Alexander Sergeevich Tonkoshkur

The results of experimental research on the influence of the features of the electrical circuit parameters of the solar module on the functioning of its passive photocell with a parallel-connected bypass critical thermistor as a method of increasing the solar module reliability of are presented. Glass-ceramic materials based on vanadium dioxide and vanadium-phosphate glass V2O5-P2O5 were used as thermistor, which change the electrical resistance in leaps and bounds by 1.5-2 orders of magnitude in the temperature range of 70 0С. The main attention is paid to the study of the patterns of behavior of the functional electrical and thermal characteristics of such elements depending on the amplitude of overvoltage and load resistance. It was found that as the amplitude of the overvoltage on the passive (shaded or damaged) photocell increases, the duration of the process of switching the bypass thermistor to the highly conductive state decreases, the voltage drop after switching decreases sharply (to values not exceeding 2 V) and changes weakly. An increase in the load resistance leads to a decrease in the current through the thermistor and an increase in the duration of the transient process. With thermal contact between the passive photocell and the bypass thermistor, switching is observed at lower overvoltages. In the absence of such a contact, the temperature to which the photocell is heated changes insignificantly in a steady state. Представлено результати експериментальних досліджень впливу особливостей параметрів електричного кола сонячного модуля на функціонування його пасивного фотоелемента з паралельно підключеним байпасним критичним терморезистором як методу підвищення надійності роботи сонячного модуля. Як терморезистор використовували склокерамічні матеріали на основі діоксиду ванадію та ванадій-фосфатного скла V2O5-P2O5, що стрибкоподібно змінюють величину електричного опору на 1,5−2 порядки в області температури 70 0С. Основну увагу приділено вивченню закономірностей поведінки функціональних електричних і теплових характеристик таких елементів від амплітуди перенапруги та опору навантаження. Встановлено, що зі зростанням амплітуди перенапруги на пасивному (затіненому або пошкодженому) фотоелементі тривалість процесу перемикання байпасного терморезистора у високопровідний стан зменшується, падіння напруги після перемикання різко знижується (до величин, що не перевищують 2 В) та слабко змінюється. Збільшення опору навантаження зумовлює зниження струму через терморезистор і збільшення тривалості перехідного процесу. При тепловому контакті між пасивним фотоелементом і байпасним терморезистором перемикання спостерігається за менших перенапруг. За відсутності такого контакту температура, до якої нагрівається фотоелемент, у сталому стані змінюється несуттєво.

The object of research is the development of a specialized measuring information system for the study and control of relaxation processes in materials and technical systems. The purpose of the work is the use of computer technologies to eliminate routine operations associated with the processing of experimental data, increase the speed, accuracy and information content of the process of studying the control of gas sensors. A variant of using computer data processing to automate the processing and primary analysis of experimental data of scientific research and control of the physicochemical parameters of gas-sensitive materials is proposed. The developed computer data processing system provides a practical opportunity to use the measurements of the kinetic characteristics of the gas sensitivity of gas sensors for their experimental research and control and, thus, to achieve higher accuracy and information content. The testing of the developed information-measuring system confirmed its operability and compliance with the requirements for improving the accuracy and speed of the processing process.

Purpose: The purpose of this study is to model the dependences of the output voltage, temperature, current and electrical power dissipation of a voltage limiter based on a two-layer varistor–posistor structure on time and analysis the influence of operating modes and design parameters of such a limiter on these characteristics.Design/methodology/approach: The behavior of the limiting voltage, temperature and other parameters of the voltage limiter when an input constant overvoltage is applied is studied by the simulation method. The voltage limiter was a two-layer construction. One layer was a zinc oxide ceramic varistor. The second layer was a posistor polymer composite with a nanocarbon filler of PolySwitch technology.Findings: The output voltage across the varistor layer decreases and reaches some fixed value related to its breakdown voltage after applying a constant overvoltage to the structure over time. The temperature of the structure increases to some steady state value, while the current decreases significantly. The amplitude of the transient current pulse increases, its duration and energy of the transient process decrease with increasing overvoltage. An increase in the internal resistance of the overvoltage source can cause a decrease in the amplitude and an increase in the duration of transient currents.Originality/value: The ranges of values for the activation energy of conduction of the varistor layer in weak electric fields, the intensity of heat exchange between the structure under study and the environment are determined to ensure the stable operation of this structure as a voltage limiter. The results obtained make it possible to select the necessary parameters of the indicated structures to ensure the required operating modes of the voltage limiter for various applications.

