Pandapower

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- [ADDED] added arbitrary keyword arguments, ``**kwargs``, in all create-functions
- [ADDED] groups functionality to allow grouping pandapower net elements and enable functionality to such groups
- [FIX] from_ppc() converter and power system test cases: add missing factor for tap_side=="lv"; change tap_side to "hv" for all test cases (were converted without new factor, so as the tap_side is "hv")
- [ADDED] from_mpc() converter: added functionality to import .m files via external package
- [CHANGED] from_ppc() converter: added option of tap_side and essential speed up
- [CHANGED] drop support of pandas versions < 1.0
- [ADDED] parameter in_ka for rated switch current
- [ADDED] current and loading result for switches
- [FIXED] bug for disabled continous tap controllers
- [ADDED] File I/O download and upload pandapowerNet to PostgreSQL
- [ADDED] __eq__ method for JSONSerializableClass using deepdiff library, and adjusted pp.nets_equal to use it. Requires deepdiff
- [CHANGED] enable calculating PTDF for a subset of branches
- [ADDED] in from_json one can pass a new variable of type dict called 'replace_elements'. Dict values replace the key in the loaded json string.

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- [ADDED] added support for Python 3.10
- [ADDED] added a function to pandapower.plotting to set line geodata from the geodata of the connected buses
- [ADDED] plotly hover information will indicate parallel lines, if parallel > 1
- [ADDED] 'showlegend' option for simple_plotly
- [CHANGED] rename u by vm (voltage magnitude) in file and functions names
- [FIX] plotly: only one legend entry for all lines/trafos instead of single entries for each one
- [FIX] fixed deprecation warning for pandas indexing with set (sets changed to lists inside .loc)
- [FIX] fixed hover information for lines in plotly
- [ADDED] functions to obtain grid equivalents (power system reduction with REI, Ward, X-Ward methods)
- [CHANGED] use numpy to vectorize trafo_control
- [ADDED] generic functions in pandapower.toolbox to read and write data to/from elements
- [CHANGED] remove code duplication in const_control, characteristic_control
- [ADDED] added the functionality to import grid data from PowerFactory
- [FIXED] failing tests for PowerModels integration due to the missing pm option "ac"

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- [ADDED] toolbox functions false_elm_links() and false_elm_links_loop()
- [FIXED] poly_cost and pwl_cost consideration in merge_nets()
- [ADDED] "results" initialization for runopp()
- [CHANGED] toolbox function nets_equal()
- [ADDED] toolbox function merge_same_bus_generation_plants()
- [ADDED] new object table "characteristic", new class "Characteristic" and "SplineCharacteristic" that are callable and return a value based on input according to a specified curve
- [FIXED] toolbox replace_ward_by_internal_elements() index usage
- [ADDED] TapDependentImpedance controller that adjusts the transformer parameters (e.g. vk_percent, vkr_percent) according to the tap position, based on a specified characteristic
- [ADDED] tap dependent impedance internally in build_branch: transformer (2W, 3W) parameters (e.g. vk_percent, vkr_percent) are adjusted according to the tap position based on a specified characteristic in the optional columns
- [ADDED] multiple costs check in create functions and runopp
- [ADDED] correct_dtypes() function for fileIO convert
- [FIXED] revise to_ppc() and to_mpc() init behaviour
- [CHANGED] import requirements / dependencies
- [ADDED] with the option "distributed_slack" for pp.runpp: distributed slack calculation to newton-raphson load flow; new column "slack_weights" for ext_grid, gen and xward; only 1 reference bus is allowed, any further reference buses are converted to PV buses internally
- [CHANGED] improved the integration with the package lightim2grid (fast power flow backend written in C++), add the test coverage for using lightsim2grid (for both versions, single slack and distributed slack, see https://lightsim2grid.readthedocs.io/en/latest/ on how to install and use lightsim2grid) #1455
- [FIXED] checks for when to activate and deactivate lightsim2grid in pp.runpp, added tests
- [ADDED] from_mpc: import additional variables from MATPOWER file as keys in net._options
- [FIXED] output_writer: bugfix for "res_{element}_3ph" to also run timeseries with runpp_3ph
- [FIXED] DeprecationWarning in pandas: use pandas.Index instead of pandas.Int64Index
- [FIXED] scipy version requirement: cancel the version limit
- [CHANGED] drop support for Python 3.6
- [FIXED] bugfix in timeseries calculations with recycle=True 1433
- [CHANGED] run tests in GuitHub Actions for pull requests to all branches
- [FIXED] net.unser_pf_options: bugfix for overruling the parameters that are in user_pf_options
- [ADDED] add_zero_impedance_parameters(): convenience function to add all required zero-sequence data for runpp_3ph from std_types and apply realistic assumptions
- [CHANGED] adjusted create.py functions to also include zero-sequence parameters
- [CHANGED] new tutorials for the voltage deviation model and the power flow calculation with PowerModels.jl
- [CHANGED] create_lines: enable batch creating of multiple lines now with multiole std_type entries instead of using the same std_type
- [CHANGED] OPF parameter "OPF_FLOW_LIM" now accessible through kwargs
- [CHANGED] Included DC line elements and results in to_html
- [FIXED] bugfix for currents of transformers in 3ph power flow 1343
- [CHANGED] check the dtype of the tap_pos column in the control_step of the transformer controller 1335
- [FIXED] net.sn_mva corrected for power_system_test_cases 1317
- [FIXED] fixed bugs in automatically identifying power station units (short-circuit calculation enhancements are still in progress)

