This paper reviews some of the major approaches to modeling and simulation in power electronics, and provides references that can serve as a starting point for the extensive literature on the subject. The major focus of the paper is on averaged models of various kinds, but sampled-data models are also introduced. The importance of hierarchical modeling and simulation is emphasized.

Modeling and simulation of power electronic converters

The controller in a pulse-width-modulation (PWM) power converter has to stabilize the system and guarantee an almost constant output voltage in spite of the perturbations in the input voltage and output load over as large a bandwidth as possible. Boost and flyback power converters have a right-half-plane zero (RHPZ) in their transfer function from the duty cycle to the output voltage, which makes it difficult to achieve the aforementioned goals. Here, the authors propose to design a controller using H/sup /spl infin// control theory, via the solution of two algebraic Riccati equations. The almost optimal H/sup /spl infin// controller is of the same order as the converter and has a relatively low DC gain. The closed-loop characteristics of a typical low-power boost power converter with four different control schemes were compared by computer simulation. The H/sup /spl infin// control was found to be superior in a wide frequency range, while being outperformed by the others at extremely low frequencies. Good agreement was found between simulation results and experimental measurements.

H/sup /spl infin// control applied to boost power converters

A general and unified large signal averaged circuit model for current programmed DC-to-DC converters is proposed. In the averaged circuit model, the active switch is modeled by a current source, with its value equal to the averaged current flowing through it, and the diode is modeled hy the voltage source, with its value equal to the averaged voltage across it. The averaged circuit model has the same topology as the switching converter. The large signal averaged circuit model for current programmed buck, boost, buck-boost and Cuk converters are proposed, from which the large signal characteristics can be obtained. The steady-state and small signal transfer functions of the current programmed DC-to-DC converters can all be derived from their large signal averaged circuit models. The large signal characteristics of the current programmed buck converter are studied by both the phase plane trajectory and the time domain analysis. Experimental prototypes for a current programmed buck converter, with and without an input filter, are breadboarded to verify the analysis. >

A general unified large signal model for current programmed DC-to-DC converters

Average modeling of PWM power converters is reexamined in the light of the behavioral dependent sources now included in modern versions of electronic circuit simulators. A topology independent behavioral model is developed to emulate the operation of PWM converters in voltage and current modes, for continuous and discontinuous inductor current cases. It is shown that, in general, the operation of the switching part involves three behavioral blocks, i.e., the generic switched inductor model (GSIM), the duty cycle generator (DCG), and the inductor current generator (ICG). Explicit expressions and equivalent circuits are developed for all possible modes of operation. >

Average simulation of PWM converters by direct implementation of behavioral relationships

Subharmonic oscillation of a generic fixed-frequency current-programming switch mode power converter (SMPC) operating in the continuous-conduction mode (CCM) is analyzed. The conditions for oscillation are derived by the geometric approach as well as by analyzing the converter in the discrete time domain and are shown to be equivalent. In obtaining the state-space averaged differential equation, the forward Euler approximation is invoked. This z/spl rarr/s transformation maps a z-domain pole outside the unit circle that causes the oscillation to a s-domain pole in the left-half plane (LHP), which has previously been overlooked. The analysis is then applied to a current-programming buck converter, which suggests the two correct control equations for both converters employing either trailing- or leading-edge modulation.

Analysis of subharmonic oscillation of fixed-frequency current-programming switch mode power converters

A SPICE simulation model of current-mode pulse-width modulation (PWM) converters operating in the continuous mode is described and tested against analytical expressions and experimental data for buck and boost converters. The simulation model is also used to compare an earlier average model to a recently suggested modification and to examine the effect of the gain factor in the current feedback path. >

D. Kimhi

Papers

A SPICE model for current mode PWM converters operating under continuous inductor current conditions