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Andrographolide (Andr) is a bioactive Andr diterpenoid extracted from herbaceous Andrographis paniculata (Burm. F.) Wall. ex Nees (Acanthaceae). Andr can relieve cardiac dysfunction in mice by inhibiting the mitogen-activated protein kinases (MAPK) pathway. This study investigates the efficacy and underlying mechanism of Andr on cardiac hypertrophy in mice. Male C57 mice (20–25 g, 6–8 weeks) were divided into four groups (n = 10 mice/group) as sham group (sham operation), transverse aortic constriction (TAC) model group, TAC + Andr 100 mg/kg group and TAC + Andr 200 mg/kg group. Andr groups were given intragastric administration of Andr (100 and 200 mg/kg) once a day for 14 consecutive days. An in vitro hypertrophy model was established by adding 1 μM of Ang II to H9c2 cells for 48 h induction. In TAC-mice, Andr improved echocardiographic indices [reduced LVESD (30.4% or 37.1%) and LVEDD (24.8% or 26.4%), increased EF (22.9% or 42.6%) and FS (25.4% or 52.2%)], reduced BNP (11.5% or 23.6%) and Ang II levels (10.3% or 32.8%), attenuates cardiac fibrosis and reduces cardiac cell apoptosis in TAC mice. In vitro, Andr attenuated cardiomyocyte hypertrophy and decreased the protein expression of GRP78 (67.8%), GRP94 (47.6%), p-PERK (44.9%) and CHOP (66.8%) in Ang-II-induced H9c2 cells and reversed after endoplasmic reticulum (ER) stress agonist Tunicamycin (TN) treatment. Andr was found to be an anti-hypertrophic regulator, which could attenuate cardiac hypertrophy by suppressing ER stress. It may be a new therapeutic drug for cardiac hypertrophy. [ABSTRACT FROM AUTHOR]

A series of three-port forward converters with a compact structure and extended duty cycle range is presented for the standalone renewable energy system. Bidirectional power-flow port embedding and switch device sharing can be used to derive these converters from conventional two-switches forward converters. In comparison to the conventional two-switch forward converter, only one switch and one diode are added to build an energy storage port with bidirectional power flow characteristics, which has the benefits of compact structure and low cost. Meanwhile, the embedding of the energy storage port provides an additional demagnetization loop for the magnetic inductor, which extends the duty cycle range of the forward converter so that the proposed converter no longer requires a duty cycle of less than 0.5 as in the case of conventional forward converters. The proposed converters also offer the advantages of fewer components, easy control, and independent control of power flow between multiple ports when compared to similar solutions. Finally, an experimental setup with a photovoltaic battery as an application is developed, and the experimental results verify the effectiveness and flexibility of the proposed topology and control method. [ABSTRACT FROM AUTHOR]

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]

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]

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]

For a photovoltaic (PV)/battery power system consisting of PV module, energy storage system, and local load, using a three‐port converter (TPC) instead of several single‐input converters is more desirable, such as simpler circuit, higher efficiency, lower cost, and centralized control without communication circuit. In this paper, a TPC is proposed and analyzed, which includes operating modes, steady‐state performance, and parameter design. Compared with other converters, the proposed TPC has a low cost, compact structure, and a more flexible voltage relationship among all ports. Moreover, energy management and control methods are further proposed for PV/battery systems based on the proposed converter, which can achieve maximum power point tracking (MPPT) of PV module and constant output voltage. In order to design the control loop and realize multivariable optimal control, a small‐signal model of the converter is obtained in each operation mode. Then a detailed decoupling design approach based on a small‐signal model is provided to allow a separate controller design for the proposed converter. Finally, the validity of the proposed converter and its energy management and control method are verified by experimental results. [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]

A bipolar dc microgrid is desirable as it enhances the system reliability and efficiency. However, the conventional bipolar dc microgrid requires multiple dc–dc converters to feed the power to the load, which leads to large volume and weight and high cost. In this article, a novel four-port converter is proposed to integrate photovoltaic (PV) module and battery to the bipolar dc microgrid system, realizing the single-stage energy conversion. The main advantages of this converter are that three switches are used to realize PV generation, battery charging and discharging, as well as symmetrical bipolar output voltage, and all input ports and output ports share the common reference ground. Depending on relationships between the energies of the source and the load, three different operation modes are defined. Then, the detailed parameter design is provided by analyzing different operation modes of the converter. Energy management and control strategies of the bipolar dc microgrid using this converter are explained in detail. Finally, experimental verifications are given to illustrate the feasibility and effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

A current sensor based global maximum power point tracking (GMPPT) algorithm of photovoltaic system is proposed in this article to increase the tracking speed during partial shading condition. For the proposed algorithm, the tracking range of duty cycle is reduced by calculating both the upper limit and lower limit of duty cycle and skipping the duty cycle section without global maximum power point. Compared with maximum power trapezium (MPT) algorithm and the combination algorithm of MPT and search-skip-judge, the proposed algorithm reduces the tracking range of duty cycle during both tracking directions and only needs one current sensor to realize control. As a result, the proposed algorithm shows advantages of fast tracking speed, small energy loss, and low hardware cost. Followed by theoretical analysis, the simulation and experimental evaluation validate the claimed advantages of the proposed GMPPT algorithm. [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]