Remanent Voltage Tachometer for Induction Machine Grid Control
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Solution Overview
Problem
Existing systems for determining the optimal time to connect and disconnect turbines from the power grid in variable flow environments, such as tidal kinetic hydropower, are costly and unreliable, particularly in hostile environments like underwater, due to the need for tachometry instrumentation and timers that cannot compensate for unpredictable fluid flow variations.
Innovation Solution
Measuring the small remanent voltage generated by the induction machine's residual internal magnetism allows for sensing the turbine's rotation rate without separate tachometer sensors, enabling controlled switching to and from the power grid, thereby optimizing energy generation and reducing maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tachometry instrumentation is installed at the turbine to measure speed directly, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The induction machine's own magnetic field serves as the measurement source. The remanent voltage generated by the machine's residual magnetism during rotation provides the tachometer signal without requiring external sensing equipment, making the system self-measuring and eliminating complex instrumentation
Solution Approach 2:
The patent replaces mechanical/optical tachometer sensors with an electrical measurement approach. By measuring the remanent voltage signal generated by the induction machine's magnetic field during rotation, the system substitutes complex mechanical sensing with simple voltage measurement circuitry
2Device complexity
If timers are used to determine connection timing, then device complexity is reduced, but adaptability deteriorates due to inability to compensate for flow variations
Solution Approach 1:
The system continuously monitors the remanent voltage frequency, which directly reflects the turbine's rotational speed and the fluid flow conditions. This real-time feedback enables the control system to adapt connection and disconnection timing to actual flow conditions, replacing fixed timer-based control with dynamic speed-based control
Solution Approach 2:
The patent changes the control parameter from fixed time intervals to variable rotational speed measurements. By using the remanent voltage frequency (which varies with speed) as the control parameter, the system can adapt to changing flow conditions while maintaining relatively simple control logic
3Productivity
If connection is made early to maximize power generation, then productivity is improved, but reliability deteriorates due to motoring and trip risks
Solution Approach 1:
The system performs preliminary speed assessment by measuring remanent voltage frequency before grid connection. This preliminary action ensures the turbine has reached sufficient rotational speed to generate power reliably, preventing premature connection that would cause motoring or trips while still enabling early connection when conditions are favorable
4Reliability
If connection is delayed to ensure stable operation, then reliability is improved, but productivity deteriorates due to lost power generation
Solution Approach 1:
The system uses dynamic speed monitoring through remanent voltage measurement to determine the optimal connection moment. Rather than using fixed early or late connection strategies, the dynamic assessment of rotational speed allows connection at the precise moment when stability requirements are met, maximizing power generation while ensuring reliable operation
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 allows for efficient and cost-effective control of turbine operation in variable flow conditions, reducing unnecessary power generation loss and turbine wear, while eliminating the need for direct water speed measurement and expensive instrumentation.
Implementation Method 1
Measuring the small remanent voltage generated by the induction machine's residual internal magnetism allows for sensing the turbine's rotation rate
Data Source
AI summary
In a power generating system the remanent voltage of an induction machine is measured. The frequency of the remanent voltage is compared to a predetermined threshold. When the frequency of the remanent voltage is greater than the predetermined threshold the induction machine is connected to the power grid. Induction machine is disconnected from power grid once generated power drops below a predetermined threshold. Once the induction machine is disconnected, it is prevented from being reconnected to the power grid until a predetermined time period elapses.