Abstract
The modeling approaches of power converters occupy an important position in power electronic systems and have made considerable progress over the past years. Continuous modeling approaches and linearization techniques are reviewed, including the state-space average model, generalized average model, averaged small-signal model, and describing function method. A Buck converter with PWM modulation and voltage-mode control is taken as an example to compare the advantages and disadvantages of different methods through simulation analysis. Moreover, the corresponding equivalent circuit with an intuitive physical meaning of state-space average model, generalized average model, and averaged small-signal model is given. The results point out that the generalized average model can improve the modeling accuracy based on the state-space average model. In the linearization techniques, the averaged small-signal model reflects accuracy at low frequencies, but introduces phase lag in the high-frequency region. The describing function method is derived from harmonic linearization, which takes into account the sideband effect and improves the modeling accuracy at high frequencies.
Highlights
The modeling approaches of power converters occupy an important position in power electronic systems and have made considerable progress over the past years
The average modeling approaches are widely used to average out the switching dynamics in power converters
In order to describe the modeling methods of converter system, a closed-loop voltage-mode controlled continuous conduction mode (CCM) Buck converter with PWM modulation is selected as an example
Summary
Modeling approaches are the basis to study the characteristics and control approaches of power converters. The averaged small-signal model is a good tool for practical controller design for industrial and engineering application This model ignores the switching ripple effect and introduces phase lag in the high-frequency region. Middlebrook et al [19,20] studied the frequency characteristics of current-mode controlled switching converters based on the modeling idea of averaging the inductor current in a switching cycle, but they failed to accurately predict the sub-harmonic oscillation of the system On this basis, Ridley [21] considered the influence of the sample hold link in the peak current control to obtain an improved average model.
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