PMSM Drive Battery Current Limiting via MTPA and MTPV Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor control systems for PMSM drives, particularly in electric power steering systems, face challenges in effectively limiting battery current to prevent excessive discharging or charging, which can lead to battery degradation, and require offline calibration that is time-consuming and not optimal for dynamic operating conditions.
Innovation Solution
A motor control system that performs maximum torque per ampere (MTPA) and maximum torque per voltage (MTPV) calculations to determine current commands, iteratively adjusting torque commands to ensure battery current limits are met while maximizing voltage utilization, allowing for online battery current management across all operation regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If offline calibration is used to limit battery current, then battery protection is achieved, but the process is time-consuming and not optimal for dynamic operating conditions
Solution Approach 1:
The patent implements dynamic battery current limiting by continuously monitoring operating conditions (motor speed, torque demand, battery state) and adjusting current limits in real-time during motor operation, replacing static offline calibration with adaptive online control that responds to changing conditions
Solution Approach 2:
The control system performs self-adjustment by automatically modifying torque commands and current limits based on real-time feedback from sensors and operating conditions, eliminating the need for external calibration processes while maintaining optimal battery protection
2Reliability
If torque command is reduced to limit battery current, then battery current limit is met, but voltage utilization is not maximized
Solution Approach 1:
The patent dynamically adjusts multiple parameters including torque commands, current limits, and operating points based on real-time conditions, changing these parameters optimally to simultaneously satisfy battery current constraints and maximize voltage utilization efficiency
Solution Approach 2:
The control system continuously monitors both battery current and voltage utilization metrics, using feedback loops to adjust torque commands that achieve current limiting while maintaining optimal voltage usage, preventing both under-utilization and over-current conditions
3Power
If maximum torque is commanded to PMSM, then motor performance is optimized, but battery current exceeds safe limits
Solution Approach 1:
The control system preemptively limits torque commands before they can cause harmful excessive battery current, by calculating safe torque boundaries based on real-time battery current limits and operating conditions, preventing harmful effects before they occur
Solution Approach 2:
The patent applies partial torque limitation where the torque command is reduced only to the extent necessary to meet battery current constraints, rather than completely eliminating torque, thus maintaining adequate motor performance while preventing harmful over-current conditions
Data Source
AI summary
Technical solutions are described for controlling operation of an electric machine such as a permanent magnet synchronous motor (PMSM) drive or motor control system to limit battery current and protect a battery from excessive discharging or charging current from the PMSM drive. Systems and methods employ a torque control algorithm for PMSMs that uses a battery current limit constraint when generating current commands during each of a maximum torque per ampere (MTPA) operation, and maximum torque per voltage (MTPV) operation. Torque search operations are performed in each of the MTPA and MTPV operation regions in a PMSM drive system until current commands are achieved under a given battery current limit constraint and while maintaining maximum voltage utilization throughout all PMSM operation regions.