PMSM D-Q Axis Inductance Estimation Using a Back-EMF Observer
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Solution Overview
Problem
Existing methods for estimating d-q axis inductance of permanent magnet synchronous motors (PMSM) are complex and accuracy-dependent on precise rotor locking, making them inefficient and prone to errors.
Innovation Solution
A method using a back EMF observer to estimate d-q axis inductance by disabling one phase and enabling the other two, incorporating a DC motor control block to lock the rotor at zero angular speed, and iteratively calculating equivalent motor inductances to accurately determine d-q axis inductance without requiring specific electrical angle locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the existing inductance measurement method is used to accurately lock the rotor at a specific electrical angle, then the d-q axis inductance estimation accuracy is improved, but the measurement procedure becomes complicated and more time-consuming
Solution Approach 1:
The patent replaces the mechanical rotor locking system with an electrical control system. By injecting test voltages and using back EMF observers, the system electronically determines inductance parameters without requiring physical rotor positioning mechanisms, thereby simplifying the measurement procedure while maintaining accuracy
Solution Approach 2:
The patent changes the measurement approach by injecting test voltages at different frequencies and amplitudes, and by varying the phase enabling/disabling patterns. This allows the system to extract inductance information through parameter variation rather than through precise mechanical positioning, reducing procedural complexity
2Measurement precision
If multiple measurements are taken in the vicinity of a fixed electrical angle to obtain inductance information, then the accuracy is improved through averaging, but the measurement time increases
Solution Approach 1:
The patent employs periodic injection of test voltages at different phases and frequencies. By using periodic excitation signals and analyzing the periodic back EMF responses, the system obtains multiple measurement points automatically through the periodic nature of the signals, achieving accurate averaging without extending actual measurement time
Solution Approach 2:
The patent enables continuous measurement by injecting test voltages and continuously monitoring back EMF throughout the measurement process. Rather than taking discrete measurements at different angles, the system continuously extracts inductance information from the ongoing electrical signals, eliminating idle time between measurements
3Ease of operation
If a back EMF observer is used to estimate rotor position and speed, then the measurement procedure is simplified, but the inductance estimation accuracy may be compromised without precise rotor locking
Solution Approach 1:
The patent uses back EMF observers that continuously monitor the electrical signals and provide feedback on rotor position and speed estimates. This feedback is then used to adjust the measurement process and calculate accurate inductance parameters, maintaining precision while simplifying the procedure through automated electronic control
Solution Approach 2:
The patent introduces the back EMF observer as an intermediary that bridges the gap between simplified measurement procedures and accurate inductance estimation. The observer processes the electrical signals and extracts precise rotor information, enabling accurate measurements without requiring complex mechanical positioning
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 simplifies the estimation process, improves accuracy, and allows for precise d-q axis inductance calculation without needing precise rotor position information, applicable to both surface and interior PMSM structures with minimal deviation from actual values.
Implementation Method 1
estimating back EMF by the back EMF observer so as to acquire the equivalent motor inductance
Data Source
AI summary
A method of estimating a d-q axis inductance of a permanent magnet synchronous motor includes the following steps. First, building an equivalent motor control block through enabling two of the three phases, and disabling the remaining one of the three phases, and locking a rotor. Afterward, incorporating a back EMF observer into a DC motor control block, and making the DC motor control block correspond to the back EMF observer by commanding an angular speed of the DC motor control block to be zero. Afterward, introducing the equivalent motor control block into the DC motor control block, and using the back EMF observer to estimate the back EMF, and repeating above steps taking turns to disable one phase so as to obtain three sets of motor inductances respectively. Finally, estimating the d-q axis inductance by introducing the three sets of equivalent motor inductances into an inductance relational equation.