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Constant Power Load

Constant power load for DC or AC supply

  • Library:
  • Simscape / Electrical / Passive

  • Constant Power Load block

Description

The Constant Power Load block implements a constant power load for a DC or AC supply.

If you set the Load type parameter to DC:

  • The block outputs a nominal rated power as long as the voltage from the DC supply is equal to or greater than the value specified for the Minimum supply voltage parameter.

  • When the voltage from the DC supply drops below the Minimum supply voltage, the load behaviour changes and the block acts as a constant resistance. If the supply voltage becomes negative, the block acts as a constant reverse conductance.

To ensure smooth transitions between these behaviours, the block uses a third-order polynomial spline with continuous derivatives. You can specify the width of this transition using the Transition voltage width parameter.

If you set the Load type parameter to AC:

  • The block outputs a nominal rated power as long as the voltage from the AC supply is equal to or greater than the value specified for the Minimum supply voltage (RMS) parameter.

  • When the voltage from the AC supply drops below the Minimum supply voltage (RMS), the load behaviour changes and the block models a load with constant impedance.

For more information about the equations for the AC load type in a three-phase system, see the Equations section of the Constant Power Load (Three-Phase) block.

Faults

The Constant Power Load block allows you to model an electrical fault as an open circuit. The block can trigger fault events at a specific time.

You can also choose whether to issue an assertion when a fault occurs, by using the Reporting when a fault occurs parameter. The assertion can take the form of a warning or an error. By default, the block does not issue an assertion.

Load-Flow Analysis

If the block is in a network that is compatible with the frequency-time simulation mode, you can perform a load-flow analysis on the network. A load-flow analysis provides steady-state values that you can use to initialize a machine.

For more information, see Perform a Load-Flow Analysis Using Simscape Electrical and Frequency and Time Simulation Mode.

Variables

Use the Variables section of the block interface to set the priority and initial target values for the block variables prior to simulation. For more information, see Set Priority and Initial Target for Block Variables.

Ports

Conserving

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Electrical conserving port associated with the constant power load positive terminal.

Electrical conserving port associated with the constant power load negative terminal.

Parameters

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Main

Type of load. Select DC to use this load with a DC supply or AC to use this load with an AC supply.

Nominal power consumed by the block.

Dependencies

To enable this parameter, set Load Type to DC.

Minimum voltage the DC supply needs to give the block to act as a constant power load.

Dependencies

To enable this parameter, set Load Type to DC.

Value of the reverse conductance when the supply voltage becomes negative.

Dependencies

To enable this parameter, set Load Type to DC.

Transition voltage width used to ensure smooth transitions between the block's behaviours when the supply voltage drops below the Minimum supply voltage or becomes negative.

Dependencies

To enable this parameter, set Load Type to DC.

Active power consumed by the block.

Dependencies

To enable this parameter, set Load Type to AC.

Reactive power consumed by the block.

Dependencies

To enable this parameter, set Load Type to AC.

Rated frequency.

Dependencies

To enable this parameter, set Load Type to AC.

Minimum voltage, in RMS, the AC supply needs to give the block to act as a constant power load.

Dependencies

To enable this parameter, set Load Type to AC.

Faults

Select Yes to enable faults modeling and expose the associated parameters in the Faults section to select the reporting method and specify the time at which the fault triggers.

Choose whether to issue an assertion when a fault occurs:

  • None — The block does not issue an assertion.

  • Warn — The block issues a warning.

  • Error — Simulation stops with an error.

Dependencies

To enable this parameter, set Enable open circuit fault to Yes.

Simulation time when the block enters the faulted state.

Dependencies

To enable this parameter, set Enable open circuit fault to Yes.

Conductance during the open-circuit state.

Dependencies

To enable this parameter, set Enable open circuit fault to Yes.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced in R2020a