Fault-Tolerant PM Motor Drive Control for DC Bus Overvoltage
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Solution Overview
Problem
In multi-channel permanent magnet motor systems, particularly in aerospace applications, faults in one channel can induce high back emf, leading to DC bus overvoltage and potential damage to the motor system due to unregulated regenerative power, which is exacerbated by size/weight reduction efforts.
Innovation Solution
Implementing a control scheme that monitors operating conditions and applies specific control techniques, such as field weakening, regenerative configuration, or short-circuiting, to maintain DC bus voltage below the overvoltage threshold, especially at high motor speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-channel motor drive systems are designed with redundancy for fault tolerance, then system reliability is improved, but device complexity increases
Solution Approach 1:
The motor drive system is divided into multiple independent channels, each with its own inverter and control circuitry. This segmentation allows one channel to fail while the other continues to operate, providing fault tolerance without requiring complete system redundancy. The segmented architecture enables selective operation of healthy channels while isolating faults.
Solution Approach 2:
The control system is designed to perform multiple functions: normal dual-channel operation, fault detection, and single-channel continued operation. The same hardware infrastructure supports both redundant operation and degraded-mode operation, making the system universal in its operational capabilities without requiring separate systems for each mode.
2Weight of moving object
If permanent magnet motors are used to reduce weight and size, then weight of moving object is reduced, but risk of DC bus overvoltage damage increases
Solution Approach 1:
The control system continuously monitors the DC bus voltage in each channel and provides feedback control. When a fault is detected that could lead to overvoltage, the system adjusts the switching states of the inverter to regulate the DC bus voltage, preventing it from exceeding safe thresholds. This closed-loop control enables safe operation of lightweight permanent magnet motors.
Solution Approach 2:
The control system detects faults before they can cause DC bus overvoltage damage and takes preventive action. By monitoring channel health and predicting potential overvoltage conditions, the system applies corrective control measures in advance, such as adjusting inverter switching or activating protection mechanisms, to prevent the harmful overvoltage effect from occurring.
3Productivity
If the motor continues to rotate after a fault to maintain torque generation, then productivity is maintained, but DC bus voltage may exceed overvoltage threshold
Solution Approach 1:
The control system dynamically adjusts its operation based on real-time channel health status. When a fault is detected in one channel, the system transitions from dual-channel operation to single-channel operation, dynamically reconfiguring the inverter switching patterns and control strategies to maintain torque generation while preventing DC bus overvoltage. This dynamic adaptation allows continued productivity with modified control parameters.
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
Prevents DC bus overvoltage and reduces the risk of permanent damage to motor components by effectively managing induced back emf during faults, ensuring continued operation and safety.
Implementation Method 1
the induced back emf in that channel... could potentially cause the voltage at its DC bus to exceed a DC bus overvoltage threshold
Data Source
AI summary
Methods and apparatus for controlling channels of a multi-channel fault tolerant electric motor system experiencing a particular fault, the control maintaining the voltage in the respective DC bus of the channel with the fault below the DC bus overvoltage threshold for that channel, the particular fault being one that as a result of the continued rotation of the rotor of the motor could potentially cause the voltage in the respective DC bus for the channel with the fault to increase above a DC bus overvoltage threshold for that channel.