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Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching for all switches and zero current switching for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30 V renewable energy source, 48 V energy storage device and 400 V output is designed to verify the performance of the proposed three-port converter. [ABSTRACT FROM AUTHOR]

Average small-signal model, known as a simple and powerful tool, is widely used to provide design guidance for switching converters. Due to the ignorance of high-frequency characteristics, conventional average small-signal model fails to reveal dynamics of switching converters with ripple-based control. Improved small-signal models for ripple-based controls, including peak and valley ripple-based controls, are proposed in this article, which can be accurate to half of the switching frequency. Specifically, as for peak or valley current control, the uniform gain representing sample-and-hold effect is derived and suitable for different averaging ways. With regard to V2 control, the improved small-signal model can predict subharmonic oscillation caused by duty cycle and reveal the influence of the equivalent series resistance of output capacitor. Moreover, by combining the improved small-signal models of ripple-based current-mode control and V2 control, small-signal model of V2C control can be analyzed. The relationship among these ripple-based control methods is revealed, and the stability analysis as well as the transient response is carried out. Finally, experimental results turn out to agree well with the theory analysis. [ABSTRACT FROM AUTHOR]

Recently, it has been reported that valley V2 control can be applied to boost converters. However, the actual transient performance and design methodology are not clear due to insufficient knowledge about its small signal model. In this article, a small signal model of valley V2 controlled boost converter is proposed by combining average method and sampled-data method, which is simple and accurate to half the switching frequency. Then, design guidance focused on dynamical performance and stability is provided. Moreover, compensator for the valley V2 controlled boost converter is discussed. The proposed small signal model and design guidelines are verified with experimental results. Results first indicate that for the valley V2 controlled boost converter, the inductor current information is contained in the control loop because of the discontinuous output voltage ripple, which is totally different from that in V2 controlled buck converter. Also, the equivalent series resistance as well as the duty ratio will affect the transient performance to some extent. Moreover, just by using the simple proportional integral compensator, the valley V2 controlled boost converter can be compensated, and it possesses fast transient performance. As for the stability issues, the ramp compensation is useful to eliminate the instability, improving the stability margin. [ABSTRACT FROM AUTHOR]

This article proposes a two-mode active balancing circuit for series-connected cell strings. The proposed balancing circuit has two operation modes: any cell to any cell (AC2AC) and direct cell to cell (DC2C) modes. In AC2AC mode, the balancing circuit can be equivalent to an improved switched-capacitor (SC) balancing circuit, and the energy is transferred among all imbalanced cells, implementing the higher balancing speed when the voltage gap between cells and the number of imbalanced cells are large. In DC2C mode, the proposed balancing circuit can be equivalent to a balancing circuit based on three-resonant-state LC unit, and the energy is transferred from the highest voltage cell to the lowest voltage one, achieving the higher balancing efficiency and speed as well as accuracy when the voltage gap between cells is small. The operation state, balancing power, and balancing efficiency of each mode are analyzed in detail. The control strategy and design considerations of the balancing circuit are introduced to obtain the optimal balancing performance. Experimental results are provided to verify the validity of the proposed balancing circuit. The results show that the proposed balancing circuit achieves high balancing accuracy and efficiency as well as balancing speed. [ABSTRACT FROM AUTHOR]