Multi-Stator Machine Fault-Tolerant Control via Compensation Current Exchange
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Solution Overview
Problem
Multi-stator permanent magnet synchronous generators (PMSGs) in offshore wind turbines face significant power output reduction and revenue loss due to open-circuit faults in frequency converters, leading to increased torque ripple and potential damage from vibrations, as existing control strategies often require shutting down affected phases.
Innovation Solution
A fault-tolerant control arrangement where each frequency converter controller exchanges compensation current values with another controller to minimize torque ripple, allowing the machine to continue operating by adjusting healthy converters to compensate for faulty ones, thus reducing torque ripple without hardware modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the machine continues operating with a faulty frequency converter, then productivity is maintained, but torque ripple increases causing vibrations and potential damage
Solution Approach 1:
The invention converts the harmful effect of a faulty frequency converter into a beneficial compensation mechanism. When one frequency converter fails, another healthy converter adjusts its output to compensate for the faulty one, transforming the potential harm into a useful fault-tolerant operation mode that maintains continuous productivity while minimizing torque ripple through coordinated control of multiple converters.
Solution Approach 2:
The invention changes the operating parameters of healthy frequency converters dynamically. When a fault is detected, the control system modifies the output parameters (voltage, current, frequency) of the remaining healthy converters to compensate for the faulty converter, thereby maintaining acceptable torque ripple levels while keeping the system operational.
2Object-affected harmful factors
If healthy frequency converters compensate for faulty converters, then torque ripple is minimized, but device complexity increases due to coordination requirements
Solution Approach 1:
The invention merges the control functions of multiple frequency converters into a coordinated system. Instead of operating independently, the healthy converters are merged into a unified control scheme that shares the compensation burden, reducing the complexity burden on any single converter while collectively minimizing torque ripple through combined action.
Solution Approach 2:
The healthy frequency converters are designed to perform multiple functions: their normal power conversion function plus an additional compensation function for faulty converters. This multi-functionality allows the system to maintain simplicity in hardware while achieving complex fault-tolerant behavior through software control coordination.
3Reliability
If all phases of a faulty stator are taken out of service, then reliability is improved, but power output decreases significantly
Solution Approach 1:
The invention segments the fault isolation at the converter level rather than at the stator phase level. Instead of taking out all phases of a faulty stator, only the specific faulty converter is isolated while other converters continue to operate and compensate, thereby maintaining higher power output while still ensuring reliability through targeted fault containment.
Solution Approach 2:
The invention maintains continuous useful action by keeping healthy converters operational and having them compensate for faulty ones. Rather than shutting down entire stator phases, the system continues to produce power through the coordinated action of healthy converters, ensuring uninterrupted power output while managing faults gracefully.
Data Source
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AI summary
The invention describes a control arrangement (1) of a multiple-stator machine (2), comprising a frequency converter (20_1, 20_2) for each of the plurality of stators and a controller (1_1, 1_2) for each frequency converter (20_1, 20_2), wherein a controller (1_1, 1_2) of a frequency converter (20_1, 20_2) is realized to generate control signals (120_1, 120_2) for that frequency converter (20_1, 20_2) on the basis of current values (Iabc1, Iabc2) relating to that stator, and to generate a compensation current value (Idq_comp1, Idq_comp2) for a further controller (1_1, 1_2) on the basis of the received current values (Idq1, I*dq1, Idq2, I*dq2) in the event of an open-circuit fault in a frequency converter (20_1, 20_2); to receive appropriate input signal (⊝e), a compensation current value (Idq_comp1, Idq_comp2) from a further controller (1_1, 1_2); and to compute a voltage reference (V*dq1, V*dq2) for a subsequent transform stage (11) and PWM stage (12) of the controller (1_1, 1_2) on the basis of the received current Values (Idq1, I*dq1, Idq2, I*dq2, Idq_comp1, Idq_comp2) coming from the reference computation blocks (13, 14). The invention further describes a current control module (10) of a frequency converter controller (1_1, 1_2) of such a multi-stator machine (2); a multi-stator machine (2); and a method of performing fault-tolerant control of a multi-stator machine (2).