Active power decoupling methods are developed to deal with the inherent ripple power at twice the grid frequency in single-phase systems generally by adding active switches and energy storage units. ...They have obtained a wide range of applications, such as photovoltaic (PV) systems, light-emitting diodes (LEDs) drivers, fuel cell (FC) power systems, and electric vehicle (EV) battery chargers, etc. This paper provides a comprehensive review of active power decoupling circuit topologies. They are categorized into two groups in terms of the structure characteristics: independent and dependent decoupling circuit topologies. The former operates independently with the original converter, and the latter, however, shares the power semiconductor devices with the original converter partially and even completely. The development laws for the active power decoupling topologies are revealed from the view of "duality principle," "switches sharing," and "differential connection." In addition, the exceptions and special cases are also briefly introduced. This paper is targeted to help researchers, engineers, and designers to construct some new decoupling circuit topologies and properly select existing ones according to the specific application.
Bulky electrolytic capacitor is usually needed in bridgeless power factor correction rectifiers to buffer the double-frequency ripple power (DFRP). However, it reduces the system reliability and ...power density significantly. This letter proposed a control method to divert DFRP to the small energy transfer capacitor. Then, the bulky electrolytic capacitor can be replaced with a small film capacitor. The proposed method is realized by making the best of the existing switching states. Therefore, it needs no extra switches or energy storage components, which are usually required in other active power decoupling methods. The operating principle is explained, and a closed-loop control strategy is proposed. Finally, the effectiveness is verified by experimental results.
The active power-decoupling (APD) method is an effective solution to handle the inherent double-line frequency ripple power in single-phase power systems. It removes the bulky passive devices and ...facilitates the improvement of the system power density and even the reliability. This article provides a comprehensive review of the prior-art and state-of-the-art control strategies in APD. They are categorized into four groups according to the basic control ideas of "power balance," "harmonic suppression," "volt-second balance/charge balance," and "virtual impedance." And the specific control strategies under each control idea are discussed and compared. The pros and cons of each control idea are also presented . Finally, this article draws a sketch of the global trends in APD control.
This paper proposes an active power decoupling method without adding additional active switches for single-phase current source rectifiers. Two identical decoupling capacitors connected across the ...two bridge arms operate alternatively to buffer the ripple power at twice the line frequency. First the operational principle of the proposed circuit is presented. Thereafter, a hybrid modulation method, in which input current synthesis and ripple power buffering can be carried out simultaneously, is developed. Moreover, a new effective closed-control strategy is presented, in which the decoupling control is responsive for regulating dc-link current and the rectification control is in charge of power factor correction as well as maintaining the dc component of the decoupling capacitor voltages at a given level. Consequently, complete ripple power decoupling is achieved and sine input current is obtained. Finally, the theoretical analysis is favorably verified by the simulations and experimental results.
Cable-stayed bridges have been commonly used on high-speed railways. The design, construction, and maintenance of cable-stayed bridges necessitate an accurate assessment of the cable temperature ...field. However, the temperature fields of cables have not been well established. Therefore, this research aims to investigate the distribution of the temperature field, the time variability of temperatures, and the representative value of temperature actions in stayed cables. A cable segment experiment, spanning over one year, is conducted near the bridge site. Based on the monitoring temperatures and meteorological data, the distribution of the temperature field is studied, and the time variability of cable temperatures is investigated. The findings show that the temperature distribution is generally uniform along the cross-section without a significant temperature gradient, while the amplitudes of the annual cycle variation and daily cycle variation in temperatures are significant. To accurately determine the temperature deformation of a cable, it is necessary to consider both the daily temperature fluctuations and the annual cycle of uniform temperatures. Then, using the gradient boosted regression trees method, the relationship between the cable temperature and multiple environmental variables is explored, and representative cable uniform temperatures for design are obtained by the extreme value analysis. The presented data and results provide a good basis for the operation and maintenance of in-service long-span cable-stayed bridges.
