An Optimized Approach to Remote ...

FACULTY OF SCIENCE AND ENGINEERING DEPARTMENT OF ELECTRICAL ENGINEERING

An Optimized Approach to Remote Telecommunications Cell Site Power Solution

Research Paper

Submitted 4th February 2016, Approved 8th February 2016 Atlantic International University, Honolulu, Hawaii, United States Collins Geoffrey Mwambu, [email protected]

February 2016

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RESEARCH BACKGROUND This research is driven by the desire for an advanced study and analysis of existing hybrid power systems for remote telecom cell sites. It is also intended to add value and ensure Telecom Operators and Tower (Passive infrastructure) companies derive the maximum benefit from solutions they invest in with regard to minimizing network breakdown on the infrastructure and operational expenditure. It also seeks to introduce anti-theft features of quick moving Items such as Generators parts and design protection mechanisms coupled with remote management systems (A full scope study on Anti-theft will be discussed separately in the infrastructure security Paper -Covering both passive and active, focusing on remote equipment, underground cables and fiber protection in developing countries). Deploying a hybrid power solution doesn't exactly guarantee that the system will never breakdown. In fact, not all diesel generator mechanical parts or entire secondary power sources are fully managed remotely by existing hybrid solutions (referring to self-diagnosis system to detect such related malfunctioning parts prior to complete breakdown), but a wellresearched and carefully designed and tested model can improve efficiency up to about 80%. The purpose of this research is to explore a possibility of optimizing such systems to ensure an evolved total energy management system. In Separate papers, I will capitalize on integrating the mechanical system monitoring and also the electrical system. The most convenient being the early warning mechanism to allow sufficient time to fix the mechanical parts whilst equipment still holds life on backup power sufficient to hold services during the critical breakdown and repair period. This will in turn minimize the outage time and increase usage of hybrid solution. I will also study the efficiency of Remote Power Management Solutions (RPMS) to ensure effective and total remote power management. And lastly, most Telecom operators are largely attracted to invest in African markets, yet the actual rollout and acceptable coverage faces peculiar problems that make maintenance of such network investments a hard and expensive task. These will range from heavy electricity bills, limited grid coverage, equipment theft, to mention but a few. This Research Paper proposes a solution that will focus on maximizing network uptime, at the same time reduce on electricity bills, by allowing the power plant prioritize utilization of alternative cheaper sources and hence shorten your return on investment whilst maximizing business profitability.

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For Celine!

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ACKNOWLEDGEMENT The help of a number of people and a couple of online forums already indicated in the bibliography has been instrumental to the completion of this Thesis and continues to be as the plan to implement the proposed design solution goes in. Mohammed Javed Iqbal: Thank you for shaping the skeleton Idea that I couldn’t have had sufficient material to build on my own in this short time. Stephen Gray: Thank you for the advice contributed and for the reasoning out of the wiring diagrams together, reflected in this paper as a nice piece of work that took a little some more time to sketch to accomplish. My Supervisors at AIU: You did a wonderful job following up from time to time and reminding me of the limited time to complete this dream. Thank you for guidance and the opportunity to make my dream finally reach this far. Special Thanks to Dr. Jack for the timely response to my queries and guidance. And Finally to Admission Counselor: Kazumi Iwasaki. It was a nice guidance at the beginning without which I wouldn’t have reached this point. I’m glad I listened to you.

Collins Geoffrey Mwambu

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TABLE OF CONTENTS

Research background .............................................................................. i Acknowledgement...................................................................................iii Table of Contents ..................................................................................... iv Acronyms.................................................................................................... vi Abstract .................................................................................................... viii Chapter 1: INTRODUCTION ................................................................... 9 Chapter 2: Hybrid efficiency, challege and investigations ........10 Analysis of existing Power Hybrid solutions for Remote Infrastructure Support:................ 10 The Problem: ...................................................................................................................................................... 10

Chapter Three: LITERATURE REVIEW .............................................11 past literature: Introductions ...................................................................................................................... 11 Distributed Generation .............................................................................................................................. 11 Impact of Distributed Generation ......................................................................................................... 12 Wind DG and its Grid Integration Issues ............................................................................................ 13 FACTS Controllers ........................................................................................................................................ 14 Photo Voltaic Energy .................................................................................................................................. 16 Hybrid Energy- Wind/PV.......................................................................................................................... 17 Summary.......................................................................................................................................................... 20 Current research Information ..................................................................................................................... 21 Existing hybrid solution on the market, the setup, goal and challenge: ................................ 21 Basic concept of hybrid Power Solutions designers:..................................................................... 21

CHAPTER 4: solution DESIGN AND Description............................22 Introducing the Concept: ............................................................................................................................... 22 Grid Supply with Diesel Generator: ........................................................................................................... 22 Grid Supply with alternative power sources:........................................................................................ 23 The Design Strategy –Energy Management System (EMS): ............................................................ 25 System Components Description: .............................................................................................................. 27 Mains input ..................................................................................................................................................... 27 Line Sensing and Filtration ...................................................................................................................... 27 Utility Power supply ................................................................................................................................... 28 Load Sharing Technique and Power Stabilization.......................................................................... 28 iv

Auto bypass switch: .................................................................................................................................... 28 Genset input power ..................................................................................................................................... 29 Automatic Transfer Switch: ..................................................................................................................... 29 Genset control................................................................................................................................................ 29 Power Measurement................................................................................................................................... 30 DC power for Equipment with DC DB.................................................................................................. 30 Security lights & Tower light ................................................................................................................... 31 Remote Monitoring &Remote event handling ................................................................................. 31 Remote Power Management &Site Monitoring system .................................................................... 31 Key Benefits of the RPMS. ......................................................................................................................... 31 The Hardware Setup:....................................................................................................................................... 32

CHAPTER 5: Analysis of Results and Benefits: ..............................35 Sustainability of Telecommunications services ................................................................................... 35 Secured Power Supply: Securing critical operations with green power ................................... 35 opex reduction & Energy efficiency. ......................................................................................................... 35 Minimized pollution –minimizing genset runtime: ............................................................................ 36 Controllers: .......................................................................................................................................................... 36 Cell site Manager and controller: ............................................................................................................... 36

