UPS Voltage Distortion Detection and Inverter Switching

Solution Overview

Problem

UPS systems operating in economic mode cannot actively condition AC voltage, leading to potential damage and inefficiency due to distorted AC voltage signals from utility power sources, which may exceed tolerance levels.

Innovation Solution

A method and system for real-time detection of total harmonic distortion (THD) in AC voltage signals using a processor to generate a reference signal, calculate RMS values, and determine THD, enabling switching between bypass and inverter feed paths based on distortion levels to ensure power quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the UPS system operates in economic mode using bypass feed path, then operational cost is reduced and efficiency is improved, but power quality deteriorates due to voltage distortion from utility power source

Engineering Contradiction:

Improveoperational costVSAvoidvoltage distortion

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary detection of voltage distortion using THD calculation before the distorted voltage can cause damage to the load. The controller continuously monitors the bypass path voltage quality and prepares switching action in advance when distortion exceeds thresholds, preventing harmful effects rather than reacting after damage occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback control by continuously calculating THD of the bypass path voltage and using this information to control the switching between bypass and inverter paths. The real-time THD measurement feeds back to the controller, which adjusts the operating mode accordingly, creating a closed-loop system that maintains power quality while optimizing efficiency.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If the UPS system uses bypass feed path for power delivery, then efficiency is improved, but reliability deteriorates due to inability to actively condition AC voltage

Engineering Contradiction:

ImproveefficiencyVSAvoidpower quality

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system performs preliminary detection of voltage distortion using THD calculation before the distorted voltage can cause damage to the load. The controller continuously monitors the bypass path voltage quality and prepares switching action in advance when distortion exceeds thresholds, preventing harmful effects rather than reacting after damage occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback control by continuously calculating THD of the bypass path voltage and using this information to control the switching between bypass and inverter paths. The real-time THD measurement feeds back to the controller, which adjusts the operating mode accordingly, creating a closed-loop system that maintains power quality while optimizing efficiency.

Inventive Principle:

Principle #23Feedback

3Reliability

If real-time THD detection is implemented, then power quality protection is improved, but device complexity increases due to additional processing requirements

Engineering Contradiction:

Improvepower quality protectionVSAvoidcomputational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical or hardware-based voltage conditioning systems with a computational approach. Instead of using complex power electronic circuits to actively condition every voltage waveform, the system uses digital signal processing to detect THD and switches between operating modes based on calculated distortion levels, simplifying the overall system architecture while maintaining protection capabilities.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9404947B2Systems and methods for detecting power quality of uninterrupible power supplies

Publication Date: 2016.08.02 ABB (SCHWEIZ) AG

AI summary

A system may include an uninterruptible power supply (UPS) configured to provide power to a load via a bypass feed path coupled to a first power source or via an inverter feed path coupled to a second power source. The UPS may include a controller configured to switch between providing power to the load via the bypass feed path and the inverter feed path based at least in part on a real-time calculation of an amount of voltage distortion present on a voltage signal input to the load via the bypass path. As such, the controller may be configured to provide power to the load via the inverter feed path when the amount of voltage distortion is greater than a limit.