Sensorless Rotor Position Estimation Using Open-Phase Induced Voltage
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Solution Overview
Problem
Conventional sensorless control methods for permanent magnet electrical motors face challenges in accurately estimating the initial rotor position, especially at low speeds or when the motor is stopped, leading to potential start-up failures and negative rotation due to low sensitivity of open-phase induced voltage methods.
Innovation Solution
A drive system that includes a voltage detection unit for induced voltages at open phases, an induced voltage difference calculating unit, an induced voltage sum calculating unit, and a rotor position determining unit, which uses the differences and sums of induced voltages to precisely estimate the rotor position and prevent negative rotation during start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless control based on speed electromotive voltage is used, then cost and system size are reduced, but position detection accuracy deteriorates at low speeds and stopped state
Solution Approach 1:
The patent changes the detection parameter from speed electromotive voltage (which is proportional to rotation speed) to open-phase induced voltage (which is generated by magnetic circuit changes). This parameter change enables accurate position detection at low speeds and stopped state where speed electromotive voltage is insufficient, while maintaining the sensorless control architecture.
2Reliability
If open phase induced voltage method is used for initial position estimation, then start-up can be achieved, but sensitivity decreases leading to negative rotation
Solution Approach 1:
The patent merges the detection of open-phase induced voltage with the existing 120-degree current application control system. By integrating the open-phase voltage detection into the standard control architecture, the system achieves accurate initial position estimation without requiring additional sensors or complex external measurement equipment, thereby preventing negative rotation while maintaining start-up capability.
3Loss of time
If six voltage pulses are applied for initial position estimation, then initial position can be estimated quickly, but system complexity increases
Solution Approach 1:
The patent implements self-service by utilizing the motor's own open-phase induced voltage for position detection. The system uses the motor's inherent electromagnetic characteristics and existing control circuitry to perform initial position estimation, eliminating the need for external position sensors or complex additional measurement systems, thereby achieving quick estimation without increasing overall system complexity.
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 accurate and rapid initial position estimation of the rotor, preventing start-up failures and ensuring positive rotation, even at low speeds, by enhancing the detection sensitivity and precision of the rotor position.
Implementation Method 1
a voltage detection unit for induced voltages at open phases upon application of positive and negative pulse voltages between two phases
Data Source
Figure 1
Figure 2A~2B
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AI summary
A drive system of a synchronous electrical motor according to the present invention is a drive system of a synchronous electrical motor (100) including: a synchronous electrical motor (4); a power converter (3) that is connected to the synchronous electrical motor (4) and that is constituted of a plurality of switching elements; a controller (2) that controls the synchronous electrical motor (4) by outputting a voltage instruction to the power converter (3); a voltage detection unit (21) that detects induced voltages at respective open phases upon application of respective positive and negative pulse voltages between respective two phases out of three-phase windings of the synchronous electrical motor (4); an induced voltage difference calculating unit (22) that calculates an induced voltage difference that is a difference between an induced voltage detected by the voltage detection unit (21) at each of the open phases upon application of the positive voltage pulse between the corresponding two phases and an induced voltage detected by the voltage detection unit at the open phase upon application of the negative voltage pulse between the two phases; an induced voltage sum calculating unit (23) that calculates an induced voltage sum that is a sum of the induced voltage detected by the voltage detection unit (21) at each of the open phases upon application of the positive voltage pulse between the corresponding two phases and the induced voltage detected by the voltage detection unit (21) at the open phase upon application of the negative voltage pulse between the two phases; and a rotor position determining unit (20) that determines a rotor position based on the induced voltage difference and the induced voltage sum.