure 8.1
34
Block Diagram
8.2 Overall Circuit Layout of the Proposed System
Figure 8.2 Overall Circuit Layout of the Proposed System
35
8.3 ARDUINO UNO
Figure 8.3 Arduino and pin diagram The Arduino Uno is a microcontroller board based on the ATmega328P. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz quartz crystal, a USB connection, a power jack, an ICSP header and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. "Uno" means one in Italian and was chosen to mark the release of Arduino Software (IDE) 1.0. The Uno board and version 1.0 of Arduino Software (IDE) were the reference versions of Arduino, now evolved to newer releases. The Uno board is the first in a series of USB Arduino boards, and the reference model for the Arduino platform; for an extensive list of current, past or outdated boards see the Arduino index of boards. The ATmega328 on the Uno comes preprogrammed with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the original STK500 protocol. The ATmega328 has 32 KB (with 0.5 KB occupied by the bootloader). It also has 2 KB of SRAM and 1 KB of EEPROM. 36
The Uno has a number of facilities for communicating with a computer, another Uno board, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The 16U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. The Arduino Software (IDE) includes a serial monitor which allows simple textual data to be sent to and from the board. The RX and TX LEDs on the board will flash when data is being transmitted via the USB-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).
8.4 RASPBERRY PI 2 - MODEL B The Raspberry Pi is a series of credit card–sized single-board computers developed in England, United Kingdom by the Raspberry Pi Foundation with the intent to promote the teaching of basic computer science in schools and developing countries. The original Raspberry Pi and Raspberry Pi 2 are manufactured in several board configurations through licensed
manufacturing
agreements
with Newark
element14 (Premier
Farrell), RS
Components and Egoman. The hardware is the same across all manufacturers. Several generation of Raspberry Pi's have been released. The first generation (Pi 1) was released in February 2012 in basic model A and a higher specification model B. A+ and B+ models were released a year later. Raspberry Pi 2 model B was released in February 2015 and Raspberry Pi 3 model B in February 2016. The boards are priced between US$20 and US$35. A cut down compute model was released in April 2014 and a Pi Zero with smaller footprint and limited IO capabilities released in November 2015 for US$5. All models feature a Broadcom system on a chip (SOC) which include an ARM compatible CPU and an on chip graphics processing unit GPU (a Video Core IV). CPU speed range from 700 MHz to 1.2 GHz for the Pi 3 and on board memory range from 256MB to 1GB RAMS. Secure Digital SD cards are used to store 37
the operating system and program memory in either the SDHC or Micro SDHC sizes. Most boards have between 1 and 4 USB slots, HDMI and composite video output, and a 3.5mm jack for audio. Lower level output is provided by a number of GPIO pins which support common protocols like I2C. Some models have an RJ45 Ethernet port and the Pi 3 has on board WIFI 802.11n and Bluetooth. The Foundation provides Debian and Arch Linux ARM distributions for download, and promotes Python as the main programming language, with support for BBC BASIC (via the RISC OS image or the Brandy Basic clone for Linux), C, C++, Java, Perl, Ruby, Squeak Smalltalk and more also available.
Figure 8.4 Location of connectors and ICS on Raspberry Pi 2 Model B. SPECIFICATIONS
A 900MHz quad-core ARM Cortex-A7 CPU. 1GB RAM. 4 USB ports. 40 GPIO pins. Full HDMI port. Ethernet port. Combined 3.5mm audio jack and composite video. Camera interface (CSI). Display interface (DSI). Micro SD card slot. Video Core IV 3D graphics core. MODEL 2 B+. 38
8.5 Development of Voltage Sensor Using Voltage Divider Circuit
Figure 8.5 Voltage Sensor using Voltage Divider Circuit
A basic voltage divider circuit is used as the AC/DC Sensing Unit to scale down the input DC and AC voltages into a DC voltage in the range of 0 to 5 V. The Processor Unit can read this scaled down voltage and calculate the actual AC/DC voltages. When we are applying an AC voltage we use a rectifier diode in series with the Voltage divider circuit to prevent the negative cycles from entering the circuitry. No need for step down transformers because we are already getting a voltage ‘V2’ in the range of 0 to 5 V only, across R2.
