Intelligent Energy Management System Mayur D. Karathia
Jignesh G. Bhatt
PG Scholar Assistant Professor (Sr. Grade) Instrumentation and Control Engineering Department, Faculty of Technology, Dharmsinh Desai University, Nadiad, Gujarat, INDIA
[email protected] [email protected] Abstract—Saving electricity in industries and building is major concern today. Hence, Energy Management System remained preferred area for researchers recently. EMS not only saves electricity, but also monitors and records the electrical consumption data. It also helps diagnose electric machine health, energyefficiency and their reliability against failures. The paper reports the work carried out at PG dissertation level and presents the detailed design and implementation of industrial grade EMS. Sensors and MODBUS-compliant modules are wired to form an RS485 network at field level, which is connected to a PC based main controller. The proposed system online monitors and records the data of energy consumption, and helps to enhance energy efficiency of the system. Offline data based diagnosis helps to plan preventive actions to save electricity and further optimize overall system. Remote access is also availed through intranet/internet. Various functionalities of the proposed system have been validated through laboratory implementation.
Himanshu G. Bhavsar Director Vbtech Automation, Ahmedabad, Gujarat, INDIA.
[email protected]
A. Measurement subsystem This subsystem handles routine tasks related to measurand data such as measurement, display, logging, updating and availing of data as and when necessary. These operations include acquiring energy data from remote energy meters and displaying the same data using Graphical User Interfaces (GUIs) in various customized formats such as Meter view, Gauge view, Trends, etc. Additionally, this also includes recording energy data in the database for later analysis purpose at user specified logging rate. Generally, logging rates are kept adjustable from 10 seconds to few minutes as per conditions and requirements of installation. B. Communication Subsystem This subsystem handles communication between the control-room mounted computers workstations running GUIs and field mounted energy meters. This subsystem also handles remote updation of configuration of energy meters and their firmware. This includes setting device identification number into each energy meter, setting communication parameter, data type (integer, float, and long), etc.
Index Terms—Automation, Human–Machine Interface Design, MODBUS, RS-485, Virtual Instrumentation
I. INTRODUCTION
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nergy management system is a data logging system that incorporates various functionalities that helps in optimization of electricity usage. EMS consists of an intelligently wired network of energy meters, geographically installed in distributed manner to monitor electrical parameters of the load. The typical EMS not only monitors, but also records and manages the data availed by energy meters for analysis purpose. Industries account for huge quantity of the total electrical energy consumption and hence, optimization of energy usage in industries results in significant energy savings. EMS serves three essential functions mentioned below:
C. Analysis Subsystem This includes retrieving energy data stored in the database and displaying them in a proper manner, so that data interpretation becomes easy and quick decisions can be implemented in order to optimize the energy usage. Various types of views and reports of energy consumption on hourly, daily, weekly, monthly and yearly formats can be produced and analyzed further using this subsystem. This paper presents design of an intelligent EMS based on wired network operating on RS-485/MODBUS[1][2] protocols suitable to residential, commercial and industrial environments. MODBUS protocol is used for data acquisition. Although not formally standardized, it is regarded as an open protocol[1][2]. The physical layer of communication system is an RS-485 wired network, chosen for its simplicity, low cost and adequate data bandwidth. The forthcoming sections present detailed design of the proposed EMS including design objectives, functionalities and hardware-software used for development of the
1. Energy accounting, 2. Evolution and decision making 3. Decision implementation II. EMS SUBSYSTEMS The EMS can be split into various subsystems according to the basic functionalities implemented by it as mentioned below:
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system. The paper ends with concluding notes and identifying future scope of work in form of suggestions for further value addition.
6. Reporting the results and producing alerts as necessary for critical events including any deviations from the set targets. 7. Implementing management measures to rectify deviations. 8. Checking the accuracy of energy invoices. 9. Allocating energy costs to specific departments (Energy Accounting Centers).
