Electric Machine dq Current Control for Zero-Speed Torque
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Solution Overview
Problem
Existing electric machines experience torque output reduction and switch degradation at zero rotational speed due to uneven heat distribution among inverter legs, leading to increased financial and weight costs when addressing this issue.
Innovation Solution
Generating a dq phase angle in response to motor maximum torque per ampere and inverter current angle to adjust direct and quadrature currents, optimizing torque generation while reducing switch degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current flow through inverter legs is reduced to prevent switch degradation, then switch reliability is improved, but torque output decreases by more than 15%
Solution Approach 1:
The system dynamically adjusts the dq phase angle based on real-time operating conditions (motor MTPA angle and inverter current angle) to optimize torque generation while managing heat distribution. This dynamic control allows the system to maintain high torque output even when current flow is constrained to prevent switch degradation.
Solution Approach 2:
The invention changes the operational parameters by introducing a dynamically calculated dq phase angle that modifies the current distribution among inverter legs. This parameter adjustment enables the system to generate higher torque for a given current flow while preventing any single leg from exceeding thermal limits, thus resolving the contradiction between torque output and switch reliability.
2Power
If conductor and switch capacity is increased to handle maximum current, then torque output is maintained, but system financial expense and weight increase
Solution Approach 1:
Instead of increasing hardware capacity, the system changes operational parameters by optimizing the dq phase angle to distribute current more efficiently among existing inverter legs. This allows the same hardware to deliver higher torque output without requiring heavier or more expensive conductors and switches.
Solution Approach 2:
The invention replaces a mechanical/hardware solution (increasing conductor and switch capacity) with a control/software solution (dynamic dq phase angle calculation). This substitution maintains torque output while avoiding the weight and cost penalties of upgraded hardware.
3Power
If conductor and switch capacity is increased to handle maximum current, then torque output is maintained, but system financial expense increases
Solution Approach 1:
The invention replaces a hardware-intensive solution with a control algorithm that calculates and applies an optimized dq phase angle. This software-based approach maintains torque output without requiring expensive upgrades to conductors, switches, or other physical components, thereby reducing system financial expense.
Solution Approach 2:
The system achieves higher torque output by changing operational parameters (dq phase angle) rather than upgrading hardware capacity. This parameter optimization allows existing components to operate more efficiently, avoiding the need for expensive high-capacity conductors and switches.
Data Source
AI summary
Methods and system for operating an electric machine are shown. In one example, direct current and quadrature current that is supplied to an electric machine via an inverter are adjusted in response to a difference between two angles. The method and system may be particularly useful for operating the electric machine at lower rotational speeds.