39
8.6 Development of Auto Synchronizer
Figure 8.6 Development of Auto Synchronizer using Arduino Uno
The Auto synchronizer consists of voltage divider circuits used to measure the line voltages of the generator (which needs to be synchronized) and the bus to which it’s been connected. The measured output voltage waveforms are given as analog inputs to the Arduino Microcontroller. The Arduino Uno has an inbuilt ADC converter which is used to match the sinusoidal waveforms of the two voltage readings from voltage divider circuit. Once the values are set and the reference values are mapped, the circuit functions as an automatic synchroscope where the output pulse is given to the relay circuit to close the breaker upon synchronization.
40
8.7 PROXIMITY SENSOR
Figure 8.7 Inductive Type Proximity Sensor Inductive proximity sensors are used for non-contact detection of metallic objects. Their operating principle is based on a coil and oscillator that creates an electromagnetic field in the close surroundings of the sensing surface. The presence of a metallic object (actuator) in the operating area causes a dampening of the oscillation amplitude. The rise or fall of such oscillation is identified by a threshold circuit that changes the output of the sensor. The operating distance of the sensor depends on the actuator's shape and size and is strictly linked to the nature of the material. These sensors contain an output amplifier with the function N.O. or N.C. that can pilot a load connected in series. PNP Output: Transistor output that switches the positive voltage to the load. The load is connected between output and common. Current flows from the device's output, through the load to ground when the switch output is on. Also known as current sourcing or positive switching. NPN Output: Transistor output that switches the common or negative voltage to the load. The load is connected between the positive supply and the output. Current flows from the load through the output to ground when the switch output is on. Also known as current sinking or negative switching.
41
8.8 CURRENT SENSOR
Figure 8.8 Current Sensor ACS712 provides economical and precise solutions for AC or DC current sensing. The device consists of a precise, low-offset, linear Hall sensor circuit with a copper conduction path located near the surface of the die. The device consists of a precise, low-offset, linear Hall circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field which the Hall IC converts into a proportional voltage. Device accuracy is optimized through the close proximity of the magnetic signal to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC, which is programmed for accuracy after packaging. The output of the device has a positive slope (>VIOUT(Q)) when an increasing current flows through the primary copper conduction path (from pins 1 and 2, to pins 3 and 4), which is the path used for current sampling. The internal resistance of this conductive path is 1.2 mΩ typical, providing low power loss. This allows the ACS712 to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques.
42
CHAPTER 9 WORKING OF AN INDIVIDUAL GENERATOR 9.1 Stepper Motor Control Initial conditions for starting the DC motor coupled Alternator requires a starting resistance for the DC motor armature. This is automated using a stepper motor controlled linear movement for the variable arm of the rheostat. The field control of the DC motor and Alternator requires individual set of rheostats for controlling the excitation systems. Similar stepper motor controlled linear movement is employed for the operation of the variable arm of the rheostats.
Figure 9.1 Rheostat arrangement for automatic variable control
The stepper motor control driver is engaged using L293D integrated circuit motor driver for sending the control pulses of the stepper motor field coils. A set of three driver boards are used to drive the stepper motors individually. The total current carried for the stepper motor driver circuit is around 1.2 A and is supplied by a separate power source. 43
9.2 Relay Circuitry In order to open and close the DC source to the DC motor and field of the generator, a relay switch acting as a circuit breaker is employed. The relay also acts as a circuit breaker for the incoming generator or opening of the existing generator from the bus. Apart from isolating the DC source and connecting the generators to the bus, it is also used to control the load being connected to the bus. Control of the load (load shedding) provides an additional feature of protecting the system from over-loads during peak hours. The relay circuit gets its command pulses from the Raspberry Pi controller for controlling all the relays according to the system parameters.
9.3
Voltage and Current Sensor
The voltage sensor is used to measure the bus voltage and generator side voltages. Both line or phase voltage can be measured using the proposed system. According to the measured values the synchroscope detects the peak values for the waveforms and closes the relay which brings the generator into the grid.
To measure the load on the bus and amount of field current supplied to the DC motor and alternator, ACS712 current sensors are used to control the system. The value of the field current is used to vary the position of the variable rheostat. Generator field current is also monitored in order to operate the machine within their rated capacity.
