Motor Inverter Control Using Efficiency Maps Across Torque-Speed Range
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Solution Overview
Problem
Existing motor systems in electrified vehicles face challenges in achieving efficient operation across the entire operating space due to a large number of controllable parameters and settings, which complicates control and efficiency optimization.
Innovation Solution
The implementation of efficiency maps that correspond to predetermined combinations of motor system control parameters, such as PWM schemes, switching frequencies, gate drive parameters, and DC link voltages, allows for determining the highest efficiency solution at any given operating point, with considerations for noise, vibration, harshness, motor bearing life, and RESS life through Pareto front analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple motor system control parameters with multiple selectable settings are used, then motor system efficiency can be optimized across different operating conditions, but the complexity of control increases significantly
Solution Approach 1:
The patent segments the control parameter space by dividing it into multiple efficiency maps, where each map corresponds to a specific combination of control parameters (such as PWM scheme, switching frequency, gate drive parameter, and DC link voltage). This segmentation allows the complex multi-parameter optimization problem to be broken down into multiple simpler lookup operations, where the controller can select the appropriate efficiency map based on current operating conditions without having to evaluate all possible parameter combinations simultaneously.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing efficiency maps for various combinations of control parameters before actual operation. These efficiency maps are generated in advance through simulations or experiments, capturing the optimal efficiency solutions for different operating conditions. During real-time control, the system simply needs to select the appropriate pre-computed map based on current motor speed and torque requirements, eliminating the need for complex real-time optimization calculations.
2Loss of energy
If efficiency maps for multiple parameter combinations are maintained, then optimal efficiency solutions can be found across the entire motor operating space, but memory and computational resources increase
Solution Approach 1:
The patent applies local quality by generating efficiency maps with different levels of detail and resolution tailored to specific operating regions. Instead of using uniformly high-resolution maps across the entire operating space, the system can use finer-grained maps for frequently operated or critical efficiency regions, while using coarser maps for less critical regions. This approach optimizes memory usage by allocating storage resources proportionally to the actual needs of different operating conditions.
Solution Approach 2:
The patent merges multiple efficiency maps by implementing a selection mechanism that chooses the most appropriate map based on current operating conditions (motor speed and torque). Instead of maintaining and evaluating all parameter combinations simultaneously, the system merges the information from multiple maps through selective activation, where only the relevant map for the current operating region is loaded and used. This significantly reduces the effective memory footprint while maintaining comprehensive coverage of the operating space.
Data Source
AI summary
A motor system includes a rechargeable energy storage system, an alternating current motor, and a power inverter. Multiple efficiency maps may be provided, each representing a specific combination of control parameters and associated settings. The maps relate the motor's operating space (torque and speed) to corresponding efficiency solutions. The combination of control parameters and settings that yields the highest motor system efficiency at an operating point may be determined from the multiple efficiency maps and used in controlling the motor.