Bidirectional Matrix Converter DC Bus Capacitor Discharge
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Solution Overview
Problem
Bidirectional matrix converters in vehicles face challenges in safely discharging high voltage DC bus capacitors when the DC energy source is disconnected or the converter is removed, requiring effective methods to reduce voltage to a safe level without additional hardware or heat sink requirements.
Innovation Solution
The electrical system incorporates a DC interface, an AC interface, a DC bus capacitor, first and second energy conversion modules with switching elements, an isolation module, and a control module that detects the need to discharge the capacitor, shorting the AC interface and modulating the switching elements to establish a current path through an inductive element, allowing controlled discharge of the capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a DC bus capacitor is used to deliver high power over a wide range of operating voltages, then power delivery capability is improved, but the voltage across the capacitor becomes hazardous when the energy source is disconnected
Solution Approach 1:
The patent extracts the discharge function from the main energy conversion path by using the AC interface and inductive element as a separate discharge pathway. When discharge is needed, the AC interface is shorted and the switching elements are arranged to create a current path through the inductive element, isolating the discharge function from normal power delivery operations.
Solution Approach 2:
The inductive element coupled to the AC interface serves as an intermediary for energy transfer during discharge. The switching elements act as intermediaries to redirect current flow from the DC bus capacitor through the inductive element to the shorted AC interface, enabling controlled discharge without direct connection to the DC energy source.
2Reliability
If additional hardware is added to discharge the DC bus capacitor, then discharge capability is improved, but device complexity increases
Solution Approach 1:
The AC interface and inductive element, which are already part of the matrix converter structure, are given a dual function: normal AC power conversion and DC bus capacitor discharge. The switching elements are configured to perform both standard energy conversion operations and discharge operations by changing their arrangement, eliminating the need for dedicated discharge hardware.
Solution Approach 2:
The matrix converter system discharges its own DC bus capacitor using its existing components (AC interface, inductive element, and switching elements) without requiring external discharge modules or additional hardware. The control module orchestrates the self-discharge process by detecting when discharge is needed and configuring the switching elements appropriately.
3Productivity
If a discharge path is created through the AC interface, then discharge efficiency is improved, but thermal design parameters may be affected
Solution Approach 1:
The discharge process uses periodic switching of the switching elements to alternately charge and discharge current in the inductive element. This periodic action distributes the thermal load over time rather than concentrating it in a single continuous discharge path, allowing heat to dissipate between switching cycles and maintaining thermal design parameters.
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 method enables safe and efficient discharge of the DC bus capacitor to a low voltage state without additional hardware, maintaining thermal design parameters and avoiding the need for external discharge modules, ensuring safety and operational efficiency.
Implementation Method 1
an inductive element coupled between the second energy conversion module and the AC interface
Implementation Method 2
modulating one or more of the plurality of switching elements of the first energy conversion module
Data Source
AI summary
A system and method of discharging a bus capacitor of a bidirectional matrix converter of a vehicle are presented here. The method begins by electrically shorting the AC interface of the converter after an AC energy source is disconnected from the AC interface. The method continues by arranging a plurality of switching elements of a second energy conversion module into a discharge configuration to establish an electrical current path from a first terminal of an isolation module, through an inductive element, and to a second terminal of the isolation module. The method also modulates a plurality of switching elements of a first energy conversion module, while maintaining the discharge configuration of the second energy conversion module, to at least partially discharge a DC bus capacitor.