A Study on the Influence of Three-phase Unbalance of AC Side Voltage on on the Operating Characteristics of VSC

In this paper, the influence of the AC three-phase voltage unbalance problem in the low-voltage distribution network on the operating characteristics of the VSC is studied. This paper deduces the expression of the negative sequence component of the three-phase unbalanced voltage after park transformation and develops the simulation model of the low-voltage DC distribution network. The correctness of the theoretical derivation is verified by simulation. The simulations of three-phase unbalances of 5%, 10%, and 15% were performed to investigate the effects of different three-phase unbalance on DC voltage. The results show that the three-phase voltage imbalance on the AC side will introduce a double-frequency voltage component on the DC side. The greater the voltage imbalance, the larger the amplitude of the introduced double-frequency voltage component, and the more serious the impact on the DC voltage quality.