A Min–Max Closed-Loop PLL-GSPWM for Circulating Leakage Currents Attenuation in PV Station

Traditionally, photovoltaic (PV) inverters assume the specific topologies or transformer to attenuate the circulating leakage current. Alternatively, the circulating leakage current in PV station can also be attenuated by pushing the inverters' carrier angle being zero degree in theory, which however is too hard to be realized because it relies on additional low-latency communication channels. Being different, this article proposes a min-max closed-loop phase-locked-loop based global synchronous pulsewidth modulation method for circulating leakage current attenuation in PV station. In specific, the circulating leakage currents of parallel-connected PV inverters can be treated as a multi-input multi-output (MIMO) system. Then, this article analyzes the relationship between the phase shift values of carriers and the leakage current. Next, the dominating carrier phase shift value for the maximum leakage current is analyzed and selected. Doing so, the MIMO system is simplified as a single-input single-output system and then the perturbation and observation algorithm can be assumed to minimize the circulating leakage current. It is noted that the proposed method does not need low-latency communication channels to synchronize the carrier phase angles and immune the uncertain operation parameters. Experimental prototype with four down-scale inverters verified the performance of the proposed method.