A Novel Zero Sequence Injection Scheme for Three-Level NPC Converters Considering Neutral-Point Potential Balance
Chen Xi1, Huang Shenghua1,2, Li Bingzhang1, Wu Fang1
1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan 430074 China; 2. Wenhua College Huazhong University of Science and Technology Wuhan 430074 China
Abstract:An in-depth comparison of two methods (SVPWM and VSVPWM) for the three-level converter is presented in this paper, and the disadvantages are analyzed such as high dv/dt of the line- to-line voltage, high harmonic contents, high power device switching losses, and slow neutral-point voltage-balancing dynamics of VSVPWM. In order to overcome the drawbacks of the two methods, a novel zero sequence injection carrier-based modulation scheme is proposed. Firstly, a zero sequence injection method for the two-level converter is introduced into a small hexagon of the simplified three-level space vector diagram, then the relationship between the neutral-point current and the zero sequence component is studied mathematically in each small hexagon. In addition, combined with the signs of switching functions in six small hexagons, the carrier-based modulation and the potential balancing control can be achieved with only one carrier wave and six expressions. The proposed method has the advantages of small calculation amount, short execution time and fast voltage-balancing dynamics. Finally, a comparison among three kinds of strategy (the proposed method, SVPWM, and VSVPWM) is presented, which verifies the feasibility and validity of the proposed method.
[1] 冯思硕, 王金花, 杨欢, 等. 混合钳位式三电平逆变器新型调制策略研究[J]. 电工技术学报, 2016, 31(13): 46-54. Feng Sishuo, Wang Jinhua, Yang Huan, et al.Research on a novel modulation strategy of the hybrid clamped three-level inverter[J]. Transactions of China Electrotechnical Society, 2016, 31(13): 46-54. [2] Lee J S, Lee K B.Time-offset injection method for neutral-point AC ripple voltage reduction in a three-level inverter[J]. IEEE Transactions on Power Electronics, 2016, 31(3): 1931-1941. [3] 王付胜, 李祯, 付航, 等. 一种抑制系统漏电流非隔离型三电平逆变器中点平衡载波调制算法[J]. 电工技术学报, 2017, 32(增刊2): 128-138. Wang Fusheng, Li Zhen, Fu Hang, et al.A new pulse-width modulation algorithm for the com- prehensive neutral-point balancing and leakage current reducing in the three-level transformerless inverter[J]. Transactions of China Electrotechnical Society, 2017, 32(S2): 128-138. [4] 耿乙文, 许家斌, 王亮, 等. 基于空间电压矢量120°解耦的开绕组异步电机双三电平逆变器零序电压消除[J]. 电工技术学报, 2017, 32(3): 184-193. Geng Yiwen, Xu Jiabin, Wang Liang, et al.Elimination of zero-sequence voltage in dual three- level inverter fed open-end winding induction motor based on 120°decoupled space-vector PWM strategy[J]. Transactions of China Electrotechnical Society, 2017, 32(3): 184-193. [5] Zaragoza J, Pou J, Ceballos S, et al.A comprehensive study of a hybrid modulation technique for the neutral-point-clamped converter[J]. IEEE Transactions on Industrial Electronics, 2009, 56(2): 294-304. [6] Zaragoza J, Pou J, Ceballos S, et al.Voltage-balance compensator for a carrier-based modulation in the neutral-point-clamped converter[J]. IEEE Transactions on Industrial Electronics, 2009, 56(2): 305-314. [7] Busquets-Monge S, Ortega J D, Bordonau J, et al.Closed-loop control of a three-phase neutral-point- clamped inverter using an optimized virtual-vector- based pulse width modulation[J]. IEEE Transactions on Industrial Electronics, 2008, 55(5): 2061-2071. [8] Welchko B A, Correa M B R, Lipo T A. A three-level MOSFET inverter for low-voltage drives[J]. IEEE Transactions on Industrial Electronics, 2004, 51(3): 669-674. [9] Teichmann R, Bernet S.A comparison of three-level converters versus two-level converters for low- voltage drives, traction, and utility applications[J]. IEEE Transactions on Industry Applications, 2005, 41(3): 855-865. [10] Rodriguez J, Bernet S, Steimer P K, et al.A survey on neutral-point-clamped inverters[J]. IEEE Transa- ctions on Industrial Electronics, 2010, 57(7): 2219-2230. [11] Seo J H, Choi C H, Hyun D S.A new simplified space-vector PWM method for three-level inverters[J]. IEEE Transactions on Power Electronics, 2001, 16(4): 545-550. [12] Busquets-Monge S, Bordonau J, Boroyevich D, et al.The nearest three virtual space vector PWM-a modulation for the comprehensive neutral-point balancing in the three-level NPC inverter[J]. IEEE Power Electronics Letters, 2004, 2(1): 11-15. [13] Pou J, Zaragoza J, Rodríguez P, et al.Fast-processing modulation strategy for the neutral-point-clamped converter with total elimination of low-frequency voltage oscillations in the neutral point[J]. IEEE Transactions on Industrial Electronics, 2007, 54(4): 2288-2294. [14] Maheshwari R, Munk-Nielsen S, Busquets-Monge S.Design of neutral-point voltage controller of a three- level NPC inverter with small DC-link capacitors[J]. IEEE Transactions on Industrial Electronics, 2013, 60(5): 1861-1871. [15] 李宁, 王跃, 王兆安. 