The phase shifter as an efficient measure of regulating the power flow by inserting compensation voltage has important significance for improving the utilization ratio of transmission lines

balancing system power flow

and etc. Based on the thyristor controlled double core symmetry phase shifter

a simple system model is built in the real time digital simulator (RTDS) and the control device is developed. In consideration of the influence of different firing angles

a control strategy is proposed. The firing pulse is advanced before current zero-crossing when the voltage tap is fixed and after current zero-crossing when the voltage tap is being regulated. And a detection method of current zero-crossing is also presented. The result shows that the system is stable and harmonic-free at the fixed voltage tap. The transition is smooth and short-current-free during voltage tap regulation.