DAB Power Converter Control for Discontinuous Reactor Current
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Solution Overview
Problem
The existing CF-DAB circuit experiences issues with power transmission failure during charging and discharging due to the introduction of a current discontinuity mode, which leads to increased conduction loss and inefficient power conversion, particularly at low outputs.
Innovation Solution
A power converter design that includes a first and second bridge with series-connected switching elements, a transformer, and reactors, controlled by a circuit to manage reactor current in a discontinuous current mode, ensuring power transmission through the DAB circuit by adjusting the ON periods of switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching of power devices is stopped to achieve current discontinuity mode, then conduction loss is reduced, but power transmission operation cannot be performed
Solution Approach 1:
The patent divides the switching control into separate phases: the boost circuit switching elements are stopped to achieve current discontinuity mode and reduce conduction loss, while the DAB circuit switching elements continue to operate to maintain power transmission function. This segmentation allows each circuit to operate independently with optimized switching strategies.
Solution Approach 2:
The patent dynamically adjusts the switching states of different circuit components based on operational requirements. The boost circuit switching elements are dynamically stopped during certain phases to reduce losses, while the DAB circuit switching elements are dynamically controlled to ensure continuous power transmission capability.
2Loss of energy
If boost circuit operates in discontinuous current mode, then power conduction loss is reduced, but switching of DAB circuit power devices also stops
Solution Approach 1:
The patent segments the power conversion function into two independent control systems: the boost circuit control system that operates in discontinuous current mode to reduce conduction loss, and the DAB circuit control system that maintains continuous switching to ensure power transmission. This allows the boost reactor current to be discontinuous while the DAB circuit continues to transmit power effectively.
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
Improves power conversion performance by maintaining power transmission while reducing conduction loss, especially at low outputs, by controlling reactor current in a discontinuous current mode.
Implementation Method 1
a transformer (30) including a primary winding (30p) and a secondary winding (30s), the primary winding (30p) being connected to a plurality of the intermediate nodes of the first legs, the secondary winding (30s) being connected to a plurality of the intermediate nodes of the second legs and magnetically coupled to the primary winding (30p)
Data Source
AI summary
In a DAB circuit including a first bridge and a second bridge, a boost circuit is shared by connecting reactors between a storage battery and the first bridge. In each leg of the first bridge, in order to increase an absolute value of a reactor current, an ON period of one switching element of a switching element on a high voltage side and a switching element on a low voltage side is provided, and then, an ON period of the other switching element is provided. An ON period length of the one switching element is set according to a control command value of a DC voltage input to the first bridge. An ON period length of the other switching element is set to a time length until an absolute value of the reactor current that has increased during the ON period of the one switching element returns to zero.