CHAPTER 6: Conclusion & Recommendations:.............................38 Bibliography .............................................................................................39

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ACRONYMS

AC CRF CVCI DC/DC DOC DSP D/A DC EDLC EMI ESR O&M HCC HESS IP IGBT IC ICC LCE LLP LPSP LVD MOSFET NPC FC OM NPV BR GR PCB PI SV SOC SMES TV TI AVR RPMS VRLA RMS IPS EMS WECS

Alternating current Capital Recovery Factor Constant voltage constant current DC to DC Depth of charge Digital Signal Processing Digital to analogue Direct current Electric double layer capacitor Electro-magnetic interference Equivalent series resistance Operations and Maintenance Hysteretic current control Hybrid energy storage system Initial payment Insulated gate bipolar transistor Integrated circuit Interrupted charge control Levelised cost of energy Loss of load probability Loss of power supply probability Low voltage disconnect Metal oxide semiconductor field effect transistor Net present cost Fuel: Net present cost Operation and maintenance: Net present cost Net present value Battery replacement: Net present cost Diesel-generator replacement: Net present cost Printed circuit board Proportional plus integral (controller) Salvage value State of charge Superconducting magnetic energy storage Television Turbulence Intensity Automatic Voltage Regulator Remote Power Management System Valve regulated lead acid Remote monitoring system Integrated Power System Energy Management System Wind energy conversion system vi

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ABSTRACT Telecommunications play a major role in shaping the world’s economy by facilitating information sharing. As such, it is essential to develop a reliable infrastructure to facilitate such a service. Considering the growing power supply demand for telecommunications infrastructure across the globe, isolated power generating units can be used as an alternative to electrify cell sites in areas where there is no grid extension. On the other hand, these units can also be used in remote areas with such services that require continuous power supply but connected to unreliable grid. At present however, the telecommunication sector is liable for its energy consumption and the amount of pollution it emits in the environment through these diesel consuming remote units or diesel generators. In the context of off-grid telecommunication applications, off-grid base transceiver stations (BTSs) are commonly used due to their ability to provide radio coverage over a wide geographic area. Majority of the off-grid BTSs still rely on emission-intensive power supply solutions from these diesel generators. In this paper, a sustainable solution for optimizing hybrid solutions in order to ensure effective powering of these BTSs is discussed. The key aspects in designing an ideal power supply solution is reviewed, and this mainly include the proposed design of an intelligent AVR solution coupled with a fully-fledged remote power management solution. This will cover the sizing and optimization approaches used to design the BTSs’ power supply systems as well as the operational and control strategies adopted to manage the power supply systems. The proposed solution will also make it possible to deploy on islands, in remote regions or in isolated industrial plants – where energy supply is often based on diesel generators or other small fossil-based power plants. This will be considered as a better way to produce energy through the hybrid solution and effectively manage it. The renewable energy systems will supplement traditional generators and, in combination with an intelligent control system, they will provide energy that is economical, reliable and more environmentally sustainable. This system will focus on reducing dependency on fuel, while significantly improving the carbon footprint on the environment by prioritizing dependency on the stored energy from renewable sources.

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CHAPTER 1: INTRODUCTION The rapid growth rate of electronic communication or data transmission across the globe indicates a vast demand of telecommunication services and therefore a great expansion of Telecommunications infrastructure. In 2011 and 2012, Industry predictions estimated that 75,000 new off-grid telecommunications cell towers would be built in developing countries. Over 50 million additional wireless subscribers were expected in Africa alone over a span of two years. Experts in Asia and South America estimated the wireless market to grow about 7–10% every year for a span of five years. These stats were published in an independent survey report carried out by Cummins –One of the leading Power Solutions provider. According to Statistics Brain Research Institute results released in March 2015, total number of cell towers grew from 900 in 1985 to 205,000 (beginning of 2015) in the US. As of November 2015, the total number of active internet users –Connected devices is about 3,366,261,156 according to the statistics report published by International Telecommunications Union. This is a direct translation in the increasing power demand, since this means more cell sites or telecom equipment will continue to be evolve in order to sustain the services. Most of these cell towers built for remote access in developing countries with limited of no grid will need generators and alternative energy sources for either emergency backup in urban areas or as primary power source for remote areas. In order for the emerging market players to sustain this increasing demand, the service providers must promise and offer a high standard of service quality which is continuous, reliable and accessible. Like all electrical/electronic systems, functionality means availability of a quality power supply. Because of this global requirement, many power experts have resorted to exploring cost effective power solutions and this has seen evolution of massive hybrid power manufacturers in the telecom industry, majorly as a way of cutting down operational expenditure. Since the area of hybrid power solutions is still under massive development, a lot of research is still required in order to develop solutions that are cost effective, less environmental impact whilst ensuring a continuous clean power supply to telecom equipment. This paper will seek to address the gap in the existing telecom power solutions and clearly elaborate the efficiency requirements and the factors to be considered in designing and configuring of such systems in order to derive Capital Expenditure value with more benefits to the environment. This will be delivered in the modular based design of an intelligent total power management system that will support remote troubleshooting through a preset threshold voltage that will ensure early warning and guarantee reduced downtime on the telecommunications infrastructure.

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CHAPTER 2: HYBRID EFFICIENCY, CHALLEGE AND INVESTIGATIONS ANALYSIS OF EXISTING POWER HYBRID SOLUTIONS FOR REMOTE INFRASTRUCTURE SUPPORT: There are many power solution providers today on the market that have developed hybrid and AVR solutions for telecommunications cell sites markets. These Hybrid solutions play a major role in cutting down the operational expenditure by prioritizing energy dependence on the cheaper alternative source whilst ensuring a continuous power supply. One of the basic feature is the energy storage through backup batteries with the aid of the hybrid rectifiers and switching the equipment over to the batteries once they are sufficiently charged. Whilst this is considered one of the best energy utilization efficiency strategy, there are a couple of controls that can enable effective energy management that still need to be explored in order to ensure maximum utilization. This is coupled with other management features such as fuel monitoring and battery voltage monitoring. A threshold battery voltage is preset which once reached during discharge, the system will automatically change the equipment over to the available power source in order to allow the batteries to recharge again. This automatic changeover allows to switch between the different available power sources logically with priorities set within the controller for which power source is primary and secondary. The primary source will be switched to as priority and only switch to secondary source if the primary source is unavailable or has developed a fault.

