total harmonic distortion (thd) analysis of grid ...paper.ijcsns.org/07_book/201812/20181231.pdf ·...

IJCSNS International Journal of Computer Science and Network Security, VOL.18 No.12, December 2018

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Manuscript received December 5, 2018 Manuscript revised December 20, 2018

Total Harmonic Distortion (THD) Analysis of Grid Integrated Permanent Magnet Synchronous Generator (PMSG) With Full

Scale Converter (FSC) Based Wind Farm

Shafqat Hussain Memon1, Mahendar Kumar2, Abdul Hakeem Memon3, Zubair Ahmed Memon4, Shakir Ali Soomro5

1,5Department of Electrical Engineering, Mehran University (SZAB) Campus Khairpur Mir’s Sindh Pakistan

2,3,4Department of Electrical Engineering, Mehran University of Engineering Technology Jamshoro Sindh Pakistan

Abstract Recent development in the wind energy technology, wind energy generation has been emerged as the fastest growing technology and most clean energy source to produce electrical power in Pakistan as well as across the world. Several topologies (i.e. induction machine, double fed induction machine and synchronous machine) with different configurations based on advanced power electronic converters are commercially available for modern wind turbines. Among different wind turbine topologies, permanent magnet synchronous generator (PMSG) with full scale converter (FSC) based wind turbine is preferred due to its advantages of maximum power extraction, variable wind speed operation and to support grid even during disturbance (i.e. fault condition) but it generates harmonic problems due to nonlinear characteristics of its converter and non linear loads connected from grid side. The other challenging task in grid connected wind farms is fault detection. Hence in this work, the total harmonic distortion analysis of wind farm (using synchronous generator full scale converter based) integrated with grid is carried out using Fast Fourier Transform (FFT) analysis to evaluate the Total Harmonic Distortion (THD) of output current at different fault conditions with help of MATLAB / SIMULINK software, also to classify faults and analyze harmonics to maintain continuity and quality of power. Key words: Total Harmonic Distortion (THD), Fast Fourier Transform (FFT). Permanent Magnet Synchronous Generator (PMSG), Electrical Faults.

1. Introduction

Renewable energy resources has created a great importance due to increase in pollution levels and exhaustion combustible fuels [1-8]. Among the sources of renewable energy, wind energy, solar power generation has been emerged as the fastest growth technology and one of the convenient and clean energy to produce electrical power [2]. Due to the recent development in the wind energy technology, grid integrated wind generation is increasing across the world on a large scale [3]. Progress in large electronics converters for power system are also playing

vital role in improving reliability and controllability of wind turbines [4]. Nowadays, several topologies are commercially available for modern wind turbines based on induction machine, double fed induction machine and synchronous machine with control of advanced electronic converters. The modern wind generators are designed not only to produce power but also provide support to grid at any type fault .Due to this, the wind turbines with full scale converters are preferred because power converters completely decouple wind turbines from switchyard or grid station contingencies and therefore it provides grid support as well [5]. Also, the integration of wind energy conversion system with distribution network is increased. Hence, the distribution generation has got so much familiarity and attraction because of less distribution losses, low generation prices and improved power quality and stability. As well distributed generation, the role of distribution network is changed with respect to conventional distribution network. Traditional distributed network primarily used for delivering electrical power to consumers whereas, nowadays, the distribution networks are used for collection of electrical power from different distributed generation. The system transient stability affected during different type of faults cause the disturbance in voltage and current [11] , similarly the total harmonic distortion THD also disturbed during different faults. The distributed generations are much advantageous despite this; it generates and enhances the harmonics (THD) level in the distribution network, due to the involvement of AC/DC/AC convertor in permanent magnet synchronous generator (PMSG) based wind turbine to sweep maximum amount of power. In addition to this, the usage non linear loads is increasing rapidly in distributed network [6], which are also responsible current harmonic distortion due to which power quality will be suffered and compromised. Hence, such problems associated with these systems need to studied , analyzed as well mitigation techniques.


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2. Wind energy conversion system based on PMSG with full scale converter.

The modern wind energy conversion systems around the world are employing PMSGs because of its efficiency and stability. This wind farm is based on PMSG based integrated with distribution grid with AC/DC/AC converter as shown in Figure.1. The machine side of full scale converter is used to provide generator torque and speed control whereas grid side is used to fulfill reactive power requirement and supply constant dc voltage to the grid [7].

