PHOTOVOLTAIC MODULE AND SHADOW: STUDY AND INTEGRATION OF A CURRENT BALANCING SYSTEM

International audienceCurrent crystalline photovoltaic modules (PV) are designed with 36 or 72 series – connected PV cells. Usually, in order to protect the PV cells, a bypass diode is connected in anti-parallel every 18 PV cells. Furthermore, the series connection of PV modules is necessary in order to obtain the input voltage for the converter. Yet, each PV cell has its own current-voltage characteristic. The manufacturers guarantee a dispersion of 3% of maximum power between solar cells; so series connection of heterogeneous PV cells generates mismatch losses. Mismatch losses can increase in case of shading which may greatly reduce power output. Moreover, building integrated PV (BIPV) has seen an important development in urban areas bringing to the light shadow related problems. This paper proposes a PV module with an integrated power electronics topology able to replace bypass diodes while extracting maximum power of each 18 PV cell string. The operating principle of the current balancing system (CBS) is studied with multiple input levels and various PV generator characteristics. Five different layouts of the CBS are studied using a 144 PV cell string subdivided in 18 cell groups which are submitted to 21 shade scenarios. Furthermore, the optimal CBS can be implemented easily into current 72 cell modules. Experimental results on a prototype are compared to simulation results in chosen shade conditions. The performance analysis carried out shows interest in using the 4 input level CBS rather than traditional bypass diode modules