Dynamic Load (Three-Phase)

Balanced three-phase dynamic load

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Libraries:
Simscape / Electrical / Passive

Description

The Dynamic Load (Three-Phase) block models a balanced dynamic load for a balanced three-phase supply.

This table shows how the block calculates the consumed active and reactive power based on the voltage from the supply, V.

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

In these equations:

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

• P_actual is the consumed active power of the Dynamic Load (Three-Phase) block.

• P_in is the input active power of the Dynamic Load (Three-Phase) block, determined by external input port P.

• Q_actual is the consumed reactive power of the Dynamic Load (Three-Phase) block.

• Q_in is the input reactive power of the Dynamic Load (Three-Phase) block, determined by external input port Q.

The Dynamic Load (Three-Phase) block consumes or generates active power depending on the polarity of input active power P_in. If P_in > 0, the block consumes active power. If P_in < 0, the block generates active power.

Faults

To model a fault in the Dynamic Load (Three-Phase) block, in the Faults section, click the Add fault hyperlink next to the fault that you want to model. In the Add Fault window, specify the fault properties. For more information about fault modeling, see Fault Behavior Modeling and Fault Triggering.

The Dynamic Load (Three-Phase) block allows you to model an electrical fault as an open circuit. The block can trigger fault events at a specific time.

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, W

physical signal

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

Q — Reactive power, V*A

physical signal

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

Conserving

~ — Three-phase voltage

electrical

Composite three-phase port associated with the three-phase voltage.

Dependencies

To enable this port, set Electrical connection to Composite three-phase ports.

a — Phase A voltage

electrical

Expanded three-phase port associated with the phase A voltage.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

b — Phase B voltage

electrical

Expanded three-phase port associated with the phase B voltage.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

c — Phase C voltage

electrical

Expanded three-phase port associated with the phase C voltage.

Dependencies

To enable this port, set Electrical connection to Expanded three-phase ports.

Parameters

Main

Electrical connection — Electrical connection

Composite three-phase ports (default) | Expanded three-phase ports

Whether to model composite or expanded three-phase ports.

When you select Composite three-phase ports, the ~ conserving port represents a composite three-phase port.

When you select Expanded three-phase ports, the a, b, and c conserving ports represent the individual phases of a three-phase system.

Rated electrical frequency — Rated electrical frequency

60 Hz (default) | positive scalar

Since R2023a

Rated electrical frequency.

Minimum supply voltage (phase-to-phase RMS) — Minimum supply voltage

100 V (default) | scalar

Minimum voltage, in phase-to-phase RMS, that the supply needs for the block to act as a dynamic load.

Voltage time constant — Voltage dynamics time constant

0.01 s (default) | positive scalar

Since R2023a

Time constant associated with the transients of the terminal voltage measurement.

Initial supply voltage (phase-to-phase RMS) — Initial terminal voltage

200 V (default) | positive scalar

Since R2023a

Terminal voltage, in phase-to-phase RMS, at time zero.

Initial supply voltage angle — Terminal voltage angle of phase A at time zero

0 deg (default) | scalar

Since R2023a

Terminal voltage angle of phase A at time zero.

Parasitic conductance to electrical reference — Parasitic conductance to electrical reference

0 S (default) | nonnegative scalar

Since R2023a

Parasitic conductance to electrical reference.

Faults

Open circuit fault — Option to add open circuit fault

Add fault (default)

Option to add an open-circuit fault in the Dynamic Load (Three-Phase) block.

To add a fault, click the Add fault hyperlink.

Open-circuit conductance — Open-circuit conductance

1e-4 S (default) | scalar

Conductance during the open-circuit state.

Dependencies

To enable this parameter, add a fault to the Dynamic Load (Three-Phase) block by clicking the Add fault hyperlink in the Open circuit fault parameter.

After you create the fault, you can change the properties in the Fault Inspector window. When you open a block that has a fault, the Open Fault Inspector hyperlink appears instead of the Add fault hyperlink. For an example that shows how to include faults, see Analyze a DC Armature Winding Fault.

Trigger fault at time — Time before entering faulted state

0 s (default) | nonnegative scalar

Simulation time at which the block enters the faulted state.

Dependencies

To enable this parameter, in the Fault Inspector window, set Trigger Type to Timed.

This parameter appears in the Trigger section of the Fault Inspector window. For more information, see Set Fault Triggers.

Extended Capabilities

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

Version History

Introduced in R2019a

R2023a: Improved support for inductive nodes

Prior to R2023a, to connect the Dynamic Load (Three-Phase) block to an inductive node, you had to provide a large parasitic resistance. From R2023a, you can connect this block to an inductive node by specifying the Rated electrical frequency, Voltage time constant, Initial supply voltage (phase-to-phase RMS), Initial supply voltage angle, and Parasitic conductance to the electrical reference parameters. As a result of this change, the Minimum active power parameter has been removed. If your model saved in an earlier release contains this block you must set appropriate values to the new parameters.

Additionally, the Modeling option parameter of the block has been renamed to Electrical connection and moved to the Main section.

R2020b: Library path change

The Dynamic Load (Three-Phase) block has been moved from the Simscape > Electrical > Passive > RLC Assemblies library to the Simscape > Electrical > Passive library.

If you have a script that depends on the library path or the Simscape component path of this block, update it to reflect these changes.