THE PROBLEM: The Problem with this solution however is that the system does not provide prediagnosis while the site is still on batteries, to know whether the changeover will be successful on the available power source upon reaching the discharge threshold. Should the available power source happen to develop a fault at the time the system is on batteries therefore, there will not be any early warning as to whether the changeover will be successful. This poses a potential risk to the equipment as there will be an abrupt shutdown due to power cutoff which takes some time to be detected and fixed. With the setting of the two threshold voltages therefore, the system will at the preferred time attempt to exit the battery cycle and perform a pretest before falling back on batteries. This will automatically pick up and flag a warning should there be a source failure, this gives time for the fault to be repaired before the second threshold is reached for the system to exits the battery cycle. This optimized solution seeks to address this problem. Similarly, many AVR designs on the market bundled with most solution have line monitoring capabilities and therefore in case of a one-line malfunction, the failed line will automatically be looped to provide a full 3 phase output. With the failure of the second line however, these are unable to utilize the remaining one line to loop and provide a 3 phase output whilst providing time for repair. This area will also be fully addressed in this paper with the help of the techniques described in the description above in addition to the remote monitoring and event handling system. The RPMS. 10

CHAPTER THREE: LITERATURE REVIEW PAST LITERATURE: INTRODUCTIONS Based on the studies carried out by several researchers and their contribution to research field motivates for further scope of research. In this chapter review of several research papers by various authors and technical reports has been discussed. Distributed Generation (DG) and their grid integration issues and later on solutions presented by several authors are presented. Also studies on the hybrid combination of PV/ Wind modelling and simulation by several authors using various tools have been discussed. Since in most remote areas DGs are still relied on as primary power source, it is important that we analyze the efficiency and discuss how the efficiency can be improved and also introduce additional power sources which can be integrated through an energy management hybrid system. DISTRIBUTED GENERATION The earliest electric power systems were DG systems intended to cater the requirements of local areas. Different definitions of DG have been proposed. Some have linked this to size of the plant, suggesting that DG should be from a few KW to sizes less than 10 or 50 MW. A review of alternative definitions of DG [(Ackerman et al., 2001), (IEEE), (CIRED, 1999), (CIGRE)], suggested that DG can be defined as the installation and operation of electric power generation units connected directly to the distribution network or connected to the network on the customer site of the meter. Comparison of renewable and nonrenewable DG options in context to their current status, evaluation of their future potential and cost of generation in Indian power sector are available [Banergee, 2006]. DG has a key role to play in power sector. It offers great potential to offset traditional utility investments in generation and transmission facilities. A report from EIA suggested that DG's contribution to electricity is predicted to increase drastically. Many researchers have investigated the importance of the DG and its applications in enhancing the electrical system. Daly et al., [2001] discussed different applications of DG and its cost analysis in their study. They presented different DG technologies and the potential benefits of DG that included reliability, deferral of power delivery investments, and environmental benefits. Joos et al., [2000], discussed the potential of DG to provide ancillary services. Their study demonstrated the potential of different types of DG along with proper power electronic interface to provide ancillary services to the main grid. The high performance development of power sector by DG is highlighted by Matthew [2009] and with the existing technologies, the developers and urban planners have a key ingredient to create sustainable cities with DGs. Banergee, [2006] and Gerwen, [2006], summarized the benefits of DGs by comparing different technologies of renewable sources. The viability of DG integration depends heavily on energy prices and stable policies to encourage serious investments by market 11

parties [Gerwen, 2006]. Malcolm [2003] suggested with incentives, recognition and rewards the possibility of encouragement to the distributed network operators. IMPACT OF DISTRIBUTED GENERATION Interconnecting a DG to the distribution feeder can have significant effects on the system such as power flow, voltage regulation, reliability etc. A DG installation changes traditional characteristics of the distribution system. Most of the distribution systems are designed such that the power flows in one direction. The installation of a DG introduces another source in the system. When the DG power is more than the downstream load, it sends power upstream reversing the direction of power flow and at some point between the DG and substation; the real power flow is zero due to back flow of power from DG. The 1547 series of IEEE standards for interconnecting distributed resources to the power system is a set of standards consisting of 6 parts [ieee.org]. These standards provide criteria and requirement for interconnecting distributed resources to the power system. The IEEE 1547.1, [2005] defines the requirement for interconnecting equipment that connects the DG to the electric power system. The IEEE 1547.2, [ 2 0 0 5 ] , provides t h e technical details and application to understand the IEEE standard. The IEEE 1547.3, [2005], guided and addressed engineering concerns of design, operation and integration of DG island systems. The IEEE 1547.6, [2005], focuses on standard criteria, test and requirements for interconnection distribution secondary network of area electric power system with local electric power system having distributed resource generation. The DG installation can impact the overall voltage profile of the system. Inclusion of DG can improve feeder voltage of distribution networks in areas where voltage dip or blackouts are of concern for utilities. The voltage issues related to the installation of DG on current electrical system have been discussed in many papers. Several debates on voltage impact on the grid when wind DG integrates have been carried out as it is most necessary for grid code maintenance. The impacts of DG on voltage regulation by Load Tap Changing (LTC) transformer were studied by Dai and Baghzouz [2004]. They found that the DG can cause under- voltages and over-voltages if proper LTC transformer controls are not applied. Several researchers have worked on the control models for the efficient operation of DG. Kashem and Ledwich [2004], studied on operation and control for DG installation in their work. They contributed a DG control model to improve the network voltage efficiently. Further they addressed network issues when multiple DGs are included in the network and presented analytical methods and solutions to develop design criteria for DG installation [Kashem and Ledwich, 2005]. Borges and Falcao [2003] discussed the role of DG in loss reduction based on a power summation method. Barker and Mello [2000], briefly presented on the impact of DG on losses of the feeder but analysis was not carried out.

