基于数学分析的抑制模块化多电平换流器电压波动的子模块电容参数设计

远海风电场经MMC-HVDC联网具有一定的技术优势,子模块是模块化多电平换流器(MMC)的重要组成部分,其参数关系到换流器的安全稳定运行。文中在MMC的稳态数学模型基础上,推导了子模块电容能量波动的关系式,以数学分析的方法证明了换流器工作在静止无功补偿方式时模块电压波动最大,设计了全工况下满足电压波动率要求的子模块电容取值,并指出了考虑风电功率波动的子模块电容取值。仿真以南汇柔性直流输电示范工程为背景,验证了发生直流电压极值时换流器的运行方式,以及所设计的电容参数对换流器工况的适应性。

Sub-module Capacitance Parameter Design of Modular Multilevel Converters to Restrain Voltage FluctuationBase on the Mathematical calculation

The sub-module is an important part of the modular multilevel converter (MMC), its parameters are related to the safety and stable operation of the converter. The values of the sub-module capacitance parameters affect the DC voltage fluctuation of the system. Based on the steady state mathematical model of MMC, the analytical expression of the instantaneous power of the MMC bridge arm is obtained, and the relation expression of the sub-module capacitance energy is derived. By the method of mathematical calculation, this paper proves that the modular voltage is maximized when the converter is working in static var compensation mode, and the converter that can meet the voltage fluctuation rate requirements in the range of capacitance values under all working conditions is designed. The simulation is based on the HVDC Flexible demonstration project in Nanhui. The voltage fluctuation of the converter under different working conditions and the adaptability of the designed capacitance parameters to the converter operating conditions are verified.