Research On Autonomous Control Of Photovoltaic Unit For Ship's DC Microgrid

In order to reduce the consumption of fossil energy and solve the problem of marine environment pollution,the development and utilization rate of renewable energy such as photovoltaic(PV)energy in modern ships are constantly increasing.At the same time,the ship's DC microgrid technology,with its advantages of energy saving,simple control and high adaptability to renewable energy,has become the future development direction of the ship's electric power field.This paper takes the PV unit in ship's DC microgrid as the research object,aiming at improving its dynamic performance and solving the transient disturbance caused by its working mode switching.The main content of dissertation are as follows:Firstly,this paper summarizes the background,significance,research status and control strategy of ship's DC microgrid and PV unit.Secondly,design the double integral sliding mode controller of the boost converter to improve the dynamic performance and stability of the converter after the PV cell and its boost converter are modeled and analyzed.Then,compare its performance with PI controller.Thirdly,aiming at the problem that the working modes switching of PV units will lead to a sharp drop of DC bus voltage in DC microgrid hierarchical coordinated control strategy,a control strategy based on DC bus voltage information to offset and compensate the reference working points of PV cells is proposed,which realizes the unified control of maximum power tracking mode and constant voltage control mode of PV unit,and seamless switching between the two modes.Fourthly,in order to verify the double integral sliding mode controller and the proposed seamless switching control strategy of PV unit,an off-grid PV/storage DC microgrid experimental system is developed,and the hardware and software of PV unit are designed.Finally,the experimental system of off-grid DC microgrid is tested and analyzed.The result shows that the double integral sliding mode controller can improve the dynamic performance and anti-jamming ability of PV units.At the same time,the seamless switching control strategy proposed in this paper can achieve smooth switching between the working modes of PV units.