Pandapower

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- [ADDED] compatbility with networkx 2.0 (see 82)
- [ADDED] compatibility with pandas 0.21 (see 83)
- [CHANGED] implementation of ZIP loads changed to constant current magnitude paradigm (see 62)
- [ADDED] max_step parameter for shunt
- [ADDED] added warning for large bus index values
- [FIXED] bug in short-circuit results of trafo3w
- [FIXED] bugfix in find_bridges and refactoring
- [CHANGED] faster implementation of result cleanup
- [CHANGED] faster implementation of line index handling in power flow
- [FIXED] bug in plotly label display (75)
- [ADDED] several fixes, extensions, tests for toolbox
- [ADDED] additional MV line standard types
- [FIXED] kerber extrem vorstadtnetz mv bus voltage
- [FIXED] removed incorrect estimation result tables for load, sgen, gen

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- [FIXED] ZIP load issue that led to incorrect calculation of I part with voltage angle shifts
- [FIXED] Bug that set voltage constraints to 0.9/1.2 if no voltage constraints was given in OPF
- [ADDED] possibility to access J matrix after power flow
- [ADDED] opf cost conversion
- [ADDED] opf costs in power system test cases

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- [ADDED] possibility to save networks to an sql database
- [CHANGED] major change in fileIO: all networks are converted to a uniform dataframe only version before they are saved as excel, json or sql. Old files can still be loaded, but all files saved with v1.4 can only be loaded with v1.4!
- [FIXED] all tests now pass if numba is not installed (although pandapower might be slow without numba)
- [FIXED] state estimation bug with phase shift transformers
- [CHANGED] OPF now raises specific warning if parameters are missing instead of generic exception
- [ADDED] geographical data for cigre and IEEE case networks
- [ADDED] Dickert LV Networks

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- [CHANGED] to_pickle saves only python datatypes and no pickle objects
- [ADDED] html representation of pandapower nets
- [ADDED] collections for trafos, loads, ext_grids
- [CHANGED] renamed create_shunt_as_condensator to create_shunt_as_capacitor
- [FIXED] mock problem in create docstrings
- [ADDED] Synthetic Voltage Control LV Networks

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- [ADDED] ZIP loads integrated in power flow
- [ADDED] numba implementation of dissolving switch buses
- [ADDED] Current source representation of full converter elements in short circuit calculations
- [ADDED] Method C for calculation of factor kappa in short circuit calculation
- [CHANGED] Speedup for calculation of branch short circuit currents
- [CHANGED] Branch results for minimum short circuit calculations are calculated as minimal currents
- [ADDED] Interactive plots with plotly
- [CHANGED] included pypower files for power flow and index files
- [FIXED] compatibility with numpy 1.12
- [CHANGED] -1 is a valid value for net.bus_geodata.x
- [CHANGED] allow transformers with negative xk to provide large scale IEEE cases (RTE, PEGASE, Polish)
- [ADDED] large scale IEEE cases (RTE, PEGASE, Polish)
- [ADDED] rated voltage and step variable for shunts
- [ADDED] lagrange multiplier included in bus results after OPF

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- [CHANGED] Minor refactoring in pd2ppc
- [ADDED] Technical Report