Basic Power Research Articles

Comparison of Basic Inductive Power Transfer Systems With Linear Control Achieving Optimized Efficiency

Inductive power transfer (IPT) systems with front-side and load-side converters are generally developed for better overall system efficiency than a single IPT converter by providing maximum efficiency tracking and output regulation against variations of coupling coefficient ( $k$ ) and load. The optimum efficiency point of an IPT converter is at a particular loading resistance, which varies with $k$ and is hard to measure directly for the purpose of control. Perturb and observe control is normally implemented to iteratively track the optimum efficiency point. However, this heuristic algorithm results in slow response to the variations of $k$ and load. Recently, a much faster linear control for optimum efficiency tracking has been developed for the series-series (SS) IPT system only. This paper proposes a general linear control scheme for all four basic IPT systems to track the optimum efficiency point. Unlike the SS IPT converter, it is found that additional control of either frequency or adaptive compensation is needed for the other three basic IPT converters to operate against the variation of $k$ . Different input to output transfer functions and their $k$ - and load-independent properties at optimum efficiency are identified for all four basic IPT systems. Thus, a general fast linear control can be applied in the front-side converter to achieve optimum efficiency, while the load-side converter regulates the output power independently. Furthermore, the maximum efficiencies of the IPT converters with these four basic compensations for an identical loosely-coupled transformer are compared theoretically and verified experimentally. The parallel–parallel IPT converter gives the best efficiency. Its additional frequency control in conjunction with the optimum efficiency tracking and the output power regulation is also experimentally validated.

Analysis of power system parameters for islanding detection using wavelet transform

<p><span>This paper classifies the basic power system parameters based on sensitivity and performance capability. This is the basic step in selecting the suitable parameter for intelligent islanding detection technique. The behaviour of basic power system parameters is analyzed using wavelet transform under all possible islanding and non-islanding conditions. In wavelet transform, the mother wavelet plays a significant role in the extraction of parameter features. The db4 mother wavelet is selected after an extensive analysis on different mother wavelets. As a result, it has been found that the extracted feature of reactive power shows the highest capability to distinguish islanding from non-islanding events.</span></p>

Effect of gripping conditions and strip oscillations on vibrations originating at cold rolling

The process of continuous rolling is subjected to non-stationarity, accompanied by oscillations of not only basic technological and power parameters, but also parameters in the hearth of deformation. Non-stationarity at the rolling accounting high dynamic of the process results in origination of negative vibration effects. To prevent the vibrations originations the rolling speed is decreased, which prevents the reaching of the designing parameters of rolling mills operation. The study of influence of non-stationarity of the rolling technological process on gripping conditions and origination of dangerous oscillations was carried out. Characteristics of rolling mode of strip of 2.0–0.45 × 970 mm dimension, accompanied by vibration was presented, as well as graphs of the strip oscillations in the process of stationary rolling and under conditions of vibrations origination presented. An assumption made, that during vibrations origination the gripping conditions of the strip by rollers are disturbed. It means that provision of the grip stationarity will decrease the risk of the vibrations originating at the rolling. The assumption was confirmed by the studies of the cold rolling at five-stand mill 1700 of Cherepovets steel-works. The calculations of the hearth of deformation parameters were made by application of an elaborated dynamic model of the rolling process. The higher probability of vibrations originating at the rolling of strips of smaller thickness explained. It was shown, that due to the strip length, the rolling of the thinner metal is accomplished at higher speeds, comparing with the rolling of thicker metal. In addition, it was shown that the friction coefficient value at that would promote increase of risk of non-stationary rolling mode originating. The support of stable friction conditions in the hearth of deformation is promoted by usage of chrome-plated working rollers and asymmetrical rolling.

Recent Progress and Future Research Direction of Nonlinear Dynamics and Bifurcation Analysis of Grid-Connected Power Converter Circuits and Systems

Since the discovery of nonlinear dynamics and chaotic behaviors of basic power converter circuits, stability analysis has been extended to more complex converter structures, paralleled and interconnected converters, microgrids, and power systems. While the analysis has long been identifying the parameters that cause various nonlinear phenomena, some work has shown direct relevance toward practical design of power converters, and control circuits. In this article, a review is conducted to highlight the key contributions of bifurcation analysis for power converter circuits and systems, and to discuss the ongoing work in this area.