Series of signal outputs obtained from the sensors is sent to the Arduino board, which is assigned to each generator individually. The signals are then processed and fed back to the Raspberry Pi board for further control of the excitation system. This forms a closed feedback loop system to control the entire generation unit. 44
Once the DC source is connected by the relay circuit, the starting resistance of the DC motor is brought to minimum position. The DC motor picks up speed and attains a certain RPM. This is measured by the inductive type proximity sensor. Speed values are constantly updated in the Arduino board connected to each generator. Field current of the DC motor is slowly increased to achieve the rated speed. Once the generator attains its rated speed, the rheostat of the DC motor field current stops increasing. Then the generator field current begins ramping up, until the generator generates the rated voltage and the stepper motor of the generator field ceases.
When a load is connected to the system, there is a considerable drop in the voltage of the generator and speed. To satisfy the load the field current rheostats regulates itself through the control pulses sent by the Raspberry Pi.
For a new incoming load
The existing generator acts as the bus to the load. When a new load is incoming to the bus, there is again a drop in the voltage and speed of the generator. Since the new incoming load is greater than the rated capacity of the first generator, the second generator is brought into the grid. This involves synchronization of the incoming generator with the bus. Now the second generator voltage and frequency is measured and compared with the bus voltage and frequency. When both are in phase and equal the relay circuit is closed by the Raspberry Pi and the new load is supplied by both the generators.
So, the stability of the system is constantly monitored and controlled by the proposed system in real time. The data obtained is stored in a database which is interfaced to an overall supervisory control for real time monitoring and control. Thus, the proposed system has an advantage of minimizing the manual labour required for operating several generators in parallel.
45
CHAPTER 10 MATLAB SIMULATION 10.1 Matlab Simulation using SimPowerSystem
Figure 10.1 Physical Modelling using SimPowerSystems 46
10.2 Simulation Output Results
Figure 10.2 Simulation output ( scope values )
47
10.3 Matlab SimPowerSystems
In Matlab SimPowerSystems, the proposed model was simulated using the actual workings conditions of the machines. Considerable results were obtained in the output waveforms of the two generators under parallel operating conditions. The physical modelling of Simscape assisted the work in determining the mechanical parameters such as torque variation and coupling coefficient’s of the two machines.
The mechanical part or prime mover is modelled using the DC motor and generator coupling and supplied as input mechanical power to the synchronous generators. Various output parameters are measured and supplied as feedback to the excitation system of the DC motor. The line voltages, phase voltages and current on the bus bar of the system are measured and a voltage controlled switch is closed or opened according to the drop.
The loading of the system was done dynamically using a conventional RLC loading where a breaker is controlled via a digital pulse for certain time. The output results of the system reflected the drop and increase in load currents for dynamic off and on respectively for the given time period.
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CHAPTER 11 CONCLUSION
Synchronization offers many advantages like reliability, expandability, flexibility. To do that the volt and frequency and phase differences between the generators must be taken into account, where the voltage, frequency and phase differences must be within acceptable parameters. Faulty synchronizing can damage the electrical and mechanical generating systems, causes disturbances to the power system and causes the unit to trip offline. There are two main methods to synchronize generators: automatic and manual. The manual one depends on a well-trained operator where the automatic depends on a device based on hardware or software technique.
The synchronizing process needs fast real time data communication so after along research the Internet of Things (IoT) protocol is chosen which is the main contribution of the proposed work.
Synchronizing device proposed in the project is an Automatic device based on Internet of things protocol. It includes three control units to read the characteristics of two generators and adjusting the generators to become identical with each other.
The three control units are built from Arduino Uno or Atmega 328 microcontrollers connected via a Raspberry Pi board, which are called the generator control unit and main controller unit respectively. They are accounted for the two generators to read the characteristics of the generators, and regulate the phase difference relative to a reference signal, and send OK signal to the third unit via local area network. The third unit is the synchronizer control unit, which waits for the OK signal from the generator voltage control units to issue an order for closing the relay circuit. 49
CHAPTER 12 FUTURE WORK
The proposed synchronize device developed in this project requires to add volt control and frequency control to its controller which give the device ability to adjust the volt and frequency within the acceptable limits of the synchronizing process to get full control to the generator. The most important thing is to generalize the device to synchronize bigger generators of higher ratings and exclude the use of the conventional rheostats.
Secondly, the proposed system disregards the dynamic pricing on the consumers. The basic framework of the Transactive Energy Systems involves the dynamic pricing for the consumers based on peak hours. Maximum efficiency with minimum cost and maintenance along with grid stability enhances the application of the proposed system to opt for dynamic pricing.
50
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