考虑内部动态约束的MMC功率运行区间的确定及控制方法

Determination and control method on power operating area of modular multi-level converter considering the constraint of internal dynamics

为了正确评估模块化多电平换流器(modular multilevel converter,MMC)的内部动态约束对运行区间的影响,提出一种通过求解MMC状态空间方程来获取MMC内部动态进而确定其功率运行区间的功率扫描方法。建立基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)系统的稳态模型,通过求解状态方程得出各功率点对应的状态变量;提出一种系统非正弦周期电气量极值的计算方法求解各内部动态约束的幅值;通过逐点扫描得到满足MMC内部动态约束和常规约束时的功率运行区间。针对功率设置可能越限的情况,设计保证系统满足内部动态约束的边界控制策略。在PSCAD/EMTDC中进行仿真,仿真结果验证了MMC功率运行区间确定方法的正确性及边界控制策略的有效性。

This paper proposed a point-scanning method to obtain the internal dynamics of modular multilevel converter(MMC)and determine its operating area by solving the state-space equations.A steady-state model of modular multilevel converter based high voltage direct current(MMC-HVDC)system was developed,and the corresponding state variables of each power point were obtained by solving the state equations.A method to calculate the extreme value of non-sinusoidal periodic quantities was proposed to solve the amplitude of internal dynamics constraints.The power operating area of MMC was obtained when the internal dynamic constraints and the conventional constraints were considered by the point-scanning method.Based on the analysis results,a boundary control strategy was designed to ensure that the system satisfied the internal dynamic constraints.Simulation results in PSCAD/EMTDC verified the correctness of the MMC power operating area determination method and validity of the boundary control strategy.