Low cost, easy-to-replicate myringotomy tube insertion simulation model

IntroductionSimulation is an established part of modern surgical education. Several training centers have proposed different simulation models for myringotomy tube (MT) placement and validated their effectiveness in medical student and resident training. None is widely used. Early models were simple tubes that lacked important microsurgical elements. Newer simulators are more comprehensive, but are difficult and expensive to build. We present a MT placement simulator that is low cost, easy to construct with basic power tools and allows for acquisition of the most necessary MT placement skills. MethodsThe model incudes a rotating spherical “head”, a 4 mm oval speculum, a drilled-out working shaft similar in size to the external auditory canal, and a realistic paper tympanic membrane target, set at an anatomically correct angle. To evaluate the model's efficacy, we assessed the performance of 10 surgically naïve medical student volunteers before training and after 30 min of instruction with the model. Their speed was recorded and operative performance was assessed using a validated Global Rating Scale. ResultsAfter 30 min of practice on the model, there was significant improvement in MT placement skill scores and significant decrease in time for tube placement (p < 0.05). ConclusionThis MT placement simulation model is inexpensive and easy to build. Unlike existing planar models, it simulates patient head orientation, and requires realistic hand positioning on a 4 mm speculum. Practice with the model for 30 min resulted in statistically significant improvement in MT placement skill scores for inexperienced student surgeons.

Loop-Shaping Based Control for Switch Mode DC-DC Power Converters

Renewable energy sources require switching regulators as an interface to a load with high efficiency, small size, proper output regulation, and fast transient response. Moreover, due to the nonlinear behavior and switching nature of DC-DC power electronic converters, there is a need for high-performance control strategies. This work summarized the dynamic behavior for the three basic switch-mode DC-DC power converters operating in continuous conduction mode, i.e. buck, boost, and buck-boost. A controller was designed using loop-shaping based on current-mode control that consists of two feedback loops. A high-gain compensator with wide bandwidth was used in the inner current loop for fast transient response. A proportional-integral controller was used in the outer voltage loop for regulation purposes. A procedure was proposed for the parameters of the controller that ensures closed-loop stability and output voltage regulation. The design-oriented analysis was applied to the three basic switch-mode DC-DC power converters. Experimental results were obtained for a switching regulator with a boost converter of 150 W, which exhibits non-minimum phase behavior. The performance of the controller was tested for voltage regulation by applying large load changes.

Методика інженерних розрахунків параметрів обладнання для зневоднення твердих побутових відходів у сміттєвозі

A mathematical model of the operation of the solid domestic waste dewatering drive in a garbage truck is proposed. This model allows us to study the dynamics of this process and obtain regression equations for determining the nominal value of the angular velocity of the hydraulic motor. During the study there has been used the numerical method of Runge–Kutta–Vellberg of the fourth order with a variable step of integration, and regression results of one-factor experiments and other pair of dependencies with a selection of the best function of the 16 most common variants on the criterion of the maximum correlation coefficient. An analytical study of a simplified mathematical model of the operation of the solid domestic waste dewatering system in a garbage truck by solving a system of ordinary linear differential equations using Laplace transformations and by decomposing the expression into simple fractions allowed us to obtain analytical interdependencies of its main parameters, which can be used to perform preliminary design calculations of the parameters of this drive. When comparing the results obtained using full and simplified mathematical models for dewatering solid domestic waste in a garbage truck, in particular the angular velocity of the hydraulic motor, the error was 7,06 %, which is acceptable for performing preliminary design calculations of the main drive parameters. A scientifically-based method of design calculation of the drive for dewatering solid domestic waste in a garbage truck is proposed. This method allows to obtain the basic geometric, power and speed parameters and is one of the components for solving the problem of creating scientific and technical bases for designing highly efficient working bodies of machines for cleaning and primary processing of solid domestic waste. The main geometric, power and speed parameters of the drive for dewatering solid domestic waste in a garbage truck are obtained.

