A Single Cell Maximum Power Point Tracking Converter without a Current Sensor for High Performance Vehicle Solar Arrays

A maximum power tracker is developed for a single high performance GaAs solar cell to reduce the impact of variations in cell illumination for highly curved arrays as required for vehicle applications. This solution also finds applications in concentrating photovoltaic systems where the incident energy may vary due to optical imperfections. On a curved array, each cell has a directly connected tracker that operates autonomously. An examination of the switching ripple performance of a large number of series connected asynchronous converters is made. The tracker uses a highly efficient 600 mW buck converter operating at 20 kHz with a synchronous rectifier. A dedicated MSP340 processor is capable of the total converter control task. Operating at 1.8 V the controller can be directly powered by the cell. A charge pump is used to develop gate drive voltages for the converter MOSFETs. A maximum power tracking algorithm based on observations of cell voltage and converter duty cycle is demonstrated. The load power may be maximized by maximizing the converter average output voltage. An interior voltage loop is used to control cell voltage and assists in securing a 1.5 mS response to illumination change