EV DC Bus Discharge Control Using Motor Isolation Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric vehicle systems, there is a challenge in controlling the discharge of a direct current (DC) bus to a desired level within a specific time frame without unexpected recharging by the electric motor or other components, which can disrupt the discharge process.
Innovation Solution
The system alternates between two modes: a DC bus isolation mode and a current injection mode, using a switching component to isolate the electric motor from the capacitor and inject current into the motor to manage the discharge, preventing recharging and maintaining control over the DC bus voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is left connected to the DC bus during discharge, then the system structure remains simple, but the motor may unexpectedly recharge the DC bus and disrupt the discharge process
Solution Approach 1:
A switching component is introduced as an intermediary between the electric motor and the DC bus capacitor. This switch isolates the motor from the capacitor during discharge operations, preventing unexpected recharging while maintaining system reliability. The controller manages the switching component to enable or disable motor connection based on operational requirements.
2Reliability
If the DC bus discharge time is extended to ensure complete discharge, then discharge thoroughness is improved, but the system loses time efficiency and productivity
Solution Approach 1:
The system performs preliminary actions by isolating the motor from the DC bus before discharge begins, and by pre-charging the capacitor through the motor in controlled intervals during discharge. This prevents discharge interruptions and ensures complete discharge without extending total discharge time, maintaining system productivity.
Solution Approach 2:
The controller implements periodic switching between motor isolation and motor-connected states during the discharge process. The motor is periodically reconnected to charge the capacitor at controlled intervals, then isolated again to allow discharge. This periodic action ensures complete discharge while maintaining efficient timing through automated cycle management.
3Manufacturing precision
If the switching component frequently alternates between isolation and connection modes to prevent recharging, then discharge control precision is improved, but the switching component experiences increased wear and reduced reliability
Solution Approach 1:
The controller implements partial action by keeping the motor isolated for the majority of the discharge time, with brief periodic reconnections for capacitor recharging. This reduces the total number of switching cycles compared to continuous switching, thereby reducing wear on the switching component while maintaining sufficient voltage control precision through the periodic control strategy.
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 approach effectively prevents unexpected recharging and ensures controlled discharge of the DC bus, maintaining stability and efficiency in the electric vehicle's energy management system.
Implementation Method 1
The switching component can enter a first state to cause the electric motor to convert electrical power of the capacitor to mechanical power to propel the electric vehicle, or convert mechanical power from a drive system of the electric vehicle to electrical power to charge the capacitor
Implementation Method 2
The propulsion component can, in the second state, convert from electrical or mechanical energy to thermal energy
Data Source
AI summary
High voltage discharge is provided. A system can include an electric motor of an electric vehicle electrically connected to a capacitor. A switching component can be connected with and intermediary to the electric motor and the capacitor. A controller can cause the switching component to enter a first state to cause the electric motor to convert electrical power of the capacitor to mechanical power to propel the electric vehicle, or convert mechanical power from a drive system of the electric vehicle to electrical power to charge the capacitor. The controller can cause the switching component to enter, in response to detection by the controller of an indication to discharge the capacitor, a second state to isolate the electric motor from the capacitor.