Inverter Control Device for Accurate SynRM Phase Angle Estimation
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Solution Overview
Problem
Existing inverter control systems for motor drive systems, particularly in applications like railroads and industrial settings, face challenges in accurately estimating the rotational phase angle of Synchronous Reluctance Motors (SynRM) at high-speed rotations, as existing methods rely on small no-load induced voltages and are not effective due to high-frequency voltage superposition premises.
Innovation Solution
The inverter control device employs a startup controller and a regular time controller that utilize high-frequency voltage commands and current responses to estimate the rotational phase angle in a stationary reference frame, transitioning to a rotating reference frame with initial values, allowing for accurate estimation and stable motor start-ups even at high speeds by counting zero-crossings of the rotational phase angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency voltage superposition method is used to estimate rotational phase angle, then low-speed rotation estimation accuracy is improved, but high-speed rotation estimation becomes difficult
Solution Approach 1:
The patent dynamically adapts the control strategy based on motor speed. At low speeds, high-frequency voltage superposition is used for accurate phase angle estimation. At high speeds, the system transitions to using back-EMF-based estimation without high-frequency superposition, allowing the system to maintain accuracy across the full speed range rather than being limited to low-speed operation only
Solution Approach 2:
The patent changes the estimation parameters based on operating conditions. The rotational phase angle estimation method is switched between two different approaches (high-frequency superposition method for low speed, back-EMF method for high speed) depending on the motor speed, enabling accurate measurement across varying speed conditions
2Extent of automation
If no-load induced voltage method is used for rotational phase angle estimation, then sensorless control is achieved, but estimation accuracy deteriorates at high speeds
Solution Approach 1:
The patent changes the estimation approach based on speed parameters. At low speeds, it uses high-frequency voltage superposition with no-load induced voltage for accurate sensorless control. At high speeds, it transitions to using back-EMF-based estimation without high-frequency superposition, maintaining both sensorless operation and accuracy across the full speed range
Solution Approach 2:
The system dynamically switches between different sensorless control strategies based on operating speed. The controller adapts the estimation method in real-time, using high-frequency superposition at low speeds and back-EMF-based estimation at high speeds, enabling accurate sensorless control throughout the entire operational range
3Device complexity
If single formula estimation without speed consideration is used, then free-run restart control is simplified, but high-speed rotation estimation accuracy is lost
Solution Approach 1:
The patent implements dynamic adaptation of the control algorithm based on motor speed. Instead of using a single fixed formula, the system switches between different estimation methods (high-frequency superposition at low speeds, back-EMF-based at high speeds), maintaining both operational simplicity and high-speed accuracy through speed-dependent strategy selection
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
This approach enables accurate estimation of rotational speed and phase angle, ensuring stable motor start-ups and operation across varying speeds, including high-speed rotations, without requiring high-speed calculation processes, thus improving reliability and efficiency.
Implementation Method 1
a current detector configured to detect a current of an output line of the inverter main circuit
Implementation Method 2
a rotational speed estimator configured to calculate a value corresponding to a rotational speed of the motor by using the value corresponding to the rotational phase angle
Data Source
AI summary
A device according to an embodiment includes an inverter main circuit; a detector configured to detect a current of an output line of the inverter main circuit; a starting time controller comprising a rotational phase angle estimator configured to calculate, based on a current response value detected by the detector, a value corresponding to a rotational phase angle of a motor connected to the inverter main circuit in a stationary reference frame, and a rotational speed estimator configured to calculate a value corresponding to a rotational speed of the motor by using the value corresponding to the rotational phase angle when the inverter main circuit is started; and a regular time controller configured to calculate, with the value corresponding to the rotational speed as an initial value, an estimated rotational phase angle of the motor in a rotating reference frame.