classFrequency
Information
System and Autonomous Frequency
The frequency concept must fulfil several conditions.
- First it should provide a common system frequency (50 | 60 Hz) that is either
(i) parameter specified, or more generally supplied as an input signal
(ii) a dynamical variable of the model, determined by the involved generators feeding the network. - Second it should allow handling several subsystems, each with autonomous frequency, within one common model.
- Third it must allow both transient and steady-state simulation, and related to that the definition of rotating reference systems.
A system angular-frequency omega is provided by the component 'System'. We have three choices:
a) Parameter system frequency.
a) Signal system angular frequency through signal input.
b) Average system angular frequency, obtained as weighted average over involved generators.
The corresponding system-angle theta is obtained by integrating
der(theta) = omega
and is used within the sources (voltage- or power-sources, and inverters).
Note: within a variable-frequency concept, theta can not be replaced by omega*time.
We distinguish two main cases:
A) Case network-frequency.
All sources within a network-backbone have system-frequency (fType='sys').
B) Case autonomous frequency, independent of network frequency.
The sources within a network-backbone have either parameter- or signal-frequency (fType='par' or 'sig').
Frequency-independent sub-systems within one model can therefore easily be defined.
Note:
omega is used for electrical angular frequency,
w is used for mechanical angular frequency.