Sensorless Motor Control Using Dynamic PWM Switching
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Solution Overview
Problem
Existing position sensorless motor control systems using a single current sensor suffer from degraded control performance when the final voltage command vector falls in an unmeasurable area of the inverter's space vector, leading to incorrect injection of high-frequency voltage and suboptimal control.
Innovation Solution
A motor control system that includes a reference current generator, a motor voltage providing device, a high frequency voltage generator, and coordinate converters to generate and inject a high frequency voltage proportional to the reference current and feedback current, ensuring the phase voltage is correctly provided to the motor, thereby maintaining control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single current sensor is used to reduce cost, then manufacturing cost is reduced, but control performance is degraded when the voltage command vector is in an unmeasurable area
Solution Approach 1:
The system dynamically switches between different PWM switch patterns (first pattern for measurable areas, second pattern for unmeasurable areas) based on the position of the final voltage command vector in the space vector diagram. This dynamic adaptation ensures accurate high-frequency voltage injection and maintains control performance across all operating conditions while using only a single current sensor.
Solution Approach 2:
The system changes the PWM switching parameters (switch pattern) based on the operating condition (measurable vs. unmeasurable area). By detecting the position of the voltage command vector and adjusting the PWM pattern accordingly, the system maintains accurate current measurement and control performance throughout the entire operating range despite using a single current sensor.
2Measurement precision
If PWM switch pattern is changed to ensure constant DC-link current, then current measurement accuracy is improved, but high frequency voltage injection becomes incorrect in unmeasurable areas
Solution Approach 1:
The system dynamically selects between a first PWM switch pattern (for measurable areas where constant DC-link current is needed) and a second PWM switch pattern (for unmeasurable areas where different current measurement strategies are required). This dynamic switching ensures that the appropriate measurement and injection strategy is applied based on the operating condition, maintaining both measurement accuracy and injection accuracy across all conditions.
Solution Approach 2:
The system changes the PWM switching parameters based on the position of the voltage command vector in the space vector diagram. When the vector is in a measurable area, one set of parameters is used; when in an unmeasurable area, a different set of parameters is applied. This parameter adaptation resolves the conflict between maintaining constant DC-link current and achieving accurate high-frequency voltage injection.
3Adaptability or versatility
If high frequency voltage is injected for position estimation, then position sensorless control is achieved, but control stability is compromised when voltage command is in unmeasurable area
Solution Approach 1:
The system dynamically adapts the PWM switch pattern based on whether the voltage command vector falls in a measurable or unmeasurable area. This dynamic adaptation ensures that high-frequency voltage injection is performed correctly in all regions of the space vector diagram, maintaining both the position estimation capability and control stability under all operating conditions.
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 stable position sensorless control performance by ensuring the high frequency voltage is correctly injected, maintaining control performance and reducing costs by using a single current sensor.
Implementation Method 1
estimate position information of a motor from a high frequency current induced by injecting a high frequency voltage signal into the motor
Data Source
AI summary
A motor control system includes a reference current generator that generates a reference current based on a command, a motor voltage providing device that generates a phase voltage based on the reference current, a high frequency voltage, and a feedback current and provides a motor with the phase voltage, and a high frequency voltage generator that generates the high frequency voltage corresponding to a magnitude of voltage generated based on the reference current and the feedback current.