.PowerSystems.UsersGuide.Overview

Information

PowerSystems combines a generic concept for the modeling of electrical power systems at different levels of detail with the extensive component models of the former SPOT library.

PowerSystems uses replaceable PhaseSystems to define the voltage and current variables as well as optional supporting reference angles in the connectors. The aim is to have different single and polyphase systems and different mathematical formulations in one framework. In particular this shall cover systems like:

• AC power systems, including dc power flow, steady-state, transient, and unsymmetric,
• Variable frequency systems, e.g. in wind turbines or for drive control, and
• DC power systems, like HVDC

A general terminal for electrical power systems can be defined as:

connector Terminal "General power terminal"
replaceable package PhaseSystem = PhaseSystems.PartialPhaseSystem "Phase system";
PhaseSystem.Voltage v[PhaseSystem.n] "voltage vector";
flow PhaseSystem.Current i[PhaseSystem.n] "current vector";
PhaseSystem.ReferenceAngle theta[PhaseSystem.m] "optional vector of phase angles";
end Terminal;

The replaceable PhaseSystem defines the number n of independent voltage and current components and their representation in the connector. Moreover it defines types for the physical quantities so that terminals of different phase systems cannot be directly connected.

The vector of reference angles theta[m] allows the definition of a rotating reference system for the description of AC systems with modal components. It is known from the Spot library that this enables the treatment of modal quantities in the time domain, covering transient and unsymmetric systems as well.

The power Terminal is overdetermined with the reference angles though. The operators Connections.root, Connections.potentialRoot, Connections.isRoot and Connections.branch are used for their implementation. A Modelica tool needs to analyze connection graphs and eliminate redundant equations.

The following table summerizes the PhaseSystems that are predefined in the PowerSystems library:
PhaseSystem n m Comment
DirectCurrent 1 0 One voltage and one current component in natural coordinates
TwoConductor 2 0 Two voltage and two current components for Spot AC1ph_DC components
ThreePhase_d 1 0 One modal component for active power — like DirectCurrent, but converting voltage values to three phase
ThreePhase_dq 2 1 Two modal components for active and reactive power; one reference angle for frequency — cf. complex phasors with variable frequency
ThreePhase_dq0 3 2 Three modal components for active, reactive and dc power; two reference angles for Spot dq0 components

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