一种基于虚拟同步发电机的电流谐波抑制方法

A Method of Current Harmonics Suppression Based on VSG

虚拟同步发电机(VSG)可以实现分布式发电系统友好接入电网,然而在实际运行中,电网电压往往含有低次谐波,导致VSG并网电流产生同次谐波,从而恶化并网电能质量。为此,该文通过重塑电网电压谐波频率处的导纳实现对并网电流谐波的抑制。首先建立了VSG的导纳模型,分析了电网电压谐波影响VSG并网电流质量的原因。基于所建立的VSG导纳模型,提出了一种基于陷波器的电网电压前馈控制策略,并推导出电网电压前馈函数的表达式;针对电网电压前馈函数包含微分项且在基频处增益过大会导致过调制的特点,采用谐波频率处部分前馈的方法。最后通过仿真和实验证明了所提控制策略的正确性和有效性。

Virtual synchronous generator （VSG） can make distributed generation connect to power grid friendly. However, in actual operation, there are some low-order harmonics in grid voltage, which will generate the same order harmonics in grid-connected current and worsen the power quality. As for the problem, current harmonics are suppressed by remodeling the admittance at the harmonic frequencies in this paper. Firstly, admittance model of VSG is established. Then the reason that grid voltage harmonics can affect grid-connected current is analyzed. Secondly, according to admittance model, a grid voltage feedforward strategy is proposed based on notch filter, which can suppress current harmonics by remodeling the admittance at the harmonic frequencies. the transfer function of the grid voltage feedforward is obtained. A feedforward partly strategy at the harmonic frequencies is adopted in order to solve the problem that the transfer function of grid voltage feedforward contains differential terms and has a high gain in the base frequency which will cause over modulation. Finally simulation results and experimental results verify the correctness and effectiveness of the proposed strategy.