What is a positive sequence model of an induction machine?

In summary, the conversation discusses the use of a 3 phase induction machine model as a generator in a DFIG arrangement in Simulink. The model is stated to be a "Positive sequence model" and the conversation explores the reasoning behind this choice and the implications and limitations of using this model for this application. Additionally, there is a mention of the usefulness of zero and negative sequence models in cases of unbalanced three-phase systems.
  • #1
anon6912
21
3
I'm trying to understand a 3 phase induction machine model used as a generator in a Doubly Fed Induction Generator (DFIG) arrangement in Simulink.

In this model for the induction generator component, they have stated that the model is a "Positive sequence model" of the induction generator.

Whats the reasoning behind modelling it in this way for this application?
What are the implications and limitations of this?
What about the negative and zero sequences, arnt they worth considering?

Sorry for the number of questions, I wanted to explain my lack of understanding as comprehensively as possible:smile:
 
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  • #2
Zero and negative sequence models are useful only when the three phases are unbalanced.
 

1. What is a positive sequence model of an induction machine?

A positive sequence model of an induction machine is a mathematical representation of an asynchronous electric motor that considers the effects of positive sequence currents and voltages. This model is used to analyze the steady-state performance of the machine and is based on the assumption that all three phases of the machine are identical.

2. How does a positive sequence model differ from a negative sequence model?

A positive sequence model only considers the effects of positive sequence currents, while a negative sequence model takes into account the effects of negative sequence currents as well. Negative sequence currents can cause unbalanced forces and torque in the machine, while positive sequence currents do not.

3. What are the key components of a positive sequence model of an induction machine?

The key components of a positive sequence model include the stator, rotor, and air gap, as well as the circuit equations that describe the relationship between the stator and rotor quantities. Other components, such as the rotor resistance and leakage inductance, may also be included depending on the level of accuracy desired.

4. What are the main applications of a positive sequence model of an induction machine?

A positive sequence model is commonly used in power system studies to analyze the steady-state performance of induction motors. It is also used in the design and control of variable speed drives, as well as in fault analysis and protection schemes for power systems.

5. Are there any limitations to using a positive sequence model of an induction machine?

While a positive sequence model is a useful tool for analyzing the steady-state performance of induction machines, it does have some limitations. It does not take into account the effects of harmonics, saturation, or transient behavior, which may be important in certain applications. Additionally, the accuracy of the model decreases at high frequencies and with non-sinusoidal waveforms.

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