A Modular Single-phase Multistring Multilevel Inverter Topology for Distributed Energy Resources

AbstractThis Paper presents simulation analysis of single phase multilevel inverter for distributed energy resources(DER) system are small power generation tools, in order to reduce conversion losses, complexity of the circuit and to improve the size and cost of the system. The system involves a high step up converter is used to set up the voltage coming from the various DER's such as Fuel cell module and Photovoltaic module, this high voltage acts as input to the inverter. This system requires less number of switches as compare to conventional cascade H-bridge (CCHB) inverter. There are some advantages of this multilevel inverter such as improved output waveform, and lower Electromagnetic interference, lower switching power loss and Total Harmonic Distortion (THD)

Impedance Matching Method in Two-Stage Converters for Single Phase PV-Grid System

This paper presents the study on the impedance matching method in two-stage converters for single phase PV-grid system. The use of PV systems was to obtain the electrical power from the sunlight energy. The system consisted of a Buck-Boost DC-DC converter and a five-level inverter. A Buck-Boost DC-DC converter was used as a means of impedance matching to obtain the maximum power that, in this case, through a method by using the incremental conductance current control algorithm. Meanwhile a five-level inverter was used as an interface to the utilities.  By using this technique, the system came to be simple. The impedance of the power grid, a Buck-Boost DC-DC converter, and a five-level inverter were seen by PV mostly in the area of RMPP, enabling the maximum power produced by the PV to be delivered to the grid. To demonstrate the effectiveness of the design, the analysis and simulation results, furthermore, were provide

Fault Tolerant Multilevel Inverter Topologies with Energy Balancing Capability: Photovoltaic Application

The continuous increase in energy demand and depletion of conventional resources motivates the research towards the environment friendly renewable energy sources like solar and wind energy. These sources are best suitable for rural, urban and offshore locations, because of easy installation, less running cost and ample resources (sun light and wind). The remote locations are mostly islanded in nature and far away from technical expertise in case of troubleshooting. This motivates the research on development of fault tolerant converters. These fault tolerant converters increases the reliability, which provides the continuous power supply to critical loads. From the last few decades, the integration of multilevel inverters with renewable energy systems is also increasing because of advantages like, improved power quality, total harmonic distortion (THD) and reduced output filter size requirement. Employing conventional multilevel inverters for increasing the number of voltage levels increases the device count and isolated DC sources. As a result probability of semiconductor switch failure is more and energy balancing issue between sources, which in-turn degrades the reliability and performance of the inverter. The majority of conventional multilevel inverter topologies cannot address energy balancing issues between multiple photovoltaic (PV) sources, which may need because of partial shading, hotspots, uneven charging and discharging of associated batteries etc. If energy sharing not addressed effectively, the batteries which are connected to the shaded or faulty PV system will discharge faster which may cause total system shutdown and leads to under-utilization of healthier part of the system. To address these issues, fault tolerant multilevel inverter topologies with energy balancing capability are presented in this thesis. The major contributions of the proposed work are Single phase and three phase fault tolerant multilevel inverter topologies. viii Energy balancing between sources and dc off set minimization (or batteries) due to uneven charging and discharging of batteries for five-level inverter. Extending the fault tolerance and energy balancing for higher number of voltage levels. The first work of this thesis is focused to develop fault tolerant single phase and three phase multilevel inverter topologies for grid independent photovoltaic systems. The topologies are formed by using three-level and two-level half bridge inverters. The topology fed with multiple voltage sources formed by separate PV strings with MPPT charge controllers and associated batteries. Here the topologies are analyzed for different switch open circuit and/or source failures. The switching redundancy of the proposed inverters is utilized during fault condition for supplying power with lower voltage level so that critical loads are not affected. In general, the power generation in the individual PV systems may not be same at all the times, because of partial shading, local hotspots, wrong maximum power point tracking, dirt accumulation, aging etc. To address this issue energy balancing between individual sources is taken care with the help of redundant switching combinations of proposed five-level inverter carried out in second work. Because of partial shading the associated batteries with these panels will charge and discharge unevenly, which results voltage difference between terminal voltages of sources because of SOC difference. The energy balance between batteries is achieved for all operating conditions by selecting appropriate switching combination. For example during partial shading the associated battery with low SOC is discharged at slower rate than the battery with more SOC until both SOC’s are equal. This also helps in minimization of DC offset into the ac side output voltage. The mathematical analysis is presented for possible percentage of energy shared to load by both the sources during each voltage level. The third work provides single phase multilevel inverter with improved fault tolerance in terms of switch open circuit failures and energy balancing between sources. Generally multilevel inverters for photovoltaic (PV) applications are fed ix with multiple voltage sources. For majority of the multilevel inverters the load shared to individual voltage sources is not equal due to inverter structure and switching combination. This leads to under-utilization of the voltage sources. To address this issue optimal PV module distribution for multilevel inverters is proposed. Mathematical analysis is carried out for optimal sharing of PV resources for each voltage source. The proposed source distribution strategy ensures better utilization of each voltage source, as well as minimizes the control complexity for energy balancing issues. This topology requires four isolated DC-sources with a voltage magnitude of Vdc/4 (where Vdc is the voltage requirement for the conventional NPC multilevel inverter). These isolated DC voltage sources are realized with multiple PV strings. The operation of proposed multilevel single phase inverter is analyzed for different switch open-circuit failures. All the presented topologies are simulated using MATLAB/Simulink and the results are verified with laboratory prototyp

