一种面向实时仿真的两电平VSC建模方法

A Two-level VSC Modeling Method for Real-time Simulation

新能源通过两电平电压源型换流器(voltage source converter,VSC)接入电网前,需要对其数字控制器做硬件在环测试,这要求实时仿真器能够对VSC做采样频率及以下频带的准确建模。为解决电力电子开关动作频繁改变系统拓扑造成的仿真效率下降问题,该文使用传输线建模法将交流侧电感等效成短传输线,将换流器从系统中隔离出来,从而使开关操作引起的系统拓扑变化限制在节点数较少的(VSC)子系统中。然后用延时受控电压源等效直流电容,进一步降低了VSC子网的计算量。最终,系统被分成多个可并行计算的子网系统。仿真结果表明,提出的实时仿真模型计算精度远高于目前常用的LC小步长建模方法,模型的频率特性满足仿真需要。

The hardware-in-loop test for the digital controller is necessary, before the new energy source is connected to the power grid by means of two-level voltage source converter(VSC). It is requested that the real-time simulator could model the VSC converter accurately within a wide frequency band, from 0 Hz to the sampling frequency of the digital controller. In order to improve the simulation efficiency, this paper used the transmission line modeling method to model the AC inductors, and isolate the converter from the system. And the DC capacitors could be modeled by delay controlled voltage source, which could also reduce the simulation time-cost. As a result, the system was split into several sub-networks and could be calculated in parallel. Compared with the commonly used LC small-step modeling method, the proposed method gives a more accurately simulation result, which could meet the wide frequency band modeling request.