Multiphase Multilevel Converter With Stacked Half-Bridges
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Solution Overview
Problem
Existing multi-level multi-phase converters face challenges in meeting high power requirements while minimizing component count, filter size, and operational complexity, particularly for low-voltage applications, and require complex capacitor voltage sensing circuits.
Innovation Solution
A multi-level and multi-phase converter design with a transformer having N phases, primary and secondary switch/rectifier legs with stacked half-bridges connected in series, and a reduced number of DC link capacitors and voltage sensing circuits, utilizing a phase shift in switching signals and transformer interconnection to achieve efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high number of full bridge inverter cells with separate transformers are used to meet high power requirements, then the power output is improved, but the number of components increases and the converter becomes unsuitable for low-voltage applications
Solution Approach 1:
The converter is divided into multiple phases (N phases) with each phase having its own switch leg and half-bridge circuits. This segmentation allows the high power requirement to be distributed across multiple parallel phases, reducing the burden on individual components while maintaining high overall power output capability.
Solution Approach 2:
Multiple phases are combined in parallel configuration where the secondary rectifier legs of different phases are connected in parallel. This merging approach allows the converter to achieve high power output through parallel current contribution from multiple phases while using a single shared transformer and reduced number of DC link capacitors compared to separate full-bridge configurations.
2Reliability
If capacitor voltage sensing circuits are added to maintain DC link capacitor voltages, then the reliability is improved, but the number of components and costs increase
Solution Approach 1:
The voltage sensing circuits serve multiple functions: they monitor DC link capacitor voltages for reliability purposes, provide feedback for phase shift control to balance capacitor voltages, and enable the converter to operate with reduced capacitor count. This multi-functionality reduces the need for separate dedicated sensing circuits for each capacitor.
Solution Approach 2:
The voltage sensing circuits provide feedback signals that are used to adjust the phase shift between primary switch legs. This feedback mechanism automatically balances the DC link capacitor voltages during operation, maintaining reliability without requiring separate control circuits for each capacitor.
3Power
If a multi-level topology with stacked half-bridges is used to achieve high power output, then the power capability is improved, but the switching frequency range becomes narrower
Solution Approach 1:
The converter employs dynamic phase shift control between primary switch legs based on load conditions. The phase shift angle is adjusted dynamically to optimize the voltage stress on switches and maintain efficient operation across a wide range of power outputs, effectively compensating for the narrower inherent switching frequency range of multi-level topologies.
Solution Approach 2:
The converter changes operating parameters including phase shift angle and switching frequency to optimize performance. By adjusting the phase shift between primary switch legs and modifying switching frequencies within the available range, the converter maintains high power output capability while adapting to different load requirements.
4Stress or pressure
If multiple stacked full bridges are used for very high-voltage applications, then the voltage capability is improved, but the converter becomes inefficient and economically unsuitable for low-voltage applications
Solution Approach 1:
Instead of using the full stacked full-bridge configuration with maximum voltage stress on each component, the invention uses a partial approach with N-phase parallel configuration where each phase operates at optimized voltage levels. This partial action approach achieves the required voltage capability through parallel phase contribution while maintaining lower individual component stress, resulting in improved efficiency and economic suitability for low-voltage applications.
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 converter achieves high power output with reduced components, lower ripple currents, smaller size, and simplified control, suitable for low-voltage applications with lower losses and easier manufacturing.
Implementation Method 1
a transformer with a plurality N of phases. A primary side circuit of the converter is connected to a primary side of the transformer
Implementation Method 2
each of the primary switch legs comprises a plurality of stacked primary half-bridges connected in series with one another
Implementation Method 3
the secondary rectifier legs are connected in parallel to one another
Implementation Method 4
utilizing a phase shift in switching signals and transformer interconnection to achieve efficient operation
Data Source
Figure 1
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AI summary
The invention concerns a multi-level multi-phase converter (1), comprising: a transformer (2) with a plurality N of phases (12); a primary side circuit (5) connected to a primary side (3) of the transformer (2), the primary side circuit (5) comprising a plurality of primary switch legs (6) with primary switches (27), wherein a number of primary switch legs (6) of the primary side circuit (5) corresponds to a number N of phases (12) of the transformer (2); and a secondary side circuit (7) connected to a secondary side (4) of the transformer (2), the secondary side circuit (7) comprising a plurality of secondary rectifier legs (8) with secondary rectifier elements (9), wherein the secondary rectifier legs (8) are connected in parallel to one another; wherein each of the primary switch legs (6) comprises a plurality of stacked primary half-bridges (6.1, 6.2) connected in series with one another; the primary switch legs (6) are connected in parallel to one another; and wherein one phase (12) of the primary side (3) of the transformer (2) is connected between two primary half-bridges (6.1, 6.2) in series with one another. The invention also concerns a control method for operating the multi-level multi-phase converter (1).