Unbalance Loads Compensation With STATCOM Based on PR Controller and Notch Filter

The STATCOM based on four-leg voltage source converter is used to compensate the reactive currents, harmonic currents and unbalance loads currents of the network. When the STATCOM compensates the unbalance loads of the network, the DC voltage will contain the second harmonic. The second harmonic has influence on the current control loop, and the network currents will contain the third harmonic and negative currents. The direct-axis component and the quadrature-axis component currents contain the second harmonic which has influence on dynamic characteristics of the current control loop. In this paper, the mathematical model of the STATCOM is established. And a novel control strategy based on PR control and notch filter is proposed. The notch filter suppresses the second harmonic in the DC voltage, and the negative currents and harmonics the STATCOM generated is filtered. With the PR control method, the second harmonic of the direct-axis component and the quadrature-axis component currents could be tracked precisely in real time. And the direct-axis component and the quadrature-axis component currents are compensated precisely and dynamic characteristics could be guaranteed. With the control strategy, the DC capacitor is used to buffer the unbalance power, and the STATCOM compensates the unbalance currents precisely. Simulation and experimental results verify the effectiveness of the proposed control system.