Fig. 1 PMSG based wind turbine

3. Control of AC-DC-AC Converter.

An electronics converter is mainly used to extract the maximum possible amount of power from the generator. In the absence of this, it is very much crucial to deliver the power into the power transmission or distribution system due to the power quality problems specifically voltage and the frequency issues. The main problem with converter is that it generates harmonic problems due to its non-linear characteristics. Harmonics or THD generation depends on the number of switching pulses. The harmonic components can be defined with following mathematical relation as [7].

h= a.p ± 1 Here, h= harmonics order. a= integer (such as 1, 2, 3,4,5…n) and p= pulse per cycle.

4. Description of Model / Test System

The simulation model / test system consists of 10MW wind farm integrated with 120kV grid. Five 05 wind turbines each of having capacity of 2MW, is connected to 120kV distribution system. It delivers power to 120KV grid through 30km, 25kV feeder as shown in one line diagram Figure2. A wind turbine uses a detailed model of Synchronous Generator and Full Scale Converter.

Fig. 2 Single line diagram of 10MW wind farm integrated with 120 KV Grid

The simulation model developed in MATLAB, given single line diagram in figure 2 for test system simulated and total harmonic distortion analysis THD measured in Fast Fourier Transform FFT window under different fault conditions (i.e. single line to ground, double line to ground and triple line to ground) by injecting different fault for limited period of time ,as the transient stability of power system studied under different fault conditions [11].


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5. Simulation Results & Discussions

Fig. 3 Simulation Model (MATLAB) of 10MW wind farm integrated with 120 KV Grid.

Figure 3 shows simulation model developed in MATLAB Software for 10MW wind farm integrated with 120 KV Grid. In which Total Harmonic Distortion THD analysis carried out, voltage and current measured during no fault condition and after occurrence of different type of faults. As THD at no fault condition is very low with fault changes the THD increased.

5.1 Total Harmonic Distortion (THD), Voltage and current during no fault condition

In this case system is normal, no any fault applied and following are the simulation results of output voltage and output current at wind farm shown in Figure. 4 and Figure. 5 respectively at no fault condition.

Fig. 4 Output voltage at no fault

Fig.5 Output current at no fault

5.1.1 THD Analysis in FFT Window during no fault condition

At no fault condition THD Analysis in FFT window of output current at wind farm is presented in Figure. 6 and Figure. 7.

Fig. 6 Output current

Fig. 7 FFT analysis of output current

It is also observed from current and voltage waveforms, even at no fault condition, there is harmonic distortion in current waveform due to nonlinear characteristics of converter employed by wind generator and nonlinear loads. There is 12.23 % total harmonic distortion in output current waveform observed by FFT analysis as shown in Figure.7.

5.2 Total Harmonic Distortion (THD), Voltage and current during single line to ground fault

In this case a single line to ground fault is applied / injected for limited period of time, voltage drops and current distortion THD increase, as shown in simulation results of output voltage and output current at wind farm shown in Figure 8 and Figure 9 respectively.


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Fig. 8 Output voltage at SLG fault

Fig. 9 Output current at SLG fault

5.2.1 THD Analysis in FFT Window during single line to ground fault

At single line to ground fault THD Analysis in FFT window of output current at wind farm is presented in Figure.10 and Figure.11. It is also observed from FFT analysis of current waveform, total harmonic distortion increases upto 12.89% as shown in Figure11 as compared 12.48 % THD at no load condition.



5.3 Total Harmonic Distortion (THD), Voltage and current during double line to ground fault

In this case a double line to ground fault is injected for limited period of time, voltage drops and current distortion increase as shown in simulation results of output voltage and output current at wind farm shown in Figure 12 and Figure13 respectively.

Fig. 12 Output voltage at DLG fault

Fig. 13 Output current at DLG fault

5.3.1 THD Analysis in FFT Window during double line to ground fault

At double line to ground fault condition ,THD Analysis in FFT window of output current at wind farm is presented in Figure.14 and Figure.15 .



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5.4 THD Analysis during triple line to ground fault

In this case triple line to ground fault condition applied and following are the simulation results of output voltage and output current at wind farm shown in Figure. 16 and Figure.17 respectively at triple line to ground fault condition.

