Reactive power
In plain terms
Beyond active power, generators and loads also exchange reactive power. Reactive power does no useful work but it strongly influences voltages: injecting or absorbing it at the right place can raise or lower local voltages and so relieve the grid without any new hardware. eDisGo currently provides a fixed-power-factor control.
Fixed cos φ control
set_time_series_reactive_power_control() derives a
reactive-power series from the active-power series using a fixed power factor cos φ,
per component type and voltage level (the values come from
config_timeseries). The core calculation is
fixed_cosphi():
The sign encodes whether the component behaves inductively or capacitively and
follows eDisGo’s (PyPSA-based) sign convention, which is opposite for generators and
loads. The helpers
get_q_sign_generator() and
get_q_sign_load() return the correct sign for a
given reactive-power mode (inductive/capacitive). See
definitions and units for the full sign convention.
By default ("default") the power factor and inductive/capacitive mode of every
component group come from the configuration files. They can be overridden per group by
passing a DataFrame (with columns components, mode and power_factor) to
generators_parametrisation / loads_parametrisation /
storage_units_parametrisation, or a group can be set to None to leave it
untouched.
Note
Reactive power must be set after all active-power series are in place (it is derived from them) — see the ordering rules.
Physics
The voltage change along a feeder depends on both active and reactive power flow, \(\Delta V \approx (R\,P + X\,Q)/V\). Because distribution lines have a sizeable reactance \(X\), modulating \(Q\) is an effective, hardware-free way to support voltage — complementary to the reinforcement measures in Grid reinforcement. Voltage-dependent controls (Q(U), cos φ(P)) are planned for future releases.