UPS Inverter Counter Voltage Generation
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Solution Overview
Problem
Existing uninterruptible power supplies require multiple voltage detectors to generate a counter voltage when switching from bypass to inverter power supply mode, leading to high costs.
Innovation Solution
An uninterruptible power supply system that uses a single first voltage detector to control the inverter for voltage feedforward, generating a counter voltage at the first switch terminal, eliminating the need for additional detectors and preventing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple voltage detectors are used to detect voltages at both terminals of the first switch for generating counter voltage, then the inverter can be controlled to generate counter voltage accurately, but the cost increases
Solution Approach 1:
The patent merges the voltage detection function into a single voltage detector that detects the voltage at the third terminal (load terminal). The controller uses this single detection value to control both the first and second switches, eliminating the need for separate voltage detectors at each switch terminal while maintaining accurate voltage control for counter voltage generation.
Solution Approach 2:
The single voltage detector serves multiple functions: it detects the voltage at the load terminal, provides feedback for inverter control, enables counter voltage generation, and facilitates smooth transition between bypass and inverter power supply modes. This multi-functional approach reduces component count while maintaining system performance.
2Speed
If the first switch is turned on immediately during mode transition, then the switching is fast, but an inrush current flows from the bypass AC power source to the capacitor through the first switch
Solution Approach 1:
The patent implements preliminary action by controlling the inverter to generate counter voltage before turning on the first switch. The controller detects the voltage at the third terminal and uses this information to pre-charge or pre-discharge the capacitor through the inverter, ensuring that when the first switch closes, there is no voltage difference to cause inrush current. This preliminary voltage equalization eliminates the harmful inrush current while enabling fast switching.
Solution Approach 2:
The counter voltage generated by the inverter acts as a preliminary anti-action to prevent the inrush current. By generating a voltage that opposes the potential voltage difference across the first switch before closure, the system prevents the harmful inrush current from flowing through the capacitor and switch during mode transition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system reduces costs by eliminating the need for extra voltage detectors while effectively preventing inrush currents during mode transitions, ensuring efficient power supply.
Implementation Method 1
a converter configured to convert AC power supplied from the commercial AC power source through the first terminal into DC power
Implementation Method 2
an inverter configured to convert DC power generated by the converter or DC power in a power storage device into AC power
Data Source
AI summary
This uninterruptible power supply executes a counter voltage generation mode between a bypass power supply mode and a lap power supply mode. During the counter voltage generation mode, voltage feedforward control is performed for an inverter (2) in accordance with a detection value of a voltage detector (VD5) to generate a counter voltage at one terminal of a switch (S2), the counter voltage being at a level corresponding to a voltage at an output terminal (T4). Therefore, without providing an extra voltage detector for generation of counter voltage, an inrush current can be prevented from flowing from a bypass AC power source (52) to an AC filter (F2) through the switch (S2) when the switch (S2) is turned on.