# Asymmetric /Three Phase Power Flow

pandapower uses Sequence Frame to solve three phase power flow : pandapower.pf.runpp_3ph.runpp_3ph(net, calculate_voltage_angles=True, init='auto', max_iteration='auto', tolerance_mva=1e-08, trafo_model='t', trafo_loading='current', enforce_q_lims=False, numba=True, recycle=None, check_connectivity=True, switch_rx_ratio=2.0, delta_q=0, v_debug=False, **kwargs)

runpp_3ph: Performs Unbalanced/Asymmetric/Three Phase Load flow

INPUT:

net - The pandapower format network

OPTIONAL:

algorithm (str, “nr”) - algorithm that is used to solve the power flow problem.

The following algorithms are available:

• “nr” Newton-Raphson (pypower implementation with numba accelerations)

Used only for positive sequence network

Zero and Negative sequence networks use Current Injection method

Vnew = Y.inv * Ispecified ( from s_abc/v_abc old)

Icalculated = Y * Vnew

calculate_voltage_angles (bool, “auto”) - consider voltage angles in loadflow calculation

If True, voltage angles of ext_grids and transformer shifts are considered in the loadflow calculation. Considering the voltage angles is only necessary in meshed networks that are usually found in higher voltage levels. calculate_voltage_angles in “auto” mode defaults to:

• True, if the network voltage level is above 70 kV

• False otherwise

The network voltage level is defined as the maximum rated voltage of any bus in the network that is connected to a line.

max_iteration (int, “auto”) - maximum number of iterations carried out in the power flow algorithm.

In “auto” mode, the default value depends on the power flow solver:

• 10 for “nr”

For three phase calculations, its extended to 3 * max_iteration

tolerance_mva (float, 1e-8) - loadflow termination condition referring to P / Q mismatch of node power in MVA

trafo_model

• transformer equivalent models

• “t” - transformer is modeled as equivalent with the T-model.

• “pi” - This is not recommended, since it is less exact than the T-model. So, for three phase load flow, its not implemented

Transformer loading can be calculated relative to the rated current or the rated power. In both cases the overall transformer loading is defined as the maximum loading on the two sides of the transformer.

flow and rated current of the transformer. This is the recommended setting, since thermal as well as magnetic effects in the transformer depend on the current.

power flow to the rated apparent power of the transformer.

enforce_q_lims (bool, False) (Not tested with 3 Phase load flow) - respect generator reactive power limits

If True, the reactive power limits in net.gen.max_q_mvar/min_q_mvar are respected in the loadflow. This is done by running a second loadflow if reactive power limits are violated at any generator, so that the runtime for the loadflow will increase if reactive power has to be curtailed.

Note: enforce_q_lims only works if algorithm=”nr”!

check_connectivity (bool, True) - Perform an extra connectivity test after the conversion from pandapower to PYPOWER.

If True, an extra connectivity test based on SciPy Compressed Sparse Graph Routines is perfomed. If check finds unsupplied buses, they are set out of service in the ppc

If False, `net.load.const_z_percent` and `net.load.const_i_percent` are not considered, i.e. `net.load.p_mw` and `net.load.q_mvar` are considered as constant-power loads.

consider_line_temperature (bool, False) (Not tested with 3 Phase load flow) - adjustment of line impedance based on provided line temperature.

If True, `net.line` must contain a column `temperature_degree_celsius`. The temperature dependency coefficient alpha must be provided in the `net.line.alpha` column, otherwise the default value of 0.004 is used.

KWARGS:

numba (bool, True) - Activation of numba JIT compiler in the newton solver

If set to True, the numba JIT compiler is used to generate matrices for the powerflow, which leads to significant speed improvements.

switch_rx_ratio (float, 2)

(Not tested with 3 Phase load flow) - rx_ratio of bus-bus-switches. If impedance is zero, buses connected by a closed bus-bus switch are fused to model an ideal bus. Otherwise, they are modelled as branches with resistance defined as z_ohm column in switch table and this parameter

delta_q

(Not tested with 3 Phase load flow) - Reactive power tolerance for option “enforce_q_lims” in kvar - helps convergence in some cases.

trafo3w_losses

(Not tested with 3 Phase load flow) - defines where open loop losses of three-winding transformers are considered. Valid options are “hv”, “mv”, “lv” for HV/MV/LV side or “star” for the star point.

v_debug (bool, False) (Not tested with 3 Phase load flow) - if True, voltage values in each newton-raphson iteration are logged in the ppc.

init_vm_pu (string/float/array/Series, None) (Not tested with 3 Phase load flow) - Allows to define initialization specifically for voltage magnitudes. Only works with `init == "auto"`!

• “auto”: all buses are initialized with the mean value of all voltage controlled elements in the grid

• “flat” for flat start from 1.0

• “results”: voltage magnitude vector is taken from result table

• a float with which all voltage magnitudes are initialized

• an iterable with a voltage magnitude value for each bus (length and order has to match with the buses in net.bus)

• a pandas Series with a voltage magnitude value for each bus (indexes have to match the indexes in net.bus)

init_va_degree (string/float/array/Series, None) (Not tested with 3 Phase load flow) - Allows to define initialization specifically for voltage angles. Only works with `init == "auto"`!

• “auto”: voltage angles are initialized from DC power flow if angles are calculated or as 0 otherwise

• “dc”: voltage angles are initialized from DC power flow

• “flat” for flat start from 0

• “results”: voltage angle vector is taken from result table

• a float with which all voltage angles are initialized

• an iterable with a voltage angle value for each bus (length and order has to match with the buses in net.bus)

• a pandas Series with a voltage angle value for each bus (indexes have to match the indexes in net.bus)

recycle (dict, none) - Reuse of internal powerflow variables for time series calculation.

Contains a dict with the following parameters: bus_pq: If True PQ values of buses are updated

gen: If True Sbus and the gen table in the ppc are recalculated

Ybus: If True the admittance matrix (Ybus, Yf, Yt) is taken from

ppc[“internal”] and not reconstructed

neglect_open_switch_branches (bool, False)

(Not tested with 3 Phase load flow) - If True no auxiliary buses are created for branches when switches are opened at the branch. Instead branches are set out of service

pp.add_zero_impedance_parameters(net): To add zero sequence parameters into network from the standard type

EXAMPLES:

Use this module like this:

```from pandapower.pf.runpp_3ph import runpp_3ph
runpp_3ph(net)
```
NOTES:
• Three phase load flow uses Sequence Frame for power flow solution.

• Three phase system is modelled with earth return.

• PH-E load type is called as wye since Neutral and Earth are considered same

• This solver has proved successful only for Earthed transformers (i.e Dyn,Yyn,YNyn & Yzn vector groups)

Note

If you are interested in the pypower casefile that pandapower is using for power flow internally, you can find it in net[“_ppc0”],net[“_ppc1”], net[“_ppc2”]. However all necessary informations are written into the pandpower format net, so the pandapower user should not usually have to deal with pypower.