A new control strategy for instantaneous voltage compensator using 3-phase PWM inverter

In a three-phase power system, unbalanced voltage with harmonics can be detected on the synchronous reference frame. Assuming that there is no neutral path in the power system, an unbalanced voltage with harmonic components has a DC component, a 2nd harmonic and the other harmonic components. Therefore, it is possible to compensate unbalanced voltage and harmonic voltage by cancelling the harmonic components, exclusive of the DC component on the d-q axis. In addition, by adjusting the value of the DC component obtained from positive sequences, the regulation of load voltage is achieved. This paper presents an algorithm performing compensation of unbalanced and harmonic voltage as well as maintaining the constant voltage in the load side. The compensating characteristics of the proposed instantaneous voltage compensator are also discussed.