Transformer-less AC-AC Power Converter Topology for High Density UPS
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Solution Overview
Problem
Existing online uninterruptible power supply (UPS) systems face challenges in achieving high power density due to the need for bulky components, such as transformers and large inductances, which limit switching frequency and increase volume, especially in applications with space constraints like data centers and aerospace.
Innovation Solution
A transformer-less AC-AC power converter topology with a common neutral between input and output AC ports, utilizing half-bridge switch structures and a single DC bus, enabling high-frequency operation up to 2 MHz and achieving a power density of 26.4 W/in3 in a 1-kVA prototype converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If transformer-less designs are used to reduce volume, then power density is improved, but common neutral configuration becomes required which limits topology choices
Solution Approach 1:
The patent merges the PFC rectifier and inverter stages into a single unified circuit topology that shares common components (inductors, switches, capacitors) and provides both PFC and common-neutral functions simultaneously. This integration eliminates the need for separate transformer and PFC circuitry while achieving the desired common-neutral configuration between input and output ports.
2Volume of moving object
If switching frequency is increased to reduce size, then power density is improved, but high-frequency-loop inductances from four-quadrant switches limit the achievable frequency
Solution Approach 1:
The patent extracts and eliminates the four-quadrant switches from the topology, replacing them with standard half-bridge switches that have significantly lower loop inductances. This removal of the limiting component enables operation at much higher switching frequencies (MHz range) while maintaining the same power processing capability.
3Reliability
If split DC bus architecture is used to achieve common neutral, then grounding requirements are met, but capacitor voltage balancing challenges and volume increase occur
Solution Approach 1:
The patent merges the DC bus architecture into a single unified bus that serves both the PFC rectifier and inverter stages. This single DC bus eliminates the voltage balancing challenges of split-bus architectures and reduces the total capacitor volume required, while still achieving common-neutral configuration through the unified circuit topology.
Data Source
AI summary
The present disclosure provides a high-power-density power converter topology with a common neutral between its input and output AC ports while having a single DC bus. The topology may also be embodied as an online uninterruptible power supply (UPS). The presently-disclosed topology enables high power density by utilizing half-bridge switch structures suitable for MHz-frequency operation.