Drive device for AC motor, compressor drive device, and refrigeration cycle device
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Solution Overview
Problem
Existing drive devices for AC motors face challenges in implementing advanced control methods for reducing torque and speed pulsations, particularly in sensorless control systems, which require significant man-hours for reliability evaluation and are difficult to integrate into general-purpose devices.
Innovation Solution
A drive device incorporating an adaptive observation unit, speed control unit, phase lead amount calculation unit, vibration suppression control unit, and torque control unit to estimate angular velocity and suppress speed pulsations in AC motors, allowing for easy implementation of extended functions without modifying the core adaptive observer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If position sensorless control is used to reduce cost and improve ease of manufacture, then sensor cost is eliminated and ease of manufacture is improved, but speed estimation response is limited to several hundred rad/s and high-frequency pulsations cannot be accurately estimated
Solution Approach 1:
The speed estimation function is segmented into two independent parallel units: a basic speed estimation unit for general operation and a high-frequency speed estimation unit for pulsation suppression. Each unit operates independently with its own bandwidth characteristics, allowing the system to maintain low-cost sensorless control while achieving high-frequency response capability when needed.
Solution Approach 2:
The system dynamically switches between different estimation units based on frequency requirements. The basic estimation unit handles low-frequency operation while the high-frequency unit activates for pulsation suppression, optimizing performance across different operating conditions without requiring full high-bandwidth estimation at all times.
2Measurement precision
If two angular velocity estimation units connected in parallel are added to enhance speed estimation response, then high-frequency speed pulsations can be accurately estimated, but device complexity increases and reliability evaluation requires significant man-hours
Solution Approach 1:
The estimation system is divided into specialized units with distinct functions: basic estimation for general speed control and high-frequency estimation specifically for pulsation suppression. This segmentation allows each unit to be optimized for its specific purpose while maintaining overall system manageability and reducing integration complexity.
Solution Approach 2:
The high-frequency speed estimation unit serves multiple purposes: it suppresses speed pulsations, reduces vibration, and improves overall system stability. By designing this unit with multi-functionality, the added complexity is justified by the multiple benefits it provides across different operational aspects.
3Object-affected harmful factors
If advanced control methods for reducing torque and speed pulsations are implemented, then vibration and noise are reduced, but the control system becomes more complex and difficult to integrate into general-purpose devices
Solution Approach 1:
The control system dynamically activates advanced pulsation suppression control only when high-frequency pulsations are detected, rather than continuously operating complex control algorithms. This dynamic approach reduces vibration and noise when needed while keeping the control system simple for general-purpose operation, facilitating easier integration.
4Speed
If the adaptive observation unit is modified to improve speed estimation response, then high-frequency pulsations can be suppressed, but any change in position or speed estimation method exerts wide-ranging influences requiring extensive reliability evaluation
Solution Approach 1:
By segmenting the estimation system into independent parallel units rather than modifying the core adaptive observer, changes are isolated to specific functional modules. This modular approach limits the scope of reliability evaluation needed, as modifications in one unit do not necessarily affect the other units or the overall system stability.
Data Source
AI summary
A drive device for an AC motor includes: an adaptive observation unit that adaptively estimates an angular velocity of a rotor of an AC motor; a speed control unit that determines a first torque command with which an angular velocity command matches an average value of an estimated angular velocity; a phase lead amount calculation unit that calculates, based on a disturbance frequency, a phase lead amount of a transfer function from a true angular velocity to a model deviation; a vibration suppression control unit that determines, based on a frequency of load torque pulsations, the model deviation, and the phase lead amount, a second torque command with which speed pulsations in the AC motor are suppressed; and a torque control unit that controls a torque of the AC motor based on the first torque command and the second torque command.