Improved MPPT Methods for PV Array Under Patrially Shaded Condition

Abstract

Under partially shaded conditions PV string exhibits complex output characteristics, i.e., the current-voltage curve (I-V) shows multiple current stairs whereas power –voltage (P-V) curves presents multiple voltage peaks. Therefore the use of conventional maximum power point tracking is not beneficial in the case of tracking accuracy or on tracking speed. This paper introduces two global MPPT methods one is search-skip-judge global MPPT(SSJ-GMMPT) and another is rapid global MPPT (R-GMPPT) methods. These two methods proposed helps to reduce searching voltage range based on study of I-V and P-V characteristics of P-V string. The real maximum power under any shading condition can be tracked by SSJ-GMPPT and therefore high accuracy and rapid tracking speed can be achieved without any additional circuits and sensors. The tracking speed of long string having huge PV modules can be improved by R-GMPPT methods which degrades more than 90% of tracking time that is required by conventional global searching method. Comparing these two propose method with other methods highlights that these proposed methods are good and powerful.