UPS Auxiliary Branch Bypasses Rectifier to Reduce Switching Losses
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Solution Overview
Problem
Conventional Uninterruptible Power Supplies (UPS) face efficiency losses due to switching losses in power conversion, leading to decreased power density and increased heat production, particularly in 3-level Neutral Point Clamped (NPC) topologies used in online and offline UPS systems.
Innovation Solution
The implementation of a 3-level NPC topology with an auxiliary branch that selectively bypasses the rectifier and inverter during certain voltage conditions, utilizing a controller to switch between buck, freewheel, connection, and stop modes based on input and output voltage levels to minimize switching losses and maximize efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional rectifier and inverter stages are used in UPS systems, then power conversion is achieved, but switching losses increase and efficiency decreases
Solution Approach 1:
The patent extracts and removes the conventional rectifier and inverter stages from the power conversion path. Instead of using traditional multi-stage conversion, the invention directly couples the AC input to the AC output through a simplified topology with auxiliary switches, eliminating the sources of switching losses while maintaining power conversion functionality.
Solution Approach 2:
The patent inverts the conventional approach by not using rectification and inversion stages. Instead of AC→DC→AC conversion, the system uses direct AC coupling with auxiliary switching elements that perform power factor correction and voltage regulation without traditional rectifier/inverter hardware, thereby eliminating switching losses.
2Loss of energy
If auxiliary branch is enabled during buck mode, then power conversion efficiency improves, but device complexity increases
Solution Approach 1:
The auxiliary branch in the patent serves multiple functions: it performs buck conversion when input voltage exceeds output voltage, provides freewheeling paths for inductor current, and enables direct AC coupling. This multi-functionality allows a single auxiliary branch structure to handle various operating conditions without requiring separate circuits for each function, thereby limiting the increase in device complexity.
3Adaptability or versatility
If multiple operating modes are implemented, then adaptability to different voltage conditions improves, but control complexity increases
Solution Approach 1:
The patent implements dynamic mode switching based on real-time comparison of input and output voltage levels. The controller dynamically selects between buck mode, freewheel mode, and direct coupling mode according to voltage conditions, enabling adaptability without requiring complex predetermined control schemes. The switching criteria are simple voltage threshold comparisons that reduce control complexity.
Data Source
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AI summary
According to one aspect, a UPS system is provided including an input configured to receive AC input power, an output configured to provide AC output power to a load, a rectifier coupled to the input, an inverter coupled to the rectifier and the output, an auxiliary branch coupled to the input and the output, and a controller coupled to the rectifier, the inverter, and the auxiliary branch, and configured to receive voltage information indicative of a voltage level of the AC input power and AC output power, select, based on the voltage information satisfying a first condition, a buck mode of operation, select, based on the voltage information satisfying a second condition, a freewheel mode of operation, and communicate one or more control signals to at least one of the rectifier, the inverter, and the auxiliary branch based on the selected mode of operation.