Open-circuit Operation Research Articles

Open-Circuit Fault-Tolerant Control for Dual Three-Phase PMSM With Minimum Torque Ripple Considering Phase Back EMF Harmonics

This paper proposed an open-circuit fault-tolerant control method for dual three-phase permanent magnet synchronous motor (DTPPMSM), which takes the back electromotive force (back EMF) harmonics into consideration and can achieve the minimum torque ripple. From the perspective of machine ontology and electromagnetic power, this paper analyzed the influence of back EMF harmonics on torque ripple. On this basis, by adjusting the phase of currents, specific order torque ripple components which can offset each other can be generated by the back EMF fundamental wave and harmonics, thus suppressing the specific order torque ripple of the whole motor. Furthermore, not limited to specific order torque ripple, the method can also be used to obtain the minimum overall torque ripple under open-circuit operation. Finite element analysis (FEA) and prototype experiment are employed to verify the proposed method.

Design optimization of Solar Power Inverter using the GRA Method

Among the most crucial components of a solar-powered system is an inverter. It is an apparatus that transforms the direct current (DC) produced by solar panels into the alternating current (AC) required by the electric system. Flashing hybrid solar inverter is the best solar inverter for home which offers the following features: - Its operating voltage is between 100-290V. - It has 700 VA of power. 5kW solar inverter price budget starts at $2,000 for excellent single-phase devices and $1,000 for existing datasets (like Sungrow) (eg Fronius or SMA). The most popular size, 5kW, can accommodate arrays up to 6.6kW in power. A solar charge controller can only function effectively during the day, because when the ultraviolet irradiance is strong and, the system's Voltage rating must reach the inverter at a moderate DC voltage level in order for it to function. Your photovoltaic systems and inverter operate at night power will be off. The inverter doesn't run overnight because it doesn't want to draw electricity. Instead, it rises again in the morning when the sun shines. Your home and solar system are connected to the utility grid. By switching to solar PV-based power generation from the airport's current conventional energy source, the carbon footprint of the facility can be decreased. Power distribution solar PV power facilities may be built in regions that are required to be broad and free of obstructions around runways. Based on first year operating data, the current study seeks to evaluate the operational efficiency of a 12 MWp solar-powered airport at Cochin Airport Limited (CIAL), India. With the aid of the most well-liked PV simulation programmes, such as Deterioration in quality and Solar Gis, the plant effectiveness is precisely rendered. The software's performance metrics were discovered to perfectly resemble the observed values. Economic and ecological studies of Kochi airports powered by solar energy attest to its efficiency in lowering carbon footprint, resulting in an airport with almost no emissions that is clean, green, and sustainable.Gray correlation analysis is widely used to measure the degree of relationship between sequences through the gray correlation coefficient. Gray relational analysis has been used by many researchers to optimize control parameters with multiple responses through gray relational grading. The fundamental tenet of the GRA approach is that the chosen option must have the "greatest degree of Green relation" to the positive-ideal solution and the "minimum of grey relation" to the negative-best answer. A technique for determining whether or not variables are connected and how much they are correlated is called grey correlation coefficient analysis. The primary method of determining these curves' geometric similarity is by the construction of characteristic series curves. Type of Solar Module, No of modules per string, No of string, No of inverters and No of transformers Short circuit current (ISC), Open circuit voltage (VOC), Operating Temperature and Dimension. Stress Management in Healthcare Institutions in Work overload is got the first rank whereas is the Overtime is having the lowest rank.