The experience of operating solar arrays indicates the need to solve the problem of creating effective and reliable switching elements to block defective and damaged photovoltaic cells. Available methods of solving this problem (for example, the use of transistor switches, electronic systems, etc.) either do not completely solve it, or are expensive. The tasks of increasing the reliability and efficiency of switching elements, preventing the destruction of photovoltaic cells which occurs during heating by dark current ("hot spots" and fire hazardous situations) are relevant. Recently, one of the promising solutions of this problem is the use of additional devices for isolating inactive (shaded or defective) areas of both separate photovoltaic cells and their modules. These devices are PPTC (polymeric positive temperature coefficient) resettable fuses of PolySwitch type, which are polymer composites with nanoscale carbon fillers. The basic functional property of PPTC fuse is an abrupt increase in electrical resistance by several orders of magnitude when a temperature is reached and a return to the initial high conductive state when the temperature drops. The advantages of such structures based on polymer composites with nanocarbon fillers include: – close to the metal resistance to the switching temperature and to the resistance of the insulator above the specified temperature; – possibility of realization in the form of discrete elements and continuous film-tapes (that is important at the decision of problems of realization of isolation of defective local area of the separate photovoltaic cell); – reaction in the form of temporary isolation of separate components of the solar array to increase their temperature. The research results are presented and the concept of overload protection by using resettable fuses based on polymer nanocomposite materials with nanocarbon fillers is substantiated in this paper. In particular, the expediency of series connection of PolySwitch fuses to photovoltaic modules with parallel connection of their strings is shown to prevent an abnormal situation, namely, a complete loss of electrical energy generated by such a string, which can occur when one of its modules is short-circuited. The circuit solutions in the form of combined structure based on layers of a varistor ceramics and a posistor polymer nanocomposite with carbon filler being in thermal contact are investigated. The prospect of its use to protect photovoltaic cells with a high reverse resistance from overvoltage is established. The problem of protection against local overheating in photovoltaic cells (or their parallel connections) by physical and technological methods, in particular, by creating photovoltaic cells with a built-in layer based on a posistor composite being in thermal contact with it, is analyzed. In general, the described results represent a new direction in the field of improving photovoltaic systems, in particular, in terms of increasing their efficiency, operating time and reliability by using solid-state devices based on polymer posistor nanocomposites and varistor ceramics as means of their protection from electrical and thermal overloads. Keywords: SOLAR ARRAY, PHOTOVOLTAIC MODULE, PHOTOVOLTAIC CELL, ELECTRIC OVERLOAD, POLYMER POSISTOR NANOCOMPOSITE, HOT SPOT, VARISTOR CERAMICS

Актуальность. Имеющиеся на настоящий момент результаты моделирования и экспериментальные данные свидетельствуют, что обводные диоды в подпанельных строках фотоэлектрических элементов не полностью защищают от появления «горячих пятен». Обводные диоды более эффективны для предотвращения «горячих пятен» при очень коротких длинах строк ФЭП, что не применяется в современной конструкции панелей из экономических соображений. Поэтому необходимо повышения надежности солнечных батарей, включая устранение нештатных (пожароопасных) ситуаций на основе разработки методов и средств предотвращения токовых перегрузок в их фотоэлектрических системах на основе новых подходов. Цель. Разработка универсального подхода для минимизации токовых перегрузок в фотоэлектрических системах солнечных батарей путем применения недорогостоящих элементов функциональной электроники, в частности, относительно новых и, получивших широкое распространение, самовосстанавливающихся предохранителей типа “Polyswith”. Метод. Предложено схемное решение и методом моделирования обоснованы возможности использования предохранителей типа Polyswitch для предотвращения и минимизации токовых перегрузок в фотоэлектрических системах солнечных батарей. Результаты. Проанализировано влияние величины сопротивления в проводящем состоянии и тока срабатывания предохранителей на вольт-амперные и вольт-ваттные характеристики параллельных соединений фотоэлектрических преобразователей и их модулей. Разработана математическая модель схемного решения и проведено моделирование его основных характеристик при использовании типичных параметров фотоэлектрических преобразователей на основе монокристаллического кремния и коммерческих самовосстанавливающихся предохранителей. Проанализировано влияние величины сопротивления в проводящем состоянии и тока срабатывания СВП на ВАХ и ВВХ параллельного соединения фотоэлектрических компонентов солнечных батарей. Выводы. Показано, что эффективное ограничение тока при наличии короткого замыкания при таком соединении фотоэлектрических компонент может быть реализовано при выполнении следующих условий: – сопротивление предохранителя в проводящем состоянии значительно меньше параллельного соединения последовательных сопротивлений фотоэлектрических компонент; – ток срабатывания предохранителя должен быть больше тока короткого замыкания отдельного фотоэлектрического компонента и меньше тока их параллельного соединения. Библ. 26, рис. 5, табл. 1.

