摘要
混合频率载波调制法可以解决混合级联7电平逆变器的功率环流问题,但其输出电压的谐波特性较差。为此,提出了一种改进的混合频率载波调制策略,该策略使得高压单元运行在单极倍频正弦脉宽调制(sinusoidal pulse width modulation,SPWM)下,从而提高了高压单元的等效开关频率。此外,对高、低压单元的开关策略进行了优化改进,减少了开关次数。相比于改进前的方法,在高压单元开关频率相同时,其等效开关频率可提高1倍,逆变器输出电压的谐波将分布在更高的频段,从而改善了逆变器输出的电能质量,同时消除了功率环流。由仿真结果可知,在相同开关频率下,改进后的方法使得输出电压的较低次谐波由约1 k Hz提高到了约2 k Hz,并且不会出现功率环流现象。研究结果对所提出的改进的混合频率或波调制策略的实用化有一定意义。
The hybrid seven-level inverter can run without power circulation in the presence of the hybrid frequency carrier modulation, however, the harmonic characteristics of its output voltage is not ideal. According to the characteristic of the hybrid seven-level inverter, we propose an improved hybrid frequency carrier modulation strategy, which makes the high voltage cell run in monopole multiplier sinusoidal pulse width modulation(SPWM), and improves the equivalent switching frequency of the high voltage cell. In addition, the switching strategies of the high- and low-voltage cell are optimized in order to reduce the switching times. Compared to the former method, when the switching frequency of the high voltage cell is the same, its equivalent switching frequency can be doubled, and the harmonic of the output voltage will distribute in the higher frequency segment. This method can improve the power quality of the inverter, and eliminate the power circulation simultaneously. The simulation results show that, under the same switching frequency, the improved method makes the lower harmonics of the inverter output voltage from 1 k Hz to 2 k Hz nearby, and the phenomenon of power circulation does not appear. As a result, the method has a certain significance to the practical application of the improved hybrid frequency camer modulation strategy proposed in this paper.
引文
[1]KOURO S,MALINOWSKI M,GOPAKUMAR K,et al.Recent advances andindustrial applications of multilevel converters[J].IEEE Transactions on Industrial Electronics,2010,57(8):2553-2580.
[2]宋平岗,吴继珍,邹欢.电网电压不平衡时模块化多电平换流器直接功率补偿控制策略[J].高电压技术,2016,42(7):2184-2192.SONG Pinggang,WU Jizhen,ZOU Huan.Direct power compensation control strategy for modular multilevel converter under unbalanced grid voltage conditions[J].High Voltage Engineering,2016,42(7):2184-2192.
[3]高志刚,金晓锋.背靠背级联H桥型四象限五电平变换器[J].高电压技术,2016,42(1):79-84.GAO Zhigang,JIN Xiaofeng.Research on a back-to-back cascaded h-bridge four-quadrant five-level converter[J].High Voltage Engineering,2016,42(1):79-84.
[4]李宁宁,王建赜,纪延超,等.基于改进比例控制的STATCOM/BESS直流侧功率动态分配方法[J].高电压技术,2016,42(1):112-120.LI Ningning,WANG Jianze,JI Yanchao,et al.Dynamic allocation method of dc side power based on improved ratio control for STATCOM/BESS[J].High Voltage Engineering,2016,42(1):112-120.
[5]常非,王一,梅红明,等.35 k V直挂式角接链式STATCOM控制策略[J].高电压技术,2016,42(1):121-127.CHANG Fei,WANG Yi,MEI Hongming,et al.Control strategies of35 k V transformerless delta connection chain STATCOM[J].High Voltage Engineering,2016,42(1):121-127.
[6]MANJREKAR M D,LIPO T A.A hybrid multilevel inverter topology fordrive applications[C]∥Applied Power Electronics Conference and Exposition.Anaheim,Canada:[s.n.],1998:523-529.
[7]RECH C,PINHEIRO J R.Hybrid multilevel converters:Unified analysis and design consider ations[J].IEEE Transactions on Industrial Electronics,2007,54(2):1092-1104.
[8]耿俊利,梁晖,金渊.基于SVPWM调制的混合级联七电平逆变器优化控制策略[J].电网技术,2015,39(2):327-333.GENG Junli,LIANG Hui,JIN Yuan.A space vector pulse width modulation based optimization control strategy for hybrid cascaded 7-level inverter[J].Power System Technology,2015,39(2):327-333.
[9]孙醒涛.混合不对称多电平逆变器拓扑及控制策略的研究[D].哈尔滨:哈尔滨工业大学,2009.SUN Xingtao.Research on topologies and control strategies of hybrid asymmetric multilevel inverter[D].Harbin,China:Harbin Institute of Technology,2009.
[10]FARID K,SOUMIA L,KHOUDIR M,et al.Hybrid cascaded H-bridge multilevel-inverter induction motor drive direct torque control for automotive applications[J].IEEE Transactions on Industrial Electronics,2010,57(3):892-899.
[11]费万民,吕征宇,姚文熙.混合级联多电平变换器SHEPWM方法的仿真[J].电力系统自动化,2003,27(17):40-44.FEI Wanmin,LüZhengyu,YAO Wenxi.Research of SHEPWM technique for hybrid cascade multilevel converters[J].Automation of Electric Power Systems,2003,27(17):40-44.
[12]王学华,阮新波,王蓓蓓,等.阶梯波合成Ⅱ型混合级联多电平逆变器的功率均衡策略[J].电工技术学报,2009,24(2):78-84.WANG Xuehua,RUAN Xinbo,WANG Beibei,et al.Power balance strategy for staircase waveform synthesis of II-type hybrid cascaded multi-level inverter[J].Transactions of China Electrotechnical Society,2009,24(2):78-84.
[13]李宋,叶满园.混合级联多电平逆变器混合频率载波调制技术[J].高电压技术,2015,41(7):2378-2383.LI Song,YE Manyuan.Hybrid frequency carrier modulation technique for hybrid cascade multi-level inverter[J].High Voltage Engineering,2015,41(7):2378-2383.
[14]王毅,石新春,朱凌,等.基于混合频率载波调制的多电平PWM控制策略研究[J].中国电机工程学报,2004,24(11):188-192.WANG Yi,SHI Xinchun,ZHU Ling,et al.Research on the hybrid frequency carrier-based multilevel PWM control strategy[J].Proceedings of the CSEE,2004,24(11):188-192.
[15]何凯益,陈轶涵,龚春英.混合级联式中频逆变器控制策略[J].南京航空航天大学学报,2014,46(1):78-85.HE Kaiyi,CHEN Yihan,GONG Chunying.Control strategy of hybrid cascade inverter with medium frequency[J].Journal of Nanjing University of Aeronautics and Astronautics.2014,46(1):78-85.
[16]KANG D W,LEE Y H,SUH B S,et al.An improved carrierwave-based SVPWM method using phase voltage redundancies for generalized cascaded multilevel inverter topology[C]∥Proceedings of IEEE Applied Power Electronics Conference and Exposition.[S.l.]:IEEE,2000:542-548.
[17]李和明,王毅,石新春,等.混合级联型多电平变频器拓扑结构研究[J].中国电机工程学报,2006,26(2):127-132.LI Heming,WANG Yi,SHI Xinchun,et al.Research on the topology of hybrid cascaded multilevel converters[J].Proceedings of the CSEE,2006,26(2):127-132.
