A study on DC capacitor voltage control strategy of cascade circuit DSTATCOM

The cascade DSTATCOM has been widely used in various DSTATCOM prototypes and projects due to its advantages such as low loss, high efficiency, little harmonic content in output voltage, easy modularization, and so on.However,this kind of DSTATCOM structure contains inherent unbalance capacitor voltage in the DC-link,which may lead to abnormal running of DSTATCOM,especially in the transient process running of DSTATCOM. Traditional DSTATCOM DC-bus voltage control strategy is three-level DC voltage control. However, when the DC capacitor of all the chain of three-phase circuit is lower than the target value, the first level control will firstly lose control function, then finally the voltage will be a serious imbalance. In this case, it cannot be achieved to the network voltage dynamic compensation.