ADVANCES in NATURAL and APPLIED SCIENCES

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1 ADVANCES in NATURAL and APPLIED SCIENCES ISSN: Published BYAENSI Publication EISSN: Special 11(6): pages Open Access Journal Mitigation of Harmonics using PV Inverter based Shunt Active Filter 1 M.Sabarimuthu, 2 S.Subhasri, 3 S.Sureshraja, 4 U.Thulasiram, 5 V.Manimegalai 1,2,3,4,5 Department of Electrical and Electronics, Kongu Engineering College, Perundurai Received 28 January 2017; Accepted 22 March 2017; Available online 28 April 2017 Address For Correspondence: M.Sabarimuthu, Department of Electrical and Electronics, Kongu Engineering College, Perundurai subhasrisubramani@gmail.com Copyright 2017 by authors and American-Eurasian Network for ScientificInformation (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). ABSTRACT The present modern power system is getting more complex and dynamic day-by-day. These dynamic changes can be effectively handled by integrating renewable energy sources to the grid. The optimal usage of renewable sources will improve the overall performance of the electrical utility. Renewable energy sources and non-linear loads connected to the grid have adverse effects on the power quality of the system. This paper presents about the Dynamic Active Power Filter(DAPF) to improve the power quality of the grid at source side with effective integration of renewable sources. KEYWORDS: Total Harmonic Distortion(THD), Shunt Active Filter (SAF),Renewable Energy Sources(RES). INTRODUCTION A novel approach to determine reference compensation currents of the three-phase shunt active power filter (APF) under distorted and/or imbalanced source voltages[1]. A model that represents a shunt hybrid active power filters application mainly for current harmonic elimination and fixed reactive power compensation [2]. An optimal control method entitled ant colony PI controller for extracting the reference compensating currents to shunt active power filter under balanced voltage conditions, which is applied to eliminate line current harmonics and compensate reactive power [3]. The description about when the supply voltages are balanced and sinusoidal, load compensation can give both unity power factor and perfect harmonic cancellation (PHC) source currents.but under distorted supply voltages, achieving both UPF & PHC currents are not possible and contradictory to each other[4]. The analysis of a shunt hybrid active power filter consisting of a small rated voltage source active power filter and a series 7th tuned LC passive filter[5]. Now a days, fossil fuel is the main energy supplier of the worldwide economy, but the recognition of it as being a major cause of environmental problems makes the mankind to look for alternative resources in power generation. Moreover, the day-by-day increasing demand for energy can create problems for the power distributors, like grid instability and even outages. The necessity of producing more energy combined with the interest in clean technologies yields in an increased development of power distribution sytems using renewable energy. Integration of renewable energy units to the grid has many effects on the power quality of the system. The injected harmonics in the line are mainly due to nonlinear loads connected. Utility and consumer equipment will be affected by power quality abnormalities. This makes the power quality more important at all levels of usage of electricity. These power quality problems should be addressed so as to provide reliable and quality power, which eliminates these power quality issues while integrating renewable energy units. This project presents a grid interfacing inverter control that compensates power quality problems and interfacing renewable energy source with the grid. The grid interfacing inverter is given with hysteresis current control method to generate gate pulse ToCite ThisArticle: M.Sabarimuthu, S.Subhasri, S.Sureshraja, U.Thulasiram, V.Manimegalai, Mitigation of Harmonics using PV Inverter based Shunt Active Filter. Advances in Natural and Applied Sciences. 11(6); Pages:

2 350 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: and it has the capability to performs (1) Reactive power compensation, (2)Unity power factor, (3)Source current harmonic reduction, (4)Active power supply to the load during grid fluctuations. ISSUES AND CHALLENGES OF RES-GRID INTEGRATION: Integrating more large-capacity RE into the grid brings variability and uncertainty.at the same time, there will continue to be unexpected disturbances stemming from load variation, grid faults and conventional generation outages. Worldwide studies and experience in recent years have shown that new technical solutions are needed to address this conjunction of difficulties. The new solutions will include new technologies, methods and practices, applied in order to provide more flexibility and improve the efficiency of power systems, constantly balancing generation and load. Only this will make the power systems reliable and maintain security of supply, i.e. avoid any interruption in the supply of power. The required power system flexibility can be achieved on the generation side, from both RE generation and conventional generation. It should first be pursued using grid-friendly RE generation. This means mitigating the impacts of RE generation on the power system, enabling it to contribute to system reliability and stability by improving its design and control technologies. However, the amount of flexibility which can be achieved by this approach is limited. Flexibility from conventional generation is currently the major source of power system flexibility, and is generally referred to as generation flexibility. Renewable energy sources are intermittent in nature hence it is therefore a challenging task to integrate renewable energy resources into the power grid. Challenges and issues associated with the grid integration of various renewable energy sources particularly solar photovoltaic and wind energy conversion systems. further these challenges are broadly classified into technical and non-technical and described below. A.Technical Issues: The following are the technical issues are described as 1. Power quality a.harmonics b.frequency and voltage fluctuation 2. Power fluctuation a.small time power fluctuations b.long time or seasonal power fluctuations 3. Storage 4. Protection issues 5. Optimal placement of RES 6. Islanding B.Non-Technical Issues: The following are the non-technical issues are described as 1.Due to scarcity of technical skilled workers. 2.Less availability of transmission line to accommodate RES 3.RES technologies are excluded from the competition which discourages the installation of new power plant for reserve purpose. PROPOSED METHODOLOGY: The topology presents effective integration of renewable energy units to the grid. The solar energy unit (SEU) is used in place of battery to maintain the DC link capacitor voltage and also to supply the active power to the load during power fluctuations. This makes the model to use REUs very effectively.fig. 1 shows the general block diagram of grid integrated REUs. Here battery fed dynamic active power filter is used to improve the power quality. Fig. 2 describes the proposed model, where REUs are integrated to the grid in optimum manner. Fig. 1: Basic block diagram of grid integrated REUs

