Robust H_∞Controller Design Of A DC/DC Converter Based On An LPV Model

With the development of control technology, many scholars have studied the controlmethod of DC/DC converters. The linear control method as PI and PID control hasbeen widely applied to the actual system, but there is slow dynamic response, poor control,difficult to optimize control characteristics shortcomings. In addition, theadvanced control method such as one cycle control, sliding mode variable structure control,adaptive control, the LQ and LQG have also been applied. However, the above method is notideal for anti-jamming capability and system parameters changing robustness. The highfrequency chattering phenomenon even makes the system unstable.In essence, the DC/DC convert is a nonlinear multivariable system, should research thecontrol strategy based on the nonlinear control theory. In recent years, with the developmentof robust control, linear varying parameters (LPV) control has been the rapidly developmentand in deal with nonlinear systems has acquired some results. This article puts forward arobust H∞controller design method which deploys the closed-loop pole to a region in order tomeet the dynamic response and system stability. Using the LPV convex decompositionmethod, puts the system model into the polytopic LPV model with a convex polyhedronstructure. Then using linear matrix inequalities (LMI) approach to design feedback controllerto meet the requirements of H∞performance and closed-loop poles placement. The paper isorganized as follows:First, compared the methods of the previous paper for designning DC/DC controllers,and summarizes their advantages and disadvantages. Introduces the development of robustcontrol theory and LMI technique, on this basis，proposes the design method have used in thispaper, and discusses the purpose and significance of this method.Second，introduces related concepts and theories. Focus on the LMI technique, regionalpole placement method and robust control theory essence, after that, obtains the LMIequations in the case of taking into account the specified H∞performance and the poleplacement to make system with a reasonable degree of attenuation, damping characteristicsand adjust time of the system.Third, modeling the nonlinear DC/DC system with state space averaging method, when analysis the Buck converter, using the appropriate method have obtain linear model of thesystem small signal model, and introducing the new state variable representing the integral ofthe error between desired output value and the actual output value, finally using LPV modelto represent the uncertain time-varying systems.Finally, compared the H∞controller with the traditional PID controller, Matlabsimulation results shows that the H∞controller can make the system has good dynamicperformance and stability. At the same time, the system still maintain robustness when theload change, outside interference exist and system architecture parameters change, but thetraditional controller can not get the same control effect, the system performance is relativelypoor.