Servomotor Current Control for Voltage Saturation Prevention
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Solution Overview
Problem
Existing servomotor technologies face challenges in preventing armature voltage saturation, particularly during high-speed rotation, where excessive d-axis current is supplied, leading to inefficiencies and potential voltage saturation issues during low-speed rotations with high loads.
Innovation Solution
A current control method that dynamically adjusts the phase angle and d-axis current based on voltage command values, using equations Iq=I·cos θ and Id=−|Idmax|·sin θ, to minimize the supply of d-axis current, thereby preventing voltage saturation without excessive current usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If d-axis current is supplied to prevent armature voltage saturation during high-speed rotation, then voltage saturation is prevented, but excessive d-axis current is supplied leading to power consumption increase
Solution Approach 1:
The patent applies dynamics by making the d-axis current supply conditional rather than continuous. The control device dynamically adjusts the d-axis current based on real-time detection of voltage saturation risk, supplying current only when necessary during high-speed rotation to prevent saturation while avoiding excessive current during low-speed operation, thus resolving the contradiction between reliability and energy consumption.
Solution Approach 2:
The patent changes the parameter of d-axis current magnitude based on operating conditions. By detecting voltage saturation risk and adjusting the d-axis current amplitude accordingly - supplying larger current when saturation is detected during high-speed rotation and reducing or eliminating it during low-speed operation - the system prevents saturation while minimizing power consumption.
2Reliability
If d-axis current is supplied to generate offset voltage, then voltage saturation is prevented, but torque generation efficiency decreases due to reactive current
Solution Approach 1:
The system dynamically adjusts d-axis current supply based on detected voltage saturation risk rather than continuously supplying it. By activating d-axis current only when voltage saturation is detected during high-speed rotation and reducing it during low-speed operation, the system prevents saturation while minimizing the impact on torque generation efficiency by limiting reactive current to necessary periods only.
Solution Approach 2:
The patent implements periodic detection and conditional d-axis current supply based on operating conditions. The control device periodically monitors for voltage saturation risk and activates d-axis current in periodic cycles only when high-speed rotation and saturation risk are detected, rather than continuous supply, thus maintaining productivity while preventing saturation.
3Force
If large amount of q-axis current is supplied to generate torque, then torque output increases, but armature voltage saturation occurs during high-speed rotation
Solution Approach 1:
The patent applies the counterweight principle by using d-axis current to generate an offset voltage that counteracts the back electromotive force during high-speed rotation. This offset voltage compensates for the voltage drop caused by large q-axis current, allowing high torque output to be maintained without causing armature voltage saturation, thus resolving the contradiction between force output and voltage saturation prevention.
Solution Approach 2:
The d-axis current acts as an intermediary mechanism that mediates between the conflicting requirements of high q-axis current for torque and voltage saturation prevention. By introducing d-axis current as a mediating element that generates offset voltage, the system enables large q-axis current to be supplied for high torque while the d-axis component prevents saturation through voltage compensation.
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
This approach allows for stable torque generation during high-speed rotations and efficient operation during low-speed, high-load conditions by minimizing unnecessary d-axis current, reducing power consumption and preventing voltage saturation.
Implementation Method 1
a relative rotation power of the magnetic field and the armature is generated based on an interaction between the magnetic field flux generated by the magnetic field and an armature magnetic flux generated by applying an armature voltage to the armature winding of each phase
Implementation Method 2
the influence of back electromotive force that occurs in an armature can be reduced, thereby preventing the voltage saturation
Data Source
AI summary
A method of controlling a current by supplying a d-axis current in order to prevent a voltage saturation includes: defining an amount of the d-axis current as Id=|Idmax|·sin θ; continuously comparing a voltage command value with the voltage command value threshold Vo in a predetermined cycle; extracting a predetermined number No of latest comparison results in terms of time; setting a phase angle θ to be 0° when a number N of the comparison results out of the predetermined number No of the comparison results is equal to or less than an integer Nb; and increasing the phase angle θ depending on largeness of the number N when the number N is more than the integer Nb.