基于交流电流下垂特性控制的VSC建模和稳定性分析

在直流微电网中,下垂控制常被用来实现直流母线电压的稳定和电压源型换流器(VSC)功率的准确分配,已有的下垂控制特性大多基于直流变量,响应速度慢且结构复杂.为此提出了一种基于交流侧电流的Id-V下垂特性,其与单闭环控制VSC结合,系统结构简单、成本低、响应速度快,可以实现直流母线电压的快速稳定,并设计了自适应下垂系数以实现准确的功率分配.建立了传统I-V下垂控制系统和Id-V下垂控制系统的状态空间平均模型,并基于建立的模型绘制特征根轨迹分析系统的小信号稳定性.通过仿真验证了稳定性分析结果的正确性.仿真结果表明Id-V下垂控制系统能够实现准确的功率分配和直流母线电压的稳定,且响应速度相比传统I-V下垂控制系统更快.

Modeling and stability analysis of VSC with droop characteristic based on AC current

In DC microgrid, droop control can achieve stable DC bus voltage and accurate power distribution of VSCs(Voltage Source Converters). The traditional droop control characteristics are mostly based on DC variables, with slow response speed and complex structure. Therefore, an Id-V droop characteristic based on AC current is proposed, which is combined with single closed-loop controlled VSC to simplify the system structure, reduce the system cost, improve the response speed and rapidly achieve the stable DC bus voltage. Moreover, the adaptive droop gain is designed and adopted to achieve accurate power distribution. The state-space average models of Id-V droop control system and I-V droop control system are established, and on this basis the eigenvalue trajectories are drawn to analyze the small-signal stability of the system. The correctness of stability analysis results is verified by simulation. The results show that, Id-V droop control system can achieve accurate power distribution, and has faster response speed than I-V droop control system.