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The Nonlinear Model Library

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How to Access the Nonlinear Model Library The Continuous Library The Discrete Library The Phasors Library The Switch Current Source Library Limitations of the Nonlinear Models Modifying the Nonlinear Models of the powerlib_models Library

How to Access the Nonlinear Model Library

The building blocks used to assemble the Simulink model of the nonlinear circuit are stored in a library named powerlib_models. You do not normally need to work with the powerlib_models library. You can access that library by entering powerlib_models in the MATLAB Command Window.

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The Continuous Library

The Continuous library contains blocks that use voltage inputs (output of the state-space model of the linear circuit) and their current output is fed into the state-space model. For complex models, such as electrical machines requiring several inputs and outputs, vectorized signals are used. Useful internal signals are also returned by most of the models in a measurement output vector m.

For example, the Asynchronous Machine model is stored in two blocks named asynchronous_machine (electrical model) and ASM_mechanics (mechanical model). The electrical model uses as inputs a vector of four voltages, two rotor voltages and two stator voltages, respectively: (VabR, VbcR, VabS, VbcS). It returns a vector of four currents, two rotor currents and two stator currents, respectively: (IaR, IbR, IaS, IbS). The model also returns a measurement output vector of 20 signals. When the Asynchronous Machine block is used from the powerlib library, this measurement output vector is accessible through the m output of the machine icon. You can get details on the model inputs and outputs from the documentation of powerlib and powerlib_models block icons.

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The Discrete Library

The Discrete library contains the discrete versions of the continuous models described above.

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The Phasors Library

The Phasors library contains the phasor versions of some of the continuous models described above. See Getting Started for more details on the phasor simulation.

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The Switch Current Source Library

The Switch Current Source library contains models of power electronic devices with an internal inductance Lon > 0. Al these continuous models are simulated by a current source external to the linear circuit. These devices are the diode, thyristor, gate-turnoff thyristor (GTO), metal-oxide-semiconductor field-effect transistor (MOSFET), and the insulated-gate-bipolar transistor (IGBT). As for electrical machines, these models use a voltage input (output of the state-space model of the linear circuit) and their current output is fed into the state-space model. All these models are vectorized.

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Limitations of the Nonlinear Models

Because nonlinear models are simulated as current sources, they cannot be connected in series with inductors and their terminals cannot be left open.

If you feed a machine through an inductive source, power_analyze prompts you with an error message. You can avoid this by connecting large resistances in parallel with the source inductances or across the machine terminals.

A series RC snubber circuit is included in the model of the Breaker block and power electronics blocks. You should not have any problems if you keep these snubber circuits in service. The snubber can be changed to a single resistance by setting Cs to Inf, or to a single capacitor by setting Rs = 0. To eliminate the snubber, specify Rs = Inf or Cs = 0.

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Modifying the Nonlinear Models of the powerlib_models Library

We do not recommend to modify the powerlib_models library. However you can use the models as a starting point to create your own version of the models. Use the technique described in Building and Customizing Nonlinear Models.

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Increasing Simulation Speed

Creating Your Own Library of Models

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