Research On PCH Control Of Three-phase Photovoltaic Power System Inverter

The development of clean and sustainable solar energy is one of the effective ways to solve the energy crisis and environmental problems at present.Currently,photovoltaic power generation which is one of the patterns has been paid attention and get great development.The inverter is an important part of the photovoltaic power generation system to realize the function of power supply or grid connection.Its performance has a very important impact on the entire power generation system.The three-phase voltage PWM inverter has been used in the field of photovoltaic power generation mostly.However,this kind of inverter is a coupled nonlinear system.The traditional control method is to design the transfer function to control the inverter.The parameter setting is too complex and the control effect is not good.The port-controlled Hamilton(PCH)control theory which based on energy shaping method has been paid more and more attention.It can be used to solve the control problem of nonlinear system.For the inverter control,the advantage is that the physical meaning of the parameter is clear and the design of the controller and the analysis of stability are simple.In this paper,the PCH control of inverter for photovoltaic power generation has been studied.(1)Firstly,the significance of the research on photovoltaic inverter is described and the photovoltaic power generation system is introduced.Then,the advantages and disadvantages of the relevant control theory are introduced,and the control theory of the port Controlled Hamiltonian is derived.The current research situation and control of PCH are introduced further.(2)The mathematical models of the three-phase independent inverter in the threephase stationary coordinate and the two-phase rotating coordinate are established.The PCH model of the inverter is established based on the PCH theory and the general mathematical model.The PCH controller of the inverter is given and the design method is given.According to the results of simulation experiment,the excellent performance of PCH control for independent inverter is verified.(3)In the research of photovoltaic grid-connected inverter control,the control method of direct current control is determined.The PCH controller of three-phase grid-connected inverter is designed Based on PCH control theory and direct current control method.The design method is given.The excellent performance of PCH control in grid-connected inverter is verified by experiments.In addition,the experimental results are compared with the traditional VOC(voltage oriented control)vector control under the same experimental conditions to verify the excellent performance of PCH control further.(4)Two aspects of the expansion based on the PCH control of the grid-connected inverter are carried out.Firstly,the overall PCH control of the inverter with the boost function which is used for the problem that the input voltage of the DC side is low is designed and verified by simulation experiments.On the other hand,a composite PCH control of the two-stage photovoltaic power generation system which is made up of PCH control,PI(proportion integration)control and MPPT control is proposed.Lastly,the feasibility and excellent performance of the PCH control in a dynamic two-stage photovoltaic power generation system are verified through experiments.At the end of this paper,the main work and the shortcomings of this paper are summarized.The work to be improved and studied in the future is also pointed out.