Doubly Fed Induction Machine Synchronous Deadband Control
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Solution Overview
Problem
Pumped storage power plants with double-fed asynchronous machines face efficiency and economic losses due to cyclic thermal stress on components when operating near synchronous speed, leading to reduced lifespan of semiconductor devices and sub-optimal power usage.
Innovation Solution
A method and system that dynamically minimize the synchronous deadband by continuously monitoring and adjusting the rotor current frequency and speed, allowing operation closer to synchronous speed while reducing thermal load on components, using measures such as adjusting converter settings and cooling systems to maintain efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the doubly fed induction machine operates near synchronous speed, then the power control range is expanded and system efficiency is improved, but cyclic thermal stress increases significantly reducing semiconductor device lifespan
Solution Approach 1:
The patent applies dynamics by making the synchronous deadband variable rather than fixed. The control device dynamically adjusts the synchronous deadband based on real-time operating conditions, allowing the operating range to adapt continuously. This enables the system to operate closer to synchronous speed when conditions permit, expanding power control range while preventing thermal stress damage when conditions require protection.
Solution Approach 2:
The patent changes the parameter of synchronous deadband from a fixed value to a variable parameter that depends on operating conditions. By continuously monitoring temperature, rotor current frequency, and power output, the system adjusts the synchronous deadband parameter dynamically, allowing optimal operation near synchronous speed while preventing thermal stress damage.
2Reliability
If a fixed synchronous deadband is used to protect semiconductor devices, then device reliability is improved, but significant efficiency and economic losses occur due to restricted operating range
Solution Approach 1:
The patent transforms the static synchronous deadband into a dynamic parameter that adapts to real-time operating conditions. The control device continuously monitors temperature, rotor current frequency, and power output to adjust the synchronous deadband, allowing the system to operate efficiently when conditions permit while maintaining device protection when conditions require it.
Solution Approach 2:
The patent implements feedback by continuously monitoring operating parameters (temperature, rotor current frequency, power output) and using this information to adjust the synchronous deadband. This closed-loop control ensures that the deadband is optimized based on actual system conditions, preventing both overheating and unnecessary efficiency losses.
3Use of energy by moving object
If the rotor current frequency is reduced to operate closer to synchronous speed, then power control efficiency is improved, but thermal stress on semiconductor devices increases due to uneven power loss distribution
Solution Approach 1:
The patent changes the synchronous deadband from a fixed parameter to a variable parameter that depends on operating conditions. By continuously adjusting the deadband based on temperature, rotor current frequency, and power output, the system can operate closer to synchronous speed with higher efficiency while preventing excessive thermal stress through real-time parameter adaptation.
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 enables safer and more efficient operation of pumped storage power plants by minimizing efficiency and profitability losses associated with synchronous deadbands, allowing for better utilization of power control ranges and increased system efficiency and profitability.
Implementation Method 1
The generator, which produces electrical energy during turbine operation, can also serve as a drive motor for the pumps or pump-turbines on the same shaft
Implementation Method 2
The maximum temperature of power semiconductors, e.g., IGBTs and diodes, used in the inverter, increases at lower rotor current frequencies under otherwise constant operating conditions
Data Source
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AI summary
A method for operating a pumped-storage power plant (1) is disclosed, which uses a doubly fed asynchronous machine (4) with a frequency converter (8) in a rotor circuit (12). The method includes determining a current setpoint for the rotor current frequency based on a setpoint power to be transmitted between an electrical grid (2) and the doubly fed asynchronous machine (4), depending on measured current operating parameters. The method further includes determining an instantaneous impermissible synchronous deadband ([-Δf, Δf]; [n0-Δn, n0+Δn]) depending on one or more parameters characterizing an instantaneous state of the pumped-storage power plant 4. The synchronous deadband ([-Δf, Δf]; [n0-Δn, n0+Δn]) is defined by a minimum required rotor current frequency (Δf) permissible for steady-state operation.The speed difference (Δn) of the rotor speed from the synchronous speed (n0) is determined, which is necessary to avoid impairment and damage to system components due to thermal stress. The method further includes controlling the converter (8) to generate voltages and currents with the current setpoint of the rotor current frequency for the rotor (11) of the asynchronous machine (4) when the current setpoint of the rotor current frequency or speed does not fall within the instantaneous impermissible synchronous deadband ([-Δf, Δf]; [n0-Δn, n0+Δn]). A system for operating a pumped-storage power plant (1) with a doubly fed asynchronous machine (4) is also disclosed.