3 351 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: Fig. 2: Detailed block diagram of proposed system CONTROL STRATEGY: The transient and dynamic performance depends upon firing pulse generation of VSC. Following are some of the most commonly used control strategies Phase Shift Control p-q theory Unit template Method d-q theory Adaline Based Control Algorithm In above methods the unit template is a simple method for reference signal generation. The PI controller is used in voltage control loop and Hysteresis current controller is used for switching pulse generation. The Ua, Ub and Uc are the inphase unit vectors and the Wa, Wb and Wc are the quadrature unit vectors which are computed from instantaneous source voltage. The Isad, Isbd and Iscd are in-phase components of reference current calculated by multiplying in-phase unit vectors, Ua, Ub and Uc with Ismd* while Isaq, Isbq, Iscq are the quadrature component of the reference current calculated by multiplying quadrature unit vectors Wa, Wb and Wc with Ismq*. Step 1: Calculation of amplitude of source voltage Vt=((2/3)(V a 2 + V b 2 + V c 2 )) 1/2 Step2: Calculate the inphase components U a=v a/v t U b=v b/v t U c=v c/v t Step 3: Calculate the quadrature components W a= (-U b/ 3)+(U c/ 3) W b= (( 3*U a)/2) + ((U b-u c)/ 3) W c=((- 3*U a)/2) + ((U b-u c)/ 3) Step 4: Calculate the in-phase component of reference supply current I smd(n)= Ismd(n-1)+K pd{v dcer- Vdcer(n-1)}+K idv dcer(n); I sad = I smdu a; I sbd = I smdu b; I scd = I smdu c; Step 5: Calculate the quadrature component of reference supply current Ismq(n) = I smq(n-1)+k pa{ Ver(n)-V er(n-1)}+k iav er(n);

4 352 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: I saq = I smqw a; I sbq = I smqw b; I scq = I smqw c; Step 6: Calculate the total reference supply current I sa = I saq+i sad; I sb = I sbq+i sbd; I sc = I scq+i scd; HYSTERESIS CURRENT CONTROL: Carrier-less PWM hysteresis current controller is used for generating firing pulse of the gate drive. That is, the current errors are computed as, shown in equation I saerr = I sa*-i sa; I sberr = I sb*-i sb; I scerr = I sc*-i sc; Now the difference between reference and actual currents is fed to hysteresis current controller (HCC). HCC develops the pulses to DAPF based on the difference between reference and actual source currents.hysteresis current controller generates the required firing pulses to the inverter. The SEU fed DAPF injects the currents which cancels the harmonics in source current and compensates the reactive power at CCL. By compensating reactive power, DAPF brings the unity power factor at CCL. It also injects the active power from the SEU. The whole Unit Template algorithm is represented in the form of a block diagram. Fig. 3: Whole unit template algorithm. SIMULATION (WITHOUT FILTER): The following figure 4 shows the simulation diagram without using filter components Fig. 4: Simulation diagram of the system without filter. Three phase supply is given to the non-linear load. Load is connected via uncontrolled bridge rectifier. Various measurement blocks are connected to the system.

5 353 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: Fig. 5: Harmonic distortion of source current. The above graph represents harmonic distortion of source current without filter. The x axis represents time in seconds and y axis represents current in ampere. Fig. 6: Source voltage of each phase. The above graph represents the source voltage of each phase. The x axis represents the time in seconds and y axis represents voltage in volts. Fig. 7: FFT analysis of source current. The above picture represents the Fast Fourier Transform (FFT) of source current and the vertical spikes along the horizontal axis represents the magnitude of harmonics. The x axis represents the various odd harmonic orders. SIMULATION (With Filter): The shunt active power filter has proved to be a useful device to eliminate harmonic currents and to compensate reactive power for nonlinear loads. Due to this, Shunt active filter is introduced in this proposed system. Fig. 8: Simulation diagram of the system with filter.

