Sensorless Synchronous Motor Control via Fourier Analysis
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Solution Overview
Problem
Existing sensorless control methods for synchronous motors face challenges such as increased losses and noise due to high-frequency currents, requiring complex adjustments and accurate current sampling, which complicates stable rotation phase angle estimation without a rotational phase angle sensor.
Innovation Solution
A sensorless control apparatus that calculates high-frequency voltage and current components using Fourier series expansion, allowing for accurate estimation of the rotation phase angle without the need for current synchronization with switching, thereby reducing noise and simplifying sampling management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector is used to detect the angle of rotation, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical detector system with an electrical calculation-based sensorless control system. The angle of rotation is estimated by calculating the phase angle from voltage and current signals processed through Fourier series expansion, eliminating the need for physical detectors and reducing system complexity while maintaining measurement precision
Solution Approach 2:
The patent creates a virtual model of the motor's electrical characteristics to estimate the angle of rotation. By modeling the relationship between voltage, current, and phase angle through mathematical calculations, the system replicates the function of a physical detector without its associated complexity and cost
2Measurement precision
If high-frequency voltage is superimposed to estimate angle of rotation, then measurement precision is improved, but loss and noise increase
Solution Approach 1:
The patent uses partial action by injecting only the minimum necessary high-frequency voltage component required for accurate angle estimation. The system carefully controls the amplitude and frequency of the superimposed voltage to achieve sufficient signal strength for measurement while minimizing energy loss and avoiding excessive noise generation
Solution Approach 2:
The patent dynamically adjusts parameters such as the amplitude, frequency, and injection timing of the superimposed high-frequency voltage based on operating conditions. By optimizing these parameters, the system achieves accurate angle estimation while minimizing energy loss and noise across different motor operating states
3Measurement precision
If current sampling is performed close to switching to observe high-frequency current, then measurement precision is improved, but device complexity and noise increase
Solution Approach 1:
The patent performs preliminary action by pre-calculating the expected high-frequency current characteristics based on the known switching pattern and motor parameters. This allows the system to prepare appropriate filtering and processing routines in advance, simplifying the actual sampling process and reducing complexity while maintaining measurement precision
Solution Approach 2:
The patent introduces an intermediary processing stage that uses Fourier series expansion to extract high-frequency current components from the total current signal. This intermediary mathematical transformation separates the useful high-frequency information from switching noise and other disturbances, simplifying the sampling management while improving measurement accuracy
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 rotation phase angle estimation without a rotational phase angle sensor, leading to size reduction, cost savings, and simplified maintenance, while minimizing high-frequency voltage superposition and facilitating current detection sampling.
Implementation Method 1
A sensorless control apparatus that calculates high-frequency voltage and current components using Fourier series expansion, allowing for accurate estimation of the rotation phase angle
Data Source
AI summary
According to one embodiment, a sensorless control apparatus for a synchronous motor, includes a PWM processing unit which pulse-width-modulates a three-phase voltage command, and thereby generates a gate command for an inverter, a high-frequency voltage calculator which obtains a high-frequency voltage component included in an output of the PWM processing unit or an equivalent output value, a high-frequency current calculator which obtains a high-frequency current component included in a current response value from a synchronous motor driven by the inverter, and an estimated angle calculator which calculates an estimated phase angle indicative of an estimated value of an angle of rotation of the synchronous motor, based on a plurality of pairs each including the high-frequency voltage component and the high-frequency current component which respectively include cosine components or sine components at an equal frequency, the pairs obtained for at least two different frequencies.