modelSystem

System reference

Information

The model System represents a global reference for the following purposes:

It allows the choice of

nominal frequency (default 50 or 60 Hertz, but arbitrary positive choice allowed)
system frequency or initial system frequency, depending on frequency type
frequency type: parameter, signal, or average (machine-dependent) system frequency
lower and upper limit-frequencies
common phase angle for AC-systems
synchronous or inertial reference frame for AC-3phase-systems
transient or steady-state initialisation and simulation modes
For 'transient' initialisation no specific initial equations are defined.
This case allows also to use Dymola's steady-state initialisation, that is DIFFERENT from ours.
Note: the parameter 'sim' only affects AC three-phase components.

It provides

the system angular-frequency omega
For fType Parameter this is simply a parameter value.
For fType Signal it is a positive input signal.
For fType Average it is a weighted average over the relevant generator frequencies.
the system angle theta by integration of
```
 der(theta) = omega 
```
the reference angle thetaRef for defining the coordinate-orientation:
thetaRef = theta if refType == Synchron (reference frame is synchronously rotating with theta).
thetaRef = 0 if refType == Inertial (inertial reference frame, not rotating).
the angle thetaRel = theta - thetaRef

The angles allow the definition of a rotating or stationary electrical coordinate system.
Root-nodes defining coordinate-orientation will have the connector variable theta = {thetaRel, thetaRef}

Note: Each model using System must use it with an inner declaration and instance name system in order that it can be accessed from all objects in the model.
When dragging the 'System' from the package browser into the diagram layer, declaration and instance name are automatically generated.

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Parameters

Type	Name	Default	Description
SI.AngularFrequency	omega_nom	2pif_nom	nominal angular frequency
Boolean	synRef	refType == PowerSystems.Types.ReferenceFrame.Synchron or dynType == PowerSystems.Types.Dynamics.SteadyState
Frequency
Types.SystemFrequency	fType	PowerSystems.Types.SystemFrequency.Parameter	system frequency type
SI.Frequency	f	f_nom	frequency if type is parameter, else initial frequency
SI.Frequency[2]	f_lim	{0.5f_nom, 2f_nom}	limit frequencies (for supervision of average frequency)
Nominal
SI.Frequency	f_nom	50	nominal frequency
SI.AngularVelocity	w_nom	2pif_nom	nom r.p.m.
System
SI.Angle	alpha0	0	phase angle
Types.ReferenceFrame	refType	PowerSystems.Types.ReferenceFrame.Synchron	reference frame (3-phase)
Initialization
Types.Dynamics	dynType	PowerSystems.Types.Dynamics.SteadyInitial	transient or steady-state model

Connectors

Type	Name	Default	Description
Modelica.Blocks.Interfaces.RealInput	omega_in		system angular frequency (optional if fType==Signal)
Interfaces.Frequency	receiveFreq		receives weighted frequencies from generators

Components

Type	Name	Default	Description
SI.Time	initime
SI.Angle	theta		system angle
SI.Angle	thetaRel	theta - thetaRef	angle relative to reference frame
SI.Angle	thetaRef	if synRef then theta else 0	angle of reference frame
SI.AngularFrequency	omega