Variable-Speed Pumped Storage Control for Rotational Speed Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable speed pumped-storage power generation devices face challenges in maintaining stable operation and following sudden changes in power output commands due to limited variable speed ranges and inefficiencies in rotational speed control.
Innovation Solution
A power generation device with a variable speed generator motor and a pump turbine, utilizing a rotational speed control device with proportional, integral, and differential control elements to manage speed and power output, and implementing a power output command limiter function to adjust the generator motor output command based on rotational speed deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the variable speed width is limited to less than about 10% in secondary excitation variable speed pumped-storage power generation devices, then the protection control can prevent excess of the variable speed range limit, but the device cannot effectively follow sudden changes in power output commands and rotational speed decreases occur under high load conditions
Solution Approach 1:
The patent changes the excitation system parameter from secondary excitation to primary excitation, enabling the generator motor to operate with a much wider variable speed range (approximately ±50% or more from synchronous speed) compared to the limited ±10% range of secondary excitation systems. This parameter change allows the device to follow sudden power output commands effectively while maintaining protection control through the power output command limiter function.
2Reliability
If the generator motor output command increase rate is limited to prevent rotational speed decrease, then the protection control is maintained, but the power output cannot rapidly follow the power output command
Solution Approach 1:
The patent implements a dynamic power output command limiter function that adaptively adjusts the maximum increase rate of the generator motor output command based on the current operational state, particularly the guide vane opening degree and rotational speed. This dynamic adjustment allows the system to achieve rapid power output response when conditions permit while preventing rotational speed decrease when approaching operational limits.
Solution Approach 2:
The patent applies preliminary action by predicting potential rotational speed decreases based on current operating parameters (guide vane opening, rotational speed, power output command) and proactively limiting the power output command increase rate before rotational speed instability occurs. This prevents the need for reactive protection control while maintaining rapid response capability.
3Productivity
If the guide vane opening is increased to maximize water turbine output, then the power output follows the command closely, but the rotational speed control becomes unstable and excessive speed fluctuations occur
Solution Approach 1:
The patent employs feedback control through the rotational speed control device that includes proportional, integral, and differential control elements. This feedback mechanism continuously monitors the rotational speed and adjusts the guide vane opening command to maintain stable rotational speed while achieving accurate power output tracking. The feedback loop prevents excessive speed fluctuations by correcting deviations in real-time.
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
The device effectively follows sudden increases or decreases in power output commands within a wide variable speed range, preventing rotational speed decreases and ensuring stable power generation operations even under high load conditions.
Implementation Method 1
a pump turbine 2 directly connected to a rotor and configured to drive the rotor during a power generation operation
Implementation Method 2
a variable speed generator motor 1 in which a secondary side DC-excited plunge pole type rotor rotates at a variable speed
Data Source
AI summary
A power generation device is a primary excitation variable speed pumped-storage power generation device or a primary excitation variable speed power generation device. When an output of a pump turbine or a water turbine is insufficient for a power output equivalent in a vicinity of a fully opened guide vane opening and the rotational speed decreases, an increase in a generator motor output command or a generator output command is stopped, and the stop of the increase in the generator motor output command or the generator output command is canceled after the rotational speed is increased.