Reconfigurable AC/DC Converter for Single- and Three-Phase PFC
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Solution Overview
Problem
Existing three-phase/single-phase compatible AC/DC converters struggle to operate efficiently under non-unity power factor conditions, leading to issues such as low output power and long charging times in electric vehicles, and they lack the capability to provide reactive power compensation, which is increasingly required by modern electric grids.
Innovation Solution
The proposed solution involves a three-phase/single-phase compatible AC/DC converter that includes relays and additional switches, allowing it to operate as a totem-pole power factor correction converter with a single-phase input, and employs a T-type leg configuration to enable non-unity power factor operation by switching at AC zero crossings, using low-cost diodes to reduce cost and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional boost converter topology is used for AC/DC conversion, then sinusoidal input current and unity power factor are achieved, but the converter cannot operate under non-unity power factor conditions and lacks reactive power compensation capability
Solution Approach 1:
The patent applies universality by designing a converter that can operate in multiple modes: unity power factor mode, non-unity power factor mode, and reactive power compensation mode. The same hardware topology supports all these functions through controlled switching of the T-type leg and diagonal switches, eliminating the need for separate converters for different operating conditions.
Solution Approach 2:
The patent implements dynamics by making the converter topology reconfigurable through switching elements. The T-type leg and diagonal switches can be dynamically activated or deactivated based on the desired operating mode, allowing the converter to adapt its structure in real-time to meet different power factor requirements and provide reactive power compensation when needed.
2Adaptability or versatility
If three-phase input is used for high power applications, then power delivery is improved, but the converter cannot operate with single-phase input for home charging scenarios
Solution Approach 1:
The patent achieves universality by designing a single converter topology that accepts both three-phase and single-phase inputs. The converter uses three bridge legs with diagonal switches that can be configured to handle three-phase input or single-phase input by selectively enabling or disabling specific switching paths, making the system adaptable to different input scenarios without requiring separate hardware designs.
Solution Approach 2:
The patent applies segmentation by dividing the converter into three independent bridge legs, each with its own switching elements. This modular structure allows the converter to process three-phase input using all three legs simultaneously or single-phase input by activating only the necessary legs, providing flexibility in input configuration while maintaining a unified overall architecture.
3Adaptability or versatility
If reactive power compensation capability is added to meet future grid requirements, then grid compatibility is improved, but the converter complexity and control difficulty increase
Solution Approach 1:
The patent implements universality by integrating reactive power compensation capability into the existing converter topology. The same T-type leg and diagonal switches used for power factor correction are also employed for reactive power compensation, allowing the converter to provide both active and reactive power support to the grid using a unified control framework, thereby avoiding the need for separate compensation equipment.
4Productivity
If EV battery capacity increases for longer range, then vehicle performance is improved, but charging time increases significantly with conventional 7-kW OBC
Solution Approach 1:
The patent applies the skipping principle by enabling the OBC to operate at higher power levels when three-phase input is available. The converter topology efficiently handles high-power three-phase input by utilizing all three bridge legs in parallel, allowing the system to 'skip' through the charging process faster by accepting and processing higher power input, thereby reducing charging time for large-capacity batteries.
Data Source
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AI summary
The present disclosure provides a three-phase/single-phase compatible AC/DC converter (52, 118) and a control method. The three-phase/single-phase compatible AC/DC converter (52) includes plural relays (RL1, RL2, and RL3) that, when selectively activated or deactivated, enables operation as a three-phase converter or a totem-pole power factor correction (PFC) converter (56) with a single-phase input, the totem-pole PFC converter having a parallel arrangement of a diode leg (68) and slow leg (66) connected at their respective midpoints to neutral so as to operate in unity power factor or non-unity power factor. The method includes: operating plural fast legs (60, 62) at a first duty cycle for a period defined by a predefined range of an input voltage, and at least a second duty cycle outside of the period different than the first duty cycle for non-unity power factor cases; and increasing a switching frequency of the slow leg (66) during the period while in non-unity power factor operation.