Resonant Grid-Tied Power Converter for Power Factor Correction
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Solution Overview
Problem
Existing DC-AC converters face challenges in efficiently controlling power factor and waveform matching when converting DC power to AC power for feeding into an AC power grid, particularly in three-phase systems.
Innovation Solution
A power converter design incorporating an input stage with a switching circuit and capacitors, coupled with multiple resonant converter stages and a transformer, controlled by a control circuit to generate alternating voltages and currents that match the AC grid waveform, ensuring efficient power transfer and power factor correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DC-AC converter is used to convert DC power to AC power for feeding into an AC power grid, then power conversion is achieved, but power factor control and waveform matching are difficult to maintain efficiently
Solution Approach 1:
The converter is divided into multiple resonant converter stages (first resonant converter stage, second resonant converter stage, etc.), each connected to a different phase of the power grid. This segmentation allows independent control of each phase, enabling effective power factor control and waveform matching for three-phase systems while maintaining modular structure.
Solution Approach 2:
The control circuit operates each resonant converter stage in periodic operating cycles that include precharge phases and transfer phases. During precharge phases, resonant currents are built up; during transfer phases, power is transferred to the grid. This periodic operation enables precise control of power factor and waveform synchronization with the AC grid.
2Productivity
If multiple resonant converter stages are added to improve power factor control and waveform matching, then power conversion efficiency improves, but device complexity increases
Solution Approach 1:
Each resonant converter stage is designed with universal functionality to perform multiple tasks: power conversion, power factor correction, and waveform synchronization. The stages share common control strategies and circuit topologies, allowing the system to achieve high power conversion efficiency without proportionally increasing complexity, as each added stage provides multi-functional benefits.
Solution Approach 2:
The control circuit dynamically adjusts operating parameters (such as switching frequencies, duty cycles, and resonant current levels) of each converter stage to optimize power conversion efficiency. By changing these parameters adaptively, the system maintains high productivity while managing device complexity through intelligent control rather than purely structural additions.
3Reliability
If resonant converter stages with precharge and transfer phases are implemented, then power factor correction and waveform matching improve, but control complexity increases
Solution Approach 1:
The control circuit incorporates feedback mechanisms that monitor grid voltage waveforms and resonant current levels in real-time. Based on this feedback, the controller adjusts the timing and duration of precharge and transfer phases to maintain precise waveform matching with the AC grid. This feedback-based control achieves reliable waveform synchronization while managing control complexity through adaptive rather than purely open-loop strategies.
Solution Approach 2:
Before each power transfer phase, the control circuit executes a precharge phase where resonant currents are built up in advance. This preliminary action ensures that when the transfer phase begins, the converter is already prepared to deliver synchronized, waveform-matched power to the grid. This approach improves waveform matching reliability by preparing the system in advance, while the control complexity is managed through standardized precharge sequences.
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 enables efficient power conversion with power factor correction, achieving sinusoidal output currents that match the grid voltage waveform, thereby optimizing power transfer and reducing harmonic distortion.
Implementation Method 1
a transformer (2) coupled between the output of the input stage and the input of the at least one resonant converter stage
Implementation Method 2
at least one resonant converter stage (3a, 3b, 3c) having an input and an output
Data Source
Figure 1
Figure 2~5
Figure 6
AI summary
A power converter, a control circuit for controlling a power converter, and a method for operating a power converter are disclosed. The power converter includes an input stage (1) including an input (11, 12) configured to receive an input voltage (Vin), and an output (13, 14); at least one resonant converter stage (3a, 3b, 3c; 3d) including an input (Ina, Inb, Inc; Ind) and an output (Outa, Outb, Outc; Outd) configured to be coupled to a power grid; a transformer (2) coupled between the output (13, 14) of the input stage (1) and the input (Ina, Inb, Inc; Ind) of the at least one resonant converter stage (3a, 3b, 3c; 3d); and a control circuit (7) configured to control operation of the input stage (1) and the at least one resonant converter stage (3a, 3b, 3c; 3d). The input stage (1) includes a switching circuit (15) connected to the input (11, 12) of the input stage (1) and at least one capacitor (16) connected between the switching circuit (15) and the output (13, 14) of the input stage (1).