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40220140503005

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  • 1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 34 STATCOM BASED POWER QUALITY IMPROVEMENT IN GRID CONNECTED RENEWABLE ENERGY SYSTEMS K M Mamatha1 , Nalini.S2 1 4th Semester, M.Tech(Power Electronics) 2 Associate Professor Department of Electrical and Electronics Engineering, Dr. Ambedkar Institute of Technology, Bangalore, India ABSTRACT The power quality of the system is affected when it is connected to a renewable energy sources like wind, solar etc. Hence the power injected by such sources degrades the system performance. The scheme used in this paper tells about maintaining the unity power factor at the source side, reactive power support only from STATCOM to wind Generator and Load and a simple bang-bang controller for STATCOM to achieve fast dynamic response. Key-words: IGBT (Insulated Gate Bipolar Transistor), IG (Induction Generator), FACTS (Flexible Alternating Current Transmission System). 1. INTRODUCTION With increase in the demand for Electricity due to increase in population and industrialization, the Generation of power is really a challenge now a days. If we want to increase the power generated in the conventional way i.e., by means of non-renewable energy sources like coal, diesel, natural gases and similar fossil fuels, the pollution increases which degrades the Environment and human life style. Compared to the non-renewable energy sources these have the advantages of the following: 1. The sun, wind, geothermal, ocean energy are available in the abundant quantity and free to use. 2. The non-renewable sources of energy that we are using are limited and are bound to expire one day. INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY (IJEET) ISSN 0976 – 6545(Print) ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME: www.iaeme.com/ijeet.asp Journal Impact Factor (2014): 6.8310 (Calculated by GISI) www.jifactor.com IJEET © I A E M E
  • 2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 35 3. Renewable sources have low carbon emissions, therefore they are considered as green and environment friendly. 4. Renewable helps in stimulating the economy and creating job opportunities. 5. Renewable sources can cost less than consuming the local electrical supply. In the long run, the prices of electricity are expected to soar since they are based on the prices of crude oil, so renewable sources can cut your electricity bills. But even though they have their advantages, they are not preferred due to economic criteria of investing huge funds. Also the problems that we face when we integrate these energy sources to the grid are quite many like power quality maintenance.In this paper we consider Wind power that can be utilized for generation of electrical power using Wind farms with FACTS device STATCOM to compensate the disturbances that occur due to the fluctuating nature of the wind. 2. METHODOLOGY In this proposed scheme a FACTS device STATIC COMPENSATOR (STATCOM) is connected at a point of common coupling with a battery energy storage system (BESS) to reduce the power quality problems. The battery energy storage system is integrated to support the real power source under fluctuating wind power [6]. The FACTS Device (STATCOM) control scheme for the grid connected wind energy generation system to improve the power quality. The STATCOM is acompensatingdevice whichis usedtocontrolthe flow ofactive and reactive power required to the Induction Generator of the wind turbine. It is a custom power device which is gaining a fast publicity during these days due to its exceptional features like it provides fast response, suitable for dynamic load response or voltage regulation and automation needs, Both leading and lagging VARS can be provided, to correct voltage surges or sags caused by reactive power demands pulse STATCOM can be applied on wide range of distribution and transmission voltage, overload capability of this provides reserve energy for transients from the BESS [1]. The pulse STATCOM is controlled using the PI controller. 3. TYPES OF POWER QUALITY PROBLEM The power quality problems are listed below: 1. Transients 2. Long Duration Voltage Variations 2.1 over voltage 2.2 under voltage 2.3 sustained interruptions 3. short duration voltage variations 3.1 interruptions 3.2 sags (dips) 3.3 swells 4. voltage and current imbalance 5. voltage fluctuation 6. power frequency variations 7. waveform distortion 7.1 harmonics 7.2 inter harmonics 7.3 noise
  • 3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 36 Elimination of these problems are analyzed and discussed in the paper [4] and the STATCOM is used to overcome the power quality problems. 4. BLOCK DIAGRAM The propose system consists of three phase AC source, Wind power generating system, non- linear load, STATCOM with Battery energy storage system [1], PI controller. The three phase bridge rectifier. Figure 4.1: Block diagram of the proposed system Is used as a non-linear load. The block diagram for proposed method is shown in Figure 4.1.The STATCOM and PI controller in order to eliminate harmonics, to compensate reactive power demand and to maintain unity power factor at source side. Wind generating system using induction generator. It requires reactive power for magnetization. When the generated an active power of an induction is varied due to wind [3]. Absorbed reactive power and terminal voltage of an induction generator can be significantly affected. A proper control scheme in wind generating system is used to product active power. It generated power is given to the non- liner load. This non- linear load will produce some distortion in output waveform. Due to this input side also get affected and more losses, more power consumption and equipment get damaged. STATCOM is used to reduce harmonic to improve performance of system. Reference current is taken from output side is compared with input current and is given as input to the PI controller. Its controller output is given to input of STATCOM. An opposite harmonics from STATCOM is injected to line at point of common coupling in order to maintain the unity power factor at the source side. 5. PROPOSED CIRCUIT DIAGRAM: The proposed circuit diagram is as shown in the figure 5.1. The STATCOM absorbs the power from the source and the energy is stored using the battery and also provides reactive power support to the load and wind energy system when necessary, hence a dual power flow is indicated in the figure 5.1.
