Phase-shifted Full-bridge Photovoltaic Converter Connected To DC Microgrid And Its Control Method

With the depletion of traditional energy sources and the intensification of environmental pollution,distributed new energy power generation such as photovoltaics has received extensive attention.The rise of DC microgrid technology has greatly promoted the development of distributed new energy power generation.Solar energy is widely used as a most common and important new energy source in DC microgrid systems.The intermittent nature of solar photovoltaic power generation and the complexity of microgrid operation make photovoltaic power generation access to DC microgrid with multiple working modes.Except for the maximum power point tracking(MPPT)working mode studied by traditional photovoltaic power plants,there is also a constant voltage working mode and a constant power working mode.And the flexibility of the working mode of the photovoltaic power generation system contributes to the stable operation of the microgrid system.Therefore,it is of great significance to study the connection of photovoltaic power generation to DC microgrid.In this paper,the various DC/DC converters used in photovoltaic power generation are summarized and analyzed.In this paper,a phase-shifting full-bridge zero-voltage-switching(ZVS)converter is used,which is easy to achieve high-power and high-efficiency,with wide gain range and electrical isolation functions.This paper analyzes its principle in detail and verifies it through simulation.Then the three working modes and corresponding system states of the PV converter in the bipolar DC microgrid are analyzed in detail,and the corresponding algorithms are designed for each mode.Combined with the output characteristics of photovoltaic cells,the MPPT mode is designed with a perturbation observation control algorithm based on PI control.A dual PI loop algorithm is designed for constant voltage mode and constant power mode.The Matlab simulation model is built to verify the effectiveness of the proposed algorithm in each mode,and smooth switching is achieved before different working modes.Then the hardware design of the phase-shifted full-bridge ZVS photovoltaic converter is carried out,including the main power circuit design,control circuit design and auxiliary power supply design,and the photovoltaic converter is developed.Finally,an experimental platform was built to connect the phase-shifted full-bridge ZVS PV variator to the bipolar DC microgrid platform.The photovoltaic multiple working modes experiment and switching experiment were carried out on the experimental platform.Theexperimental results verify that the designed algorithm can effectively connect photovoltaics into the bipolar DC microgrid,achieving the flexibility of photovoltaic power generation and the stable operation of the bipolar DC microgrid.