A Novel Method for Maximum Power Point Tracking of the Grid-Connected Three-Phase Solar Systems Based on the PV Current Prediction

In this paper, it is first attempted to provide a small signal model of the photovoltaic (PV) system, DC-DC boost converter, and pulse width modulation (PWM) generator. Then, a technique is provided for maximum power point tracking (MPPT) in grid-connected solar systems based on variable and adaptive perturbation and observation with predictive control of the PV current. An innovative aspect of the proposed predictive current control method is to use the current controller to achieve the value of PV impedance, which has been used in DC-DC boost converter. The proposed method is to obtain the coming current value on the basis of the current predictive model. The goal of the proposed method is to make the DC-DC boost converter inductor current track the current reference. Voltage and current ripple minimization is added to the cost function simultaneously as a system constraint to optimize system performance. This reduces the amount of voltage and current fluctuations around the maximum power point. The proposed method is capable of detecting rapid changes in solar radiation. A sudden and simultaneous increase in voltage and current is detected by the algorithm and then the duty cycle becomes increasing instead of decreasing. The simulation is carried out in MATLAB Simulink environment in real-time for a 26.6 kW three-phase grid-connected solar system. The simulation results of current predictive control are compared with perturbation and observation techniques and linear voltage and current proportional integral derivative (PID) controller-based adaptive control. The results show that the total harmonic distortion (THD%) of the inverter voltage with proposed method has been reduced by 0.16% compared to the PID method. In addition, the THD% of the current in the proposed method is reduced by 0.1% compared to the PID method. The solar system output voltage variation of the proposed method is less than 5 V.