Sensorless PM Motor Control via Open-Phase Voltage Detection
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Solution Overview
Problem
Existing sensor-less control systems for permanent magnet motors face challenges in maintaining high-performance control characteristics, especially in low velocity regions due to sensitivity decline and noise interference, leading to inaccurate position detection and deteriorated torque characteristics.
Innovation Solution
A synchronous motor drive system that employs a 120-degree energization method with a mode switching trigger generator, which selects two phases based on open phase induced voltage and adjusts switching timing according to generated torque, using a phase compensator to delay switching and improve power factor, thereby enhancing control stability and torque performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sensor-less control based on velocity induced voltage is used, then cost is reduced and system miniaturization is achieved, but position detection accuracy deteriorates in low velocity region
Solution Approach 1:
The patent changes the detection parameter from velocity-induced voltage (which depends on rotational speed) to open-phase induced voltage (which exists even at zero velocity). This parameter change enables accurate position detection across all velocity ranges, resolving the contradiction between cost reduction through sensor-less control and position detection accuracy in low velocity region.
2Measurement precision
If 120-degree energization with open phase induced voltage switching is used, then position detection accuracy is improved in low velocity region, but power factor deteriorates under large load torque
Solution Approach 1:
The patent introduces dynamic adjustment of energization phase switching timing based on the magnitude of q-axis magnetic flux. When q-axis magnetic flux exceeds a threshold (indicating large load torque or high inductance), the system delays the switching timing to compensate for phase advance, thereby improving power factor while maintaining accurate position detection capability.
3Force
If q-axis magnetic flux increases due to large load torque, then torque capability is improved, but phase advance occurs and power factor deteriorates
Solution Approach 1:
The patent implements a feedback mechanism that monitors the magnitude of q-axis magnetic flux (calculated from torque current and inductance parameters) and adjusts the energization phase switching timing accordingly. When q-axis magnetic flux is large, the system delays switching to compensate for phase advance, creating a closed-loop control that maintains optimal power factor across varying load conditions while preserving torque capability.
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 system achieves high-performance control characteristics in low velocity regions by improving power factor and torque stability, even under heavy loads or large inductance conditions, ensuring accurate position detection and efficient motor operation.
Implementation Method 1
detects an open phase induced voltage generated in a non-energization phase winding when positive or negative pulse voltages are applied to the two phases
Data Source
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AI summary
To provide a drive system of a PM motor that can realize a high-performance control characteristic in a low velocity region. The synchronous motor drive system includes: a power converter that generates an AC voltage by switching multiple switching elements sequentially and supplies it to a synchronous motor; a torque detection part for detecting or estimating a load torque of the synchronous motor; a detector for detecting a release voltage of a phase that is not supplied when pulse outputs of two phases that are energized by the power converter are supplied to two phases among three-phase winding of the synchronous motor; and a controller for switching the two phases that are energized according to the detected release voltage according in accordance with a predetermined energization mode, in which the controller delays timing of switching the two phases according to the detected or estimated load torque of the synchronous motor.