Inductance Determination via Steady-State Spectral Analysis
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Solution Overview
Problem
Existing methods for determining the direct and quadrature inductance of electrical machines require measuring phase currents in the transient state, which necessitates specific current sensors and significant computing resources.
Innovation Solution
A method that determines direct and quadrature inductance through spectral analysis of phase currents in the established regime, using a higher test frequency than the rotation frequency, and applying test setpoints with sinusoidal and cosinusoidal components to calculate inductance values without requiring transient current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase currents are measured during transient operation to determine inductances, then inductance determination is achieved, but specific current sensors and significant computational resources are required
Solution Approach 1:
The patent changes the operating condition parameter from transient state to steady state (established regime). By injecting high-frequency signals during steady-state operation and analyzing the spectral components of the resulting currents, the method determines inductances without requiring transient measurements. This parameter change eliminates the need for specialized transient current sensors and reduces computational complexity while maintaining measurement accuracy.
2Measurement precision
If transient phase current measurements are performed, then inductance values can be determined, but the measurement process becomes more complex and resource-intensive
Solution Approach 1:
The patent employs periodic high-frequency signal injection at a frequency higher than the rotation frequency during steady-state operation. By using periodic test signals and analyzing the periodic response through spectral analysis, the method simplifies the measurement process. The periodic action allows extraction of specific spectral peaks that directly provide inductance information without complex transient analysis.
Solution Approach 2:
The patent introduces high-frequency test signals as an intermediary to indirectly determine inductances. Instead of directly measuring transient currents, the method uses high-frequency signal injection and spectral analysis of the resulting steady-state currents as an intermediary process. This intermediary approach simplifies measurement by converting the inductance determination problem into a frequency-domain analysis problem.
3Loss of information
If high frequency signal injection is used for sensorless control, then position information can be obtained, but the system requires additional test frequencies and spectral analysis complexity
Solution Approach 1:
The patent uses electrical vibration in the form of high-frequency signal injection to extract position information and inductance values. By injecting high-frequency signals and analyzing the vibrational response through spectral analysis of steady-state currents, the method obtains position information sensorlessly. The vibration-based approach converts mechanical position information into electrical signal characteristics that can be extracted through frequency analysis.
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 approach eliminates the need for transient current measurements, reducing the requirement for specialized sensors and computational resources while accurately determining inductance values.
Implementation Method 1
the determination of the forward inductance and the quadrature inductance is carried out from a spectral analysis of the electrical quantity resulting from the phase currents
Implementation Method 2
a technique for analyzing a permanent magnet motor without a position sensor using high-frequency voltage injection
Data Source
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AI summary
This method for determining a direct-axis inductance (Ld) and a quadrature-axis inductance (Lq) of an electric machine (102) includes: at least one testing step including: controlling the electric machine (102) so that a stator (106) of the electric machine (102) generates a magnetic field including a magnetic field that rotates at a rotation frequency so as to make a rotor (104) of the electric machine (102) rotate, and a test magnetic field that varies periodically at a test frequency; measuring the phase currents ([i]) that flow through the stator phase windings (A, B, C) of the electric machine (102) during the control of the electric machine (102); determining an amplitude spectrum (S) of an electrical quantity determined on the basis of at least some of the phase currents ([i]); searching, in the amplitude spectrum (S), for at least one peak present at a frequency that is dependent on the test frequency; determining an amplitude (Ipul, Irot) of each peak found; and determining the direct-axis inductance (Ld) and the quadrature-axis inductance (Lq) from the amplitudes (Ipul, Irot) of two peaks found in the one or more testing steps.