MATLAB-Simulink environment based power quality improvement in photovoltaic system using multilevel inverter

Introduction. In this world of technical advancement, conventional resources are at the stage of destruction. To avoid such problems, we are going to use an alternative energy source namely solar by photovoltaic effect. The demand for multilevel inverters increased as they are used for different dynamic (high) voltage and dynamic (high) power appliances as they are capable of producing the output wave shape with low total harmonic distortion. Novelty. A new multilevel inverter is used in adding a (bidirectional) two way switch in between the capacitor and a traditional H-bridge module. This produces a better sine wave. By series connection of these two H-bridge modules, nine levels output voltage including zero is possible. The purpose of the proposed topology is reduction in the number of switches and it gives the good result with comparatively less power loss when it is compared with the other normal basic traditional inverters of the same output quality. Methods. In this paper, sinusoidal pulse width modulation technique is used for the working of the switches in the multilevel inverter. The results are verified by using simulation and also experimental setup is done. From the results it is observed that the proposed topology with reduced number of switches gives lower electromagnetic interference, lower harmonic distortion. Practical value. The total harmonic distortion value in the simulation is 14.4 % and practically it is 13.8 %.Вступ. У світі технічного прогресу звичайні ресурси перебувають у стадії руйнації. Щоб уникнути таких проблем, ми збираємося використати альтернативне джерело енергії, а саме сонячну енергію з фотоелектричним ефектом. Попит на багаторівневі інвертори збільшився, оскільки вони використовуються для різних динамічних (високих) напруг та динамічних (високих) потужностей, оскільки вони здатні формувати вихідну форму хвилі з низьким гармонічним загальним спотворенням. Новизна. Новий багаторівневий інвертор використовується для додавання двостороннього перемикача між конденсатором і традиційним модулем Н-моста. Це дає найкращу синусоїду. При послідовному з’єднанні двох модулів Н-моста можливо дев’ять рівнів вихідної напруги, включаючи нуль. Метою запропонованої топології є зменшення кількості перемикачів, що дає хороший результат при порівняно менших втратах потужності порівняно з іншими традиційними звичайними інверторами з такою ж вихідною якістю. Методи. У цій статті для роботи перемикачів у багаторівневому інверторі використовується метод широтно-імпульсної синусоїдальної модуляції. Результати перевіряються за допомогою моделювання, а також виконується експеримент. З результатів видно, що пропонована топологія зі зменшеною кількістю перемикачів дає менші електромагнітні перешкоди, менші гармонійні спотворення. Практична цінність. Сумарне значення гармонійних спотворень при моделюванні складає 14,4 %, а практично – 13,8 %

