Battery Current-Based Speed Limiting for EDS Overload Prevention
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Solution Overview
Problem
Electric vehicles face overloading issues in their electrical distribution systems, leading to overheating of components due to high current demands, especially when operating at maximum speeds, which can result in power limiting and a disconnect between driver expectations and vehicle performance.
Innovation Solution
A controller is programmed to reduce the vehicle's speed limit from a maximum to an electrical distribution system (EDS) speed limit based on measured current capacity, commanding a torque to the electric machine that is less than the driver-demanded torque to prevent current saturation, thereby maintaining the vehicle below the EDS speed limit and reducing the need for power limiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the vehicle operates at maximum speed, then the vehicle performance and driver satisfaction are improved, but the electrical distribution system may be overloaded causing overheating and power limiting
Solution Approach 1:
The controller proactively reduces the speed limit before the electrical distribution system becomes overloaded by monitoring current capacity and adjusting the speed limit in advance. This preliminary action prevents overloading and overheating from occurring, maintaining system reliability while allowing the vehicle to operate at or near maximum speed under normal conditions.
2Temperature
If the speed limit is reduced to prevent EDS overloading, then the electrical component overheating is prevented, but the vehicle performance and driver satisfaction deteriorate
Solution Approach 1:
The speed limit is made dynamic rather than static, automatically adjusting based on real-time electrical distribution system current capacity. When the EDS can handle high current, the vehicle maintains maximum speed. When current capacity diminishes, the speed limit is gradually reduced to prevent overloading. This dynamic adjustment prevents electrical component overheating while minimizing the impact on vehicle performance and driver satisfaction.
3Reliability
If abrupt power limiting is implemented to protect the EDS, then the electrical system is protected from damage, but the driving experience deteriorates due to sudden performance loss
Solution Approach 1:
The controller gradually reduces the speed limit in advance before the electrical distribution system becomes overloaded, rather than implementing abrupt power limiting when overloading occurs. This preliminary and gradual adjustment protects the electrical system from damage while maintaining a smooth driving experience, as the driver experiences progressive speed reduction rather than sudden performance loss.
Data Source
AI summary
According to one embodiment, a vehicle includes an electrified propulsion system having an electric machine powered by a traction battery over an electrical distribution system (EDS). A controller is programmed to, reduce a speed limit of the vehicle from a maximum speed limit to an EDS speed limit in response to a measured average current of the EDS being within a threshold percentage of an average current limit of the EDS, and, in response to a measured speed of the vehicle exceeding the EDS speed limit, command a torque to the electric machine that is less than a driver-demanded torque such that the vehicle is propelled at a speed below the EDS speed limit.