Research On Nonlinear Control Strategy Of Photovoltaic Grid - Connected Inverter

Photovoltaic grid-connected inverter is the important component of photovoltaic powersystem，its performance will directly affect the performance of the system. For the fixedtopology, the grid-connected inverter’s performance depends on the control strategy. Mostphotovoltaic grid-connected inverter adopts voltage source PWM inverter topologystructure, because this structure has merits of the controlled power factor and sine currentof nets side. In view of the nonlinearity and passivity of grid-connected inverter’smathematical model, the passivity–based control (PBC) based on the energy control viewis adopted to improve the control precision of the controller. The proposed controller canredistribute the system energy, and adopt the approaches of injecting damping anddecoupling to optimize the controller. The final designed controller has many advantages,as simple algorithm and less adjustable parameter, etc. Simulation and prototype resultsshow that passivity-based control method is practicable.This paper has six parts. In the first part, there is a brief introduction for researchbackground and meaning, and at the same time several mature control strategies are simplydescribed. In the second part, we introduce the voltage source photovoltaic grid-connectedinverter’s topology structure and math model, and the principle of SVPWM. And in thethree parts, the passivity concept is introduced, and the passvity and stability ofEuler-Lagrange(EL) model and port controlled Hamiltonian with dissipation (PCHD)model is proved. The fourth part is the controller research of three phase photovoltaicgrid-connected inverter base on the EL and PCHD model, and the passvity and stability ofphotovoltaic grid-connected inverter is proved.While the fifth part is experiment analysisfor the proposed control strategy. In the final part, there are summary and outlook for thistopic.The main work and conclutions of this paper are statesd as follow:(1) To analyse and prove the passivity of photovoltaic grid-connected inverter, and buildthe current modle and power model of photovoltaic grid-connected inverter based onthe passivity.(2) To build the EL modle and PCHD model of photovoltaic grid-connected inverter, anddesign the passivity based controller for those kinds of models.(3) To build the simulation stucture for the control strategy of three-phase photovoltaic grid-connected inverter base on the passivity of system.(4) To design the5kVA prototype platform for the three-phase photovoltaic grid-connectedinverter based on DSP TMS320F28335A.