  • 4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 ISSN 0976 – 6553(Online) Volume 5, Issue Figure 5.1: Proposed circuit diagram 6. SIMULATION ENVIRONMENT Simulation is carried out using MATLAB. The name MATLAB stands for Matrix Laboratory. MATLAB is a software package for high performance numerical computation and visualization. It provides an interactive computation, graphics and animations. The combination of analysis capabilities, flexibility, reliability and powerful graphics makes MATLAB the premier software package for electrical engineers. Best of all, MATLAB provides easy extensibility with its own high level programming language. 7. MODELING OF OVER ALL CIRCUIT SYSTEM Figure: 7.1 shows the complete MATLAB model of The power circuit as well as control Simulink. The grid source is represented by three connected at the load end.STATCOM is connected in shunt and it consists of PWM voltage source inverter circuit and a DC capacitor connected at its DC bus. An IGBT implemented using Universal bridge block from Power Electronics subset of PSB. Fig 7.1:Over All Circuit Diagram in Simulink Snubber circuits are connected in parallel wit STATCOM system is carried out for linear and non modelled using the block three-phase parallel R International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 37 Figure 5.1: Proposed circuit diagram [7] SIMULATION ENVIRONMENT Simulation is carried out using MATLAB. The name MATLAB stands for Matrix Laboratory. MATLAB is a software package for high performance numerical computation and visualization. It provides an interactive environment with hundreds of built-in functions for technical computation, graphics and animations. The combination of analysis capabilities, flexibility, reliability and powerful graphics makes MATLAB the premier software package for electrical Best of all, MATLAB provides easy extensibility with its own high level programming OVER ALL CIRCUIT SYSTEM s the complete MATLAB model of STATCOM along with control circuit. The power circuit as well as control system are modelled using Power System Block set and Simulink. The grid source is represented by three-phase AC source. Three-phase AC loads are connected at the load end.STATCOM is connected in shunt and it consists of PWM voltage source and a DC capacitor connected at its DC bus. An IGBT-based PWM inverter is implemented using Universal bridge block from Power Electronics subset of PSB. Over All Circuit Diagram in Simulink (MATLAB) er circuits are connected in parallel with each IGBT for protection. Simulation of STATCOM system is carried out for linear and non-linear loads. The linear load on the system is phase parallel R-L load connected in delta configuration. The non International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), Simulation is carried out using MATLAB. The name MATLAB stands for Matrix Laboratory. MATLAB is a software package for high performance numerical computation and in functions for technical computation, graphics and animations. The combination of analysis capabilities, flexibility, reliability and powerful graphics makes MATLAB the premier software package for electrical Best of all, MATLAB provides easy extensibility with its own high level programming STATCOM along with control circuit. system are modelled using Power System Block set and phase AC loads are connected at the load end.STATCOM is connected in shunt and it consists of PWM voltage source based PWM inverter is h each IGBT for protection. Simulation of linear loads. The linear load on the system is L load connected in delta configuration. The non-
  • 5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 ISSN 0976 – 6553(Online) Volume 5, Issue linear load on the system is modelled using R and R rectifier. Provision is made to connect loads in parallel so that the effect of sudden load addition and removal is studied. The feeder connected from the three appropriate values of resistive and inductive components. Fig 7.2: MATLAB model of controller block The control scheme is based on injecting the currents into the grid controller. The controller makes the use of a hysteresis current controlled technique. By using such technique, the controller keeps the control system variable between boundaries of hysteresis area and gives correct switching signals for STATCOM operation. The MATLA scheme for generating the switching signals to the STATCOM is shown in the abo 8. SIMULATION RESULTS The hybrid energy generating system is connected with grid having the nonlinear load. The performance of the system is measured by switching the STATCOM at time 0.21 s in the system and how the STATCOM responds to the step change command for increase in additional load at 0.21s is shown in the simulation. When STATCOM controller is made ON, without change in any other load condition parameters, it starts to mitigate for reactive dem dynamic performance is also carried out by step change in a load, when applied at 0.21 s. This additional demand is fulfil by STATCOM compensator. Thus, STATC real power from source. The result of source current, load respectively. While the result of injected current from S Fig 8.1: waveform 3 phase output 0 -60 -40 -20 0 20 40 60 80 