Modular Medium-Voltage Grid-Connected Converter with Improved Switching Techniques for Solar Photovoltaic Systems

© 1982-2012 IEEE. The high-frequency common magnetic-link made of amorphous material, as a replacement for common dc-link, has been gaining considerable interest for the development of solar photovoltaic medium-voltage converters. Even though the common magnetic-link can almost maintain identical voltages at the secondary terminals, the power conversion system loses its modularity. Moreover, the development of high-capacity high-frequency inverter and power limit of the common magnetic-link due to leakage inductance are the main challenging issues. In this regard, a new concept of identical modular magnetic-links is proposed for high-power transmission and isolation between the low and the high voltage sides. Third harmonic injected sixty degree bus clamping pulse width modulation and third harmonic injected thirty degree bus clamping pulse width modulation techniques are proposed which show better frequency spectra as well as reduced switching loss. In this paper, precise loss estimation method is used to calculate switching and conduction losses of a modular multilevel cascaded converter. To ensure the feasibility of the new concepts, a reduced size of 5 kVA rating, three-phase, five-level, 1.2 kV converter is designed with two 2.5 kVA identical high-frequency magnetic-links using Metglas magnetic alloy-based cores

Adaptive hysteresis band current control of grid connected PV inverter

In this paper, adaptive hysteresis band current controller is implemented to control the current injected into the grid. Initially it was implemented by B.K Bose for control of the machine drive. Now it is implemented for the grid connected PV inverter, to control the current injected into Grid. It is well suitable for the distribution generation. The adaptive hysteresis band controller changes the bandwidth based on the modulating frequency, supply voltage, input DC voltage and slope of the reference current. Consequently, the controller generates pulses to the inverter. It is advantageous over the conventional hysteresis controller, as the switching frequency is maintained almost constant. Thereby quality of grid current is also improved. It is verified in time domain analysis of simulation using MATLAB

Switched Capacitor Nine-level inverter with reduced components for Grid connected PV systems using Fuzzy logic controller

The novel use of a three-phase switched capacitor SC nine-level inverter in a PV system is described in this article. It has a low input voltage, fewer components, and is grid-connected. The primary benefit of the suggested inverter is high voltage gain, which is attained by switching capacitors in series and parallel to raise the output voltage with the proper switching management. It is simpler to design a fuzzy logic controller to increase the infusion of solar energy into the electrical network. The MATLAB/Simulink environment's findings demonstrate that the suggested fuzzy logic controller performs well under a range of illumination levels. In comparison to the traditional PI controller, the total harmonic distortion (THD) obtained is less than the limit of 0.67 %. Good spectrum analysis and strong performance with fewer components are made possible by the nine-level SC inverter

Development of a boost-inverter converter under electromagnetic compatibility stress equipping a photovoltaic generator

