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This paper describes the control of a pulse width modulated (PWM) type sequential shunt switching unit (SSU) for spacecraft applications. It is found that the solar cell output capacitance has a significant impact on SSU design. Shorting of this cell capacitance by the PWM switch causes input current surges. These surges are minimized by the use of a series filter inductor. The system with a filter is analyzed for ripple and the control to output-voltage transfer function. Stable closed loop design considerations are discussed. The results are supported by modeling and measurements of loop gain and of closed-loop bus impedance on test hardware for NASA's 120 V Earth Observation System (EOS). The analysis and modeling are also applicable to NASA's 160 V Space Station power system.

A novel integrated battery charger/discharger converter for a standardized battery module is proposed. Instead of using separate charger and discharger converters, it integrates these two converters into a single converter in order to minimize the size. The integrated charger/discharger converter not only regulates the solar array output power including the peak power tracking capability but also controls the battery charging/discharging current depending on the solar array output power and the load power. In addition, it offers a regulated bus voltage that simplifies the power distribution/conversion for the payload.