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Description

This PQ load is a 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. 


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Mask and Parameters

General Parameters:

V0Base value for PU conversion (kV)
F0Base 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)
NpActive power - Voltage variation coefficient
NqReactive power - Voltage variation coefficient
KpfActive power - Frequency variation coefficient
KqfReactive power - Frequency variation coefficient

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

  • Net_1: 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:

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bodyP_0
: Active power under nominal conditions

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bodyQ_0
: Reactive power under nominal conditions

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bodyV_0
: Nominal voltage

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bodyF_0
: Frequency deviation from the nominal value F0 in pu.

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bodyKpf
: Active power-Frequency coefficient

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bodyKqf
: Reactive power-Frequency coefficient

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bodyNp
: Active power-Voltage coefficient

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bodyNq
: Reactive power-Voltage coefficient

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bodyV
: RMS voltage measured at the connection node Net_T1

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.