基于新型广义积分器的MMC-HVDC桥臂电流控制策略

An Arm Current Control Strategy for MMC-HVDC Based on Novel Generalized Integrators

建立基于桥臂电流的模块化多电平变流器(modular multilevel converter,MMC)数学模型并给出桥臂电流参考值的计算公式。为同时实现MMC交流侧电流控制和环流抑制两个控制目标,提出三相静止坐标系下基于比例积分器(proportional integrator,PI)和两个正弦信号调节器并联结构的桥臂电流控制策略。该文提出一种新型广义积分器(novel generalized integrator,NGI),并从频域和时域的角度对NGI和准二阶广义积分器(quasi second order generalized integrator,QSOGI)进行深入对比分析。对比结果表明,相比于QSOGI,采用NGI作为电流控制器时,控制精度高,相位裕度大,暂态性能较好。仿真结果验证了所提控制策略在对称电网电压下和电网严重故障的情况下均具有良好的控制效果。

The mathematic model of MMC based on arm currents was established and computational formula of the arm current reference was presented. In order to achieve ac-side current control and circulating current suppression simultaneously, this paper presented an arm current control strategy which is based on the proportional integrator and two sinusoidal signal regulators in parallel in the three-phase stationary frame. This paper presented a novel generalized integrator（NGI）, and then thorough analysis and comparison between NGI and the quasi second order generalized integrator（QSOGI） were carried on from the point of time domain and frequency domain. The comparison shows that the control system has good control accuracy and transient performances and big phase margin when NGI is used as the current controller. Simulation results demonstrate that the proposed control strategy can work well under balanced grid voltage as well as under severe grid faults.