PMSM Torque Control via DC Link Voltage Normalization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Permanent magnet synchronous motors (PMSMs) face instability in torque control due to changes in speed, temperature, direct link voltage, and other parameters, requiring a control method that maintains stable torque transfer regardless of these variations.
Innovation Solution
A method using speed-torque lookup tables to normalize rotor speed based on changes in DC link voltage and parameters, adjusting the change ratio of the DC link voltage through a change ratio control value to ensure precise torque control, even when the voltage limiting circle of the inverter output voltage is smaller than the command voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DC link voltage changes due to temperature, speed, or other parameter variations, then the torque control precision deteriorates, but using a fixed speed-torque lookup table simplifies the control structure
Solution Approach 1:
The patent applies dynamics by making the speed-torque lookup table adaptive rather than fixed. The table is dynamically adjusted based on detected DC link voltage, allowing the control system to maintain precision across varying operating conditions. This resolves the contradiction by enabling the simple lookup table structure to adapt to changing voltage conditions.
Solution Approach 2:
The patent changes the parameter of the lookup table based on DC link voltage variations. By detecting voltage changes and adjusting the lookup table parameters accordingly, the system maintains torque control precision despite voltage fluctuations, while preserving the simplicity of the lookup table approach.
2Measurement precision
If the speed-torque lookup table is adjusted frequently to maintain precision under varying conditions, then torque control precision improves, but the computational complexity and memory requirements increase
Solution Approach 1:
The system dynamically adjusts the lookup table only when necessary based on DC link voltage changes, rather than continuously or frequently. This selective dynamic adjustment maintains precision while avoiding unnecessary computational overhead and memory operations.
Solution Approach 2:
The patent modifies lookup table parameters based on detected voltage changes, but only when actual voltage variation occurs. This approach improves precision through parameter adaptation while minimizing computational complexity by avoiding unnecessary adjustments.
3Reliability
If the inverter output voltage is limited due to parameter changes, then the voltage limiting circle becomes smaller than the command voltage, but adjusting the change ratio control value maintains torque stability
Solution Approach 1:
The patent uses feedback by detecting the DC link voltage and using this information to adjust the lookup table parameters. This closed-loop approach ensures torque stability despite voltage limiting conditions, as the system continuously adapts to actual voltage levels.
Solution Approach 2:
The patent changes the lookup table parameters based on the detected voltage limiting conditions, allowing the system to maintain reliable torque transfer even when the inverter output voltage is constrained below the command voltage level.
Data Source
AI summary
A method of controlling torque of a permanent magnet synchronous motor (PMSM) by using a speed-torque lookup table may include: receiving a current direct-current (DC) link voltage of an inverter configured to drive the PMSM and a speed of a rotor of the PMSM; calculating a change ratio of a DC link voltage based on the current DC link voltage and a DC link voltage at a time when the speed-torque lookup table is generated; calculating a normalized speed of the rotor according to a change in the DC link voltage by using the speed of the rotor and the change ratio of the DC link voltage; and/or transferring the normalized speed of the rotor as an input to the speed-torque lookup table.