CSV files

Naming of files

A naming strategy provides a mapping between model classes and the human readable names of those entities to be used within e.g. the data sinks, in which the serialized representation of several objects of this class can be found. Currently we offer two different, pre-defined naming strategies, which you might extend to fit your needs:

  1. EntityPersistenceNamingStrategy: A basic naming strategy that is able to add prefix and suffix to the names of the entities. A flat folder structure is considered. For more details see Default naming strategy.

  2. HierarchicFileNamingStrategy: An extended version of the EntityPersistenceNamingStrategy. Additionally, the Default directory hierarchy is taken into account. Please note, that this directory hierarchy is only meant to be used in conjunction with input models.

However, you can control the behaviour of serialization and de-serialization of models by injecting the desired naming strategy you like into CsvDataSource and CsvFileSink.

Default naming strategy

There is a default mapping from model class to naming of entities in the case you would like to use csv files for (de-)serialization of models. You may extend / alter the naming with pre- or suffix by calling new EntityPersistenceNamingStrategy("prefix","suffix").

Input

Model

File Name

operator

prefix_ operator_input _suffix

node

prefix_ node_input _suffix

line

prefix_ line_input _suffix
prefix_ line_type_input _suffix

switch

prefix_ switch_input _suffix

two winding transformer

prefix_ transformer2w_input _suffix
prefix_ transformer2w_type_input _suffix

three winding transformer

prefix_ transformer3w_input _suffix
prefix_ transformer3w_type_input _suffix

measurement unit

prefix_ measurement_unit_input _suffix

biomass plant

prefix_ bm_input _suffix
prefix_ bm_type_input _suffix

combined heat and power plant

prefix_ chp_input _suffix
prefix_ chp_type_input _suffix

electric vehicle

prefix_ ev_input _suffix
prefix_ ev_type_input _suffix

electric vehicle charging station

prefix_ evcs_input _suffix

fixed feed in facility

prefix_ fixed_feed_in_input _suffix

heat pump

prefix_ hp_input _suffix
prefix_ hp_type_input _suffix

load

prefix_ load_input _suffix

photovoltaic power plant

prefix_ pv_input _suffix

electrical energy storage

prefix_ storage_input _suffix
prefix_ storage_type_input _suffix

wind energy converter

prefix_ wec_input _suffix
prefix_ wec_type_input _suffix

schematic node graphic

prefix_ node_graphic_input _suffix

schematic line graphic

prefix_ line_graphic_input _suffix

Time Series

Model

File Name

individual time series

prefix_ its _columnScheme_UUID_suffix

load profile input

prefix_ rts _profileKey_UUID_suffix

Let’s spend a few more words on the individual time series: Those files are meant to carry different types of content - one might give information about wholesale market prices, the other is a record of power values provided by a real system. To be able to understand, what’s inside of the file, the columnScheme part of the file name gives insight of its content.

For example, you have an IndividualTimeSeries CSV file for energy prices, then you use the key c from the table below for columnScheme its_c_2fcb3e53-b94a-4b96-bea4-c469e499f1a1.csv. The CSV file must then have the appropriate format for the key c :

   time,price
   2020-01-01T00:00:00Z,100.0

The CSV file requires a unique identification number. The UUID (Universally Unique Identifier) can be created here. You can also use the Method java.util.UUID#randomUUID to create a UUID. This is the UUID from the example above 2fcb3e53-b94a-4b96-bea4-c469e499f1a1.

The following keys are supported until now:

Key

Information and supported head line

c

An energy price (e.g. in €/MWh; c stands for charge).
Permissible head line: time,price

p

Active power
Permissible head line: time,p

pq

Active and reactive power
Permissible head line: time,p,q

h

Heat power demand
Permissible head line: time,h

ph

Active and heat power
Permissible head line: time,p,h

pqh

Active, reactive and heat power
Permissible head line: time,p,q,h

weather

Weather information
Permissible head line: time,coordinate,direct_irradiation,diffuse_irradiation,temperature,wind_velocity,wind_direction

