Cuk Converter with Integrated Magnetics

Overview

This model highlights the PLECS magnetic domain components using a complex isolated Ćuk converter which is capable of zero-ripple operation. A more thorough analysis and discussion of this demo model can be found in [1].

Fig. 1 Ćuk converter with integrated magnetics

Model

Due to a proper winding turn-ratio, this Ćuk converter can achieve zero ripple in both input and output currents. The magnetic circuit consists of two opposing E-cores spaced by air gaps. These air gaps are represented with three permeances \(P_{\mathrm{g1}}\), \(P_{\mathrm{g2}}\) and \(P_{\mathrm{g3}}\). The two chokes and the transformer are combined into a single magnetic structure modeled as separate permeances \(P_{\mathrm{1}}\), \(P_{\mathrm{2}}\) and \(P_{\mathrm{3}}\). The leakage fluxes are bundled and simplified to a single flux path \(P_{\mathrm{4}}\).

Simulation

In this example, the core material saturates around \(0.4\) Tesla leading to spikes in the output current. The spikes occur when the magnetic flux in the output leg \(P_{\mathrm{3}}\) gets close to \(5\,\mu\mathrm{Wb}\). Increasing \(B_{\mathrm{sat}}\) to \(0.5\) Tesla removes the output current ripple (as does replacing Saturable Core components with Linear Cores).

Conclusion

The permeance-capacitance analogy implemented in PLECS provides an intuitive and geometry-based approach to modeling magnetic circuits like the one for this Ćuk converter.

Bibliography

[1]

J. Allmeling, W. Hammer and J. Schönberger, Transient simulation of magnetic circuits using the permeance-capacitance analogy, 2012 IEEE 13th Workshop on Control and Modeling for Power Electronics (COMPEL), Kyoto, 2012, pp. 1-6.