Dynamic DC Offset Compensation in PMSM Phase Current Measurement
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Solution Overview
Problem
Permanent magnet synchronous motors (PMSM) face torque ripple issues due to dynamic components of DC offset in measured phase current, which existing methods struggle to account for effectively, especially as they vary with time and temperature.
Innovation Solution
A motor control system with a dynamic offset compensation control module that periodically disables the inverter controller to measure phase current, determining an offset correction value based on these measurements, ensuring accurate compensation for the dynamic DC offset component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple offset measurement approach is used to account for the fixed component of DC offset, then the device complexity is reduced, but the measurement precision deteriorates because the dynamic component varying with time and temperature cannot be accounted for
Solution Approach 1:
The system performs offset measurements at periodic intervals by temporarily disabling the inverter controller. This periodic action allows the system to capture dynamic offset variations over time and temperature without requiring continuous complex compensation, thus resolving the contradiction between simplicity and precision
Solution Approach 2:
The system performs offset measurements during idle periods before normal operation resumes. By preparing the offset correction value in advance during periods when the motor is not actively running, the system ensures accurate compensation is ready when needed without interfering with normal operation
2Measurement precision
If the inverter controller is continuously disabled to measure phase current for offset determination, then the measurement precision improves, but the productivity deteriorates due to continuous interruption of motor operation
Solution Approach 1:
Instead of continuous disabling, the system uses periodic measurements at predetermined intervals. This allows accurate offset characterization while minimizing interruption to motor operation, thus resolving the contradiction between measurement precision and productivity
Solution Approach 2:
The system performs offset measurements during naturally occurring idle periods when the motor would otherwise be stationary. By utilizing these self-generated opportunities for measurement, the system obtains accurate data without requiring additional operational interruptions
3Measurement precision
If offset measurements are performed frequently to capture dynamic variations, then the measurement precision improves, but the loss of time increases due to repeated disabling of the inverter controller
Solution Approach 1:
The system determines optimal measurement intervals that capture dynamic offset variations without excessive frequency. By balancing the measurement period against the rate of dynamic variation, the system achieves adequate precision while minimizing time loss
Solution Approach 2:
The system adjusts the measurement frequency based on operating conditions such as temperature change rates and motor load variations. By dynamically changing the measurement interval parameter, the system maintains precision during rapid changes while reducing measurements during stable conditions
Data Source
AI summary
A motor control system for determining an offset correction value is provided. The motor control system includes a motor, an inverter, an inverter controller, and a dynamic offset compensation control module. The inverter is configured to transmit the phase current to the motor. The inverter controller determines the phase current to the motor. The dynamic offset compensation control module is in communication with the inverter controller and the motor, and is configured to perform a method at a fixed periodic interval to determine the offset correction value.