Galvanically Isolated Analog Control Circuit for Vienna Converter
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Solution Overview
Problem
Existing three-phase AC to DC power converters, such as Vienna converters, face challenges in maintaining a high power factor and low total harmonic distortion across varying input frequencies and amplitudes, while also requiring electrical connections to the neutral terminal and center terminal of filter capacitors, which complicates control and certification processes.
Innovation Solution
A galvanically isolated control circuit for the Vienna converter that operates entirely in the analog domain, generating gating signals for power switches based on unipolar voltage error signals and triangular wave carriers, eliminating the need for neutral terminal connections and software, thus allowing for independent control of AC currents and reduced harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital control electronics with software are used, then control flexibility and adaptability are improved, but device complexity and certification requirements increase
Solution Approach 1:
The patent replaces the digital control system (software-based) with an analog control circuit that processes control signals using analog electronic components. This substitution eliminates the need for software development, coding, and certification while maintaining control functionality through analog signal processing, directly resolving the contradiction between control flexibility and certification complexity
Solution Approach 2:
The patent introduces an analog control circuit as an intermediary between the sensor inputs and the power converter switches. This analog intermediary processes control signals continuously in the analog domain, providing adaptive control without requiring digital software, thus achieving flexibility while avoiding software certification requirements
2Measurement precision
If connection to neutral terminal and center terminal is made, then control accuracy is improved, but device complexity and safety risks increase
Solution Approach 1:
The patent extracts and eliminates the requirement for connections to the neutral terminal and center terminal of the output capacitor. By redesigning the control circuit to function without these connections, the patent reduces device complexity and safety risks while maintaining control accuracy through alternative sensing and control methods that do not require direct access to these terminals
3Ease of manufacture
If conventional control schemes are used, then implementation simplicity is improved, but power factor and harmonic distortion performance worsen under varying frequency and voltage conditions
Solution Approach 1:
The patent implements a dynamic control circuit that automatically adapts to varying input frequency and voltage conditions. The analog control circuit continuously adjusts control parameters based on real-time input conditions, enabling the system to maintain high power factor and low harmonic distortion across different operating conditions, thus improving reliability without sacrificing implementation simplicity
Data Source
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AI summary
Disclosed is a three phase Vienna converter for converting three phase AC to DC, with active power factor control. The control electronics is galvanically isolated from the neutral of the input supply and from the center terminal of the two series connected output DC filter capacitors. The control circuit is realised using analog devices to meet electromagnetic interference standards. The converter operates over a wide range of voltages and frequencies of supply voltage. Attenuated phase to neutral voltages are generated. The RMS values of these signals are derived. The attenuated voltages are divided by their RMS values to obtain Unity Sine Wave signals and are multiplied with the voltage error signal to obtain current reference signals. The current error signals between current reference signals and current feedback signals are compared with a triangular wave for generating gating signals for the controlled power switches of the Vienna converter.