Inverter Safety Mode Selection for Overvoltage and Phase Heating
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Solution Overview
Problem
Existing inverter control systems in electric vehicles lack effective mechanisms to manage safety modes in the event of failure, particularly in situations like power or software failures, which can lead to overheating, overvoltage, and excessive braking, risking damage to the inverter and battery.
Innovation Solution
A redundant control system using a second control device, such as a simple electronic circuit without a microcontroller, selects between Active Short Circuit (ASC) and Freewheeling (FW) modes based on voltage and rotational speed or current thresholds to prevent damage and ensure functional safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second microcontroller or programmable logic component is used to manage safety status, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses a simplified copy of the main microcontroller's safety management function, implemented through basic electronic circuits that replicate only the essential safety status detection and response capabilities, rather than using a full second microcontroller or complex programmable logic device
Solution Approach 2:
The patent employs simple, inexpensive electronic components (such as voltage dividers, resistors, and basic logic gates) to implement safety management functionality, accepting that these components may need replacement but prioritizing low cost and simplicity over long-term durability
2Reliability
If ASC mode is applied to prevent overvoltage, then reliability is improved, but temperature increases due to large current flow
Solution Approach 1:
The patent dynamically switches between different safety modes (ASC mode, freewheeling mode, and resistance mode) based on real-time system conditions such as voltage levels, current flow, and temperature, rather than applying a single static safety mode
Solution Approach 2:
The patent changes operational parameters by switching between different safety modes with distinct characteristics: ASC mode for overvoltage protection, freewheeling mode for current dissipation, and resistance mode for controlled energy dissipation, selecting the appropriate mode based on measured system parameters
3Temperature
If FW mode is applied to reduce heating, then temperature is reduced, but overvoltage and uncontrolled regeneration may occur
Solution Approach 1:
The patent dynamically transitions between freewheeling mode and other safety modes based on real-time monitoring of voltage and current conditions, switching to ASC mode or resistance mode when overvoltage risks are detected
Solution Approach 2:
The patent implements feedback control by continuously monitoring system voltage, current, and temperature, and using this information to determine when to switch between different safety modes, ensuring appropriate protection against overvoltage while managing temperature
Data Source
AI summary
A method is disclosed for controlling an inverter controlled by a first control device in a nominal operating mode and by a second control device to apply a safety operating mode chosen from an Active Short Circuit (ASC) mode and a freewheeling (FW) mode. The method comprises determining the voltage on a high-voltage bus (UHVDC). If the voltage is lower than a first voltage threshold (Uthi), the FW mode is selected; if the voltage is greater than a second voltage threshold (Uth2) greater than Uthi, the ASC mode is selected; and if the voltage is between Uthi and Uth2, a parameter representative of the ability to inject power onto the UHVDC in a risk free manner is determined. If this parameter is greater than or equal to a threshold value, ASC mode is selected and if the parameter is lower than the threshold value, FW mode is selected.