Defect chemistry and transportation within La1.7Ba1.3In2O6.85 mixed ionic-electronic conducting membrane: Towards the application of solid oxide fuel cells

La1.7Ba1.3In2O6.85, as a representative material belonging to La2BaIn2O7-based family, is a novel and promising electrolyte material for solid oxide fuel cells (SOFCs). However, due to the co-existence of various mobile charged defects including oxygen vacancy, proton, and electron-hole, the conduction properties and behaviors of La1.7Ba1.3In2O6.85 are complex and not fully understood. In this work, we systematically explore La1.7Ba1.3In2O6.85 with a focus on defect chemistry and transportation. A theoretical model is built to analyze the experimentally measured conductivities of La1.7Ba1.3In2O6.85 at varying temperatures and oxygen partial pressures. Subsequently, the conduction properties and behaviors of La1.7Ba1.3In2O6.85 membrane at open circuit conditions and operation conditions are investigated thoroughly for the first time. Our findings reveal that in reducing and humidified atmospheres, La1.7Ba1.3In2O6.85 behaves as a dual-ion conducting oxide, with oxygen-ionic transport numbers exceeding 0.7. Our work can provide a new and overall understanding of the La2BaIn2O7-based material for SOFCs’ application.

Application of TUSSIM with a variable Tromp curve for predicting optimal operation of multi-compartment mills with various ball size distributions

A true unsteady-state simulator (TUSSIM) for ball milling was integrated with a variable Tromp curve for classification to simulate and optimize closed-circuit, multi-compartment cement ball milling. Using representative model–operational parameters from available literature, we first investigated the system dynamics for a two-compartment mill. Then, various simulations examined the impacts of closed-circuit vs. open-circuit operation, number of compartments, and various ball size distributions. Our results suggest that integrating an air classifier into an open-circuit ball mill can increase the production rate by 15% or increase the cement-specific surface area by 13%. A single-compartment mill entails a pre-milled feed for proper operation, whereas a two-compartment mill yields a finer cement product than a three-compartment mill. Uniform mass distribution of balls led to slightly finer product than uniform surface area or number distributions, while the impact of a classifying liner was negligibly small. Finally, we identified optimal ball mixtures in a two-compartment mill using a combined global optimizer–DAE solver, which suggests 14% capacity increase with desirable cement quality. Overall, TUSSIM’s results are not only in line with limited, full-scale experimental studies and industry best practices, but also provide fundamental process insights, while enabling process optimization with tailored ball mixtures in different compartments.

Experimental Investigation of CECE Process to Recover Tritium and Deuterium from Low Tritiated/Deuterated Liquid Waste

A current concern of researchers from the Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) within the National R&D Institute for Cryogenics and Isotopic Technologies in Rm. Valcea is the solution of a combined electrolysis catalytic exchange (CECE) isotopic separation process that aims to be part of a new liquid waste decontamination technology. The experimental installation, defined as module M1100, has interfaces with the PESTD process and auxiliary systems and is placed within the PESTD area. The installation has its own automation and control system that allows for safe operation. Two operating modes are presented. The first mode is in “open-circuit” mode to evaluate the individual separation performances of the two technological processes, water electrolysis and water-hydrogen catalytic isotopic exchange, respectively. The second mode is in “closed loop,” which corresponds to the CECE isotopic separation process where the tritium/deuterium are concentrated in the water within the electrolyzer. The preliminary experimental investigations were performed with low-concentrated tritiated water (HTO; ~100 Bq/l] in order to have a reduced degree of contamination as the concentration of the processed water was increased (~1000 Bq/l). The evaluation of the separation performances was made by comparing correlations from direct measurements with the calculated ones provided by the software developed for the CECE isotopic separation process in the open-circuit operating mode. For the closed-loop operation mode, the data provided by the calculation program for the representation of the nonstationary CECE isotopic separation regime were compared with the measured data. The preliminary results show a good correlation between the measured and the calculated data considering these experiments were carried out mainly in order to improve the operating performance.

Multiterminal open quantum dot circuit operating in the fractional quantum Hall regime

We study theoretically a large quantum dot in the fractional quantum Hall regime that is strongly coupled to $\mathcal{M}$ leads via single-mode quantum point contacts. In the case $\mathcal{M}=2$, when the system is mapped onto the two-channel charge Kondo problem, we predict a universal expression for the conductance in the vicinity of a strong-coupling fixed point. The power of the leading temperature correction to the maximal conductance is determined by the fractional filling factor $\ensuremath{\nu}=1/m$. For $\mathcal{M}>2$, we examine the case in which $\mathcal{M}\ensuremath{-}1$ quantum point contacts are fully open, reproducing a single-channel circuit coupled to a dissipative Ohmic environment. The system is treated as a Luttinger liquid with an impurity, whose effective interaction parameter is defined as $K=\ensuremath{\nu}(\mathcal{M}\ensuremath{-}1)/\mathcal{M}$. Conductance scaling in the weak and strong tunnel regimes is used to discuss the low-temperature transport behavior of multichannel single- and double-charge Kondo devices.

