EV Inverter Active Discharge Using Three-Phase Short and Pulse Control
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Solution Overview
Problem
Conventional high voltage discharge systems in electrified vehicles are costly, heavy, and can limit electric motor speed, necessitating the development of more efficient and lightweight solutions.
Innovation Solution
An inverter active discharge system using existing power modules, employing a three-phase short condition and periodic pulse waveform to quickly discharge the high voltage bus without additional components, with optional reprogramming of gate drive integrated circuits for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional resistor banks and switches are used for fast discharging of high voltage bus, then discharge speed is improved, but vehicle cost, packaging space, and weight are drastically increased
Solution Approach 1:
The patent extracts the discharge function from dedicated external components (resistor banks and switches) and relocates it to the existing inverter power modules. By utilizing the inverter's existing switches and control circuitry, the system eliminates the need for separate discharge resistors and associated components, thereby reducing vehicle weight while maintaining fast discharge capability.
Solution Approach 2:
The inverter power modules are made multi-functional by enabling them to perform both motor driving and high voltage discharge operations. The same switches and control circuitry that drive the electric motor are repurposed to discharge the high voltage bus, eliminating dedicated discharge components and reducing overall system weight and cost.
2Speed
If conventional resistor banks and switches are used for fast discharging of high voltage bus, then discharge speed is improved, but vehicle cost is drastically increased
Solution Approach 1:
The discharge functionality is extracted from separate dedicated components and integrated into the existing inverter control system. This eliminates the need for additional resistor banks, discharge switches, and associated control circuitry, thereby reducing system complexity and vehicle cost while preserving fast discharge performance.
Solution Approach 2:
The inverter control system is enhanced to perform dual functions: motor driving and high voltage discharge. By programming the existing control unit to recognize discharge requests and activate appropriate switch sequences, the system achieves fast discharge without adding dedicated discharge hardware, thus reducing complexity and cost.
3Reliability
If conventional discharge systems are used, then discharge function is achieved, but electric motor speed is limited
Solution Approach 1:
The system dynamically adapts its operation mode based on real-time conditions. The control system can seamlessly transition between motor driving mode and discharge mode by adjusting switch states and control parameters. This dynamic capability ensures that the discharge function is reliably achieved when needed while maintaining full motor speed capability during normal operation, as the discharge function is activated only through specific discharge requests.
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
The system effectively reduces high voltage to a safe level without additional components, balancing switch temperatures and improving discharge speed, thus reducing vehicle weight and cost while maintaining motor performance.
Implementation Method 1
a three-phase inverter to convert high voltage direct current (DC) power to high voltage alternating current (AC) power
Implementation Method 2
commanding one set of the set of upper switches and the set of lower switches of the three-phase inverter to each be in an ON state to cause a three-phase short across the three-phase inverter to prevent back electromotive force (EMF) from supporting the high voltage bus
Implementation Method 3
commanding the other set of the set of upper switches and the set of lower switches of the three-phase inverter according to a periodic pulse waveform to allow shoot-through current to quickly discharge the high voltage bus
Data Source
AI summary
An inverter active discharge technique for an electrified vehicle includes in response to detecting the discharge request, performing an active inverter discharge procedure including commanding one set of the set of upper switches and the set of lower switches of a three-phase inverter to each be in an ON state to cause a three-phase short across the three-phase inverter to prevent back electromotive force (EMF) from supporting a high voltage bus, wherein the three-phase inverter is configured to convert an input direct current (DC) voltage to output alternating current (AC) voltages for powering an electric motor of the electrified vehicle, and during the three-phase short, commanding the other set of the set of upper switches and the set of lower switches of the three-phase inverter according to a periodic pulse waveform to allow shoot-through current to quickly discharge the high voltage bus.