AC Motor Current Estimation via Inverted DQ Synchronization
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Solution Overview
Problem
Existing AC motor control systems face challenges in achieving stable electric current estimation accuracy, particularly at higher rotation speeds, due to phase delays in current estimate values used across cycles, leading to deteriorated torque control and potential system breakdowns.
Innovation Solution
The control apparatus employs an electric current estimation unit that performs inverted dq conversion and dq conversion at predetermined intervals to synchronize electric current estimates with the current rotation angle, removing phase delays and improving estimation accuracy without increasing system volume or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric current estimation is performed using previous cycle values without synchronization, then calculation simplicity is maintained, but estimation accuracy deteriorates due to phase delays at higher rotation speeds
Solution Approach 1:
The invention performs preliminary synchronization of the previous cycle's electric current estimate values with the current rotation angle before using them in estimation calculations. This preliminary action (synchronization) ensures that phase delays are corrected in advance, maintaining estimation accuracy without adding complex real-time adjustment mechanisms during the main calculation cycle.
Solution Approach 2:
The invention uses feedback by continuously updating the electric current estimate values based on the synchronized previous cycle data and current sensor readings. The estimation unit feeds back corrected values that account for rotation angle changes, improving accuracy while maintaining a manageable calculation structure through iterative refinement.
2Measurement precision
If multiple electric current sensors are used to detect all phases, then estimation accuracy is improved, but system volume and cost increase
Solution Approach 1:
The invention creates a virtual copy of the electric current values for non-detected phases by calculating estimate values based on the detected phase current and synchronization data. Instead of using physical sensors for all phases, the system generates accurate virtual representations through mathematical estimation, reducing sensor quantity while maintaining detection accuracy.
Solution Approach 2:
The invention introduces an intermediary estimation mechanism that bridges the gap between single-phase detection and three-phase control. The electric current estimation unit acts as an intermediary, translating single-phase sensor data into accurate three-phase current estimates through synchronization and calculation, eliminating the need for multiple sensors.
3Device complexity
If single phase sensing is used to reduce cost and volume, then system compactness is improved, but estimation stability deteriorates under varying operation conditions
Solution Approach 1:
The invention applies dynamics by making the estimation calculation adaptive to varying operation conditions through rotation angle-based synchronization. The system dynamically adjusts the estimation process based on the current rotation angle and speed, ensuring stable and accurate estimates across different operating conditions rather than using a fixed static calculation method.
Data Source
AI summary
A control apparatus of an AC motor improves an electric current estimation accuracy of the AC motor, which includes a three phase motor with an electric current detector to detect an electric current detection value of one of the three phases (a sensor phase). The control apparatus includes an electric current estimation unit that repeatedly performs an inverted dq conversion and a dq conversion. The inverted dq conversion calculates an electric current estimate values for phases other than the sensor phase based on the d/q axis electric current estimate values of a previous cycle. The dq conversion calculates the d/q axis electric current estimate values of a current cycle in a rotation coordinate system of the AC motor based on the electric current estimate values calculated by the inverted dq conversion and the electric current detection value of the sensor phase detected by the electric current detector.