Bangyin Liu

The single-stage series-resonant dual-active-bridge (SR-DAB) DC-AC converter, serving as a critical interface connecting DC sources and the AC grid, is often constrained by a narrow zero-voltage switching (ZVS) range and severe circulating current losses, while also requiring the capability to handle varying grid voltages and load fluctuations. To mitigate these limitations, this paper proposes a real-time, analytical Triple-Phase-Shift Variable Frequency Modulation (TPSVFM) strategy. This optimized scheme employs a real-time computational framework that synergizes a simplified analytical model with high-fidelity correction, thereby balancing computational feasibility with control precision. Additionally, a complementary Filtering Compensation Feedforward (FCF) strategy is introduced to suppress output current distortion and optimize system efficiency across the entire operating range. The proposed methodology ensures high flexibility and efficiency across the entire active and reactive power plane, enabling seamless bidirectional power transfer without complex auxiliary controls. Validation using a 500-W experimental prototype confirms the efficacy of the proposed approach, demonstrating a peak efficiency of 98.3%.

The inherent tradeoff between reactive losses and switching losses in inductive power transfer (IPT) systems makes it particularly challenging to maintain high efficiency across a wide output power range. This article proposes a multi-period asymmetrical voltage cancellation (MP-AVC) modulation strategy, where multiple switching periods are combined into a modulation period and the half-wave pulses within a modulation period are asymmetrically canceled. By adopting MP-AVC, the power factor angle of the IPT system will vary periodically around 0° at a consistently low level, ensuring zero-voltage switching (ZVS) operation with low reactive losses. Meanwhile, the equivalent switching count of MOSFETs will decrease as output power decreases, which significantly reduces the switching losses. In addition, the output characteristics, operating principle, and comparison with other modulation strategies are presented. Finally, a 4.3 kW prototype is developed, achieving efficiencies of 97.54%, 97.36%, and 92.29% at output power of 4.3 kW, 2.2 kW, and 27.35 W, respectively.

Single-stage DC/AC converter is increasingly adopted in photovoltaic inverters, energy storage systems and electric vehicle chargers due to its high flexibility, high efficiency and low cost. In this paper, the frequency interaction effect is analyzed based on the frequency domain model of converter. To solve the harmonic coupling problem, a right-inverse harmonic decoupling compensator is proposed. Based on practical requirements for stability and implementability, a least-squares solution for the decoupling matrix is derived. The decoupling strategy improves the effectiveness of the harmonic current controller and reduces current THD. An 500W prototype is implemented, with rated voltage of 48V on DC side and 220Vrms on AC side. Experimental results validate the accuracy of the theoretical model and the effectiveness of the proposed decoupling strategy.

Single-stage dc/ac converter is increasingly adopted in photovoltaic inverters, energy storage systems and electric vehicle chargers due to its high flexibility, high efficiency and low cost. This article introduces a minimum loss trajectory modulation strategy for single-stage SR-DAB based dc/ac converter. By establishing the precise model for the loss of the converter, the operation efficiency is optimized in a 2-D optimization procedure. The two operation modes of the optimized trajectory handle the heavy load and light load operating modes, respectively, which can achieve the highest converter efficiency in the 50-Hz grid cycle. In addition, to solve the problem caused by the discontinuous modulation variables, a seamless mode switching strategy is proposed. An 500-W prototype is implemented, with rated voltage of 48 V on dc side and 220-Vrms on ac side. Experimental results validate the theoretical analysis and the practical feasibility of proposed modulation strategy.