Power Transmission Unit Duty-Cycle Control for Small Inductor Current
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Solution Overview
Problem
Existing power transmission units (PTUs) in fuel cell systems face challenges in achieving stable small current control, particularly when operating in buck-boost mode, due to the influence of duty cycles on the current through inductive elements.
Innovation Solution
A power transmission unit is designed with a first and second switch, each operating at different duty cycles, and an inductive element connected between them. A controller determines a total duty cycle based on actual and desired phase currents and adjusts the duty cycles to achieve small current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a non-complementary buck-boost control method is used to reduce phase current ripple and decrease phase inductance value, then the current control stability is improved, but the device complexity increases due to the need for multiple switches operating at different duty cycles
Solution Approach 1:
The control method segments the duty cycle control into two independent duty cycles (first duty cycle for first switch, second duty cycle for second switch) instead of using a single unified duty cycle. This segmentation allows independent optimization of each switch's operation to reduce current ripple while maintaining manageable device complexity through systematic control.
Solution Approach 2:
The control method dynamically adjusts the duty cycles of the first and second switches based on real-time current feedback. The controller continuously modifies the duty cycle values to maintain optimal current control stability, adapting to changing operating conditions while managing device complexity through dynamic rather than static control.
2Stability of the object's composition
If the second duty cycle is made less than the first duty cycle in buck-boost mode, then the phase current ripple is reduced, but the control system complexity increases
Solution Approach 1:
The control method applies different duty cycle characteristics to different parts of the control system - the first switch operates at a first duty cycle while the second switch operates at a second duty cycle that is less than the first. This local differentiation of control parameters reduces phase current ripple by creating asymmetric switching patterns tailored to each switch's position in the circuit.
Data Source
AI summary
A power transmission unit and a method for controlling the current flowing through it are disclosed. The power transmission unit includes a first switch which is turned on and off at a first duty cycle; a second switch which is turned on and off at a second duty cycle that is less than the first duty cycle; an inductive element connected between the first switch and the second switch, with its current associated with the first and second duty cycles; and a controller configured to determine a total duty cycle as the sum of the first and second duty cycles based on an actual phase current and a desired phase current of the inductive element, and to adjust the first and second duty cycles based on the determined total duty cycle. Embodiments of the present disclosure adjust both the first and second duty cycles through the total duty cycle, which changes with the total duty cycle, allowing both the first and second duty cycles to be adjusted to appropriate values. This ensures that the current flowing through the inductive element reaches an appropriate value, thereby enabling small current control.