Inductance Estimation via Signal Injection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current self-commissioning procedures for synchronous reluctance motors struggle to accurately estimate inductances at various operating points due to saturation and cross-magnetization effects, often requiring the motor to be disconnected from the mechanical load and inducing torque, which complicates standstill testing.
Innovation Solution
A method involving a system with two current regulators, where one regulator receives an alternating current (AC) signal and the other a predetermined direct current (DC) signal, allowing for the superimposition of a varying signal to estimate inductance and flux linkage while maintaining the motor at standstill or quasi-standstill, using a Goertzel algorithm to analyze the contribution signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If torque ramps are induced in the motor to estimate inductances at operating points where both i d and i q are non-zero, then inductance estimation coverage is improved, but the motor starts rotating and requires disconnection from mechanical load
Solution Approach 1:
The patent applies periodic action by using high-frequency signal injection superimposed on the drive currents. This periodic signal enables inductance estimation without requiring the motor to rotate or be disconnected from mechanical load, thus maintaining ease of operation while achieving comprehensive inductance estimation coverage across all operating points including those where both i d and i q are non-zero.
2Measurement precision
If high-frequency signal injection is used for inductance estimation, then measurement precision is improved, but saturation and cross-magnetization effects cause estimation inaccuracies
Solution Approach 1:
The patent addresses saturation and cross-magnetization effects by dynamically adjusting estimation parameters based on the operating point. The system modifies the high-frequency signal injection strategy and estimation algorithms according to the actual magnetic saturation level and cross-magnetization conditions, thereby maintaining measurement precision and reliability across varying operating conditions including saturated states.
3Ease of operation
If standstill tests are performed with direct connection to mechanical load, then safety and operational convenience are improved, but current procedures cannot estimate inductances at all operating points
Solution Approach 1:
The patent implements universality by developing a high-frequency signal injection method that functions across all operating points including standstill conditions with mechanical load connection. This multi-functional approach enables the same estimation procedure to accurately determine inductances whether the motor is at standstill or rotating, whether connected to mechanical load or not, and across the entire range of i d and i q values, thus achieving both operational convenience and comprehensive coverage.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a method of estimating inductances and flux linkages of an electrical machine, which electrical machine is supplied with drive currents via current regulators and actual values of the drive currents are measured and fed back to the current regulators such that closed-loop control is provided. The method comprises the steps of providing one of the current regulators with an alternating current (AC) value either for a direct axis current reference i*d or for a quadrature axis current reference i*q of the machine current vector, while providing another one of the current regulators with a predetermined direct current (DC) value for the remaining one of the two current references i*d and i*q . Subsequently, after a predetermined time period has expired, a varying signal is superimposed onto an output signal generated by the current regulator in response to the AC value. Finally, a contribution signal, which corresponds to the contribution of the superimposed varying signal to the drive currents, is determined, and the machine inductances and flux linkages are estimated on the basis of the contribution signal.