Control device and control method for rotary machine, and rotary machine unit equipped with control device
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Solution Overview
Problem
In rotary machines, detecting ground faults in electric motors while minimizing the difference between required and actual torque is challenging due to the interaction between turbine and electric motor drives.
Innovation Solution
A control device that sets the induction motor to minimum torque or higher when turbine output torque is within its stable range, allowing the turbine output torque to be adjusted by subtracting electric motor output torque from the required torque, enabling smooth transition and reducing torque discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is driven to detect ground fault, then ground fault detection becomes possible, but a difference between required torque and actual sum torque is generated
Solution Approach 1:
The control device determines whether the electric motor torque is greater than a reference torque before the electric motor starts driving. This preliminary determination ensures that the motor operates in a stable region during ground fault detection, preventing torque fluctuations while maintaining detection capability.
Solution Approach 2:
The control device changes the operating parameters by adjusting the electric motor torque to be greater than a reference torque. This parameter adjustment stabilizes the motor operation during ground fault detection, eliminating torque differences while maintaining detection accuracy.
2Stability of the object's composition
If the induction motor is set to minimum torque when turbine output torque is in stable range, then smooth transition between drives is achieved, but ground fault detection becomes difficult
Solution Approach 1:
The control device adjusts the electric motor torque parameter to be greater than the minimum torque and greater than a reference torque. This parameter change enables ground fault detection while maintaining smooth transition and operational stability between turbine and motor drives.
Solution Approach 2:
The control device performs preliminary determination of motor torque before startup, ensuring it exceeds the reference torque. This preliminary action prepares the system for stable operation with detection capability, resolving the contradiction between stability and detection.
3Ease of operation
If the reference torque is set in stable output range of turbine, then synchronization issues are eliminated, but the range for ground fault detection is reduced
Solution Approach 1:
The control device sets the reference torque within the stable output range of the turbine. This parameter setting eliminates synchronization issues during motor startup while the control logic ensures the motor torque exceeds this reference, maintaining adequate detection range.
Solution Approach 2:
The control device uses feedback from the turbine's stable output range to determine the appropriate reference torque. This feedback mechanism ensures synchronization stability while the control algorithm adjusts motor torque to maintain detection capability throughout the operating range.
Data Source
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AI summary
A control device for the rotary machine driven by the turbine output torque which is an output of the turbine and the electric motor output torque which is an output of an induction motor includes a required output setting unit for setting a required torque for driving the rotary machine and a drive source command unit which, when the turbine output torque is greater than or equal to the lower limit within the stable output range of the turbine, sets the electric motor output torque to a minimum torque of the induction motor or higher and sets the turbine output torque to a value obtained by subtracting the electric motor output torque from the required torque.