Investigation Of Modeling And Control For Power Electronic Circuits Based On Hybrid System

Nowadays, owe to excellent switching on and off ability of power electronic devices, they are widely used in all kinds of power converter circuit. Nevertheless, the power electronic devices are operated in switching mode all the time, there may be sets of subsystems in one circuit because of switching, and the classic circuit theory is not suitable to analyze these topologies. How to model the power electronic circuit properly and how to derive their stability condition is a research direction of power electronics.Power electronic systems can be viewed as typical hybrid systems, so their stability problems can be researched through hybrid system theory. Base on the theory, this dissertation investigates modeling for power electronic circuits and robust covariance control with uncertain parameters. The main contributions of this dissertation are as follows.(1) Large signal models based on hybrid system for second-order DC/DC converters (such as Buck, Boost, Buck-Boost, Flyback, Forward converter etc.) which operate at CCM mode are proposed. Expression standing for energy stored in the passive components is used as Lyapunov function. Inner product of vectors is viewed as time derivative. Direct method of Lyapunov is used to derive the sufficient condition for the system, which is satisfied through sliding mode like control strategy. The strategy is validated by simulations and experiments on Boost converter controlled by DSP.(2) Considering load resistance as uncertain parameter of system, the differential equation is established based on hybrid system theory. The Taylor expansion is used to divide matrices of system into certain and uncertain parts. Averaged method is applied to derive the small signal model. Linear matrix inequality (LMI) standing for the stability of system is obtained according the robust covariance control theory and is solved by MATLAB LMI toolbox, so the control parameters based on state feedback are obtained. Simulation and experiments on Buck converter shows that the system behaves robust with the control parameters.(3) By use of equivalent circuit transformation, the half-bridge is transformed into a continues state system without switches, the large signal is derived, transfer function is proposed and the PID controller design method is suggested.