31.2 : 简化同步电机模型

The Synchronous Machine Model is crucial in transient stability studies.

It represents a synchronous machine with a constant internal voltage behind its direct axis transient reactance under balanced three-phase positive-sequence conditions, constant excitation, and no losses or saturation.

Here, each generator connects to a system composed of transmission lines, transformers, loads, and other machines represented by an infinite bus behind system reactance.

Consider a synchronous generator connected to a grid or infinite bus with constant voltage magnitude, phase, and frequency. Its power is a sinusoidal function of the machine power angle.

During transients, internal and bus voltages are considered constant for power calculations.

The Equal-Area Criterion is used when a step change occurs in mechanical power. The rotor accelerates due to inertia, overshooting its final steady-state point before stabilizing due to damping from mechanical and electrical losses.

The Equal-Area Criterion applies to a single machine connected to an infinite bus or two interconnected machines.

For multi-machine systems, each machine's nonlinear swing equation is solved using numerical integration to determine stability and maximum power angle.