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This paper proposes optimized control methods for global minimum backflow power based on a triple-phase-shift (TPS) control strategy. Three global optimized methods are derived to minimize the backflow power on the primary side, on the secondary side and on both sides, respectively. Backflow power transmission is just a portion of non-active power transmission in a dual active bridge (DAB) converter. Non-active power transmission time is proposed in this paper, which unifies zero power transmission and backflow power transmission. Based on the proposed index, an optimized control method is derived to achieve both the maximum effective power transmission time and minimum current stress of DAB at the same time. A comparative analysis is performed to show the limitations of the minimum backflow power optimization method. Finally, a prototype is built to verify the effectiveness of our theoretical analysis and the proposed control methods by experimental results.

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Taking the hydraulic conversion system of the oscillating flapping-wing wave energy power generation device as the research object, a hydraulic conversion system is designed to convert wave energy into usable mechanical energy. Based on the principle of high-efficiency collection of wave energy and stable output of the hydraulic conversion system, the composition of the hydraulic conversion system and the parameters of each component are determined. According to different sea conditions, the pre-charge pressure of the accumulator is adjusted to keep the pressure of the high and low pipelines of the hydraulic system stable, and the mechanical energy is stably output through the hydraulic motor. The AMESim simulation platform is used to build the model of acquisition mechanism and hydraulic conversion system, simulate the motion response of acquisition mechanism under actual sea conditions as the system input, and analyze the effectiveness and output stability of hydraulic conversion system. The results verify that the designed hydraulic conversion system can achieve efficient collection of wave energy. The research results have laid a theoretical foundation for the development and research of wave energy power generation devices.

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This paper presents a novel topology and the coordinating control strategy of the hybrid cascade energy storage and bi-directional power regulation device. First, the voltage gain and power transmission characteristics of isolated half-bridge DC/DC converter have been analyzed. On this basis, the coordinating control strategy of the two kinds of converters is mainly studied. Finally, a detailed bi-directional power regulation device model is established on a PSCAD/EMTDC platform.

Aimed at the problem of extradosed cable-stayed bridges economic characteristics,studied extradosed cable-stayed bridges and cable stayed bridges data which has been built in China,statistics, induction, fitting the relation between the consumption of the main materials and the span,clear relationship between the cost and span, indicate that both consistent cost when the main span is 200 m ~ 320 m;Extradosed cable-stayed bridge is cheaper when the main span of less than 200m or more than 320m.

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