Q1Power System 2
Question
Q.1. What is slack bus? What is its significance?
Answer
The slack (swing) bus is a reference bus in load flow analysis with fixed voltage magnitude and angle (usually 0 degrees), whose significance is to supply the unknown system losses and balance the overall power mismatch.
The slack bus (also called the swing bus or reference bus) is a specially designated bus in power system load flow analysis at which the voltage magnitude and phase angle are both specified and held fixed (with the angle conventionally taken as the reference, 0 degrees), while its real and reactive power generation are left unspecified and are calculated as part of the load flow solution. Its significance is that, since the total system transmission losses cannot be known in advance (they depend on the yet-to-be-determined bus voltages and power flows), the slack bus absorbs this unknown difference between total scheduled generation and total load-plus-losses, ensuring the overall power balance equation is satisfied; without a slack bus, load flow equations would be over-specified and generally unsolvable.