Introduction. Static converters are among the most widely used equipment in several applications, for example, electric power transmission, motor speed variation, photovoltaic panels, which constitute the electronic components. The design of a power electronics device is done without any real means of predicting electromagnetic disturbances during the product development phase. This case-by-case development process is repeated until a solution is found that best respects all the electromagnetic compatibility constraints. The purpose is the development of a boost-inverter converter under electromagnetic compatibility constraints. The improvements made to the inverter are mainly in the control, the choice of power switches and the electromagnetic compatibility solutions brought to the device. The quality of the wave is improved by acting on the type of control and the choice of switches. Methods. In the first time, we have highlighted a comparison between two most frequently used power components (MOSFET and IGBT) in the inverter and the boost by simulation using ISIS and LT-spice softwares. The sinusoidal voltage with modulation circuit is greatly simplified by the use of the PIC16F876A microcontroller. In a second step, we validate the obtained results with experimental measurements. We start with the boost, then the inverter. In addition, the circuits made are housed in boxes to avoid accidental contact for people. The equipment is designed to isolate the load from the power supply in case of: over voltages, under voltages, high and low battery level and short circuits. Results. All the simulations were performed using the ISIS and LT-spice softwares. The obtained results are validated by experimental measurements performed in the ICEPS Laboratory at the University of Sidi Bel-Abbes in Algeria. The realization of a single-phase inverter with a pulse width modulation control, associated with a boost chopper and the waveforms of the current and voltage across each static converter its opening are presented. The sources of disturbances in power devices are at the origin of the temporal and frequency characteristics of the signals coming from the hot spots of the power switches and the resonances created during the switching of these elements.Вступ. Статичні перетворювачі відносяться до обладнання, що найбільш широко використовується в декількох застосуваннях, наприклад, для передачі електроенергії, зміни швидкості двигуна, у фотогальванічних панелях, які складають електронні компоненти. Проєкт устрою силової електроніки виконується без будь-яких реальних засобів прогнозування електромагнітних перешкод на етапі розробки продукту. Цей процес індивідуальної розробки повторюється доти, доки знайдено рішення, яке найкраще враховує всі обмеження електромагнітної сумісності. Метою є розробка підвищувально-інверторного перетворювача при обмеженнях за електромагнітною сумісністю. Удосконалення, внесені в інвертор, в основному стосуються управління, вибору силових вимикачів та рішень щодо електромагнітної сумісності, реалізованих у пристрої. Якість хвилі покращується за рахунок впливу на тип керування та вибір перемикачів. Методи. Вперше ми підкреслили порівняння між двома найбільш часто використовуваними силовими компонентами (MOSFET та IGBT) в інверторі та підвищенням шляхом моделювання з використанням програмного забезпечення ISIS та LT-spice. Синусоїдальна напруга зі схемою модуляції значно спрощується за рахунок використання мікроконтролера PIC16F876A. На другому етапі ми підтверджуємо отримані результати експериментальними вимірами. Починаємо з Boost, потім з інвертора. Крім того, виготовлені схеми розміщені в коробках, щоб уникнути випадкового дотику людей. Устаткування призначене для відключення навантаження від джерела живлення у разі: перенапруги, зниженої напруги, високого та низького рівня заряду батареї та короткого замикання. Результати. Усі розрахунки проводилися з використанням програм ISIS та LT-spice. Отримані результати підтверджені експериментальними вимірами, проведеними в лабораторії ICEPS Університету Сіді-Бель-Аббес в Алжирі. Представлено реалізацію однофазного інвертора з керуванням на базі широтно-імпульсної модуляції, пов'язаного з підвищуючим переривником, а також осцилограми струму та напруги на кожному відкритті його статичного перетворювача. Джерелами збурень у силових пристроях є часові та частотні характеристики сигналів, що надходять від гарячих точок силових ключів, та резонанси, що створюються при комутації цих елементів

A grid-connected asymmetrical cascaded H-bridge 81 level inverter with single PV unit and voltage splitting multi winding isolation transformer in marine applications

716-723In this paper, an asymmetrical cascaded H-bridge 81 level inverter powered by a single photo voltaic (PV) unit is presented. The PV unit drives an interleaved soft switched boost converter that drives a simple three level inverter, which in turn drives a multiple secondary winding transformer. The AC output of the four isolated secondary windings of the transformer is rectified and filtered to deliver four isolated DC voltages in the ratio 1:3:9:27. The system incorporates maximum power point tracking at the front end boost DC-DC converter level. Overall reduced THD is achieved by strategically spacing on the time axis, for each AC cycle, the discrete voltage levels of the 81 level inverter. The mathematical formulation, the results of simulation in the MATLAB/SIMULINK environment and the results of experimental verifications are provided