Sensorless DAB PFC Control via Phase Shift Coordination
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Solution Overview
Problem
Current single-stage isolated PFC converters face challenges in controlling input current sinusoidally without increasing system complexity and cost, particularly in high-frequency and high-power density applications, due to the need for inner current loop controllers which reduce bandwidth and complicate control system design.
Innovation Solution
A current sensorless control system for DAB-based single-stage isolated PFC converters that uses a diode rectifier circuit, DAB converter power main circuit, EMI filter, and a digital controller with A/D sampling, PI controller, and modulation unit to directly control input current without an inner current loop, reducing system complexity and cost while improving dynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an inner current loop controller is added to control input current sinusoidally, then the input current waveform can be controlled to be sinusoidal, but the bandwidth of the system is reduced and the difficulty of control system design is increased
Solution Approach 1:
The patent extracts and removes the inner current loop controller from the control system. Instead of using a traditional two-loop control structure with inner current loop and outer voltage loop, the invention uses only the outer voltage loop to directly control the DAB converter's phase shift, thereby eliminating the complexity associated with inner loop current control while still achieving sinusoidal input current through the voltage loop's reference signal design
Solution Approach 2:
The outer voltage loop controller is designed to perform multiple functions: it not only regulates the output voltage but also directly controls the input current waveform shape through the DAB converter's phase shift control. This multi-functional approach eliminates the need for a separate inner current loop controller, reducing system complexity while maintaining both voltage regulation and current waveform quality
2Manufacturing precision
If an inner current loop controller is added to control input current sinusoidally, then the input current waveform can be controlled to be sinusoidal, but the bandwidth of the system is reduced
Solution Approach 1:
By removing the inner current loop controller, the patent eliminates the bandwidth limitations imposed by nested loop structures. The single outer voltage loop operates without being constrained by an inner loop's bandwidth requirements, thereby maintaining higher system bandwidth while still achieving accurate input current waveform control through direct phase shift modulation of the DAB converter
3Manufacturing precision
If traditional PFC control method is used with inner current loop, then input current sinusoidal control is achieved, but the cost of control system is increased
Solution Approach 1:
The patent removes the inner current loop controller hardware and associated current sensors, thereby reducing the cost of the control system. The solution achieves input current sinusoidal control using only the outer voltage loop controller and the existing DAB converter structure, eliminating the need for additional control components and current sensing infrastructure
Data Source
AI summary
A current sensorless control system and a control method thereof for single stage isolated PFC converters based on DAB. By coordinating three control variables of the DAB converter, that is, the inside phase-shifting ratio of the primary side full-bridge, the inside phase-shifting ratio of the secondary side full-bridge, and the phase-shifting ratio between the primary and the secondary sides, the present invention does not need to design additional current controller for the control of the input current, and may make the input current sinusoidal by directly coordinating the output voltage controller, the input voltage and the current modulation step, thereby reducing system cost and the difficulty of controller design, enhancing the stability of the control system, and improving the dynamic performance.