Three-Phase PFC Converter Control Without Inductors or DC Link
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Solution Overview
Problem
Conventional three-phase PFC rectifiers are bulky and heavy due to the use of inductors and DC link capacitors, and they are difficult to control, particularly when implemented as dual active bridge cyclo-converters.
Innovation Solution
A method and control circuit for a three-phase PFC power converter that generates an alternating voltage based on input voltages, controlling input currents to match voltage waveforms without the need for bulky inductors and DC link capacitors, using a simplified control scheme and a switching circuit with bidirectionally blocking switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional three-phase PFC rectifier with inductors and DC link capacitor is used, then power factor correction is achieved, but the device becomes bulky and heavy
Solution Approach 1:
The patent removes the bulky inductors and DC link capacitor from the conventional PFC rectifier topology. By extracting these large passive components and replacing them with a capacitor-less PFC bridge circuit, the invention achieves power factor correction without the weight penalty of traditional inductor-based designs.
Solution Approach 2:
The patent replaces the mechanical/magnetic energy storage function of inductors with an electronic control mechanism. The capacitor-less PFC bridge uses active switching devices (IGBTs or MOSFETs) controlled by a microprocessor to achieve current waveform shaping and power factor correction without relying on large magnetic components.
2Weight of stationary object
If dual active bridge cyclo-converter topology is used, then inductors and DC link capacitor can be omitted, but control becomes difficult
Solution Approach 1:
The patent introduces a microprocessor as an intermediary control element that simplifies the control of the capacitor-less PFC bridge. The microprocessor generates the necessary gate drive signals for the switching devices and implements the control algorithm to shape the input current waveform, making the control process more manageable compared to traditional dual active bridge cyclo-converters.
Solution Approach 2:
The patent changes the control parameters and switching patterns of the PFC bridge to achieve simplified operation. By optimizing the switching sequences and control parameters of the active devices in the capacitor-less PFC bridge, the invention reduces control complexity while maintaining effective power factor correction.
3Reliability
If inductors and DC link capacitor are used, then power factor correction is achieved, but device size increases significantly
Solution Approach 1:
The patent extracts and removes the large passive components (inductors and DC link capacitor) from the PFC rectifier design. By eliminating these space-consuming elements and using a capacitor-less bridge topology with active switching, the invention achieves power factor correction in a significantly reduced footprint.
Solution Approach 2:
The patent changes the fundamental operating parameters of the PFC circuit by transitioning from a passive component-based design to an active switching-based design. This parameter change enables power factor correction without requiring large physical components, thereby reducing the overall device size.
Data Source
Figure 1A
Figure 1B~2
Figure 3~4
AI summary
Disclosed is a method. The method comprises generating an alternating voltage (Vmn) based on three alternating input voltages (Va, Vb, Vc) received at an input (a, b, c) of a power converter in an unregulated fashion, wherein generating the alternating intermediate voltage (Vmn) comprises controlling waveforms of three input currents (Ia, Ib, Ic) received at the input (a, b, c) dependent on waveforms of the three alternating input voltages (Va, Vb, Vc).