Improved Predictive Calculation-Based Extinction Angle Control for HVDC

In HVDC projects, the predictive calculation-based extinction angle control (PC-EAC) generates the firing angle order by means of open loop. Under the steady-state condition, the result of its calculation is accurate. However, when a fault occurs in AC system, a serious calculation error will exist, which increases the risk of commutation failure. Therefore, an improved control is proposed. In this control, the firing angle order of each converter valve is separately calculated according to its commutation voltage, and considering the influence of the firing pulse control system, a compensation term is added to eliminate the deviation between actual firing angle and its order. In order to ensure the equidistant pulse control of each converter valve, the minimum firing angle order of all valves is taken as the output of the controller. Finally, several simulations are conducted on the CIGRE HVDC Benchmark model and a +/- 500 kV/3 kA project model to validate the performance of the proposed strategy. The simulation results show that the proposed control can effectively reduce the risk of commutation failure, and make the system recovery more stable.