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- [ADDED] Optimized the calculation of single/selected buses in 1ph/2ph/3ph short-circuit calculation
- [ADDED] Power station units with gen and trafo designated with "ps_trafo_ix" for short-circuit calculation
- [ADDED] Multiple example networks and network variations from IEC 60909-4
- [ADDED] OR-Tools implementation of linprog solver
- [ADDED] Efficient PTDF calculation on large grid
- [ADDED] toolbox function replace_pq_elmtype()
- [ADDED] Alternative constructor for DiscreteTapControl to use net.trafo.tap_step_percent to determine vm_lower_pu and vm_upper_pu based on vm_set_pu
- [ADDED] Characteristic object that represents a piecewise-linear characteristic
- [ADDED] CharacteristicControl that implements adjusting values in net based on some other input values in the grid
- [ADDED] USetTapControl that adjusts the setpoint for a transformer tap changer, based on a specified result variable (e.g. i_lv_ka)
- [CHANGED] Short-circuit gen calculation parameter "rkss_pu" to "rkss_ohm" according to IEC 60909 example
- [CHANGED] ConstControl can now also change attributes of other controllers, if the parameter "variable" is defined in the format "object.attribute" (e.g. "object.vm_set_pu")
- [CHANGED] ConstControl is initialized with level=-1 and order=-1 by default to make sure that it runs before other controllers
- [CHANGED] ConstControl now writes values from the datasource to net at time_step instead of control_step, which ensures that the values for the time step are set before running the initial power flow
- [CHANGED] replaced naming for "inductive" or "ind" by "underexcited" and "capacitive" or "cap" for "overexcited"

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- [ADDED] Factorization mode instead of inversion of Ybus in short-circuit calculation.
- [ADDED] Optimized the calculation of single/selected buses in 1ph/2ph/3ph short-circuit calculation.
- [ADDED] New options for run_control to 'continue on divergence' and 'check each level' PR 1104.
- [ADDED] Check for necessary and valid parameters to calculate 3ph powerflow.
- [ADDED] Toolbox method get_connecting_branches to determine branches which connect two sets of buses.
- [CHANGED] Deleting set_q_from_cosphi from ConstControl and deprecation warning. Use a separate ConstControl for setting Q timeseries instead.
- [CHANGED] Removed official Python 3.5 support due to end of its life 994.
- [FIXED] matching_params was missing in basic controller.
- [FIXED] Order of latitude and longitude in plotly mapbox plot.
- [FIXED] Dependencies of powerflow result plotting.
- [FIXED] init_ne_line to work with switches and parallel lines. Needed for PowerModels TNEP.

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- [ADDED] github actions for tests added.
- [ADDED] tests for PowerModels.jl interface (julia tests).
- [ADDED] documentation on how to install Gurobi as a PowerModels.jl solver.
- [ADDED] the voltage set point of external grids can now be optimized by the OPF by setting net.ext_grid.controllable to True.
- [ADDED] the Powermodels AC OPF can now be used with line loading constraints formulated with respect to the maximum current net.line.max_i_ka by using pp.runpm_ac_opf(net, opf_flow_lim="I").
- [ADDED] for easier debugging of the Powermodels interface, you can now save your .json file and specify the file name by using pp.runpm(net, delete_buffer_file=False, pm_file_path="filename.json").
- [CHANGED] The create-module now contains some functions for standardized checks and procedures in all create functions.
- [CHANGED] all controllers and output writers do not have net as attribute any more.
- [CHANGED] due to multi net implementations in pandapipes, time series functions have been adapted drastically in order to minimize duplicated code.
- [CHANGED] internal data structure tutorial contains now an example of a spy plot to visualize the admittance matrix Ybus.
- [CHANGED] introduce abstract node/branch formulation for the plotly functions.
- [FIXED] issue 905 fixed (If powerflow not necessary, e.g. two ext_grids/pv-nodes with only two buses) powerflow is bypassed and the solution is trivial.
- [FIXES] issue 954 fixed (Update bus IDs for net.asymmetric_load and net.asymmetric_sgen when merging nets in toolbox.py).
- [FIXED] issue 780 fixed (passing the shape to pypower solves the problem)
- [FIXED] excel engine pd.ExcelFile not working in new pandas version. Adaptation in file_io with new module openpyxl. openpyxl needs to be installed. Requirements are adapted accordngly.
- [FIXED] in io_utils functions with no clear class name can be de-serialized as well.
- [FIXED] fixed generic coordinates creation when respect_switches is set.
- [FIXED] recycle values None and False are considered equally --> recycle usage is skipped.
- [FIXED] control_diagnostic distinguishes between two winding and three winding transformers.
- [FIXED] toolbox functions, e.g. get_connected_elements, consider switches for three winding transformers.
- [FIXED] json load for broken geom columns in bus_geodata.