Modeling and Decoupled Control of a Buck-Boost and Stacked Dual Half-Bridge Integrated Bidirectional

Abstract

The modeling and control of a buck-boost and stacked dual half-bridge (DHB) integrated bidirectional dc-dc converter (BDC) have been studied in this paper. This converter features high voltage transfer ratio, high efficiency, and the minimum number of switches. In this paper, an extended, continuous, full order, state-space averaging modeling method is proposed. Compared with existing methods, the proposed method exhibits higher coincidence with the switching circuit simulation, in steady and especially dynamic states. Due to its high dynamic accuracy and low complexity, the proposed modeling method provides a better theoretical analysis and fast simulation tool for transient process and control design of converters with dual-active-bridge (DAB) units, especially with DHB units. By using this method, the high-frequency transformer series inductance current is directly divided into a sampled dc component and a fluctuant component. Only the sampled dc one is included into state variables. But both components are considered into state equations. Besides, this method regards the entire converter as a linear superposition of its subsections, which provides a stepwise modeling based on linearization of subsections. Moreover, a decoupled proportional-integral control method is proposed to enhance the stability and dynamic response of the converter. This control method is analyzed by the proposed models, which can be regarded as an application of the proposed modeling method.

Existing System

Step-Up/Step-Down Soft-Switching Bidirectional DC–DC Converter

Proposed System

This paper focuses on developing an extended, continuous, full order, state-space averaging modeling method. The proposed modeling method is for converters with phase shift plus duty cycle control. A converter BB-SDHB BDC is modeled by the proposed modeling method. Both nonlinear large-signal model and linear small-signal model are established. These two mathematic models highly coincide with switching circuit simulation in both steady and dynamic states. Experimental results validate the correctness and accuracy of the proposed modeling method. Simulation comparison with two existing advanced modeling methods also shows the higher accuracy of the proposed one. Due to its high dynamic and steady accuracy and low complexity, the proposed modeling method provides a better theoretical analysis and fast simulation tool for transient process and control design of converters with DAB units, especially with DHB units. A decoupled control strategy is also proposed to achieve better control stability of the VM-SDCT BDCs. For the BB-SDHB BDC, the effectiveness of this control strategy is analyzed based on the proposed model, which is also an application of this modeling method.

Architecture

Derivation of topology - VM-SDCT BDC

BB-SDHB BDC