Research On The Control Strategy For Double-Stage Single-Phase PV Grid-Connected Inverter

Because of the traditional energy draining,Solar energy had entered the world of people,as a clean,no pollution and depletion's energy,and the PV power generation technology is also increasingly mature.According to connected to the grid or not,PV system can be divided into grid type and off-grid type,The application of PV grid-connected inverter has become the mainstream of PV power generation.According to the cascade form,PV system can be divided into single-stage and multi-stage,and the multistage structure is given priority to the double-stage type;The topic of this design is the research on the control strategy for double-stage single-phase PV grid-connected inverter,and the important parts of the system is the design of the circuit and the analysis of the control algorithm.First,the circuit structure of system was designed,it includes pre-stage circuit and the post-circuit.The parameters of the pre-stage Boost circuit has been determined,the output filter circuit of inverter has also been designed.the advantages and disadvantages of the L type filter and the LCL filter has been comparison and analysis,the LCL filter was choose,and plot analysis was given on the modeling,the methods were given to restrain the resonance peak of LCL filter,and finally the LC parameters in the filter were presented.Secondly,the control circuit and control law were analyzed,and the master control chip has been selected.In order to guarantee the normal work of the system,the sampling circuit,drive circuit,circuit design were designed;The grid-connected form of the system was analyzed,and design the control algorithm,comparative the the PI and PR control algorithm for inner current loop,the disadvantages were pointed out with PI control algorithm,the influence of various parameters were given to use quasi PR algorithm,based on this,through modeling and bode diagram,the parameters of the voltage loop controller was designed.Thirdly,The maximum power point tracking algorithm for the system were analyzed using perturbation and observation method to track the maximum power of the system,software flow chart of the control system was given,System control flow chart of software realization are given,it included the flow chart of main program,the interrupt program,and analyzes the algorithm of software phase lock and Its implementation principle was presented.Finally,the each part of the system were analyzed in the MATLAB simulation,it include the construction of the solar panel module,the application of the maximum power point tracking,compared the control effect of PI control algorithm with PR control algorithm in the MATLAB simulation,and the simulation of software phase lock,those may verify whether the system can work normally or not;Then the experimental analysis was carried out based on theoretical simulation,to verify whether the system can work or not.