Results

Model

File Name

node

prefix_ node_res _suffix

line

prefix_ line_res _suffix

switch

prefix_ switch_res _suffix

two winding transformer

prefix_ transformer2w_res _suffix

three winding transformer

prefix_ transformer3w_res _suffix

biomass plant

prefix_ bm_res _suffix

combined heat and power plant

prefix_ chp_res _suffix

electric vehicle

prefix_ ev_res _suffix

electric vehicle charging station

prefix_ evcs_res*_suffix*

fixed feed in

prefix_ fixed_feed_in_res _suffix

heat pump

prefix_ hp_res _suffix

load

prefix_ load_res _suffix

photovoltaic power plant

prefix_ pv_res _suffix

storage

prefix_ storage_res _suffix

wind energy converter

prefix_ wec_res _suffix

thermal house model

prefix_ thermal_house_res _suffix

cylindrical thermal storage

prefix_ cylindrical_storage_res _suffix

Default directory hierarchy

Although there is no fixed structure of files mandatory, there is something, we consider to be a good idea of structuring things. You may either ship your csv files directly in this structure or compress everything in a .tar.gz file. However, following this form, we are able to provide you some helpful tools in obtaining and saving your models a bit easier.

Default directory hierarchy for input classes Default directory hierarchy for input classes

Default directory hierarchy for result classes Default directory hierarchy for result classes

The italic parts are optional and the others are mandatory. As you see, this still is a pretty flexible approach, as you only need to provide, what you really need. However, note that this hierarchy is only meant to be used in conjunction with input models, yet.

The class DefaultInputHierarchy offers some helpful methods to validate and create a default input file hierarchy.

De-serialization (loading models)

Having an instance of Grid Container is most of the time the target whenever you load your grid. It consists of the three main blocks:

  1. Raw grid elements

  2. System participants

  3. Graphics

Those blocks are also reflected in the structure of data source interface definitions. There is one source for each of the containers, respectively.

As a full data set has references among the models (e.g. a line model points to its’ nodes it connects), there is a hierarchical structure, in which models have to be loaded. Therefore, the different sources have also references among themselves. An application example to load an exampleGrid from csv files located in ./exampleGrid could look like this:

    /* Parameterization */
    String gridName = "exampleGrid";
    String csvSep = ",";
    String folderPath = "./exampleGrid";
    EntityPersistenceNamingStrategy namingStrategy = new EntityPersistenceNamingStrategy(); // Default naming strategy

    /* Instantiating sources */
    TypeSource typeSource = new CsvTypeSource(csvSep, folderPath, namingStrategy);
    RawGridSource rawGridSource = new CsvRawGridSource(csvSep, folderPath, namingStrategy, typeSource);
    ThermalSource thermalSource = new CsvThermalSource(csvSep, folderPath, namingStrategy, typeSource);
    SystemParticipantSource systemParticipantSource = new CsvSystemParticipantSource(
            csvSep,
            folderPath,
            namingStrategy,
            typeSource,
            thermalSource,
            rawGridSource
    );
    GraphicSource graphicsSource = new CsvGraphicSource(
            csvSep,
            folderPath,
            namingStrategy,
            typeSource,
            rawGridSource
    );
    
    /* Loading models */
    RawGridElements rawGridElements = rawGridSource.getGridData().orElseThrow(
            () -> new SourceException("Error during reading of raw grid data."));
    SystemParticipants systemParticipants = systemParticipantSource.getSystemParticipants().orElseThrow(
            () -> new SourceException("Error during reading of system participant data."));
    GraphicElements graphicElements = graphicsSource.getGraphicElements().orElseThrow(
            () -> new SourceException("Error during reading of graphic elements."));
    JointGridContainer fullGrid = new JointGridContainer(
            gridName,
            rawGridElements,
            systemParticipants,
            graphicElements
    );

As observable from the code, it doesn’t play a role, where the different parts come from. It is also a valid solution, to receive types from file, but participants and raw grid elements from a data base. Only prerequisite is an implementation of the different interfaces for the desired data source.

Serialization (writing models)

Serializing models is a bit easier:

    /* Parameterization */
    String csvSep = ",";
    String folderPath = "./exampleGrid";
    EntityPersistenceNamingStrategy namingStrategy = new EntityPersistenceNamingStrategy();
    boolean initEmptyFiles = false;

    /* Instantiating the sink */
    CsvFileSink sink = new CsvFileSink(folderPath, namingStrategy, initEmptyFiles, csvSep);
    sink.persistJointGridContainer(grid);

The sink takes a collection of model suitable for serialization and handles the rest (e.g. unboxing of nested models) on its own. But caveat: As the (csv) writers are implemented in a concurrent, non-blocking way, duplicates of nested models could occur.

Compression and extraction of files

We consider either regular directories or compressed tarball archives (*.tar.gz) as source of input files. The class TarballUtils offers some helpful functions to compress or extract input data files for easier shipping.