SiC MOSFET Two-Stage Inverter for Electric Machines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power conversion systems face inefficiencies and complexity when converting high-voltage AC to DC or vice versa, particularly in modern electrical machines and grids, where high power levels lead to increased losses and inefficiencies.
Innovation Solution
A two-stage inverter system utilizing silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) in a two-level configuration, with an independent shoot-through protection circuit and a low inductance DC bus design to minimize voltage overshoots and ensure reliable operation at high frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional silicon-based power semiconductors are used for high-voltage power conversion, then the system can operate at high voltage levels, but switching losses increase and efficiency decreases at high frequencies
Solution Approach 1:
The patent changes the material parameter from conventional silicon to silicon carbide (SiC), which fundamentally alters the semiconductor's electrical characteristics. SiC enables operation at higher switching frequencies with reduced switching losses due to its wider bandgap and higher critical electric field, directly resolving the contradiction between energy loss and productivity
Solution Approach 2:
The patent employs silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) that combine SiC's superior electrical properties with MOSFET's voltage-controlled switching mechanism. This composite approach leverages both materials' strengths to achieve low loss and high frequency operation simultaneously
2Power
If high-voltage DC bus operation is implemented, then power throughput increases, but voltage overshoots and electrical stress increase
Solution Approach 1:
The patent places capacitors in parallel with the SiC MOSFETs before voltage overshoots can occur. These capacitors act as energy buffers that absorb voltage spikes and reduce electrical stress on the semiconductor devices, enabling safe high-voltage operation
Solution Approach 2:
The patent introduces an independent shoot-through protection circuit that includes a current sensor, comparator, and latch. This intermediary protection system monitors current flow and interrupts gating signals to prevent shoot-through conditions, mediating between the high-power operation and safe device operation
3Reliability
If shoot-through protection circuits are added to prevent MOSFET damage, then reliability improves, but system complexity increases
Solution Approach 1:
The patent divides the protection function into separate, modular components: a current sensor (current transformer), a comparator, and a latch. This segmentation allows each component to perform a specific function independently, making the overall protection system more manageable and less complex than integrated solutions
4Stability of the object's composition
If DC bus inductance is reduced to minimize voltage overshoots, then voltage stability improves, but physical space for bus bar arrangement becomes constrained
Solution Approach 1:
The patent arranges the DC bus bar structure where conducting plates are positioned and shaped to nest together, minimizing the distance between conducting paths. This nested arrangement reduces the loop area and consequently the inductance while fitting within compact physical spaces
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 system achieves high efficiency and reliability in power conversion with reduced system complexity, enabling high power throughput and minimizing voltage overshoots, while the independent shoot-through protection circuit ensures safe operation even in case of gate driver failures.
Implementation Method 1
using two or more SiC MOSFETs in series with each MOSFET having a gate terminal for triggering a state switch between an on (conducting) and off (non-conducting) state of the MOSFET
Implementation Method 2
a current sensor, such as a current transformer that is inductively coupled to at least one capacitor in parallel with the SiC MOSFETs
Implementation Method 3
the series SiC MOSFETs are connected across a DC bus and in parallel with one or more capacitors
Data Source
AI summary
The present disclosure involves a two stage inverter, a system for electrical power conversation, and a method of converting electrical power using silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). One example implementation includes using two or more SiC MOSFETs in series with each MOSFET having a gate terminal for triggering a state switch between an on (conducting) and off (non-conducting) state of the MOSFET. An AC terminal is connected between the series SiC MOSFETS, and the series SiC MOSFETs are connected across a DC bus and in parallel with one or more capacitors.