基于新型矢量选择表的电压型三电平中性点钳位整流器直接功率控制策略[J]. 电工技术学报, 2016, 31(8): 76-89. Li Ning, Wang Yue, Wang Zhaoan.Direct power control strategy based on novel switching table applied in three-level neutral point clamped voltage source rectifier[J]. Transactions of China Electro- technical Society, 2016, 31(8): 76-89. [16] Choi U M, Blaabjerg F, Lee K B.Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral- point-clamped inverters[J]. IEEE Transactions on Industry Applications, 2015, 51(2): 1678-1691. [17] Ye Zongbin, Xu Yiming, Wu Xiang, et al.A simplified PWM strategy for a neutral-point-clamped (NPC) three-level converter with unbalanced DC links[J]. IEEE Transactions on Power Electronics, 2016, 31(4): 3227-3238. [18] 戴鹏, 石祥龙, 朱晓莹, 等. 有源钳位三电平变频器改进SVPWM策略[J]. 电工技术学报, 2017, 32(14): 137-145. Dai Peng, Shi Xianglong, Zhu Xiaoying, et al.Improved SVPWM strategies for active neutral point clamped converters[J]. Transactions of China Electro- technical Society, 2017, 32(14): 137-145. [19] 胡存刚, 王群京, 李国丽, 等. 基于虚拟空间矢量的三电平NPC变换器中点电压平衡控制方法[J]. 电工技术学报, 2009, 24(5): 100-107. Hu Cungang, Wang Qunjing, Li Guoli, et al.A neutral-point potential balancing algorithm for three-level inverter based on virtual-space-vector[J]. Transactions of China Electrotechnical Society, 2009, 24(5): 100-107. [20] 张志, 谢运祥, 乐江源, 等. 消除中点低频振荡的三电平逆变器空间矢量脉宽调制方法[J]. 电工技术学报, 2011, 26(3): 103-109. Zhang Zhi, Xie Yunxiang, Le Jiangyuan, et al.SVPWM method of removing the low-frequency oscillations of neutral point voltage for three-level NPC inverter[J]. Transactions of China Electro- technical Society, 2011, 26(3): 103-109. [21] 桂石翁, 吴芳, 万山明, 等. 变虚拟空间矢量的三电平NPC变换器中点电位平衡控制策略[J]. 中国电机工程学报, 2015, 35(19): 5013-5021. Gui Shiweng, Wu Fang, Wan Shanming, et al.A strategy for considering neutral-point potential balance for three-level NPC inverters with the varied virtual space vector[J]. Proceedings of the CSEE, 2015, 35(19): 5013-5021. [22] 姜卫东, 赵德勇, 胡杨, 等. 基于载波实现的二极管钳位型三电平逆变器虚拟空间矢量脉宽调制方法[J]. 电工技术学报, 2016, 31(12): 153-160. Jiang Weidong, Zhao Deyong, Hu Yang, et al.Carrier-based virtual space vector pulse width modulation for diode clamped three-level inverter[J]. Transactions of China Electrotechnical Society, 2016, 31(12): 153-160. [23] Celanovic N, Boroyevich D.A comprehensive study of neutral-point voltage balancing problem in three- level neutral-point-clamped voltage source PWM inverters[J]. IEEE Transactions on Power Electronics, 2000, 15(2): 242-249. [24] 尹靖元, 金新民, 杨捷, 等. 开绕组电机驱动用双三电平逆变器的共模电压差抑制[J]. 电工技术学报, 2016, 31(15): 178-186. Yin Jingyuan, Jin Xinmin, Yang Jie, et al.The differential common mode voltage elimination of dual three-level converter for open-end winding motor drives[J]. Transactions of China Electro- technical Society, 2016, 31(15): 178-186. [25] 胡存刚, 胡军, 陈权, 等. 基于特定谐波消除PWM的三电平有源中点钳位逆变器共模电压抑制方法[J]. 电工技术学报, 2016, 31(16): 93-102. Hu Cungang, Hu Jun, Chen Quan, et al.Suppression method of common-mode voltage for three-level active neutral-point-clamped inverter based on selective harmonics elimination PWM[J]. Transa- ctions of China Electrotechnical Society, 2016, 31(16): 93-102. [26] Jiang Yanmin, Wu Weimin, He Yuanbin, et al.New passive filter design method for overvoltage suppression and bearing currents mitigation in a long cable based PWM inverter-fed motor drive system[J]. IEEE Transactions on Power Electronics, 2017, 32(10): 7882-7893. [27] 汪波, 罗毅飞, 张烁, 等. IGBT极限功耗与失效机理分析[J]. 电工技术学报, 2016, 31(12): 135-141. Wang Bo, Luo Yifei, Zhang Shuo, et al.Analysis of limiting power dissipation and thermal failure mechanism[J]. Transactions of China Electro- technical Society, 2016, 31(12): 135-141. [28] 胡存刚, 马大俊, 王群京, 等. 三电平有源中点钳位逆变器损耗分布平衡控制策略[J]. 电工技术学报, 2017, 32(1): 129-138. Hu Cungang, Ma Dajun, Wang Qunjing, et al.Control strategy of loss distribution balancing for three-level active neutral-point-clamped inverter[J]. Transactions of China Electrotechnical Society, 2017, 32(1): 129-138.