虚拟同步机接入弱电网的电能质量新问题及谐波抑制方法

Power Quality Issues and Harmonic Suppression Method of Virtual Synchronous Generator Connected to Weak Grid

对比了VSG和传统电流型并网逆变器(TGCI)接入弱电网下的谐波域模型,发现传统谐波电流抑制方法并不适用于VSG,同时弱电网条件下非线性负载谐波电流和电网谐波电压对VSG谐波输出阻抗的要求是相互矛盾的,进而导致VSG接入弱电网下的问题更加复杂。提出一种阻抗重塑型谐波电流抑制方法来提升VSG接入弱电网的友好性,主要包含无源和有源部分,有源部分是通过公共耦合点(PCC)电压和附加电压两个变量的适当负、正前馈,增加从电网侧到VSG的谐波阻抗,同时还减小PCC到VSG的输出阻抗,有效地解决VSG接入弱电网的并网电流畸变严重的难题。最后,搭建了10 kW的VSG样机平台验证了所提方法的有效性。

The paper compares the harmonic models of virtual synchronous generator(VSG)and traditional current type grid-connected inverter(TGCI),and points out that the traditional harmonic current suppression method is not suitable for VSG.Moreover,the requirements of the reshaped harmonic output impedance of the VSG are in conflict,viewed from the grid harmonic voltage and load harmonic current under weak grid condition,resulting in the more complicated power quality issues of the VSG integrating into the weak grid.To this end,the paper proposes an impedance reshaping method for suppressing harmonic current distortion,mainly consisting of the passive and active approaches to improve friendliness between the VSG and the grid.In the active approach,based on the negative and positive feedback of PCC voltage and additional voltage,the active branch can not only increase the harmonic impedance from the grid side to the VSG,but also reduce the output impedance from the PCC to the VSG,which effectively solves the grid-connected current distortion problem.Finally,a prototype platform of 10 kV VSG is built to verify the effectiveness of the method.