Bidirectional Buck-Boost Converter for Battery Balancer
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Solution Overview
Problem
Existing uninterruptable power supply systems for train applications face challenges with complex and costly solutions to prevent uncontrolled circulating currents and electromagnetic interference (EMI) due to the use of batteries connected to unstable potentials, particularly in systems with multiple power supply modules.
Innovation Solution
A power supply system with a bidirectional buck/boost converter connected to a neutral point of the power supply module, allowing for simplified charging and discharging of a rechargeable battery, and an additional balancing converter for load balancing between DC links, eliminating uncontrolled currents and EMI issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two wire battery is used connected to an unstable potential, then the number of converters and protection components is reduced, but the control becomes more difficult and additional impedances and control circuitry are required to limit circulating currents
Solution Approach 1:
The patent introduces a neutral point as an intermediary reference potential for the battery connection. This neutral point acts as a mediator between the battery and the DC link, providing a stable reference that eliminates the need for additional control circuitry and impedances while maintaining simple two-wire battery connection.
Solution Approach 2:
The patent creates an equipotential neutral point in the DC link that serves as a stable reference potential. By establishing this equipotential point, the battery operates with a stable voltage reference, eliminating circulating current issues without requiring additional control components or increasing system complexity.
2Use of energy by moving object
If a battery is used for several power supply modules, then auxiliary energy is provided, but the battery may introduce uncontrolled circulating current between the power supply modules
Solution Approach 1:
The neutral point serves as an intermediary that isolates the battery from direct connection to multiple DC links. This mediator prevents direct current paths between parallel power supply modules, eliminating uncontrolled circulating currents while allowing the battery to provide auxiliary energy to multiple modules through the shared neutral point.
Solution Approach 2:
The patent extracts the battery from direct connection to the DC links and reconnects it through the neutral point. This extraction removes the battery-induced circulating current problem while preserving the auxiliary energy function, as the neutral point provides a common reference without creating direct current paths between modules.
3Ease of operation
If a three wire battery is used with midpoint input, then the system is simple to control and inherently stable, but higher costs are incurred due to cabling, protection and two DC-DC converters
Solution Approach 1:
The patent merges the neutral point function with the battery connection point. Instead of requiring a separate three-wire battery configuration with dedicated midpoint connection, the neutral point of the DC link serves dual purposes: as the reference potential for the inverter and as the connection point for the battery, eliminating the need for additional cabling and converters.
Solution Approach 2:
The neutral point is designed to serve multiple functions simultaneously: it acts as the reference potential for the split DC link, the connection point for the battery, and the common reference for all power supply modules. This multi-functionality eliminates the need for separate dedicated battery connection infrastructure, reducing system complexity and cost.
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 proposed solution provides a cost-effective, easy-to-control uninterruptable power supply system with reduced cabling and components, preventing uncontrolled circulating currents and EMI, while maintaining stable operation and scalability.
Implementation Method 1
A power supply system with a bidirectional buck/boost converter connected to a neutral point of the power supply module, allowing for simplified charging and discharging of a rechargeable battery
Data Source
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AI summary
A power supply system (10) for supplying a load (18) with electric energy from an electrical network (14) comprises at least one power supply module (20). The power supply module (20) comprises a DC link (24) to be supplied from the electrical network (14); and an inverter (26) connected to the DC link (24) and adapted for converting a DC voltage from the DC link (24) into an AC voltage to be supplied to the load (18). The power supply system (10) comprises an electric energy storage (30) to be charged by the DC link (24) and for supplying the DC link (24) with electric energy, when the electrical network (14) has a power failure, the electric energy storage (30) connected with one input (36) to a neutral point (N) of the power supply module (20). The power supply module (20) comprises a bidirectional buck/boost converter (40) connected to a positive potential (DC+) or negative potential (DC-) of the DC link (24), to the neutral point (N) and to another input (34) of the electric energy storage (30).