Available transfer capacity model and algorithm of the power grid with STATCOM installation

The optimization of the available transmission capacity (ATC) was considered in the power systems integrated with static synchronous compensator (STATCOM). A calculation method of ATC second-order cone programming (SOCP) based on Benders decomposition was proposed, aiming at the non-convexity and non-linearity in the optimization of the ATC of the power grid. The proposed method was divided into three stages. Firstly, the mathematical model of ATC considering the integration of the STATCOM is established. Secondly, the non-convex tidal current model is approximately converted into a convex optimization model by SOCP. Finally, the solution obtained by transforming the ATC model into two-stage models with basic state power flow constraints and N-1 power flow constraints using Benders decomposition method. The simulation results obtained from the IEEE-118 node system show that the proposed method can guarantee the feasibility of effectively regulating the grid transmission capacity of the power grid. It is also demonstrated that the installation of STATCOM can improve the system transmission capacity.

Design of Electric Power Line Drawing Algorithm

Abstract At present, the drawing of power lines is still in the state of semi-manual design, mainly completed by AutoCAD, which not only consumes human resources, but also has low efficiency. Therefore, this paper designs an automatic drawing software for power lines. It integrates drawing and data management. Based on the basic information of power lines, this software imports and automatically converts the basic power data (latitude and longitude data) containing GPS/BeidDou positioning information into the distance, direction, angle and other information of poles and cables. Then, it realizes the function of automatically drawing the power line graph according to the scale by multiple tree traversal algorithm. This software is easy to operate and reliable, and has achieved good results in practice.

Trends in global research in forest carbon sequestration: A bibliometric analysis

Abstract Based on the Web of Science Core Collection databases from 1990 to 2018, a scientometric analysis of 1,284 academic works related to forest carbon sequestration is carried out to characterize the intellectual landscape by identifying and revealing the basic characteristics, research power, intellectual base and research hotspots in this field. The results of this work show that: ① the number of publications in forest carbon sequestration research has increased rapidly and the research in this field is in its “growth stage”; Forest Ecology and Management is the most productive journal and Forestry is the most popular subject category; ② the most productive authors and institutions in this subject area are in the USA, China and Canada, with the Chinese Academy of Sciences being the key institution performing such research; ③ in the sample, 9 papers have played a key role in the evolution of the field and laid a solid foundation for future research; ④ Keyword clustering analysis showed that the main research topics in the domain of forest carbon sequestration could be summarized as: (a) temperate forest; (b) forest management; (c) uncertainty analysis; (d) forest floor; (e) REDD; (f) net primary productivity. Meanwhile, keyword bursts analysis showed that the new research hotspots or research frontiers mainly concentrated on changes in the carbon storage and carbon sequestration potential of secondary forests and tropical forests, plant litter carbon storage and contribution to total ecosystem carbon storage, and new national forest inventories (NFIs). Through in-depth analysis of forest carbon sequestration research, this paper provides a better understanding of development trends that have emerged in this field over the past 29 years, which can also offer reference for future research.

Advanced MPPT Algorithm for Distributed Photovoltaic Systems

The basic and adaptive maximum power point tracking algorithms have been studied for distributed photovoltaic systems to maximize the energy production of a photovoltaic (PV) module. However, the basic maximum power point tracking algorithms using a fixed step size, such as perturb and observe and incremental conductance, suffer from a trade-off between tracking accuracy and tracking speed. Although the adaptive maximum power point tracking algorithms using a variable step size improve the maximum power point tracking efficiency and dynamic response of the basic algorithms, these algorithms still have the oscillations at the maximum power point, because the variable step size is sensitive to external factors. Therefore, this paper proposes an enhanced maximum power point tracking algorithm that can have fast dynamic response, low oscillations, and high maximum power point tracking efficiency. To achieve these advantages, the proposed maximum power point tracking algorithm uses two methods that can apply the optimal step size to each operating range. In the operating range near the maximum power point, a small fixed step size is used to minimize the oscillations at the maximum power point. In contrast, in the operating range far from the maximum power point, a variable step size proportional to the slope of the power-voltage curve of PV module is used to achieve fast tracking speed under dynamic weather conditions. As a result, the proposed algorithm can achieve higher maximum power point tracking efficiency, faster dynamic response, and lower oscillations than the basic and adaptive algorithms. The theoretical analysis and performance of the proposed algorithm were verified by experimental results. In addition, the comparative experimental results of the proposed algorithm with the other maximum power point tracking algorithms show the superiority of the proposed algorithm.

