mosaik-pypower 0.8.7
An adapter to use PYPOWER with mosaik.
Requires Python: >=3.9

mosaik-pypower
==============

This package contains the adapter to connect *PYPOWER* to *mosaik*.

.. contents:: Table of Contents
   :depth: 3


Installation and starting
-------------------------

You can install mosaik-pypower via pip:

.. code-block:: bash

   $ pip install mosaik-pypower

You can run the tests with:

.. code-block:: bash

    $ git clone https://gitlab.com/mosaik/mosaik-pypower.git
    $ cd mosaik-pypower
    $ uv run pytest

You can either start mosaik-pypower as normal process or use it as a library.
If you run it via the command line, you need to pass the address that mosaik
is listening on:

.. code-block:: bash

    $ mosaik-pypower HOST:PORT

You can run ``mosaik-pypower --help`` to get more help.

In order to use it as a library, you have to import the module
``mosaik_pypower.mosaik`` and instantiate the class ``PyPower``:

.. code-block:: python

   >>> import mosaik_components.mosaik_pypower.mosaik
   >>> pp = mosaik_components.mosaik_pyower.mosaik.PyPower()


Input file format
-----------------

Mosaik-pypower uses, like PYPOWER, the bus-branch model to represent power
grids.

This model is fairly simple: You have a number of buses / nodes that are
connected via branches / lines. Transformers are just a special kind of branch.
Buses are divided into three sub-types: the reference bus (also known as swing
or slack bus), PQ buses and PU buses.

For PQ buses, the (re)active power *P* and *Q* are given, PYPOWER will
calculate the voltage magnitude and angle for these nodes. PU buses provide
active power and a constant voltage, thus PYPOWER computes the reactive power
for these buses. Mosaik-pypower currently *only supports PQ buses*, because
they are more general and if you model your power grid for mosaik, you do not
know in advance what kind of unit (consumer, producer, …) will be connected to
a bus.

Every grid needs to have *exactly one* reference bus. It has a constant voltage
magnitude and angle (usually 1 p.u.  and 0°). PYPOWER computes the residual
(re)active power for that node. Usually it is placed on the primary or
secondary side of the grid's transformer station (or where it would be)::

    With transformer       Without transformer

          REF                      REF
           |                        |
           8                        |
           |                       PQ0
          PQ0                     /   \
         /   \                   |     |
        |     |                 PQ1   PQ2
       PQ1   PQ2

PYPOWER's original input format is relatively hard to read/write and also
contains more information than we need to model power grids for the use with
mosaik. For example, it contains loads and feed-in for each bus which we don't
need here because mosaik will provide it from other simulators.

Thus, mosaik-pypower provides simpler input file formats which it will convert
to the format used by PYPOWER. Currently, it can read Excel (xlsx) and JSON
files (in an old an a new variant).

The Excel and new JSON formats are structured in a similar way. The difference
of the old JSON format are larger. You can find example files in our `source
code repository`__. Below, you’ll find a detailed description of them.

__ https://gitlab.com/mosaik/mosaik-pypower/-/tree/master/tests/data/


Excel
^^^^^

Excel files need to have the suffix ``*.xlsx`` and need to provide at least to
sheets: one for buses and one for branches. They should usually be named
*Nodes* and *Lines*, but you can also use any name you want (more on that
later).

In every sheet, the first row is reserved for headings. From row two, you list
the buses and branches (one per row). If the first cell of a row starts with
a ``#`` this row is treated as a comment.

Bus sheet
"""""""""

The bus sheet contains at least three columns (you can use the other columns
for comments):

1. The bus name (string)
2. The bus type (either ``REF`` or ``PQ``)
3. The bus' base voltage (integer in kV line-to-line, e.g. ``400`` for
   a European LV node).

Example::

   Node name  Node type  Base voltage [kV]  Notes
   Grid       REF        110                Slack bus
   # This is a comment
   Bus0       PQ         20
   Bus1       PQ         20
   Bus2       PQ         20
   Bus3       PQ         20

There must be *exactly one* REF bus in the list and it must be first in the
list.


