DC Isolated-Parallel UPS Module Fault Current Management

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Solution Overview

Problem

Existing UPS systems face inefficiencies and high costs due to the need for costly high-amperage equipment and high fault current levels when powering large data centers with DC power, as well as inefficiencies in multi-module configurations that often operate in suboptimal modes, failing to realize efficiency gains from DC power distribution.

Innovation Solution

A Direct Current (DC) Isolated-Parallel (Iso-Parallel) UPS system that uses static rectifiers and inverters to convert AC power to DC, with bidirectional converters connecting DC busses to a common AC Iso-Parallel Bus via chokes, allowing power equalization and fault isolation among modules, and operating at higher frequencies to reduce choke size and amperage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If DC power distribution is used to computer loads, then power utilization efficiency is improved, but fault current levels become dangerously high

Engineering Contradiction:

Improvepower utilization efficiencyVSAvoidfault current levels

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The system divides the DC power distribution into multiple isolated parallel modules, each with its own DC bus. Fault isolation barriers prevent fault currents from propagating across the entire system, containing high fault currents to individual modules while maintaining efficient DC power distribution to computer loads.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

AC coupling transformers are introduced as intermediary devices between DC buses. These transformers provide galvanic isolation while allowing power transfer, thereby blocking dangerous DC fault currents from spreading between modules while maintaining the efficiency benefits of DC power distribution.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If multi-module UPS configurations are used to accommodate large critical loads, then load capacity is improved, but electrical efficiency decreases due to equipment operating at low capacity percentages

Engineering Contradiction:

Improveload capacityVSAvoidelectrical efficiency

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

Multiple UPS modules are merged into a single isolated-parallel system where DC buses are AC-coupled through transformers. This allows modules to operate in parallel with load sharing capabilities, enabling each module to operate at optimal capacity levels while collectively handling large critical loads, thereby maintaining high electrical efficiency.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The system implements dynamic load sharing among modules through AC coupling, allowing modules to adjust their power contribution based on actual load demands. This dynamic operation prevents equipment from operating at inefficiently low capacity percentages while maintaining the ability to handle large total loads.

Inventive Principle:

Principle #15Dynamics

3Reliability

If static bypass switches are used in prior iso-parallel configurations, then fault isolation is achieved, but operating efficiency is reduced due to rectifier and inverter paths being engaged

Engineering Contradiction:

Improvefault isolationVSAvoidoperating efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

AC coupling transformers serve as intermediary devices that enable direct DC-to-DC power transfer between modules without requiring rectifier and inverter conversion. This eliminates the efficiency losses associated with engaged rectifier and inverter paths while maintaining fault isolation through the transformer's galvanic isolation properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration enhances efficiency by equalizing power demand among modules, reducing equipment costs, and achieving higher efficiency in power distribution by using DC power directly, while maintaining fault isolation and reducing the size and cost of inductive components.

Implementation Method 1

Each DC bus is connected to the common IP Bus through a bidirectional converter and an inductive reactor, referred to as an IP choke

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Implementation Method 2

Methodology Applied

Scientific EffectElectromagnetic Conversion: Electromagnetic Induction

Data Source

PatentUS10135293B2Direct current isolated-parallel uninterruptible power supply system

Publication Date: 2018.11.20 MOSMAN MICHAEL J

AI summary

A Direct Current (DC) Isolated-Parallel (Iso-Parallel or IP) Uninterruptible Power Supply (UPS) system and method for converting incoming AC power to DC power using several modules which are paralleled at their outputs yet fault isolated from each other. The DCIP UPS has two or more modules connected to a common IP Bus which operates at AC voltage and is disposed between a facility electrical distribution system and the facility's critical electrical loads which operate at DC voltage. The electrical distribution system receives power from a local utility, or from a standby power source when utility power is unavailable, and delivers AC power to the DCIP UPS input. The DCIP UPS converts the power to DC and delivers it to critical electrical loads associated with computer equipment or other devices using DC power. The individual modules that comprise the DCIP UPS share the DC loads equally, yet remain isolated such that a fault within one module or its load will not disrupt the operation or loads of the remaining modules.