Modular Power Conversion with Shared Bus for DC Link Balancing
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Solution Overview
Problem
The existing power conversion systems for electric vehicle charging stations face inefficiencies due to bulky line frequency transformers and the DC link imbalance caused by power imbalances across independent charging ports in solid state transformer (SST) architectures, leading to reduced system efficiency and increased costs.
Innovation Solution
A power conversion system comprising multiple power modules with bidirectional power flow through a shared power bus, where each module has a first port for external connection, a second port for independent power input/output, and a third port connected in parallel to form a power bus, allowing for power regulation between modules to balance input/output power and address DC link voltage imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common DC bus architecture with multiple isolated DC-DC chargers is used, then galvanic isolation among vehicles is achieved, but system efficiency decreases due to multi-stage conversion circuits
Solution Approach 1:
The system divides the charging station into multiple independent power modules, each capable of autonomous operation. Each module includes its own DC-DC converter and control circuitry, allowing them to function independently while sharing the common DC bus. This segmentation enables each module to operate at optimal efficiency points while maintaining galvanic isolation through individual isolated DC-DC converters.
Solution Approach 2:
The power modules are designed with multi-functionality to serve multiple purposes: they can independently charge vehicles, share power among themselves through the common DC bus, and maintain voltage balance across the system. The bidirectional power flow capability allows each module to act as both a power consumer and a power source, reducing the need for separate isolation circuits for each charging port.
2Adaptability or versatility
If multiple isolated DC-DC chargers are connected to a DC bus, then multiple charging ports are provided, but device complexity increases
Solution Approach 1:
The charging station is divided into modular power units that can be independently configured and maintained. Each module contains complete charging functionality including isolation conversion, allowing for simplified individual module design while achieving complex system capabilities through modular assembly.
Solution Approach 2:
Multiple power modules share common infrastructure including the DC bus, control system, and physical housing. This merging of common resources reduces overall system complexity compared to having completely separate charging systems for each port, while still maintaining the electrical isolation required for safety.
3Reliability
If line frequency transformer is used for medium-voltage isolation, then isolation is achieved, but weight and volume increase
Solution Approach 1:
The patent replaces traditional line-frequency mechanical transformers with high-frequency isolated DC-DC conversion circuits. This substitution leverages electronic switching at higher frequencies to achieve the same isolation function with significantly reduced weight and volume, as high-frequency transformers require much smaller magnetic cores and windings.
Solution Approach 2:
The system changes the operating frequency parameter from line frequency (50/60 Hz) to high frequency (kHz range) for the isolation transformation. This parameter change enables the use of smaller, lighter magnetic components while maintaining effective galvanic isolation, directly addressing the weight and volume issues with traditional transformers.
Data Source
AI summary
Embodiments of the present disclosure provide a power conversion system and a control method. The power conversion system includes multiple power modules, and each power module includes a first port, a second port, and a third port, where the first port of each power module is connected to an external device, second ports of the power modules are independent of each other and used as independent ports to output power, third ports of the power modules are connected in parallel to form a power bus and power flow of the third port of each power module is bidirectional.