Running a load flow

You can use the module pypowsybl.loadflow in order to run load flows on networks.

Start by importing the module:

import pypowsybl.network as pn
import pypowsybl.loadflow as lf

Providers

We can get the list of supported load flow implementations (so called providers) and default one:

>>> lf.get_provider_names()
['DynaFlow', 'OpenLoadFlow']
>>> lf.get_default_provider()
'OpenLoadFlow'

By default, load flows are based on the OpenLoadFlow implementation, fully described on Powsybl website. OpenLoadFlow supports AC Newton-Raphson and linear DC calculation methods.

You may also use DynaFlow, provided by the Dynawo project. DynaFlow is a new steady-state simulation tool that aims at calculating the steady-state point by using a simplified time-domain simulation. Please see configuration instructions on Powsybl website.

Parameters

The most important part before running a load flow is knowing the parameters and change them if needed. Let’s have a look at the default ones:

>>> lf.Parameters()
Parameters(voltage_init_mode=UNIFORM_VALUES, transformer_voltage_control_on=False, use_reactive_limits=True, phase_shifter_regulation_on=False, twt_split_shunt_admittance=False, shunt_compensator_voltage_control_on=False, read_slack_bus=True, write_slack_bus=True, distributed_slack=True, balance_type=PROPORTIONAL_TO_GENERATION_P_MAX, dc_use_transformer_ratio=True, countries_to_balance=[], connected_component_mode=<ConnectedComponentMode.MAIN: 0>, provider_parameters={})

For more details on each parameter, please refer to the API reference.

All parameters are also fully described in Powsybl load flow parameters documentation.

Parameters specific to a provider

Some parameters are not supported by all load flow providers but specific to only one. These specific parameters could be specified in a less typed way than common parameters using the provider_parameters attribute.

Warning

provider_parameters is dictionary and all keys and values have to be a string even in case of a numeric value.

We can list supported parameters specific to default provider using:

>>> lf.get_provider_parameters_names()
['slackBusSelectionMode', 'slackBusesIds', 'lowImpedanceBranchMode', 'voltageRemoteControl', ...]

And get more detailed information about theses parameters using:

>>> lf.get_provider_parameters().iloc[:2]
                                    description    type      default                                possible_values
name
slackBusSelectionMode  Slack bus selection mode  STRING  MOST_MESHED  [FIRST, MOST_MESHED, NAME, LARGEST_GENERATOR]
slackBusesIds                     Slack bus IDs  STRING_LIST

For instance, OLF supports configuration of slack bus from its ID like this:

>>> p = lf.Parameters(provider_parameters={'slackBusSelectionMode' : 'NAME', 'slackBusesIds' : 'VLHV2_0'})

AC Load Flow

In order to run an AC loadflow, simply use the run_ac() method:

>>> network = pn.create_eurostag_tutorial_example1_network()
>>> results = lf.run_ac(network, parameters=lf.Parameters(distributed_slack=False))

The result is composed of a list of component results, one for each connected component of the network included in the computation:

>>> results
[ComponentResult(connected_component_num=0, synchronous_component_num=0, status=CONVERGED, status_text=CONVERGED, iteration_count=3, reference_bus_id='VLHV1_0', slack_bus_results=[SlackBusResult(id='VLHV1_0', active_power_mismatch=-606.5596837558763)], distributed_active_power=0.0)]

Component results provides general information about the loadflow execution: was it successful? How many iterations did it need? What is the remaining active power imbalance? For example, let’s have a look at the imbalance on the main component of the network:

>>> results[0].slack_bus_results[0].active_power_mismatch
-606.5596837558763

Then, the main output of the loadflow is actually the updated data in the network itself: all voltages and flows are now updated with the computed values. For example you can have a look at the voltage magnitudes (rounded to 2 digits here):

>>> network.get_buses().v_mag.round(2)
id
VLGEN_0      24.50
VLHV1_0     400.62
VLHV2_0     388.33
VLLOAD_0    146.90
Name: v_mag, dtype: float64

DC Load Flow

In order to run a DC loadflow, simply use the run_dc() method.

For that example, we will use a distributed slack, with imbalance distributed on generators, proportional to their maximum power. We also choose to ignore transformer ratios in the DC equations:

>>> parameters = lf.Parameters(dc_use_transformer_ratio=False, distributed_slack=True,
...                            balance_type=lf.BalanceType.PROPORTIONAL_TO_GENERATION_P_MAX)

Then let’s create our test network and run the DC load flow:

>>> network = pn.create_eurostag_tutorial_example1_network()
>>> results = lf.run_dc(network, parameters)

We can finally retrieve the computed flows on lines:

>>> network.get_lines()[['p1', 'p2']]
                p1     p2
id
NHV1_NHV2_1  300.0 -300.0
NHV1_NHV2_2  300.0 -300.0