Fig. 16 Output voltage at TLG fault

Fig. 17 Output Current at TLG fault

5.4.1 THD Analysis in FFT Window during triple line to ground fault

At triple line to ground fault condition THD analysis in FFT window of output current at wind farm is presented in

Figure.18 and Figure.19. As observed from the THD Analysis , current THD increases as the fault severity increase as occurred during triple line to ground fault.


Fig. 19 FFT analysis of output current.

Table.1 Total Harmonic Distortion (THD) in output current during different system conditions.

S.No System Condition Total Harmonic Distortion (THD) in output current

1 No fault condition 12.23% 2 Single line to ground

fault condition 12.89%

3 Double line to ground fault condition 13.67%

4. Triple line to ground fault condition 14.64%

Summarized in Table.1 , Total Harmonic Distortion (THD) in output current increases with fault level. High THD affects the power capacity , cause overheating of equipment, unnecessary tripping and may damage the equipment, harmful to their useful life [8,9]. Total Harmonic Distortion THD could be reduced less than 5% IEEE recommended values with the help power quality improvement devices like passive filters [15], multipulse transformers, multipulse converters [16], hybrid active power filter [10,12,13,14].

6. Conclusion

In this work, simulink model of permanent magnet synchronous generator (PMSG) with full scale based (FSC) wind farm integrated with grid is presented. In the wind farm connected to the grid, detection of fault current is a challenging task so classification of different faults is necessary. Thus, the methodology is presented in this study for total harmonics distortion (THD) analysis of output current for different faults with help of Fast Fourier Transform FFT function in MATLAB. In this way, it is easy to evaluate total harmonic distortion THD level which


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would help to distinguish and classify different fault. Such harmonic analysis methodology will also help in understanding harmonic problems, selection and implementation harmonic mitigation devices like D-Statcom, passive filters, active power filters, hybrid active power filters.

Acknowledgement

The authors would like to pay a word of gratitude to Mehran University of Engineering & Technology authority for extending their support and facilities. Cooperation of the Institute of Information & Communication Technology IICT and Department of Electrical Engineering MUET, Jamshoro has made publishing of this article possible. References [1] Bubshait, A. S.; Mortezaei, A.; Simões, M. G.; and Busarello,

T. D. C. (2017). Power quality enhancement for a grid connected wind turbine energy system. IEEE Transactions on Industry Applications,53(3), 2495-2505.

[2] Gatavi, E.; Hellany, A.; Nagrial, M.; and Rizk, J. (2016,October). Low voltage ride-through enhancement in DFIG-based wind turbine. IEEE Electrical Power and Energy Conference (EPEC),Ottawa, ON, Canada (1-6).

[3] Shafqat H.Memon.;Zubair A. Memon.; M. Aslam Uqaili.; and Shan-E-Farooq,2018. Voltage Stability and Reactive Power Compensation of 132kv Grid Integrated 50MW Wind Farm Using Statcom. J. Appl. Environ. Biol. Sci., 8(1)232-240.

[4] Singh, M., Khadkikar, V. and Chandra, A., 2011. Grid synchronisation with harmonics and reactive power compensation capability of a permanent magnet synchronous generator-based variable speed wind energy conversion system. IET Power Electronics, 4(1), pp.122-130

[5] Baroudi, J.A., Dinavahi, V. and Knight, A.M., 2007. A review of power converter topologies for wind generators. Renewable energy, 32(14), pp.2369-2385.

[6] Das, A. and Roy, N.K., 2017, December. Reduction of harmonics distortion and voltage sag of PMSG based wind energy systems connected to distribution networks. In Humanitarian Technology Conference (R10-HTC), 2017 IEEE Region 10 (pp. 333-336). IEEE.

[7] Arani, M.F.M. and Mohamed, Y.A.R.I., 2016. Assessment and enhancement of a full-scale PMSG-based wind power generator performance under faults. IEEE Transactions on Energy Conversion, 31(2), pp.728-739.

[8] [8] Kumar, M., Memon, Z. A., Uqaili, M. A., & Baloch, M. H. (2018). An Overview of Uninterruptible Power Supply System with Total Harmonic Analysis & Mitigation: An Experimental Investigation for Renewable Energy Applications. INTERNATIONAL JOURNAL OF COMPUTER SCIENCE AND NETWORK SECURITY, 18(6), 25-36.

