Double-Boost DC/DC Converter Switching for DC-Link Voltage Balancing
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Solution Overview
Problem
Existing double-boost DC/DC converters face challenges in voltage balancing, particularly in split DC-link configurations, due to limited power capability of the 4th leg converter, often exacerbated by DC offset and even harmonics in load current, leading to undesired common mode voltages and inefficiencies.
Innovation Solution
A double-boost DC/DC converter design that switches inner switches in a specific sequence (S1, S2, S3, S4) to balance voltage without generating undesired common mode voltages, using transistors and anti-parallel diodes, with a controller managing these switches to operate in both converter and DC source modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated 4th leg buck-boost converter is used for voltage balancing, then DC-link voltage balancing is achieved, but the power capability is limited and common mode voltages are generated
Solution Approach 1:
The patent merges the voltage balancing function with the existing dual-boost converter by utilizing its two operating modes (converter mode and DC source mode) to perform both power conversion and voltage balancing tasks, eliminating the need for a separate 4th leg converter and thereby removing the power capability limitation
Solution Approach 2:
The dual-boost converter is designed to perform multiple functions: it operates as a converter in normal mode and as a DC source in boosting mode, with both modes contributing to voltage balancing. This multi-functionality allows the system to handle both standard power conversion and voltage balancing without requiring additional dedicated hardware
2Reliability
If a dedicated 4th leg converter is used for voltage balancing, then DC-link voltage balancing is achieved, but undesired common mode voltages are generated on DC source terminals
Solution Approach 1:
The patent converts the potential harmful common mode voltages into beneficial balancing action by carefully controlling the switching sequences. The switching patterns are designed so that voltage imbalances are corrected through the difference in volt-seconds applied to the inductors, while the common mode voltage components are eliminated through synchronized switching of the upper and lower switches
3Reliability
If a dedicated 4th leg converter is used for voltage balancing, then DC-link voltage balancing is achieved, but hardware complexity and costs increase
Solution Approach 1:
The dual-boost converter is designed to perform multiple functions: it operates as a converter in normal mode and as a DC source in boosting mode, with both modes contributing to voltage balancing. This multi-functionality allows the system to handle both standard power conversion and voltage balancing without requiring additional dedicated hardware
Solution Approach 2:
The system uses its own existing components (the two boost converters with their switches, inductors, and capacitors) to perform voltage balancing without requiring external dedicated balancing circuitry. The converters self-regulate the DC-link voltages by adjusting their operating modes and switching patterns
Data Source
Figure 1
Figure 2a~2e
Figure 3a~3e
AI summary
Voltage balancing circuit (100) for a double-boost DC/DC converter comprising a split DC-link (101, 102) with midpoint (103); outer directional devices (111, 114) and inner switches (112, 113) parallel-connected to the DC-link (101, 102), wherein the outer directional devices are connected to capacitors of the split DC-link and to the inner switches and the inner switches are connected to each other at a midpoint; and DC source (140) terminal to which a DC source is connectable in parallel over inductances to the inner switches; wherein an inductance is connected to the midpoint of the DC link and to the midpoint of the inner switches.