Study Of The MPPT And Grid-connected Control Strategy In PV Systems

Because the storage capacity of global non-renewable fossil energy is limited and the demand for energy caused by the development of human society is unlimited, the contradiction become more and more serious,which will lead to the decrease and imbalance of global economic. Under this background, use renewable energy has become an effective way to resolve this contradiction. Solar energy can be a renewable energy source, its development and use attracts the world’s attention. PV is an effective way to make full use of solar energy, most domestic photovoltaic allow parallel operation provide conditions for the future development of China’s photovoltaic power generation. Maximum power point tracking PV array (MPPT) and the grid control strategy of photovoltaic inverters is the two key technologies of PV system performance which directly affects the efficiency and stability of the entire PV system.Firstly, in this paper, we modeled and simulated the characteristic curve of the PV array power output under different circumstances, the goal of MPPT is to maintain the output voltage of the PV array at the maximum power point. Compared the current maximum power point tracking control method commonly used for partial shade, analyzed the tracking control method based on the maximum power point of particle swarm optimization (PSO), proposed an maximum power point tracking control method based on improved simulated annealing particle swarm optimization, integrated the simulated annealing algorithm thinking and particle swarm algorithm, improved the explore ability of particles and enhance the speed and accuracy of the maximum power point tracking algorithm convergence.Secondly, elaborated the principles and objectives of PV grid control strategy, compared the advantages and disadvantages of several common grid inverter control strategies. Against for the harmonic pollution and reactive load of the local grid system,we proposes a new composite grid control strategy combination of proportional-integral (PI) control and proportional-resonant (PR), control of PI control the grid electric current, and control of PR control local nonlinear load control reactive power compensation and harmonic suppression. This strategy improved the efficiency of photovoltaic grid-connected inverter, improved the quality of the power. Through the simulation experiments, the strategy can compensate for reactive power and harmonic local load output active power to the grid at the same time.Beside these, this paper also elaborated the design process of the single-phase photovoltaic grid-controlled device of the DSP TMS320LF2812 chip, including the software implementation frequency, phase difference detection method, software lock-in technique of realization of SPWM and so on. Based on these, we produced a single-phase grid-connected PV system, the experimental results means well.