Inverter Control Device Partial Shutdown DC Link Voltage
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Solution Overview
Problem
In high-output alternating current rotating electric machines used in electric and hybrid automobiles, a contactor open state can lead to a rise in DC link voltage and excessive reflux current, causing wear and increasing costs due to the need for higher capacitance and withstand voltage in smoothing capacitors and switching elements.
Innovation Solution
An inverter control device that executes partial shutdown control by switching off a switching element in one phase and then full shutdown control when currents in other phases reach zero, reducing DC link voltage rise and reflux current, while maintaining zero current in the rotating electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shutdown control is implemented to switch all switching elements to off state when contactor opens, then DC link voltage rise is suppressed, but large reflux current flows through switching elements and stator coil causing wear and reduced lifetime
Solution Approach 1:
The patent applies partial shutdown control by selectively switching off only specific switching elements (e.g., upper side switching elements in certain phases) rather than all switching elements. This partial action allows the inverter to suppress DC link voltage rise while minimizing reflux current flow, thereby reducing wear on switching elements and stator coil compared to complete shutdown control.
2Strength
If active short control is implemented to allow current reflux, then DC link voltage rise is suppressed, but large current continues to flow through switching elements and stator coil causing wear and reduced lifetime
Solution Approach 1:
The patent implements a controlled transition from active short control to partial shutdown control. By partially switching off specific switching elements while maintaining others in on state, the system suppresses DC link voltage rise and limits reflux current duration, reducing wear on components compared to continuous active short control.
3Reliability
If smoothing capacitor is given higher capacitance and higher withstand voltage to handle DC link voltage rise, then voltage stability is improved, but physical size of smoothing capacitor and inverter increases
Solution Approach 1:
The patent changes the operational parameters of the inverter by implementing partial shutdown control strategies that selectively switch off specific switching elements. This control approach limits the magnitude and duration of DC link voltage rise, allowing the use of smaller smoothing capacitors with lower withstand voltage ratings while maintaining voltage stability during contactor open events.
4Reliability
If inverter is designed with higher withstand voltage to handle DC link voltage rise, then voltage stability is improved, but manufacturing cost and product cost increase
Solution Approach 1:
The patent modifies the operational parameters through partial shutdown control, limiting DC link voltage rise to levels that standard-rated inverter components can handle. This approach maintains voltage stability during contactor open events while avoiding the need for expensive high-withstand voltage components, thereby reducing manufacturing and product costs.
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 configuration effectively suppresses DC link voltage rise and reflux current, reducing the need for high-capacitance smoothing capacitors and high-withstand switching elements, thereby minimizing size and cost increases in the rotating electric machine drive device.
Implementation Method 1
a smoothing capacitor (DC link capacitor) for smoothing DC voltage (DC link voltage) is often provided on the DC side (in the DC link portion) of the inverter
Implementation Method 2
the electrical power stored in the stator coil charges the smoothing capacitor via free wheel diodes (FWDs) that are connected in reverse-parallel to the switching elements
Data Source
AI summary
An inverter control device for controlling a rotating electric machine drive device that includes an inverter and a DC link capacitor, the inverter being connected to a DC power supply via a contactor, being connected to an alternating current rotating electric machine, and performing power conversion between direct current and three-phase alternating current, an arm for each alternating current phase being formed by a series circuit including an upper side switching element and a lower side switching element, and the DC link capacitor smoothing a DC link voltage, which is a DC-side voltage of the inverter, the inverter control device performing switching control on the switching elements that form the inverter.