Resonant Three-Phase PFC Converter With Integrated Isolation Control
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Solution Overview
Problem
Conventional three-phase PFC converters are bulky due to the use of multiple inductors and a DC link capacitor, and are difficult to control, necessitating a more compact and controllable design.
Innovation Solution
A power converter with multiple resonant converter stages and a control circuit that adjusts the operating frequency and power transfer duty cycles to regulate input currents and output voltages, reducing the number of components and improving control efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional three-phase PFC rectifier with two stages (including three inductors and a DC link capacitor) is used to provide galvanic isolation, then galvanic isolation between input and output is achieved, but the device becomes bulky and heavy with large component count
Solution Approach 1:
The patent combines multiple converter stages into a single integrated resonant converter stage that performs both power conversion and galvanic isolation functions. The series connection of transformer secondary windings provides both the voltage transformation and galvanic isolation, eliminating the need for separate inductors and DC link capacitor while maintaining the isolation function.
Solution Approach 2:
The resonant converter stage is designed to simultaneously perform multiple functions: power factor correction, voltage transformation, galvanic isolation, and current waveform shaping. The transformer with series-connected secondary windings serves both as the isolation barrier and the voltage multiplication mechanism, reducing overall component count.
2Device complexity
If a three-phase dual active bridge (DAB) converter is used to reduce inductors and omit DC link capacitor, then component count is reduced, but the converter becomes difficult to control
Solution Approach 1:
The control circuit monitors the output voltage and adjusts the duty cycle of the resonant converter stage to maintain stable operation. This feedback mechanism simplifies control by providing direct voltage regulation, avoiding the complex control algorithms required by DAB converters while maintaining component reduction benefits.
Solution Approach 2:
The patent utilizes resonant frequency operation and duty cycle modulation to control power transfer. By operating at or near the resonant frequency of the LC tank circuit and adjusting the duty cycle, the converter achieves simple and effective control without requiring the complex bidirectional switching control needed in DAB topologies.
3Productivity
If multiple inductors and DC link capacitor are used in conventional PFC rectifier, then power factor correction is achieved, but the device occupies large volume and has high weight
Solution Approach 1:
The patent merges the power factor correction function with the voltage transformation and isolation functions in a single resonant converter stage. The series resonant topology with transformer provides both the reactive power compensation needed for PFC and the voltage step-up, eliminating separate inductor and capacitor components that contribute to weight.
Solution Approach 2:
The resonant converter utilizes the resonant oscillation between inductor and capacitor to achieve power factor correction. By operating at the resonant frequency where the reactive impedance cancels out, the system achieves unity power factor without requiring large separate reactive components, thereby reducing weight while maintaining PFC capability.
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
The solution results in a more compact and efficiently controlled three-phase PFC converter with reduced electronic components, achieving effective power factor correction and sinusoidal input currents.
Implementation Method 1
Each of the plurality of converter stages (1a, 1b, 1c) includes a switching circuit (2a, 2b, 2c), a resonant circuit (4a, 4b, 4c), and a transformer (5a, 5b, 5c)
Implementation Method 2
a first resonant circuit (4a) connected to the switching circuit (2a), a second resonant circuit (4b) connected to the switching circuit (2b), and a third resonant circuit (4c) connected to the switching circuit (2c)
Data Source
Figure 1
Figure 2~4
Figure 5~6
AI summary
A power converter and a power conversion method are disclosed. The power converter includes a plurality of resonant converter stages (1a, 1b, 1c) each Including an input (Ina, Inb, Inc) and an output (Outa, Outb, Outc); a rectifier circuit (6); and a control circuit (7) configured to control operation of the plurality of resonant converter stages (1a, 1b, 1c). The input (Ina, Inb, Inc) of each of the plurality of converter stages (1a, 1b, 1c) is configured to receive a respective input voltage (Vina, Vinb, Vine). The rectifier circuit (6) is connected to the outputs (Outa, Outb, Outc) of the plurality of converter stages (1a, 1b, 1c) and is configured to provide an output signal (Vout, Iout) based on a cascaded voltage that is dependent converter stage output voltages (Vseca, Vsecb, Vsecc) provided at the outputs (Outa, Outb, Outc) of the resonant converter stages (1a, 1b, 1c).