(Invited, Digital Presentation) Accelerated Stress Test Development for PEM Water Electrolyzers

The use of clean hydrogen around the world is expected to significantly increase in the coming decades as various countries move towards their carbon neutral goals. The United States has committed significant funds ($9.5 Billion over the next 5 years) to the demonstration of a clean hydrogen infrastructure with electrolysis ($1 Billion in research over the next 5 years) being one of the key enabling technologies. Polymer electrolyte membrane water electrolyzers (PEMWE) for hydrogen production are expected to play a critical role in this transition to a hydrogen economy. The DOE has formed a consortium (H2NEW : Hydrogen from the next generation of electrolyzers of Water) to overcome technical barriers to affordable, reliable and efficient electrolyzer development. The consortium is working on various aspects of PEMWEs to improve their durability, decrease their cost, improve manufacturability and demonstrate economic feasibility. As part of this effort, the consortium is developing accelerated stress tests (ASTs) for PEMWEs. The DOE in collaboration with National Laboratories and the U.S. Drive Fuel Cell Technical team has developed a set of validated and widely accepted ASTs for fuel cells. While these fuel cell ASTs have spurred significant materials development over the past decade, there is no accepted set of ASTs for PEMWEs.This talk will summarize our recent learnings from the development of PEMFC ASTs and how these apply to PEMWEs. While several materials including the cathode catalyst, membrane, and cathode gas diffusion layer are similar between these two systems, there are significant differences in the operating conditions and materials used at the anode of the electrolyzer. The key to successful AST development is to ensure that the stressors accelerating the degradation mechanisms are relevant to the operating conditions encountered in the intended application. An AST working group (ASTWG) that includes various U.S. electrolyzer manufacturers has been established within the consortium to incorporate feedback from commercial electrolyzer systems. Literature reports have demonstrated that both potential cycling1 and transition through Ir/IrOx redox potential2 (during open circuit operation or shutdown of electrolyzer) can be detrimental to the anode catalyst. Membrane degradation occurs under electrolyzer conditions and is accelerated with increasing temperature and low current density operation.3 The effect of electrolyzer operating conditions on both membrane and anode catalyst durability will be discussed in this talk. The various stressors leading to increased degradation of both anode catalysts and membranes will be discussed and potential PEMWE ASTs will be proposed. Acknowledgement This research is supported by the U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office, through the H2NEW consortium.References M. Alia, S. Stariha, and R. L. Borup, J. Electrochem. Soc., 166, F1164–F1172 (2019). Weiß, A. Siebel, M. Bernt, T. H. Shen, V. Tileli and H. A. Gasteiger, Journal of The Electrochemical Society, 2019, 166, F487-F497 Marocco, K. Sundseth, T. Aarhaug, A. Lanzini, M. Santarelli, A. O. Barnett and M. Thomassen, Journal of Power Sources, 2021, 483, 229179.

