PMSM Drive Current Limiting via Torque Command Modification
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Solution Overview
Problem
Existing PMSM control algorithms fail to effectively manage machine current and voltage limits, leading to potential excessive current or voltage issues that can impact system reliability and efficiency.
Innovation Solution
A system and method that perform maximum torque per ampere (MTPA) and maximum torque per voltage (MTPV) calculations to determine current commands, ensuring the PMSM operates within designated current and voltage limits, with online torque command modification to maintain optimal torque and current trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If existing PMSM control algorithms are used, then the motor can operate with high power density and easy controllability, but the machine current and voltage may exceed designated limits leading to system reliability issues
Solution Approach 1:
The control algorithm performs preliminary checks of current and voltage limits before generating torque commands. By calculating maximum available torque based on current voltage and current limits, and comparing it with the requested torque, the system proactively prevents excessive current or voltage conditions before they occur, rather than reacting after limits are exceeded
Solution Approach 2:
The algorithm continuously monitors the actual current and voltage states of the PMSM and uses this feedback to dynamically adjust the maximum available torque calculation. The current limit check and voltage limit check create closed-loop feedback mechanisms that ensure the motor operates within safe boundaries while maintaining optimal performance
2Productivity
If torque command is increased to improve productivity, then the motor output increases, but the machine current may exceed the maximum current limit
Solution Approach 1:
The algorithm dynamically changes the torque command parameter based on the calculated maximum available torque. When the requested torque exceeds the maximum available torque (determined by current limits), the algorithm modifies the torque command to match the maximum available torque, ensuring current limits are not exceeded while maximizing productive output within safe boundaries
3Power
If DC link voltage is increased to improve power output, then the motor can deliver higher power, but the PMSM voltage may exceed the maximum DC link voltage
Solution Approach 1:
The control algorithm performs a preliminary voltage limit check by calculating the maximum available torque based on the DC link voltage before executing torque commands. This preliminary action prevents voltage excursions by ensuring that torque commands are always within the voltage capability of the system
Solution Approach 2:
When the maximum available torque determined by voltage limits is less than the requested torque, the algorithm modifies the torque command parameter to match the voltage-constrained maximum. This dynamic parameter adjustment ensures the PMSM voltage remains within safe boundaries while maximizing power output under voltage constraints
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 protect against excessive machine current or voltage in a PMSM drive. Systems and methods employ a torque control algorithm for PMSMs that uses the constraints of both machine current and voltage capability in PMSM drives, and online torque command modification according to the maximum allowed torque under these machine current and voltage constraints.