External Grid

Note

Power values of external grids are given in the generator system, therefore p_mw is negative if the external grid is absorbing power and positive if it is supplying/generating power.

Create Function

pandapower.create_ext_grid(net, bus, vm_pu=1.0, va_degree=0.0, name=None, in_service=True, s_sc_max_mva=nan, s_sc_min_mva=nan, rx_max=nan, rx_min=nan, max_p_mw=nan, min_p_mw=nan, max_q_mvar=nan, min_q_mvar=nan, index=None, r0x0_max=nan, x0x_max=nan, **kwargs)

Creates an external grid connection.

External grids represent the higher level power grid connection and are modelled as the slack bus in the power flow calculation.

INPUT:

net - pandapower network

bus (int) - bus where the slack is connected

OPTIONAL:

vm_pu (float, default 1.0) - voltage at the slack node in per unit

va_degree (float, default 0.) - voltage angle at the slack node in degrees*

name (string, default None) - name of of the external grid

in_service (boolean) - True for in_service or False for out of service

s_sc_max_mva (float, NaN) - maximal short circuit apparent power to calculate internal impedance of ext_grid for short circuit calculations

s_sc_min_mva (float, NaN) - minimal short circuit apparent power to calculate internal impedance of ext_grid for short circuit calculations

rx_max (float, NaN) - maximal R/X-ratio to calculate internal impedance of ext_grid for short circuit calculations

rx_min (float, NaN) - minimal R/X-ratio to calculate internal impedance of ext_grid for short circuit calculations

max_p_mw (float, NaN) - Maximum active power injection. Only respected for OPF

min_p_mw (float, NaN) - Minimum active power injection. Only respected for OPF

max_q_mvar (float, NaN) - Maximum reactive power injection. Only respected for OPF

min_q_mvar (float, NaN) - Minimum reactive power injection. Only respected for OPF

r0x0_max (float, NaN) - maximal R/X-ratio to calculate Zero sequence internal impedance of ext_grid

x0x_max (float, NaN) - maximal X0/X-ratio to calculate Zero sequence internal impedance of ext_grid

* only considered in loadflow if calculate_voltage_angles = True

EXAMPLE:

create_ext_grid(net, 1, voltage = 1.03)

For three phase load flow

create_ext_grid(net, 1, voltage = 1.03,s_sc_max_mva= 1000, rx_max=0.1,r0x0_max=0.1,x0x_max= 1.0 )

Input Parameters

net.ext_grid

Parameter

Datatype

Value Range

Explanation

name

string

name of the external grid

bus*

integer

index of connected bus

vm_pu*

float

\(>\) 0

voltage set point [p.u]

va_degree*

float

angle set point [degree]

max_p_mw**

float

Maximum active power

min_p_mw**

float

Minimum active power

max_q_mvar**

float

Maximum reactive power

min_q_mvar**

float

Minimum reactive power

s_sc_max_mva***

float

\(>\) 0

maximum short circuit power provision [MVA]

s_sc_min_mva***

float

\(>\) 0

minimum short circuit power provision [MVA]

rx_max***

float

0…1

maxium R/X ratio of short-circuit impedance

rx_min***

float

0…1

minimum R/X ratio of short-circuit impedance

r0x0_max****

float

0…1

maximal R/X-ratio to calculate Zero sequence internal impedance of ext_grid

x0x_max****

float

0…1

maximal X0/X-ratio to calculate Zero sequence internal impedance of ext_grid

in_service*

boolean

True / False

specifies if the external grid is in service.

*necessary for executing a power flow calculation
**optimal power flow parameter
***short-circuit calculation parameter
****Single phase short circuit/Three Phase load flow calculation parameters

Electric Model

** Balanced Load Flow** The external grid is modelled as a voltage source in the power flow calculation, which means the node the grid is connected to is treated as a slack node:

alternate Text

with:

\begin{align*} \underline{v}_{bus} &= vm\_pu \cdot e^{j \cdot \theta} \\ \theta &= shift\_degree \cdot \frac{\pi}{180} \end{align*}

** Unbalanced Load Flow / Single phase short ciruit **

The external grid is modelled as a voltage source for positive sequence model, which means the node the grid is connected to is treated as a slack node. For zero sequence and negative sequence external grid impedance is calculated:

alternate Text
\begin{align*} \underline{v}_{1} &= vm\_pu \cdot e^{j \cdot \theta} \\ \theta &= shift\_degree \cdot \frac{\pi}{180} \end{align*} \begin{align*} \underline{Z}_{0} &= c \cdot \frac{(vm \cdot e^{j \cdot \theta})^2}{S_{sc_mva}} \\ \theta &= shift\_degree \cdot \frac{\pi}{180} \end{align*} \begin{align*} \underline{v}_{bus} &= vm\_pu \cdot e^{j \cdot \theta} \\ \theta &= shift\_degree \cdot \frac{\pi}{180} \end{align*}

Result Parameters

net.res_ext_grid

Parameter

Datatype

Explanation

p_mw

float

active power supply at the external grid [MW]

q_mvar

float

reactive power supply at the external grid [MVar]

Active and reactive power feed-in / consumption at the slack node is a result of the power flow:

\begin{align*} p\_mw &= P_{eg} \\ q\_mvar &= Q_{eg} \end{align*}

net.res_ext_grid_3ph

Parameter

Datatype

Explanation

p_a_mw

float

active power supply at the external grid : Phase A [MW]

q_a_mvar

float

reactive power supply at the external grid : Phase A [MVar]

p_b_mw

float

active power supply at the external grid : Phase B [MW]

q_b_mvar

float

reactive power supply at the external grid : Phase B [MVar]

p_c_mw

float

active power supply at the external grid : Phase C [MW]

q_c_mvar

float

reactive power supply at the external grid : Phase C [MVar]

Active and reactive power feed-in / consumption at the slack node is a result of the power flow:

\begin{align*} p\_mw_{phase} &= P_{eg_{phase}} \\ q\_mvar_{phase} &= Q_{eg_{phase}} \end{align*}