IabcinAmpere International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 38 stem is modelled using R and R-C circuits connected at output of the diode rectifier. Provision is made to connect loads in parallel so that the effect of sudden load addition and removal is studied. The feeder connected from the three-phase source to load is modelled using appropriate values of resistive and inductive components. Fig 7.2: MATLAB model of controller block The control scheme is based on injecting the currents into the grid [5] using hysteresis current The controller makes the use of a hysteresis current controlled technique. By using such technique, the controller keeps the control system variable between boundaries of hysteresis area and gives correct switching signals for STATCOM operation. The MATLAB model for control system scheme for generating the switching signals to the STATCOM is shown in the above fig 7.2. The hybrid energy generating system is connected with grid having the nonlinear load. The measured by switching the STATCOM at time 0.21 s in the system and how the STATCOM responds to the step change command for increase in additional load at 0.21s is shown in the simulation. When STATCOM controller is made ON, without change in any other load condition parameters, it starts to mitigate for reactive demand as well as harmonic current. dynamic performance is also carried out by step change in a load, when applied at 0.21 s. This additional demand is fulfil by STATCOM compensator. Thus, STATCOM can regulate the available real power from source. The result of source current, load current are shown in Figure: 8.2 and 8.4 respectively. While the result of injected current from STATCOM are shown in Figure: 8.1 Fig 8.1: waveform 3 phase output current of STATCOM 0.5 1 1.5 2 2.5 3 3.5 4 x10 4Timeinsec STATCOM3-PHASEOUTPUTCURRENT International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), C circuits connected at output of the diode rectifier. Provision is made to connect loads in parallel so that the effect of sudden load addition and is modelled using hysteresis current The controller makes the use of a hysteresis current controlled technique. By using such technique, the controller keeps the control system variable between boundaries of hysteresis area and B model for control system ve fig 7.2. The hybrid energy generating system is connected with grid having the nonlinear load. The measured by switching the STATCOM at time 0.21 s in the system and how the STATCOM responds to the step change command for increase in additional load at 0.21s is shown in the simulation. When STATCOM controller is made ON, without change in any other load and as well as harmonic current. The dynamic performance is also carried out by step change in a load, when applied at 0.21 s. This OM can regulate the available current are shown in Figure: 8.2 and 8.4 TATCOM are shown in Figure: 8.1.
  • 6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 39 Fig 8.2: waveform of source current Fig 8.3: Source Active and reactive power Fig 8.4: Load Current in Amps It is observed that the source current on the grid is affected due to the effects of nonlinear load and wind generator, thus purity of waveform may be lost on both sides in the system. The inverter output voltage under STATCOM operation with load variation is shown in Figure: 8.9 and 8.6. The dynamic load does affect the inverter output voltage. The source current with and without STATCOM operation is shown in Figure: 8.2. This shows that the unity power factor is maintained for the source power when the STATCOM is in operation. Fig 8.5: STATCOM Active and reactive power 0 0.5 1 1.5 2 2.5 3 3.5 4 x10 4 -60 -40 -20 0 20 40 60 Time insec IasinAmpere SourceCurrent 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -2000 0 2000 4000 6000 8000 10000 12000 14000 16000 Time in sec Activepower(W)andReactivepower(VAR) ACTIVE POW ER (W) AND REACTIVE POWER (VAR) DELIVERED BY SOURCE 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -80 -60 -40 -20 0 20 40 60 80 Time in sec LoadcurrentinAmp LOAD CURRENT 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -2000 0 2000 4000 6000 8000 10000 Time in sec Activepower(W)andReactivepower(VAR) ACTIVE POW ER(W) AND REACTIVE POWER(VAR) DELIVERED BY STATCOM
  • 7. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 40 Fig 8.6: STATCOM Output Current Fig 8.7: 3 phase of voltage wind energy system Fig 8.8: 3 phase current of wind energy system The average power flow is measured at the point of common coupling, with and without controller operation in the grid is shown in Figure: 8.3. The controller is operated for power quality mode to inject the power at t = 0.21 s, during this operation source reactive power is reduced to zero. 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -60 -40 -20 0 20 40 60 80 Time in sec outputcurrentinAmps STATCOM OUTPUT CURRENT(Ia1) 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -400 -300 -200 -100 0 100 200 300 400 3 PHASE VOLTAGE OF WIND ENERGY SYSTEM VOLTAGEINVOLTS TIME IN SEC 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -4 -3 -2 -1 0 1 2 3 4 3 PHASE CURRENT OF WIND ENERGY SYSTEM TIME IN SEC CURRENTINAMPS
