Line-Interactive UPS Topology With Series Capacitor Voltage Regulation
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Solution Overview
Problem
Existing uninterruptible power supplies (UPSs) face efficiency challenges due to double-conversion of input power, which increases costs and reduces performance, especially in line-interactive modes.
Innovation Solution
The implementation of a line-interactive UPS that combines a power-factor-correction (PFC) circuit and a series-active-filter inverter topology, with a capacitor coupled in series with the load, allows for efficient voltage regulation and power conditioning by varying the voltage across the capacitor in response to input voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If double-conversion of input power is implemented in UPS, then power quality and reliability are improved, but efficiency deteriorates and costs increase
Solution Approach 1:
The system dynamically switches between online double-conversion mode and line-interactive mode based on input power quality conditions. When input voltage is within acceptable ranges, the system operates in line-interactive mode with higher efficiency; when input voltage deviates significantly, it transitions to online mode to maintain power quality and reliability.
Solution Approach 2:
The system changes operational parameters by adjusting the switching state between different conversion modes. The controller monitors input voltage parameters and modifies the power conversion configuration accordingly, transitioning between full double-conversion and partial conversion to optimize the balance between reliability and efficiency.
2Reliability
If double-conversion of input power is implemented in UPS, then power quality is improved, but device complexity increases
Solution Approach 1:
The power conversion circuitry is designed to perform multiple functions: it can operate as a full online double-conversion system when high power quality is required, or as a line-interactive system when input power is acceptable. This multi-functionality reduces the need for separate dedicated circuits for each mode, thereby managing complexity while maintaining power quality improvement capabilities.
3Loss of energy
If voltage across capacitor is varied in response to input voltage changes, then power conditioning efficiency is improved, but control complexity increases
Solution Approach 1:
The controller implements feedback control by monitoring input voltage conditions and automatically adjusting the voltage across the capacitor accordingly. This closed-loop control optimizes power conditioning efficiency by varying capacitor voltage in response to actual input conditions, reducing energy losses while managing control complexity through automated regulation.
Data Source
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AI summary
Examples of the disclosure include a power-conditioning system comprising a load output configured to be coupled to a load, a power-factor-correction circuit (PFC) comprising a first switching leg and a second switching leg, wherein the first switching leg and the second switching leg are configured to be controlled based on a first modulation index, an inverter comprising the second switching leg and a third switching leg, wherein the third switching leg is configured to be controlled based on a second modulation index, and a capacitor coupled to an inverter output of the inverter and being coupled in series with the load output.