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WIND DG AND ITS GRID INTEGRATION ISSUES Among renewable energy sources, wind power is the most attractive for mass production. This is supported by exponential growth into the installed wind generation capacity worldwide. The rapid increase in wind power installations over the past ten years have benefited tremendously from the technology advancements that have brought about significant reduction in the investment costs associated with wind generation. A wind power project typically has a fast payback period, a relatively small installation period and a low operation/maintenance cost, making it very attractive for Potential investors. This inspired the investors and lead to the growth of wind generation. The wind power programme in India was initiated towards the end of the Sixth Plan, in 1983-84. Indian wind energy outlook report of 2009 outlines Indian renewable installed capacity of 13.2 GW [IWEO, 2009] and the installed capacity has increased from 41.3 MW in 1992 to reach 13065.78 MW by December 2010 [IWEO, 2010]. The gross potential is 48,561 MW and a total of about 14,158.00 MW of commercial projects have been established until March 31, 2011. In terms of wind power installed capacity, India is ranked fifth in the World. The reports discusses not only about status of wind energy in India but also policy environment for wind energy, costs and benefits, demand projections, energy efficiency and growth rates. The report of OECD [2005] discussed that 'Grid integration concerns have come to the fore in recent years as wind power penetration levels have increased in a number of countries as an issue that may impede the widespread deployment of wind power systems' and mention that two of the strongest challenges to wind power's future prospects are the problems of intermittency and grid reliability. The report also highlights the most of the international collaborative work specifically categorizes the current focus into four main areas• Wind power prediction tools to improve forecasting for electricity production • Modelling and grid simulation studies and practices to ensure grid system optimization. • Investigations and planning of designs to reinforce and extend the grid • Analysis and development of grid access rules, technical code requirements and international standards. From these four areas the second one has been taken for this research study and presented and discussed in chapter 5 and 6. Researchers Martinez et al., [2004] have analyzed on the suitability of wind turbines with Doubly Fed Induction Generators (DFIG) for new grid operator norms that require ride through operations and shown that the use of power error vector control and active & reactive power reference reduction during voltage dips may be a good solution for low voltage ride through. Several researchers’ opinion is that in order to maintain the grid stable even after wind integrates there is a need for grid code maintenance. Rajesh, [C-WET] reported that there 13

is a need for Indian wind grid code as wind energy constitutes 12% of the installed capacity in the power scenario in India. With high penetration, overall power system gets affected and hence grid code envisages establishing a standard operating practice. The grid codes for wind in general deal with active power control, frequency, voltage and reactive power issues, fault ride through capability, protection and power quality issues like flicker, harmonics. According to the report variation of frequency can lie between 47.5-51.5 Hertz for stable operation. For all the above necessary statements FACTS Controllers are the solution as they are more reliable and best option. Improved utilization of the existing power system is provided through the application of advanced control technologies.

FACTS CONTROLLERS Power electronics based equipment or FACTS provide proven technical solutions to address the new operating challenges. FACTS technology allows the improved transmission system operation with minimal infrastructure investment, environmental impact, and implementation time compared to the construction of new transmission lines. Constructing new transmission lines becomes extremely difficult, expensive and time consuming. FACTS technology provides advanced solutions for the existing transmission lines which would be cost effective alternative for new transmission line construction. Major problem for maintenance of grid codes are with respect to voltage variations. These problems are traditionally solved by reactive power compensation by capacitor banks or with on load tap changers. But FACTS controllers bring a wide opening for all the problems. Paserba [2007] discussed the issues and benefits of applying FACTS controllers to AC power systems. He also presented all the associated problems of power system for stable operation and suggested which type of FACTS controller to be used to solve those problems. Tyll and Frank [2009] presented different types of reactive power compensation by FACTS controllers and addressed real implementation of several controllers at different regions. Jones [2007] addressed how FACTS technology helped in improving at least 10%15% of transmission capability of lines and mentions ABB taken initiative of installing over 600 FACTS applications in 50 countries. Panda and Padhy, [2007] investigated the dynamic behavior of WTG during an external three phase fault with STATCOM and without STATCOM under various wind speed changes. Simulation results show that STATCOM prevents large deviations of bus voltage magnitude induced by reactive power drawn from distribution network by WTGs. 14

Salman and Teo [2005] investigated the dynamic behaviour of multiple wind farms that are integrated to the same network. The authors concluded that the behaviour of wind farm under fault condition connected to the network, influence the stability of other wind farms connected to the same network. To solve this problem critical clearing time of multiple wind farms can be slightly improved using VAr injection technique. They achieved by installing Static Synchronous Compensators (SSC) at selected location. Keane et al, [2011] proposed a passive solution to reduce the impact on transmission system voltages and to overcome the distribution voltage rise barrier. They developed a methodology which optimizes the power factor and tap changer settings of the distribution network section such that distribution voltages are obeyed at all times. Wilch et al., [2007] addressed the reactive power generation of offshore wind parks using DFIG connected to the main grid with long cables along with reactive power compensating devices. Both studies had not used FACTS controllers for compensation. Roohollah et al, [2008] used TurbSim, AeroDyn, FAST, and SIMULINK to model the aerodynamic, mechanical and electrical aspects of a wind power system including STATCOM. They studied the performance of STATCOM controller for different wind disturbances to the wind energy converting systems. They also showed that wind speed and wind direction changes have different effects on the generated power and voltage. Oskoui et al., [2010] presents the implementation of Holly STATCOM at Austin. Since its inception, STATCOM for overall system performance was appreciated. Grunbaum et al.,[2004] showed that when the network is weak local dynamic reactive power support may prevent voltage collapse and make it possible for the wind farms to recover and remain in service after a short circuit event. They also discussed a dynamic voltage control scheme based on a combination of SVC and STATCOM technology. A report from ABB [2012], on renewable energy, presented wind integration with the grid and the challenges to maintain grid code at various countries like, Great Britain, Australia, Poland, Norway, Korea etc. with the help of PCS100, a fully dynamic STATCOM. ABB also reported that the outstanding performance for dynamic operation of the wind farm is possible by STATCOM. It is known that the SVCs with an auxiliary injection of a suitable signal can considerably improve the dynamic stability performance of a power system. In the literature, SVCs have been applied successfully to improve the transient stability of a synchronous machine [Byerly, 1982]. Hammad [1986] presented a fundamental analysis of the application of SVC for enhancing the power systems stability. Then, the low frequency oscillation damping enhancement via SVC has been analyzed by various investigators [(Padiyar and Varma, 1991), (Zhou, 1993), (Oliveira, 1994), (Wang and Swift, 1996)]. SVC enhances the system damping of local as well as inter area oscillation modes. It was observed that SVC controls can significantly influence nonlinear system behaviour especially under high-stress operating conditions and increased SVC gains. Rodriguez et al., [2004] showed the results of stable operation of the wind energy conversion systems 15