Adaline-Based Control Schemes for Non-Sinusoidal Multiphase Drives—Part II: Torque Optimization for Faulty Mode

Fault tolerance has been known as one of the main advantages of multiphase drives. When an open-circuit fault happens, smooth torque can be obtained without any additional hardware. However, a reconfiguration strategy is required to determine new reference currents. Despite advantages of non-sinusoidal electromotive forces (NS-EMFs) such as high torque density, multi-harmonics existing in NS-EMFs cause more challenges for control, especially under faulty conditions. Therefore, to guarantee high-quality vector control of multiphase drives with multi-harmonic NS-EMFs, this two-part study proposes control schemes using adaptive linear neurons (Adalines) to adaptively eliminate torque ripples. The proposed simple Adalines are efficient because of taking advantage of the knowledge of rotor position and of torque harmonic rank induced by the NS-EMFs. The control scheme using an Adaline for healthy mode was described in part I of this study. In this second part, the control scheme using another Adaline for an open-circuit operation, under the impacts of multi-harmonics in NS-EMFs, is proposed. Notably, smooth torque and similar copper losses in the remaining healthy phases can be obtained. Experimental tests are carried out on a seven-phase permanent magnet synchronous machine (PMSM) with a high total harmonic distortion (THD = 38%) of NS-EMFs. A demonstration video is provided with this paper.

A Fast Calculation Approach for Pressure Finger Losses in Large Salient-Pole Synchronous Machines

This article proposes a new, computationally inexpensive calculation approach for eddy current losses in nonmagnetic pressure fingers for open-circuit operation. The field calculation was presented in a previous article (Fricke et al., 2019) and is based on a Schwarz-Christoffel mapping. An alternative 2-D FEA field calculation is presented. The loss model discretizes the pressure fingers similar to 2-D FEA and solves an electric network, while allowing for geometric different alterations, such as slits, to be considered. The proposed approach takes only around one second to compute, with the loss model itself taking only around 60 ms. Comparisons to a time-step 3-D FEA model are used to validate the new method.

Electrically and Frequency-Tunable Printed Inverted-F Antenna with a Perturbed Parasitic Element

This study designed an electrically and frequency-tunable printed inverted-F antenna (PIFA) with a perturbed parasitic element between the antenna and the ground plane. The resonant frequency of the proposed antenna can be changed via the short- and open-circuit operation of the parasitic element. This operation is activated using an electrical switch, which in this case is a PIN diode with an inductor and a resistor. The antenna was designed on the basis of the principles of the perturbation method, which enables control over resonant frequencies through modifications to the volume of a metal cavity. Meandered gaps were incorporated into the parasitic element for the independent operation of each PIN diode switch. The size of the PIFA’s radiator is 4.8 × 10 mm<sup>2</sup>, and the tunable resonant frequency at the –10 dB bandwidth is 340 MHz (17.3%).

How Operational Parameters Affect Electromethanogenesis in a Bioelectrochemical Power-to-Gas Prototype

Bioelectrochemical power-to-gas represents a novel solution for electrical energy storage, currently under development. It allows storing renewable energy surplus in the form of methane (CH4), while treating wastewater, therefore bridging the electricity and natural gas (and wastewater) grids. The technology can be coupled with membrane contactors for carbon dioxide (CO2) capture, dissolving the CO2 in wastewater before feeding it to the bioelectrochemical system. This way, the integrated system can achieve simultaneous carbon capture and energy storage objectives, in the scenario of a wastewater treatment plant application. In this study, such technology was developed in a medium-scale prototype (32 L volume), which was operated for 400 days in different conditions of temperature, voltage and CO2 capture rate. The prototype achieved the highest CH4 production rate (147 ± 33 L m-3 d-1) at the lowest specific energy consumption (1,0 ± 0,3 kWh m-3 CH4) when operated at 25 oC and applying a voltage of 0,7 V, while capturing and converting 22 L m-3 d-1 of CO2. The produced biogas was nearer to biomethane quality (CH4 > 90% v/v) when CO2 was not injected in the wastewater. Traces of hydrogen (H2) in the biogas, detectable during the periods of closed electrical circuit operation, indicated that hydrogenotrophic methanogenesis was taking place at the cathode. On the other hand, a relevant CH4 production during the periods of open electrical circuit operation confirmed the presence of acetoclastic methanogenic microorganisms in the microbial community, which was dominated by the archaeal genus Methanothrix (Euryarcheota). Different operational taxonomic units belonging to the bacterial Synergistes phylum were found at the anode and the cathode, having a potential role in organic matter degradation and H2 production, respectively. In the panorama of methanation technologies currently available for power-to-gas, the performances of this bioelectrochemical prototype are not yet competitive, especially in terms of volumetric CH4 production rate and power density demand. However, the possibility to obtain a high-quality biogas (almost reaching biomethane quality standards) at a minimal energy consumption represents a potentially favourable business scenario for this technology.

