AC Motor Controller Feedback Using Midpoint Potential Detection
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Solution Overview
Problem
Existing controllers for AC rotary electric machines face challenges in accurately compensating for on-duty errors due to dead time, requiring complex circuit configurations and increased calculation loads, especially in estimating detection voltages and loss voltages.
Innovation Solution
A controller for AC rotary electric machines that includes a midpoint potential detection circuit to detect the potential of the connection node in series circuits, allowing for accurate detection of actual on-duty and calculation of on-duty errors, which are then used to correct voltage commands and improve control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dead time compensation is performed using feedforward control with reference model circuit (PLT 1), then on-duty error compensation is achieved, but threshold value determination and tuning work are required
Solution Approach 1:
The patent uses feedback control by detecting the actual on-duty of switching devices and comparing it with the command on-duty to generate a correction value. This correction value is then fed back to adjust the voltage command, achieving accurate on-duty error compensation without complex reference models or threshold switching.
Solution Approach 2:
The system automatically detects and compensates for its own on-duty errors using the midpoint potential detection circuit and feedback control mechanism. The controller self-corrects the voltage command based on the detected actual on-duty, eliminating the need for external tuning or complex compensation circuits.
2Measurement precision
If detection voltage is estimated based on terminal voltage of winding (PLT 2), then dead time compensation is achieved, but voltage detection circuit and filter circuit are required increasing circuit scale
Solution Approach 1:
The patent extracts only the necessary midpoint potential detection function from the complex voltage detection system. By detecting the midpoint potential of the DC power source, the system obtains the required detection information without needing terminal voltage detection circuits or filter circuits, significantly simplifying the overall circuit configuration.
3Measurement precision
If detection voltage and loss voltage are estimated to perform dead time compensation (PLT 2), then compensation is achieved, but calculation processing load increases
Solution Approach 1:
The patent extracts only the essential midpoint potential detection information needed for on-duty error compensation, eliminating the need for complex loss voltage estimation calculations. This approach maintains compensation accuracy while significantly reducing the calculation processing load on the controller.
4Device complexity
If simple circuit configuration is used for on-duty detection, then device complexity is reduced, but on-duty error compensation accuracy may be compromised
Solution Approach 1:
The patent introduces the midpoint potential of the DC power source as an intermediary measurement point. By detecting this midpoint potential, the system can accurately determine the actual on-duty of switching devices without requiring complex voltage detection circuits across the motor terminals, thus achieving both simplicity and accuracy.
Data Source
AI summary
To provide a controller for AC rotary electric machine which can compensate error of the actual on-duty with respect to the command on-duty calculated from command voltage with good accuracy, with a simple circuit configuration. A controller for AC rotary electric machine detects an actual on-duty of the switching device based on the detection value of the midpoint potential which is the potential of the connection node of the series connection in the series circuit; calculates an on-duty error based on the difference between the command on-duty and the actual on-duty; and corrects the voltage command or the command on-duty based on the on-duty error.