Synchronous Inductance Identification via Voltage Pulse Sequences
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Solution Overview
Problem
Existing methods for estimating inductances in synchronous salient pole machines, particularly with single current measurement, face challenges such as unreliable results due to rotor position uncertainty and mechanical constraints, leading to inefficient control of frequency converters.
Innovation Solution
A method utilizing a voltage pulse test sequence applied in different directions to measure currents, allowing for the calculation of inverse inductance values that vary sinusoidally with the rotor angle, enabling identification of synchronous inductances without rotor rotation and using only one output current measurement, implemented in a frequency converter without additional instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only one output current measurement is used in frequency converter, then cost is reduced and device complexity is lowered, but measurement precision of inductance identification deteriorates
Solution Approach 1:
The patent segments the measurement process by applying voltage pulses in different directions (positive and negative sequences) to extract multiple inductance parameters from a single current measurement. This allows the system to obtain d-axis and q-axis synchronous inductances without requiring multiple simultaneous current sensors.
Solution Approach 2:
The patent uses periodic voltage pulse sequences with different polarities applied to the machine phases. By alternating between positive and negative voltage sequences, the system can measure current responses that reveal different inductance characteristics, enabling accurate identification with minimal sensing hardware.
2Measurement precision
If rotor position is used for inductance identification, then measurement precision improves, but reliability deteriorates due to rotor position uncertainty and mechanical constraints
Solution Approach 1:
The patent makes the system self-sufficient by eliminating the need for external rotor position sensors or mechanical positioning mechanisms. The inductance identification is performed using only the current measurement already available in the frequency converter, combined with applied voltage pulse sequences, making the process reliable under all mechanical conditions.
Solution Approach 2:
The patent changes the voltage application parameters (magnitude, direction, sequence) rather than relying on rotor position. By varying the voltage pulse characteristics and measuring the resulting current responses, the system can identify inductance parameters without needing to control or know the rotor position, thereby improving reliability.
3Measurement precision
If voltage pulse test sequence is applied in different directions, then inductance identification accuracy improves, but testing time increases
Solution Approach 1:
The patent performs preliminary voltage pulse tests in both positive and negative directions during the identification process. By pre-applying these test sequences and measuring the resulting currents, the system can calculate synchronous inductances accurately without requiring extended testing periods or iterative procedures.
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
Enables rapid and accurate identification of synchronous inductances, facilitating efficient control of salient pole machines by determining direct and quadrature axis inductances, and rotor angle, thus improving operational reliability and reducing costs.
Implementation Method 1
When voltage is fed to a salient pole machine, the change rate of stator current depends on the angle of the voltage and on the rotor angle
Data Source
Figure 1~2
Figure 3~4
AI summary
A frequency converter and a method of identifying synchronous inductances of a salient pole synchronous machine connected to a frequency converter having a current measurement in the intermediate voltage circuit. The method comprises providing a voltage pulse with a known magnitude to each phase of the salient pole synchronous machine with the frequency converter, measuring the current in the intermediate voltage circuit at the end of each voltage pulse, calculating for each provided voltage pulse the inverse value of inductance as the measured current divided by the magnitude of the voltage and by duration of the voltage pulse, and solving the synchronous inductances from the calculated inverse values of inductances