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It is well-known that the low-frequency negative input impedance of the constant power load (CPL) is the major cause of the cascaded system instability, and the heavier the power, the worse the stability. In this article, a power adaptive load-side parallel virtual impedance (PALPVI) control strategy is proposed to improve the stability of the cascaded dc system with buck-type CPL. First, a parallel impedance with power adaptability is derived followed up with the derivation of the corresponding compensation controller transfer function to realize it virtually. Considering that the compensation controller is highly dependent on the circuit parameters and needs extra current sensors to acquire the power information, a simplification of the compensation controller is made based on the open-loop characteristics of the buck-type CPL. The final PALPVI control strategy does not require the circuit parameters or any current sensor and has almost no side effect on the dynamic performance. Finally, a 48–24–12 V cascaded dc system is fabricated to verify the feasibility and effectiveness of the proposed PALPVI control strategy. [ABSTRACT FROM AUTHOR]

The dc distribution power system has drawn widespread attention and rapidly developed in recent years; however, its stability issue is one of the urgent challenges, requiring much attention. In previous stability studies, the line impedance network is often overlooked, which is convenient for the geographically centralized systems, but inaccurate for the distributed systems. In this article, the modeling and stability criteria of these two systems are simultaneously studied. For the distributed systems, first, the transfer functions from each input voltage or current disturbance to the bus voltage are derived. On this basis, the sufficient and necessary condition for the system stability is discussed. Subsequently, a bus node impedance criterion (BNIC) is proposed to assess the small-signal stability of the dc distribution power system. For the centralized systems, by ignoring the line impedance network, its small-signal model can be deduced by the distributed system, and the proposed BNIC is proved to be still valid. In addition, some existing impedance-based stability criteria are analyzed and compared with the proposed BNIC. Finally, the correctness and effectiveness of the proposed BNIC are verified by the cases study and experiments. [ABSTRACT FROM AUTHOR]

In order to effectively compensate negative sequence current (NSC) of the V/v traction system and reduce the capacity and cost of railway power conditioner (RPC), a low-cost hybrid railway power conditioner (HRPC) technology scheme considering regenerative braking energy is proposed in this paper. The proposed HRPC consists of an RPC with a modular multilevel converter structure (MMC-RPC) and a railway static var compensator (RSVC). First, the circuit topology of the proposed scheme and the principle of NSC compensation considering regenerative braking energy are given. Then, the capacity configurations of MMC-RPC and RSVC are presented to reduce the capacity of active equipment and further lower the investment cost of HRPC. On this basis, the HRPC with energy storage units (ESU-HRPC) is studied to recycle the remaining regenerative braking energy, and the difference from the proposed HRPC is further analyzed. Subsequently, the capacities of HRPC and ESU-HRPC are designed based on the measured power data from a heavy-haul railway in China as an example. Besides, the system control strategy is given. Finally, the proposed technical schemes are verified by the hardware in loop (HIL) experiments. [ABSTRACT FROM AUTHOR]

A plasma electrochemical method is used to synthesize cuprous oxide nanoparticles (Cu 2 O NPs). In this system, a gaseous discharge plasma is used to replace the usual solid electrode in a conventional electrodeposition, and Cu 2+ ions are released from anodic dissolution and take a form of Cu 2 (OH) 2+ in the solution. The Cu 2 (OH) 2+ moves to the cathode reaction zone and then is reduced to the Cu 2 O monomer by reductants generated from the plasma-liquid interactions. Consequently, Cu 2 O NPs are formed in the solution by the combination of Cu 2 O monomers. The results indicate that the morphology and Cu valence in the nanoparticles are tuned by the added surfactant of glucose or ascorbic acid. Moreover, the Cu 2 O NPs synthesized with a suitable concentration of ascorbic acid demonstrate strong visible light photocatalytic activity on the methyl orange degradation. [ABSTRACT FROM AUTHOR]

With respect to the problems of great impact on the utility grid, the increasing catenary voltage, the limited utilization rate of the regenerative braking energy (RBE) and the irreducible cost of electricity for locomotives caused by the RBE generated by electric locomotives of the whole railway line cannot be fully utilized in traction power supply systems. An energy management system (EMS) integrating electrical energy and information is proposed in this paper. A corresponding optimization algorithm is also proposed to calculate the distribution of the regenerative braking power in the whole railway line. The structure and working principle of the EMS are introduced. The basic principle and detailed steps of the proposed algorithm are given. Finally, the optimization calculation and simulation are carried out, the effectiveness and feasibility of the proposed EMS and the optimization algorithm are verified. [ABSTRACT FROM AUTHOR]

