Inductance Determination for Permanent Magnet Synchronous Machines
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Solution Overview
Problem
Existing methods for determining the flux and torque inductances of permanent magnet synchronous machines are inadequate for reliable control, particularly at low speeds and standstill conditions, and do not account for rotor position asymmetries effectively.
Innovation Solution
A control method that applies voltage vectors in both positive and negative directions to each phase of the machine, measuring current responses to determine rotor position and calculate flux and torque inductances, accounting for magnetic saturation effects by averaging and differencing current variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage vectors are applied in both positive and negative directions to measure current responses, then measurement precision of inductances is improved, but device complexity and measurement time increase
Solution Approach 1:
The measurement procedure is segmented into distinct phases: applying voltage vectors in positive direction, measuring current responses, applying voltage vectors in negative direction, and measuring current responses. This segmentation allows systematic extraction of inductance values from different measurement conditions, improving accuracy while maintaining procedural clarity
Solution Approach 2:
The method employs periodic application of voltage vectors in alternating positive and negative directions to each phase. This periodic action enables the system to capture current responses under different polarity conditions, which are then used to calculate accurate inductance values that account for magnetic saturation effects
2Measurement precision
If current measurements are taken at multiple points during voltage pulse application, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The method performs preliminary measurements of current responses during the application of voltage vectors in both positive and negative directions. By capturing current values at specific time points (such as at the end of voltage pulse application and during decay), the system prepares data that can be directly used for inductance calculation without requiring additional measurement steps
Solution Approach 2:
The method measures current responses at more time points than the absolute minimum required (measuring during both the voltage application phase and the decay phase). This excessive measurement approach ensures that sufficient data is captured to accurately determine inductance values while the measurements are performed efficiently in a single measurement cycle
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
This method enables accurate determination of flux and torque inductances regardless of rotor type or salience, providing consistent control and reference models for variable speed drives, even at low speeds and standstill.
Implementation Method 1
accounting for magnetic saturation effects by averaging and differencing current variations
Data Source
Figure 1~2B
Figure 3~4
Figure 5
AI summary
The invention relates to a control method implemented in a variable speed drive for determining the inductances (Ld, Lq) of a permanent magnet synchronous machine comprising three phases (a, b, c), each oriented along a direction, a stator, and a rotor. For each phase, one after the other, said method includes steps of: applying, along the direction of the phase (a, b, c), a voltage vector (V1, V3, V5) in the positive direction and a voltage vector (V2, V4, V6) in the negative direction for a predetermined duration; measuring the current obtained in the phase after applying the voltage vectors in both directions; determining an angle (? r ) for the position of the rotor in relation to the stator based on the measured current; and determining the flow (Ld) and torque (Lq) inductances of the machine based on the predetermined angle (? r ).