基于无源性理论的MMC电容电压观测器设计
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摘要
模块化多电平变换器(modular multilevel converters,MMC)因其结构上的诸多优点适用于高压大功率工况。在应用中,电容电压的控制一直是MMC控制的重点,测量电容电压对于系统的安全运行很有必要。随着电压和功率等级的升高,桥臂子模块和传感器数量增加,使系统复杂性提高,成本增加。为了减少传感器数量,根据无源性理论和持续充分激励条件设计MMC降维观测器,通过测量MMC的桥臂电流和桥臂级联子模块总电压,结合模块开关信号,对每个子模块电容电压进行估计,将观测器得到的电容电压估计值用于MMC系统设计,并在Simulink中进行仿真验证。仿真结果表明观测器具有良好的鲁棒性和准确性。
Because of its advantages in structure, modular multilevel converter(MMC) is suitable for high voltage and high power systems. In applications, control of the capacitor voltages is fundamental concern in terms of MMC. Capacitor voltages are necessary for proper control and safe operation of MMC. However, with increase of voltage and power level, the number of cascaded modules increases, and it is necessary to increase the number of voltage sensors, thus resulting in cost increase and hardware complexity. To reduce the number of sensors, a reduced-order observer based on passivity theory and condition of persistent and sufficient excitation was proposed. Capacitor voltages were estimated with gating signals, measurements of arm current and observation errors of total cascaded sub-module voltage. Then, the estimated results of the observer were used to the MMC controller design. Simulation results verify robustness and accuracy of the proposed observer.
Because of its advantages in structure, modular multilevel converter(MMC) is suitable for high voltage and high power systems. In applications, control of the capacitor voltages is fundamental concern in terms of MMC. Capacitor voltages are necessary for proper control and safe operation of MMC. However, with increase of voltage and power level, the number of cascaded modules increases, and it is necessary to increase the number of voltage sensors, thus resulting in cost increase and hardware complexity. To reduce the number of sensors, a reduced-order observer based on passivity theory and condition of persistent and sufficient excitation was proposed. Capacitor voltages were estimated with gating signals, measurements of arm current and observation errors of total cascaded sub-module voltage. Then, the estimated results of the observer were used to the MMC controller design. Simulation results verify robustness and accuracy of the proposed observer.
引文
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[2]王姗姗,周孝信,汤广福,等.模块化多电平HVDC输电系统子模块电容值的选取和计算[J].电网技术,2011,35(1):26-32.Wang Shanshan,Zhou Xiaoxin,Tang Guangfu,et al.Selection and calculation for sub-module capacitance in modular multi-level converter HVDC power transmission system[J].Power System Technology,2011,35(1):26-32(in Chinese).
[3]Hiller M,Krug D,Sommer R,et al.A new highly modular medium voltage converter topology for industrial drive applications[C]//13th European Conference on Power Electronics and Applications.Barcelona,Spain:IEEE,2009:1-10.
[4]Du S X,Liu J J.A study on DC voltage control for chopper-cellbased modular multilevel converters in D-STATCOM application[J].IEEE Transactions on Power Delivery,2013,28(4):2030-2038.
[5]刘天琪,陶艳,李保宏.风电场经MMC-MTDC系统并网的几个关键问题[J].电网技术,2017,41(1):3251-3260.Liu Tianqi,Tao Yan,Li Baohong.Critical problems of wind farm integration via MMC-MTDC system[J].Power System Technology,2017,41(1):3251-3260(in Chinese).
[6]Amal A,Khalifa A,Abdul R.Sliding mode observer of submodular capacitor voltages in modular multilevel converter[C]//2015International Workshop on Recent Advances in Sliding Modes(RASM).Istanbul,Turkey:IEEE,2015:1-6.
[7]Hagiwara M,Nishimura K,Akagi H.A medium-voltage motor drive with a modular multilevel PWM inverter[J].IEEE Transactions on Power Electronics,2010,25(7):1786-1799.
[8]王奎.无变压器多电平变换器拓扑及控制算法研究[D].北京:清华大学,2011.
[9]王奎,郑泽东,李永东.新型模块化多电平变换器电容电压波动规律及抑制方法[J].电工技术学报,2011,26(5):8-14.Wang Kui,Zheng Zedong,Li Yongdong.Voltage ripple principle and restrain method of floating capacitors in a new modular multilevel converter[J].Transactions of China Electrotechnical Society,2011,26(5):8-14(in Chinese).