[9] Kumar, M., Memon, Z. A., Uqaili, M. A., & Baloch, M. H. (2018). An Experimental Insulation Testing Investigation of 210 MW Generator: A Case of Thermal Power Station Jamshoro. International Journal of Energy Optimization and Engineering (IJEOE), 7(4), 68-91.

[10] Memon, Z. A., Uqaili, M. A., & Unar, M. A. (2016). Design of Three-Phase Hybrid Active Power Filter for Compensating the Harmonic Currents of Three-Phase System. arXiv preprint arXiv:1604.03223.

[11] Bhellar, E., Hashmani, A. A., & Kumar, M. (2018). TRANSIENT STABILITY ANALYSIS OF THERMAL POWER PLANT JAMSHORO CONNECTED WITH INFINITE BUS BAR SYSTEM.

[12] Memon, Z. A., Uquaili, M. A., & Unar, M. A. (2016). Harmonics mitigation of industrial power system using passive filters. arXiv preprint arXiv:1605.06684.

[13] Memon, Z. A., Uqaili, M. A., & Unar, M. A. (2012). Estimation of compensation current reference using fuzzy logic controller for three-phase hybrid active power filter. International Journal of Computer Applications, 43(11), 16-21.

[14] Memon, Z. A., Uqaili, M. A., & Soomro, M. A. (2011). Experimental Analysis of Harmonic Mitigation Effects on Three Phase Six Pulse Converter by Using Shunt Passive Filter. Mehran University Research Journal of Engineering and Technology, 30(4), 653-656.

[15] Mansoor Ahmed Soomro, Muhammad Aslam Uqaili and Zubair Ahmed Memon, “A Novel Method of the Current Harmonic Elimination of Industrial Power System Using single Tuned Shunt Passive Filter,” Mehran University Research Journal of Engineering & Technology,Vol.31, No.1, January, 2012, pp.101-106.

[16] Zubair Ahmed Memon, Muhammad Aslam Uqaili and Mansoor Ahmed Soomro, “Experimental Analysis of Harmonic Mitigation Effects on Three-phase Six-Pulse Converter by Using Shunt Passive Filters,” Mehran University Research Journal of Engineering & Technology,Vol.30, No.4, October, 2011, pp.653-656.

Shafqat Hussain Memon received the B.E. in electrical engineering and M.E in electrical power engineering from the MUET, Jamshoro, Sindh, in 2016 and 2018 respectively. He is currently working as Lab Engineer with the Mehran University of Engineering and Technology, SZAB Campus Khairpur Mir’s, Sindh. Research Interests include renewable energy sources and its integration with grid with power

quality, stability and control aspects.

Mahendar Kumar received the B.E and M.E degrees in Electrical Engineering from MUET Jamshoro in 2009 and 2013, respectively. Research Interest: Power Quality, Power Electronics, Power System Analysis, Power System Stability and Power Generation.


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Abdul Hakeem Memon received the B.E. and M.E. degrees in electrical engineering from the MUET, Jamshoro, Sindh, in 2009 and 2013, respectively, and the Ph.D. degree from the Nanjing University of Science and Technology, Jiangsu, China, in 2018. In 2009, he joined the MUET as a Lecturer, where he is currently an Assistant Professor. Research Interests include, power electronic converters, control engineering, and electric

machine design.

Zubair Ahmed Memon received the B.E., M.E., and Ph.D. degrees in Electrical Engineering from the MUET, Jamshoro, Sindh, Pakistan ,in 1991, 2005, and 2012, respectively. He is currently a Professor Department of Electrical Engineering and the Director of IICT, MUET Jamshoro. Research Interests include Power Quality, renewable energy sources, power electronic

converters, and control engineering.

Shakir Ali Soomro, received B.E in Electrical Engineering from MUET Jamshoro in year 2004. In Karachi Electric Supply Company (KESC) worked as Engineer and Manager also in 2012. M.E(Electrical Power) in 2007,from NED University UET, Karachi.. At Present he is working at Mehran UET,SZAB khairpur Mir's campus as Assistant Professor

Electrical Engineering Department.

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