基于电网谐波电压前馈的虚拟同步整流器电流谐波抑制方法

A Harmonic-Current Suppression Method for Virtual Synchronous Rectifier Based on Feedforward of Grid Harmonic Voltage

虚拟同步机技术可使电力电子变换器表现出类似同步电机的阻尼和惯量特性,从而促进电源或负荷与电网的友好交互。然而,因实际电网运行工况较为复杂,电网电压畸变将导致虚拟同步变换器的并网电流发生严重畸变。为此,该文提出一种适用于畸变电网下的虚拟同步整流器电流谐波抑制方法。首先,运用阻抗分析法,研究电网谐波电压对虚拟同步整流器并网电流的影响机制;其次,基于阻抗分析,提出一种电网谐波电压前馈的方法,通过增大谐波频率处的网侧阻抗,削弱电网谐波电压对并网电流的影响,实现对电流谐波的抑制;最后,采用小信号分析法,研究前馈因子的取值方法,并评估系统的稳态与动态性能。仿真和实验结果证明了该研究方法的正确性和有效性。

The virtual synchronous machine technology can make power electronic converters exhibit damping and inertia characteristics similar to conventional synchronous machines, which is beneficial to the friendly interaction of power sources or loads with the grid. However, due to the complicated conditions of the actual grid, the distortion of grid voltage always leads to serious grid-connected current distortion of virtual synchronous converters. Thus, this paper proposes a harmonic-current suppression method for the virtual synchronous rectifier to solve this problem. Firstly,the influence mechanism of grid harmonic voltage on grid-connected current of virtual synchronous rectifier was investigated through impedance analysis. Secondly, a feedforward method of grid harmonic voltage was proposed accordingly. By increasing the grid-side impedance at the harmonic frequency, the influence of grid harmonic voltage on grid-connected current was weakened, then the current harmonics were suppressed accordingly. Finally, the selection method of feedforward factor was developed by small signal analysis, and the system steady-state and dynamic performance was evaluated. Simulation and experimental results verified the proposed method.