Design of series submodular photovoltaic grid-connected inverter

Multilevel inverter can achieve high voltage output through low voltage withstand switching devices, which has been widely used in photovoltaic (PV) grid-connected, but there are problems of complex system control and low efficiency. In order to optimize these problems, this paper proposes a new series submodular topology of photovoltaic grid-connected inverter to reduce the switching frequency of the high voltage stage switch. The introduction of a special precision adjustment module can achieve lower voltage waveform output accuracy and reduce the parameter size requirements of the LC filter. The grid-connected algorithm and the sub-module capacitor voltage sharing algorithm for this topology are proposed. The control of the grid-connected algorithm is very simple. In order to verify the feasibility of the method, this paper uses the simulation platform to build a grid-connected PV inverter model with 7-stage series sub-modules. The experimental results show that the proposed PV inverter topology, grid-connected control algorithm and capacitor voltage sharing algorithm have theoretical feasibility.