Sensorless Synchronous Motor Torque Control for Low-Speed Stability
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Solution Overview
Problem
Position sensorless motor control systems face challenges in maintaining stability at low speeds due to errors in position estimation and increased load, leading to instability and loss of synchronism.
Innovation Solution
A motor drive method and apparatus that reduces output torque below maximum levels at low speeds and limits acceleration and jerk, using an inverter and controller to regulate power and control the motor, ensuring stability by maintaining torque coefficients and controlling reactive currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If maximum output torque is maintained at low speeds, then power output is maximized, but rotational stability deteriorates and loss of synchronism occurs
Solution Approach 1:
The patent applies dynamics by making the output torque characteristic adjustable and speed-dependent. The control device dynamically changes the torque-speed relationship, reducing torque at low speeds to prevent loss of synchronism while maintaining higher torque at speeds where the motor can operate stably. This dynamic adjustment resolves the contradiction between maximizing power output and maintaining rotational stability.
Solution Approach 2:
The patent changes the torque parameter as a function of speed. By modifying the torque characteristic curve to reduce torque in the low-speed range where instability occurs, the system prevents loss of synchronism. This parameter change allows the motor to operate reliably across the full speed range while avoiding the instability region.
2Device complexity
If position sensorless control is used, then device complexity is reduced, but measurement precision of rotational position deteriorates
Solution Approach 1:
The patent employs feedback mechanisms in the position sensorless control system. The control device continuously monitors motor current, voltage, and speed, using this feedback information to estimate rotor position and adjust control parameters accordingly. This feedback approach enables accurate position estimation without physical sensors, resolving the contradiction between simplified device structure and measurement precision.
Solution Approach 2:
The patent replaces the mechanical position sensing system with an electronic estimation system. Instead of using physical position sensors that会增加device complexity, the system uses electrical measurements and computational algorithms to determine rotor position. This substitution maintains measurement precision while keeping the device structure simple.
3Stability of the object's composition
If output torque is reduced at low speeds, then rotational stability is improved, but power output decreases
Solution Approach 1:
The patent applies dynamics by making the torque-speed relationship adjustable. The control device dynamically reduces torque only in the specific low-speed range where instability occurs, while maintaining full torque capability at higher speeds where the motor operates stably. This dynamic approach resolves the contradiction by optimizing torque output for each operating condition.
Solution Approach 2:
The patent applies local quality by modifying the torque characteristic only in the specific low-speed region where stability problems occur, rather than reducing torque across the entire operating range. This localized adjustment maintains rotational stability where needed while preserving power output capability in the stable operating region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances rotational stability and prevents loss of synchronism, allowing the motor to operate reliably in low-speed ranges by reducing torque and controlling harmonic frequencies, thereby improving operational efficiency and reducing device inefficiencies.
Implementation Method 1
an inverter that regulates supplied power to a motor that is a position sensorless synchronous machine
Implementation Method 2
a motor that is a position sensorless synchronous machine
Implementation Method 3
a controller that outputs a control signal to control the inverter
Data Source
AI summary
A motor drive method is a method of driving a motor by a motor drive apparatus. The motor drive apparatus includes an inverter that regulates supplied power to the motor that is a position sensorless synchronous machine, and includes a controller that outputs a control signal to control the inverter. The method includes reducing output torque of the motor to be less than maximum output torque, in a speed range that is lower than a first speed at which the motor rotates. The maximum torque that is output from the motor is the maximum output torque in a case the motor drive apparatus drives the motor.