Instability Mechanism and Control Measures of Reactive Compensation in Islanded Microgrid Based on Droop Control

doi:10.11985/2020.01.004

Abstract

Abstract:

For the line economical operation and lower transmission loss requirements, on the part of reactive compensation of islanded microgrid, resonance problems among droop control inverter and the reactive compensation capacitor are studied. Firstly, output impedance of droop control inverter is obtained by small signal method, it is disclosed that droop control inverter especially Q-U control factor is mainly factor, which would affect the output impedance value at lower frequency band. Then, the stability of islanded microgrid is analyzed by impedance-based specifications when reactive power capacitors are emulated for reactive power compensation. It is shown that the grid is unstable if the reactive power capacitor is existed for reactive compensation. Finally, harmonic suppression method based on capacitor current feedforward control at current inner loop is proposed, which reshapes the output impedance of droop control inverter, and a 3 kW droop control inverter is designed for verified the effectiveness of the output impedance model and harmonics damping mothed.

Key words: Reactive compensation based on reactive power capacitor, droop control, islanded microgrid, impedance-based specifications, harmonic suppression

CLC Number:

TM561

SHI Yunjie,FENG Xiayun,WANG Fei,ZHANG Lijun,LI Yufei. Instability Mechanism and Control Measures of Reactive Compensation in Islanded Microgrid Based on Droop Control[J]. Journal of Electrical Engineering, 2020, 15(1): 29-35.

