DC Link Overvoltage Protection in Power Converter-Inverter Circuits
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Solution Overview
Problem
Conventional power conversion devices face challenges in efficiently managing overvoltage conditions and minimizing energy loss during switching operations, particularly in applications like air conditioner refrigerant compressors, where regenerative braking and overvoltage protection require high-power components that increase device size and cost.
Innovation Solution
The power conversion device incorporates a unique configuration with a converter circuit, an inverter circuit, a capacitor for voltage smoothing, and an overvoltage protection circuit using wide-bandgap semiconductors, along with control units to manage switching operations and overvoltage protection, allowing for efficient energy management and reduced component size through shared heat dissipation mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-power components are used for overvoltage protection and regenerative braking, then protection reliability is improved, but device size and cost increase
Solution Approach 1:
The patent combines the overvoltage protection function with the existing DC link capacitor structure. The protection circuit uses the DC link capacitor as part of its operation, merging the protection function with the voltage smoothing function already present in the system, thereby avoiding additional large components while maintaining protection reliability
Solution Approach 2:
The DC link capacitor serves multiple functions: voltage smoothing during normal operation and overvoltage protection during abnormal conditions. This multi-functionality eliminates the need for separate dedicated protection components, reducing overall device size while maintaining both operational and protective functions
2Reliability
If high-power components are used for regenerative braking and overvoltage protection, then protection capability is improved, but manufacturing cost increases
Solution Approach 1:
The protection circuit is integrated with existing system components, particularly utilizing the DC link capacitor and control unit already present in the power conversion device. This integration avoids the need for separate high-cost protection components while maintaining comprehensive protection capability
Solution Approach 2:
The system uses its own existing components (DC link capacitor, control unit) to provide overvoltage protection and regenerative braking functions, rather than requiring external dedicated protection devices. This self-service approach reduces component count and manufacturing cost while maintaining protection effectiveness
3Strength
If DC link voltage variation is allowed, then capacitor stress is reduced, but output voltage stability deteriorates
Solution Approach 1:
The control unit dynamically adjusts the inverter circuit's switching operations in response to DC link voltage variations. When voltage rises above the reference level, the control unit modifies switching patterns to reduce voltage, thereby maintaining output stability while allowing controlled voltage variation that protects the capacitor from excessive stress
Solution Approach 2:
The control unit continuously monitors DC link voltage and uses this feedback to adjust inverter switching operations. This closed-loop control maintains output voltage stability by compensating for DC link voltage variations, while the controlled nature of these variations prevents excessive capacitor stress
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 reduces energy loss, minimizes component size and cost, and prevents overvoltage damage by actively managing DC link voltage during switching operations, ensuring reliable operation and extended component lifespan.
Implementation Method 1
a capacitor (31) connected in parallel to each of the converter circuit (20) and the inverter circuit (40) between the converter circuit (20) and the inverter circuit (40), the capacitor (31) allowing variation of an output voltage from the converter circuit (20), the capacitor (31) absorbing variation of an output voltage from the inverter circuit (40) due to a switching operation
Implementation Method 2
an overvoltage protection circuit (50) including a resistor (51) and a semiconductor element (52) connected in series to each other, the overvoltage protection circuit (50) being connected in parallel to the capacitor (31), the overvoltage protection circuit (50) being configured to protect the inverter circuit (40) from an overvoltage applied to the inverter circuit (40)
Data Source
AI summary
A converter circuit converts AC electric power into DC power. An inverter circuit converts the DC power into AC power. A capacitor is connected in parallel to each of the converter circuit and the inverter circuit between these circuits. The capacitor allows variation of an output voltage from the converter circuit, and absorbs variation of an output voltage from the inverter circuit due to a switching operation. An overvoltage protection circuit includes a resistor and a semiconductor element connected in series to each other. The overvoltage protection circuit is connected in parallel to the capacitor to protect the inverter circuit from an overvoltage. First and second control units respectively control the inverter circuit and the overvoltage protection circuit.