Design and Implementation of the Power Electronic System for the Lunar Zebro rover

Abstract

The small and lightweight Lunar Zebro rover must survive in the harsh lunar environment for several Earth days following its moon landing. The mission of the rover is to map the radiation environment on the moon. The success of the entire mission depends on the Power Electronic System (PES), which supplies power to all subsystems and charges the batteries using solar panels. The current PES of the Lunar Zebro rover does not comply with all mission-specific requirements and does not perform satisfactorily when integrated into the rover. Therefore, the need for a reliable PES that conforms to all requirements arises for the Lunar Zebro rover.

In this research, the design and implementation of an efficient, compact, and redundant PES for the Lunar Zebro rover is developed. First, the optimal Direct Current (DC) bus is designed to obtain a system with the highest efficiency. This is done by modelling the efficiency of the DC/DC converters for different bus voltages and estimating the overall losses in these converters during the deployment of the rover. Moreover, the effect of the bus voltage on the size of the passive components is investigated, and the bus voltage resulting in the most compact system is obtained. It is found that a 12 V bus results in the most efficient and compact system. No additional converter is required that regulates the 12 V output, and the inductance required for each converter is decreased compared to higher bus voltages.

Besides the DC bus design, redundancy methods are compared to obtain the best tradeoff between redundancy and footprint added. The two-phase interleaved converter was found to have only an 8.59% increase in footprint compared to single-phase converters, while failure in a switch, diode, input capacitor, and output capacitor are accounted for in each converter. Finally, the mode of operation that results in the highest efficiency is obtained by designing each converter and modelling the corresponding losses for Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM) operation. For both the single-phase and two-phase interleaved converters hold that operating in CCM results in a significant increase in efficiency compared to DCM operation. Moreover, the PES utilising two-phase interleaved converters is more efficient during rover operation than the single-phase counterpart. However, charging is less efficient than for the single-phase counterpart. Simulink and LTspice simulations have been carried out to verify the operation of each converter. Finally, experiments on a functional prototype are carried out to provide experimental validation of the design.