Power Conversion Device Step-Out Detection via Induced Voltage
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Solution Overview
Problem
Existing methods for detecting step-out in permanent magnet synchronous motors, such as those using magnetic pole position sensors or sensorless methods, face challenges like increased costs, incomplete detection of step-out states, and lack of protection against load variations, leading to potential motor damage and inefficiencies.
Innovation Solution
A power conversion device and control method that employs a frequency detection unit, speed reproducer, and step-out determination unit to detect step-out by analyzing induced voltages during a free run state, allowing for reliable detection without a magnetic pole position sensor, and includes a circuit breaker for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic pole position sensor is used for step-out detection, then detection reliability is improved, but device cost and complexity increase
Solution Approach 1:
The patent extracts the step-out detection function from the magnetic pole position sensor system and implements it through software algorithms using existing current detection circuits. The step-out determination unit independently calculates the angle difference between the actual rotor position and the commanded position, eliminating the need for additional sensors while maintaining detection reliability.
Solution Approach 2:
The patent creates a virtual model of the rotor position by calculating the angle from current detection signals and uses this copied position information for step-out detection. Instead of directly measuring position with sensors, the system copies position information from electrical signals and processes it to detect step-out conditions.
2Device complexity
If sensorless control is used to reduce cost, then device complexity is reduced, but step-out detection reliability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the actual rotor position is continuously calculated from current signals and compared with the commanded position. The angle difference feedback is used by the step-out determination unit to reliably detect step-out conditions, maintaining detection accuracy without requiring additional sensors.
Solution Approach 2:
The patent combines multiple existing functions (current detection, position calculation, and step-out determination) into an integrated control system. By compositing these functions using software algorithms and existing hardware resources, the system achieves reliable step-out detection without adding separate sensor components.
3Reliability
If conventional step-out detection methods are used, then detection capability is provided, but protection against motor damage is insufficient
Solution Approach 1:
The patent performs preliminary detection of step-out conditions by continuously monitoring the angle difference between actual and commanded rotor positions. The step-out determination unit proactively identifies step-out events before they cause significant motor damage, enabling timely protective action through the control unit to prevent harmful effects.
Solution Approach 2:
The patent converts the potentially harmful step-out condition into a detectable signal by monitoring angle differences. The harmful asynchrony between rotor and stator fields is transformed into useful information that triggers protective control actions, turning a dangerous condition into an opportunity for early intervention and motor protection.
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 highly reliable step-out detection and protection in permanent magnet synchronous motors, reducing costs and preventing motor damage by accurately identifying and responding to step-out conditions without the need for magnetic pole position sensors.
Implementation Method 1
a frequency detection unit, which detects a frequency of an induced voltage generated in a free run state
Implementation Method 2
circuit breaker for protection
Data Source
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AI summary
Provided is a power conversion device equipped with a power-swing detection function for a rotary machine with an embedded permanent magnet, and also provided is an apparatus (for example, a rotary machine driving apparatus or refrigeration apparatus) using the power conversion device. The power conversion device comprises the following: a frequency detection unit for generating a digital signal having information on the rotation speed, rotation direction, and magnetic pole position of the rotary machine, such digital signal generated on the basis of the induced voltage of the rotary machine when the rotary machine is in a free run state; a speed reproducer for estimating the rotation speed, rotation direction, and magnetic pole position of the rotary machine on the basis of the digital signal generated in the frequency detection unit; and a power-swing determination unit for determining the power swing state of the rotary machine on the basis of the rotation speed, rotation direction, and magnetic pole position estimated by the speed reproducer.