DC Link Capacitor Discharge Using Controlled Inverter Shoot-Through
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Solution Overview
Problem
Traditional methods for discharging energy from DC link capacitors in electric vehicle traction inverters require bulky and expensive discharge resistors, leading to inefficiencies and increased system complexity, which do not meet the safety and cost-effectiveness requirements of automotive safety regulations.
Innovation Solution
A system utilizing a discharge controller that activates a controlled shoot-through of transistors in the inverter to dissipate energy from the DC link capacitor, eliminating the need for additional resistors and leveraging existing components for efficient energy discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional discharge resistors are used to dissipate energy from the DC link capacitor, then the safety discharge requirement is met, but the system becomes bulky, expensive, and complex
Solution Approach 1:
The discharge function is merged with the existing inverter transistors. The same transistors that perform normal inversion functions are also used for capacitor discharge by creating a shoot-through condition, eliminating the need for separate discharge resistors and control circuitry.
Solution Approach 2:
The inverter transistors are made multi-functional by enabling them to perform both normal inversion operations and capacitor discharge operations. The discharge controller utilizes the existing transistor structure to achieve discharge, making the transistors universal components that serve multiple purposes.
2Reliability
If traditional discharge resistors are used to dissipate energy from the DC link capacitor, then the safety discharge requirement is met, but the system cost increases
Solution Approach 1:
The discharge function is merged with the existing inverter transistors. The same transistors that perform normal inversion functions are also used for capacitor discharge by creating a shoot-through condition, eliminating the need for separate discharge resistors and control circuitry.
Solution Approach 2:
The inverter's own transistors serve the dual purpose of normal operation and discharge function. The system uses its existing components to perform the discharge task, eliminating the need for additional dedicated discharge components and reducing overall system cost.
3Reliability
If traditional discharge resistors are used to dissipate energy from the DC link capacitor, then the safety discharge requirement is met, but the system weight increases
Solution Approach 1:
The discharge function is merged with the existing inverter transistors. The same transistors that perform normal inversion functions are also used for capacitor discharge by creating a shoot-through condition, eliminating the need for separate discharge resistors and control circuitry.
Solution Approach 2:
The discharge resistors are extracted from the system entirely. Instead of adding discharge resistors, the invention removes them by using the inverter transistors themselves to perform the discharge function through controlled shoot-through, thereby reducing system weight.
4Reliability
If traditional discharge resistors are used to dissipate energy from the DC link capacitor, then the safety discharge requirement is met, but energy efficiency decreases
Solution Approach 1:
The discharge is performed through controlled periodic switching of the transistors. The discharge controller activates the transistors in a controlled manner to create shoot-through conditions, enabling rapid energy dissipation through the existing power semiconductor devices rather than continuous resistance-based dissipation.
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 reduces system weight, cost, and complexity while enhancing energy efficiency and response times, effectively meeting automotive safety standards for rapid DC link capacitor discharge.
Implementation Method 1
a discharge controller configured to cause a discharge of energy from the DC link capacitor by turning on at least a first transistor and a second transistor of the inverter so as to cause a controlled shoot-through
Data Source
AI summary
There is provided an inverter system comprising a DC input for connecting to a DC power source. The inverter system comprises a plurality of transistors that are controllable to convert a DC voltage to an AC voltage. The inverter system further comprises a DC link capacitor coupled to the DC input of the inverter system and a discharge controller configured to cause a discharge of energy from the DC link capacitor when the DC power source is disconnected from the DC input of the inverter system. The discharge controller is configured to cause the discharge of energy from the DC link capacitor by turning on at least a first transistor and a second transistor so as to cause a controlled shoot-through of the inverter system. At least one of the first transistor and the second transistor are controlled by the discharge controller to operate in a linear region of operation.