Two-Stage DC Current Injection for PMSM Rotor Positioning
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Solution Overview
Problem
Existing sensorless PMSM motor control techniques with sinusoidal BEMF face limitations in achieving maximum torque per ampere, particularly during startup, due to position detection failures and rotor misalignment issues with single-stage dc current injection methods.
Innovation Solution
A two-stage dc current injection method is implemented using a synchronously rotating reference frame current regulator, with configurable current amplitudes and angles for each stage, to align the rotor magnet position effectively, allowing for robust control and reduced rotor shaft hunting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If single-stage dc current injection is used to position the rotor, then the control algorithm is simple, but position detection failure occurs and rotor misalignment happens
Solution Approach 1:
The patent divides the single-stage dc current injection into two sequential stages. The first stage positions the rotor to an intermediate position with specific current magnitude and angle, then the second stage moves it to the final predetermined position. This segmentation resolves the contradiction by maintaining algorithmic simplicity while eliminating position detection failures through the intermediate positioning step.
Solution Approach 2:
The first stage of dc current injection performs a preliminary action by positioning the rotor to an intermediate position before the final positioning action in the second stage. This preliminary positioning prevents the misalignment and position detection failures that occur with direct single-stage injection, while keeping the overall control algorithm relatively simple.
2Power
If dc current injection is used to achieve maximum torque per ampere, then torque efficiency is improved, but rotor shaft hunting occurs with large inertia loads
Solution Approach 1:
The two-stage injection scheme segments the torque-building process. The first stage establishes partial alignment with controlled current parameters, allowing the rotor to settle before the second stage completes the positioning. This prevents the oscillatory hunting behavior that occurs with single-stage high-magnitude injection, especially with large inertia loads, while still achieving maximum torque per ampere capability.
Solution Approach 2:
The patent dynamically adjusts the current magnitude and angle parameters between the two stages. The first stage uses specific current parameters suitable for initial positioning, then the second stage uses different parameters optimized for final positioning. This dynamic parameter adjustment stabilizes the rotor shaft during the positioning process while maintaining torque efficiency.
3Ease of manufacture
If momentary backward shaft movement is allowed during startup, then dc current injection implementation is simplified, but this limits application scope
Solution Approach 1:
The two-stage injection method segments the rotor positioning process into controlled steps that can achieve positioning without requiring momentary backward shaft movement. The first stage creates an intermediate position through controlled current injection, and the second stage completes the positioning, eliminating the need for backward movement while maintaining implementation simplicity.
Solution Approach 2:
The patent replaces the mechanical backward shaft movement approach with an electrical control approach using two-stage current injection. Instead of allowing mechanical reversal, the system uses controlled electrical current sequences to achieve the same positioning effect, thereby expanding application scope to applications where backward movement is not permitted while keeping implementation simple.
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 enhances the robustness of dc current injection, ensuring accurate rotor positioning and enabling maximum torque per ampere capability, even with high inertia loads, by avoiding misalignment and position detection failures.
Implementation Method 1
a first current command and a first angle command are supplied to a current regulator for a first parking time, to move the rotor to an intermediate position; and a second current command and a second angle command are supplied to the current regulator for a second parking time, to move the rotor to a predetermined position
Data Source
AI summary
A method and system for controlling a current regulator motor control for parking a motor rotor in a predetermined position, wherein a first current command and a first angle command are supplied to a current regulator for a first parking time, to move the rotor to an intermediate position; and a second current command and a second angle command are supplied to the current regulator for a second parking time, to move the rotor to a predetermined position. The current regulator may have a normal voltage output range, and a circuit may be provided for limiting a voltage output of the current regulator to a reduced voltage output range for at least a portion of the parking time. Advantageously the motor is a permanent-magnet synchronous motor with sinusoidal back-EMF.