AC Machine Inverter Control Device DC Current Estimation
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Solution Overview
Problem
Conventional control devices for AC rotating electrical machines face increased processing load due to the need for correcting dead time periods when estimating phase voltages, which affects the precision of DC current calculation.
Innovation Solution
A control device that includes a midpoint potential detection unit and a phase current detection unit to calculate the DC current input to the inverter circuit, allowing for precise estimation of DC current without addressing dead time corrections, thereby reducing CPU processing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase voltages are estimated from phase voltage command value with dead time correction, then measurement precision is improved, but CPU processing load increases
Solution Approach 1:
The patent extracts only the necessary information (midpoint potential and phase current) from the complex voltage estimation process, eliminating the need for dead time correction calculations while maintaining sufficient measurement precision for DC current estimation
Solution Approach 2:
Instead of calculating phase voltages through complex command value processing with dead time correction, the patent uses direct midpoint potential detection as a simplified copy that provides sufficient information for DC current estimation without the computational burden
2Measurement precision
If dead time correction is applied to phase voltage estimation, then DC current calculation precision is improved, but computational complexity increases
Solution Approach 1:
The patent extracts the essential information needed for DC current calculation by directly detecting midpoint potentials and phase currents, removing the unnecessary dead time correction step while maintaining calculation precision
Solution Approach 2:
Instead of calculating phase voltages and then deriving DC current (the conventional approach requiring dead time correction), the patent inverts the approach by directly using midpoint potentials and phase currents to calculate DC current, simplifying the computational path
Data Source
AI summary
A control device of an AC rotating electrical machine includes: a midpoint potential detection unit 12 that detects, for respective phases, midpoint potentials 43, 44, 45 of upper switching elements 41 and lower switching elements 42 of an inverter circuit 20; a phase current detection unit 23 that detects a phase current of each phase of an AC rotating electrical machine 3; and a CPU 11 that calculates a current estimated value Idc of DC current that is input from a DC power supply 2 to the inverter circuit 20, on the basis of the detected midpoint potential of each phase and the phase current of each phase.