Power Converter Phase Reference from DC Bus Voltage
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Solution Overview
Problem
Conventional AC/DC power converters face challenges in maintaining stable DC bus voltage and efficient power transfer between AC and DC buses, particularly in varying AC input conditions, as they often rely on direct phase/frequency control methods that are limited by AC input frequency and do not effectively utilize DC bus voltage feedback for adaptive phase shifting.
Innovation Solution
The method involves generating a phase offset signal from a DC voltage error signal, which is differentiated to produce a phase reference signal, allowing for adaptive phase shifting and power transfer between AC and DC buses, using a converter circuit like an active bridge circuit, and incorporating a magnitude reference signal generated from phase current and DC voltage to stabilize power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If direct phase/frequency control methods are used to transfer power between AC and DC buses, then power transfer can be achieved, but the DC bus voltage stability deteriorates under varying AC input conditions
Solution Approach 1:
The patent implements a feedback mechanism where the DC bus voltage is continuously monitored and used to generate a phase offset signal. This feedback loop allows the system to automatically adjust the phase of the AC current in response to voltage deviations, maintaining stable DC bus voltage even under varying AC input conditions while ensuring reliable power transfer.
2Power
If conventional phase control methods are used, then power transfer is achieved, but adaptability to varying AC input conditions deteriorates
Solution Approach 1:
The patent employs dynamic phase adjustment by differentiating the DC voltage error signal to generate a phase offset signal. This dynamic approach allows the phase of the AC current to continuously adapt to changing AC input conditions, enabling the system to maintain effective power transfer across varying operational environments rather than relying on fixed phase control.
3Device complexity
If DC bus voltage feedback is not utilized for phase shifting, then control simplicity is maintained, but power transfer efficiency deteriorates
Solution Approach 1:
The patent utilizes DC bus voltage feedback to generate a phase offset signal through differentiation. This feedback mechanism enables the system to automatically optimize the phase angle between AC voltage and current, maximizing power transfer efficiency by ensuring unity power factor operation while maintaining relatively simple control circuitry.
Data Source
AI summary
In a power converter apparatus, such as an uninterruptible power supply, a phase reference signal is generated responsive to a DC voltage on a DC bus. A magnitude reference signal may be generated responsive to a phase current of an AC bus and/or the DC voltage on the DC bus. Power is transferred between the AC and DC busses responsive to the phase reference signal and the magnitude reference signal. Generation of the phase reference signal may include generating a DC voltage error signal responsive to the DC voltage on the DC bus, generating a phase offset signal responsive to the DC voltage error signal, and generating the phase reference signal responsive to the phase offset signal. Generation of the magnitude reference signal may include generating a volt-amperes reactive (VAR) error signal responsive to the phase current and generating the magnitude reference signal responsive to the VAR error signal.