Treatment of methyl orange (MO) synthetic wastewater by air discharge plasma was investigated, and the solution's pH value was found to be a key parameter of influencing the treatment efficiency. The results indicate that lower pH value can induce production of high reactive species, NO+ and peroxynitrous acid, which can contribute to the MO decomposition. When the appropriate amount of Fe2+ ions is present in the MO solution, the MO decomposition can be promoted by Fenton's reaction (Fe2+ reacts with H2O2 produced from the plasma–liquid interaction). Furthermore, the lower pH value is also beneficial for the Fenton's reaction by avoiding an appearance of Fe(OH)3 precipitate that can reduce the treatment efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A plasma-NaCl aqueous solution system has been used to synthesize cuprous oxide (Cu2O) nanoparticles. In this plasma electrochemical system, the argon plasma located above the liquid surface is used as cathode, while a copper plate partially immersed into the aqueous solution as the counter electrode. At the anode zone, the anodic dissolution of Cu plate releases Cu2+ into aqueous solution and then transports and reacts in the plasma-liquid interactions zone. The results show that the morphology of the synthesized Cu2O nanoparticles ranges from irregular shape to spherical structure by altering the concentration of surfactant of cetyltrimethyl ammonium bromide. In addition, the obtained Cu2O nanoparticles with spherical structure have been confirmed to have enhanced visible-light photocatalytic performance of methyl orange degradation. Graphical abstract: [ABSTRACT FROM AUTHOR]

AC heavy-haul trains produce a huge amount of regenerative braking energy when they run on long downhill sections. If this energy can be used by uphill trains in the same power supply section, a reduction in coal transportation cost and an improvement in power quality would result. To accurately predict the energy consumption and regenerative braking energy of heavy-haul trains on large long slopes, a single-particle model of train dynamics was used. According to the theory of railway longitudinal section simplification, the energy consumption and the regenerative braking energy model of a single train based on the train attributes, line conditions, and running speed was established. The model was applied and verified on the Shenshuo Railway. The results indicate that the percentage error of the proposed model is generally less than 10%. The model is a convenient and simple research alternative, with strong engineering feasibility. Based on this foundation, a model of train energy consumption was established under different interval lengths by considering the situation of regenerative braking energy in the multi-train operation mode. The model provides a theoretical foundation for future train diagram layout work with the goal of reducing the total train energy consumption. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is usually considered to be an important reagent in green chemistry since water is the only by-product in H2O2 involved oxidation reactions. Early studies show that direct synthesis of H2O2 by plasma-water interactions is possible, while the factors affecting the H2O2 production in this method remain unclear. Herein, we present a study on the H2O2 synthesis by atmospheric pressure plasma-water interactions. The results indicate that the most important factors for the H2O2 production are the processes taking place at the plasma-water interface, including sputtering, electric field induced hydrated ion emission, and evaporation. The H2O2 production rate reaches ~1200 μmol/h when the liquid cathode is purified water or an aqueous solution of NaCl with an initial conductivity of 10500 μS cm−1. [ABSTRACT FROM AUTHOR]

The stability analysis methods of single-bus dc distribution power systems (DPSs) have been widely studied; however, the multivoltage-level dc DPSs, which have been used in data center, all-electric ship, and so on, its stability analysis methods are rarely reported. The main focus of this article is to study the stability analysis methods, especially the impedance ratio of multivoltage-level dc DPSs. From the point of view of whole system, the two-port small-signal models of multivoltage-level dc DPSs are established and the equivalent loop gains are obtained and used to judge the system stability. On the other hand, the multivoltage-level dc DPSs can be regarded as conventional single-bus dc DPSs at different interfacing locations, and the impedance-ratio type stability criteria are obtained. And it is proved that the two stability analysis methods, namely the system equivalent loop gain and impedance-ratio type stability criterion at different interfacing locations, have the same stability results, which clarifies the stability status by considering different interfacing locations. Finally, the analysis is verified with simulations and hardware-based experiments of a three-converter three-stage dc DPS. [ABSTRACT FROM AUTHOR]

This paper proposes a centralized-decentralized control strategy for regenerative braking energy utilization and power quality improvement in the modified AC-fed railway system with energy-storage-based smart electrical infrastructure. The proposal of a centralized-decentralized control strategy can enhance the ability to withstand and rapidly recover from disruptions, thus providing further guarantees for safe and reliable operation and energy conservation for railway systems. First of all, the description and control strategy of the modified railway system are outlined, and then the control principles and implementation process of the centralized control and decentralized control strategies are given. Moreover, a method of load power detection and regulated power reference calculation is proposed. Finally, the effectiveness of the proposed strategy is verified in a case of a modified railway system consisting of four traction substations and eight power supply sections. The results demonstrate that regenerative braking energy can be efficiently utilized in railways and that power quality can be improved using the proposed centralized-decentralized control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a modified power supply system based on the current alternating current (AC)-fed railways with neutral zones that can further improve the eco-friendliness and smart level of railways. The modified system complements the existing infrastructure with additional energy-storage-based smart electrical infrastructure. This infrastructure comprises power electronic devices with energy storage system connected in parallel to both sides of each neutral zone in the traction substations, power electronic devices connected in parallel to both sides of each neutral zone in section posts, and an energy management system. The description and functions of such a modified system are outlined in this paper. The system allows for the centralized- and distributed-control of different functions via an energy management system. In addition, a control algorithm is proposed, based on the modified system for regenerative braking energy utilization. This would ensure that all the regenerative braking energy in the whole railway electrical system is used more efficiently. Finally, a modified power supply system with eight power supply sections is considered to be a case study; furthermore, the advantages of the proposed system and the effectiveness of the proposed control algorithm are verified. [ABSTRACT FROM AUTHOR]