Comparison of the performance of different comminution technologies in terms of energy efficiency and mineral liberation

In this study, a magnetite-rich ore was comminuted using laboratory-scale SFC and HPGR in open-circuit operations. Both comminution devices were operated at an identical net specific energy input, and their respective particle reduction ratios, size-specific energies (SSEs), and Bond operating work indices were used to evaluate and compare their grinding efficiencies. Also, the liberation characteristics of selected size fractions (−106+75 µm, −75+45 µm, and <45 µm) of the products obtained from both the SFC and the HPGR were investigated and compared using QEMSCAN™ and magnetic separation (on the <106 µm size fractions). The results showed that the SFC generated finer product particles and subsequently achieved a higher particle reduction ratio compared with the HPGR. Additionally, the SFC operated at a lower Bond operating work index and SSE (for <75 µm) than HPGR, which was interpreted as partially due to the edge effect of the open-circuit HPGR operation. The size-by-size liberation studies showed that the magnetite in both the HPGR and the SFC products were sparsely liberated with <2% being liberated in the <45 µm size fractions. The results from the magnetic separation studies showed that both the HPGR and the SFC products yielded statistically identical separation efficiency, although the HPGR’s product generated slightly higher mass and iron recoveries. Finally, whilst the HPGR’s product yielded higher gangue rejection compared with that of the SFC, the SFC’s product showed a slightly higher Fe upgrade compared with that of the HPGR.

A Rechargeable Zinc-Copper Battery Based on the Combination of a Monovalent Cationic Exchange Membrane and an Inert Charge Shuttle

To reach their full potential, renewable and intermittent energy sources such as wind and sun need to be coupled with a cost effective energy management system that is able to convert, store, and delivery energy as required. The Daniell element is one of the earliest non-rechargeable batteries. It is based on abundant, cost-effective and environmentally-benign materials and the chemistry relies on reduction of copper at the positive electrode and oxidation of zinc at the negative electrode. Since both electrodes are immersed in different electrolytes, they have to be separated by a porous barrier or a salt-bridge in order to prevent the self-discharge of the battery. However, these separators are not selective and copper ions migrate over time to the negative electrode and deposit on the surface of the zinc electrode which reduces shelf time and makes recharging of the element impossible.In this work, we report on a novel Zinc-Copper battery design which is based on the application of a selective cation exchange membrane in conjunction with an unreactive sodium background electrolyte which acts as a charge shuttle. The membrane is impermeable for the copper (and zinc) ions but allows the sodium ions to migrate between the two half-cells to maintain the electro-neutrality.We first tested the suitability of different zinc-based electrolytes, including zinc sulfate, zinc chloride, and zinc nitrate. At equal electrolyte conductivities, we found a higher potential for the zinc deposition in sulfate electrolytes compared to that in chloride electrolytes. It was also observed that the zinc electrode passivated due to the formation of zinc oxide (ZnO) when operated in a zinc nitrate solution. In terms of the electrodeposition of copper, sulfate and nitrate-based electrolytes showed a nearly equal potential. However, chloride-based copper electrolytes shifted the potential to more negative values due to the stabilization of the monovalent copper ion intermediate.The membrane selectivity was evaluated by monitoring the crossover of copper ions into the zinc half-cell for various concentrations of copper in the copper half-cell. After seven days of open circuit operation, we measured copper concentrations below 10 ppm in the zinc half-cell when there was 0.1 M of copper sulfate in the copper half-cell. When the copper half-cell was filled with 0.5 M copper sulfate, the effect of crossover was evident by a blue tint of the electrolyte and the Zn electrode was covered with a layer of black/red deposit.Hence, we chose a conservative catholyte composition of 0.1 M copper sulfate and 1M sodium sulfate in the battery. We performed discharge measurements where we varied the discharge current density and measured the voltage over time. Discharge continued until a cell voltage of 0 V was reached, which corresponds to a complete consumption of the copper ions in the catholyte. Indeed, it turned out that we utilized only around 3 to 6 % of the zinc electrode and less than 1 % of the copper electrode during discharge. These very low values indicate that the present system could also be favorably-designed as a hybrid redox (flow) battery. Hence, for the current preliminary cell design it is seems reasonable to normalize the current with the mass of the initial copper ion content since it is the limiting electro-active species. At 0.5 mA/cm2 (421 mA/g), the battery was discharged for around 17 hours before all of the copper ions were consumed resulting in a specific capacity of 763 mAh/g. The theoretical charge content based on the initial copper concentration was 843 mAh/g giving a faradaic yield of 90.5 %. The capacity and faradaic yield of the discharge at 1 mA/cm−2 (842 mA/g) were 583 mAh/g and 69.2 %, respectively.The recharge-ability of the battery was investigated over 100 charge-discharge cycles at a current density of ±0.5 mA/cm2. The average capacity was 530 mAh/g while the average exergy efficiency was 74 %. The deviations over the cycle numbers are less than 5 % of the average values. In other words, there was no clear increase or decrease during operation, indicating a steady performance. Afterwards, the zinc electrode was characterized using Energy-dispersive X-ray spectroscopy. Only a very small amount of deposited copper was found, indicating a negligible copper ion cross over. This verifies that the combination of a cost-effective monovalent cation exchange membrane along with an unreactive background electrolyte imparts recharge-ability to the Daniell cell. Figure 1

