Power Conversion Device Inductance Estimation Low Speed Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion devices for position sensorless control of permanent magnet motors fail to accurately estimate inductance in the low speed range from a halting state to about 10% of base speed.
Innovation Solution
A power conversion device incorporating a harmonic voltage generation unit that superimposes harmonic voltages on voltage commands and an inductance estimation unit, which estimates inductance based on harmonic currents and switching signals, enabling accurate inductance estimation across all speed ranges including low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the harmonic superimposition method is applied to position sensorless control in medium to high speed range, then extended electromotive force based control is achieved, but inductance estimation during operation in low speed range cannot be realized
Solution Approach 1:
The patent applies dynamics by making the inductance estimation method adaptive to different speed ranges. The system dynamically switches between estimation methods: using extended electromotive force based control for medium to high speeds and harmonic voltage superimposition for low speeds, ensuring reliable operation across the entire speed range without compromising measurement precision at any stage
Solution Approach 2:
The patent changes the control parameters based on speed range. At low speeds, it superimposes harmonic voltages on voltage commands and estimates inductance from harmonic currents. At medium to high speeds, it uses extended electromotive force based control. This parameter change approach resolves the contradiction by optimizing the estimation method for each operating condition
2Measurement precision
If inductance estimation is performed using harmonic superimposition method, then accurate inductance estimation can be achieved in low speed range, but the method cannot be applied during operation in medium to high speed range
Solution Approach 1:
The patent creates a universal inductance estimation system that can operate across all speed ranges by implementing multiple estimation methods. The harmonic superimposition method provides accurate inductance estimation at low speeds, while the extended electromotive force based control handles medium to high speeds, making the system universally applicable throughout the entire operating range
3Device complexity
If position sensorless control is implemented without accurate inductance estimation, then the system structure is simplified, but torque control accuracy deteriorates
Solution Approach 1:
The patent implements self-service by enabling the motor control system to automatically estimate its own inductance parameters during operation without external measurement equipment or position sensors. The harmonic voltage superimposition method allows the system to extract inductance information from its own current responses, maintaining torque control accuracy while keeping the system structure simple
Data Source
AI summary
A power conversion device includes a harmonic voltage generation unit that superimposes dc-axis and qc-axis harmonic voltages on dc-axis and qc-axis voltage commands in accordance with a switching signal; and an inductance estimation unit that estimates dc-axis inductance and qc-axis inductance on a basis of dc-axis and qc-axis harmonic currents, amplitude values of the harmonic voltages, and the switching signal.