Dynamic Load

Dynamic load for DC or AC supply

Since R2020b

• 

Libraries:
Simscape / Electrical / Passive

Description

The Dynamic Load block implements a dynamic load for a DC or AC supply.

If you set the Load type parameter to DC:

• The consumed power of the block is equal to the P port as long as it is greater than the value of the Minimum consumed power parameter and 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 resistive load. If the supply voltage becomes negative, the block acts as an open circuit 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, this table shows the relationship between the voltage from the AC supply, V, the active power at the P port, P_in, and the consumed active power of the block, P_actual:

Applicable Range of V Values	Applicable Range of Pin Values	Corresponding Consumed Active Power
$$V>V_{\min }$$	$$P_{in}>P_{\min }$$	$$\begin{array}{l}{P}_{actual}=P_{in}\\ Q_{actual}=Q_{in}\end{array}$$
	$$P_{in}<P_{\min }$$	$$P_{actual}=P_{\min }$$
$$V<V_{\min }$$	$$P_{in}>P_{\min }$$	The block models a load with an impedance equal to:$$\begin{array}{l}R=V_{\min }^2\frac{P_{in}}{P_{in}^2+Q_{in}^2}\\ X=V_{\min }^2\frac{Q_{in}}{P_{in}^2+Q_{in}^2}\\ Z=\sqrt{R^2+X^2}\end{array}$$
	$$P_{in}<P_{\min }$$	$$P_{actual}=P_{\min }$$

Where:

• V_min is the value of the Minimum supply voltage (RMS) parameter.

• P_min is the value of the Minimum active power parameter.

• P_actual is the consumed active power of the Dynamic Load block.

• Q_actual is the consumed reactive power of the Dynamic Load block.

The consumed reactive power of the block is equal to the Q port 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. Otherwise, the block models a load with an impedance equal to:

$$\begin{array}{l}R=V_{\min }^2\frac{P_{in}}{P_{in}^2+Q_{in}^2}\\ X=V_{\min }^2\frac{Q_{in}}{P_{in}^2+Q_{in}^2}\\ Z=\sqrt{R^2+X^2}\end{array}$$

.

Faults

The Dynamic 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.

Ports

Input

P — Real power

physical signal

Physical signal port associated with real power, specified as a scalar.

Q — Reactive power

physical signal

Physical signal port associated with reactive power, specified as a scalar.

Conserving

+ — Positive terminal

electrical

Electrical conserving port associated with the dynamic load positive terminal.

- — Negative terminal

electrical

Electrical conserving port associated with the dynamic load negative terminal.

Parameters

Main

Load type — Load type

DC (default) | AC

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

Minimum supply voltage — Minimum DC supply voltage

20 V (default) | scalar

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.

Minimum consumed power — Minimum consumed power

1e-3 W (default) | scalar

Minimum amount of power consumed by the block.

Dependencies

To enable this parameter, set Load Type to DC.

Reverse conductance — Reverse conductance

1e-6 S (default) | scalar

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

Dependencies

To enable this parameter, set Load Type to DC.

Transition voltage width — Transition voltage width

1e-3 V (default) | scalar

Transition voltage width. This value is 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.

Rated frequency — Rated frequency

60 Hz (default) | scalar

Rated frequency.

Dependencies

To enable this parameter, set Load Type to AC.

Minimum supply voltage (RMS) — Minimum AC supply voltage

200 V (default) | scalar

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

Dependencies

To enable this parameter, set Load Type to AC.

Minimum active power — Minimum active power

1e-3 W (default) | scalar

Minimum active power of the block.

Dependencies

To enable this parameter, set Load Type to AC.

Faults

Enable open circuit fault — Whether to enable fault modeling

Off (default) | On

Select On to enable fault modeling and expose the associated parameters in the Faults section, which enables you to select the reporting method and specify the time at which the fault triggers.

Reporting when a fault occurs — Whether to issue assertion when fault occurs

None (default) | Warn | Error

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 On.

Simulation time for fault event — Time before entering faulted state

1 s (default) | scalar

Simulation time when the block enters the faulted state.

Dependencies

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

Open-circuit conductance — Open-circuit conductance

1e-4 S (default) | scalar

Conductance during the open-circuit state.

Dependencies

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

Extended Capabilities

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

Version History

Introduced in R2020b