Purpose: The purpose of this paper is to minimize and prevent current overloads (including the elimination of abnormal and fire hazardous situations) in photovoltaic solar arrays by using low-cost functional electronic elements, in particular, the new PolySwitch PPTC fuses. Design/methodology/approach: The modeling method has been used to investigate the circuit solution of the use of PolySwitch type fuses to prevent and minimize current overloads in photovoltaic solar arrays. Findings: It is shown that the limitation of the short-circuit current with parallel connection of photovoltaic components (photovoltaic cells or their modules) can be implemented when the following conditions are met: the resistance of the fuse in the conducting state is much lesser than the parallel connection of the series resistances of the photovoltaic components; and the tripping current of the fuse must be greater than the maximum current of the separate photovoltaic components and lesser than the current of a parallel connection of several photovoltaic components. Originality/value: The influence of the magnitude of the resistance in the conducting state and the response current of the fuses to the current–voltage and volt–watt characteristics of parallel connections of the photovoltaic components (photovoltaic cells or their modules) is analyzed. The modeling results are confirmed by experimental data on the transformation research of light current–voltage and volt–watt characteristics of parallel connections of industrial photovoltaic modules using resettable fuses of the PolySwitch type.

Purpose: The purpose of this paper is to develop the models of the dielectric permittivity dispersion of heterogeneous systems based on semiconductors to a level that would allow to apply effectively the method of broadband dielectric spectroscopy for the study of electronic processes in ceramic and composite materials.Design/methodology/approach: The new approach for determining the complex dielectric permittivity of heterogeneous systems with semiconductor particles is used. It includes finding the analytical expression of the effective dielectric permittivity of the separate semiconductor particle of spherical shape. This approach takes into account the polarization of the free charge carriers in this particle, including capturing to localized electron states. This enabled the authors to use the known equations for complex dielectric permittivity of two-component matrix systems and statistical mixtures.Findings: The presented dispersion equations establish the relationship between the parameters of the dielectric spectrum and electronic processes in the structures like semiconductor particles in a dielectric matrix in a wide frequency range. Conditions of manifestation and location of the different dispersion regions of the complex dielectric heterogeneous systems based on semiconductors in the frequency axis and their features are established. The most high-frequency dispersion region corresponds to the separation of free charge carriers at polarization. After this region in the direction of reducing of the frequency, the dispersion regions caused by recharge bulk and/or surface localized states follow. The most low-frequency dispersion region is caused by recharging electron traps in the boundary layer of the dielectric matrix.Originality/value: Dielectric dispersion models are developed that are associated with: electronic processes of separation of free charge carriers in the semiconductor component, recapture of free charge carriers in the localized electronic states in bulk and on the surface of the semiconductor and also boundary layers of the dielectric at the polarization. The authors have analyzed to situations that correspond applicable and promising materials: varistor ceramics and composite structure with conductive and semiconductor fillers. The modelling results correspond to the existing level of understanding of the electron phenomena in matrix systems and statistical mixtures based on semiconductors. It allows to raise efficiency of research and control properties of heterogeneous materials by dielectric spectroscopy.