Research On Optimal Control Strategies Of Photovoltaic Grid-connected Inverter

To improve the efficiency of the photovoltaic cells'output power, optimize photovoltaic grid-connected generation system'power quality, the text made a study of photovoltaic inverter maximum power point tracking (MPPT) control, the reactive power and harmonic control method.To make the internal resistance of PV cells and the load resistance match, output maximum power in the current environment conditions, the text adopted fuzzy logic control which was based on BOOST converter to study maximum power point tracking control. This control method was simulated with SIMULINK toolbox, the result certificated that fuzzy logic control method improved traditional method's disadvantages, achieved the unity of accuracy and fast tracking. Simultaneously, It elevated the voltage of the DC side, avoided the disadvantages by use of low frequency transformers.Since the grid-connected method of photovoltaic grid-connected generation system adopted current source method, the current must track the fundamental voltage of grid to make the system output completely active power. Besides, the fundamental voltage of grid is often interfered by harmonic signals. Simultaneously, inverters belong to power electronic equipment which works in a state of high frequency switching. It makes the output power has harmonics which if are not well controlled, it will pollute the grid's power quality. For the above reasons, the text adopted synchronous repetitive and PI control which based on the voltage space vector pulse width modulation(SVPWM) to optimize the power quality of the system. Synchronous repetitive and PI control converted system analysis's coordinate space to synchronously rotating frame, with the use of decouple control, realized active power and reactive power individually controlled. In this space, repetitive and PI control not only realized rapidly tracking of grid voltage, but also eliminated periodic disturbance (harmonics), in this way, achieved the aim of improving the power quality. Finally, this control method was simulated with SIMULINK toolbox. By adding harmonic disturbance of the grid's voltage, the feasibility of the method had been proved.