КОНСТРУКТОРСКОЕ И ТЕХНОЛОГИЧЕСКОЕ ОБЕСПЕЧЕНИЕ ИЗГОТОВЛЕНИЯ КОРПУСА РАКЕТНОГО ДВИГАТЕЛЯ НА ТВЕРДОМ ТОПЛИВЕ ТИПА “КОКОН”

Rocket engines on firm fuel are widely applied in the rocket and space-rocket technics. The case is the basic bearing element of the engine on firm fuel and carries out functions of the chamber of combustion, and also is the basic power element of the engine and simultaneously a part of a power design of the rocket. In the article on firm fuel of type "cocoon", mission and requirements the description of a design of the case of the rocket engine results in elements of a design of case rocket engines on firm fuel of type "cocoon". It is determined the applied materials and technology requirements to them. The choice of constructional materials for each separate element and knot depends on many factors and the requirements shown to a product. Properties of composite material substantially depend as on parity between binding and reinforcing components, and from parameters of the technological process of their manufacturing. It is determined a technological route of manufacturing of case rocket engines on firm fuel of type "cocoon". The technological route of manufacturing of any product appreciably depends on applied materials, manufacture type, presence of an industrial base, a design of a product, its form, technical requirements, etc. It is determined the manufacturing of an internal heat-shielding covering of case rocket engines on firm fuel of type "cocoon". It is determined the manufacturing internal heat-shielding covering of the bottoms forward, back and a cylindrical part of the case. The internal heat-shielding covering of the bottoms of case rocket engines on firm fuel of type "cocoon" represents a multilayered design with flanges, cuffs, jacks. In this connection manufacturing heat-shielding covering of the bottoms is spent separately. Before calculation heat-shielding covering of a cylindrical part on prepared mandrel covers (technological and a fixing layer), technological covers of the forward and back bottoms keep within consistently and also are established heat-shielding covering the forward and back bottoms. It is determined the manufacturing of a power cover of the case, a cover of communication and joint knots. Power cover and the cover of communication of the case make spirally-ring "wet" winding of the carbon fiber impregnated epoxy resin, on winding the machine tool. Forward and back knots of a joint of the case are made by a method of winding of layers of carbon fabric. Layers of a carbon fabric alternate with ring and spiral layers of a carbon fiber carrying out a role of consolidation of layers of carbon fabric and communication of forward and back knots of a joint.

Quantitative transient stability assessment in microgrids combining both time-domain simulations and energy function analysis

Hybrid microgrids of the future comprise synchronous generators and inverter-based photovoltaics, battery storage systems etc. Interconnection of off-grid hybrid microgrids can provide economic benefits and increase security of supply. Both in the short-term and long-term planning phase as well as during operation, transient stability assessment (TSA) of such clustered hybrid microgrids is essential at different operating points. Quantitative TSA helps in, for example, optimal generation dispatching, adjusting clearing times in the protection systems, optimal clustering of microgrids etc. However, the existing five hybrid methods developed for transmission systems with certain assumptions and limitations, taking the advantages of both time-domain simulations and transient energy function (TEF), cannot be directly applied for microgrids. Although there could be less than ten synchronous generators in clustered hybrid microgrids, a detailed TSA in such systems is too complex to begin with. Hence, two basic power system models – one-machine infinite-bus system (OMIBS) and two-machine system (TMS) – with classical 2nd order and detailed 5th order modelling of diesel generators (DG) with and without controllers are studied in this paper. One of the aims is to get a better knowledge of the dynamic behaviour and analyse kinetic energy (KE) and potential energy (PE) profiles. The main goal is to develop a new hybrid method to define a stability margin (SM) and a stability degree (SD) for both the types of generator modelling. The stability analyses in the OMIBS show that, the influence of the generator modelling on the end results, i.e., SM and SD, is significant. The duration of the sub-transient state in DG might be of just several tens of milliseconds after the fault incident, but the indirect effect of the sub-transient short-circuit currents especially on speed governors until the end of the forward swing is substantial. In the TMS, the synchronous operation of the DG is strongly dependent on each other. The TEF and its components like KE and PE, which are applied individually to each DG, are inversely proportional to the inertia constants of the DG. It was shown not only graphically, but also by postulating and proving two propositions. Therefore, an important foundation regarding the TEF has been laid for the quantitative TSA in multi-machine clustered hybrid microgrids.