6 354 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: Fig. 9: Harmonic distortion of source current with filter. The above graph represents the harmonic distortion of source current after inroducing filter components. The x axis represents the time in seconds and the y axis represents the magnitude of current harmonics. Fig. 10: FFT analysis of source current with filter. The above figure shows that the FFT analysis of source current after connecting the filter components. The vertical spikes represent the current harmonic levels and the x axis represents the various odd harmonic orders. Table: Fig17. Result obtained by the system System Current THD in % WITHOUT FILTER % WITH FILTER 4.36% VIII.HARDWARE DETAILS: The components used in the system are 1. Auto Transformer 2. Diode Bridge Rectifier - 60A(TSPR60PB) 3. Power Quality Analyser 4. RL Load 5. Filter Capacitor HARDWARE SETUP: Fig. 12: The entire hardware setup for the proposed system.

7 355 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: This above figure12 shows the entire hardware setup of the proposed system consisting of various measurement devices. The main device used is Power Quality Analyser which is capable of providing phase and line values of current and voltages. And also it is capable of monitoring the power factor and power transferred of real, reactive and apparent power levels. HARDWARE RESULTS: Fig. 13: Phase voltages of each phases of the system. Figure 13 shows the waveform shows the phase voltage variation of each phase. It is monitored with the help of the voltage sensors connected with the Power Quality Analyzer. Fig. 14: Total Harmonic Distortion of phase voltage. The above figure represents the Total Harmonic Distortion (THD) levels of phase voltage. The THD of R phase is 2.6% and Y phase s 2.9% and B phase is 2.4%. Fig. 15: RMS values of Phase current of the system. The above figure represents the RMS values of phase current of the system.the RMS value of R phase is 0.7A andy phase is 0.7A and B phase is 0.7A.

8 356 M.Sabarimuthu et al., 2017/Advances in Natural and Applied Sciences. 11(6) Special 2017, Pages: Fig. 16: THD of phase current of each phases. The above figure represents THD of phase current of each phases. Table: Fig17. Result obtained by the system System Current THD in % WITHOUT FILTER 29.9 % WITH FILTER 2.6% Conclusion: The model presented in this paper efficiently eliminates the harmonics and compensates reactive power demand at CCL. Comparison with other traditional methods proves that Unit template algorithm controlled DAPF effectively reduces %THD of source current to the considerable level. The simulated results prove that the proposed model dynamically performs the following activities: 1. Reactive power compensation at CCL 2. Unity power factor at CCL 3. THD% of source current at CCL are reduced REFERENCES 1. Mack, G.W., and S. Santoso, Understanding power system harmonics, Power Engineering Review, IEEE, 21(11): Akagsi, H., Y. Kanazawa and A. Nabae, Instantaneous reactive power compensators comprising switching devices without energy storage components, IEEE Trans. Ind. Appl., IA-20: Czarnecki, L.S., On some misinterpretations of the instantaneous reactive power theory, IEEE Trans. Power Electron., 19(3): Ghosh, A., and A. Joshi, A new approach to load balancing and power factor correction in power distribution system, IEEE Trans. Power Delivery, 15(1): George, S., and V. Agarwal, A DSP based optimal algorithm for shunt active filter under nonsinusoidal supply and unbalanced load conditions, IEEE Trans. Power Electron., 22(2): Sabarimuthu, M., N. Senthilnathan and T. Manikandan, An Adaptive current control strategy for a three phase shunt active filter IEEE SCEECS 2012 at NIT,Bhopal. 7. Chang, G.W., C.M. Yeh and W.C. Chen, Meeting IEEE-519 current harmonics and power factor constraints with a three-phase three wire active power filter under distorted source voltages. 8. Verdelho, P. and G.D. Marques, An active power filter and unbalanced current compensator control circuit, VI European Conference on Power Electronics and Applications, pp: , Sevilla, Espain. 9. Abinaya, M., N. Senthilnathan, M.Sabarimuthu, Harmonic Compensation as Ancillary Service in PV Inverter based Residential Distribution systems,2014 International Conference on Ciruit,Power and Computing Technologies[ICCPCT] at Noor Islam college of Engineering and Technology,Kanyakumari. 10. Vedat Karslı, M., Mehmet Tümay and Berrin Süslüoğlu, An evaluation of time domain techniques for compensating currents of shunt active power filters, International Conference on Electrical and Electronics Engineering Bursa, Turkey. 11. Sharmila, A., Dr. N. Senthilnathan and M. Sabarimuthu, Mitigation of source current harmonics for wind generating system using STATCOM,International conference on Innovations in Information Embedded and Communication Systems ICIIECS 15.