with the aid of SVC. The reference list of SVCs installed all over world is given in www.siemens.com. The Siemens states that over 30,000 MVAr capacities of SVCs have been installed. Various authors discussed the performance comparison of SVC and STATCOM. Ali et al., [2010] showed the results with SVC and STATCOM and concluded STATCOM is much more capable of stabilizing the network due to its inherent factors. Noroozian et al., [2003] examined the overall performance of SVCs and STATCOMs. The impact of SVCs and STATCOMs are studied separately on a system and simulation results showed that the STATCOM solution allows faster voltage recovery compared to SVC. Based on the literatures, for this study, STATCOM was chosen to solve the grid integration issues. Most of the investigators analyzed the system behavior considering three phase fault for some milliseconds and for fixed STATCOM rating. A complete study on different type of faults at PCC and at wind turbine generator (WTG) are essential to achieve overall power quality of the system. Since the study is not only to see the better performance of the existing wind farm using STATCOM, but also to suggest hybrid combination of PV energy with the wind energy with in and around the space availability of Wind Farm. So literature survey on PV Modelling and simulation of PV arrays were carried out. PHOTO VOLTAIC ENERGY Villava et al., [2009] analysed the development of a method for the mathematical modelling of PV arrays. They have proposed an effective and straight forward method to fit the mathematical I-V curve to the three, remarkable points without the need to guess or to estimate any other parameters except the diode constant. They have also provided all the necessary information to easily develop a single- diode photovoltaic array model for analysing and simulating a photovoltaic array. Altas and Sharaf [2007] introduced a simulation model for photovoltaic arrays to be used in Matlab-SIMULINK GUI Environment. The model is simulated connecting a three phase inverter showing that, the generated DC voltage can be converted to AC and interfaced to AC loads as well as AC utility grid system. Lloyd et al., [2000] developed a reliable and repeatable methodology for the assessment of Maximum Power Point Tracking (MPPT) performance. They had modelled a simulator using Ispice and SIMULINK. Ropp and Gonzalez [2009] addressed a Matlab SIMULINK model of a single phase grid connected PV inverter that have been developed and experimentally tested its performance. Hamrouni and Cherif [2007] found an approach of modelling and control of a grid connected photovoltaic system. Here a MPPT controller is used to extract the optimal photovoltaic power; a current and a DC link voltage regulator are used to transfer the 16

photovoltaic power and to synchronize the output inverter with the grid. Hernanz et al., [2010], developed a model based on other studies and that model has been validated with experimental data of a commercial PV module, Mitsubishi PV- TD1185MF5. Kishore et al., [2010] presented the determination of resistances of PV cell with adjustments of characteristics that correspond to maximum power point. The influential environmental factors like; dust, solar radiation intensity, shadow, temperature and wind velocity are considered. The study by Villalva et al., [2010] deals with the regulation of the output voltage of PV arrays. They have presented a detailed analysis of the PV voltage regulation problem using a buck converter as PV array interface. Bogdan et al., [1994] developed a methodology for calculation of the optimum size of a PV array for a stand-alone hybrid wind/PV system. The least square method was used to determine the best fit of the PV array and wind turbine to a given load. Also an algorithm was developed to find the optimum size of the PV array in the system. This literature reveals the investigation on hybrid energy has almost begun in 1990's. The discussions on PV modelling and simulation by several authors, guided this study for the PV park to integrate the grid along with wind integration. The combination of PV and wind integration creates a hybrid generation which aids the existing system. Lot of research study is going on the area of PV modelling and its efficiency improvement. HYBRID ENERGY- WIND/PV Use of renewable energy technology to meet the energy demands has been steadily increasing for the past few years, however, the important drawbacks associated with renewable energy systems are their inability to guarantee reliability and their lean nature. Presently, standalone solar photovoltaic and wind systems have been promoted around the globe on a comparatively larger scale. These independent systems cannot provide continuous source of energy as they are seasonal. Standalone solar photovoltaic energy system cannot provide reliable power during non-sunny days. The standalone wind system cannot satisfy constant load demands due to significant fluctuations in the magnitude of wind speeds from hour to hour throughout the year. To solve these problems energy storage systems will be required for each of these systems in order to satisfy the power demands which are of very expensive. Hence Hybrid power systems are better option whenever, wherever individual renewable DG is considered. Mualikrishna and Lakshminarayana [2008] proposed a hybrid system with solar and wind sources for rural electrification. Authors compare standalone wind and standalone PV with Hybrid combination and concludes that hybrid would be the best option and viable if PV module cost is below Rs 100/W and its efficiency is higher than 20%. Nayar et al., [2007], discussed the implementation of PV/Wind/diesel micro grid system in republic of Maldives, a remote island. They insisted the hybrid system which has been installed was commissioned in August 2007 is able to perform better and detail study on daily power flow of each energy has been tested practically. From the recorded data daily energy output from wind, PV and diesel was plotted and shown in the paper after first month of 17

