A simplified series-parallel structure for the regulated peak power tracking (RPPT) system

Regulated peak power tracking (RPPT) systems such as the series structure and the parallel structure are commonly used in satellite space power systems. However, this structure processes the solar array power or the battery power to the load through two regulators during one orbit cycle, which reduces the energy transfer efficiency. The series-parallel structure for the RPPT system can improve the power conversion efficiency, but an additional regulator increases the cost, size and weight of the system. In this paper, a simplified series-parallel space power system that consists of two regulators is proposed. The proposed system achieves similar energy transfer efficiency with the series-parallel structure by adding one switch to the series structure, which reduces the cost, size and the weight. A single digital signal processor (DSP) is used to control all of the required functions, such as current sharing for the parallel module converter, load voltage regulation, solar array stabilizing, maximum power point tracking (MPPT) and the system operation algorithm of the proposed system. The large signal stability analysis is provided to understand the four main modes of system operation. In order to compare the energy efficiency with a series structure, the simulations are performed and the results are analyzed. The proposed structure saves 11% energy compared to the series structure. Experimental verifications are performed using prototype hardware with a TMS320F2812 DSP and 200 W solar arrays.