Voltage Injection Amplitude Adjustment for Rotor Position
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Solution Overview
Problem
Existing methods for determining the rotor position of a rotating, multi-phase electrical machine without a position sensor, particularly during rapid speed changes, face challenges in maintaining a sufficient signal-to-noise ratio and reducing noise development due to delays in filter time constants.
Innovation Solution
A method that adjusts the amplitude of voltage injection based on the current vector difference between predicted and actual rotor positions, using a PWM-controlled inverter, where the amplitude is increased with larger deviations to maintain signal quality and reduced with smaller deviations to minimize noise, and optionally high-pass filtering or taking the absolute value of the difference to account for model errors and speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the filter time constant is reduced to follow rapid speed changes, then the rotor position determination responds faster, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies dynamics by making the filter time constant variable rather than fixed. The filter time constant is adapted dynamically based on the absolute value of the current vector difference: when the current vector difference is large (indicating rapid speed changes), the filter time constant is reduced for faster response; when the current vector difference is small (indicating steady state), the filter time constant is increased for better noise filtering. This dynamic adaptation resolves the contradiction between fast response and good signal-to-noise ratio.
2Measurement precision
If the amplitude of voltage injection is increased to improve signal-to-noise ratio, then the rotor position determination becomes more accurate, but the noise development increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the amplitude of the high-frequency voltage injection based on the current vector difference. When the current vector difference is large (indicating rapid speed changes or large position deviations), the voltage injection amplitude is increased to ensure sufficient signal strength and accurate rotor position determination. When the current vector difference is small (indicating steady state with small deviations), the voltage injection amplitude is reduced to minimize noise development. This parameter adaptation resolves the contradiction between measurement accuracy and noise generation.
3Measurement precision
If the amplitude of voltage injection is constantly high to maintain good signal-to-noise ratio, then the rotor position is always determined accurately, but the noise development remains continuously high
Solution Approach 1:
The patent applies periodic action through continuous monitoring and periodic adjustment of the voltage injection amplitude based on the current vector difference. The system continuously evaluates the current vector difference and periodically adapts the injection amplitude accordingly, rather than maintaining a constant high amplitude. This periodic adaptation ensures that high injection amplitude is applied only when necessary (during rapid speed changes or large position deviations) and reduced during steady-state operation, thereby resolving the contradiction between maintaining continuous measurement accuracy and reducing continuous noise development and energy loss.
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 effectively maintains a good signal-to-noise ratio during dynamic conditions, allowing precise rotor position determination while minimizing noise and adapting to the machine's dynamics within a few sampling steps, suitable for highly dynamic systems.
Implementation Method 1
so-called anisotropy-based methods can be used here, which determine the rotor position via the magnetic anisotropy of the rotor
Implementation Method 2
fed by means of a PWM-controlled inverter
Data Source
Figure 1
AI summary
The invention relates to a method for adjusting an amplitude of a voltage injection of a rotating, multi-phase electric machine, which electric machine is fed by means of a PWM-controlled inverter, comprising at least the following steps: a. determining a predetermined current vector at a first time, which current vector would be present at the machine at a second time, by means of a voltage equation of the electric machine, in accordance with a voltage predetermined in a controller for controlling the electric machine, with a current vector determined from phase currents measured at the first time, and with a rotational speed of the machine, wherein the first time lies before the second time, b. determining a real current vector present at the machine at the second time in accordance with phase currents of the machine measured at the second time, c. forming a current vector difference between the predetermined current vector and the real current vector at the second time, d. adjusting the amplitude of the voltage injection in accordance with the formed current vector difference.