Topology and Control Strategy of Modular Three-Port Converter

In response to the technical bottlenecks of low AC collection efficiency, low grid-connected stability, and weak grid support capability in large-scale photovoltaic (PV) grid-connected systems under weak grid scenarios, this paper proposes a modular three-port converter (MTPC) topology that integrates high-efficiency PV DC collection, safe AC grid connection, and flexible DC transmission. Firstly, the circuit structure and operating principle of the MTPC topology are introduced, and the equivalent circuits for the converter to realize the DC conversion and AC inversion functions are analyzed. Based on this, the port voltage control strategy and DC port harmonic suppression strategy for the converter are proposed, and the configuration principle for each bridge leg submodule as well as the design method for bridge leg inductance and submodule capacitance parameters are presented. Finally, PSCAD simulation results verify the feasibility and effectiveness of the proposed topology and control strategies. The proposed MTPC topology can provide a novel technical solution for safe and efficient grid connection of large-scale PV in remote weak grid areas such as deserts, wastelands, and barren lands.