基于Z源逆变器的永磁直驱风电系统不对称故障穿越策略

基于Z源逆变器的永磁直驱风力发电机组在不对称电网故障下运行时,将导致并网电流含负序分量,Z源网络电容电压泵升并含有二倍工频纹波等问题。由于系统机侧采用三相不可控整流,无法解决Z源网络电容中二倍频对发电机转矩脉动的影响,本文采用储能型Crowbar方案,通过对故障时系统功率流动的分析,提出一种基于Z源逆变器的永磁直驱风电系统不对称故障穿越策略,采用比例谐振控制器使流入储能装置的功率无静差跟踪发电机输出功率和Z源逆变器输出功率之差,不仅限制了故障时Z源网络电容电压的泵升,还消除了Z源网络电容上的二倍工频纹波。此外,通过在正负序同步坐标变换下电网正负序电压分别定向的方法,抑制了并网电流的负序分量。仿真和实验结果验证了所提控制策略的有效性。

A Ride-Through Strategy of D-Permanent Magnet Synchronous Generator System Based on Z-Source Inverter During the Asymmetrical Faults

Asymmetrical grid faults will introduce negative sequence components into grid-connected currents, and results in overvoltage or large voltage fluctuations across the capacitors in a Z-source inverter (ZSI). When the ZSI is used to a wind power generation system, the voltage fluctuations may even lead to generator torque ripples. Thus, this paper proposes a ride-through scheme to mitigate the adverse effects caused by asymmetrical grid faults, for the ZSI-based wind power system using permanent magnet synchronous generator (PMSG). In this scheme, the solution based on super-capacitor, controlled by a proportional-resonant controller, is used to limit the voltage rise and reduce the voltage fluctuations in the ZSI. Meanwhile, the negative sequence components of the grid currents are eliminated effectively, by using separate positive and negative sequence control loops. Simulation and experimental results are presented to verify the effectiveness of the proposed control scheme.