UPS Square Wave Inverter Voltage Control
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Solution Overview
Problem
Existing uninterruptible power supplies (UPS) using square wave power face instability and oscillations when powering active Power Factor Correction (PFC) loads, due to the difference in voltage relationships between sine and square waves, leading to potential damage and premature shutdown.
Innovation Solution
A control system for UPS that monitors and controls both the average and RMS voltage of the square wave output, using a pulse width modulation controller to clamp the output to zero when thresholds are met, preventing oscillations and ensuring stable power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a square wave inverter is used to provide backup AC power, then the system cost is reduced and simplicity is improved, but voltage instability and oscillations occur when powering active PFC loads
Solution Approach 1:
The patent implements a control system that continuously monitors the output voltage of the square wave inverter and uses feedback signaling to detect voltage deviations. When voltage instability or oscillations are detected, the controller adjusts the inverter operation to correct the deviation, thereby maintaining voltage stability while preserving the simplicity of square wave architecture
Solution Approach 2:
The control system dynamically adjusts operational parameters of the square wave inverter based on load conditions and voltage measurements. By changing parameters such as switching frequency or duty cycle in response to detected voltage instability, the system maintains stable operation without requiring complex waveform generation
2Ease of manufacture
If square wave power is used to reduce system cost, then manufacturing cost is reduced, but active PFC loads experience damage and premature shutdown
Solution Approach 1:
The patent introduces a control system as an intermediary between the simple square wave inverter and the active PFC loads. This intermediary monitors voltage conditions and intervenes when necessary to prevent damaging voltage spikes or oscillations, thereby protecting the loads while maintaining the cost-effectiveness of square wave operation
3Ease of operation
If conventional voltage control is used in square wave inverters, then basic operation is maintained, but voltage oscillations cause premature shutdown
Solution Approach 1:
The control system employs feedback mechanisms that continuously monitor voltage stability and provide real-time adjustments to prevent oscillations. This feedback control enables the inverter to maintain stable operation for extended periods without premature shutdown, while preserving the ease of operation inherent in square wave architecture
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 effectively prevents oscillations and damage by accurately controlling the square wave output, ensuring seamless power transfer and stable operation of active PFC loads, reducing the risk of premature shutdown and voltage damage.
Implementation Method 1
using a pulse width modulation controller to clamp the output to zero when thresholds are met
Data Source
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AI summary
According to one aspect, embodiments of the invention provide an uninterruptible power supply (UPS) system comprising an input configured to receive input AC power, an output configured to provide output AC power to a load, a DC power source coupled to a DC bus, an inverter having an input coupled to the DC bus and an output coupled to the output of the UPS system, the inverter configured to receive DC power at the input from the DC bus and provide AC power having a voltage to the output, and a controller coupled to the output of the inverter and configured to operate the inverter based on an average voltage of the AC power at the output of the inverter.