Steady-State Process Analysis of DC Converter Based on Equations Expansion

The paper deals with processes analysis in circuits of converter working on a time-varying load. A control of inverter and load switches are realised by signals with incommensurable frequencies. Processes in such a system are described by differential equations with periodical coefficients. Steady-state periodic solutions can be obtained by the extension of ordinary differential equations with one independent time variable into partial differential equations with two independent variables of time. These equations are solved by use of the Galerkin method with trigonometric basis and weight functions. The results of calculations of the steady-state process for a buck-boost converter are presented in form of the double Fourier series. They are compared with results obtained in the way of numerical calculation of differential equations for a transient process. Extended equations are also solved by a generalized state-space averaging method. A balance of active power in circuits of converter with the time-varying load is shown.