Research Of The Three-port DC-DC Converter Based On Switched Capacitor

Multi-port converter achieves centralized power management and control of the renewable input source, energy storage device and load, with the advantages of low volume and cost, high system efficiency and high reliability. Switched capacitor technique can be introduced into multi-port converter to improve the performance. At present, many converters have been proposed in the literature. However, these topologies contain two inductors, which increase the system volume, cost and electromagnetic problems. And, they can not achieve the bidirectional energy transfer of the storage port.In this paper, a number of novel topologies with switched capacitor are derived based on dual-input single-inductor Buck and Boost converter. The Buck topologies enhance fault tolerance when the renewable source is powered down and reduce the voltage rating of the storage input source. Dual-input Boost topologies enhance the output boost capability. This paper presents the constitution and switched capacitor boost principles of the two kinds of topologies.By comparing the switched capacitor dual-input Buck and Boost converter, the series-connected Buck type topology is chosen as the main research object. And a three-port bidirectional topology for hybrid energy storage system is proposed by introducing an extra path in the dual-input Buck converter. Operation principle and input-output relationship in three modes are given in detail. The thesis also analyzes the switched capacitor performance. In consideration of the circuit parasitic parameters fully, charge-discharge models are established and the influencing factors of the capacitor voltage ripple, charging current and charging efficiency are given. In addition, power management strategy is designed for the renewable energy-battery system. In order to ensure the stability and rapidity of the system, small-signal models in every mode are presented and the decoupling matrixes are used to design closed-loop controller.The operation principle and power management control strategy of the three-port converter are validated through PSIM simulation. Meanwhile, a 240 W prototype is built in the laboratory and the corresponding hardware parameters and software programs are designed. The simulation and experimental results verify the feasibility of the proposed topology and correctness of control strategy.