Electric Machine PWM Control for Harmonic Injection Timing
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Solution Overview
Problem
Existing methods for operating electric machines struggle to efficiently regulate harmonic currents and voltages, particularly in reducing noise and torque ripples, due to limitations in pulse width modulation techniques.
Innovation Solution
The method employs a 'double update' pulse width modulation approach, calculating two harmonic manipulated variables for each period of the modulation method, one for switch-on and one for switch-off operations, to independently determine these times and improve harmonic frequency modulation and voltage positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional single update pulse width modulation method is used, then the control structure is simple, but the delay is high and the maximum frequency of target voltages is limited
Solution Approach 1:
The patent divides the single update PWM control into two separate update operations: one for switch-on and one for switch-off. This segmentation allows each operation to be optimized independently, doubling the maximum frequency of target voltages while maintaining manageable control structure through systematic organization of the two update processes.
2Manufacturing precision
If harmonic currents are injected to reduce noise and torque ripples, then the regulation quality improves, but the complexity of control increases
Solution Approach 1:
The patent implements dynamic harmonic injection where the harmonic manipulated variable is continuously adjusted based on actual machine operation. The double update PWM method enables real-time modification of harmonic parameters, allowing the system to adapt to changing conditions and maintain optimal regulation quality without excessive complexity through dynamic rather than static control.
3Measurement precision
If the switching frequency is increased to improve voltage positioning, then the resolution improves, but the computational load increases
Solution Approach 1:
The patent performs preliminary calculation of the harmonic manipulated variable for both switch-on and switch-off operations before the actual PWM execution. By pre-calculating these values and storing them for use in the double update process, the system achieves high voltage positioning resolution without excessive computational load during the critical PWM switching moments, as the heavy calculation work is done in advance.
Data Source
AI summary
The invention relates to a method for operating an electric machine. A harmonic manipulated variable with respect to a harmonic of a predetermined frequency occurring during the energization of the electric machine is determined. The electric machine is energized using the determined harmonic manipulated variable by means of a pulse width modulation method. For each period of the pulse width modulation method, the harmonic manipulated variable is determined for both a switch-on operation and a switch-off operation.