Research On The Control Strategy For Two-stage Single-phase Grid-tied PV Inverter

As environmental pollution and energy crisis is getting more serious, much more attention hasbeen paid to the development and application of the renewable and clean energy. Solar photovoltaicenergy has been exploited with the advantages of distributed throughout the earth, recyclable and soon, meanwhile photovoltaic power generation is developed rapidly as the main application of the solarenergy. Therefore, as the key part of the solar power generation system, the topology and controlstrategy of the photovoltaic conversion play an important role in the whole system.In this thesis, the main research content is the influence on the volume, efficiency and controlperformance of the whole system by using different control strategies based on two-stage one-phasegrid-tied PV inverter. Firstly, the specific implementation method of the conventional control strategyis elaborated. On this basis, an optimal choice of such parameters of the perturb and observe (P&O)maximum power point tracking algorithm (MPPT) is proposed. In addition, a mathematical model ofthe voltage-current loop is established. Secondly, a novel time-sharing dual-mode control strategy iselaborated, and an optimized mathematical model of the grid-current loop is established. Meanwhile,the cause and inhibition method of the ripple voltage at the PV module terminals is discussed. Theintegration of MPPT method with the adopted control strategy is also proposed. Moreover, the PVmodule, is hypersensitive to ripple in the output voltage. Although the ripple does not damage the PVmodule, it reduces the available power. Therefore, the inner relationship between terminal ripplevoltage and the utilization of PV module is deduced, and the design of the main energy storageelement is proposed. Finally, the comparison on efficiency of the system between two controlstrategies is proved in a quantitative way with the usage of loss analysis method.In this thesis, simulation models on the different control strategies for two-stage one-phasegrid-tied PV inverter are built in MATLAB/Simulink. In addition, an experimental platform based onforegoing topology controlled by TMS320F2808is established for experimental justification. Thesimulation and experimental results present that the basic functions of grid-tied PV inverter based onboth control strategies can be realized. Furthermore, time-sharing control strategy results in less lossand high efficiency than that of conventional control strategy at the same power rank. However, thevolume of the two situations makes little difference, and simultaneously, the ease of realization,system stability and THD of gird current on the time-sharing control strategy are inferior to theconventional one.