Power weakening control of the photovoltaic-battery system for seamless energy transfer in microgrids

This paper presents a power weakening control (PWC) to regulate photovoltaic (PV) power in excessive power conditions, when the maximum power point tracking (MPPT) algorithm is not needed. Excessive power leads to the overvoltage in the dc bus when available power from the PV arrays is greater than the sum of the load power and the battery power in the stand-alone mode. It is important to be able to control and limit this excessive PV power for protecting the PV-battery system. This paper explains how to handle excessive power in the PV-battery system. The proposed PWC contains an extra dc voltage control loop, power balance block, and hysteresis control, which decides the operation mode between MPPT and non-MPPT modes. The proposed PWC provides the load following function, thus it keeps dc voltage to be constant by controlling the surplus power. Therefore, it makes the PV-battery system more stable and robust under excessive power condition, resulting in improving the reliability of the PV-battery system. MATLAB/Simulink is used to validate effectiveness of the proposed control scheme.