T-Type Totem-Pole PFC Converter for Non-Unity Power Factor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power factor correction converters in electric vehicle on-board chargers struggle to operate efficiently under non-unity power factor conditions, leading to issues with reactive power compensation and harmonic distortion, which are becoming increasingly important as renewable energy sources integrate into the electrical grid.
Innovation Solution
A totem-pole power factor correction converter with a T-type leg configuration, utilizing active switches to switch near AC zero crossings, enabling non-unity power factor operation and reactive power compensation, while maintaining low cost and control complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional boost converter is used to achieve unity power factor operation, then low harmonic distortion is achieved, but the converter cannot operate efficiently under non-unity power factor conditions and lacks reactive power compensation capability
Solution Approach 1:
The patent implements dynamic switching of the T-type leg near AC zero crossings, allowing the converter to adapt its operating mode between unity and non-unity power factor operations. This dynamic control enables the system to switch between different power factor modes based on grid requirements, achieving both low harmonic distortion during unity PF operation and reactive power compensation during non-unity PF operation
Solution Approach 2:
The converter is designed with multi-functionality to handle both unity and non-unity power factor operations using the same T-type totem-pole topology. The T-type leg with active switches provides universal operation capability, enabling the converter to perform both PFC and reactive power compensation functions without requiring separate circuits
2Reliability
If reactive power compensation is implemented in existing PFC converters, then voltage regulation at point of connection is improved, but the converter complexity and control difficulty increase significantly
Solution Approach 1:
The patent merges the PFC function and reactive power compensation function into a single integrated T-type totem-pole converter. By combining these functions in one circuit topology with shared components (inductors, capacitors, and switches), the design avoids the complexity of separate PFC and reactive power compensation circuits, achieving voltage regulation capability without significant increase in device complexity
Solution Approach 2:
The T-type totem-pole converter is designed as a universal circuit that performs both PFC and reactive power compensation using the same hardware components. The active switches in the T-type leg serve dual purposes: shaping input current for PFC and providing reactive current for voltage regulation, thereby achieving multi-functionality without proportionally increasing device complexity
3Adaptability or versatility
If reactive power compensation is added to existing PFC converters, then grid support capability is improved, but the control complexity and difficulty increase significantly
Solution Approach 1:
The control method employs periodic switching of the T-type leg near AC zero crossings, synchronized with the grid voltage cycle. This periodic action simplifies the control by using zero-crossing detection as a timing reference, making it easier to implement reactive power compensation without requiring complex continuous control algorithms. The control complexity is reduced by leveraging the natural periodicity of the AC waveform
Solution Approach 2:
The converter implements feedback control by detecting the actual power factor and grid voltage conditions, then adjusting the switching duty cycle of the T-type leg accordingly. This feedback mechanism enables automatic adaptation to different operating conditions (unity or non-unity power factor) and simplifies the control by using measured quantities directly in the control algorithm, reducing the need for complex predictive or iterative control methods
Data Source
AI summary
The present disclosure provides a totem-pole PFC converter and a control method thereof. The totem-pole PFC converter includes: a plurality of phase legs connected in parallel; a plurality of boost inductors, wherein each boost inductor is connected between the corresponding input terminal and the midpoint of the corresponding phase leg; a plurality of capacitors; a diode leg connected with the plurality of phase legs in parallel, wherein the midpoint of the diode leg is connected with the neutral terminal; an output filter connected with the diode leg in parallel; a T-type leg connected between the midpoint of the diode leg and the midpoint of the output filter and including two active switches connected in series; and a control system configured to turn the two active switches on around AC voltage zero crossings during non-unity power factor operation.