Research on Distributed Photovoltaic Microgrid System Based on Dual-Output T-Type Three-Level Converter

For adapt to the function of distributed photovoltaic microgrid system of “self-generating and self-using, margin grid-connected”, from the perspective of cost saving and reducing converter volume, the paper proposed a distributed photovoltaic microgrid system (DTPV-MGS) based on the dual output T-type three-level converter (DT-TLC). The DT-TLC structure can output two sets of AC current with controllable frequency and amplitude. The working principle of the circuit is analyzed in this paper. The upper output of the DT-TLC can be directly connected to the AC source / load operating at different amplitudes and frequencies without additional AC/DC/AC converter units. The lower output is connected to the distribution network through the LCL filter to complete the grid connection. The grid-connected control method of the system is designed. Double-loop control method of grid-connected inverter based on voltage-vector directional control (VO-DCC) is used to control the reference signal of the grid-connected port. For the structure, a time-sharing modulation SVPWM technology is proposed to output the required three-phase AC voltage. In order to reduce the complex workload of SVPWM in the experiment process., a carrier-based pulse width modulation (CBPWM) based on SVPWM is proposed. The switch drive signal is obtained by comparing the modulation wave with the carrier wave. Finally, the feasibility of the proposed DT-TLC-DTPV-MGS, the effectiveness of the modulation method and the control method are experimentally verified.