Generator Excitation Control for Fast AC Bus Synchronization
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Solution Overview
Problem
Synchronous electric machines face challenges in synchronizing quickly and safely when bringing multiple generators online to a shared AC bus, as existing methods can cause large current surges and damage, and are often done sequentially, which is too slow for applications requiring rapid power supply.
Innovation Solution
The method involves mechanically rotating synchronous machines to a predetermined speed, electrically connecting them to a power distribution bus, and simultaneously raising excitation using a field current regulator, with a voltage regulator activated once a voltage threshold is reached, allowing for synchronized operation and rapid startup without large transient current surges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If generators are synchronized sequentially one by one, then large current surges are avoided, but the startup time becomes too slow for applications requiring rapid power supply
Solution Approach 1:
The system performs preliminary actions by mechanically rotating all synchronous machines to predetermined speed and electrically connecting them to the power distribution bus before raising excitation. This preliminary setup allows multiple generators to be ready simultaneously, enabling rapid paralleling without sequential synchronization delays.
Solution Approach 2:
The patent changes the excitation parameter control strategy by using a field current regulator to directly control field current during startup, then switching to voltage regulator control once voltage threshold is reached. This parameter transition enables safe simultaneous excitation of multiple generators, avoiding the time penalty of sequential synchronization while maintaining protection against current surges.
2Productivity
If excitation is raised rapidly to achieve faster synchronization, then startup time is reduced, but large transient current surges can occur causing damage to components
Solution Approach 1:
The system employs feedback control through a field current regulator that monitors output voltage and adjusts field current accordingly. When output voltage reaches a predetermined threshold, the regulator activates to determine input parameters, creating a feedback loop that prevents over-excitation and large transient current surges while enabling rapid synchronization.
Solution Approach 2:
The patent implements dynamic control by transitioning from direct field current control to voltage regulator control based on real-time voltage conditions. This dynamic switching allows the system to rapidly raise excitation when safe, then automatically modulate to maintain stability, achieving both fast startup and surge protection.
3Productivity
If multiple generators are excited simultaneously, then paralleling time is reduced, but current load in exciter and generator increases causing component wear
Solution Approach 1:
The system applies partial action by controlling excitation to reach a predetermined voltage threshold rather than immediately applying full excitation. The field current regulator manages the excitation ramp-up, and the voltage regulator activates only when voltage threshold is reached, preventing excessive current load while enabling simultaneous paralleling of multiple generators.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the total current load, increases machine life, allows for faster paralleling of generators, and enables successful synchronization despite load activation, minimizing component wear and ensuring reliable power supply.
Implementation Method 1
Synchronous electric machines often generate electrical power at a specific phase and frequency which depends on the speed and position of the prime mover of the electric machine
Implementation Method 2
Excitation is raised by applying a filed current to an exciter of the particular synchronous machine using a field current regulator to achieve a target field current
Data Source
AI summary
The present disclosure contemplates a method for synchronizing a large number of generators on an AC bus simultaneously by closing the generator breakers when the generators are rotating but de-energized. Then excitation is raised for each generator simultaneously, causing the generators to synchronize as voltage increases, without large transient current surges that can damage the machines. In order to safely maximize the rate at which excitation is raised, initial excitation can be controlled using current regulation, specifically controlling excitation current instead of voltage. Once a predetermined voltage is reached, a control scheme can be switched to a voltage regulation mode, which brings the generator to the final desired voltage.