PCC voltage stabilization by D-STATCOM with direct grid voltage control strategy

The STATic synchronous COMpensator used in Distribution system (DSTATCOM) can stabilize the grid voltage of the Point of Common Coupling (PCC) by injecting or absorbing reactive power to the grid. Traditional strategy which stabilizes PCC voltage indirectly by compensating load reactive current exposes its disadvantages when the impedance of distribution network is varying, and the load or the sending-end voltage is fluctuating. This paper presents a direct grid voltage control strategy that adopts a D-STATCOM based on cascaded multilevel converter to support the voltage of PCC. The simple model of the relationship between the reactive power and the PCC voltage is established and the design of PI controller by using pole-zero cancellation method is given. Simulation results with Matlab/Simulink prove the validity and applicability of the proposed method.