Figures/Tables 10

References 26

[1]	Guerrero J M, Hang L, Uceda J . Control of distributed uninterruptible power supply systems[J]. IEEE Transactions on Industrial Electronics, 2008,55(8):2845-2859. doi: 10.1109/TIE.2008.924173
[2]	Haddadi A, Yazdani A, Joos G , et al. A gain-scheduled decoupling control strategy for enhanced transient perfor- mance and stability of an islanded active distribution network[J]. IEEE Transactions on Power Delivery, 2014,29(2):560-569. doi: 10.1109/TPWRD.2013.2278376
[3]	Guo X, Lu Z, Wang B , et al. Dynamic phasors-based modeling and stability analysis of droop-controlled inverters for microgrid applications[J]. IEEE Transactions on Smart Grid, 2014,5(6):2980-2987. doi: 10.1109/TSG.2014.2331280
[4]	Guerrero J M, GarciadeVicuna L, Matas J , et al. A wireless controller to enhance dynamic performance of parallel inverters in distributed generation systems[J]. IEEE Transactions on Power Electronics, 2004,19(5):1205-1213. doi: 10.1109/TPEL.2004.833451
[5]	Guerrero J M, Vasquez J C, Matas J , et al. Control strategy for flexible microgrid based on parallel line- interactive UPS systems[J]. IEEE Transactions on Industrial Electronics, 2009,56(3):726-736. doi: 10.1109/TIE.2008.2009274
[6]	Zhong Q . Robust droop controller for accurate propor- tional load sharing among inverters operated in parallel[J]. IEEE Transactions on Industrial Electronics, 2013,60(4):1281-1290. doi: 10.1109/TIE.2011.2146221
[7]	Li Y W, Kao C . An accurate power control strategy for power-electronics-interfaced distributed generation units operating in a low-voltage multibus microgrid[J]. IEEE Transactions on Power Electronics, 2009,24(12):2977-2988. doi: 10.1109/TPEL.2009.2022828
[8]	He J, Li Y W, Guerrero J M , et al. An islanding microgrid power sharing approach using enhanced virtual impedance control scheme[J]. IEEE Transactions on Power Electronics, 2013,28(11):5272-5282. doi: 10.1109/TPEL.2013.2243757
[9]	中华人民共和国电力工业部. 供电营业规则[J]. 电力标准化与计量, 1997(2):2-16.
	Ministry of Electric Power Industry of the People's Republic of China. Power supply business rules[J]. Electric Power Standardization & Measurement, 1997(2):2-16.
[10]	Xue Y, Zhang X . Reactive power and AC voltage control of LCC HVDC system with controllable capacitors[J]. IEEE Transactions on Power Systems, 2017,32(1):753-764. doi: 10.1109/TPWRS.59
[11]	Kekatos V, Wang G, Conejo A J , et al. Stochastic reactive power management in microgrids with renewables[J]. IEEE Transactions on Power Systems, 2015,30(6):3386-3395. doi: 10.1109/TPWRS.2014.2369452
[12]	Prasai A, Divan D M . Control of dynamic capacitor[J]. IEEE Transactions on Industry Applications, 2011,47(1):161-168. doi: 10.1109/TIA.2010.2090318
[13]	Lu C, Hsu C, Juang C . Coordinated control of flexible AC transmission system devices using an evolutionary fuzzy lead-lag controller with advanced continuous ant colony optimization[J]. IEEE Transactions on Power Systems, 2013,28(1):385-392. doi: 10.1109/TPWRS.2012.2206410
[14]	Das S, Chatterjee D, Goswami S K . A GSA-based modified SVC switching scheme for load balancing and source power factor improvement[J]. IEEE Transactions on Power Delivery, 2016,31(5):2072-2082. doi: 10.1109/TPWRD.2015.2502623
[15]	Chen Y, Guerrero J M, Shuai Z , et al. Fast reactive power sharing,circulating current and resonance suppression for parallel inverters using resistive-capacitive output impe- dance[J]. IEEE Transactions on Power Electronics, 2016,31(8):5524-5537. doi: 10.1109/TPEL.2015.2493103
[16]	Padiyar K R, SaiKumar H V . Investigations on strong resonance in multimachine power systems with STATCOM supplementary modulation controller[J]. IEEE Transactions on Power Systems, 2006,21(2):754-762. doi: 10.1109/TPWRS.2006.873405
[17]	Padiyar K R, Prabhu N . Design and performance evaluation of subsynchronous damping controller with STATCOM[J]. IEEE Transactions on Power Delivery, 2006,21(3):1398-1405. doi: 10.1109/TPWRD.2005.861332
[18]	胡伟, 孙建军, 姜一鸣 , 等. 含STATCOM的孤岛微电网低频稳定性分析[J]. 中国电机工程学报, 2015,35(10):2454-2462. doi: 10.13334/j.0258-8013.pcsee.2015.10.011
	Hu Wei, Sun Jianjun, Jiang Yiming , et al. Low frequency stabilization analysis of isolated microgrid with STATCOM[J]. Proceedings of the CSEE, 2015,35(10):2454-2462. doi: 10.13334/j.0258-8013.pcsee.2015.10.011
[19]	Jachim H, Karl-Heinz W . Multi-inverter UPS system with redundant load sharing control[J]. IEEE Transactions on Industrial Electronics, 1990,37(6):506-513. doi: 10.1109/41.103455
[20]	吴恒, 阮新波, 杨东升 , 等. 虚拟同步发电机功率环的建模与参数设计[J]. 中国电机工程学报, 2015,35(24):6508-6518. doi: 10.13334/j.0258-8013.pcsee.2015.24.027
	Wu Heng, Ruan Xinbo, Yang Dongsheng , et al. Modeling of the power loop and parameter design of virtual synchro- nous generators[J]. Proceedings of the CSEE, 2015,35(24):6508-6518. doi: 10.13334/j.0258-8013.pcsee.2015.24.027
[21]	Guerrero J M, Vasquez J C, Matas J , et al. Control strategy for flexible microgrid based on parallel line- interactive UPS systems[J]. IEEE Transactions on Industrial Electronics, 2009,56(3):726-736. doi: 10.1109/TIE.2008.2009274
[22]	李建林, 徐少华, 惠东 . 百MW级储能电站用PCS多机并联稳定性分析及其控制策略综述[J]. 中国电机工程学报, 2016,36(15):4034-4047.
	Li Jianlin, Xu Shaohua, Hui Dong . A review of stability analysis and control strategy of multi-parallel PCS for hundred MW level energy storage power station[J]. Proceedings of the CSEE, 2016,36(15):4034-4047.
[23]	Beres R N, Wang X, Liserre M , et al. A review of passive power filters for three-phase grid-connected voltage- source converters[J]. IEEE Journal of Emerging and Selected Topics in Power Electronics, 2016,4(1):54-69. doi: 10.1109/JESTPE.2015.2507203
[24]	Wang X, Blaabjerg F, Loh P C . Passivity-based stability analysis and damping injection for multiparalleled VSCs with LCL filters[J]. IEEE Transactions on Power Electronics, 2017,32(11):8922-8935. doi: 10.1109/TPEL.2017.2651948
[25]	Li Y W . Control and resonance damping of voltage- source and current-source converters with LC filters[J]. IEEE Transactions on Industrial Electronics, 2009,56(5):1511-1521. doi: 10.1109/TIE.2008.2009562
[26]	He J, Li Y W, Wang R , et al. Analysis and mitigation of resonance propagation in grid-connected and islanding microgrids[J]. IEEE Transactions on Energy Conversion, 2015,30(1):70-81. doi: 10.1109/TEC.2014.2332497

项目	参数	数值
LC滤波器	C_f/μF	3×10^–6
	L_f/mH	2
	R_f/Ω	0.02
线路阻抗	X_Li/mΩ	314
线路阻抗	R_Li/mΩ	1
负载	R_Load/Ω	25
负载	L_Load/H	0.152
直流母线电压	U_dc/V	400
开关频率	f_s/kHz	10
电压电流环控制	k_ip	0.8
	k_ii/s^–1	150
	k_up	8.3×10^–3
	k_ui/s^–1	25
下垂控制	ω_iref/(rad/s)	314
	E_iref/V	110
	n	0.01
	m	0.01