Branch sheet
""""""""""""

The branch sheet contains at least seven columns (again, you can use additional
columns for notes):

1. The branch name (string)
2. One end of the branch (a valid bus name)
3. The other end of the branch (a valid bus name)
4. The transformer or line type (see `here`__ for a list of built-in types. You
   can also `add your own`__)
5. The branch length (float in km)
6. A flag indicating whether the branch is online / active (``1``) or offline
   / inactive (``0``)
7. The default tap turn for a transformer (usually ``0``)

__ https://gitlab.com/mosaik/mosaik-pypower/-/tree/master/mosaik_pypower/resource_db.py
__ resource-db_

Example::

   Name    From  To    Type         Length [km]  Online  Tap
   # Transformer
   Trafo1  Grid  Bus0  TRAFO_40     1.0          1       0
   # Lines
   B_0     Bus0  Bus1  NA2XS2Y_185  5.0          1
   B_1     Bus0  Bus2  NA2XS2Y_185  3.0          1
   B_2     Bus1  Bus3  NA2XS2Y_185  2.0          1
   B_3     Bus2  Bus3  NA2XS2Y_185  0.3          1


.. _resource-db:

Additional branch and transformer types
"""""""""""""""""""""""""""""""""""""""

You can add more line and transformer types via two additional sheets, *Line
types* and *Transformer types* (you can give them other names if you want to).

The headings should be pretty self-explanatory:

Example line types::

   Type name  R' [Ω/km]  X' [Ω/km]  C' [nF/km]  I_max [A]
   SPAM_200   0.1337     0.0815     0           404

Example transformer types::

   Transformer Type  S_r [MVA]  I_max_prim [A]  I_max_sec [A]  P_loss [kW]  R [Ω]   X [Ω]  taps
   TRAFO_23          23         100             800            100          0.0123  1.234  {-1: 0.9, 0: 1.0, 1: 1.1}


JSON (new format)
^^^^^^^^^^^^^^^^^

The new JSON format (use ``*.json`` as a suffix) is very similar to the Excel
format, but instead of separate sheets, its just different entries in a JSON
object. There is one entry for the buses, one for branches and one for
transformers. Each entry contains is a list of lists which are structured
like the columns in the Excel format:

.. code-block:: json

   {
       "bus": [
           ["Grid", "REF", 110.0],
           ["Bus0", "PQ",  20.0],
           ["Bus1", "PQ",  20.0],
           ["Bus2", "PQ",  20.0],
           ["Bus3", "PQ",  20.0]
       ],
       "trafo": [
           ["Trafo1", "Grid", "Bus0", "TRAFO_40", true, 0]
       ],
       "branch": [
           ["B_0", "Bus0", "Bus1", "NA2XS2Y_185", 5.0, true],
           ["B_1", "Bus0", "Bus2", "NA2XS2Y_185", 3.0, true],
           ["B_2", "Bus1", "Bus3", "NA2XS2Y_185", 2.0, true],
           ["B_3", "Bus2", "Bus3", "NA2XS2Y_185", 0.3, true]
       ]
   }

There must be *exactly one* REF bus in the list and it must also be the first
entry of the list.

If you want to specify additional branch or transformer types, you can add
``branch_types`` or ``trafo_types`` to the object. They are also structured
similarly to the Excel file:

.. code-block:: json

   {
      "bus": [
         ["Grid", "REF", 110.0],
         ["Bus0", "PQ",  20.0],
         ["Bus1", "PQ",  20.0],
      ],
      "trafo": [
         ["Trafo1", "Grid", "Bus0", "TRAFO_23", true, 0]
      ],
      "branch": [
         ["B_0", "Bus0", "Bus1", "SPAM_200", 5.0, true]
      ],
      "branch_types": {
         "SPAM_200": [0.1337, 0.0815, 0, 404]
      },
      "trafo_types": {
         "TRAFO_23": [23, 100, 800, 100, 0.0123, 1.234, {"-1": 0.9, "0": 1, "1": 1.1}]
      }
   }


JSON (old format)
^^^^^^^^^^^^^^^^^

The old JSON format (also with the ``*.json`` suffix) differs from the new
format by explicitly listing the branch and transformer parameters for each
branch and transformer. It must also have a ``base_mva`` entry which is used
for the p.u. conversion. It can usually just be set to ``1``:

::

