Electric Motor Electrical Parameter Estimation via Signal Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric motor drive systems face challenges in accurately determining resistance and inductance due to limitations in measuring real phase voltage, especially with voltage source inverters introducing parasitic resistance and deadtime, which affects precision in low-voltage applications.
Innovation Solution
A method and apparatus that utilize signal modulation and demodulation techniques to estimate resistance and inductance by controlling DC and AC current components independently, allowing for precise measurement of electrical parameters without requiring real phase voltage measurement, and overcoming the effects of inverter deadtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If real phase voltage measurement is used to determine resistance and inductance, then measurement precision is improved, but device complexity increases due to additional sensors and signal conditioning requirements
Solution Approach 1:
The patent introduces signal injection and demodulation as an intermediary measurement approach. Instead of directly measuring phase voltage with complex sensors, the system injects known test signals through the inverter and uses demodulation of current responses to indirectly determine electrical parameters. This mediator approach achieves high measurement precision while avoiding the complexity of direct phase voltage measurement hardware.
2Adaptability or versatility
If voltage source inverter is used to provide AC supply, then adaptability to different motor applications is improved, but measurement precision deteriorates due to parasitic resistance and deadtime effects
Solution Approach 1:
The patent converts the harmful deadtime and parasitic resistance effects into beneficial measurement opportunities. By injecting test signals during deadtime intervals and using the known inverter switching states, the system transforms the previously problematic non-ideal inverter behavior into a characterized model that enables accurate parameter extraction. The deadtime, normally causing voltage errors, becomes a known perturbation that can be compensated for in the measurement algorithm.
Solution Approach 2:
The patent changes the measurement approach from direct voltage/current sensing to impedance-based parameter extraction. By varying test signal frequencies and amplitudes, and measuring the resulting current responses, the system extracts resistance and inductance values that are independent of the inverter's parasitic effects. This parameter transformation allows accurate motor characterization despite the non-ideal inverter behavior.
3Use of energy by moving object
If coil resistance is very small in low-voltage applications, then power consumption is reduced, but measurement precision deteriorates because parasite resistances become significant
Solution Approach 1:
The patent applies partial action by using small-amplitude test signals for measurement purposes only, separate from the main power delivery. The measurement signals are sufficiently small to not significantly impact motor operation but large enough to enable precise parameter extraction. This allows the system to maintain low overall power consumption while achieving accurate resistance measurements that would be impossible with the motor's normal operating currents alone.
Data Source
AI summary
A system for determining electrical characteristics of an electric load can comprise a signal modulation circuit that can include a first integral controller configured to control AC reference voltage based on a requested maximum AC current and an estimated maximum AC current, a second integral controller configured to control DC reference voltage based on a requested DC current and an estimated DC current, a signal demodulation circuit including an AC current estimation circuit configured to generate the estimated maximum AC current for the signal modulation circuit, a DC current estimation circuit configured to generate the estimated DC current for the signal modulation circuit, and a resistance and inductance (RL) estimation circuit configured to determine inductance of the electric load based on the estimated maximum AC current and phase shift, wherein the estimated maximum AC current is a value lower than a DC offset current value.