Desigan,Implementation And Optimization Of MPPT-based EPS For Micro-Satellites

Compared to traditional satellites, the micro-satellite with the advantages of high functional density, high technology property, high flexibility, low investment and operation cost, short R&D cycle, has great potential in the development of satellite. After ZDPS-1A successfully lauched and five years later, ZDPS-2 satellite developed by Zhejiang University, which has better performance, higher index, more complex, was also successfully lauched in September 20,2015. Now ZDPS-2 has operated normally on orbit over three months and its power system performs well. Based on ZDPS-2's power system's design and to improve its performance, a new design of power system based on mppt with a small size, high efficiency, high reliability has been proposed.This thesis first briefly introduces the components of ZDPS-2's power system and the design idea of these components. Then, the design of the MPPT module of ZDPS-2's power system is introduced in detail, which is called single-mode MPPT. Single-mode MPPT used the Perbutitation and Orbersevation(P&O) Method as the MPPT controlling algorithm, FSBB (Four-Switch Buck-Boost) topology as the power circuit of MPPT, and the main control tube working at the same time as the operate mode. Ground and on-orbit test results showed that the single-mode MPPT tracking efficiency was above 98% and the tracking speed was less than 1s. However, the power circuit's efficiency was only 71% to 87%, which resulted in the low output power of MPPT.Aimed at the problem of low efficiency of single-mode MPPT's power circuit, this thesis puts forward an improved scheme called three-mode MPPT. Theoretic analysis and experiment validated this scheme. Three-mode MPPT changes the operating mode of the main control tube working at the same time to switch among three modes of Buck, Boost and direct connection. Test results showed that the three-mode MPPT's tracking efficiency and speed is almost equal to that of the single-mode, and the power circuit efficiency is increased by more than 10%.