Variable Flux Machine Torque Control During Shunt Angle Transients
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Solution Overview
Problem
Rotary electric machines, particularly variable flux machines (VFM) and permanent magnet (PM) machines, face challenges in maintaining accurate and smooth torque transient responses, leading to noise, vibration, and harshness (NVH) issues due to slow and large torque transients, especially during high-speed/low-load operations.
Innovation Solution
Implementing open-loop/feed-forward control strategies that calculate and apply d-axis and q-axis delta current terms to maintain output torque levels during shunt angle transitions, using lookup tables and proportional-integral blocks to adjust current terms, and incorporating thermal regulation for PM machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If field weakening techniques are used to reduce back-EMF at higher rotational speeds, then the machine can operate at higher speeds, but energy losses increase and output torque capability decreases
Solution Approach 1:
The patent changes the magnetic flux parameter dynamically by adjusting the shunt angle of flux-shunting elements. This allows the machine to maintain optimal flux levels across different operating conditions, avoiding the energy losses associated with traditional field weakening techniques while still enabling high-speed operation.
Solution Approach 2:
The patent implements dynamic control of magnetic flux by continuously adjusting the shunt angle during operation. This dynamic adjustment allows the system to adapt to changing load and speed conditions, maintaining efficiency across the operating range rather than using static field weakening.
2Adaptability or versatility
If shunt angle transitions are performed to change magnetic flux, then output torque can be maintained at different operating points, but torque transient response becomes slow and causes NVH effects
Solution Approach 1:
The patent applies feed-forward control that calculates and applies d-axis and q-axis delta current terms in advance during shunt angle transitions. This preliminary action compensates for the expected torque disturbance before it occurs, maintaining smooth torque output and preventing NVH effects.
Solution Approach 2:
The patent uses proportional-integral (PI) control blocks that continuously monitor actual torque output and adjust current commands in real-time. This feedback mechanism corrects any torque deviations caused by shunt angle transitions, ensuring rapid and accurate torque transient response.
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 optimizes the speed and accuracy of torque transient responses in VFM and PM machines, reducing NVH effects and maintaining output torque levels, while also adapting to thermal changes, thereby enhancing drive quality and efficiency.
Implementation Method 1
An energized PM machine generates a back-electromotive force (back-EMF) that opposes a voltage of the energized stator windings
Implementation Method 2
The rotating stator field interacts with the strong magnetic fields of the permanent magnets to impart rotational forces to the rotor shaft
Data Source
AI summary
A method for controlling transient operation of a variable flux machine (VFM) includes, during a shunt angle transition, receiving a commanded and measured shunt angle when operating in a predetermined operating region, e.g., maximum torque per ampere or field weakening. The method includes calculating d-axis and q-axis delta current terms (ΔId and ΔIq) required to maintain an output torque level of the VFM through a duration of the shunt angle transition, then applying the required ΔId and ΔId terms as feed-forward terms to adjust a d-axis current (Id) term and a q-axis current (Iq) term from a respective lookup table. In this manner the controller maintains the output torque level of the VFM during the shunt angle transition. An electric powertrain includes the VFM, a TPIM, and the controller. A PM machine may be controlled by substituting temperature for shunt angle.