Three-Phase Boost Rectifier PWM Control for Low-Distortion AC-DC Conversion
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Solution Overview
Problem
Existing three-phase AC-to-DC converters for applications like electric vehicle charging and MRI scanners face challenges in achieving low current distortions, independent control of sinusoidal currents, and efficient power factor correction while requiring a neutral conductor connection, often involving complex and costly designs.
Innovation Solution
The electrical converter design incorporates a three-phase bridge rectifier with boost inductors and semiconductor switches controlled by pulse width modulation, allowing for pulsed voltage generation and independent current control, with a distributed boost circuit and shared inductors to minimize hardware and reduce switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional six-switch boost-type PFC rectifier or VIENNA rectifier is used, then high voltage DC conversion is achieved, but device complexity and cost increase
Solution Approach 1:
The patent merges the rectifier and boost converter functions into a single integrated circuit structure. The three-phase bridge rectifier and boost circuit share common components including the DC bus, semiconductor switches, and diodes. This integration eliminates the need for separate rectifier and boost converter stages, reducing overall device complexity while maintaining the capability to generate high voltage DC output from three-phase AC input.
2Adaptability or versatility
If neutral conductor connection terminal is added for independent current control, then current control flexibility is improved, but device complexity increases
Solution Approach 1:
The neutral conductor connection terminal serves multiple functions: it provides a reference potential for PWM control, enables independent control of three-phase currents, facilitates power factor correction, and allows the converter to operate in both balanced and unbalanced load conditions. By making the neutral terminal multi-functional, the patent achieves enhanced adaptability without proportionally increasing device complexity.
3Object-generated harmful factors
If PWM control with multiple semiconductor switches is implemented, then current distortion is reduced, but switching losses increase
Solution Approach 1:
The patent employs periodic PWM switching control for the semiconductor switches in both the rectifier and boost stages. By using high-frequency periodic switching with duty cycle modulation, the converter achieves sinusoidal input currents with low distortion. The periodic action allows for precise control of power factor and current waveform while distributing switching losses over time, managing the energy loss through proper switching timing and dead-time optimization.
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
This design achieves low input current distortions, reduced hardware requirements, improved efficiency, and independent control of currents, while maintaining a simple and cost-effective structure for three-phase AC-to-DC conversion.
Implementation Method 1
The boost inductors are connected between the phase terminals and the three phase bridge rectifier
Implementation Method 2
an output filter comprising a filter capacitor connected between the boost circuit and the output terminals
Implementation Method 3
The controller is configured to control the at least one second semiconductor switch via pulse width modulation allowing for obtaining a pulsed intermediate voltage
Data Source
AI summary
Electrical converters of the present disclosure feature a boost circuit that is fully integrated with a three phase bridge rectifier to allow for obtaining a pulsed voltage at the rectifier output. Actively switchable semiconductor switches of the boost circuit are controlled by pulse width modulation (PWM) control signals to obtain the pulsed voltage. PWM of this pulsed voltage allows control of two out of three currents at the three input terminals of the rectifier, i.e., the currents at the phase inputs having the highest and the lowest voltage levels of the three phase input voltage.