Overmodulation Voltage Command Signal Control for Electric Machines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-phase electric machine control systems face challenges in maintaining proper phase current regulation when operating in overmodulation regions, leading to current/torque oscillations due to discontinuities in voltage command signals and asymmetric duty cycles.
Innovation Solution
An overmodulation method that generates modified voltage command signals by computing a modified voltage angle without sector number computation, using an overmodulation processor with a voltage angle computation function, voltage angle modification unit, and modified voltage command generation module to ensure correct phase voltage application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If voltage command signals are applied to PWM module in overmodulation region, then torque output is improved, but phase current regulation deteriorates due to discontinuities and asymmetric duty cycles
Solution Approach 1:
The patent modifies the voltage command signals by applying a phase shift based on the sector number to compensate for discontinuities in the overmodulation region. This parameter change ensures continuous and accurate phase voltage application, maintaining both high torque output and proper current regulation.
Solution Approach 2:
The system uses feedback from the sector number computation and discontinuity detection to dynamically adjust the voltage command signals. This feedback mechanism ensures that the PWM module receives corrected signals that maintain current regulation accuracy while operating in the overmodulation region for high torque output.
2Power
If sector number computation is used for voltage command signal generation, then overmodulation control is achieved, but signal discontinuities and computational complexity increase
Solution Approach 1:
The patent computes the sector number in advance and uses it to pre-determine the appropriate phase shift for voltage command signals. This preliminary action allows the system to proactively compensate for upcoming discontinuities rather than reacting to them, reducing computational complexity during real-time PWM generation.
Solution Approach 2:
The sector number acts as an intermediary parameter that bridges the gap between the voltage command signals and the PWM generation process. By using the sector number to select appropriate signal correction strategies, the system simplifies the overall control logic while maintaining accurate overmodulation control.
3Device complexity
If modified voltage command signals are generated without sector number computation, then computational complexity is reduced, but voltage angle accuracy may deteriorate
Solution Approach 1:
The system uses the sector number to self-correct the voltage command signals by applying appropriate phase shifts. This self-service mechanism allows the control system to maintain accurate voltage angle information using simple computational operations, achieving both low complexity and high precision.
Solution Approach 2:
Instead of performing complete and complex voltage angle calculations, the system applies partial corrections based on sector number to achieve sufficient accuracy for overmodulation control. This partial action approach reduces computational burden while maintaining the precision needed for accurate torque control.
Data Source
AI summary
Embodiments of the present disclosure relate to methods, systems and apparatus for controlling operation of an electric machine in a vector controlled motor drive system when the electric machine operates in an overmodulation region. The disclosed embodiments can reduce variations/errors in the phase voltage command signals applied to the multi-phase machine so that phase current may be properly regulated thus reducing current/torque oscillation, which can in turn improve machine efficiency and performance, as well as utilization of the DC voltage source.