Sensorless Inverter Control for Synchronous Motor Restart
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Solution Overview
Problem
Existing rotation sensor-less control devices for synchronous motors face challenges in restarting from a free-running condition across all speed regions, particularly when the no-load induced voltage exceeds the DC side voltage, leading to potential over-voltage issues and prolonged restart times.
Innovation Solution
A rotation sensor-less control device that infers the phase angle and angular velocity using both inductance and induced voltage, and employs PWM with only non-zero voltage vectors to generate a voltage instruction, ensuring accurate phase estimation and stable startup across all speed regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple restart techniques are employed to achieve restarting across all speed regions, then the restart capability is improved, but the restart time becomes very long and the control sequence becomes complicated
Solution Approach 1:
The patent applies a single control technique that functions across all speed regions including high-voltage regions. The controller is designed to handle free-running restart universally without requiring multiple specialized techniques, thereby achieving adaptability while maintaining simple and fast operation.
Solution Approach 2:
Instead of attempting to restart by multiple techniques in sequence (which would be time-consuming), the patent inverts the approach by using a single technique from the beginning that is capable of handling all regions. This eliminates the sequential trial process and achieves restart quickly without complicated sequences.
2Adaptability or versatility
If the load contactor is opened to enable free-running in the high-voltage region, then free-running capability is improved, but the risk of over-voltage on the DC side increases
Solution Approach 1:
The controller applies preliminary anti-action by detecting the high-voltage region condition and proactively suppressing the no-load induced voltage before over-voltage can occur. The control actively counteracts the harmful effect by generating appropriate voltage commands to prevent the DC side voltage from exceeding safe levels.
Solution Approach 2:
The patent employs feedback control where the controller continuously monitors the motor state and adjusts the voltage commands accordingly. By detecting the high-voltage region condition and the no-load induced voltage, the controller provides feedback to suppress the induced voltage and prevent over-voltage, thereby maintaining safe operation.
3Reliability
If the no-load induced voltage is suppressed to prevent over-voltage, then the safety is improved, but the restart performance may be degraded
Solution Approach 1:
The controller dynamically adjusts its behavior based on the operating region. In high-voltage regions, it suppresses no-load induced voltage to prevent over-voltage, while in other regions it maintains normal restart performance. This dynamic adaptation ensures both safety and productivity are optimized for each specific condition.
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
Enables efficient and stable restarts from free-running conditions in all regions, including high-voltage regions, by accurately estimating phase and angular velocity, preventing over-voltage, and reducing restart time.
Implementation Method 1
a phase angle/angular velocity inference section that infers the phase angle and angular velocity of a rotor, using both the inductance and induced voltage of said synchronous machine
Implementation Method 2
a control section that generates a voltage instruction value and controls the output current of aforementioned inverter using PWM in which only a non-zero voltage vector is selected
Data Source
Figure 1
Figure 2
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AI summary
In a rotation sensor-less control device that controls an inverter (1) that drives a synchronous machine (2), a rotation sensor-less control device according to one embodiment comprises: a phase angle/angular velocity inference section (5,6) that infers the phase angle and angular velocity of a rotor, using both the inductance and induced voltage of said synchronous machine; and a control section (24, 26) that, on startup from free running of the aforementioned inverter (1) and motor (2), generates a voltage instruction value and controls the output current of the aforementioned inverter (1) using PWM in which only a non-zero voltage vector is selected, wherein the aforementioned phase angle/angular velocity inference section (5, 6) infers the aforementioned rotational phase angle/angular velocity using the aforementioned voltage instruction value and inverter output current.