An Improved Master-Slave Control for Three-port Converter Based Distributed DC Grid-connected PV System

With the development of DC grid technology, it has become a trend to introduce photovoltaic(PV) as a power source to the DC power distribution network. In this paper, an improved master-slave control strategy is proposed to realize power splitting and voltage sharing in a modular system with PV connected. Each module is a three-port converter: Input port connects distributed PV, output port connects to DC grid, and intermediate port is connected in parallel with other modules as a bus to realize the power splitting. For a single module, input voltage, intermediate bus voltage and output voltage should all be controlled to reference but only duty ratio and phase-shifting angle can be regulated hence it may occur the multi-objective variables control problem. While using the proposed strategy, this problem can be solved effectively and the system stability is ensured during the voltage sharing process. This control strategy is verified by simulation and experiment.