Boundary Selection Of Hybrid System For Bi-directional DC-DC Switching Converter

Bi-directional DC-DC converter is the converter which can operate in two-way quadrants, achieving bi-directional energy flow, as one of the characteristics of dual-purpose machine, it can significantly reduce system size, weight and cost with a high research value. In aerospace, electric cars, back-up power, distributed generation, renewable energy and other fields, Bi-directional DC-DC switching converter have broad application prospects. Based on electronic circuits, switching devices make the topology of the circuit no longer fixed, so a typical power electronic circuits are switched linear system, which is also called hybrid system.This paper first studies the structure system of Bi-directional DC-DC switching converter, which is divided into Buck and Boost mode, the paper established the mathematical model of this converter according to Kirchhoff's voltage and current laws, while analyzing the controllability of inductive current continuous and inductor current discontinuous mode.Based on hybrid systems theory, a DC-DC converter model of hybrid automata is established, the switching control problem is simplified to the boundaries selection of hybrid automaton model without any assumptions and the linear approximation. The circuit method and energy method are used to design of boundary conditions of Bi-directional DC-DC converter.Based on circuit theory methods, the boundary conditions of Bi-directional DC-DC switching converter is studied in inductor current continuous mode and inductor discontinuous mode. In energy methods, based on the principle of conservation of energy, the reference voltage and reference current is introduced to analyze the boundary condition in current discontinuous mode.The circuit algorithm and energy algorithm is implemented by using the Simulink platform and Simpower system platform and extensive simulations are carried out to check the validity of algorithm, and the simulation results verify the effectiveness of two algorithms for control of Bi-directional converterFinally, the control algorithm is verified in the prototype of the bi-directional DC-DC converter. Experimental results show that the validity of boundary selection in hybrid system of Bi-directional converter. The system can operate effectively in both Inductor current continuous mode and discontinuous mode, while the algorithm for load and input voltage disturbances has very good inhibition.