Electrical Modeling of Dye-Sensitized Solar Cells for Improving the Overall Photoelectric Conversion Efficiency

An electrical model of dye-sensitized solar cell (DSSC) is derived on continuity and transport equations for all the four charged species i.e. electrons, iodide ions (I-), triiodide ions (I3-) and cations. The device model comprises of a pseudo-homogeneous active layer, where solar photovoltaic effect including both diffusion of electrons in nanoporous TiO2 layer as well as ions in electrolyte occur, and a bulk electrolyte layer, where only ions diffuse take place. The distribution of the electrons, iodide and tri-iodide ions as function of the pseudo-homogeneous active layer thickness of the DSSC under both the open-circuit and short-circuit operation conditions were performed. Parametric studies were conducted to analyze (J–V) characteristic of the DSSC with three different sets of porosity and also for different sets of TiO2 layer thicknesses.

Control Strategy for Single-Phase Open-Circuit Operation of a Modular Solid-State Transformer

The solid-state transformer (SST) has the ability to operate with only two input phases, which can be called single-phase open-circuit (SPO) operation. With this ability, the SST can maintain operation under permanent single-phase-to-ground faults, where the fault phase must be isolated, providing a better power supply sustainability than that of the conventional low-frequency transformer. In the absence of research on the SPO operation of an SST, this paper presents a study of it. The influence of SPO operation on the grid and the SST itself is analyzed. Under the SPO state, the SST will inject the negative-sequence current to the grid; meanwhile, the maximum load power will decline; thus, the optimized power factor under the SPO state is unity. The maximum power of △-SST is higher than that of the Y-SST under the SPO state owing to the △ connection. A control strategy for the SST medium-voltage cascaded H-bridge stage is proposed. SPO current control can be achieved by controlling the positive-sequence current. A proper negative-sequence voltage can be injected to synchronize the cluster voltages to obtain a lower current total harmonic distortion and smaller dc voltage ripple. In the △-SST, a proper zero-sequence current can be injected to fully use the power rating of the double-cluster branch.

