Asynchronous Machine Torque Control via Dynamic Slew Rate Adjustment
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Solution Overview
Problem
Asynchronous machines, such as induction machines, face challenges in achieving high efficiency and fast torque response due to the inherent lagging characteristics of rotor flux with respect to stator current, leading to suboptimal performance in controlling torque.
Innovation Solution
The method involves dynamically adjusting torque and current slew rates based on rotor flux feedback, where higher rotor flux ratios enable faster slew rates and lower ratios result in slower slew rates, allowing for improved torque control and efficiency by using control signals to set these rates accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If current command slew rates are set to relatively lower values to improve machine efficiency, then efficiency is improved, but torque response speed deteriorates
Solution Approach 1:
The patent applies dynamics by making the slew rate adjustable rather than fixed. The system dynamically changes the slew rate based on operating conditions, allowing it to be higher when fast torque response is needed and lower when efficiency is prioritized, thus resolving the contradiction between speed and energy loss
Solution Approach 2:
The patent changes the parameter of slew rate based on rotor flux conditions. By monitoring rotor flux and adjusting the slew rate parameter accordingly, the system optimizes the trade-off between torque response speed and machine efficiency under different operating conditions
2Speed
If rotor flux is maintained at a constant value above a certain level to achieve faster torque response, then torque response speed is improved, but machine and inverter efficiency deteriorate
Solution Approach 1:
Instead of maintaining rotor flux at a constant high level, the system dynamically adjusts the flux level based on torque demand and operating conditions. This allows the flux to be high when fast response is needed and lower when efficiency is prioritized, resolving the contradiction between speed and energy loss
Solution Approach 2:
The system changes the rotor flux parameter dynamically based on operating conditions and torque commands, optimizing the balance between torque response speed and inverter efficiency rather than maintaining a fixed flux level
Data Source
AI summary
Embodiments of the present disclosure relate to methods, systems and apparatus for adjusting current and/or torque commands used to control operation of an asynchronous machine based on rotor flux of the asynchronous machine.