MTPA Control Search Zone for Motor Current Amplitude Reduction
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Solution Overview
Problem
Existing MTPA control methods generate offline curves with inaccuracies, leading to suboptimal selection of Q-axis and D-axis currents, which decreases motor efficiency.
Innovation Solution
The method generates a search zone for the MTPA curve with upper and lower D-axis reference currents, iteratively modifying the D-axis reference current and corresponding Q-axis reference current to achieve the lowest current amplitude, thereby updating the current pairs for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline MTPA curves are generated using conventional autotune tests, then the control method is simple to implement, but the accuracy of the MTPA curve is insufficient leading to suboptimal current selection
Solution Approach 1:
The patent performs preliminary actions by generating an initial offline MTPA curve through autotune tests before actual operation, then iteratively refines this curve during motor operation. The controller pre-calculates search zones and iteratively modifies current references based on the initial curve, progressively improving accuracy without requiring complete recalculation from scratch during operation.
Solution Approach 2:
The patent implements feedback by using the initial offline MTPA curve to guide iterative modifications during operation. The controller continuously compares actual motor performance against the stored curve, modifies D-axis and Q-axis reference currents based on discrepancies, and updates the curve progressively. This closed-loop feedback mechanism improves accuracy while maintaining manageable complexity through controlled iteration.
2Loss of energy
If the MTPA curve is updated with iteratively modified current references, then motor efficiency is improved, but the control computation increases
Solution Approach 1:
The patent applies partial action by performing iterative modifications only within specifically defined search zones around the initial MTPA curve, rather than searching the entire current space. The controller modifies D-axis reference current by limited increments and adjusts Q-axis current correspondingly, achieving efficiency improvement through targeted partial updates rather than complete recalculation, thus reducing computation time.
Solution Approach 2:
The patent changes parameters by iteratively modifying the D-axis reference current in controlled increments and adjusting the Q-axis reference current to maintain torque output. This systematic parameter variation within defined bounds allows the controller to find optimized current pairs that improve motor efficiency while keeping computation manageable through constrained search space and incremental adjustments.
3Manufacturing precision
If search zones are generated with upper and lower D-axis reference currents, then the optimization range is defined, but the control algorithm complexity increases
Solution Approach 1:
The patent segments the current optimization space by defining specific search zones with upper and lower D-axis reference current boundaries. Instead of treating the entire current space as one optimization problem, the controller divides it into manageable segments based on the initial MTPA curve values. This segmentation allows precise current selection within each zone while keeping the control algorithm complexity manageable through localized optimization.
Solution Approach 2:
The patent applies partial action by focusing optimization efforts only within defined search zones rather than the entire operating range. The controller generates upper and lower bounds for D-axis reference current based on the initial curve, then performs iterative modifications only within these partial ranges. This approach achieves sufficient precision for practical applications without requiring exhaustive search of all possible current combinations.
Data Source
AI summary
For improving Maximum Torque per Amps (MTPA) control, a method generates an offline MTPA curve based on an autotune test for a motor, which is used as offline MTPA control in order to run a motor at a high efficiency operation point. Another online method generates a search zone for the MTPA curve for a given torque point. The search zone includes an upper D-axis reference current and a lower D-axis reference current for the given torque point. The method iteratively modifies a D-axis reference current between the upper D-axis reference current and the lower D-axis reference current of the search zone. The method modifies a Q-axis reference current to output the given torque. The method updates a corresponding current pair of the given torque point to the modified D-axis reference current and the modified Q-axis reference current with a lowest current amplitude to improve MTPA control of the motor.