微电网故障下三相电压型并网变换器瞬态行为分析

三相电压源型变换器(VSC)是交直流混合电力系统中重要的功率接口装置。交直流混合系统存在诸如电网侧故障或直流侧负载变化等扰动,对其中功率接口变换器造成难以预计的影响。着重研究微电网故障时并网变换器的瞬态响应过程及其机理。首先,给出了电网三相电压暂降时三相电压源型变换器的失稳的瞬态响应现象。然后,通过非线性分析揭示了该不稳定现象的物理本质,并通过系统建模计算给出了系统参数空间中的稳定域范围;最后,通过微电网与变换器仿真验证了分析计算的有效性。

Transient Response of Three-phase Grid-connected Converters under Grid Fault

Three-phase voltage-source converters (VSC) are commonly used as a power flow interface in AC/DC hybrid power systems. The system may suffer from unpredictable transient disturbance from DC-side or grid-side faults. The nonlinear characteristics of VSCs have already been iden-tified as exhibiting catastrophic bifurcation when there is a DC-side disturbance. In this paper, the transient response of a three-phase VSC un-der practical grid fault condition is studied. The converter will also exhibit a catastrophic bifurcation after the transient disturbance. The expand-ed AC current will cause excessive devise stress. A large-signal analysis is adopted to reveal the physical origin of the phenomenon and to locate the boundary of the instability. The phenomenon and the stability boundaries are verified by cycle-by-cycle simulations.