A robust three phase power flow algorithm for radial distribution systems

An efficient load flow solution technique is required as a part of the distribution automation (DA) system for taking various control and operations decisions. This paper presents an efficient and robust three phase power flow algorithm for application to radial distribution networks. This method exploits the radial nature of the network and uses forward and backward propagation to calculate branch currents and node voltages. The proposed method has been tested to analyse several practical distribution networks of various voltage levels and also having high R/X ratio. The results for a practical distribution feeder are presented for illustration purposes. The application of the proposed method is also extended to find optimum location for reactive power compensation and network reconfiguration for planning and day-to-day operation of distribution networks.     

Sensitization of zinc oxide photoanode with an indoline dye

A dye‐sensitized solar cell (DSC) made of nanoporous ZnO film on aluminum‐doped zinc oxide (ZnO/AZO) transparent substrate has higher solar‐to‐electric energy conversion efficiency than a DSC consisting of nanoporous ZnO film deposited on conventional fluorine‐doped tin oxide (ZnO/FTO) transparent substrate. The ZnO/AZO DSC gave an overall conversion efficiency of 7.2% whereas the ZnO/FTO yielded a conversion efficiency of 4.5%. The film‐substrate orientation and higher light harvesting of the nanoporous ZnO film on the AZO after heating in air are mainly attributed to the higher energy conversion efficiency of the ZnO/AZO DSC. Copyright © 2012 John Wiley & Sons, Ltd.     

Antioxidant activity of cashew-nut-shell liquid in black loaded natural rubber vulcanizates

Cashew-nut-shell liquid (CNSL), which consists mainly of a mixture of two phenols each with a bulky unsaturated alkyl group at the meta position, has been found to protect black loaded natural rubber vulcanizates against autooxidation. Its efficiency as an antioxidant has been found to be comparable with that of the commonly used commercial antioxidants of the amine type. The high antioxidant activity of CNSL is qualitatively explained as being due to a combined effect of the formation of dimeric products and of a network bound antioxidant during vulcanization with sulphur.     

Balance Control of a Biped Robot on a Rotating Platform Based on Efficient Reinforcement Learning

In this work, we combined the model based reinforcement learning (MBRL) and model free reinforcement learning (MFRL) to stabilize a biped robot (NAO robot) on a rotating platform, where the angular velocity of the platform is unknown for the proposed learning algorithm and treated as the external disturbance. Nonparametric Gaussian processes normally require a large number of training data points to deal with the discontinuity of the estimated model. Although some improved method such as probabilistic inference for learning control (PILCO) does not require an explicit global model as the actions are obtained by directly searching the policy space, the overfitting and lack of model complexity may still result in a large deviation between the prediction and the real system. Besides, none of these approaches consider the data error and measurement noise during the training process and test process, respectively. We propose a hierarchical Gaussian processes (GP) models, containing two layers of independent GPs, where the physically continuous probability transition model of the robot is obtained. Due to the physically continuous estimation, the algorithm overcomes the overfitting problem with a guaranteed model complexity, and the number of training data is also reduced. The policy for any given initial state is generated automatically by minimizing the expected cost according to the predefined cost function and the obtained probability distribution of the state. Furthermore, a novel Q(λ) based MFRL method scheme is employed to improve the policy. Simulation results show that the proposed RL algorithm is able to balance NAO robot on a rotating platform, and it is capable of adapting to the platform with varying angular velocity.      

Understanding Automotive Exhaust Catalysts Using a Surface Science Approach: Model NOx Storage Materials