Two modulation strategies based on carrier-based modulation (CBM) scheme (named RCMV-CBM1 and RCMV-CBM2) are proposed to reduce the common-mode voltage (CMV) of a five-phase voltage source inverter. ...The basic characteristic of them is that two kinds of carriers with opposite phase are adopted. By applying the opposite carrier to some specific phases, the switching states with higher CMV absolute value can be avoided. In RCMV-CBM1, the output phase with the third largest modulated signal uses the opposite carrier, and the peak-to-peak value of CMV is reduced by 40%. In RCMV-CBM2, the output phases with the second largest and fourth largest modulated signals use the opposite carrier, and the peak-to-peak value of CMV is decreased by 80%. However, the ripple analysis reveals that RCMV-CBM1 has an advantage over RCMV-CBM2 in current quality. In addition, the optimized RCMV-CBM1 and RCMV-CBM2 are presented for reducing the output current ripple. Finally, a scaled-down prototype is built to verify the correctness and effectiveness of the proposed modulation strategies.
Sheppard-Taylor power factor correction (ST-PFC) rectifier could obtain a high power factor due to its capability of overcoming the control detuning issue. However, it needs a bulky electrolytic ...capacitor at the load side to buffer the double-frequency ripple power (DFRP), which reduces the reliability and power density significantly. This paper proposes a control method to divert the DFRP to the small energy transfer capacitor. Consequently, the bulky electrolytic capacitor is replaced with a small film capacitor. The proposed method is carried out by introducing the freewheel state (one switch is turned on and the other is turned off) into the control. So no extra hardware is added, which makes the proposed method cost-effective. A low electromagnetic interference emission is also achieved due to the continuous input-output currents. In addition, the proposed method can be extended to other topologies easily. This paper first gives the detailed analysis of the proposed control method, and then introduces the controller design. The selection of the passive components is also briefly discussed. Finally, the simulation and experimental results verify the effectiveness of the proposed control method.
Although ionic liquids have been studied as self-assembly media, the aggregation of fluorinated surfactants in ionic liquids has not been fully understood. In this work, the aggregation behavior of ...the fluorinated surfactant, N-ethylperfluorooctane sulfonamide (N-EtFOSA), in the aprotic ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate (C
2
mimEtSO
4
), was studied using surface tension,
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F-NMR, dynamic light scattering (DLS), and cryo transmission electron microscopy (cryo-TEM). The surface properties and thermodynamic parameters were calculated based on the results of surface tension measurements. It was found that the fluorinated surfactant exhibits a considerable surface activity in aprotic ionic liquids, and its critical micelle concentration (cmc) increases with increasing temperature. In addition, the surface properties indicate that solvophobic interactions are the main driving force for micelle formation. The thermodynamic parameters for micelle formation derived from the temperature dependence of the cmc revealed that micelle formation is an enthalpy-driven process. DLS and cryo-TEM results indicated the presence of nanoscale micelles in the N-EtFOSA + C
2
mimEtSO
4
system. The results of this work imply that this fluorinated surfactant exhibits a more pronounced surface activity than conventional hydrocarbon surfactants in C
2
mimEtSO
4
.
Graphical abstract
The self-assembly of fluorinated surfactants in aprotic ionic liquids
Aiming to handle the inherent double-line frequency ripple power in single-phase power systems, a lot of active power decoupling (APD) topologies have been developed. In this paper, a general method ...is introduced to synthesize APD topologies. The main construction idea is to insert a rectifier/inverter into asymmetrical H-bridge circuits (AHCs) or replace the switch/diode in the AHCs with a rectifier/inverter. This approach not only reveals the formation process of existing APD topologies but also deduces new APD topologies. Finally, an experimental case study has been carried out to illustrate the feasibility and effectiveness of the proposed topology synthesis method.
This paper shows main characteristic of a multi-component calibration device as well as the working modes. The calibration device can generate continuous and combined load covering three forces of ...Fz, Fx, Fy and two moments of My, Mz, as well torque Mz. The emphasis is on mechanical design and simulation analysis of the device, which includes a main frame, a system generating reference load cells and piston-cylinder systems. The flexibility units have been specially designed to reduce the mutual influence between components generated. The performance verification results are given at the end of the article.
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