EV Drive System Regenerative Braking Battery Protection
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Solution Overview
Problem
In electric vehicles with regeneration cooperative brake systems, stopping regeneration operation during battery unchargeability leads to instability and insufficient braking force, causing anxiety for the driver and compromising vehicle stability.
Innovation Solution
An electric vehicle drive system with a battery monitoring unit that diagnoses unchargeable battery states and outputs an unchargeable signal, and a rotating electrical machine control unit that executes loss increase control to reduce regenerative electric power while maintaining torque, thereby stabilizing vehicle travel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the regeneration operation of the rotating electrical machine is immediately stopped when battery unchargeability is detected, then the battery is protected from overcharging, but the braking force becomes insufficient and vehicle traveling stability deteriorates
Solution Approach 1:
The system performs preliminary diagnosis to determine battery chargeability status before fully stopping regeneration operation. The battery monitoring unit continuously monitors battery state and performs diagnosis procedures (such as checking charge acceptance capability) before triggering a complete stop of regeneration, allowing for smoother transition and maintaining stability.
Solution Approach 2:
The system dynamically adjusts the regeneration operation based on real-time battery diagnosis results. Instead of an immediate binary stop, the control unit modulates the regeneration brake force according to the battery's charge acceptance capability, creating a dynamic balance between battery protection and vehicle stability requirements.
2Reliability
If the regenerative brake force is reduced to protect the battery, then the battery overcharging is prevented, but the total braking force becomes insufficient
Solution Approach 1:
The system merges the regenerative brake force with friction brake force to maintain total braking force. When battery unchargeability is detected, the control unit coordinates both braking systems work together, with the friction brake compensating for the reduced regenerative brake force, ensuring the sum of both forces meets the driver's braking demand while protecting the battery.
Solution Approach 2:
The system changes the distribution parameters of braking force between regenerative and friction brakes. When battery chargeability is limited, the control unit adjusts the proportion of regenerative brake force downward and friction brake force upward, maintaining the total braking force parameter at the required level while adapting to battery constraints.
3Reliability
If the phase of currents is changed to lower power generation amount, then the battery charging is restricted, but the torque of the rotating electrical machine is maintained
Solution Approach 1:
The system changes the phase angle parameter of the current to control power generation. By adjusting the current phase (power factor) rather than simply reducing current magnitude, the system maintains torque production while limiting the active power transferred to the battery, thereby controlling charging amount without significantly reducing power generation efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution improves vehicle travel stability by reducing regenerative electric power during regeneration cooperative braking, ensuring stable braking force and preventing battery overcharging.
Implementation Method 1
the rotating electrical machine is regeneratively operated to generate braking force and regenerative electric power generated at that time is returned to a battery to charge it therewith
Implementation Method 2
a battery monitoring unit that is loaded on an electrically driven vehicle provided with a regeneration cooperative brake control device and monitors the state of a battery
Data Source
AI summary
In order to provide an electric vehicle drive system capable of promoting improvement in stability of vehicle traveling when stopping a regeneration operation during operation of a regeneration cooperative brake, the electric vehicle drive system, a battery control unit 310, upon detecting that a battery state is an unchargeable state during control of the regeneration cooperative brake, diagnoses whether a battery 300 is chargeable, and upon deciding to be unchargeable from a result of diagnosis, outputs a Fail signal. Then, a rotating electrical machine control unit 210, upon receiving a Fail prediction signal while the regeneration cooperative brake is being controlled, executes loss increase control for increasing an internal loss of a rotating electrical machine 900 and reducing regenerative electric power by a regenerative brake while maintaining torque of the rotating electrical machine 900 at regenerative torque corresponding to regenerative brake force.