新型模块化多电平换流器串联电抗器的功能与取值分析

从模块化多电平换流器正常工作状态的功率输出限制、相单元间2倍频环流限制、直流两极短路电流限制、输出交流三相短路电流限制4个方面分析了子模块串联电抗器的功能及相应的数学关系.根据分析结果,给出了模块化多电平串联电抗器的选取原则和计算方法.基于工程实际需要,通常相单元间高频环流可通过控制回路附加抑制环流控制器来有效抑制,而串联电抗器值应根据直流两极短路和输出交流三相短路电流限制要求来计算,最后可根据输出功率的要求进行校验.对一个设计实例进行了分析,给出了串联电抗器值选取的方法,验证它是合理可行的.

Function analysis and parameter selection for series reactor of modular multilevel converter

The functions of the series reactor module of modular multilevel converter is analyzed and its corresponding mathematical relations are given in four aspects,i.e.,output power limit in normal working state,double-frequency circulating current constraint between units,short circuit current limit of DC pole-to-pole fault,short circuit current limit of AC three-phase output fault,based on which,the principle and calculation method of parameter selection are given for the series reactor of modular multilevel converter.In actual engineering,the double-frequency circulating current between units is suppressed by an additional controller and the value of series reactor is calculated according to the short circuit current limits of DC pole-to-pole fault and AC three-phase output fault.The calculated result is verified by the requirement for output power.A design example is given,which shows that the proposed principle and calculation method are simple and practical.