   {
       "base_mva": <global_base_mva>,
       "bus": [
           ["<bus_id>", "REF|PQ", <base_kv>],
       ...
       ],
       "trafo": [
           ["<trafo_id>", "<from_bus_id>", "<to_bus_id>", <Sr_MVA>, <v1_%>,
           <P1_MW>, <Imax_p_A>, <Imax_s_A>],
       ...
       ],
       "branch": [
           ["<branch_id>", "<from_bus_id>", "<to_bus_id>", <length_km>,
            <R'_ohm/km>, <X'_ohm/km>, <C'_nF/km>, <I_max_A>],
           ...
       ]
   }

Again, there may only be one *REF* bus and it must be the first in the list


Usage in mosaik
---------------

As pointed out above, you can run mosaik-pypower in-process or as
a sub-process. Every instance of mosaik-pypower can handle multiple power grids
at once. This is very handy for scenarios with a lot of separate grids. You can
start one instance of mosaik-pypower for every CPU core of your machine and
distribute all grids over these instance. More instances would mean more
overhead, less instances would mean less parallelization.

Instantiation and initialization
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here is an example *sim config* for mosaik:

.. code-block:: python

   sim_config = {
       'PyPower-inproc': {
           'python': 'mosaik_components.mosaik_pypower.mosaik:PyPower',
       },
       'PyPower-subproc': {
           'cmd': 'mosaik-pypower %(addr)s',
       },
   }

When you create an instance of mosaik-pypower, you can pass three parameters:

- *step_size* is an integer in seconds (of simulation time) and defines how
  often a power flow analysis should be performend.

- *pos_load* is an optional boolean that lets you specify whether the active
  power for loads is a positive or a negative number.

  The default (``True``) is to use positive numbers for loads and negative
  numbers for feed-in of active power.

  If you want to use negative values for loads and positive for feed-in, set
  this flag to ``False``.
  
- *converge_exception* is an optional boolean that allows to set the behavior
  in case that the power flow does not converge.
  
  As default (``False``) all output attributes are set to NaN and the
  simulation continues. If set to ``True``, an exception is thrown and the
  simulation stops.

Examples:

.. code-block:: python

   # Power-flow every minute:
   pp_a = world.start('PyPower', step_size=60)

   # Power-flow every 15 minutes, negative values for active power of loads:
   pp_b = world.start('PyPower', step_size=300, pos_loads=False)


Models
^^^^^^

Mosaik-pypower provides the following models / entity types:

**Grid**
  **public:** True

  **parameters:** *gridfile* [, *sheetnames*]

  This model is used to instantiate a power-grid within mosaik-pypower from the
  *gridfile* provided. The *Grid* instance will have child entities for every
  element in that grid (buses, branches, …). You can access these entities
  via the ``children`` attribute of the *Grid* entity. These entities also
  contain information about how they are related to each other. This allows
  mosaik to determine the grid topology. You can query it via
  ``world.entity_graph[<full_entity_id>``.

  If you use an Excel file and deviate from the default sheet names, you can
  optionally pass a *sheetnames* argument which is a dict with the sheet names
  to use.

**RefBus** / **PQBus**
  **public:** False

  **attributes:** *P*, *Q*, *Vl*, *Vm*, *Va*

  Every *Grid* will contain exactly one *RefBus* entity and at least one
  *PQBus* entity.

  *P* and *Q* are active / reactive power in [W] / [VAr].

  *Vl* is the nominal voltage in [V] as defined in the grid file. *Vm* is the
  current voltage magnitude in [V] and my deviate from *Vl*. *Va* is the voltage
  angle in [°] (degree).

**Branch**
  **public:** False

  **attributes:** *P_from*, *Q_from*, *P_to*, *Q_to*, *I_real*, *I_imag*,
  *S_max*, *I_max*, *length*, *R_per_km*, *X_per_km*, *onine*

  A grid consists of an arbitrary amount of branches connecting the *PQBus*
  entities with each other.

  The attributes *(P|Q)_(from|to)* denote the (re)active power on both ends of
  the branch in [W] or [VAr]. *I_real* and *I_imag* are the complex current in
  [A] flowing through the branch.

  *S_max* and *I_max* denote the maximum acceptable apparent power (in [VA])
  and current (in [A]) for that branch.

