Parameter Design Of Front Stage Controller And Research On Back Stage Active Damping Control Strategy For Double-stage Grid-connected Photovoltaic Power Generation System

Energy and environmental issues not only promotes the rapid development of new energy power generation, but also creates the fast development trends of PV power generation. In this thesis, the double-stage grid-connected PV power generation system is used as the research object, state-space averaging method is employed to model the system to give systematic design method for front stage controller parameters, and then a power decoupling control strategy with active damping for the grid-connected inverter with LCL filter is given by using a active damping method called virtual resistor in parallel with filter capacitor. In the end, simulation study is used to verify the correctness of the design method for controller parameters as well as the decoupling control strategy.Firstly, the thesis introduces the background, object and significance of the project, summarizes the development status of PV power generation at home and abroad, and surveys the topology structure and control technology of a double-stage grid-connected PV converter.Secondly, the overall structure and working principle of a double-stage grid-connected PV power generation system are introduced, and the overall characteristics of the front stage converter system are analyzed while its parameters are designed. In view of a MPPT control structure with power-voltage double closed-loops, state-space averaging method is adopted to establish the nonlinear model of the system, and then the linearization method close to equilibrium point is used to obtain its linear model. By analyzing the model,s frequency response as well as its root locus, the systematic design method for front stage controller parameters is given to avoid the blindness of trail and error method.Thirdly, its working principle and modulation method of a inverter system with LCL filter in back stage of a grid-connected PV power generation system are presented, and the parameters of the LCL filter are designed. A method called virtual resistor in parallel with filter capacitor is used to eliminate LCL filter resonance, and a power decoupling control strategy with active damping for a inverter with LCL filter in back stage is given base on this method.Finally, the simulation model for a double-stage grid-connected PV power generation system of 12 k W is built up, the simulation results show that in the cases of standard illumination and natural illumination changes, the controller and the control strategy proposed in this thesis can not only realize maximum power tracking control and grid-connected unity power factor control quickly, but also suppress the resonance of LCL filter effectively. As a result, the system gets a good control performance.