Definition and units

Sign Convention

Generators and Loads in an AC power system can behave either like an inductor or a capacitor. Mathematically, this has two different sign conventions, either from the generator perspective or from the load perspective. This is defined by the direction of power flow from the component.

Both sign conventions are used in eDisGo depending upon the components being defined, similar to pypsa.

Generator Sign Convention

_images/cosphi-sign-convention_generation.png

Fig. 2 Generator sign convention in detail

While defining time series for Generator, GeneratorFluctuating, and Storage, the generator sign convention is used.

Load Sign Convention

_images/cosphi-sign-convention_load.png

Fig. 3 Load sign convention in detail

The time series for Load is defined using the load sign convention.

Reactive Power Sign Convention

Generators and Loads in an AC power system can behave either like an inductor or a capacitor. Mathematically, this has two different sign conventions, either from the generator perspective or from the load perspective.

Both sign conventions are used in eDisGo, similar to pypsa. While defining time series for Generator, GeneratorFluctuating, and Storage, the generator sign convention is used. This means that when the reactive power (Q) is positive, the component shows capacitive behaviour and when the reactive power (Q) is negative, the component shows inductive behaviour.

The time series for Load is defined using the load sign convention. This means that when the reactive power (Q) is positive, the component shows inductive behaviour and when the reactive power (Q) is negative, the component shows capacitive behaviour. This is the direct opposite of the generator sign convention.

Units

Table 1 List of variables and units
Variable Symbol Unit Comment
Current I A  
Length l km  
Active Power P kW In PyPSA representation (pypsa) MW are used
Reactive Power Q kvar In PyPSA representation (pypsa) MVar are used
Apparent Power S kVA In PyPSA representation (pypsa) MVA are used
Resistance R Ohm or Ohm/km Ohm/km applies to lines
Reactance X Ohm or Ohm/km Ohm/km applies to lines
Voltage V kV  
Inductance L mH/km  
Capacitance C µF/km  
Costs
kEUR