Substation High Voltage UPS Isolation Transformer Harmonic Cancellation
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Solution Overview
Problem
High power uninterruptible power supplies (UPS) face challenges in reducing total harmonic distortion (THD) and system losses due to the complexity of power distribution systems, which include multiple transformers and rectifiers, leading to inefficiencies and increased energy consumption.
Innovation Solution
The implementation of an isolation transformer with out-of-phase secondary windings and phase-shifted rectifiers, along with multiple inverters and a reference transformer, reduces THD and system losses by canceling harmonics and minimizing the need for additional power distribution devices, thereby simplifying the power distribution system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple transformers and rectifiers are used in the power distribution system, then the UPS can provide stable power conversion, but the total harmonic distortion increases and system losses increase
Solution Approach 1:
The patent divides the single transformer into multiple secondary windings and divides the single rectifier into multiple phase-shifted rectifiers. This segmentation allows each component to handle specific harmonic frequencies, reducing overall THD while maintaining stable power conversion.
Solution Approach 2:
The patent converts the harmful harmonic distortions into beneficial phase-shifted signals. By intentionally creating phase shifts between multiple rectifiers and using out-of-phase secondary windings, the harmonics that would normally be harmful are transformed into constructive interference patterns that cancel each other out, reducing THD while improving efficiency.
2Reliability
If multiple transformers and rectifiers are used in the power distribution system, then the UPS can provide stable power conversion, but system losses and energy consumption increase
Solution Approach 1:
The patent segments the power conversion path into multiple parallel channels with phase-shifted rectifiers. Each channel operates more efficiently in its optimal range, and the combined output maintains stable power conversion while reducing overall system losses through distributed operation.
Solution Approach 2:
The patent changes the phase angle parameter of multiple rectifiers relative to each other. By adjusting these phase shifts, the system optimizes the operating points of each rectifier-transformer path, allowing them to operate in their most efficient ranges and minimizing cumulative system losses while maintaining stable output.
3Reliability
If multiple transformers and rectifiers are used in the power distribution system, then the UPS can provide stable power conversion, but the system complexity increases
Solution Approach 1:
The patent merges multiple phase-shifted rectifier outputs into a single combined DC output that feeds the inverter. This merging approach maintains the benefits of multiple parallel paths for stable power conversion while consolidating the complexity into a unified interface, reducing the apparent system complexity.
Solution Approach 2:
The patent designs the multiple secondary windings and rectifiers to serve dual purposes: they individually provide stable power conversion paths while collectively functioning as a harmonic cancellation system. This multi-functionality reduces the need for separate harmonic filtering components, thereby reducing overall system complexity.
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 effectively reduces THD, minimizes system losses, and decreases energy consumption by eliminating the need for redundant power distribution components, resulting in a more efficient and cost-effective high power UPS system.
Implementation Method 1
The isolation transformer includes a primary winding and a plurality of secondary windings. The primary winding receives a first alternating current voltage from a utility substation. Each of the secondary windings generates a second alternating current voltage
Implementation Method 2
Each of the secondary windings generates a second alternating current voltage which is converted by the respective rectifiers to a direct current voltage
Implementation Method 3
An inverter having an input coupled to an output of each rectifier, converts the direct current voltage to a third alternating current voltage which is provided to output terminals of the high power uninterruptible power supply
Data Source
AI summary
A power supply includes an isolation transformer. The isolation transformer includes a primary winding and N secondary windings, where N is an integer. The primary winding receives a first alternating current voltage. Each of the N secondary windings generates a second alternating current voltage. M rectifiers convert the second alternating current voltages to a direct current voltage, where M is an integer. X inverters convert the direct current voltage to a third alternating current voltage, where X is an integer. A reference transformer is electrically coupled between the X inverters and output terminals of the power supply, is connected in parallel with the output terminals, and is configured to provide at least one of a neutral reference and a ground reference.