Dynamic Load (Three-Phase)

Balanced three-phase dynamic load

Since R2019a

• 

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

You can model an electrical fault as an open circuit and trigger a fault event at a specific time. To enable faults modeling, in the Faults section, set the Enable open circuit fault parameter to On. The block triggers the fault at the time specified in the Simulation time for fault event parameter.

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, 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

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 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.