DC-DC LLC Converter

Open Model

This example shows a DC-DC LLC power converter with frequency control. A simple integral control is implemented in Simulink® in the Controller block, and is designed to achieve a nominal output voltage defined by the variable Vout_nominal. The Output scope shows the frequency control signal, the output voltage, and the reference value for the output voltage. During startup, the reference value is ramped up to its desired setpoint. The design of the LLC powertrain is computed automatically using the first harmonic approximation.

This model contains two variants for the power electronic switches. The detailed version includes a MOSFET with nonlinear characteristics. The abstract version uses a piecewise linear model with an ideal switch, body diode, and output capacitance. The abstract version provides very similar behavior and quicker simulation.

Model

Power Electronic Switch - Detailed Variant

To enable the detailed version, in your model click on "Detailed - MOSFET" . Alternatively, in the MATLAB Command Window, enter:

DCDCLLCConverterSetAbstractDetailed(bdroot,'Detailed');

Power Electronic Switch - Abstract Variant

To enable the abstract version, in your model click on "Abstract - Ideal Switch". Alternatively, in the MATLAB Command Window, enter:

DCDCLLCConverterSetAbstractDetailed(bdroot,'Abstract');

Simulation Results from Simscape Logging

The plot below shows the output voltage as compared to the reference voltage. It also shows the variation in switching frequency as it is adjusted by the control system to track the reference voltage.

The plots below show the behavior of the abstract models and the detailed model. The results are very similar, indicating that the abstract models can be used without a significant loss of accuracy.