Inverter Power Switch Discharge for DC Link Capacitor Shutdown
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Solution Overview
Problem
Regulatory agencies require the charge on DC link capacitors in electric drive systems to be dissipated within a short time after shutdown, but existing methods can lead to high current and potential damage to components.
Innovation Solution
Utilize power switches in the electric motor to actively discharge the DC link capacitor by controlling the voltage difference between control and reference terminals, adjusting the current conduction through the power switches to manage the discharge process without causing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a discharge switch and resistor are used to discharge the DC link capacitor after shutdown, then the capacitor charge is dissipated within regulatory time requirements, but high current flows through the discharge path causing potential damage to components
Solution Approach 1:
The patent introduces an intermediary discharge path through the inverter's power switching elements instead of using a dedicated discharge switch and resistor. The inverter acts as a mediator between the DC link capacitor and the discharge path, controlling current flow through its switching elements to dissipate capacitor charge without exposing external discharge components to damaging high currents
Solution Approach 2:
The patent makes the inverter serve multiple functions: it acts as both the power conversion device during normal operation and as the discharge path during shutdown. By utilizing the existing power switching elements of the inverter for discharge purposes, the system eliminates the need for separate discharge components and avoids subjecting them to high current stress
2Reliability
If the battery is isolated from the electric drive system during shutdown, then system safety is improved, but the DC link capacitor retains charge requiring additional discharge measures
Solution Approach 1:
The inverter is designed to perform dual functions: power conversion during operation and capacitor discharge during shutdown. This multi-functionality eliminates the need for separate discharge switches and resistors, reducing system complexity while maintaining safety through battery isolation
Solution Approach 2:
The inverter's own power switching elements are utilized to perform the discharge function, making the system self-sufficient. The inverter serves itself by using its internal components to dissipate the capacitor charge that accumulates during operation, eliminating the need for external discharge infrastructure
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
Effectively discharges the DC link capacitor while preventing damage to components by maintaining low current levels, ensuring compliance with regulatory requirements.
Implementation Method 1
adjusting the current conduction through the power switches to manage the discharge process
Data Source
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AI summary
Systems, devices, and methods for active discharge of an electric drive system. In one implementation, an electric drive system for a vehicle includes an inverter having at least one phase leg, wherein a first of the phase legs includes a first power switch, a dc/dc converter configured to generate an internal supply voltage that is regulated with respect to a voltage on a rail configured to be coupled to a dc power supply, and a gate drive channel configured to drive the first power switch into conductance by applying a relatively high voltage difference derived from the internal supply voltage during operation of the vehicle and to continue the driving of the first power switch with a relatively lower voltage difference derived from the internal supply voltage after a signal indicating shut-down or fault of the vehicle. The dc/dc converter is configured to generate the internal supply voltage to have either a relatively high voltage difference with respect to the voltage on the rail or a relatively lower voltage difference with respect to the voltage on the rail.