# Documentation

## Library

Fundamental Blocks/Elements

## Description

The Parallel RLC Load block implements a linear load as a parallel 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

Nominal voltage Vn

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

Nominal frequency fn

The nominal frequency, in hertz (Hz).

Active power P

The active power of the load, in watts.

Inductive reactive power QL

The inductive reactive power QL, in vars. Specify a positive value, or 0.

Capacitive reactive power QC

The capacitive reactive power QC, in vars. Specify a positive value, or 0.

Set the initial capacitor voltage

If selected, the initial capacitor voltage is defined by the Capacitor initial voltage parameter. If not selected, the software calculates the initial capacitor voltage in order to start the simulation in steady-state.

The Set the initial capacitor voltage parameter have no effect on the block if the capacitive reactive power is equal to zero.

Capacitor initial voltage (V)

The initial capacitor voltage used at the start of the simulation. The Capacitor initial voltage parameter have no effect on the block if the capacitive reactive power is equal to zero and if the Set the initial capacitor voltage parameter is not selected.

Set the initial inductor current

If selected, the initial inductor current is defined by the Inductor initial current parameter. If not selected, the software calculates the initial inductor current in order to start the simulation steady-state.

The Set the initial inductor current parameter have no effect on the block if the inductive reactive power is equal to zero.

Inductor initial current (A)

The initial inductor current used at the start of the simulation. The Inductor initial current parameter have no effect on the block if the inductive reactive power is equal to zero and if the Set the initial inductor current parameter is not selected.

Measurements

Select Branch voltage to measure the voltage across the Parallel RLC Load block terminals.

Select Branch current to measure the current flowing through the Parallel RLC Load block.

Select Branch voltage and current to measure the voltage and the current of the Parallel 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 measurement is identified by a label followed by the block name.

Measurement

Label

Branch voltage

`Ub:`

Branch current

`Ib:`

The Load Flow tool of the powergui block uses the parameters on this tab. These load flow parameters affect only model initialization. They do not affect simulation.

Specify the load type. The default value is ```constant Z```.

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 therefore vary 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 Apply in 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 the 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 therefore vary proportionally to the bus voltage computed by the Load Flow tool. When you apply the load flow solution to the model (by clicking Apply in the Load Flow tool), the pu 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.

## Examples

The `power_paralload` example uses a Parallel RLC Load block to implement a load.