Resistive wall mode physics and control challenges in JT-60SA high scenarios

The superconducting tokamak JT-60SA is being built in Naka (Japan) under the Broader Approach Satellite Tokamak Programme jointly by Europe and Japan, and under the Japanese national programme. JT-60SA has an important supporting mission for the development of fusion energy. It will help in both the exploitation of ITER and in the definition of an optimized DEMO design. The focus of this work is set on high scenarios, in which kink-like instabilities (e.g. one or more resistive wall modes) are potentially unstable and possibly lead to disruptions. As a fundamental step to ensure the safe realization of high plasmas, modeling activities are being carried out for MHD stability and control. The drift-kinetic damping model in particular will be considered in the present work, with a stability study in Scenario 5-like plasmas carried out with MARS-F/K. Resistive wall mode (RWM) stability is found with this model for low plasma rotation and precession drift resonance with thermal ions. The dependence on normalized and flow profile is discussed. The challenge of active control is also addressed, taking advantage of the set of RWM control coils that JT-60SA will install. A dynamic simulator, based on the CarMa code, has been developed for feedback control modeling. A demonstration of this tool is given for one of the aforementioned plasmas. Stabilization of the most unstable RWM is achieved within basic power limits. Potential applications, results and latest development of this tool are discussed.

APPROXIMATE CALCULATION OF THE CIRCULAR SOIL CUTTING CAPACITY

Introduction. Rotary cultivators are necessary for circular soil cutting while forming the underlayment and slopes of highways. Therefore, the objective of the research is a theoretical substantiation of constructive and sensitive parameters for the rotary ripper. The researchers usually use synthesis method to evaluate theoretical evaluation of the energy consumption on the development of soil. The researchers also carry out an indicative calculation of basic design parameters and power drive of rotary ripper.Materials and methods. The author developed a methodology for calculating the indicative rotor power. Moreover, the author detected changes of the effective frontal sections of the working body in the process of the rotor circulation by means of the length measuring of a frontal section.Results. As a result, the author defined rational working parameters of circular cutting ground and calculated the angular velocity of the active working body. Moreover, the author also identified the required average torque and approximate rotor power.Discussion and conclusions. A simple and intuitive method based on accepted formulas of strength of materials, theoretical mechanics and other sciences is required for practical calculations of the working vehicles’ bodies. The author finds out that on the basis of the synthesis method the assessing energy expenditure on the development of soil may be defined, the analysis of the interaction with soil working bodies can be made.

IFRSs Adoption and its Influence on Financial Perfor-mance of Listed Consumer Goods Companies in Nigeria

AbstractObjective – This study examined the effect of IFRS adoption on financial performance of Listed Consumer Goods Companies in Nigeria. Design/methodology – The study selected 10 out of all the 28 Listed Consumer Goods Companies in Nigeria. Ex post facto research design was adopted and regression analysis through the aid of Eviews 9 was employed in analyzing the effect of IFRS adoption on performance of the selected listed companies. Results – The findings revealed that IFRS adoption has significant positive effect on return on total asset, IFRS adoption has negative insignificant effect on interest coverage ratio, significant positive effect on basic earnings power ratio and that IFRS adoption has negative insignificant effect on leverage. Based on the findings, the study concluded that IFRS adoption has joint significant effect on Return on asset, on Basic earnings power and on Interest coverage while the reverse was the case for financial leverage. Research limitations/implications – This study is limited in the context of consumer goods companies only. Future studies can extend the result of this study by investigating other industry in identifying the implication of IFRS adoption in their businesses.

