Extended Ward

Create Function

Input Parameters

net.xward

Parameter

Datatype

Value Range

Explanation

name

string

name of the extended ward equivalent

bus*

integer

index of connected bus

ps_mw*

float

constant active power demand [MW]

qs_mvar*

float

constant reactive power demand [MVar]

pz_mw*

float

constant impedance active power demand at 1.0 pu [MW]

qz_mvar*

float

constant impedance reactive power demand at 1.0 pu [MVar]

r_ohm*

float

\(>\) 0

internal resistance of the voltage source [ohm]

x_ohm*

float

\(>\) 0

internal reactance of the voltage source [ohm]

vm_pu*

float

\(>\) 0

voltage source set point [p.u]

in_service*

boolean

True / False

specifies if the extended ward equivalent is in service.

*necessary for executing a power flow calculation.

Electric Model

The extended ward equivalent is a ward equivalent: with additional PV-node with an internal resistance.

../_images/xward.png

The constant apparent power is given by:

\begin{align*} P_{const} &= ps\_mw\\ Q_{const} &= qs\_mvar\\ \end{align*}

The shunt admittance part of the extended ward equivalent is calculated as described here:

\begin{align*} \underline{y}_{shunt} &= \frac{pz\_mw + j \cdot qz\_mvar}{S_{N}} \end{align*}

The internal resistance is defined as:

\begin{align*} \underline{z}_{int} &= r\_pu + j \cdot x\_pu \end{align*}

The internal voltage source is modelled as a PV-node (generator) with:

\begin{align*} p\_mw &= 0 \\ vm\_pu &= vm\_pu \end{align*}

Result Parameters

net.res_xward

Parameter

Datatype

Explanation

p_mw

float

active power demand of the ward equivalent [MW]

q_mvar

float

reactive power demand of the ward equivalent [MVar]

vm_pu

float

voltage at the ward bus [p.u]

\begin{align*} vm\_pu &= v_{bus} \\ p\_mw &= P_{const} + Re(\frac{\underline{V}_{bus}^2}{\underline{Y}_{shunt}}) + Re(\underline{I}_{int} \cdot \underline{V}_{bus}) \\ q_mvar &= Q_{const} + Im(\frac{\underline{V}_{bus}^2}{\underline{Y}_{shunt}} + Im(\underline{I}_{int} \cdot \underline{V}_{bus}) ) \end{align*}