Research On Three-port DC-DC Converter Based Spacecraft Distributed DC Power System

The spacecraft power system consists of three parts: photovoltaic(PV)source,energy storage and output load.Using an integrated three-port converter(TPC)replaces multiple two-port converters can increase system power density and reduce conversion stages,thereby improving the system efficiency and reducing the total cost.In addition,building a modular,distributed and expandable system with TPC as the basic power unit is an important way to improve the power capacity and reliability of the spacecraft power system.How to realize the power control of multiple TPC modules is an important problem that needs to be solved.In this paper,a non-isolated TPC based on the integrated of non-isolated bidirectional Buck/Boost converter and full-bridge converter is studied.The decoupling control of each port of TPC is realized by PWM plus phase shift modulation strategy.The working principle,power transmission characteristics and soft switching characteristics of the TPC are analyzed in detail.The parameter design considerations are expounded.The correctness of the theoretical analysis and the feasibility of the control strategy are verified by the 500 W experimental prototype.On this basis,the TPC-based distributed three-port output parallel system architecture and its strategy are studied.The critical load power is shared by multiple distributed TPC subsystems in parallel and the reliable power supply is achieved.The article analyzes the system working state and control requirements in detail,and analyzes the current sharing control scheme of system based on the droop method.The correctness of the theoretical analysis is verified by experiments with two TPCs in parallel.Furthermore,aiming at the scalability requirements for power system of large spacecraft,a distributed DC power supply system architecture based on modular TPC is studied.The demand of PV sources power utilization and batteries state of charge balancing for subsystem is analyzed.An output power control strategy that can simultaneously consider the energy states of each PV source and battery is introduced.The voltage information of the PV and the battery ports is introduced into the droop coefficient to maximize the utilization of PV sources,and balance the state of charge of each battery.Thereby improving the reliability and stability of the system,and optimizing the power of each port under different working conditions.It was verified by experiments with two TPCs in parallel,and the results proved the correctness of the theoretical analysis and the effectiveness of the strategy.