Research On Predictive Control Method Applied For PV Inverters

distribution, cleanliness and free pollution. Photovoltaic (PV) power generation as an important form of the solar energy utilization, will be the fastest and most promising solar energy utilization technology. Inverter is an important part of PV power generation system, one for grid-connected operation of PV power generation system, sending electricity into the grid; one for off-grid PV power generation system, providing power for independence loads. Aiming at the existing problems of inverter control methods, this paper will research on model predictive control method suitable for PV inverters.According to the basic principle of model predictive control method and choosing the output current of the grid-connected inverter as the state variable, this paper puts forward a PV inverter model based on model predictive current control. Comparison with traditional linear controller is studied and analysis of examples are also made in PSCAD/EMTDC platform.Secondly, on the basis of model predictive current control method, control strategy of photovoltaic inverter is studied. When the grid voltage is within the normal range, the outer voltage loop is used to realize the MPPT control, and gives the inner ring current reference; when grid voltage three-phase symmetrical sag occurs, the designed low voltage ride through control strategy allocates the active current and reactive current reference again according to the change scope of the voltage; When grid asymmetric fault occurs, respectively to inhibit active power fluctuations and negative sequence current component as the control target, the reference value of different phase sequence current is calculated. After the current reference value is obtained by the above different circumstances, the inverter is set to track the reference current by the model predictive current controller. Simulation verifications of the control methods and control strategies are also made in PSCAD/EMTDC.Finally, the model predictive control method for three phase four leg off-grid photovoltaic inverter is studied. Considering the special requirements on output voltage of independent power supply system, choose load voltage as the state variable. And then the model predictive voltage control method with the improved two-step prediction suitable for off-grid PV inverter is put forward. At last on the simulation platform the practicability and performance of the method is investigated.