III. DESIGN OF EMS A. Design objectives The major design objectives (as illustrated by Fig. 1) for the development of the proposed EMS are as mentioned below –
C. Hardware The proposed EMS has three-layer modular design architecture and modules in each layer are described below: 1) Field level modules: Also known as Device level modules, these modules consist of energy meters as their core components along with current transformers, potential transformers, etc. Energy meters measures electric parameters that contribute to the cost of electricity, such as Power (kW), Power Factor (ratio to active kW to kVA), Energy (kWHr), etc. They also monitor the parameters that indicate health of the electrical system, such as Voltage, Current and Frequency. The energy meters are also able to indicate other parameters like total harmonic distortion, average voltage, current, frequency. Energy meters should have RS-485 connectivity for establishing communication.
1. To observe and justify the rise or fall in energy usage. 2. To plot trends of energy consumption – on basis of weekly, seasonal, operational, custom, etc. 3. To predict and suggest futuristic trends in energy consumption due changes in business plans, etc. 4. To identify, suggest and diagnose specific areas wasting energy unnecessarily. 5. To develop performance targets for energy management programs. 6. To manage their energy consumption, rather than accept it as a fixed cost that they have no control over. B. Functionalities
Fig. 1 Network Diagram for EMS Fig. 2 Energy Meter[5]
The proposed EMS has been designed to achieve the functionalities mentioned below: 1. Measuring and recording energy consumption. 2. Correlating and thereby validating energy consumption to measured output, such as production quantity. 3. Comparing energy consumption to an appropriate standard or benchmark. 4. Setting targets to reduce or control energy consumption. 5. Comparing energy consumption to the set target on regular basis. 2
software
Fig. 3 Energy management loop illustrating major design objectives
Fig. 4 Parameters configuration window
Installing stand alone energy meters at various loads in plant will not be meaningful. Readings from these meters will be in the nature of raw data-for example, log books containing hourly voltage and current readings - and this has very limited use. Because of the geographical spread and the resulting time lag between readings from different meters, their data can not be correlated in real time. For example, when assessing shift-wise performance, if reading of one meter is at the start of the shift and another 30 minutes later, the results could be totally misleading. Hence, it is necessary to have software that collects data from all meters and display on computer in real-time. The proposed EMS uses GUI based applications developed on LabVIEW [3] platform for data logging. 3) LabVIEW: The application software for the EMS is developed using LabVIEW platform. It can be operated in two modes; the Auto Control mode or the Manual Control mode. For GUI development, we have used Laboratory Virtual Instrumentation Engineering Workbench (LabVIEW)[4], which is high-level graphical programming language developed by National Instruments. It supports interfaces such as GPIB, USB IEEE1394, MODBUS, SERIAL, PARALLEL, IRDA, TCP, UDP, Bluetooth, NET ActiveX, SMTP, etc. LabVIEW can be used for data acquisition, instrument control, and industrial automation on different platforms including Microsoft Windows, various flavours of UNIX, Linux, and Mac OS. Using LabVIEW, we have integrated the wired network consisting of an RS-485/USB converter and the energy meters for real-time parameter acquisition and monitoring. The GUI prepared using LabVIEW helps to acquire, analyse, record and report live data acquired using load indicators deployed at different geographic locations.
For development of the proposed EMS, we have used Multispan[5] make energy meter model AVH-13 (shown in Fig. 2). The meter accepts 3-phase 4-wire 230V AC (LN) voltage and current as inputs and provides information about 16 energy parameters. The Network diagram of the system has been shown below: As shown in fig 3, energy meters form field-level modules in system architecture of proposed EMS. They stay connected in form of an RS-485 wired network or communication and collect data from the field. 2) Interconnecting modules: These modules are also known as interfacing modules. They link various networks and/or network segments together for meaningful application implementation. The main role of these modules is protocol matching by conversion of protocol. An RS-485 to USB converter (shown in Fig. 4) has been used in the proposed EMS to interface live data collected from the RS-485 network of energy meters via USB port of PC based workstation.
