Asynchronous Machine modelling at EMTP

Asynchronous Machine Model:

Basically, ABC transformation is a time variant it is more complex to solve. So, Park transformation is followed for Asynchronous machine modelling. It is a Traditional Approach.

Asynchronous Machine Equation:

Based on Park Transformation

Asynchronous machine model details:

1.      Main Data

·        Rated Power (3 phase)

·        Power factor

·        Rated Line to Line Voltage

·        Rated Power

·        Frequency

·        No of Poles

·        Armature winding connection

·        Load flow data

·        Reference frame (Stator fixed / Synchronous / Rotor fixed)

·        Initialization method (None/Steady state)

·        Steady state Slip

·        Saturation (Simulate Saturation/Total Saturation/Independent Saturation)

It is not really recommended to use load flow data to initialize asynchronous machine. The reason behind this is in a load flow bus, the P & Q need to be defined independently. In a asynchronous machine P & Q can’t be controlled independently as they are aligned together. So, a perfect initialized can’t be achieved in the load flow bus.

Steady state Slip is defined automatically once the first simulation is done, but for initial case default values had been entered. Controlled Torque are defined for the initial load conditions. Saturations are calculated from the d axis & q axis voltage and current data. These data can be retrieved from the open circuit test of the asynchronous machine.

2.      Electrical Data

·        Data type (Basic / Enable Nameplate input calculator)

·        Rotor Type (Single Squirrel Cage/ Single Squirrel Cage with deep bar factor/wound/double squirrel cage)

·        Saturation of leakage inductance

·        Circuit Parameters

Basic mode at data type enables us to define the parameter manually whereas in nameplate input calculator mode by obtaining the characteristic of motors like efficiency, slip, etc. the circuit parameters are calculated.

3.      Mechanical data

·        No of masses

·        Index of rotor mass

·        Mass Index

·        Moment of Inertia

·        Speed of deviation Damping

·        Mutual Damping

·        Spring constant

·        Absolute speed damping

·        Angular velocity

·        Torque

4.      Control Data

·        Total Mechanical Torque

·        Rotor Speed control

5.      Observe / Scope Data:

Data which is being fed to/from other models as input & output are defined here.

6.      Precision Control Data:

·        Damping factor

·        Rotor Speed tolerance

·        Voltage convergence tolerance

·        No of iterations in rotor speed sequence

Credits to: EMTP