Research On The Control Strategy Of DSTATCOM

DSTATCOM based on voltage source converter is a new type of reactive power compensator, which can generate or draw reactive power from the power network. The main object of this paper is to deal with the control strategy of DSTATCOM used in distribution system under balanced loads and unbalanced loads. First, the principle of DSTATCOM is analyzed in detail. By theoretical analysis, the mathematic model based on the variables ( δ , λ ) is modeled, which reflects the characteristics of DSTATCOM. Then, on the basis of this model, the control way of SPWM-based DSTATCOM is investigated, and the dynamic performance of DSTATCOM with different control strategies is compared. The experimental results show that the co-control of control angle and modulation index has better dynamic characteristics. A forward link added to the classic PI controller improves dynamic response, and the regulating time of the tested device from the rated leading var (lagging var) to lagging var (leading var) is less than two cycles. Last, the control strategy of DSTATCOM under the unbalance loads is investigated. The compensation way with the instantaneous value of negative-sequence voltage to adjust the pulse width of balance compensation gains good characteristics, which can compensate negative-sequence current caused by loads effectively and quickly.