Novel control algorithm of tracking harmonic current with little static misadjustment for active power filter with three-level NPC inverter

To improve the overall performance of the three-level active power filter(APF), the closed-loop control system of this APF is investigated, and it is found that tracking command harmonic current is one of the keys to designing this APF. The current state feedback decoupling PI control is analyzed in detail and the limitation of the conventional PI conditioner in the traditional strategies, a novel PI control method is proposed, where the predictive output current value is obtained by the state predictor, and the delay of one sampling period is remedied in this digital control system by the state predictor. The predictive command harmonic current value is obtained by the repetitive predictor synchronously with higher dynamic convergence rate and little static misadjustment. The experiment results demonstrate the steady filtering capability.