Server Rack Phase Balancing via PSU Voltage Adjustment

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Solution Overview

Problem

Data centers face increased costs due to overdesigning infrastructure to handle phase imbalances in three-phase power supplies, which can occur rapidly with varying server loads and hot unplugging, leading to inefficiencies and unnecessary power handling requirements.

Innovation Solution

Implementing a system where power supply units use alternating combinations of two phases to output DC voltage to a common bus bar, with a rack manager detecting imbalances and adjusting output voltages to balance phase currents across the power supplies, thereby modifying the input load to compensate for imbalances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If power supply units use two of three phases to convert mains AC to DC power, then power conversion efficiency is improved, but phase current imbalance occurs causing infrastructure overdesign

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidinfrastructure overdesign

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The system dynamically switches between different phase combinations (AB, BC, CA) based on real-time load conditions and phase balance requirements. Power supply units can change which two phases they draw from, allowing the system to adapt to varying server loads and maintain phase balance without overdesigning infrastructure.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system implements periodic phase switching where power supply units alternate between different phase combinations in a cyclic manner. This periodic action distributes the load across all three phases over time, preventing sustained imbalance and eliminating the need for overdesigned power infrastructure.

Inventive Principle:

Principle #19Periodic action

2Reliability

If infrastructure is overdesigned to handle phase imbalances, then reliability is improved, but data center cost increases

Engineering Contradiction:

Improvepower supply reliabilityVSAvoidpower handling capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The system employs feedback mechanisms to monitor phase currents and load conditions in real-time. Based on this feedback, power supply units adjust their phase selection and switching behavior to maintain balance. This closed-loop control ensures reliability by preventing extreme imbalances without requiring excess power handling capacity in the infrastructure.

Inventive Principle:

Principle #23Feedback

3Device complexity

If phase currents are allowed to become unbalanced, then device complexity is reduced, but power handling requirements increase due to overdesign

Engineering Contradiction:

Improvepower supply control complexityVSAvoidpower handling capacity

Core Design Contradiction:

Device complexityVSPower

Solution Approach 1:

The system merges the control logic of multiple power supply units into a coordinated system where units share phase usage. By combining the operations of multiple PSUs and rotating their phase assignments, the system maintains simple individual unit designs while achieving overall phase balance at the system level, avoiding both complexity and overdesign.

Inventive Principle:

Principle #5Merging (Combining)

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 approach effectively balances phase currents, reducing the need for overdesign and optimizing power distribution within data centers, leading to cost savings and improved efficiency in handling power fluctuations.

Implementation Method 1

Power supply units can use two of the three phases to convert the mains AC to low-voltage regulated DC power for the computing components

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

A rack manager, using a processor, can detect that a current for a first phase is imbalanced with at least one of: a current for a second phase and a current for a third phase

Methodology Applied

Scientific EffectElectrical measurement:

Implementation Method 3

An output voltage can be adjusted for the at least one power supply. The adjusted output voltage can modify a current on a common bus bar and a common return bus bar

Methodology Applied

Scientific EffectVoltage regulation:

Data Source

PatentUS10126804B2Balancing input phases across server rack power supplies

Publication Date: 2018.11.13 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Aspects extend to methods, systems, and computer program products for balancing input phases across server rack power supplies. A rack manager can monitor individual Alternating Current (AC) phase currents at the rack level. The rack manager knows (or can at least determine) which power supplies are connected to which phase. The rack manager can micro adjust individual PSU output voltages to balance current phases at the rack level. Balancing can occur in response to changed server workloads, hot-unplug of one or more servers, etc. When there is one PSU per server, phase balancing can be accomplished by connecting outputs of power supplies together via busbar or wire. Output voltages of individual power supplies can be adjusted to achieve better phase balancing. Phase imbalance can be corrected by a bus bar or wire carrying enough load to correct phase imbalance.