Multiphase AC/AC Converter Hybrid Modulation Switching Losses
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Solution Overview
Problem
Existing power conversion technologies face challenges with switching losses and stress on high-frequency, high-voltage devices, as well as the need for bulky and costly magnetics and filters in high-power applications, particularly in fuel-cell based systems.
Innovation Solution
A hybrid modulation method for ac/ac conversion that reduces switching requirements by modulating only one leg of a multi-phase switching scheme at a carrier frequency, while the others do not switch, using a bridge with switches and a controller to manage pulsating dc inputs and provide a multiphase modulated output, thereby reducing overall losses and harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If all switch legs modulate the pulsating dc input at carrier frequency, then the output waveform quality is improved, but switching losses increase significantly
Solution Approach 1:
The patent divides the multi-phase switch legs into two groups: one leg that modulates at carrier frequency and other legs that do not switch. This segmentation allows the system to achieve waveform quality through selective modulation while minimizing overall switching losses by reducing the number of active switching operations.
Solution Approach 2:
The patent applies partial action by having only one switch leg perform carrier-frequency modulation while other legs remain inactive or switch at lower frequency. This partial modulation approach provides sufficient output waveform quality without the excessive switching losses that would result from all legs switching at full carrier frequency.
2Weight of stationary object
If high-frequency transformers are used to reduce size, then the transformer weight and footprint are reduced, but switching losses and stress on devices increase
Solution Approach 1:
The patent changes the switching frequency parameter by using hybrid modulation where only one leg switches at carrier frequency while others operate at lower frequency or remain static. This parameter change maintains the benefits of high-frequency transformer operation for size reduction while mitigating the increase in switching losses and device stress.
3Productivity
If multiple switch legs operate at carrier frequency, then the power conversion efficiency is improved, but the complexity of control increases
Solution Approach 1:
The patent extracts the carrier-frequency switching function from all switch legs and concentrates it in only one leg. This extraction simplifies the control complexity by reducing the number of high-frequency switching operations that need to be coordinated, while the other legs can be controlled with simpler, lower-frequency switching or static states.
Data Source
AI summary
An ac/ac converter for accepting a pulsating dc input with encoded sinusoidal modulation and providing a multiphase modulated output. The converter comprises a bridge including a plurality of switches having switch legs for modulating the pulsating dc input at a carrier frequency over a plurality of phases. The bridge is coupled at one end to a pulsating dc source and coupled at another end to a modulated signal output. A controller is provided for the plurality of switches for causing, for each of the plurality of phases, under unity power factor, one of the switch legs to modulate the pulsating dc input at the carrier frequency while the other switch legs do not modulate the pulsating dc input at the carrier frequency.