Single-Phase Linear Compressor Flux Weakening for Stroke Extension
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Solution Overview
Problem
Linear compressors in refrigerators face limitations in stroke due to back-EMF, which restricts the voltage that can be applied by the inverter, preventing further motor operation.
Innovation Solution
Implementing a single-phase vector-like control scheme that decouples current control to perform dynamic flux weakening, allowing sequential application of voltage limits to achieve the desired stroke without exceeding clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional single-phase motor control is used, then the motor operates within standard voltage limits, but the stroke is restricted due to back-EMF preventing further motor operation
Solution Approach 1:
The patent changes the control parameters by decoupling current control into d-axis and q-axis components, allowing independent manipulation of flux and torque. This enables dynamic flux weakening by controlling the d-axis current to reduce magnetic flux, thereby reducing back-EMF and allowing higher voltage application to achieve greater motor stroke
Solution Approach 2:
The patent implements dynamic flux weakening control that continuously adjusts the d-axis and q-axis current components based on real-time motor operation conditions. This dynamic control allows the system to adaptively manage voltage limits and back-EMF constraints, enabling extended stroke operation while maintaining proper motor control
2Length of moving object
If voltage limits are applied to control motor operation, then motor operation is constrained, but the desired stroke cannot be achieved due to back-EMF restrictions
Solution Approach 1:
By transforming the control approach from scalar voltage control to vector control with d-axis and q-axis components, the patent enables independent adjustment of flux and torque. This parameter decomposition provides flexibility to apply voltage limits while achieving desired stroke through coordinated control of current components
Solution Approach 2:
The patent segments the current control into two independent components: d-axis current for flux control and q-axis current for torque control. This segmentation allows separate management of voltage constraints and stroke requirements, enabling the system to operate within voltage limits while achieving the desired motor stroke
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 scheme enables the motor to draw sufficient voltage for optimal operation, minimizing q-axis voltage component signal adjustments based on remaining voltage, thereby achieving the specified stroke without running out of clearance.
Implementation Method 1
a driving coil that generates a force for moving the piston forward and backward within the housing
Implementation Method 2
Linear compressors in refrigerators face limitations in stroke due to back-EMF, which restricts the voltage that can be applied by the inverter
Data Source
AI summary
A method for controlling a linear compressor of an appliance includes receiving, via a controller of the linear compressor, a d-axis current error signal, a q-axis current error signal, and a DC current error signal. The method also includes determining, via the controller, a DC voltage component signal based on the DC current error signal. The DC voltage component signal is limited by a first voltage threshold. Further, the method includes then determining, via the controller, a d-axis voltage component signal based, at least in part, on the q-axis current error signal. The d-axis voltage component signal is limited by a second voltage threshold. Furthermore, the method includes then determining, via the controller, a q-axis voltage component signal based, at least in part, on the d-axis current error signal. The q-axis voltage component signal is limited by a third voltage threshold that is less than the second voltage threshold. In addition, the method includes controlling, via the controller, a motor of the linear compressor using a single-phase vector-like control scheme based, at least in part, on the DC voltage component signal, the d-axis voltage component signal and the q-axis voltage component signal.