Influence of part-to-part gaps in air distribution system on operation of DTH hammer

The authors illustrate the role of pneumatic percussive machines in drilling. The article presents the elementary diagram of down-the-hole (DTH) hammer with the marked places of air leakages in the system of air distribution and describes and their influence based on the research data. The variation in the basic power characteristics of the machine is given as function of the size of gaps in the sliding joints. It is shown that the machine design can be improved by means of using elastic valve to allow discharge of air working chambers during the idle stroke of the hammer.

Reliability Modeling Method for Lithium-ion Battery Packs Considering the Dependency of Cell Degradations Based on a Regression Model and Copulas.

Lithium-ion batteries are widely used as basic power supplies and storage units for large-scale electric drive products such as electric vehicles. Their reliability is directly related to the life and safe operation of the electric drive products. In fact, the cells have a dependent relationship with the degradation process and they affect the degradation rate of the entire battery pack, thereby affecting its reliability. At present, most research focuses on the reliability of battery packs and assumes that their cells are independent of each other, which may cause the reliability of the evaluation to deviate greatly from the actual level. In order to accurately assess the reliability of lithium-ion batteries, it is necessary to build a reliability model considering the dependency among cells for the overall degradation of lithium-ion battery packs. Therefore, in this study, based on a lithium-ion battery degradation test, the Wiener process is used to analyze the reliability of four basic configurations of lithium-ion battery packs. According to the degradation data of the battery packs, the Copula function is used to quantitatively describe the dependent relationship in the degradation process of a single battery, and the quantitative dependent relationship is combined with the reliability model to form a new reliability model. Finally, taking the battery system of Tesla S as an example, a feasible optimization method for battery pack design is provided based on the model constructed in this work.

A Data-Driven Methodology for Probabilistic Wind Power Ramp Forecasting

With increasing wind penetration, wind power ramps (WPRs) are currently drawing great attention to balancing authorities, since these wind ramps largely affect power system operations. To help better manage and dispatch the wind power, this paper develops a data-driven probabilistic WPR forecasting (p-WPRF) method based on a large number of simulated scenarios. A machine learning technique is first adopted to forecast the basic wind power forecasting scenario and produce the historical forecasting errors. To accurately model the distribution of wind power forecasting errors, a generalized Gaussian mixture model is developed and the cumulative distribution function (CDF) is also analytically deduced. The inverse transform method based on the CDF is used to generate a large number of forecasting error scenarios. An optimized swinging door algorithm is adopted to extract all the WPRs from the complete set of wind power forecasting scenarios. The p-WPRF is generated based on all generated scenarios under different weather and time conditions. Numerical simulations on publicly available wind power data show that the developed p-WPRF method can predict WPRs with a high level of reliability and accuracy.

Cause Analysis of Distance on Rural Power Network Voltage Based on Power Flow Model

In order to analyze the influence of long-distance power transmission on the terminal voltage of agricultural network, this paper establishes the low voltage model of agricultural network based on the basic power flow model, and obtains the semi-quantitative relationship between the terminal voltage deviation and various factors by formula derivation. By introducing reference data for calculation, the influence of distance factor on the voltage reduction of the rural power grid is obtained. Under the same active and reactive power transmission conditions, the farm network voltage gradually decreases with the increase of the length of the agricultural network feeder. On the other hand, for the same feeder length, as the active power increases, the farm network voltage gradually decreases. As the reactive power increases, the voltage of the rural network gradually decreases. The trend of the rural power grid voltage with the reduction of the active power is greater than the reactive power, that is, the same percentage of the active power and the reactive power change. The active power has a more significant effect on the voltage reduction of the rural power grid. Therefore, the active, reactive and feeder lengths will have an impact on the terminal voltage of the rural network. By reducing the radiation range of the feeder, the terminal voltage of the rural network can be effectively improved.