An Active Switching Circuit for Solar Cells

Abstract

The electrical output of a solar panel can be optimised in several ways, through the inclusion of bypass diodes (BPDs) or to have a maximum power point (MPP) tracker or DC optimiser to ensure that the panel is always operating at its global MPP. However most of these systems have to be implemented externally to the panel. A new system, the active switching circuit was proposed as a means to actively sense shading and switch between three wiring configurations drawing inspiration from matrix converter theory. The active switching circuit prototype would operate for 16 solar cells arranged in a 4 x 4-cell solar panel and be able to change the wiring configuration of these sixteen cells using switches. The base unit of the solar panel is a substring composed of four solar cells in series and the circuit would switch between three wiring configurations. The shading would be measured through four current sense resistors and amplifiers, with one of these pairs in each substring and a differential operational amplifier system to measure the voltage across the strings. The current and voltage measurement helps determine the power output of the panel. A Simulink model of the system was first created and a panel with 4 x 4 solar cell arrangement ordered and then measurements made with shading to verify if the shading model was accurate. From these results a Simulink model for the active switching circuit was designed to test the theory of its functionality and if such a circuit could be controlled to switch between the three wiring configurations. The circuit was successfully built and was able to operate in its intended way.