Suppression of Current Fluctuations and the Brake Torque for PMSM Shutoff in Electric Vehicles

When a safety‐related fault in the motor controller is detected, the torque output of the motor cannot be effectively shut off in time and an overcurrent occurs at the moment of switching. The advantages and disadvantages of the open circuit and active short‐circuit methods are analyzed. Combining the advantages of these two operations, this paper proposes a new mixed voltage modulation method. It introduces a voltage modulation ratio that represents the duty cycle of the open circuit operation during a PWM period. This ratio is first set to a fixed value and gradually reduced to zero. The inverter is switched at a mixed operation and finally remains in the active short‐circuit mode. The current can be quickly converged by a freewheeling diode of open circuit. After switching to active circuit, the brake torque is safety. The effectiveness of this shutoff method was verified by simulations and experiments. It shows that current fluctuations are suppressed and the torque output is also within a safety range. In addition, this shutoff method does not require any additional sensor information and is simple to implement.

Fault-Tolerant Control of Hybrid Excitation Axial Field Flux-Switching Permanent Magnet Machines

With the development of electric vehicles (EVs), the reliability and security of the motor drive system have been in high demand in recent years. EVs can still work reliably even when the motor drive system encounters some failures. Therefore, fault-tolerant motors have become the focus of research all over the world. The hybrid excitation axial field flux-switching permanent magnet machine (HEAFFSPMM) is a novel stator excitation brushless PM machine. It combines the advantages of AFFSPMM and hybrid excitation PM machine. Based on a 600 W prototype of three-phase 12/10 stator/rotor pole AFFSPMM, these parameters of HEAFFSPMM are optimized by 3-D finite element method in order to obtain the high self-inductance and low ratio of mutual and self-inductances, including the number of rotor poles, the split ratio, the width of permanent magnet, and the width of stator middle teeth. Then, the fault-tolerant control method of the space vector pulse width modulation based on minimum copper loss is proposed in this paper with the combination of adjusting the field current. The control methods of the HEAFFSPMM are simulated and investigated at healthy and one-phase open-circuit operation. Finally, the experiments are done to validate the proposed fault-tolerant control method. The results indicate that the HEAFFSPMM has good fault tolerance under the proposed control method.

Concentrating System’s Design and Performance Analysis for Spacial Solar Array

A large area of sunlight onto solar cells is gathered by concentrating system for spacial concentrating solar array, which reduces the amount of solar cells by increasing light intensity onto the solar cells of the unit area. Under concentrating conditions, the short-circuit current, open-circuit voltage, fill factor, efficiency, operating temperature and strong thermal-electrical coupling characteristics of concentrating solar cells are different from the conventional solar cells because of the high intensity and high operating temperature. The concentrating module design, solar cell selection, and design of solar cell heat-dissipation have been carried out. The thermal-electric coupling model of special concentrating photovoltaic system has been established. The relationships among concentrated ratio, substrate-thickness, thermal conductivity of substrate-material and solar cell’s temperature, density of short-circuit current, open-circuit voltage, maximum output power have been analyzed, which provide a view to a reasonabl0e match and selection of multi-parameters in engineering design. Results show that the concentrated ratio has an overall effect on the open-circuit voltage, short-circuit current, efficiency and operating temperature of the solar cell. There is a strong coupling relationship among the parameters, and the positive and negative impacts caused by the concentrating characteristics should be weighed in the engineering design. The short-circuit current density of concentrating solar cells is proportional to the concentrated ratio. Under the lower concentrated ratio circumstance, fill factor and efficiency is not substantially affected by the concentrated ratio. The maximum output power and open-circuit voltage increase with the increase of concentrated ratio. Temperature of concentrating solar cells has an adverse effect on the open-circuit voltage, efficiency and output power, which needs high efficient radiator measures to be taken. The operating temperature of solar cells could be decreased significantly by the high thermal conductivity of the substrate-material. The concentrated ratio between 9~15 is recommended for spacial solar array, which not only embodies the advantage of concentrator like improving the cell-efficiency and decreasing the cost, but also doesn’t exact the deploying precision of concentrating system.

