A technique for tracking the global maximum power point of photovoltaic arrays under partial shading conditions

摘要

The Power-Voltage (P-V) characteristic of a Photovoltaic (PV) array operating under partial shading conditions is characterized by multiple peaks. Out of these one only is the Global Peak (GP). When the PV array is subject to partial shading, conventional techniques many times fail to track the GP, because they find local peaks in the vicinity of the open circuit voltage. It is, thus, necessary to adopt special Maximum Power Point Tracking (MPPT) technique for tracking the GP of an array under partial shading conditions. In this paper a MPPT is proposed which tracks the GP of an array under the influence of partial shading. In this method the PV array is isolated from the load for a negligibly short period of time and is connected to an external capacitor for scanning of its P-V curve. During charging time of the capacitor, the proposed circuit tracks the GP. After MPP tracking, Perturb and Observe (P&O) technique is invoked to track the MPP as a result of moderate variation in the ambient conditions. The proposed technique is simple to implement and it does not require a powerful microcontroller which makes it cost effective.