THE VOLTAGE INJECTION ANALYSIS IN SERIES POWER QUALITY CONTROLLER

Series power quality controller (SPQC) can mitigate the voltage disturbances by superposing a voltage on the system voltage. It can be regarded as a series-connected voltage source of the system. It has great effect in condition of voltage sags, surges, imbalances and harmonics. This paper analyzed the characteristic of injecting voltage of the SPQC when the system voltages are unbalanced, proposed some new objects of optimum control strategies for it. On the basis of that, this paper studied the compensation of unbalanced voltage sags in 3-phase 3-wire system and 3-phase 4-wire system. A new algorithm in order to optimize compensating voltage is presented and has been discussed details in case of 3-phase 4-wire system voltage imbalance sags. Simulations are shown to validate the control methods.