[10]雷鸣,李耀华,葛琼璇,等.模块化多电平变流器低频控制方法[J].中国电机工程学报,2013,33(24):59-65,10.Lei Ming,Li Yaohua,Ge Qiongxuan,et al.A control scheme of modular multilevel converter operating at low frequency[J].Proceedings of the CSEE,2013,33(24):59-65,10(in Chinese).
[11]常乾坤,葛琼璇,雷鸣,等.模块化多电平变流器低频调速系统控制方法[J].电力系统自动化,2014,38(10):120-125.Chang Qiankun,Ge Qiongxuan,Lei Ming,et al.A low-frequency control scheme for modular multilevel converter motor drive[J].Automation of Electric Power Systems,2014,38(10):120-125(in Chinese).
[12]于洋,葛琼璇,雷鸣,等.一种模块化多电平变流器的变频控制策略[J].电网技术,2016,40(9):2780-2788.Yu Yang,Ge Qiongxuan,Lei Ming,et al.A control strategy of modular multilevel converter for variable frequency operation[J].Power System Technology,2016,40(9):2780-2788(in Chinese).
[13]殷实,谭国俊,方磊,等.模块化多电平变流器调速系统变频控制[J].电工技术学报,2016,31(20):139-150.Yin Shi,Tan Guojun,Fang Lei,et al.Variable-frequency control strategy of modular multilevel converter[J].Transactions of China Electrotechnical Society,2016,31(20):139-150(in Chinese).
[14]刘波峰,贺锐智,黄守道.低频工况下MMC电容电压波动抑制研究[J].控制工程,2017,24(8):1553-1558.Liu Bofeng,He Ruizhi,Huang Shoudao.Study of capacitor voltage suppression for MMC at low frequency[J].Control Engineering of China,2017,24(8):1553-1558(in Chinese).
[15]于洋,葛琼璇,雷鸣,等.模块化多电平变流器的低频控制策略[J].高电压技术,2017,43(4):1160-1167.Yu Yang,Ge Qiongxuan,Lei Ming,et al.Low-frequency control scheme of modular multilevel converter[J].High Voltage Engineering,2017,43(4):1160-1167(in Chinese).
[16]Akagi H.New trends in medium-voltage power converters and motor drives[C]//2011 IEEE International Symposium on Industrial Electronics.Gdansk,Poland:IEEE,2011:5-14.
[17]Hagiwara M,Maeda R,Akagi H.Control and analysis of the modular multilevel cascade converter based on double-star chopper-cells[J].IEEE Transactions on Power Electronics,2011,26(6):1649-1658.
[18]Almasabi S,Nguyen N,Mitra J.Control of a multilevel modular converter using a state observer[C]//Annual IEEE India Conference.New Delhi,India:IEEE,2015:1-5.
[19]Hui Liu,Ke Ma,Poh Chiang Loh,et al.Design of state observer for modular multilevel converter[C]//Power Electronics for Distributed Generation Systems(PEDG).Aachen,Germany:IEEE,2015:1-6.
[20]Luc-AndréGrégoire,Weihua Wang,Seleme Isaac Seleme,et al.High reliability observers for modular multilevel converter capacitor voltage evaluation[C]//2016 IEEE 8th International Power Electronics and Motion Control Conference(IPEMC-ECCE Asia).Hefei,China:IEEE,2016:2332-2336.
[21]Salvatore D,Jon A S.Estimation of sub-module capacitor voltages in modular multilevel converters[C]//2013 15th European Conference on Power Electronics and Applications.Lille,France:IEEE,2013:1-10.
[22]Haghnazari S,Zolghadri M.A novel voltage measurement technique for modular multilevel converter capacitors[C]//IECON 2015-41st Annual Conference of the IEEE.Yokohama,Japan:IEEE,2015:238-243.
[23]Picas R,Zaragoza J,Pou J,et al.New measuring technique for reducing the number of voltage sensors in modular multilevel converters[J].IEEE Transactions on Power Electronics,2016,31(1):177-187.
[24]Morgan A P,Narendra K S.Asymptotic stability of nonautonomous equations and the adaptive observer[C]//1976 IEEE Conference on Decision and Control including the 15th Symposium on Adaptive Processes.Clearwater,USA:IEEE,1976:1228-1230.