  *lengh*, *R_per_km*, *X_per_km*, *C_per_km* and *online* are the respective
  values for the branch from the input file.

**Transformer**
  **public:** False

  **attributes:** *P_from*, *Q_from*, *P_to*, *Q_to*, *S_r*, *I_max_p*,
  *I_max_s*, *P_loss*, *U_p*, *U_s*, *taps*, *tap_turn*.

  A grid may have an arbitrary number of transformers (zero, one or more).
  Since it is just a special kind of *Branch* it shares many attributes with
  it.

  The attributes *(P|Q)_(from|to)* denote the (re)active power on both ends of
  the branch in [W] or [VAr]. *I_real* and *I_imag* are the complex current in
  [A] flowing through the branch.

  *S_r* is the rated apparent power (in [VA]) of the transformer. *I_max_p* and
  *I_max_s* are the maximum currents in [A] for the primary and secondary side
  of the transformer. *P_loss* is the transformer's nominal power loss in [W].

  *U_p* and *U_s* are the nominal primary and secondary line-to-line voltages
  in [V].

  *taps* is a dictionary of the available tap turns of the transformer.
  *tap_turn* is the currently active tap turn.


Examples for model instantiation and connection
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Here are some examples on how to instantiate a power grid and work with the
entities that you get in return.

Basic examples:

.. code-block:: python

   pp = world.start('PyPower', step_size=60)

   # Create a grid from a JSON file:
   grid = pp.Grid(gridfile='path/to/grid.json')

   # Get a list of RefBus, PQBus, Transformer and Branch entities:
   grid = grid.children

   # Create some PV entities and randomly connect them to a PQBus:
   pvs = make_pvs(...)  # Returns a list of PV entities
   pq_buses = [e for e in grid if e.type == 'PQBus']
   mosaik.util.connect_randomly(world, pvs, pq_buses, ('P_out', 'P'), ('Q_out', 'Q'))


Advanced stuff:

.. code-block:: python

   pp = world.start('PyPower', step_size=60)

   # Create a grid from an Excel file and overwrite default sheet names.
   # Directly grab the list of child entities
   grid = pp.Grid(gridfile='path/to/grid.xlsx', sheetnames={
       'bus': 'Nodes',
       'branch': 'Lines',
       'branch_types': 'Line types',
       'trafo_types': 'Transformer types',
   }).children

   # Get the RefBus
   ref_bus = [e for e in grid if e.type == 'RefBus']

   # Get all nodes starting with "ConnectionPoint_". Note that every entity ID
   # is prefixed with a grid index (e.g., "1-"). We can use regular expressions
   # to handle this:
   import re
   regex_cn = re.compile(r'\d+-ConnectionPoint_.*')
   conpoints = [e for e in grid if regex_cn.match(e.eid)]

   # Create a dictionary mapping node names to the respective entities. Again,
   # we have to strip the grid index:
   conpoints = {e.eid.split('-', 1)[1]: n
                for n in grid if regex_cn.match(n.eid)}

   # Connected loads to defined connection points:
   houses = create_houses(...)  # Returns a list of (house, node-id) tuples
   for house, node_id in houses:
       mosaik.connect(house, conpoints[house_id], ('P_out', 'P'), ('Q_out', 'Q'))

   # Get "secondary side" buses of all transformers
   trafo_nodes = []
   # 1. Get all transformers:
   trafos = [e for e in grid if e.type == 'Transformer']
   # 2. Group PQBuses by full ID for easier access:
   nodes = {e.full_id: e for e in grid if e.type == 'PQBus'}
   # 3. Iterate transformer relations (assuming that they are connected to the
   #    RefBus on their primary side):
   for trafo in trafos:
      rels = world.entity_graph[trafo.full_id]
      assert len(rels) == 2
      for rel in rels:
            if rel in nodes:
               trafo_nodes.append(nodes[rel])
               break
      else:
            raise ValueError('No PQBus found at trafo.')


Getting help
------------

If you need, please visit either the `mosaik-users mailing list`__ (or the
`PYPOWER Google group`__ if your issue is very PYPOWER specific).

__ https://mosaik.offis.de/mailinglist
__ https://groups.google.com/forum/#!forum/pypower