A DC Hybrid Active Power Filter and Its Nonlinear Unified Controller Using Feedback Linearization

In the current power system, the conversion between dc and ac is widely existing and the dc-side harmonic problem is prominent. To suppress the second-harmonic current at the dc side of a single-stage single-phase inverter, a dc hybrid active power filter (DC-HAPF) structure is presented, which composes of a bidirectional dc-dc circuit-based active power filter (APF) and a CL passive filter. In this article, the CL passive filter is used to mitigate the high-frequency harmonics and the APF is applied to compensate the low-frequency harmonic current. Meanwhile, the influence of the filter parameters on the harmonic suppression is analyzed based on the average switching model. In addition, for the control of the DC-HAPF, a nonlinear unified controller via feedback linearization is proposed, where the voltage and current dual-loop control is converted to a single-loop control of energy. By analyzing the control system stability and DC-HAPF's performance, appropriate control parameters are selected. To verify the feasibility of the proposed topology and control strategy, a 500-W single-stage single-phase inverter with the DC-HAPF is built and a good performance of the dc-side harmonic suppression has been achieved.