Abstract：Three-phase six-switch three-level photovoltaic inverter is investigated in this paper. First, the circuit operation principle is analyzed. And then the system common mode loop model is established. The system common mode behavior is investigated. The new modulation strategy is proposed to achieve both the three-level output voltage and constant common mode voltage, so as to eliminate the leakage current. In addition, the issue regarding the inductor winding current is discussed and solved with the improved strategy. Finally, the experiments are carried out on the digital control platform with TMS320F28335 DSP and XC3S400 FPGA. The experimental results verify the effectiveness of the proposed solution.
[1] Yang B, Li W H, Gu Y J, et al.Improved transformerless inverter with common-mode leakage current elimination for a photovoltaic grid-connected power system[J]. IEEE Transactions on Power Electronics, 2012, 27(2): 752-762. [2] 杨晓光, 姜龙斌, 冯俊博, 等. 一种新型高效无变压器型单相光伏逆变器[J]. 电工技术学报, 2015, 30(8): 97-103. Yang Xiaoguang, Jiang Longbin, Feng Junbo, et al.A new high efficiency transformerless single-phase photovoltaic inverter[J]. Transactions of China Electrotechnical Society, 2015, 30(8): 97-103. [3] 郭小强, 贺冉, 菅佳敏, 等. 非隔离型三相四桥臂光伏逆变器漏电流抑制研究[J]. 电工技术学报, 2016, 31(19): 66-73. Guo Xiaoqiang, He Ran, Jian Jiamin, et al.Leakage current reduction for three-phase four-leg photo- voltaic inverter[J]. Transactions of China Electro- technical Society, 2016, 31(19): 66-73. [4] Hernandez J, Vidal P G, Medina A.Characterization of the insulation and leakage currents of PV generators: relevance for human safety[J]. Renewable Energy, 2010, 35(3): 593-601. [5] Li W, Gu Y, Luo H, et al.Topology review and derivation methodology of single phase transfor- merless photovoltaic inverters for leakage current suppression[J]. IEEE Transactions on Industrial Electronics, 2015, 62(7): 4537-4551. [6] 张犁, 孙凯, 冯兰兰, 等. 一种低漏电流六开关非隔离全桥光伏并网逆变器[J]. 中国电机工程学报, 2012, 32(15): 1-7. Zhang Li, Sun Kai, Feng Lanlan, et al.H6 non-isolated full bridge grid-connected PV inverters with low leakage currents[J]. Proceedings of the CSEE, 2012, 32(15): 1-7. [7] 张兴, 孙龙林, 许颇, 等. 单相非隔离型光伏并网系统中共模电流抑制的研究[J]. 太阳能学报, 2009(9): 1202-1208. Zhang Xing, Sun Longlin, Xu Po, et al.Study on common-mode current suppression of single-phase non-isolated photovoltaic system[J]. Acta Energiae Solaris Sinica, 2009(9): 1202-1208. [8] 胡存刚, 姚培, 张云雷, 等. 高效非隔离单相并网MOSFET逆变器拓扑及控制策略[J]. 电工技术学报, 2016, 31(13): 82-91. Hu Cungang, Yao Pei, Zhang Yunlei, et al.Topology and control strategy for high-efficient non-isolated single-phase grid-connected MOSFET inverter[J]. Transactions of China Electrotechnical Society, 2016, 31(13): 82-91. [9] Chua K, Lim Y, Taylor P, et al.Energy storage system for mitigating voltage unbalance on low-voltage networks with photovoltaic systems[J]. IEEE Transa- ctions on Power Delivery, 2012, 27(4): 1783-1790. [10] Alam M, Muttaqi K, Sutanto D, A three-phase power flow approach for integrated 3-wire MV and 4-wire multi grounded LV networks with rooftop solar PV[J]. IEEE Transactions on Power Systems, 2013, 28(2): 1728-1737. [11] Cavalcanti M C, Kleber C de Oliveira, Alexandre M De Farias. Modulation techniques to eliminate leakage currents in transformerless three-phase photovoltaic systems[J]. IEEE Transactions on Industrial Electronics, 2010, 57(4): 1360-1368. [12] Hou C C, Shih C C, Cheng P T, et al.Common-mode voltage reduction pulsewidth modulation techniques for three-phase grid connected converters[J]. IEEE Transactions on Power Electronics, 2013, 28(4): 1971-1979. [13] Guo X, Xu D, Wu B.Three-phase seven switch inverter with common mode voltage reduction for transformerless photovoltaic system[C]//40th Annual Conference of the IEEE Industrial Electronics Society, Texas, USA, 2014: 2279-2284. [14] Guo X, Xu D, Wu B.Three-phase DC-bypass topologies with reduced leakage current for transfor- merless PV systems[C]//IEEE Energy Conversion Congress and Exposition, Pittsburg, USA, 2015: 43-46. [15] Franquelo L G, Rodriguez J, Leon J I, et al.The age of multilevel converters arrives[J]. IEEE Industrial Electronics Magazine, 2008, 2(2): 28-39. [16] Rodriguez J, Franquelo L G, Kouro S, et al.Multilevel converters: an enabling technology for high-power applications[J]. Proceedings of the IEEE, 2009, 97(11): 1786-1817. [17] Kouro S, Malinowski M, Gopakumar K, et al.Recent advances and industrial applications of multilevel converters[J]. IEEE Transactions on Industrial Electronics, 2010, 57(8): 2553-2580. [18] Malinowski M, Gopakumar K, Rodriguez J, et al.A survey on cascaded multilevel inverters[J]. IEEE Transactions on Industrial Electronics, 2010, 57(7): 2197-2206. [19] Leon J I, Kouro S, Franquelo L G, et al.The essential role and the continuous evolution of modulation techni- ques for voltage-source inverters in the past, present, and future power electronics[J]. IEEE Transactions on Industrial Electronics, 2016, 63(5): 2688-2701. [20] Kerekes T, Teodorescu R, Liserre M, et al.Evaluation of three-phase transformerless photo- voltaic inverter topologies[J]. IEEE Transactions on Power Electronics, 2009, 24(9): 2201-2211.
2018, Vol. 33 
