PMSM Torque Control via Speed Voltage Ratio
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Solution Overview
Problem
Permanent magnet synchronous motors (PMSMs) in electric vehicles face limitations in delivering bursts of torque exceeding maximum winding current, leading to potential damage and inefficiency due to excessive sparking and magnetic core saturation, especially when operating in regions where torque requests exceed the motor's capability.
Innovation Solution
A controller-based method that adjusts torque commands for PMSMs using a voltage bus, maintaining a constant ratio of speed to voltage, ensuring unaltered current magnitude and phase through the windings, thereby improving torque utilization and reducing the risk of damage by clipping torque requests to the motor's capability threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the PMSM is operated to deliver torque exceeding maximum winding current, then torque output is increased, but magnetic core saturation occurs and excessive sparking damages the motor
Solution Approach 1:
The controller preemptively determines the maximum torque capability threshold based on motor parameters, voltage, and speed before torque requests are executed. By establishing this threshold in advance and comparing incoming torque requests against it, the system prevents excessive current and sparking before they can cause damage, rather than reacting after damage occurs.
Solution Approach 2:
The system continuously monitors motor operating conditions (voltage, speed) and dynamically adjusts the maximum torque capability threshold accordingly. This feedback mechanism ensures the torque output remains within safe operating limits while maximizing performance, automatically adapting to changing conditions without manual intervention.
2Reliability
If the controller clips torque requests to the maximum torque capability threshold, then motor reliability is improved, but torque utilization efficiency deteriorates when torque requests exceed the threshold
Solution Approach 1:
Rather than using a fixed torque clipping threshold, the system dynamically calculates the maximum torque capability threshold based on real-time voltage and speed conditions. This allows the torque limit to adapt continuously, maximizing torque utilization within safe operating boundaries and reducing unnecessary clipping when the motor is operating below its capability.
3Device complexity
If the inverter supplies discrete voltage levels to the PMSM, then the motor structure is simplified, but the torque control precision deteriorates
Solution Approach 1:
The system optimizes torque control by dynamically adjusting operating parameters (voltage, speed, torque threshold) rather than requiring additional hardware complexity. By changing control parameters based on real-time conditions and using optimized switching strategies, the system achieves precise torque control within the constraints of discrete voltage levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows PMSMs to deliver torque closer to the requested value, enhancing torque capability utilization and preventing motor damage by maintaining a constant torque output based on the speed and voltage ratio, thus improving the motor's performance and reliability.
Implementation Method 1
The shaft torque of the motor and the power conversion efficiency depend upon both the magnitude and the phase angle of the oscillating voltage
Implementation Method 2
inverters are utilized to convert the non-oscillating voltage into three oscillating voltages
Implementation Method 3
The shaft torque of the motor and the power conversion efficiency depend upon both the magnitude and the phase angle of the oscillating voltage
Data Source
AI summary
A vehicle comprises an electric machine configured with at least one controller issuing torque commands with the use of a voltage bus. The controller may be configured to respond to a torque requests based on multiple vehicle system inputs including vehicle speed, position of the accelerator pedal and brake pedal, and various other vehicle data. The controller may respond to a torque request that exceeds a threshold value by issuing torque commands for the electric machine based on a speed of the electric machine and a voltage on the bus. Based on the speed of the electric machine and voltage on the bus, the controller may issue a constant torque output by the electric machine as the speed and voltage vary. Calculating a ratio using speed of the electric machine to voltage on the bus to determine torque capability may result as a constant torque when the ratio is constant.