09-08-2012, 02:50 PM
Automatic generation control of an interconnected power system
Automatic generation1.pptx (Size: 876.16 KB / Downloads: 68)
Purpose of AGC
To maintain power balance in the system.
Make sure that operating limits are not exceeded:-
Generators limit
Tie-lines limit
Make sure that system frequency is constant (not change by load).
Overview of AGC
Load is always changing.
To maintain power balance, generators need to produce more or less to keep up with the load.
When Gen < Load (Gen > Load), generator speed and frequency will drop (rise).
=> We use this generator speed and frequency as control signals!
3 Components of AGC
Primary control
Immediate (automatic) action to sudden change of load.
For example, reaction to frequency change.
Secondary control
To bring tie-line flows to scheduled.
Corrective actions are done by operators.
Economic dispatch
Make sure that the units are scheduled in the most economical way.
AGC for Multi Generators
Consider effect of
power flows in transmission lines, and
loads at each bus
to mechanical power of each generator.
This analysis assumes that every bus is a generator bus.
Simplified Control Model
Generators are grouped into control areas.
Consider
An area as one generator in single area, and,
Tie-lines between areas as transmission lines connecting buses in single area.
We can apply the same analysis to multi-area!!
However, we have to come up with frequency-power characteristics of each area.
Actual application of this model is for power pool operation.
AGC for Multi Areas
During transient period, sudden change of load causes each area generation to react according to its frequency-power characteristics.
This is called “primary control”.
This change also effects steady state frequency and tie-line flows between areas.
We need to
Restore system frequency,
Restore tie-line capacities to the scheduled value, and,
Make the areas absorb their own load.
This is called “secondary control”.
Area Control Error (ACE)
Control setting power of each area needs to be adjusted corresponding to the change of scheduled tie-line capacity and change of system frequency.
ACE measures this balance, and is given by,
for two area case.
Where = Frequency bias setting of area i (>0) and