Bi-Directional MV-LV Converter Topology With Galvanic Isolation
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Solution Overview
Problem
Existing bi-directional power flow systems for applications involving megawatt electrical power, such as renewables, storage, and datacenters, face challenges in achieving high efficiency and low costs while maintaining a compact size and cost-effective galvanic insulation.
Innovation Solution
A bi-directional medium voltage converter topology utilizing an n-pulse line-interphase-transformer (LIT), bi-directional MV converters, a multi-stage DC/DC converter, and low voltage DC/DC converter, connected via medium frequency transformers (MFTs) for galvanic insulation, allowing efficient power flow in both directions with reduced size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MV-to-LV AC/DC converter with galvanic insulation is used, then safety and electrical isolation are ensured, but the system size, cost, and footprint increase
Solution Approach 1:
The patent extracts the galvanic insulation function from the main converter structure by introducing a separate isolation converter stage. This dedicated isolation stage handles only the galvanic isolation requirement, allowing the main converter to be optimized for power conversion efficiency and reduced size. The isolation converter uses a transformer to provide galvanic insulation between MV and LV sides, while the main converter focuses on efficient power conversion.
Solution Approach 2:
The converter system is segmented into multiple functional stages: a rectifier stage, a DC-DC converter stage with galvanic isolation, and additional conversion stages. This segmentation allows each stage to be optimized for its specific function, reducing the overall size and cost while maintaining galvanic insulation requirements.
2Adaptability or versatility
If bi-directional power flow capability is added to achieve flexibility in renewable energy applications, then system versatility improves, but device complexity and cost increase
Solution Approach 1:
The patent designs the converter system with universal components that can operate in both forward and reverse power flow directions. The DC-DC converter stage and isolation transformer are configured to handle power flow in either direction, enabling the system to function as both a rectifier (AC to DC) and an inverter (DC to AC), or to bidirectionally convert between MV and LV DC. This multi-functionality is achieved through symmetric circuit topologies and control strategies that work equally well in both directions.
Solution Approach 2:
The converter employs dynamic control mechanisms that can adapt the operating mode and power flow direction based on system requirements. The control system dynamically adjusts switching patterns, duty cycles, and operational parameters to optimize performance for the current operating condition, whether charging, discharging, grid connection, or islanded operation.
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 topology achieves high efficiency and cost-effectiveness with a small footprint, suitable for various applications including renewables, energy storage, and datacenters, while minimizing grid side harmonics and filtering efforts.
Implementation Method 1
a bi-directional low voltage (LV) DC/DC converter; wherein the multi-stage DC/DC converter and the LV DC/DC converter are connected to each other galvanically insulated
Data Source
AI summary
A bi-directional medium voltage converter topology includes an n-pulse line-interphase-transformer, LIT; a plurality of bi-directional medium voltage, MV converters connected to the LIT on an AC side thereof and connected in parallel on a DC side thereof; a bi-directional multi-stage DC/DC converter connected to the plurality of bi-directional MV converters; and a bi-directional low voltage, LV, DC/DC converter; wherein the multi-stage DC/DC converter and the LV DC/DC converter are connected to each other galvanically insulated.