installation. They concluded that the newly developed and installed system will provide very good opportunities to showcase high penetration of renewable energies using wind turbines, photovoltaic modules, advanced power electronics and control technology. Zahedi and Kalam [2000], developed a methodology for calculating the correct size of hybrid system and optimized the management of the same system. Main power for the system considered is PV and wind and diesel is used as backup in this hybrid system. The system is considered as autonomous as it is not using national grid supply. The system was designed by calculating monthly demand of electrical energy required. Size of the battery bank is worked out to substitute the PV array during cloudy and non-sunny days. Kumar et al., [2011] proposed a hybrid system which includes PV/Wind/MicroHydro/Diesel power generation suitable for remote area applications. They have designed the model to provide an optimal system configuration based on hour by hour data for energy availability and demands. They also found based on simulation results that renewable/alternative energy sources will replace the conventional energy sources and feasible solution for remote and distant locations. Chang et al., [2007] discussed about the fact that if appropriate renewable energy sources are selected and used complementarily, the overall performance and potential supply time are anticipated to exceed those obtained by the individual use of these resources. The study they carried out is on the complimentary operation system, consisting of PV and Wind systems. Homer software was used to illustrate and evaluate the technical and economic aspects of the hybrid system. An attempt was made by Rehman et al., [2011], to explore the possibility of utilizing power of the wind and sun to reduce the dependence on fossil fuel for power generation to meet the energy requirement of a village in Saudi Arabia. In their study they adopted wind/PV/diesel as hybrid system with 35% renewable energy penetration (26% wind, 9% PV) and 65% diesel power contribution as the most economical power system. They concluded after estimation that the cost of energy of only diesel power system was found to be more sensitive to diesel price than the cost of energy of hybrid power system. Soltani et al., [2008] proposed an average model of a hybrid wind photovoltaic generating system. Model of the solar generating subsystem has been developed with integration of power losses model involved in the power converters. It is also shown that the model is interesting for analyzing the dynamic behaviour and for optimum design of the hybrid system. Karami et al., [2010] developed a hybrid topology which exhibited excellent performance under variable load power requirement. The proposed system is only for noninterconnected remote areas. Simulation results obtained had proven their proposed power management strategy worked properly. Curea et al., [2004] developed a test bench for the analysis of hybrid system behaviour which constitutes a wind generator, PV panes, storage batteries, inverter, diesel 18

generator and a load. First they studied about the system behaviour for the variations of the wind speed and solar radiation. In the next step analysed power quality issues due to balanced and unbalanced load variations. The test bench used marked for the validation of the simulation model. Lew et al., [2009] studied on the western wind and solar integration, which is one of the largest regional wind and solar integration studies examining the operational impact up to 35% wind, PV and concentrating solar power on the west connected grid in Arizona, Colorado, Nevada, New Mexico and Wyoming. The goal was to understand the costs and operating impacts due to the variability and uncertainty of wind, PV, and concentrated solar power on the grid. The study did not focused on the cost of generating wind or solar power but rather on the operational costs and savings due to fuel and emissions. Jeon et al., [2007] proposed a multifunctional grid connected wind/PV/BESS hybrid generation system. The principle of the proposed system and power control scheme for multi operation modes were described. Fargali et al., worked on a new geothermal space heating system, which uses PV-wind energy sources to feed the electrical loads of the heating system in a remote area in Egypt. They also presented a complete mathematical modelling and MATLAB SIMULINK model for the different components in both electrical and geothermal subsystems. The results illustrated that the designed control technique enables the developed system to be in correct and continuous operation.

Chedella et al., [2010] presented the preliminary study of modelling a small standalone AC system with the fuel cells and solar panels as energy resources. The solar energy is main energy source for electricity generation during the day and will be complemented with the fuel cell and battery during night. A new converter topology for hybrid wind/PY energy system is proposed by Jacob and Arun [2012]. They were influenced by the authors Hui et al., [2010] who presented a new rectifier stage topology for hybrid wind-solar energy system. The new converter used the cuk and single ended primary inductor converter type of DC- DC converters. Chen et al., [2007] designed a hybrid system consisting of PY power system, wind power system and battery storage. A novel controller links each of these components to ensure that one system will be supplying load dependant on the weather conditions. Detailed results on tested various weather conditions and temperatures are presented. Kim et al., [2006] dealt in their research on power control of a wind and solar hybrid generation system for interconnection operation with electric distribution system. Modelling and simulation study on the entire control scheme was carried out using a power system transient tool, PSCAD/EMTDC. The results of their simulation showed the control performance and dynamic behaviour of the wind/PY system.

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Giraud et al., [2001] reported the performance of a 4 KW grid connected residential wind-photovoltaic system with battery storage located in Lowell, USA. This paper also includes the discussion on system reliability, power quality, loss of supply and effects on the randomness of the wind and solar radiation on system design. Phrakonkham et al., [2010] discussed the status and development of electrification as well as the available renewable energy sources. They summarized on different micro grid configurations and on simulation tools. They continued their case study with respect to economic optimization using two different simulation software tools, HOMER and HOGA. SUMMARY After carrying out the literature survey the research work had one orientation towards the importance of renewable energy in the upcoming years and the associated problems when they work on either stand alone or grid integrated system. The solutions suggested by several authors in their research for most of the issues caused by the DG integration. Recent development of power electronics introduces the use of FACTS controllers in power systems. FACTS technologies not only provides solutions for efficiently increasing transmission system capacity but also increases available transfer capability, relieves congestion, improve reliability and enhances operation and control. Whenever renewable energy integrates the grid fluctuations in voltage, change in power flow pattern, voltage flicker and harmonics are reported to be common problems associated with grid. Hence maintenance of grid code becomes very essential to achieve good power quality. For all these issues FACTS controllers are better solution. Voltage sourced converters like STATCOM, SSSC or UPFC are more attractive as their operation is not so strongly dependent on the grid conditions. Series devices yet did not receive too much attention in wind power field as their role is on transmission system not on generation site and this did not probably attract wind generation owners. On the other hand, shunt devices are normally deployed not only inside the transmission network but at load and generation buses. UPFC has only very few experimental applications due to its high cost. The application of FACTS devices to enhance the dynamic and transient performance of power systems which includes large wind farm using simulation study on three phase short circuit test at PCC on the test system using PSCAD/EMDTC has been carried out. Such studies were limited to only three phase fault at PCC. Previous researchers have used a combination of SSSC and STATCOM to damp oscillations. Results showed that the FACTS devices provide an effective means in dynamic LLG faults at PCC and as well as at WTG. The effect of different combinational faults with STATCOM and without STATCOM is to be studied to achieve better power quality. There is a need for investigating the fault ride through capability of STATCOM when connected at PCC. Details of WTG is also not analyzed which is important to identify each turbine behavior under different scenarios. 20

Based on recent publications it is found that there is a scope for further research in the area of power oscillations damping of squirrel cage induction generator, harmonics, flicker mitigation and fault ride through capability of various faults using STATCOM for grid integration of wind energy. Since several studies suggested having hybrid combination rather than individual renewable sources for better and reliable operation of power system, this research study further carried out with PY simulation for estimation and cost analysis of PY plant in and around the study area chosen. Hence it was envisaged to carryout STATCOM implementation at PCC with all possible different faults at both PCC and WTG and proposal of PY plant with the existing wind farm.

