Garbage-In, Garbage-Out. This is why it is important to
ensure that in any modeling the inputs and functions are modeled correctly, and
the model outputs are validated and reassured before being used for practical
applications.
For generator modeling, NERC has set specific standards and
specifications to ensure that the generator models are accurate.
There are different types of timescale at which the machine response
incurs- from the fast electromagnetic, to electric mechanical, and to steady
state. For each of these different analysis, people use different types of
analysis.
For steady state analysis, we do power flow analysis, essentially
solving an ohms’s law. For dynamic behavior analysis, we look into time domain
and review transient stability analysis. NERC and FERC have provided standards
for steady state analysis. These standards are important to understand,
protect, validate controls and models for transmission system. For example,
when there was blackout in WECC in the early 1990, the power modeling actually
showed that the grid should be functioning fine. This showed the need to ensure
that the power models should be validated to ensure accuracy.
The question is how accurate is accurate enough? The test
vs. simulation generally should be accompanied with an error threshold. NERC Reliability Standards in the US, however
does not provide performance standards, but states the accuracy target is
effectively achieved by checks/balances afforded by all parties having to reach
agreement on the acceptability of associated models. The US systems provide
this leeway because systems are complicated with multiple variables, they call
can be modified to get an result.
NERC includes models for positive sequence models, the new
standards and guidelines are moving towards validation of electro-magnetic
transient (EMT) point on wave models. There are several kinds of model validation
for generation services. These can include – i) Open Circuit Generator
Saturation Curve Measurement, ii) Open Circuit Automatic Voltage Regulator
Voltage Reference Step Test, iii) Normal Synchronization, iv) V-Curves
Measures, v) Reactive Capability tests, and others.
These standards help to ensure that the models behavior the
way the actual physical assets behave. Quality-In, Quality-Out
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