| Photovoltaic (PV) as a solution to global energy crisis and environmental pollution is akey to solar efficiency and cleaning applications, which has attracted more and more attentionof scholars in various countries. PV power generation grid-connected system is main form ofPV power generation. In order to realize PV power generation grid-connected, many keytechnologies are needed to solve. Maximum power point tracking (MPPT) of PV cells affectsthe efficiency of PV power generation system. Grid-connected control technology determinesthe success of PV power generation connecting to the grid. The system applies a two-stagestructure which makes the MPPT control action and grid control action implementedseparately and simplifies the design of controllers. In this paper, main circuit parameters ofthe system are given in detail, and two key technologies of PV grid system are analyzed indetail.Firstly, working principle and characteristics of PV cells are analyzed. MPPTtechnology is described and traditional MPPT technology is introduced and analyzed. For themost widely observed perturbation method, perturbation and observation method based onfuzzy logic control is adopted in this paper, inheriting the advantages of traditionaldisturbance observation method which is simple and easy to be implemented and strongrobustness of fuzzy control, solving traditional perturbation observation algorithmmisjudgment and shocks insufficient, and making PV cells track the maximum power point(MPP) quickly at ambient condition change strong case.The traditional grid-connected control methods remain problems in the loss and dynamicperformance. So sliding mode control method instead of traditional methods for connecting tothe power grid is used in this paper. Sliding mode control is a variable structure controlmethod for a nonlinear system, which can solve poor anti-interference ability and dynamicperformance of the traditional grid-connected control. A detailed design process of slidingmode controller is presented.In order to verify foregoing theoretical analysis, simulation model of a single-phase PVgrid-connected system is built in Matlab/simulink platform. Simulation results show that PVgrid-connected system with sliding mode control has good dynamic performance andanti-robustness. |
