Voltage Stability: Understanding Power-Voltage Relationship
Voltage stability ensures the system can maintain acceptable voltages under all operating conditions.
Operating beyond the critical point can lead to voltage collapse and system blackout
The ‘nose’ curve of a P-V plot illustrates the characteristic relationship of power and voltage.
As power/demand increases, the voltage approaches unstable margin and beyond the critical point, the system (or a bus) becomes unstable.
That is, the load flow calculation fails to converge in a specified maximum number of iterations.
Key Points
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Operating range must remain within the stable region.
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Voltage margin determines how close the system is to instability.
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Critical point defines the maximum power transfer capability.
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Beyond this point, voltage collapse may occur.
Voltage Margin
Vmargin = Vo - Verit
V0 - No-load voltage
Verit - Critical voltage
Vmargin - Voltage margin