Variable Speed Turbine Pump Mode Start-Up Sequence
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Solution Overview
Problem
Optimizing the start-up of hydroelectric turbines in pump mode, particularly for variable speed motors, is challenging due to unstable grid conditions such as frequency and voltage variations, leading to prolonged non-optimal operation times.
Innovation Solution
A method involving operating the variable speed motor at a fixed speed with partially opened guide vanes, followed by power control mode, to minimize non-optimal operation time and ensure optimal hydraulic and electrical constraints are met, allowing for flexible operation across a wider range of conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the turbine is started directly in optimal mode, then hydraulic efficiency is maximized, but the system cannot operate when grid conditions are unstable or head is insufficient
Solution Approach 1:
The patent implements a dynamic start-up sequence that transitions the turbine from non-optimal to optimal mode based on real-time head conditions. The guide vane opening and motor speed are dynamically adjusted: initially operating with guide vanes partially opened at fixed speed, then transitioning to power control mode with optimal guide vane opening when head conditions permit, thereby adapting to varying grid conditions while maximizing hydraulic efficiency when possible.
2Productivity
If the guide vanes are fully opened for optimal operation, then hydraulic efficiency is improved, but cavitation occurs on the runner blades
Solution Approach 1:
The patent applies preliminary action by establishing minimum head conditions before transitioning to optimal operation mode. The system first operates in a preparatory phase with guide vanes partially opened, building sufficient head in the upper reservoir. Only when the head reaches the minimum required value does the system transition to power control mode with guide vanes fully opened, ensuring cavitation-free optimal operation.
3Reliability
If the turbine operates in non-optimal mode to meet minimum head requirements, then cavitation is avoided, but operation time in non-optimal mode is prolonged
Solution Approach 1:
The patent implements periodic action through a structured two-phase start-up sequence. Phase 1 operates with guide vanes partially opened at fixed speed to build head quickly. Phase 2 transitions to power control mode with guide vanes fully opened for optimal operation. This periodic transition minimizes the duration of non-optimal operation while ensuring reliable cavitation-free operation throughout the process.
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 time spent in non-optimal mode, enables efficient operation regardless of grid conditions, and enhances the flexibility and design of the turbine cycle, ensuring optimal performance without cavitation.
Implementation Method 1
a variable speed electrical motor, connected to a grid... the generator is powered by electrical energy provided by the grid to convert the electrical energy into mechanical energy for pumping water
Implementation Method 2
a turbine and can be connected to a grid... produce electrical energy from hydraulic energy
Implementation Method 3
a distributor comprising guide vanes to control a flow of water to said runner
Data Source
AI summary
The invention concerns a method for starting a hydroelectric turbine (10) in a pumping mode, said turbine being provided with a runner (6) mechanically coupled to a shaft line (8) and a variable speed electric motor connected to a grid, a distributor (4) comprising guide vanes to control a flow of water to said runner, the method comprising:a) a step of operating the variable speed motor at least partly at fixed speed, said guide vanes being only partially opened, and of defining or calculating:data of a plurality of hydraulic characteristics (C1, C2, Ci) of the turbine for an operation without cavitation;data of an operation range of the electric motor, giving the speed of the motor as a function of its power;b) then a step of operating the turbine in a power control mode.