不平衡电压下的MMC控制策略研究

模块化多电平变流器MMC(modular multilevel converter)在高压直流输电领域有着众多优势,在未来传输新能源电能有着重要作用。在不平衡电压下,基于交流有功功率的分析,设计了基于正、负序控制的电流控制器,消除有功功率二倍基频波动。同时,MMC桥臂环流包含正、负、零三序分量,传统环流控制器(CCSC)仅考虑了负序分量,因而并不适用不平衡电压。在瞬时功率理论分析的基础上,提出并设计了一种基于直接控制环流正、负、零三序分量的环流控制器。通过Matlab/Simulink仿真平台,与传统二倍频负序旋转坐标变换的环流控制器对比,验证了所提出控制器的有效性。

Study on Control Strategy of MMC Under Unbalanced Voltage

Modular multilevel converter has many advantages in the field of HVDC transmission, and it will be an important way in power transmission of new energy in the future. Under unbalanced voltage and the analysis of AC active power, the current controller based on positive-sequence and negative-sequence is designed, which eliminates the fluctuation of active power. At the same time, the circulating current in MMC contains positive-sequence, negative-sequence, and zero-sequence components. The conventional circulating current suppressing controller (CCSC) considers only the negative-sequence component, so it is not suitable for the situation under the unbalanced voltage. Based on the analysis of the instantaneous power theory, a general circulating current controller is proposed and designed based on the direct control of the positive-sequence, negative-sequence and zero-sequence components of the circulating current. Through the MATLAB/Simulink, compared with the traditional circulating current suppressing controller, the validity of the proposed control strategy is verified.