Variable-Speed Generator-Motor Starting via Secondary Exciter Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In variable-speed pumped storage power plants, the reduced variable-speed operation range due to higher head and capacity issues prevents the generator-motor from being started up to the minimum speed required for parallel connection with the electric power system, leading to increased equipment costs and complexity.
Innovation Solution
A controller that uses a secondary exciter to supply driving electricity to the generator-motor, allowing it to start and connect in parallel with the electric power system at a speed lower than the lower limit of the variable-speed operation range, utilizing the surplus output voltage/current to increase slip and enable synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the variable-speed operation range is reduced due to higher head and capacity, then the output frequency range and output voltage range required for the secondary exciter are reduced, but the generator-motor cannot be started up to the minimum speed of the variable-speed operation range
Solution Approach 1:
The patent changes the operating parameters by allowing the generator-motor to start and connect to the electric power system at a speed lower than the conventional lower limit of the variable-speed operation range. This parameter change enables the secondary exciter to supply sufficient driving electricity even with reduced output frequency and voltage ranges, resolving the contradiction between reduced adaptability and insufficient starting speed.
2Reliability
If a static starter is additionally installed to start the generator-motor, then the generator-motor can be started reliably, but large-sized equipments shall be additionally installed leading to increased equipment costs and complicated layout design
Solution Approach 1:
The patent makes the secondary exciter perform multiple functions: it serves as both the exciter for the generator-motor and the starter for starting the generator-motor. This multi-functionality eliminates the need for a separate static starter, reducing equipment complexity and installation space while maintaining reliable starting capability through proper control of the secondary exciter.
3Reliability
If a secondary start-up transformer is provided to inject driving electricity from the secondary winding circuit side, then the generator-motor can be started, but large-sized equipments shall be additionally installed leading to increased engineering costs
Solution Approach 1:
The patent extracts and eliminates the unnecessary secondary start-up transformer from the system by utilizing the existing secondary exciter and its control system to provide the required driving electricity for starting. This extraction of redundant equipment reduces engineering costs and simplifies the overall system configuration.
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 the generator-motor to start without increasing equipment size or costs, reduces the required torque for starting, and eliminates the need for additional static starters or transformers, thereby reducing engineering and installation costs.
Implementation Method 1
a frequency converter (hereinafter referred to as a 'secondary exciter') having an output of more than 20 MW may be used for an exciter connected to the rotor winding (secondary winding) of the variable-speed generator-motor
Data Source
AI summary
In one embodiment, there is provided a controller that performs control to supply driving electricity to a secondary winding of a variable-speed generator-motor from a secondary exciter and thereby start the variable-speed generator-motor from a standstill state in a variable-speed pumped storage system. The controller performs control to complete a start-up by the driving electricity from the secondary exciter and connect the variable-speed generator-motor in parallel with an electric power system, in a state where a rotating speed of the variable-speed generator-motor is lower than a lower limit speed of a variable-speed operation range.