含异构微源孤岛微电网内虚拟同步发电机预同步控制策略

Pre-synchronization Control Strategy of Virtual Synchronous Generator in Islanded Microgrid with Heterogeneous Distributed Generators

在含异构微源孤岛微电网的弱电网环境下,基于相差控制的虚拟同步发电机(VSG)在预同步过程中会因相角差周期跳变产生频率波动,且锁相环与弱电网的耦合作用会对其产生影响,容易导致VSG失稳,甚至引发系统崩溃。为此,提出一种基于虚拟电流的VSG预同步控制策略。首先,简析相角差跳变机理,揭示其对VSG并网过程的影响;然后,基于虚拟电流改进相角控制器输入变量,消除相角差跳变以提高VSG并网的频率稳定性,实现无锁相环的预同步。在此基础上,建立小信号模型,分析不同参数对预同步过程的影响,并设计合理的控制器参数提高系统的动态性能。最后,MATLAB/Simulink仿真及StarSim硬件在环半实物实验验证了所提策略的有效性。

In the weak power grid environment of the islanded microgrid with heterogeneous distributed generators,the virtual synchronous generator(VSG)based on the phase difference control produces frequency fluctuation due to the periodic jump of the phase angle difference,and the coupling of the phase-locked loop(PLL)and the weak power grid affects it,which easily leads to the instability of VSG and even system collapse.Therefore,a pre-synchronization control strategy of VSG based on the virtual current is proposed.First,the jump mechanism of the phase angle difference is briefly analyzed to reveal its influence on the gridconnection process of VSG.Then,the input variable of the phase angle controller is improved based on the virtual current for eliminating the jump of the phase angle difference,to improve the frequency stability of the grid-connection of VSG and realize the pre-synchronization without PLL.On this basis,a small-signal model is established,and the effects of different parameters on the pre-synchronization process are analyzed,while reasonable controller parameters are designed to improve the dynamic performance of the system.Finally,the simulation on MATLAB/Simulink and the hardware-in-loop experiment on StarSim verify the effectiveness of the proposed strategy.