CURRENT RESEARCH INFORMATION EXISTING HYBRID SOLUTION ON THE MARKET, THE SETUP, GOAL AND CHALLENGE: While acknowledging that Fuel, Generators and maintenance are the major operational costs for telecom operators running remote access network cell sites, there are also greater losses embedded in hidden costs such us vehicles (mileage) wear and tear while attending to major service breakdowns due to undetected power failures, quality of service issues due to delayed restorations and most of all blowing up of equipment due to unstable supply. Lots of manufacturers on the market today focus on the fuel reduction, generator and maintenance cost while the latter is overlooked. It is important to note that these losses are quite often massive and can’t be quantified. A combination of both will deliver a total power management solution whilst attracting more customers/ tenants on the operator’s infrastructure and will ensure sufficient funds for expansion and keep the network clean and competitive. BASIC CONCEPT OF HYBRID POWER SOLUTIONS DESIGNERS: Lots of experts focus on providing hybrid solutions at competitive prices through minimizing fuel consumption and maximizing battery run time of all essential loads. This is usually first priority. Other factors like environmental hygiene, protecting operator equipment from surges brought by dirty/ unstable grid come secondary. This so because of limited resources and therefore the operator can easily realize the return on investment in a shorter period of time. The problem with this however that it leave a lot of undiscovered capabilities as designers only look at competitive prices and no one looks at the minimum possible production cost with maximum results such as total energy management while combining all the factors affecting the industry.

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CHAPTER 4: SOLUTION DESIGN AND DESCRIPTION INTRODUCING THE CONCEPT: The current growth rate in cellular subscription across the world indicate that there will be a double demand in such services in the next decade as the number of mobile devices in use will be more than the human population in the world. In order to serve this growing demand, many telecom operators are expanding telecom infrastructure into remote areas of the world. This means that towers will be sited in remote areas such as forest reserves where the grid power is unreachable, or in areas with very unstable grid supply of electrical power. Telecom towers infrastructure companies (TowerCos) in remote areas have long relied on diesel generators as a source of power. But diesel generators operate at a lower efficiency level, are costlier to operate due to diesel costs, high noise levels and produce high CO2 emissions. This is the main reason there has been a rapid evolution of hybrid solutions which support multiple power sources such as solar, wind and power storage options through battery banks. All these are aimed at reducing the operational expenses whilst providing a continuous power supply. Several of these too operate in areas of grid as secondary power sources, but still the question of grid stability and high energy bills is a challenge which requires exploring extensively the capabilities of hybrid power solutions. This chapter explores two key design features that will enable effective optimization of any hybrid solution.

GRID SUPPLY WITH DIESEL GENERATOR: For grid connected sites however, unstable power can potentially lead to equipment damage, compromise service stability and result into high operational expenditure by resorting to running diesel generators. Stable power directly translates into maximum uptime, OpEx reduction by reducing generator runtime, which implies uninterrupted power supply at the maximum available time and assuring an acceptable quality of service. This kind of stability is achieved harnessing the grid and stabilizing the voltages by use of an AVR (Automatic Voltage Regulator) solution.

22

This paper will propose and explore the design of this scalable solution together with a Site Remote Monitoring functionality (RPMS) in order to deliver a total Energy Management solution (EMS.) With these two features, the following shall be achieved.

GRID SUPPLY WITH ALTERNATIVE POWER SOURCES: In remote areas with reasonably stable grid, this solution can further allow alternative low cost power sources to be utilized in order to minimize the energy bills. Solar PV and wind generation can be integrated to help reduce grid dependency. A typical load at a telecom site powers transmission equipment and the radio base station, but in hot hours of the day, the power needs will increase in order to operate the cooling plant at all times. With increasing transmission load at peak hours, the energy demand further increases to support the excess load. The load needs could range between 2kW to 10kW. This high energy requirement eventually increases the operational expenses. By integrating a gridtie system, the generation of solar PV and/or wind power can effectively support most of the loads and offset the peak load demand during these peak hours where excess load or excess cooling in needed. This will result into immense reduction of the energy costs. The two solutions combined will form an intelligent AVR (iAVR) solution that is able to interact with the NOC (Network Operations Center) and the site engineer. The functionality will be fully explained in the preceding paragraphs. A typical design impression of an iAVR solution with a hybrid controller on a remote telecom cell site is shown below:

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Stability & Hybrid Overview Generator Equipment iAVR

Genset

5

1

Local Power Supply

AC Feed to Stability

CAT 5 Comm

AC Feed

Fuel Level ATS/ACDB

3x 2.5mm Flex

6

4

AC Feed

CAT 5 Comm

3

Hybrid Back up Controller

Earth 25mm

2 AC Feed to Stability

AC Feed to Hybrid

3x 2.5mm Flex

Site Earth Bar

3x 2.5mm Flex Earth

DC Feed

3x 2.5mm Flex

DC DB

BTS and DC Power Equipment

DC Feed

PV Panels DC Feed

Wind Turbine

DC Feed DC Feed

BTS

Site Tower Status: Draft Version: 1.0

Date: 22-02-2016

Owner: Geoffrey Collins

Fig: 1 24

Purpose: Academic Research

THE DESIGN STRATEGY –ENERGY MANAGEMENT SYSTEM (EMS): This section presents a low cost design with modular type features capable of handling appropriate load capacity. The multiple power source inputs are designed as easily removable plugin cards and control card can be expanded for desired output depending on the user requirement. The system is self-protected and therefore no additional external devise is required for extra protection. Automatic bypass switch transferring the load to the utility grid or during unstable inputs and in case of unit fault. The system is also integrated with a remote monitoring and remote event handling capabilities. In order to ensure a total power solution, this system will deliver feature required for operations and maintenance (O&M). EMS total power solution design details are indicated and fully explained, together with multiple energy source inputs such as solar, wind, Generator and grid. This kind of load handling and site security features can also be applied in industries that have remote management requirements, banking sector and other organization. This paper further presents a design proposal with basic wiring diagrams. There will be need to discuss and analyse every module on circuitry level during R&D. The Figure presented below shows the basic design with an integrated Power system:

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EMS

LOAD 14. Security lights & Tower light.

