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PQ Load with Load-Flow

PQ Load with Load-Flow


The PQ load with load-flow is a three-phase element consisting of equivalent RLC branches where each branch can have an equivalent resistance (P → R), an equivalent inductance (Q > 0 → L) and an equivalent capacitor (Q < 0 → C) connected in parallel or in series (only when Q > 0). There are two types of RLC shunt connections: RLC parallel and RL series. The element is both a load-flow and a non-load-flow device. This model is similar to the one found in EMTP-RV.

Table of Contents

Mask and Parameters

General Parameters:

RLC connection type
RLC ParallelRL parallel (when Q>0) or RC parallel (when Q<0)
RL SeriesRL series only
Base voltageBase value for PU conversion (kV)
Base frequencyBase value for PU conversion (Hz)

Load Parameters:

Active power (P)3-phase active power (MW)
Reactive power (Q)3-phase reactive power (Mvar)
NpActive power coefficient for load-flow constraints calculation
NqReactive power coefficient for load-flow constraints calculation

Ports, Inputs, Outputs and Signals Available for Monitoring


  • Net_1: Network connection (supports only 3-phase connections)


  • None


  • None


  • I(a,b,c): Current for each phase (A)

Description of the Load Model

Load Model

The PQ load with load-flow consists of the parallel 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:
  • The resistance value in the RL series combination is given by:
  • The resistance value in the parallel combination is given by:
  • When Q>0, the inductance value in the parallel combination becomes:

  • When Q<0, the capacitance value in the parallel combination becomes:

Load-Flow Model

The load-flow model equations of this load are given by:

The Pconstraint and Qconstraint power become the load-flow constraints for the model. The Vload-flow is the actual voltage magnitude solution on the load bus. The P and Q are the values specified in the mask as “Active Power (P)” and “Reactive Power (Q)”, respectively.

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