Electric Motor Driving Apparatus Phase Control
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Solution Overview
Problem
Conventional electric motor driving systems using two inverters struggle with maintaining high accuracy and stability in controlling the phase difference between voltage command vectors, leading to inefficiencies and potential system output cancellation when the phase difference is not precisely 180°, especially due to timing differences in sensor sampling and control timing.
Innovation Solution
The system employs a control unit that calculates a composite voltage command by determining the phase and amplitude of a composite voltage vector based on the first and second voltage vectors, allowing for flexible operation between reverse and non-reverse modes, thereby managing the system output effectively regardless of phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the phase difference between voltage command vectors is controlled to be 180° for high output, then the system output is maximized, but the control stability deteriorates due to timing differences in sensor sampling and control timing
Solution Approach 1:
The invention changes the control parameter from a fixed 180° phase difference to a variable phase difference that can be adjusted based on control conditions. The control unit calculates the composite voltage command based on the actual phase difference between the first and second voltage vectors, allowing the phase difference to vary within a range that includes but is not limited to 180°, thereby optimizing both output and stability
Solution Approach 2:
The invention makes the phase difference dynamic rather than static. By continuously calculating the composite voltage command based on the actual phase difference between voltage vectors from two inverters, the system adapts the phase relationship in real-time according to operating conditions, sensor sampling timing, and control timing, transforming a rigid 180° requirement into a flexible control parameter
2Adaptability or versatility
If the phase difference between voltage command vectors deviates from 180° due to timing differences, then the control flexibility is improved, but the system output decreases due to potential output cancellation
Solution Approach 1:
The invention introduces feedback by continuously monitoring the actual phase difference between the first and second voltage vectors and using this information to calculate the composite voltage command. The control unit adjusts the voltage commands based on the measured phase difference, creating a closed-loop control system that compensates for timing deviations and maintains optimal output
Solution Approach 2:
The invention performs preliminary calculation of the composite voltage command based on the actual phase difference before applying the voltage commands to the inverters. By pre-calculating the optimal voltage commands that account for the measured phase difference, the system proactively compensates for potential output cancellation rather than reacting to it after it occurs
Data Source
AI summary
An electric motor driving apparatus controls driving of an electric motor having two or more phase windings whose ends are open by using first and second inverters. A control unit includes a first inverter control circuit and a second inverter control circuit. The first inverter control circuit generates a first voltage command as an output voltage command to the first inverter based on a torque command. The second inverter control circuit generates a second voltage command as an output voltage command to the second inverter. The control unit determines a composite voltage command based on a first voltage command vector and a second voltage command including a case, in which a pure phase difference between the first voltage command vector on a dq coordinate corresponding to the first voltage command and the second voltage command vector on the dq coordinate corresponding to the second voltage command is other than 180°.