11. Solar controller input

13. Output for utility socket (AC DB) 12. Wind Turbine input

10. DC power for BTS with DC DB

Integrated Power System (IPS) 9. Power Measurement

6. Genset input power 17. System access & Site security

7. ATS

8. Genset control

15. Wireless control onsite 16. Remote Monitoring & Remote event handling

5. Auto bypass switch

4. Load Sharing Technique and Power Stabilization

AVR 3. Utility Power supply

2. Line Sensing and Filtration

1. Mains input

Fig: 2 26

SYSTEM COMPONENTS DESCRIPTION:

MAINS INPUT o Utility input will terminate on MCCB (Moulded case Circuit Breaker) in the event that the current is more than 500A or MCB (Miniature Circuit Breaker) which can support up to 100A. It is however worth noting that for high power quality, MCCB is preferred. The choice of the breaker therefore will depend on the unit rating and specifications. This also visibly shows the Neutral to 3 line lines with Earth Bar which justifies system Protection. LINE SENSING AND FILTRATION Input standard line filtration component include: o The Surge Protection Device (SPD) which is a component of the electrical installation protection system. This device is connected in parallel on the power supply circuit of the loads that it has to protect. It can also be used at all levels of the power supply network. Its basic design function is to limit transient overvoltage of atmospheric origin and divert current waves to earth, so as to limit the amplitude of this overvoltage to a value that is not hazardous for the electrical installation and electric switchgear and control gear. Figure below shows a typical example of SPD in circuit. (Source: Electrical Installation Wiki).

Fig:3

o Earth bar: This provide a convenient common earthing point for electrical installations 27

Input line monitoring controller o Input three phase step down transformer 100V:1v Ratio  L1, L2, L3 sensing  Zero crossing voltage, frequency and G-L1, L2, L3 voltages detection. o Input three phase with neutral step down transformer 100V:1v Ratio  L1, L2, L3 sensing  Zero crossing voltage and frequency, N-L1, 2, 3 voltages detection o Caparison between both sensing for neutral detection o Controlled OUVI input switch (Magnetic contactor and SCR) o Voltage between Neutral and Ground o Time delay o Self-powered o Communication

UTILITY POWER SUPPLY This Switched Mode Power Supplies (SMPS) will allow multiple inputs from all the various sources such as Mains AC power, Genset power, Back up batteries, Solar and wind, and it will process desired outputs like 5v 10Amp, 12v 5Am, 24 +/_ 2Amp. LOAD SHARING TECHNIQUE AND POWER STABILIZATION The circuit design will include typically of a number of circuits below in order to ensure proper load sharing and a stabilized system output; o 3 Phase Rectification circuit o Dc Power Factor Correction o 48/24 Dc voltage output modules (SMPS) 3000 watt each (For detail: 10. DC power for BTS with DC DB) o Three Phase Sine-wave Oscillator Circuit o IGBT (Insulated gate bipolar transistors) Drive Circuit o IGBT Drain Supply SCR Controller Circuit o Output Line Filter o Output Isolation transformer 1:1 Ratio o Modular type 10kva each o Communication AUTO BYPASS SWITCH: Bypass or Isolation transfer switch is used to transfer of large motor loads, transformers, uninterruptible power supplies (UPS) systems or load shedding to a neutral "center" 28

position. It is designed for applications where maintenance, inspection and testing must be performed while maintaining continuous power to the load. This is typically required in critical life support systems and standby power situations calling for safe system maintenance with no power disruptions. Two pivotal points to watch during successful implementation. That is correct power optimization and Load isolation as part of the integrated power system. (Source: http://www.geindustrial.com, http://power.cummins.com)

GENSET INPUT POWER o Neutral to 3 Line terminal block termination or MCCB depending on the desired output to handle the load. AUTOMATIC TRANSFER SWITCH: A standard automatic transfer switch (ATS) has only three major functions: sensing normal source availability, sensing emergency source availability, and transferring power to the most desirable source at the appropriate time. The key monitoring points for the various inputs will there include, Standard ATS with Line Sensing and Filtration, Genset control, Mains contactor and Genset contactor. GENSET CONTROL o AMF: An AMF control panel (Automatic Mains Failure control panel) is utilized where you have to control a generator that is connected to the Mains in a standby configuration. The AMF control panel is fitted with an AMF controller that manages, in a fully automatic way, the connection assignment of the LOAD to MAINS or GENERATOR avoiding connection MAINS to GENERATOR. The major panel components includes sensing functionalities such as 3 phase and neutral sensing and brownout sensing. The AMF controller is conveniently tasked with driving the power circuit breakers. The size of the circuit breaker capacity and wires defines the required power rating of the panel. The parameter and check points include all Genset safety check before running, all Genset parameter check during warm-up, all Genset parameter check on load, change over and interlocking, all Genset and Mains parameter check during Genset cool-down and communication. o Hybrid All hybrid functionalities and master control such as Genset Remote Starts /Stops for O&M, BBU, Solar and Wind, Low battery voltages, Deep discharge and High temperature, all as indicated in the diagram in figure1. o Fuel measurement 29

An embedded additional functionality for accurate fuel measurement for O&M and utility bills via the fuel sensor fitted tank and communication of status. POWER MEASUREMENT o All measurable power parameters such as Mains Input Power Measurement, Genset Running Hours and Power Consumption Measurement, AC Output Power Measurement for tenant, Dc Output Power Measurement for tenant and communication.

DC POWER FOR EQUIPMENT WITH DC DB Fitted with 48/24 DC voltage output modules (SMPS), the below table summarizes the DC level expected parameters, inputs and outputs. Controller

  

LCD display Without computer configurable Communication port

Input

 

AC power Solar and wind

Output voltages

46-57.6 VDC

Output power

3000w each modules

Output current Maximum with over load protection Low voltage protection during backup

60A

SOH (state of health)

Sensing and controller circuitry for battery health

SOC (state of charge )

Adjustable

DOD(Depth of discharge )

Adjustable

Efficiency

95%

Output voltage tolerance

>+/- 1%

Output voltage ripple