Hydraulic Turbine Speed Stabilization via Net Head Control
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Solution Overview
Problem
Hydraulic machines with S-characteristics, such as pump-turbines, face challenges in stabilizing rotation speed during start-up in low water fall conditions due to unstable 'S-zones', making it difficult to synchronize with the grid using conventional PID loops, and previous solutions are either expensive or detrimental to machine performance.
Innovation Solution
A method that calculates and adjusts the target net head and guide vane opening to stabilize the rotation speed by converging the real net head and guide vane opening towards target values, using proportional derivative and integrative derivative correctors to minimize differences, ensuring the machine operates at grid-synchronized speed with zero momentum from water flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hydraulic parts are redesigned to avoid S-zones, then rotation speed stabilization is improved, but manufacturing cost increases and machine performance decreases
Solution Approach 1:
The invention changes the control parameters from direct guide vane angle control to net head control. By controlling the net head (difference between upstream and downstream water levels) to converge toward a target value, the system stabilizes rotation speed without requiring physical redesign of hydraulic components, thus avoiding increased manufacturing costs while maintaining machine performance
2Stability of the object's composition
If non-synchronized guide vanes are used to avoid S-zones, then rotation speed stabilization is improved, but machine vibrations increase and lifespan decreases
Solution Approach 1:
The invention introduces net head control as an intermediary variable between the guide vanes and the runner. Instead of directly controlling guide vane angles (which causes vibrations), the system controls the net head to converge toward a target value, which indirectly stabilizes rotation speed while avoiding harmful vibrations and extending machine lifespan
3Device complexity
If conventional PID loop is used for control, then system simplicity is maintained, but rotation speed stabilization fails in S-zones
Solution Approach 1:
The invention changes the controlled parameter from guide vane angle to net head. This parameter transformation allows the use of a relatively simple control approach while achieving rotation speed stabilization in S-zones, as controlling the net head to converge toward a target value provides inherent stability that overcomes the limitations of conventional PID control
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 method effectively stabilizes the rotation speed of hydraulic machines without impacting performance or increasing costs, allowing synchronization with the grid by controlling net head and guide vane openings, ensuring stable operation and extended machine lifespan.
Implementation Method 1
the momentum applied by the water flow on the runner
Implementation Method 2
adjusting the opening of the guide vanes so as to converge towards the target opening and reduce a height difference between the target net head and the real net head
Data Source
AI summary
A method for stabilizing the rotation speed of a machine with S-characteristics is provided. The method includes calculating a target net head and a target opening to affect guide vanes of the machine, the target net head and the target opening being calculated so that the torque exerted by water flow on the turbine is null and that the machine rotates at a target rotation speed; determining a real net head to which the machine is subjected; comparing the target net head with the real net head; and adjusting the opening of the guide vanes so as to converge towards the target opening and reduce a height difference between the target net head and the real net head.