Description
This PQ load is a two-terminal single-phase element consisting of equivalent RL series or RC series branch where each branch can have an equivalent resistance (P → R), an equivalent inductance (Q > 0 → L) or an equivalent capacitor (Q < 0 → C) connected in series. This block is intended to be connected between phases in a three-phase network.
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Mask and Parameters
General Parameters:
| V0 | Base value for PU conversion (kV) |
| F0 | Base value for PU conversion (Hz) |
Load Parameters:
| Base active power (P0) | 1-phase active power under nominal conditions (kW) |
| Base reactive power (Q0) | 1-phase reactive power under nominal conditions (kW) |
| Np | Active power - Voltage variation coefficient |
| Nq | Reactive power - Voltage variation coefficient |
| Kpf | Active power - Frequency variation coefficient |
| Kqf | Reactive power - Frequency variation coefficient |
Ports, Inputs, Outputs and Signals Available for Monitoring
Ports
- Net_1: Network connection (supports only 1-phase connections)
- Net_3: Network connection (supports only 1-phase connections)
Inputs
- None
Outputs
- None
Sensors
- F: Estimated current at the point of connection
- Lout: Effective inductance or Capacitance
- Rout: Effective resistance
- Vrms: Estimated RMS voltage at the point of connection
Description of the Load Model
Load Model
The PQ load consists of the series combination of equivalent R, L and C branches and the series combination of equivalent R and L branches. The following rules are applied:
- If P=0 and Q=0, the element becomes disconnected in all solution methods.
- The RL series inductance equivalent is calculated using:
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L(Q>0) = {V_{base}^2 \cdot Q \over \omega \cdot (P^2 + Q^2)} |
- The resistance value in the RL series combination is given by:
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R = {V_{base}^2 \cdot P \over (P^2 + Q^2)} |
- When Q<0, the capacitance value becomes:
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C(Q<0) = \frac{P^2 + Q^2}{V_{base}^2 \cdot Q \cdot \omega } |
Model Equations
The model equations of this load are given by:
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P=P_0\cdot\left(\frac{V}{V_0}\right)^{Np}\cdot(1+Kpf\cdot \Delta f)
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Q=Q_0\cdot\left(\frac{V}{V_0}\right)^{Nq}\cdot(1+Kqf\cdot \Delta f) |
where:
: Active power under nominal conditionsMathinline body P_0
: Reactive power under nominal conditionsMathinline body Q_0
: Nominal voltageMathinline body V_0
: Frequency deviation from the nominal value F0 in pu.Mathinline body F_0
: Active power-Frequency coefficientMathinline body Kpf
: Reactive power-Frequency coefficientMathinline body Kqf
: Active power-Voltage coefficientMathinline body Np
: Reactive power-Voltage coefficientMathinline body Nq
: RMS voltage measured between connection nodes Net_T1 and Net_T3Mathinline body V
By adjusting Np and Nq equal to 0, 1, or 2, the load can be set to work as a constant power, constant current, or constant impedance, respectively.