  • 8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 41 Fig 8.9: STATCOM Output Voltage The average power flow is measured at the point of common coupling, with and without controller operation in the grid. The controller is operated for power quality mode to inject the reactive power at t = 0.21 s, during this operation source reactive power is reduced to zero is shown in Figure:8.5. Fig 8.10: Source Current of without STATCOM and FFT of Source Current without STATCOM The current waveform before and after the STATCOM operation is analyzed. The Fourier analysis of this waveform is expressed and the THD of this source current at PCC without STATCOM is 13.28 %, as shown in Figure: 8.10. Fig 8.11: Source Current of with STATCOM and FFT of Source Current with STATCOM The power quality improvement is observed at point of common coupling, when the controller is in ON condition. The STATCOM is placed in the operation at 0.21 s and source current waveform is shown in Figure: 8.11 with its FFT. It is shown that the THD has been improved considerably and within the norms of the standard. The above tests with proposed scheme has not only power quality improvement feature but it also has sustain capability to support the load with the energy storage through the batteries. 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -1500 -1000 -500 0 500 1000 1500 STATCOM OUTPUT VOLTAGE TIME IN SEC VOLTAGEINVOLTS 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 -50 0 50 Selected signal: 17.5 cycles. FFT window (in red): 2 cycles Time (s) 0 100 200 300 400 500 600 700 800 900 1000 0 0.01 0.02 0.03 0.04 0.05 Frequency (Hz) Fundamental (50Hz) = 55.21 , THD= 0.97% Mag(%ofFundamental) 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 -50 0 50 Selected signal: 17.5 cycles. FFT window (in red): 2 cycles Time (s) 0 100 200 300 400 500 600 700 800 900 1000 0 2 4 6 8 10 12 Frequency (Hz) Fundamental (50Hz) = 49.52 , THD= 15.04% Mag(%ofFundamental)
  • 9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 5, Issue 3, March (2014), pp. 34-42 © IAEME 42 CONCLUSION In this paper we present the FACTS device (STATCOM) -based control scheme for power quality improvement in grid connected wind generating system and with nonlinear load. The power quality issues and its consequences on the consumer and electric utility are presented. The operation of the control system developed for the STATCOM in MATLAB/SIMULINK for maintaining the power quality is to be simulated. It has a capability to cancel out the harmonic parts of the load current. It maintains the source voltage and current in-phase and support the reactive power demand for the wind generator and load at PCC in the grid system, thus it gives an opportunity to enhance the utilization factor of transmission line. Thus the integrated wind generation and FACTS device with BESS have shown the outstanding performance in maintaining the voltage profile as per requirement. Thus the proposed scheme in the grid connected system fulfils the power quality requirements and maintains the grid voltage free from distortion and harmonics. FUTURE ENHANCEMENTS The proposed a STATCOM control scheme for grid connected hybrid wind power energy system to improve power quality is using for conventional control of PI controller which is used to compensate non -linear load and reactive power demand.We can also use fuzzy logic in the controller side which will reduce the settling time and increase the response of the circuit. REFERENCES [1] B. S. Borowy and Z. M. Salameh, (1997), “Dynamic response of a stand-alone wind energy conversion system with battery energy storage to a wind gust,” IEEE Trans. Energy Conversion, vol. 12, no. 1, pp. 73–78, Mar. [2] Francisco Diaz Gonzalez1, Marcela Martnez-Rojas (2011), “Strategies for Reactive Power Control in Wind Farms with STATCOM” IREC Catalonia Institute for Energy Research. [3] J.J.Gutierrez,J.Ruiz, L. A. Leturiondo, and A. Lazkano, (2009) “Flicker Measurement System for Wind Turbine Certification” IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 58, NO. 2, pp.375-382. [4] Kyung soo kook and yiluliu (2006) “Mitigation of the Wind Generation Integration Related Power Quality Issues by Energy Storage” Electrical Power Quality and Utilisation, Journal Vol.XII, No.2, pp.77-82.7. [5] Mukhtiar Singh, VinodKhadkikar, Ambrish Chandra, Rajiv K. Varma (2011), “Grid Interconnection of Renewable Energy Sources at the Distribution Level With Power-Quality Improvement Features” IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 26, NO. 1, pp.307-315. [6] Sharad W. Mohod and Mohan V. Aware (2012) “Micro Wind Power Generator with Battery Energy Storage for Critical Load” IEEE SYSTEMS JOURNAL, VOL. 6, NO.1, pp.118-125. [7] Sharad W. Mohod and Mohan V. Aware (2010), “A STATCOM-Control Scheme for Grid Connected Wind Energy System for Power Quality Improvement” IEEE SYSTEMS JOURNAL, VOL. 4, NO. 3, pp.346-352. [8] S.Dileep Kumar Varma and Divya Dandu, “Modelling and Simulation of Hybrid Renewable Energy Sources Connected to Utility Grid”, International Journal of Electrical Engineering & Technology (IJEET), Volume 4, Issue 5, 2013, pp. 155 - 164, ISSN Print: 0976-6545, ISSN Online: 0976-6553.

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