Abstract A typical micro-grid control strategy is generally feed-forward decoupling constant power(PQ) control based on equilibrium assumption. Through the power analysis on the micro-grid control strategy and analysis of grid-connected inverter output performance using switching function, it could come to the conclusion that the output of the inverter consists of third harmonic and negative sequence components based on the control strategy of equilibrium assumption under the condition of voltage unbalance on the grid. In order to improve the performance, a feed-forward negative sequence voltage control loop is used to superimpose on the original PQ control structure, achieving the purpose of offsetting voltage negative sequence component in the grid and maintaining three-phase balance. Also, the system could suppress the output of the third harmonic through the improved switching function modulation method. The simulation and experiment results indicate that the improved micro-grid unbalanced PQ control strategy may improve the survival capacity of micro-grid under asymmetrical grid voltage.
Yi Guiping. Micro-grid Constant Power Control Strategy Analysis under Grid Voltage Imbalance[J]. Transactions of China Electrotechnical Society, 2015, 30(14): 377-387.
[1] Eto J, Lasseter R, Schenkman B, et al. Overview of the CERTS microgrid laboratory test bed[C]. Integration of Wide-Scale Renewable Resources Into the Power Delivery System, 2009 CIGRE/IEEE PES Joint Sym- posium. 2009: 1-1. [2] Lasseter B. Microgrids. IEEE Power Engineering Society Winter Meeting[C]. New York, USA, 2001, 1: 146-149. [3] Lasseter R, Abbas A, Marnay C, et al. Integration of distributed energy resources: The CERTS MicroGrid concept[R]. California Energy Commission, 2003. [4] LOPES J A P. Kythnos 2008 symposium on micro- grids: operational control of microgrids and multi- microgrid[J]. 2008-06-02]. http://der.lbl.gov/new_site/ DER. htm. [5] KATIRAEI F, IRAVANI MR. Power management strategies for a microgrid with multiple distributed generation units[J]. Power Systems, IEEE Transactions on, 2006, 21(4): 1821-1831. [6] Piagi P, Lasseter R H. Autonomous control of Micro Grids[C]. IEEE Power Engineering Society General Meeting, Montreal, 2006, p 1708993. [7] Guerrero J M, Matas J, De-Vicuna L G, et al. Wireless- control strategy for parallel operation of distributed- generation inverters[J].IEEE Transactions on Industrial Electronics, 2006, 53(5): 1461-1470. [8] Guerrero J, Matas J, de Vicuna L G, et al. Decen- tralized control for parallel operation of distributed generation inverters using resistive output impedance. IEEE Transactions on Industrial Electronics, 2007, 54(2): 994-1004. [9] 彭力, 白丹, 康勇, 等．三相逆变器不平衡抑制研究[J]. 中国电机工程学报, 2004, 24(5): 174-178. Peng Li, Bai Dan, Kang Yong, et al. Research on three-phase inverter with unbalanced load[J]. Procee- dings of the CSEE.2004, 24(5): 174-178. [10] Prodanovic M, Green T C, et al. High-Quality Power Generation Through Distributed Control of a Power Park Microgrid. IEEE Transaction on Industrial Electronics, 2006, 53(5): 1471-1482. [11] Blazic B, Papic I. STATCOM Control for Operation with Unbalanced Voltages[C]. Power Electronics and Motion Control Conference, 2006, EPE-PEMC 2006. 12th International, Portoroz, Slovenia, 2006: 1454- 1459. [12] Li Kuang, Liu Jinjun, Wang Zhaoan, et al. Static Var generator control strategy for unbalanced systems in medium voltage applications[C]. Proceedings of the IEEE International Conference PESC’2004, Yachen, Germany, 2004: 4257-4262. [13] Chen W L, Hsu Y Y. Direct output voltage control of a static synchronous compensator using current sensorless d-q vector-based power balancing scheme [J]. IEEE Transactions on Power Delivery, 2003, 2(7-12): 545-549. [14] Bina M T, Eskandari M D. Consequence of unbalance supplying condition on a distribution static com- pensation[C]. IEEE Power Electronics Specialists Conference, Aachen, Germany, 2004. [15] 涂春鸣, 李慧, 唐杰, 罗安. 电网电压不对称对D-STATCOM的影响分析及抑制[J]. 电工技术学报, 2009, 24(8): 114-121. Tu Chunming, Li Hui, Tang Jie, Luo An. Analysis and Suppression of Influence on D-STATCOM Under Unbalanced Voltage of Power System[J]. Transactions of China Electrotechnical Society, 2009, 24(8): 114- 121. [16] Bostjan Blazic, Igor Papic. Improved D-Statcom control for operation with unbalanced currents and voltages. IEEE Transactions on Power Delivery, 2006, 21(1): 225-233. [17] 丁洪发, 段献忠, 何仰赞. 同步检测法的改进及其在三相不对称无功补偿中的应用[J].中国电机工程学报, 2000, 20(6): 17-20. Ding Hongfa, Duan Xianzhong, He Yangzan. Improve- ment of synchronous detection method and applica- tion for VAR compensation of unbalanced three-phase system[J]. Proceedings of the CSEE, 2000, 20(6): 17-20. [18] Shuangjian Peng, An Luo, Zhipeng Lv, Jingbing Wu. Power control for single-phase microgrid based on the PQ theory. ICIEA 2011: IEEE Conference on Industrial Electronics and Applications, Beijing, 2011. [19] Weiss G, Zhong Q Ch, Green T C, Liang J. Repetitive control of DC-AC converters in micro-grids. IEEE Transactions on Power Electronics, 2004, 19(1): 219-230.
2015, Vol. 30 
