Averaged Switch

To prepare models with DC-DC converters for linearization, set the Switching device parameter to Averaged Switch and replace the pulse-width modulation (PWM) signal with a modulation waveform. For a list of converter blocks that support the Averaged switch option, see List of Converter Blocks.

The default value of the Switching device parameter is Ideal Semiconductor Switch. This value results in a model that you cannot linearize exactly because discontinuities occur when the switching devices transition between the on and off states. You can use the Averaged Switch option to reduce the model fidelity and linearize the model.

When you set the Switching device parameter to Averaged Switch, the block models the switching device as a semiconductor switch with an antiparallel diode. The control signal port G accepts values in the interval [0,1]. When G is equal to 0 or 1, the averaged switch is fully opened or fully closed respectively. The switch behaves similarly to the Ideal Semiconductor Switch block with an antiparallel diode. When G is between 0 and 1, the averaged switch is partly opened. You can average the PWM signal over a specified period. You can then undersample the model and use modulation waveforms instead of PWM signals.

After you set the Switching device parameter to Averaged Switch and replace the PWM signal with a continuous signal, you can linearize your model. For example, you can use the linmod function. You can also use the steady state as an operating point that is suitable for linearization. For more information about the linearization techniques that you can now apply, see Linearization Techniques.

As an alternative to using blocks that support the Averaged switch option, you can use low-fidelity, average-value converter blocks. You can linearize models that contain these blocks. For a list of average-value converter blocks, see List of Converter Blocks.

For more complex models with discontinuities, you can estimate a linear model by running a dynamic simulation. For more information, see Estimate Linear Models from Simulation Results.

Examples

The Linearize DC-DC Converter Model example shows how to linearize a model of a DC-DC converter using averaged switching or an average-value converter.

These examples show how to use different levels of fidelity in DC-DC converters. In both examples, the lowest fidelity model with averaged switches and modulation waveforms is suitable for linearization, and you can use the steady state as an operating point.

The DC-DC Converter Model Fidelity Comparison example shows how to use different levels of fidelity in a Buck-Boost converter:

The Bidirectional DC-DC Converter Current Control example shows how to control the inductor current of a bidirectional DC-DC converter. The Bidirectional DC-DC Converter block uses averaged switches. To achieve different levels of fidelity, you can use gate pulses, averaged gate pulses or modulation waveforms.

List of Converter Blocks

You can use the Averaged switch option in these blocks to linearize models:

Alternatively, you can use these low-fidelity, average-value blocks for linearization.