Wide-Voltage Input Photovoltaic Microgrid System Based on Multi-Port Three-Level Converter

This article presents a photovoltaic micro-grid system structure with multiport three-level converter(MP-TLC). In this structure, two AC power supplies/loads with different operating amplitudes and frequencies can be directly connected through MP-TLC without multiple power conversion units. Compared with the traditional configuration, the structure of the multi-port converter photovoltaic microgrid system operates under a multi-level voltage, which reduces the number of power conversion stages, reduces the number of power switches, and reduces the overall volume and cost of the system. In addition, a carrier-based time-sharing space vector modulation strategy is proposed to solve the problem of two output couplings of MP-TLC under SPWM modulation, so that the two output ports can work relatively independently. Compared with the traditional SVPWM modulation strategy, the carrier-based time-sharing space vector modulation strategy omits many trigonometric function calculation processes, which effectively improves the calculation speed of the algorithm. This article also presents a voltage-pumping DC-DC converter for the DC boost link in a photovoltaic micro-grid system. The converter can obtain a high voltage gain at a very low duty cycle and is suitable for a wider range of photovoltaic cell voltage input. The experimental results verify the effectiveness of the wide voltage input photovoltaic microgrid system based on MP-TLC.