基于改进虚拟同步发电机的多逆变器频率无差控制策略

在采用传统虚拟同步发电机频率恢复控制的离网微电网中,由于纯积分模块的引入和一次调频响应较慢,造成系统功率分配不均和一、二次调频耦合问题。为此提出了一种具有自动开关延时的虚拟同步发电机无差调频控制策略,即用可控的频率积分反馈回路代替传统虚拟同步发电机频率控制回路。通过改进的控制策略,可使微网逆变器根据角速度变化量的不同自动在一、二次调频之间切换,实现微网频率的恢复和功率按比例分配。建立系统的小信号模型,对无差调频控制策略进行稳定性分析,并且给出所提控制策略参数的取值范围。最后,仿真结果表明,所提控制策略可在满足频率无差调节的前提下,自动实现频率调节的一、二次解耦和输出功率按比例分配,有利于提高系统稳定性。

Frequent deviation-free control for microgrid multi-inverters based on improving a virtual synchronous generator

There is a problem of uneven power distribution and primary and secondary coupling caused by the introduction of a pure integral module and the fact that primary FM response is relatively slow in the off-grid microgrid using the frequency recovery control of a traditional virtual synchronous generator. Thus this paper proposes a uniform frequency modulation control strategy for a virtual synchronous generator with automatic switching delay, in which the controllable frequency integral feedback loop is used instead of the traditional frequency control loop. With the improved control strategy, the micro-grid inverter can automatically switch between the primary and secondary frequency modulation according to the angular velocity variation, and the frequency recovery and power distribution of the micro-grid can be realized in proportion. A small signal model of the system is established to analyze the stability of the uniform frequency modulation control strategy and the range of parameters is given. The simulation results show that the proposed control strategy can automatically realize the primary and secondary decoupling and the proportional distribution of output power of the virtual synchronous generator on the premise of frequency adjustment without difference. This is beneficial in improving the stability of the system. This work is supported by the National Key Research and Development Program of China (No. 2019YFB1505400).