Phase Current Determination in Electric Machine Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Determining phase currents in electric machines with power converters during active rectification is complex due to noise, sensor offsets, and the need for synchronization with switching sequences, especially when not all low-side switches are closed.
Innovation Solution
Measuring all low-side-branch currents simultaneously and correlating them to calculate phase currents, using the two currents with the greatest amplitude, eliminating the need for synchronization and allowing measurements at any time, independent of switching times, and using parallel or serial A/D conversions for quick data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-side-branch currents are measured using shunts in the low-side branch of the power converter, then phase currents can be determined, but measurement errors occur due to noise, sensor offsets, and incorrect measurements when switches are open
Solution Approach 1:
The patent segments the measurement process by evaluating multiple individual phase current measurements and selecting only those that meet validity criteria (non-zero magnitude, consistent with switching state). This segmentation allows the system to isolate and use only reliable measurements while discarding erroneous ones, thereby improving both measurement precision and reliability simultaneously.
2Measurement precision
If current measurements are synchronized with the control application and switching sequence, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The system performs self-validation by automatically evaluating whether each measured current value is consistent with the current switching state and has non-zero magnitude. This self-service mechanism eliminates the need for external synchronization control, reducing device complexity while maintaining measurement precision through intelligent data filtering.
3Measurement precision
If all low-side switches are closed for current measurement, then all phase currents can be measured, but this conflicts with the active rectification operation where switches are switched
Solution Approach 1:
The patent implements a dynamic measurement strategy where the system adapts to the current operational state by evaluating measurement validity based on the actual switching configuration. Instead of requiring a fixed switch position, the system dynamically identifies valid measurements from available data, enabling compatibility with active rectification operation while maintaining complete phase current measurement capability.
Data Source
AI summary
A method for determining the phase currents of an electric machine having a power converter, and a stator, the power converter having, for each phase, an upper branch having an upper switch and a lower branch having a lower switch, all the upper branches being connected to an upper DC voltage terminal and all the lower branches to a lower DC voltage terminal. The power converter is operated in an active rectification mode in which each upper switch is closed only as long as a phase voltage at the relevant upper switch is higher than a voltage at the upper DC voltage terminal, and each lower switch being closed only as long as a phase voltage at the relevant lower switch is lower than a voltage at the lower DC voltage terminal; phase branch currents being measured in all the lower branches.