MVDC Link-Powered Battery Charger With Converterless Connection
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Solution Overview
Problem
Current battery charging infrastructure, particularly for electric vehicles, faces inefficiencies and limitations in power transfer capabilities and feeder system losses, necessitating improved medium voltage direct current (MVDC) link-powered solutions for enhanced charging performance.
Innovation Solution
The implementation of MVDC link-powered battery chargers that utilize bi-directional AC/DC converters and electronic controllers to manage power flow and voltage control, allowing direct power supply from an MVDC link to battery chargers without intermediate converters, thereby optimizing charging processes and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If AC/DC converters are used in parallel with normally open switches for power transfer, then power transfer capability is enhanced, but device complexity increases
Solution Approach 1:
The system divides power transfer functionality into two parallel paths: one through AC/DC converters for controlled power transfer, and another through normally open switches for direct power transfer. This segmentation allows the system to handle different power transfer scenarios through appropriate pathways, enhancing overall capability while managing complexity through functional division.
Solution Approach 2:
The MVDC link is designed to serve multiple functions: it enables power transfer between feeders through AC/DC converters, allows direct power transfer through switches, and provides a pathway for battery charging. This multi-functionality consolidates what would otherwise require separate systems into a single unified infrastructure, enhancing power capability without proportionally increasing complexity.
2Loss of energy
If AC/DC converters are coupled via DC cabling for power transfer, then feeder system power losses are reduced, but device complexity increases
Solution Approach 1:
DC cabling serves as an intermediary medium between AC/DC converters, enabling direct DC power transfer without requiring additional AC/AC conversion stages. This intermediary DC link reduces conversion losses and improves efficiency, while the cabling itself acts as the simplifying element that connects converters directly.
Solution Approach 2:
The system extracts the AC conversion function from the power transfer path by using DC cabling to directly connect AC/DC converters. This removes unnecessary AC/AC conversion stages and intermediate equipment, reducing device complexity while maintaining the efficiency benefits of DC power transfer.
3Productivity
If MVDC link voltage is increased to provide battery charging current, then charging speed is improved, but voltage control complexity increases
Solution Approach 1:
The MVDC link voltage is designed to be dynamically adjustable rather than fixed. The voltage can be increased when battery charging is required to improve charging speed, and adjusted to other levels when power transfer between feeders is the primary function. This dynamic capability allows the system to optimize for different operational modes without requiring separate fixed-voltage systems.
Solution Approach 2:
The system incorporates feedback control mechanisms that monitor battery charging requirements and automatically adjust the MVDC link voltage to appropriate levels. This feedback control simplifies the overall complexity by automating voltage adjustments based on real-time conditions, eliminating the need for manual intervention or overly complex control systems.
Data Source
AI summary
One embodiment is a system comprising a medium voltage direct current (MVDC) link electrically coupling a first AC-DC converter and a second AC-DC converter. The first AC-DC converter is electrically coupled with a first alternating current (AC) feeder. The second AC-DC converter electrically coupled with a second AC feeder. A battery charger electrically coupled with the MVDC link via a converterless connection. A first electronic controller is operatively coupled with the first AC-DC converter. A second electronic controller is operatively coupled with the second AC-DC converter. During operation of the battery charger to charge a battery the first electronic controller is configured to control power flow between the first AC feeder and the second AC feeder and the second electronic controller is configured to control the voltage of the MVDC link.