Bidirectional Buck-Boost Converter Voltage Centering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bidirectional DC-DC converters connected in parallel to a common battery require additional connections and cabling for midpoint voltage centering, leading to increased complexity and cost due to circulating currents and the need for active centering or balancing circuitry.
Innovation Solution
A bidirectional buck-boost converter design with a control circuit that connects multiple converters in parallel without a midpoint connection, using a single boost switching element to center battery voltage between DC link voltage automatically in boost mode, eliminating the need for active voltage centering and reducing circulating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional connections and cabling are added for midpoint voltage centering, then voltage centering is achieved, but device complexity and cost increase
Solution Approach 1:
The patent removes the midpoint connection requirement from the battery configuration. By connecting converters in parallel without tapping into the battery midpoint, the design eliminates the associated cabling and connection complexity while maintaining voltage centering functionality through the capacitor coupling arrangement.
Solution Approach 2:
The capacitor coupling between converters serves multiple functions: it provides voltage centering, enables parallel operation without midpoint connections, and reduces circulating currents. This multi-functional approach replaces what would otherwise require separate dedicated centering circuitry and additional connections.
2Reliability
If active centering or balancing circuitry is added, then voltage centering is maintained, but device complexity and cost increase
Solution Approach 1:
The capacitor coupling arrangement enables the converter system to self-center the voltage automatically through its inherent operational characteristics. The control circuitry manages switching operations, and the voltage centering emerges naturally from the coupled capacitor configuration without requiring separate active centering control mechanisms.
3Device complexity
If converters are connected without midpoint connection, then device complexity is reduced, but voltage centering becomes difficult to maintain
Solution Approach 1:
Coupling capacitors are introduced as intermediary elements between the parallel-connected converters. These capacitors mediate the voltage relationship, enabling automatic voltage centering to occur through the capacitive coupling mechanism without requiring direct midpoint connections to the battery.
4Power
If multiple converters are connected in parallel to common battery, then power capacity is increased, but circulating currents increase
Solution Approach 1:
The coupling capacitors act as intermediary elements that decouple the converters from direct interaction with each other and the battery midpoint. This intermediary arrangement prevents circulating currents by eliminating the closed-loop path that would otherwise exist between parallel-connected converters sharing a common battery.
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 solution simplifies control and reduces complexity by automatically centering battery voltage without additional circuitry, ensuring minimal current circulation between parallel converters, thus lowering costs and enhancing operational efficiency.
Implementation Method 1
The converter includes a first set of capacitors and a second set of capacitors having positive, negative, and mid terminals... The positive and negative terminals of the first set of capacitors are configured to operably connect to positive and negative rails, respectively, of a first source... The bidirectional DC-DC converter transforms electrical energy between DC link and battery through electromagnetic induction using switching elements and inductors
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A bidirectional buck-boost DC-DC converter is particularly well suited for applications where multiple bidirectional buck-boost DC-DC converters are connected in parallel to a common battery. Multiple bidirectional DC-DC converters, as disclosed, may be connected in parallel to a common battery and, at least in boost mode, substantially no current circulates between the parallel connected bidirectional DC-DC converters.