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IV. LABORATORY IMPLEMENTATION Computer running LabVIEW HMI
RS-485 to USB converter Fig. 7 Historical report from EMS Fig. 5 Laboratory Implementation of the proposed EMS
The Online monitoring window for the proposed EMS has been shown in Fig. 7. In this window, mimics of different energy meters are created. Here the user has flexibility to choose any one of the two modes – auto or manual. In auto mode, the mimic will be automatically refreshed every 3 seconds, while in manual mode, the user has to select the parameters that he wants to see. The logging can be started by pressing the start button which will start logging of energy parameters into database with logging rate selectable in the range of 1-99 minutes. V. RESULTS The plots of the recorded data in trends form has been shown in Fig. 8 which can be used for future analysis. There are three charts in this window. The top-most chart shows the phase to neutral voltage for each phase. The middle one shows current chart for each phase. Remaining two charts are for power factor and frequency. Particular energy meter can be selected using the drop down selection menu and its data can be plotted and interpreted.
Fig. 6 RS-485 to USB converter
Photograph of Fig. 5 shows the laboratory implementation of the proposed EMS with an energy meter, RS-485 to USB converter and PC running LabVIEW GUIs. The Configuration Window for the proposed EMS has been shown in Fig. 6. In this window, the user can select configuration parameters such as number of energy meters, communication port, data type, meter name and meter address. Only selected number of meters shall be configured and displayed in online monitoring, while the others shall remain disabled.
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root causes of failures. Each step towards optimization may result in small amounts, which can subsequently add up to substantial amounts of savings. Advantages: 1. Energy efficiency: Ensure lighting and other electricity consuming equipments are off when not required. Optimize the performance of air conditioning/ heating equipment. 2. Greater control: Standardize HVAC set points and lighting schedules across the portfolio. Ensure local settings remain compliant with corporate standards. 3. Increase visibility: Track performance and receive alerts when assets are not functioning properly. Monitor energy consumption to spot excessive usage.
Fig. 8 Online monitoring window
Limitations: Capital expense, System complexity, Information over load – are some major limitations of the proposed EMS system.
Generation and analysis of historical data can be done using the proposed EMS as shown in Fig. 9. This analysis can report and identify the areas causing energy wastage and helps to implement corrective decisions for overall energy optimization.
VII. FUTURE SCOPE Enhancement of each and every facet is important for rapid growth and wide acceptance of the proposed EMS. Focus should be on making the proposed system rugged, reliable and cost-effective as well as user-friendly. This work can be further extended by – 1. Connecting GSM Modem – to enable the system to send SMS alerts in case of critical alarm/event. 2. Adding more and more functionalities to the GUI to make it more informative and user-friendly.
VI. CONCLUSIONS Modern energy management systems have matured due to advancements in metering; software tools for analysis, affordability, and maintainability. This has resulted in industrial organizations taking full advantages of this technology by their deployments in mission-critical applications to bring the electricity bill to its minimum. The design implemented in laboratory employs RS-485 for establishing connection between meters and computer. Data acquisition and recording in layer-1 use the industry standard, protocols of RS-485 and MODBUS. In this layer, applications are implemented using user-friendly LabVIEW GUIs. For EMS software, MODBUS protocol is selected because of interoperability, vendor independence and other merits. While off-line data analysis helps in system optimization, on-line monitoring helps to diagnose system problems and
ACKNOLEDGMENTS The first author acknowledges with thanks the support and co-operation provided by Dharmsinh Desai University, Nadiad, Gujarat, India and M/s Vbtech Automation, Ahmedabad, Gujarat, India in development of this work. REFERENCES [1] MODBUS Specifications and Implementation Guidelines [Online] Available: http://www.modbus.org
[2] Modicon MODBUS protocol reference guide. pp. 1-76 (http://www.Modbus-IDA.org)
[3] Online Help and Technical Support Documentation [Online] Available: http://www.ni.com/support
[4] Online Help and Technical Support Documentation [Online] Available: http://www.conzerv.com/case_study.
[5] Guide to energy management System, Chapter-1: Introductiion to Energy Management System, Robert Burhenn, Kristen Heinemeier, Terry Peters, pp.1–18, July 2010 [6] Cratty and Williams, “Energy Management Control Systems,” from Energy Management Handbook, The Fairmont Press, pp.48–82, July 2010
Fig. 9 Trends view in monitoring window
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