Constant Power Control Strategy for Photovoltaic Generation in DC Micro-Grid

Background: Currently, power control of PV generation focuses on the Maximum Power Point Tracking (MPPT) strategy, with which PV systems is sensitive to the light, temperature, and micro-grid state, and introduces power fluctuation to the micro-grid. Methods: With the schedulable requirements of Photovoltaic (PV) systems in the grid-tied mode, PV generation systems should possess constant power output capability. This paper proposes an approach for constant power control of PV systems in DC micro-grid. By analyzing the output characteristic between active power and voltage of PV systems, and acquisition of PV output current and the capacitor voltage, voltage control reference in the PV power-voltage curve is obtained by Lagrange interpolation fitting. Result: With the implementation of closed-loop control of photovoltaic boost voltage, constant power output control of PV generation systems can be achieved. Further, this method is able to cope with the change of light and temperature and micro-grid bus voltage. This method is simple and has good environmental adaptability and fast-tracking speed. Conclusion: Simulation results verify the effectiveness of the proposed control strategy compared with a perturb and observe method which can attain the same function.