An Isolated Bidirectional Microinverter Based on Voltage-in-Phase PWM-Controlled Resonant Converter

A single-stage single-phase isolated bidirectional microinverter based on a voltage-in-phase pulsewidth modulation (VIP-PWM)-controlled resonant converter is proposed in this article. With the VIP-PWM control, the voltage conversion ratio of the resonant converter can be regulated from zero to infinity, theoretically, which means the VIP-PWM is suitable for wide-voltage-range applications, such as single-stage isolated inverters. Moreover, the voltage conversion ratio of the resonant converter is only determined by the equivalent duty cycle and is independent of the value and the direction of the transferred power. Therefore, the value and the direction of the power flow can be changed smoothly, which makes the proposed converter suitable for bidirectional dc-ac power conversion. Accordingly, a simple unified current controller can be employed for both inverter and rectifier modes. In addition, soft switching can be achieved during most of the grid period, and high efficiency can be achieved with the proposed solution. Detailed operation principles, characteristics, design considerations, and control strategy of the proposed microinverter are presented. A 300-W prototype with an input voltage range of 25-40 V is established and tested to verify the effectiveness and feasibility of the proposed solution.

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