UPS Inverter Phase Control for Ferroresonant Transformer Saturation
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Solution Overview
Problem
Switch mode power supplies in UPS systems suffer from inefficiency due to imperfect switching characteristics of modern power switches during transitions between ON and OFF configurations.
Innovation Solution
The implementation of a UPS system that includes a ferroresonant transformer, a resonant capacitor, and an inverter, where the inverter generates a pulse-width modulated output power signal with phase changes to meet load voltage requirements while avoiding transformer saturation, and eliminates pulse-width modulation during peak current transfer to improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pulse-width modulation is used during phase changes to meet voltage requirements, then voltage regulation is improved, but power switch transitions increase causing efficiency loss
Solution Approach 1:
The patent extracts and eliminates pulse-width modulation during peak current transfer periods when the AC waveform crosses zero. By removing PWM control during these specific intervals, the system avoids unnecessary power switch transitions while maintaining voltage regulation during other phases where PWM is applied.
Solution Approach 2:
The patent applies periodic modulation by enabling PWM control during specific portions of the AC cycle (when voltage needs regulation) and disabling it during other portions (during peak current transfer). This periodic application of PWM based on waveform phase optimizes the balance between voltage regulation and switching loss.
2Power
If power switches are frequently transitioned to regulate voltage, then voltage control precision is improved, but switching efficiency deteriorates
Solution Approach 1:
The patent extracts and removes PWM control during specific intervals when it would cause excessive switching without providing benefit - specifically during peak current transfer when the AC waveform is near zero. This eliminates wasteful switching actions while preserving voltage control precision during phases where PWM effectively regulates voltage.
Solution Approach 2:
Instead of applying PWM continuously, the patent applies it partially - only during portions of the AC cycle where voltage regulation is needed. This partial application avoids excessive switching during periods when voltage control is not critical, thereby improving overall switching efficiency while maintaining adequate voltage control precision.
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 the efficiency of the UPS system by 10-20% in standby mode by minimizing power switch transitions during peak current transfer, thereby reducing energy loss.
Implementation Method 1
A ferroresonant transformer is a saturating transformer that employs a tank circuit comprised of a resonant winding and capacitor to produce a nearly constant average output even if the input to the transformer varies
Implementation Method 2
A ferroresonant transformer is a saturating transformer
Implementation Method 3
A ferroresonant transformer is a saturating transformer that employs a tank circuit comprised of a resonant winding and capacitor to produce a nearly constant average output
Implementation Method 4
The PWM method of generating an AC signal from a DC source allows the amplitude of the AC signal to be determined at any point in time by controlling the duty cycle at which the inverter power switches are operated
Data Source
AI summary
An uninterruptible power supply for providing an output power signal to a load comprises a ferroresonant transformer, a resonant capacitor, and an inverter. The resonant capacitor is operatively connected to the ferroresonant transformer. The inverter is operatively connected to the ferroresonant transformer. The inverter is configured to generate the output power signal based on at least one inverter control signal such that the output power signal is a quasi square wave having at least one change of phase and an upper limit. The at least one inverter control signal is held in an OFF state during at least a portion of the at least one change of phase, pulse-width modulated during at least a portion of the at least one change of phase, and held in an ON state when the output power signal is at the upper limit.