In general, satellite electrical power system plays an important role in its mission performance. To perform the mission successfully, the satellite should be provided with the sufficient power until End-of-Life (EOL). To supply the sufficient power, it is not easy to install of larger power generation and storage source with power control units on satellite. Also, the thermal control is difficult in the space. The various technologies have been developed to reduce the satellite power sizing and to design power efficiently. The peak power tracking (PPT) method has been developed for spacecraft power system to use maximum available power of solar array. In general, to compensate for the solar cell's degradation at EOL in satellite, the solar array will be designed with big enough margin. And, when the spacecraft exits eclipses, the peak output power of a solar array becomes very higher than its peak output power in the normal sunlight operation power. As a result, the spacecraft power system should dissipate high excess power through shunt regulators in the beginning of mission and after eclipse exit. To avoid the high power dissipation in the beginning of life and to utilize maximum available power after eclipse exit, the PPT is used in many recent spacecraft. Particularly, this PPT method is useful for the spacecraft in lower orbit because it goes through a large number of eclipse.
