Motor Current Determination Using Frequency-Based Filter Delay Compensation
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Solution Overview
Problem
Existing methods for controlling current in electric motors and generators fail to effectively compensate for time delays caused by filters, particularly in high-speed devices with small synchronous resistance and inductance, leading to degraded performance due to high-frequency noise and increased delay times.
Innovation Solution
A method and device that determine the time delay caused by filters by analyzing filter characteristics versus operating frequency, using low-pass, anti-aliasing, and finite impulse response filters, and compensate for this delay to improve current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter of second or more higher order is installed to remove electrical noise, then noise elimination performance is improved, but time delay increases resulting in degradation of control performance
Solution Approach 1:
The patent applies preliminary action by pre-calculating the group delay characteristics of the filter across the operating frequency range and storing these values in a lookup table before actual current measurement and control operations. This allows the system to retrieve pre-computed delay values instantaneously during real-time control, avoiding the need to perform complex delay calculations on-the-fly while maintaining accurate compensation for filter-induced time delays.
Solution Approach 2:
The patent replaces complex real-time mathematical calculations of group delay with a lookup table approach. Instead of computing filter delay characteristics dynamically during control operations, the system substitutes this with pre-stored tabular data that can be quickly accessed and interpolated, effectively replacing a computationally intensive mechanical/mathematical process with a simpler data retrieval operation.
2Loss of time
If bandwidth of filter is set higher to minimize group delay, then time delay is reduced, but high-frequency noise generated due to PWM and switching noise cannot be effectively eliminated
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the compensation amount based on the operating frequency of the electric motor or generator. The system calculates or retrieves the group delay value corresponding to the current operating frequency from a lookup table, and uses this frequency-specific delay value to compensate the measured current signal. This allows optimal noise filtering at each frequency point without being constrained by a fixed filter bandwidth setting.
Solution Approach 2:
The patent implements feedback by continuously monitoring the operating frequency and using this information to adjust the delay compensation amount. The control system measures the actual operating frequency, retrieves the corresponding group delay value from the lookup table, and applies appropriate compensation to the current signal, creating a closed-loop system that adapts to changing operating conditions.
Data Source
AI summary
Provided, according to one embodiment, is a method for determining a current of an electric motor or a generator, the method comprising the steps of: acquiring characteristics of a filter for eliminating noise occurring in a process for determining a current of an electric motor or a generator; determining a time delay caused by the filter, on the basis of a change in a phase indicating the characteristics of the filter, the change resulting from a change in an operating frequency of the electric motor or the generator; and determining the current of the electric motor or the generator by compensating the time delay.