UPS Bus Voltage Control for Switch Loss Reduction
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Solution Overview
Problem
Conventional methods for controlling single-phase AC/AC converters in uninterruptible power supplies face inefficiencies and high reactive currents, particularly during light-load conditions, due to large switch losses and poor dynamic performance.
Innovation Solution
A method that controls the bus voltage by segment division, adjusting the bus voltage parameter K between 0 and 1 to achieve a DC voltage or full-wave rectifying voltage, and regulating duty cycles of the boost and buck arms to minimize reactive current and ripple, ensuring high efficiency across all load states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the single-phase AC/AC converter is operated at high frequency pulse-width-modulation mode with DC bus voltage waveform, then the input current can be controlled to be a sine-wave obtaining unit input power factor and output voltage can be accurately regulated, but the switch loss is large and efficiency is poor especially under full-load
Solution Approach 1:
The patent dynamically switches between two operating modes (DC bus voltage mode and full-wave rectifying voltage mode) based on load conditions. Under light-load conditions, the system operates in DC bus voltage mode for precise voltage regulation. Under heavy-load conditions, it transitions to full-wave rectifying voltage mode to reduce switch losses, thereby achieving both accurate voltage regulation and high efficiency across different operating states.
Solution Approach 2:
The patent changes the bus voltage waveform parameter from DC to full-wave rectifying voltage based on load conditions. This parameter change allows the system to optimize performance: DC waveform provides accurate voltage regulation under light-load, while full-wave rectifying waveform reduces switch losses under full-load, resolving the contradiction between precision and efficiency.
2Volume of stationary object
If the bus capacitor has small capacitance to obtain full-wave rectifying voltage waveform, then the volume can be decreased and reliability is enhanced, but the reactive current of input is large and dynamic performance is poor
Solution Approach 1:
The patent dynamically adjusts the bus voltage waveform based on load conditions. Under light-load conditions, it uses DC bus voltage to minimize reactive current. Under heavy-load conditions, it switches to full-wave rectifying voltage waveform, allowing the use of smaller bus capacitors without excessive reactive current penalties, thus achieving both compact size and acceptable dynamic performance.
3Volume of stationary object
If the converter is operated at full-wave rectifying voltage waveform mode, then the volume can be decreased and reliability enhanced, but the loss of the converter is large during light-load or no-load period
Solution Approach 1:
The patent implements dynamic mode switching based on real-time load detection. Under light-load or no-load conditions, the system operates in DC bus voltage mode which minimizes converter losses. Under heavy-load conditions, it transitions to full-wave rectifying voltage mode enabling compact design. This dynamic adaptation resolves the contradiction between volume reduction and loss minimization across different operating states.
4Productivity
If conventional controlling methods are used, then the system can operate under normal conditions, but the efficiency is poor and reactive current is large particularly during light-load conditions
Solution Approach 1:
The patent employs dynamic mode switching that adapts to real-time load conditions. Under light-load conditions, it selects DC bus voltage mode which minimizes reactive current and maximizes efficiency. Under heavy-load conditions, it switches to full-wave rectifying voltage mode to maintain operational capability. This dynamic control strategy simultaneously ensures system productivity and optimizes efficiency across all operating states.
Data Source
AI summary
A method of controlling an uninterruptible power supply apparatus (UPS) is provided. The UPS apparatus includes at least an AC input voltage, a DC input voltage and a single-phase AC/AC converter. The single-phase AC/AC converter includes an AC inductor, a bus capacitor, a boost arm, a common arm and a buck arm. The method includes steps of: controlling the bus voltage to have a DC component and full-wave rectifying component, and setting a bus voltage parameter K so that the bus voltage approaches to a full-wave rectifying voltage when K approaches to 1, wherein 0≦K≦1.