An accurate method for MPPT to detect the partial shading occurrence in a PV system

Abstract

This paper proposes an accurate detection scheme that effectively differentiates the partial shading from the uniform change of irradiance. By doing so, it avoids the unnecessary global peak search which results in a drop of the maximum power point tracker (MPPT) efficiency. The detection is achieved by calculating the irradiance at two designated points on the I-V curve namely, i.e., the short-circuit $(I-{{\text{sc}}})$ and MPP $(I-{{\text{mpp}}})$ currents. Since the mismatch of irradiance at these two points differs greatly for the partial shading and uniform irradiance change, the occurrence of the former is easily discriminated. To prove its effectiveness, the scheme is integrated into perturb and observe and particle swarm optimization MPPT algorithms using a buck-boost converter. Its performance under several partial shading and dynamic shading condition is simulated using MATLAB/Simulink and validated using the dSpace DS1104 platform. It only requires three samples to determine if partial shading occurs; without the scheme, an unnecessary scans of the entire P-V curve is initiated. Consequently, MPPT transient efficiency is increased by 30-35%. In addition to this, the calculated irradiance is utilized to update the open-circuit voltage of the array, thus eliminating the use of temperature and irradiance sensors.