AC Machine Terminal Voltage Estimation for IPM Control
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Solution Overview
Problem
High terminal voltages in Interior Permanent Magnet (IPM) machines can lead to current regulation collapse, harmonic introduction, torque ripple, rotor and stator winding heating, and acoustic noise due to manufacturing and material variances, temperature changes, and inverter accuracy issues.
Innovation Solution
A processor-based system estimates actual inverter terminal voltage by determining instantaneous voltages, filtering, and adjusting d/q-axis current commands to maintain terminal voltage feedback within a threshold, using a field programmable gate array (FPGA) for controlling AC machines like IPM motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the controller uses d/q-axis voltage commands to control the IPM machine, then the machine can operate with high efficiency and wide constant power range, but the terminal voltage may exceed threshold due to manufacturing tolerances and temperature variations causing current regulation collapse and torque ripple
Solution Approach 1:
The patent implements a feedback mechanism by estimating the actual terminal voltage of the IPM machine and comparing it with a threshold value. When the estimated terminal voltage exceeds the threshold, the controller adjusts the d/q-axis voltage commands to bring the terminal voltage back within acceptable limits, preventing current regulation collapse and torque ripple while maintaining high drive efficiency
Solution Approach 2:
The patent dynamically changes control parameters (d/q-axis voltage commands) based on the estimated terminal voltage. By monitoring terminal voltage and adjusting the voltage commands in real-time, the system adapts to manufacturing tolerances and temperature variations, ensuring stable current regulation without sacrificing productivity
2Adaptability or versatility
If the controller increases voltage commands to expand operating range, then constant power range is widened, but harmonic distortion and torque ripple increase due to terminal voltage exceeding threshold
Solution Approach 1:
The controller continuously estimates terminal voltage and uses this feedback to modulate voltage commands. This feedback loop allows the system to expand its constant power operating range while preventing terminal voltage from exceeding the threshold, thereby avoiding harmonic distortion and torque ripple even at extended operating conditions
Solution Approach 2:
The patent employs dynamic adjustment of voltage commands based on real-time terminal voltage estimation. The controller dynamically modifies the d/q-axis voltage commands to maintain terminal voltage within acceptable limits across a wider operating range, eliminating static limitations while preventing harmful harmonics and torque ripple
3Manufacturing precision
If the controller uses estimated terminal voltage for control, then current regulation quality improves, but system complexity increases due to additional voltage estimation and filtering processing
Solution Approach 1:
The patent replaces complex physical voltage sensing hardware with a computational voltage estimation approach. By using mathematical models and signal processing to estimate terminal voltage from existing measurements, the system achieves high current regulation quality without adding complex physical sensing infrastructure
Solution Approach 2:
The patent creates a virtual model of the terminal voltage through estimation algorithms rather than directly measuring it with additional sensors. This computational copy of the voltage signal provides sufficient accuracy for high-quality current regulation while avoiding the complexity of additional hardware
Data Source
AI summary
In one example embodiment, a device for controlling an alternating current (AC) machine is disclosed. The device includes a processor configured to determine a plurality of instantaneous voltages corresponding to a plurality of phase voltages of an inverter, the inverter driving the AC machine. The processor is further configured to determine an actual line-to-line voltage of the inverter based on the plurality of instantaneous voltages. The processor is further configured to determine a terminal voltage feedback for controlling the AC machine, based on the determined actual line-to-line voltage and a terminal voltage threshold.