电网不平衡时STATCOM负序电流抑制方法

Negative-sequence Current Suppression Method for STATCOM in the Conditions of Unbalanced Grid

为了改善电网不平衡工况下级联型H桥静止同步补偿器(CHB-STATCOM)输出电流对称度和谐波特性,首先建立了不平衡电网负序电压和STATCOM相内直流侧电压的定量关系,揭示了分离直流侧电压可获得对应的交流负序电压机理,提出通过调节三相直流电压即可直接产生相应的交流负序电压,实现对输出负序电流抑制;其次,利用直流电压闭环调节进一步产生装置高调制比,以改善输出电流谐波特性,最后通过380 V/7 kVA级联型STATCOM样机验证了所提控制方法的正确性和有效性。

In order to improve the output current symmetry and harmonic characteristics of cascade H-bridge static synchronous compensator(CHB-STATCOM)under unbalanced power grid conditions.Firstly,the quantitative relationship between the negative sequence voltage of unbalanced power grid and DC side voltage in STATCOM phase is established,and the corresponding mechanism of AC negative sequence voltage can be obtained by separating DC side voltage.The negative sequence voltage can be generated directly by adjusting the three-phase DC voltage to suppress the output negative sequence current.Secondly,DC voltage closed-loop regulation is used to further generate high modulation ratio of the device to improve the harmonic characteristics of the output current.Finally,a 380 V/7 kVA cascade STATCOM prototype is used to verify the correctness and effectiveness of the proposed control method.