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Load Flow Source

Three-phase voltage source for performing load flow analysis

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  • Load Flow Source block

Libraries:
Simscape / Electrical / Sources

Description

The Load Flow Source block is a three-phase voltage source that you use for a load-flow analysis. This block is only for three-phase Simscape™ networks that are compatible with frequency-time simulation mode.

The block can be used with the Busbar block to implement a swing bus, PV bus, or PQ bus. The type of bus is selected from the Source type drop-down menu parameter. See Perform a Load-Flow Analysis Using Simscape Electrical for more information about load flow in Simscape Electrical™.

When you select None for the Source impedance parameter, the Load Flow Source block models an ideal three-phase voltage source that maintains sinusoidal voltage of the specified magnitude across its terminals, independently of the current flowing through the source.

The source has a wye configuration, and port n provides a connection to the center of the wye. Port ~ is a three-phase port that represents the phases a, b, and c. The current is positive if it flows from positive to the center of the wye, and the voltage across each phase is equal to the difference between the voltage at the positive terminal and the center of the wye, V(+) – Vn.

Variables

To set the priority and initial target values for the block variables before simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.

Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. You can specify nominal values using different sources, including the Nominal Values section in the block dialog box or Property Inspector. For more information, see System Scaling by Nominal Values.

Examples

2-Bus Loadflow

2-Bus Loadflow

A model of a two-bus three-phase power system network. The model uses three instances of the Load Flow Source block from Simscape™ Electrical™, one configured to be the swing bus, one configured to be the PV bus, and one configured to be the PQ load. The PV bus regulates its output to be at a voltage of 1.025 times rated voltage and to deliver 80MW active power to the network. The Swing bus regulates voltage at the other end of the transmission line to be one times rated voltage, and it delivers the requisite power to the network so that overall active and reactive powers balance. The Simscape initialization solver determines the required internal initial voltage amplitudes and phases in both the PV bus and the Swing bus so as to start in steady state.

IEEE 9-Bus Loadflow

IEEE 9-Bus Loadflow

A model of a 9-bus three-phase power system network. This example is based on an IEEE® benchmark test case, further details of which can be found in "Power System Control and Stability" by P. M. Anderson and A. A. Fouad (IEEE Press, 2003). Simscape™ initializes two of the generators to the specified powers and terminal voltages, and initializes the remaining swing bus generator to meet just the specified voltage. The resulting load flow solution is appended to each of the busbars post-simulation. The four rows correspond to per-unit voltage, phase, active power, and reactive power respectively. Looking at Bus 1, it can be seen from the annotation that the swing generator delivers 76.4MW of active power and 27.5MVAr or reactive power to the network. Differences to the original benchmark are due to the transmission line models and transformer configurations used.

Induction Motor Initialization with Loadflow

Induction Motor Initialization with Loadflow

Initialize a three-phase induction motor as part of a load flow analysis. When initializing an induction machine that is directly connected to an AC network, in steady state there is one degree of freedom which you can set by any one of shaft torque, shaft power, motor speed, or electrical power.

Limitations

  • If you do not initialize or simulate by using frequency-time equations, the Source type parameter must be set to Voltage source with series impedance.

  • When initializing the block when Source type is set to swing bus, PV bus or PQ bus, including the internal impedance can result in initialization convergence issues. Resolve the convergence issues by using the Internal source phase search range parameter, omitting the impedance, or modelling the impedance external to the Load Flow Source block.

Ports

Conserving

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Three-phase port associated with the voltage phases a, b, and c.

Electrical conserving port associated with the center of the wye.

Parameters

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Main

Type of voltage source that the block models.

Dependencies

The visibility of Source voltage (pu), Terminal voltage (pu), Active power generated, Active power consumed, Reactive power consumed, Source phase, Minimum voltage (pu) and Internal source phase search range depend on the value that you choose for this parameter.

Per-unit voltage that the source generates.

Dependencies

This parameter is visible only when you set the Source type parameter to Voltage source with series impedance.

Per-unit terminal voltage that the source generates.

Dependencies

This parameter is visible only if you set the Source type parameter to Swing bus or PV bus.

Active power that the source generates.

Dependencies

This parameter is visible only if you set the Source type parameter to PV bus.

Active power that the source consumes.

Dependencies

This parameter is visible only if you set the Source type parameter to PQ bus.

Reactive power that the source consumes.

Dependencies

This parameter is visible only if you set the Source type parameter to PQ bus.

Rated phase-to-phase root mean square (RMS) voltage.

Rated frequency, in Hz.

Phase shift of the source.

Dependencies

This parameter is visible only if you set the Source type parameter to Voltage source with series impedance.

Impedance

Type of source impedance. Selecting any other options enables other parameters. The options are:

  • None

  • X/R Ratio

  • Series R

  • Series L

  • Series RL

Dependencies

The visibility of Short-circuit power level, Source X/R ratio, Source impedance parasitic parallel conductance, Source resistance, and Source inductance depend on the value that you choose for this parameter.

Short-circuit power level.

Dependencies

This parameter is visible only if you set the Source impedance parameter to X/R ratio.

Reactance-to-resistance ratio.

Dependencies

This parameter is visible only if you set the Source impedance parameter to X/R ratio.

Source impedance parasitic parallel conductance.

Dependencies

This parameter is visible only if you set the Source impedance parameter to X/R ratio or Series L or Series RL.

Source resistance.

Dependencies

This parameter is visible only if you set the Source impedance parameter to Series R or Series RL.

Source inductance.

Dependencies

This parameter is visible only if you set the Source impedance parameter to Series L or Series RL.

Expected Ranges

Per-unit minimum voltage. This parameter assists with the initial solve in models with non-physical, very low voltages.

Dependencies

This parameter is visible only if you set the Source type parameter in the Main setting to Swing bus, PV bus or PQ bus.

Vector of the lower and upper boundaries for the internal source phase search. Use this range to help the initial solve converge to the desired load flow solution.

Dependencies

This parameter is visible only if, in the Main setting, you set the Source type parameter to PV bus or PQ bus.

Extended Capabilities

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

Version History

Introduced in R2019b

See Also

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