In Situ Development of Efficient Electrogenic Bacterial Community in Urine Fed Microbial Fuel Cell Cascades

Microbial fuel cell technology harnesses the potential of some naturally occurring bacteria for electricity generation. To initiate the operation of microbial fuel cells, inoculation with different types of bacterial community, including those found in activated sludge, are employed. There are however, health hazards associated with the use of digested activated sludge and this of course depends on where the sample has been sourced from. Organisms such as Mycobacterium tuberculosis, Pseudomonas aeruginosa and enteric viruses have been reported in activated sludge, which can have practical difficulties when working with such samples. Therefore, the development of an efficient electroactive bacterial community, capable of producing optimum power output without the need for sludge inoculation, would eliminate any potential risks. In the current study, we developed an efficient electroactive bacterial community within a ceramic based MFC system, using only fresh urine as the inoculum. Efficient biofilm development was achieved by stepwise adjustment of the external resistance, following 48 hours of open circuit operation. This resulted in a uniform bacterial community with power output levels >50% higher than those inoculated (as per standard practice) with activated sludge. The results showed that power generation begins within 2 days of experimental set-up, compared to at least 5 days in sludge inoculated systems, thus significantly reducing start up time. Incidentally, the development of the bacterial community occurs irrespective of the freshness or age of the urine feed. Given the difficulty in moving suitable activated sludge across countries/borders and that practical application of MFCs technology is more likely to occur in remote rural locations, it is possible that suitable activated sludge might not be available for inoculation locally. Therefore, deployment of MFC systems capable of producing optimum power without the need for sludge-inoculation would be beneficial to their widespread global application. This is the first report of an in situ development of an electroactive bacterial community in urine-fed MFC systems that outperform those initially inoculated with activated sludge. Keywords: In situ bacterial community development, Microbial fuel cell, Fresh urine, Electrogenic bacterial community.

Сравнительный анализ результатов экспериментального исследования несимметричных режимов работы трехфазного трансформатора и данных полнофазного моделирования

Achieving better energy efficiency and quality of electrical power supply in distribution networks is a multipronged problem, which should be solved with reference to unbiased criteria. Data obtained from load flow analysis of the network under study serve as the main criterion in estimating the efficiency of technical solutions and administrative measures aimed at decreasing technical and commercial losses and improving the key electric energy quality indicators. At the same time, achieving better accuracy of a numerical analysis of electrical networks with loads unevenly distributed among the phases, including, in particular, distribution networks, still remains a significant problem in the electric power industry. The single-line equivalent circuits, which are conventionally used in engineering applications, do not allow the steady-state operating conditions of a three-phase electric network containing multiple sources of imbalance to be analyzed with sufficient accuracy. Under such conditions, it is reasonable to make a shift for using a three-phase representation of the network under study. This approach involves the need to construct three-phase equivalent circuits of electrical equipment, determine their parameters and use them for analysis. The article describes a conceptual approach for constructing the three-phase model of a three-phase two-winding transformer with a wye - grounded wye winding connection circuit, which is widely used in distribution networks. The following experiments were carried out on the test bench: open-circuit test, short-circuit test, load operation tests, open-circuit test under zero sequence supply voltage, and open-circuit test and load operation tests with one phase disconnected. Part of the experimental data was used to calculate the parameters of the three-phase equivalent circuit and to model a three-phase transformer in the MATLAB environment based on the described method.A comparison between the simulated and the experimental data testifies that the performed simulation of various transformer operating conditions yields highly reliable and accurate results. In the balanced mode, the maximum and minimum errors of simulating the main parameters were found to be 4.78 and 2.13%, respectively. In the unbalanced mode, the maximum and minimum errors of simulating the main parameters were found to be 6.6 and 0.78%, respectively. The obtained results allow a conclusion to be drawn that the proposed model of a three-phase two-winding transformer with the wye - grounded wye winding connection circuit adequately reflects the properties of a real transformer. The proposed technique allows the key properties of a three-phase transformer to be revealed, namely, the redistribution of magnetic fluxes among the magnetic core legs and the presence of voltage across the secondary winding when one of the primary winding phases is open. It can also be inferred that a three-phase transformer has a balancing effect.