Synchronous Generator Line Start via Controlled Excitation
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Solution Overview
Problem
Synchronous power systems face challenges in starting up efficiently without increasing mass or decreasing efficiency, as they require precise alignment of rotor and stator magnetic poles, which is impractical for driving mechanical loads from fixed speed national electrical grids, often necessitating the use of power electronics, pony motors, and induction rotor devices.
Innovation Solution
A controller-based system that synchronizes a generator with load-driving motors by carefully controlling the field current of an exciter and the rotational acceleration of the prime mover shaft, eliminating the need for additional power electronics and induction rotor devices by using a brushless field exciter to produce a variable excitation signal that aligns the generator and motors without increasing mass or decreasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous machines are used to drive mechanical loads from fixed speed electrical grids, then efficiency is improved, but the system cannot line start due to the requirement for precise alignment of rotor and stator magnetic poles
Solution Approach 1:
The system performs preliminary alignment of the rotor and stator magnetic poles before connecting to the electrical grid. The controller monitors the phase angle between the generator and grid, and only closes the breaker when the phase angle is within a predetermined threshold, ensuring proper alignment before power connection.
Solution Approach 2:
The system uses feedback from phase angle monitoring to control the breaker closing operation. The controller continuously measures the phase angle between the generator output and the electrical grid, and uses this feedback information to determine the optimal moment to connect the generator to the grid, ensuring synchronized operation.
2Ease of operation
If additional devices such as power electronics, pony motors, and induction rotor devices are added to enable line start, then line start capability is improved, but mass increases and efficiency decreases
Solution Approach 1:
The invention extracts and eliminates the need for additional line start devices such as power electronics, pony motors, and induction rotor devices. By using the existing synchronous machine structure with proper control of the excitation system and breaker closing timing, the system achieves line start capability without adding extra mass or components.
Solution Approach 2:
The synchronous machine is designed to perform multiple functions: it can operate as a motor during startup (using grid power to align poles) and then transition to generator mode (providing power to the grid). This multi-functionality eliminates the need for separate line start devices, reducing system mass while maintaining operational capability.
3Ease of operation
If additional devices such as power electronics, pony motors, and induction rotor devices are added to enable line start, then line start capability is improved, but efficiency decreases
Solution Approach 1:
The invention removes the need for additional line start devices that would introduce energy losses. By using the synchronous machine's own excitation system and controlled breaker closing, the system achieves startup without the energy inefficiencies associated with power electronics converters, pony motors, or induction rotor devices.
Solution Approach 2:
The synchronous machine uses its own excitation system and the electrical grid's power to perform the alignment and startup process independently. The machine draws power from the grid during alignment, then transitions to generating power, eliminating the need for external auxiliary devices that would consume additional energy and reduce overall system efficiency.
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
Enables efficient synchronization of generators with motors without the inefficiencies and added mass associated with traditional methods, allowing for reliable and efficient power distribution in synchronous power systems.
Implementation Method 1
A synchronous machine commonly cannot 'line start' due to the impractical requirement to connect the nonrotating motor to the rotating electrical grid at precisely aligned stator and rotor magnetic poles
Implementation Method 2
by carefully controlling the field current of an exciter and the rotational acceleration of the prime mover shaft
Data Source
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AI summary
A system includes one or more synchronous generators mechanically coupled to an excitation system. The excitation system is configured to output an excitation signal to excite the synchronous generator to produce a voltage and a current at an output of the synchronous generator. During startup of the synchronous generator, the excitation system may also output pulses of the excitation signal to initiate synchronism of one or more non-rotating electric motors electrically coupled to the synchronous generator. In addition, the pulses may be output to urge rotation of the non-rotating electric motors into rotational electrical alignment with the synchronous generator and each other.