Variable Speed Pumped Storage Hydropower Control System
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Solution Overview
Problem
Conventional control systems for variable speed pumped storage hydropower systems face inefficiencies due to excessive control of generator-motor output and rotational speed, leading to overshoots and undershoots, which negatively impact pump-turbine efficiency and response speed.
Innovation Solution
A control system that includes a secondary excitation device, flow rate adjusting valve control, optimization processing, speed control, output compensation, and mechanical output compensation units, which generate and apply command values to adjust generator-motor output and pump-turbine flow rate, minimizing rotational speed deviations and optimizing system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the generator-motor output is increased quickly to respond to power system frequency changes, then the response speed is improved, but the rotational speed deviation from optimal value increases causing pump-turbine efficiency to decrease
Solution Approach 1:
The control system pre-calculates and stores the relationship between generator-motor output and optimal rotational speed in a lookup table before operation. When output changes are required, the system quickly retrieves pre-computed rotational speed demand values rather than calculating them in real-time, enabling fast response while maintaining optimal efficiency points.
Solution Approach 2:
The patent replaces the conventional mechanical governor system with an electronic control system using a microprocessor-based control unit. This electronic system calculates rotational speed demand values and controls the generator-motor output more precisely and rapidly, eliminating the sluggish response of mechanical systems while maintaining pump-turbine efficiency through accurate speed control.
2Loss of energy
If the rotational speed is adjusted to maintain optimal efficiency, then the pump-turbine efficiency is improved, but the generator-motor output control becomes sluggish and cannot respond quickly to frequency changes
Solution Approach 1:
The control system dynamically adjusts the rotational speed demand value based on real-time operating conditions by retrieving values from a pre-calculated lookup table that contains optimal speed-settings for various output levels. This allows the system to maintain optimal efficiency across varying load conditions while responding quickly to frequency changes, as the lookup table provides immediate guidance without requiring slow iterative calculations.
Solution Approach 2:
The system continuously monitors the actual rotational speed and compares it with the demanded rotational speed, then adjusts the generator-motor output accordingly. This feedback mechanism ensures that the pump-turbine operates at optimal efficiency points while enabling rapid response to frequency changes through active correction of speed deviations.
3Speed
If the generator-motor output change amount is used for compensating rotational speed demand value, then the control responsiveness is improved, but excessive control occurs causing overshoot in output and undershoot in rotational speed
Solution Approach 1:
The control system applies preliminary anti-action by calculating compensatory rotational speed demand values in advance based on the direction and magnitude of generator-motor output changes. When output increases, the system pre-determines the appropriate speed reduction; when output decreases, it pre-determines the appropriate speed increase. This prevents excessive control and oscillations by counteracting changes before they cause instability.
Solution Approach 2:
The system uses partial action by applying only the necessary rotational speed adjustment based on the actual output change requirements, rather than maximum adjustments. The compensatory rotational speed demand value is calculated proportionally to the output change, avoiding excessive control actions that would cause overshoot and undershoot, thereby maintaining control stability while preserving responsiveness.
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 system effectively suppresses rotational speed changes and maintains pump-turbine efficiency by using feedback and feed-forward compensation signals, reducing overshoots and undershoots in generator-motor output and rotational speed.
Implementation Method 1
a variable speed pumped storage hydropower system using a doubly-fed generator-motor
Implementation Method 2
A rotational speed change of the generator-motor of the variable speed pumped storage hydropower system is determined by a difference between a generator-motor output and a pump-turbine output
Data Source
AI summary
In one embodiment, a control system of a variable speed pumped storage hydropower system includes an optimization processing unit configured to calculate a flow rate adjusting valve opening demand value and a first command value, a speed control unit configured to generate a secondary current active power component command value of a secondary excitation device based on the first command value, a mechanical (pump-turbine) output compensation unit configured to calculate a compensation value of the opening of the flow rate adjusting valve and/or a compensation value of the generator-motor output, and an output control unit configured to generate a flow rate adjusting valve opening command value based on the generator-motor output command value, the flow rate adjusting valve opening demand value, the compensation value calculated by the mechanical output compensation unit, and the output detection value of the generator-motor.