Bus Current Limiting Through Torque Feedback in EV Power Systems
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Solution Overview
Problem
Passive overcurrent protection in high-voltage power supply systems of electric vehicles leads to damage to vehicle parts and safety risks due to excessive temperature and insulation aging.
Innovation Solution
A bus current control method that dynamically adjusts the limit current and target requested torque based on motor speed, actual current, and torque data, using a set of correction coefficients and historical data to prevent overcurrent and ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive overcurrent protection (fuse blowing) is used, then the system structure is simple, but the bus current cannot be effectively limited causing damage to vehicle parts and safety risks
Solution Approach 1:
The patent implements dynamic current limiting by continuously adjusting the current limit based on motor speed and actual current feedback. The control unit dynamically modifies the current limit parameter during operation, transitioning from static fuse protection to adaptive active protection that responds to real-time system conditions.
Solution Approach 2:
The system employs feedback control by monitoring actual bus current and comparing it against the dynamic current limit. When overcurrent is detected, the control unit adjusts the current limit and requests torque based on feedback from actual current, motor speed, and requested torque, creating a closed-loop control system that actively prevents overcurrent damage.
2Object-affected harmful factors
If dynamic current limiting control is implemented, then bus current is effectively limited within safe range, but the control system complexity increases
Solution Approach 1:
The control unit performs multiple functions: it determines current limits based on motor speed, monitors actual current, calculates requested torque adjustments, and controls the motor. By consolidating these functions in a single control unit, the patent reduces overall system complexity while achieving effective dynamic current limiting and overcurrent protection.
Solution Approach 2:
The system changes control parameters (current limit, requested torque) based on operating conditions (motor speed, actual current). The control unit adjusts these parameters dynamically to maintain bus current within safe ranges, using parameter variation as the core mechanism for both protection and control functions.
3Ease of operation
If limit current is determined solely by motor speed, then the control is simple, but it cannot respond to actual current conditions causing ineffective overcurrent protection
Solution Approach 1:
The control unit employs feedback control by monitoring actual bus current and comparing it against the dynamic current limit. When overcurrent is detected, the control unit adjusts the current limit and requests torque based on feedback from actual current, motor speed, and requested torque.
Solution Approach 2:
The system determines a preliminary current limit based on motor speed before actual overcurrent occurs. This preliminary limit serves as a preventive measure, and the control unit further adjusts it based on real-time current conditions, combining predictive and reactive control strategies.
Data Source
AI summary
Disclosed are a bus current control method, a device, a system and a storage medium. The method includes: obtaining a data set including a motor speed corresponding to a current time point, an actual current and an actual torque; determining a limit current at the current time point according to the motor speed; in response to the limit current being less than the actual current, determining a deviation value at the current time point according to the limit current and the actual current; determining a target requested torque based on the deviation value and the actual torque; and determining the bus current according to the target requested torque.