Parallel Rectifier and PFC Converter for Unity Power Factor
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Solution Overview
Problem
Existing power conversion systems for electric vehicles face inefficiencies in converting AC power to DC power, particularly in achieving high efficiency and unity power factor, especially when dealing with varying battery capacities and voltages.
Innovation Solution
A power conversion system comprising a three-phase diode rectifier and a three-phase power factor correction converter operating at different frequencies, with an isolated LLC power converter, where the power factor correction device operates in triangular current mode and the LLC converter provides high efficiency by operating at its resonant frequency, distributing power through two routes to minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single power conversion device is used to convert AC power to DC power, then the device structure is simple, but the conversion efficiency is low and power factor cannot achieve unity
Solution Approach 1:
The power conversion system is divided into two separate power conversion devices: a first power conversion device for high-efficiency power conversion and a second power conversion device for power factor correction. This segmentation allows each device to be optimized for its specific function, achieving high conversion efficiency while maintaining unity power factor.
Solution Approach 2:
The second power conversion device acts as an intermediary between the AC power source and the first power conversion device. It corrects the power factor of the input current before it reaches the first device, enabling the overall system to achieve unity power factor while the first device maintains high conversion efficiency.
2Ease of operation
If power factor correction circuit is added to achieve unity power factor, then the power factor improves, but the system complexity and conduction losses increase
Solution Approach 1:
The system separates the power factor correction function into a dedicated second power conversion device, distinct from the main power conversion device. This allows the power factor correction circuit to be independently optimized and controlled, achieving unity power factor without compromising the simplicity of the main power conversion path.
Solution Approach 2:
The second power conversion device is designed to handle only the necessary portion of power for correction purposes, rather than processing the entire power load. This partial action approach minimizes the impact on system complexity and conduction losses while achieving the desired power factor improvement.
3Loss of energy
If traditional AC/DC conversion method is used, then the system structure is simple, but conversion efficiency is low especially when dealing with varying battery capacities and voltages
Solution Approach 1:
The first power conversion device employs dynamic control strategies that allow it to adapt its operating parameters in real-time according to varying battery capacities and voltages. This dynamic adaptation maintains high conversion efficiency across different operating conditions without requiring complex reconfiguration of the overall system architecture.
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 system achieves high efficiency and unity power factor by distributing power primarily through a diode rectifier and a fraction through a power factor correction device, reducing conduction losses and ensuring efficient charging of electric vehicle batteries.
Implementation Method 1
the LLC converter provides high efficiency by operating at its resonant frequency
Implementation Method 2
a first rectifier coupled to a three-phase power source and is configured to operate at a first operating frequency
Implementation Method 3
The power factor correction circuit may be implemented in a suitable power converter such as a boost converter. By employing an appropriate control circuit, the boost converter is capable of shaping the input line current to be sinusoidal and in phase with the sinusoidal input voltage of the AC input source.
Implementation Method 4
an isolated power converter connected to output terminals of the three-phase diode rectifier. The isolated power converter comprises a primary network, a transformer and a secondary network
Data Source
AI summary
A power conversion system includes a first rectifier and a second rectifier. The first rectifier is configured to operate at a first operating frequency. The first rectifier is configured to be connected with a three-phase power source. A first amount of power flows through the first rectifier from the three-phase power source. The second rectifier is configured to operate at a second operating frequency. The second rectifier is configured to be connected in parallel with the first rectifier, and a second amount of power flows through the second rectifier from the three-phase power source. The second operating frequency is higher than the first operating frequency, and the second amount of power is a fraction of the first amount of power.