Minimum Switching Losses Discontinuous PWM Strategy for Bidirectional Single-Phase AC-DC Converter with Active Power Decoupling Circuit

Abstract

Active power decoupling circuits are used in bidirectional single-phase grid-connected systems to enhance the circuit lifetime by creating an alternative path for the typical dc-side power pulsating ripple. Therefore, this reduces the requirement of smoothing dc capacitors allowing compact designs even with the implementation of long life metalized film technology. However, with the necessary addition of auxiliary components, extra power losses in the added switching devices and passive components will be introduced, which will inevitably reduce the system power conversion efficiency. To relieve this issue, a new discontinuous pulsewidth modulation (PWM) strategy with minimum switching losses is proposed in this article. This method detects the converter current and reference voltages synchronously to determine the optimum clamped duration of each circuit phase-leg. With such a characteristic, the proposed strategy can realize the minimum switching losses at any instant, thus improving the power conversion efficiency and potentially the power density of the converter. The proposed modulation method is described, analyzed, validated, and compared with different PWM methods on a 2-kVA bidirectional single-phase ac-dc converter with active power decoupling circuit.