功率双向流动时背靠背变流器稳定性分析

背靠背变流器作为区域电网互联的关键器件,其自身稳定性是保证电网间稳定运行的重要前提。文章主要从变流器直流端阻抗的角度研究了功率双向流动时背靠背变流器稳定性问题,分析显示背靠背变流器直流端在功率正向传输的稳定性劣于功率反向运行。针对功率双向运行对系统产生的稳定问题,提出在逆变器中引入直流电流内环控制从而对逆变器直流/交流端阻抗进行重塑校正,使得直流端输入阻抗由原本在低频段的负阻抗变为感性阻抗特性,从而提高了背靠背变流器运行的稳定裕度。最后,在Matlab/Simulink仿真平台建立背靠背变流器系统进行仿真验证,结果验证了理论分析及所提控制方案的可行性。

Stability Analysis of Back-To-Back Converter with Bidirectional Power Flow

As the key component of regional power grid interconnection, the stability of back-to-back converters is an important prerequisite to ensure the stable operation of regional power grids. In this paper, the stability of back-to-back converter with bidirectional power flow is studied mainly from the perspective of the DC terminal impedance of the converter. The results show that the stability of the back-to-back converter is better when power reverses. To alleviate the stability problem of the back-to-back converter caused by bidirectional power flow, the DC current inner loop is introduced into the inverter to reshape the AC/DC impedance of the inverter, which makes the DC terminal input impedance change from the original negative impedance in the low frequency band to the inductive impedance characteristics, so as to improve the stability margin of the back-to-back converter. Finally, the model of back-to-back converter is established in the Matlab/Simulink simulation platform for simulation verification, and the results verify the feasibility of the theoretical analysis and the proposed control scheme.