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A multiport converter with bipolar outputs to integrate renewable energy and energy storage into the bipolar dc bus is the desirable solution due to its high reliability and efficiency. A novel symmetric bipolar outputs full-bridge four-port converter based on phase-shift modulated buck–boost voltage balancer is proposed in this article. The interleaved bidirectional buck/boost circuit with pulsewidth modulation is used as the primary side to achieve the integration of renewable energy and energy storage, whereas the phase-shift modulated buck–boost voltage balancer is derived as a secondary side circuit to generate a symmetrical and common ground bipolar output voltage. Single-stage power conversion, symmetrical bipolar output voltage, approximately decoupled control loop, and soft switching can be realized in the proposed four-port converter. Detailed analysis of the proposed converter is presented, including operation principle, steady-state performance, soft switching performance, and control method. Finally, experimental verifications are carried out to illustrate the feasibility and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

Using a multiport converter to integrate renewable energy and energy storage into the bipolar dc bus is a desirable solution due to its high efficiency and reliability. In this article, a series of bipolar output active rectifiers with center-tapped winding is proposed to serve as secondary rectification circuits. Then, a family of isolated four-port converters with symmetrical bipolar outputs is further developed to integrate renewable energy and energy storage. The proposed symmetrical bipolar output isolated four-port converters can achieve single-stage power conversion, symmetrical bipolar output voltage, soft switching, and decoupled control. A typical four-port converter, named full-bridge interleaving bidirectional buck/boost + semiactive rectifier with bipolar output converter, is specifically analyzed in detail in terms of operation principles, voltage and power relationship, port current ripples, soft switching performance, and control. Finally, experimental tests have been performed to verify the feasibility and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

In the standalone renewable energy system, a multiport converter is more desirable than several single-input converters as it has advantages of a simpler circuit, higher efficiency, and lower cost. This article proposes a novel topology synthesis method to derive integrated three-port converters with low cost and compact structure. With the proposed topology synthesis method, integrated three-port converters can be easily developed from conventional single-input single-output (SISO) converters by replacing a switch and a diode with a basic cell, including bidirectional power flow. Compared with the SISO converter, the derived integrated three-port converters only need to add the extra switch and diode, which makes them have low cost and compact structure. As an example, topology synthesis based on buck, boost, buck–boost, Cuk, SEPIC, and zeta converters is performed in this article. The proposed topology synthesis method can also be extended to deduce a series of n-port converters. In order to achieve a better understanding of the proposed converters, the integrated three-port SEPIC converter is specifically analyzed, including its operation principle, steady-state performance, small-signal modeling, and control system. Finally, experimental verifications have been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method. [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]