Inverter Overvoltage Protection With Reduced DC-Link Capacitance
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Solution Overview
Problem
Conventional power conversion devices face challenges in efficiently managing overvoltage and reducing capacitance while providing reliable power to loads, particularly in scenarios involving magnetic energy storage and switching operations, which can lead to component stress and increased costs.
Innovation Solution
A power conversion device incorporating a converter circuit, an inverter circuit, a capacitor for voltage variation, and an overvoltage protection circuit with a resistor and semiconductor element, controlled by a dual control unit system to manage overvoltage and minimize capacitance, utilizing wide-bandgap semiconductors for efficient energy handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power conversion device uses a braking circuit with a braking resistor to manage overvoltage, then overvoltage protection is provided, but the device size, cost, and power consumption increase
Solution Approach 1:
The patent extracts the overvoltage protection function from the conventional braking circuit and relocates it to the inverter circuit itself. By using the inverter's switching elements to redirect and dissipate regenerative energy, the separate braking resistor and braking circuit are eliminated, reducing device size and cost while maintaining overvoltage protection capability
Solution Approach 2:
The inverter circuit is given multiple functions: it not only performs its primary function of converting DC to AC power for the load, but also serves as the overvoltage protection mechanism by redirecting regenerative energy during braking operations. This multi-functionality eliminates the need for separate protection components
2Stability of the object's composition
If a power conversion device uses a large capacitor to smooth voltage variations, then voltage stability is improved, but the device size and cost increase
Solution Approach 1:
The patent changes the operational parameters of the capacitor by dynamically controlling the inverter circuit's switching timing and duty cycle. Instead of relying on a large capacitor to passively smooth voltage, the system actively manages voltage variations through precise control of energy flow, allowing the use of a smaller capacitor while maintaining voltage stability
Solution Approach 2:
The patent replaces the passive mechanical approach of using a large capacitor for voltage smoothing with an active electronic control system. The inverter circuit's switching elements and control unit actively regulate voltage by controlling energy redistribution, substituting the need for large passive energy storage components
3Ease of manufacture
If a power conversion device uses conventional semiconductors for switching operations, then the device is easier to manufacture, but heat dissipation becomes problematic and efficiency decreases
Solution Approach 1:
The patent employs composite material technology by integrating wide-bandgap semiconductor materials (such as SiC or GaN) into the inverter circuit's switching elements. These advanced materials combine the electrical performance benefits of wide-bandgap semiconductors with optimized structural design, enabling superior heat dissipation and efficiency while remaining manufacturable through established semiconductor fabrication processes
4Adaptability or versatility
If a power conversion device allows full variation of converter output voltage, then adaptability to different loads is improved, but overvoltage stress on the inverter circuit increases
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors the converter circuit's output voltage and dynamically adjusts the inverter circuit's switching parameters. This feedback loop enables the system to adapt to different load conditions while automatically preventing overvoltage stress by redistributing excess energy through the inverter, thus protecting components while maintaining load adaptability
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
The solution effectively reduces capacitance, minimizes power consumption, and prevents component stress, enabling smaller, cost-effective devices with enhanced heat dissipation and reliability in managing overvoltage conditions.
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.