Reactive Power Control of Photovoltaic Grid-Connected Inverters Based on Unfolding Inverter

This paper presents a reactive power control technique for photovoltaic grid-connected inverters utilizing an unfolding inverter topology. Traditional grid-frequency unfolding inverters and certain DC/DC circuits with unidirectional energy transfer paths face challenges in effectively injecting reactive power into the grid. To overcome these limitations, this paper introduces a novel method that adjusts the output current waveform, enabling reactive power injection without requiring modifications to the inverter circuit structure. The proposed technique outperforms conventional methods by reducing total harmonic distortion and expanding the power factor adjustment range, making it suitable for a wide range of grid-connected inverters based on the unfolding inverter configuration. Additionally, the operating principles are thoroughly explained, accompanied by a comprehensive mathematical derivation of the grid current reference waveform. The effectiveness and feasibility of this approach are verified through theoretical analysis and detailed simulation results.