Multi-Level Power Converter Topology for Capacitor Voltage Balance
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Solution Overview
Problem
Current multi-level power converters face challenges in improving performance and reliability due to voltage imbalances among capacitors, which can lead to damage of switching semiconductor devices and limit the number of voltage levels they can generate.
Innovation Solution
A multi-level power converter design that includes a first and second power converting unit with phase-shifted voltage levels, a coupling inductor with windings of the same number of turns, and an inductive filtering unit, allowing for the generation of desired voltage levels using fewer capacitors and reducing the risk of voltage imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of capacitors is increased to generate more voltage levels, then the number of voltage levels increases, but the risk of voltage imbalance among capacitors increases and reliability deteriorates
Solution Approach 1:
The patent merges two H-bridge circuits into a single unified structure with shared capacitors and coupling inductors. The first and second H-bridge circuits share the same capacitor bank (C1, C2) and are coupled through coupled inductors (L1, L2), creating an integrated five-level converter that generates multiple voltage levels without requiring separate capacitor sets for each bridge, thereby reducing voltage imbalance risk.
Solution Approach 2:
The capacitors C1 and C2 serve multiple functions simultaneously: they provide voltage levels for both the first and second H-bridge circuits, enable five-level output generation, and maintain voltage balance across the entire system. This multi-functional design eliminates the need for dedicated capacitors for each bridge, reducing the overall capacitor count and improving reliability.
2Adaptability or versatility
If more capacitors are used to provide multiple voltage levels, then the voltage levels can be generated, but the complexity of the circuit increases
Solution Approach 1:
The patent combines two H-bridge circuits into a unified structure where capacitors, inductors, and switching devices are shared between bridges. The coupled inductors L1 and L2 with equal turns are wound on the same magnetic core, creating a compact integrated structure that reduces overall circuit complexity while maintaining five-level voltage generation capability.
Solution Approach 2:
The first and second H-bridge circuits are nested within a unified converter structure, with their switching devices and capacitors interlaced and shared. The coupled inductors are nested on the same magnetic core, creating a compact nested arrangement that reduces spatial complexity and component count while achieving multiple voltage levels.
3Device complexity
If the number of capacitors is reduced to simplify the circuit, then the circuit complexity decreases, but the ability to generate multiple voltage levels is compromised
Solution Approach 1:
The patent changes the topological parameters of the converter by introducing coupled inductors with equal turns ratio (n1:n2 = 1:1) and configuring switching devices in specific combinations. By changing the coupling parameter k between inductors L1 and L2, the system can maintain five-level voltage generation with fewer capacitors, as the inductive coupling compensates for the reduced capacitive diversity.
Solution Approach 2:
The patent creates a composite converter structure combining resistive elements (switching devices), capacitive elements (shared capacitors C1, C2), and inductive elements (coupled inductors L1, L2) in a unified topology. This composite structure leverages the synergistic interaction between different energy storage elements to generate five voltage levels with reduced component count, particularly using the inductive coupling to create additional voltage levels that would otherwise require more capacitors.
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 design enhances the performance and reliability of multi-level power converters by generating the required number of voltage levels while minimizing capacitor risk and extending the service life of semiconductor devices, allowing for broader usage scenarios.
Implementation Method 1
a coupling inductor including first and second windings with the same number of turns, the first winding includes a first end coupled to the first AC terminal and a second end, the second winding includes a third end coupled to the second AC terminal and a fourth end
Implementation Method 2
an inductive filtering unit arranged between the AC port and the second and fourth ends of the first and second windings
Data Source
AI summary
A multi-level power convertor is provided. The multi-level power convertor includes a DC port, an AC port, a first power converting unit coupled to the DC port and including a first AC terminal adapted to provide a first plurality of voltage levels, a second power converting unit coupled to the DC port and including a second AC terminal adapted to provide a second plurality of voltage levels of the same number as the first plurality of voltage levels, a coupling inductor including first and second windings with the same number of turns, and an inductive filtering unit arranged between the AC port and the second and fourth ends of the first and second windings.