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# Solving For Sequence Currents for a radial system with a Wind Turbine Modeled as a Constant Current

## Solving For Sequence Currents for a radial system with a Wind Turbine Modeled as a Constant Current

(OP)
Hello,

I have a simple radial system which is fed by a utility followed by a series impedance and finally a Type 4 WTG Type element. (See image below)

Although I realize the system above is unrealistic i wanted to give myself a simple example.

I want to look at how the system would react to a L-G fault at the terminals of the WTG element

The Type 4 WTG element would have to be modeled as a Constant current source for the positive sequence network

Lets assume the following for the WTG:

1.In the positive sequence network for the WTG would be represented as a constant current source (Lets assume we know this SC current)
2.For the negative sequence network lets assume the the WTG is represented by the WTGs impedance (Some ZWTG)
3.For the zero sequence network the WTG impedance would be considered as an open circuit

Under the assumptions listed above I am having trouble thinking about how to go about finding the sequence currents at the faulted bus

I am thinking that super position has to come into the picture for such a circuit however im having trouble seeing how to go about it

If someone can help me form a general approach of how to solve for the sequence currents at the faulted bus i would really appreciate the help

### RE: Solving For Sequence Currents for a radial system with a Wind Turbine Modeled as a Constant Current

"Often state-of-the art Type IV WTGs only inject a symmetrical current under all operating conditions including balanced and unbalanced faults. Hence, the negative and zero sequence components of the current during a fault are non-existent. However, it should be noted that the technology allows Type IV WTGs to contribute negative sequence current, if required"

http://www.pes-psrc.org/Reports/Fault%20Current%20...

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