UPS PWM Control for Sinusoidal Waveform and Voltage Regulation
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Solution Overview
Problem
Conventional uninterruptible power supplies (UPS) struggle to maintain a substantially sinusoidal output waveform and regulate output voltage effectively, especially when active power factor correction devices are connected, leading to potential overvoltage conditions and incompatibility with certain loads.
Innovation Solution
A method and system for a UPS that uses pulse width modulation (PWM) control signals to generate a substantially sinusoidal output voltage, with a controller that compares instantaneous output voltage to a reference RMS voltage, calculates and applies scaling factors to maintain the output voltage at a desired level, and adjusts PWM signals based on phase angles and harmonic components to ensure sinusoidal waveform and voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional UPS uses simple power conversion without advanced PWM control, then device complexity is reduced, but output waveform quality deteriorates (cannot maintain substantially sinusoidal output)
Solution Approach 1:
The patent implements dynamic PWM control where pulse widths are continuously adjusted based on instantaneous output voltage feedback. The controller dynamically modifies the switching duty cycle of power conversion devices to maintain sinusoidal waveform accuracy, transforming a static power conversion system into a dynamically controlled one that adapts to maintain waveform quality.
Solution Approach 2:
The patent employs feedback control by comparing the instantaneous output voltage with a reference sinusoidal waveform and using the error signal to adjust PWM control signals. This closed-loop feedback mechanism ensures the output waveform maintains substantial sinusoidal shape despite variations in load or input conditions, resolving the contradiction between waveform quality and control complexity.
2Manufacturing precision
If conventional UPS uses fixed PWM control signals, then device complexity is reduced, but output voltage regulation deteriorates (cannot maintain RMS voltage at reference level)
Solution Approach 1:
The control system dynamically adjusts PWM signal parameters including duty cycle and timing based on real-time output voltage measurements. The controller continuously calculates required PWM adjustments to maintain RMS voltage at the reference level, transforming fixed control into adaptive dynamic control that responds to voltage deviations.
Solution Approach 2:
The patent changes key control parameters (PWM duty cycle, pulse timing) based on detected output voltage conditions. When voltage deviates from reference, the system modifies these parameters to correct the deviation, enabling precise RMS voltage regulation through parameter adaptation rather than fixed control signals.
3Reliability
If conventional UPS lacks voltage comparison and scaling control, then device complexity is reduced, but overvoltage protection deteriorates (cannot prevent overvoltage conditions)
Solution Approach 1:
The system performs preliminary voltage comparison against reference levels before outputting PWM signals. By anticipating potential overvoltage conditions through continuous monitoring and preemptively adjusting PWM duty cycles, the system prevents overvoltage from occurring rather than reacting after it occurs, enhancing reliability through proactive control.
Solution Approach 2:
The patent implements feedback control where output voltage is continuously measured and compared to reference levels. When voltage approaches dangerous levels, the feedback loop automatically reduces PWM duty cycle to bring voltage back within safe operating ranges, providing automatic overvoltage protection through continuous feedback monitoring and corrective action.
4Adaptability or versatility
If conventional UPS uses basic power conversion, then ease of manufacture is improved, but adaptability deteriorates (incompatibility with active power factor correction devices)
Solution Approach 1:
The patent implements dynamic control that adapts to different load characteristics including active power factor correction devices. The controller dynamically adjusts PWM parameters based on detected load conditions, enabling the system to maintain sinusoidal output and proper voltage regulation across diverse load types, thereby improving adaptability through dynamic response.
Solution Approach 2:
The system changes PWM control parameters in response to different load types and conditions. By detecting load characteristics and adjusting duty cycle, frequency, and timing parameters accordingly, the power conversion circuit becomes adaptable to various loads including sophisticated power factor correction devices, resolving the contradiction between simplicity and adaptability.
Data Source
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AI summary
A method of operating an uninterruptible power supply (UPS) includes generating, during a portion of an output cycle, a substantially sinusoidal output voltage responsive to a plurality of pulse width modulation (PWM) control signals provided to a power conversion circuit of the UPS, comparing the output voltage to a reference root mean square (RMS) voltage at each of a plurality of time intervals during the portion of the output cycle, calculating a PWM control signal scaling factor based on each of the comparisons to the reference RMS voltage, and maintaining the output voltage at substantially the reference RMS voltage by applying the calculated PWM control signal scaling factor to at least one of the plurality of PWM control signals. The method may include detecting that the output voltage has reached a maximum output voltage level and clamping the output voltage to a steady state output voltage reference level.