Modeling of high frequency resonant inverter system in phasor domain for fast simulation and control design

Abstract

The full-bridge resonant converters use various modulation schemes for different control purpose. The circuit modeling and analysis are complicated for these converters because the state variables like inductor currents and capacitor voltages are ac dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonics of interest. Correspondingly, the resonant converter is decomposed into two dc sub-circuits, the state variables of which are the time-varying Fourier coefficients of the original ac variables. Small signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A general phasor dynamic model is presented for a family of high frequency DC/AC resonant inverter system with 5 energy storage components. The advantages of this model over the other models include: 1) The mathematical model closely relates to the power converter topology in time domain, and therefore keeps the physical meaning of the state variables. The active power, reactive power, etc, can be easily defined. 2) Also the model can be easily derived from the topology in time-domain. Therefore this model can be easily extended to more complicated resonant topologies, and to include more parasitical components for higher accuracy of modeling. 3) The model can be applied to a number of modulations including phase shift modulation, frequency modulation, pulse width modulation, and pulse width modulation with minor modifications. 4) It can be used for fast simulation, circuit analysis and controller design. A resonant inverter system with 5 energy storage elements are modeled and compared with switch simulation for both steady state and transients. The simulation results match the switch simulation in both steady state and transients, but takes much less time.