The structure–reactivity relationships of model BaO-based NO_x storage/reduction catalysts were investigated under well controlled experimental conditions using surface science analysis techniques. The reactivity of BaO toward NO₂, CO₂, and H₂O was studied as a function of BaO layer thickness [0 < θ_BaO < 30 monolayer (ML)], sample temperature, reactant partial pressure, and the nature of the substrate the NO_x storage material was deposited onto. Most of the efforts focused on understanding the mechanism of NO₂ storage either on pure BaO, or on BaO exposed to CO₂ or H₂O prior to NO₂ exposure. The interaction of NO₂ with a pure BaO film results in the initial formation of nitrite/nitrate ion pairs by a cooperative adsorption mechanism predicted by prior theoretical calculations. The nitrites are then further oxidized to nitrates to produce a fully nitrated surface. The mechanism of NO₂ uptake on thin BaO films (<4 ML), BaO clusters (<1 ML) and mixed BaO/Al₂O₃ layers are fundamentally different: in these systems initially nitrites are formed only, and then converted to nitrates at longer NO₂ exposure times. These results clarify the contradicting mechanisms presented in prior studies in the literature. After the formation of a nitrate layer the further conversion of the underlying BaO is slow, and strongly depends on both the sample temperature and the NO₂ partial pressure. At 300 K sample temperature amorphous Ba(NO₃)₂ forms that then can be converted to crystalline nitrates at elevated temperatures. The reaction between BaO and H₂O is facile, a series of Ba(OH)₂ phases form under the temperature and H₂O partial pressure regimes studied. Both amorphous and crystalline Ba(OH)₂ phases react with NO₂, and initially form nitrites only that can be converted to nitrates. The NO₂ adsorption capacities of BaO and Ba(OH)₂ are identical, i.e., both of these phases can completely be converted to Ba(NO₃)₂. In contrast, the interaction of CO₂ with pure BaO results in the formation of a BaCO₃ layer that prevents to complete carbonation of the entire BaO film under the experimental conditions applied in these studies. However, these “carbonated” BaO layers readily react with NO₂, and at elevated sample temperature even the carbonate layer is converted to nitrates. The importance of the metal oxide/metal interface in the chemistry on NO_x storage-reduction catalysts was studied on BaO(<1 ML)/Pt(111) reverse model catalysts. In comparison to the clean Pt(111), new oxygen adsorption phases were identified on the BaO/Pt(111) surface that can be associated with oxygen atoms strongly adsorbed on Pt atoms at the peripheries of BaO particles. A simple kinetic model developed helped explain the observed thermal desorption results. The role of the oxide/metal interface in the reduction of Ba(NO₃)₂ was also substantiated in experiments where Ba(NO₃)₂/O/Pt(111) samples were exposed to CO at elevated sample temperature. The catalytic decomposition of the nitrate phase occurred as soon as metal sites opened up by the removal of interfacial oxygen via CO oxidation from the O/Pt(111) surface. The temperature for catalytic nitrate reduction was found to be significantly lower than the onset temperature of thermal nitrate decomposition.     

A Novel Technique to Compensate Voltage Sags in Multiline Distribution System&#8212;The Interline Dynamic Voltage Restorer

The dynamic voltage restorer (DVR) provides a technically advanced and economical solution to voltage-sag problem. As the voltage-restoration process involves real-power injection into the distribution system, the capability of a particular DVR topology, especially for compensating long-duration voltage sags, depends on the energy storage capacity of the DVR. The interline DVR (IDVR) proposed in this paper provides a way to replenish dc-link energy storage dynamically. The IDVR consists of several DVRs connected to different distribution feeders in the power system. The DVRs in the IDVR system share a common energy storage. When one of the DVR compensates for voltage sag appearing in that feeder, the other DVRs replenish the energy in the common dc-link dynamically. Thus, one DVR in the IDVR system works in voltage-sag compensation mode while the other DVRs in the IDVR system operate in power-flow control mode. In principle, IDVR can operate effectively when constituent DVRs are electrically (not necessarily physically) far apart. Closed-loop load voltage and current-mode-control techniques are used as the control strategy in the two modes of operation. Experimental results obtained for a laboratory prototype of the IDVR are presented to show the effectiveness and the efficacy of the proposed IDVR system to improve power quality     

A novel dynamic series compensator with closed-loop voltage and current mode control for voltage sag mitigation

The increased use of voltage-sensitive equipment in the industrial sector has made industrial processes more susceptible to supply voltage quality problems in the form of voltage sags. Series-connected voltage source converter (VSC)-based devices have been gaining popularity in protecting sensitive loads against voltage sags. This paper presents a novel transformerless dynamic series compensator (DSC) to mitigate long-duration voltage sags effectively. A line-side controllable rectifier connected to the proposed DSC maintains the dc-link voltage at a specific value while the DSC compensates voltage sags. The DSC is controlled by a closed-loop voltage and current mode controller which provides better damping and dynamic performance than that of in open-loop controller. The closed-loop controller consists of an outer voltage loop and an inner current loop derived from filter capacitor current. Performance of the proposed DSC is tested under varied voltage sag conditions, and simulated and experimental results are presented to show the effectiveness of the proposed DSC in mitigating long-duration voltage sags.     

Electrolytic concentration effect on the abrasive assisted-electrochemical machining of an aluminum–boron carbide composite

All engineering materials can be machined by one or combination of processes in such a way that the material’s potential is fully exploited. Electrochemical machining is found to be a most promising process that produces various components from the hard-to-machine materials for the various applications. Electrolyte concentration is playing a positive role by improving the electrolyte conductivity, but negatively forming the passivation layer on the cut surfaces. In order to improve the surface finish and removal of generated residual materials from the cut surfaces, abrasive particles were fed along with electrolyte into the machining zone. This present paper investigates the sodium chloride (NaCl) electrolyte with varied concentration (10–30%) in association with SiC abrasive particles on the material removal rate, surface roughness, and radial overcut while machining of aluminum 6061–boron carbide (5–15?wt%) composites. This study conclusively derived that electrolyte concentration up to 20% exhibited a positive role in the material removal rate for the machining of composites because the rate of dissolution was of higher magnitude. Externally supplied abrasive particles along with electrolyte reduced the surface roughness and radial over cut to an extent. Conversely, at higher electrolyte concentration, the externally supplied abrasive particles have a little effect on the removal of the formed passivation layer as confirmed by SEM analysis.