Documentation

Three-Phase Series RLC Load

Implement three-phase series RLC load with selectable connection

Library

Fundamental Blocks/Elements

Description

The Three-Phase Series RLC Load block implements a three-phase balanced load as a series combination of RLC elements. At the specified frequency, the load exhibits a constant impedance. The active and reactive powers absorbed by the load are proportional to the square of the applied voltage.

Only elements associated with nonzero powers are displayed in the block icon.

Dialog Box and Parameters

Parameters Tab

Configuration

The connection of the three phases. Select one of the following four connections:

Y(grounded)

Neutral is grounded.

Y(floating)

Neutral is not accessible.

Y(neutral)

Neutral is made accessible through a fourth connector.

Delta

Three phases connected in delta

The block icon is updated according to the load connection.

Nominal phase-to-phase voltage Vn

The nominal phase-to-phase voltage of the load, in volts RMS (Vrms).

Nominal frequency fn

The nominal frequency, in hertz (Hz).

Specify PQ powers for each phase

Select to specify active powers, inductive reactive powers, and capacitive reactive powers for each phase of the load.

Active power P (W)

The three-phase active power of the load, in watts. This parameter is visible only when Specify PQ powers for each phase is cleared.

Inductive reactive power QL (positive var)

The three-phase inductive reactive power QL, in vars. Specify a positive value or 0. This parameter is visible only when Specify PQ powers for each phase is cleared.

Capacitive reactive power QC (negative var)

The three-phase capacitive reactive power QC, in vars. Specify a positive value or 0. This parameter is visible only when Specify PQ powers for each phase is cleared.

Active powers [Pa Pb Pc] (W):

The three-phase active power of the load, in watts. Specify three positive values. You can specify different powers for each phase, including 0. This parameter is visible only when you select Specify PQ powers for each phase.

Inductive reactive powers [QLa QLb QLc] (positive var):

The three-phase inductive reactive power QL, in vars. Specify three positive values. You can specify different powers for each phase, including 0. This parameter is visible only when you select Specify PQ powers for each phase.

Capacitive reactive powers [QCa QCb QCc] (negative var):

The three-phase capacitive reactive power QC, in vars. Specify three positive values. You can specify different powers for each phase, including 0. This parameter is visible only when you select Specify PQ powers for each phase.

Measurements

Select Branch voltages to measure the three voltages across each phase of the Three-Phase Series RLC Load block terminals. For a Y connection, these voltages are the phase-to-ground or phase-to-neutral voltages. For a delta connection, these voltages are the phase-to-phase voltages.

Select Branch currents to measure the three total currents (sum of R, L, C currents) flowing through each phase of the Three-Phase Series RLC Load block. For a delta connection, these currents are the currents flowing in each branch of the delta.

Select Branch voltages and currents to measure the three voltages and the three currents of the Three-Phase Series RLC Load block.

Place a Multimeter block in your model to display the selected measurements during the simulation. In the Available Measurements list box of the Multimeter block, the measurements are identified by a label followed by the block name.

Measurement

 

Label

Branch voltages

Y(grounded)

Uag:

 

Y(floating)

Uan:

 

Y(neutral)

Uan:

 

Delta

Uab:

Branch currents

Y(grounded)

Iag:

 

Y(floating)

Ian:

 

Y(neutral)

Ian:

 

Delta

Iab:

Load Flow Tab

The parameters on this tab are used by the Load Flow tool of the Powergui block. These load flow parameters are used for model initialization only, they have no impact on the block model and on the simulation performance.

Load type

Specify the load type.

If you select constant Z, the load impedance is determined from the nominal phase-to-phase voltage Vn, active power P, and reactive power (QL-QC) specified on the Parameters tab of the block dialog box. During the load flow solution, the impedance is kept constant. The effective P and Q are therefore varying proportionally to the square of the bus voltage computed by the Load Flow tool.

If you select constant PQ, the active power P and reactive power Q are kept constant and equal to the values specified on the Parameters tab of the block dialog box. When you apply the load flow solution to the model (by clicking the Apply button of the Load Flow tool), the Nominal phase-to-phase voltage Vn parameter on the Parameters tab is automatically adjusted to the phase-to-phase bus voltage computed by the Load Flow tool.

If you select constant I, the load current is kept constant at its nominal value determined from base voltage specified in the dialog box of the associated Load Flow Bus block and from active power P and reactive power QL and QC specified on the Parameters tab of the block dialog box. The effective P and Q are therefore varying proportionally to the bus voltage computed by the Load Flow tool. When you apply the load flow solution to the model (by clicking the Apply button of the Load Flow tool), the p.u. value of the nominal voltage Vn on the Parameters tab is automatically adjusted to the square root of the load voltage (in pu) computed by the Load Flow tool.

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