Pandapipes

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- [ADDED] added bulk create functions for junctions, sinks, sources, pipes (from std_type and parameters) and valves (clean control)
- [ADDED] automated Testing for Python 3.8
- [ADDED] github action tests added
- [ADDED] LHV and HHV properties for fuel gases
- [ADDED] multinet functionality to couple a pandapower and pandapipes network
- [ADDED] example gas distribution grid with houses and geodata
- [ADDED] compressibility values for hydrogen
- [ADDED] create graph added to topology
- [CHANGED] bypassing for pumps, pressure lift = 0 for negative and very high volume flows
- [CHANGED] pressure lift in pumps now based on p_from (inlet-volume flow)
- [CHANGED] logger level for pipeflow messages is now "debug" instead of "info"
- [CHANGED] usage of generic functions in the create module which are mostly based on pandapower
- [CHANGED] renaming component_models.py into base_component.py
- [CHANGED] removing extract_results from pipe, heat_exchanger and valve up to the abstract file branch_models.py
- [CHANGED] adding initial_run to net.controller and removing initial_run and recycle from all controllers
- [CHANGED] updating run_control and run_timeseries in order to minimize duplicated code between pandapower and pandapipes
- [CHANGED] update of generic geodata creation in plotting
- [CHANGED] addding initial pressure and volume values as well as its chosen regression polynomial degree to each pump
- [FIXED] all tests pass with pandas > 1.x
- [FIXED] bug fix for ext_grid result extraction in case of unordered connected junctions
- [FIXED] problem of not converging pipeflow solved if there are no branches

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- [ADDED] added the pipeflow option "reuse_internal_data" which allows to reuse the system matrix from one pipeflow to the next in combination with "only_update_hydraulic_matrix" - useful for timeseries calculations
- [ADDED] hydrogen properties
- [ADDED] Swamee-Jain friction model
- [ADDED] test networks (water) for Swamee-Jain friction model
- [ADDED] further explanation in the documentation, e.g. on heating networks and time series / controller
- [ADDED] heating network and time series tutorials
- [ADDED] enable net loading built in different pandapipes versions
- [ADDED] carry over new artificial coordinate functions from pandapower
- [ADDED] functionality to create_networkx graph for pandapipes networks
- [ADDED] tests for connected components searches in pandapipes networks
- [CHANGED] property files for bi-atomic gases
- [CHANGED] make ppipe_hook serializable and inherit from pp_hook by using decorators
- [CHANGED] changed column "controller" in controller table to "object"
- [CHANGED] changes in run_control/run_time_series for better pandapower code reusability like using initial_run variable instead of initial_pipeflow
- [CHANGED] names of parameters for regression function in pump
- [CHANGED] pressure lift for pumps is now always >= 0
- [CHANGED] on reverse flow, the pressure lift for pumps is 0
- [CHANGED] add_fluid_to_net is now a private function (usually the wrapper create_fluid_from_lib should be used)
- [FIXED] direction of pump in the water test network 'versatility' for OpenModelica
- [FIXED] accurate calculation of v in get_internal_results for pipes
- [FIXED] enable loading of nets containing controller

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- [ADDED] allow pipeflow for empty net (with no results)
- [ADDED] tests for plotting
- [ADDED] new toolbox functions and tests
- [ADDED] get... methods for fluids
- [ADDED] tutorial, documentation and tests for heat networks
- [CHANGED] default column for controllers changed from controller to object
- [CHANGED] deepcopy (now in ADict) and repr of pandapipes net + fluid
- [CHANGED] improved plotting: respect in_service
- [CHANGED] for fluids, comp, molar_mass and der_comp are now read from .txt-files and are no longer hardcoded
- [CHANGED] pandapipes.toolbox renamed to pandapipes.internals_toolbox
- [FIXED] np.isclose comparison instead of 'p_from != p_to' in pipe_component to allow for computational inaccuracy

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- [ADDED] badges for pypi and versions
- [CHANGED] result table initialization now in most cases only contains one DF creation call 42
- [CHANGED] from pandapower tempdir to pytest tmp_path in test
- [CHANGED] default orientation of sink and source collections to avoid overlapping
- [FIXED] missing images and typos in documentation

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- first release of pandapipes