Power Quality Enhancement in Hybrid Photovoltaic-Battery System based on three–Level Inverter associated with DC bus Voltage Control

This modest paper presents a study on the energy quality produced by a hybrid system consisting of a Photovoltaic (PV) power source connected to a battery. A three-level inverter was used in the system studied for the purpose of improving the quality of energy injected into the grid and decreasing the Total Harmonic Distortion (THD). A Maximum Power Point Tracking (MPPT) algorithm based on a Fuzzy Logic Controller (FLC) is used for the purpose of ensuring optimal production of photovoltaic energy. In addition, another FLC controller is used to ensure DC bus stabilization. The considered system was implemented in the Matlab /SimPowerSystems environment. The results show the effectiveness of the proposed inverter at three levels in improving the quality of energy injected from the system into the grid.Peer reviewedFinal Published versio

New Topologies and Advanced Control of Power Electronic Converters for Renewable Energy based Microgrids

Solar energy-based microgrids are increasingly promising due to their many features, such as being environmentally friendly and having low operating costs. Power electronic converters, filters, and transformers are the key components to integrate the solar photovoltaic (PV) systems with the microgrids. The power electronic converters play an important role to reduce the size of the filter circuit and eliminate the use of the bulky and heavy traditional power frequency step-up transformer. These power converters also play a vital role to integrate the energy storage systems such as batteries and the superconducting magnetic energy storage (SMES) unit in a solar PV power-based microgrid. However, the performance of these power converters depends upon the switching technique and the power converter configuration. The switching techniques can improve the power quality, i.e. lower total harmonic distortion at the converter output waveform, reduce the converter power loss, and can effectively utilize the dc bus voltage, which helps to improve the power conversion efficiency of the power electronic converter. The power converter configuration can reduce the size of the power converter and make the power conversion system more efficient. In addition to the advanced switching technique, a supervisory control can also be integrated with these power converters to ensure the optimal power flow within the microgrid. First, this thesis reviews different existing power converter topologies with their switching techniques and control strategies for the grid integration of solar PV systems. To eliminate the use of the bulky and heavy line frequency step-up transformer to integrate solar PV systems to medium voltage grids, the high frequency magnetic linkbased medium voltage power converter topologies are discussed and compared based on their performance parameters. Moreover, switching and conduction losses are calculated to compare the performance of the switching techniques for the magnetic-linked power converter topologies. In this thesis, a new pulse width modulation technique has been proposed to integrate the SMES system with the solar PV system-based microgrid. The pulse width modulation technique is designed to provide reactive power into the network in an effective way. The modulation technique ensures lower total harmonic distortion (THD), lower switching loss, and better utilization of dc-bus voltage. The simulation and experimental results show the effectiveness of the proposed pulse width modulation technique. In this thesis, an improved version of the previously proposed switching technique has been designed for a transformer-less PV inverter. The improved switching technique can ensure effective active power flow into the network. A new switching scheme has been proposed for reactive power control to avoid unnecessary switching faced by the traditional switching technique in a transformer-less PV inverter. The proposed switching technique is based on the peak point value of the grid current and ensures lower switching loss compared to other switching techniques. In this thesis, a new magnetic-linked multilevel inverter has been designed to overcome the issues faced by the two-level inverters and traditional multilevel inverters. The proposed multilevel inverter utilizes the same number of electronic switches but fewer capacitors compared to the traditional multilevel inverters. The proposed multilevel inverter solves the capacitor voltage balancing and utilizes 25% more of the dc bus voltage compared to the traditional multilevel inverter, which reduces the power rating of the dc power source components and also extends the input voltage operating range of the inverter. An improved version magnetic-linked multilevel inverter is proposed in this thesis with a model predictive control technique. This multilevel inverter reduces both the number of switches and capacitors compared to the traditional multilevel inverter. This multilevel inverter also solves the capacitor voltage balancing issue and utilizes 50% more of the dc bus voltage compared to the traditional multilevel inverter. Finally, an energy management system has been designed for the developed power converter and control to achieve energy resiliency and minimum operating cost of the microgrid. The model predictive control-based energy management system utilizes the predicted load data, PV insolation data from web service, electricity price data, and battery state of charge data to select the battery charging and discharging pattern over the day. This model predictive control-based supervisory control with the advanced power electronic converter and control makes the PV energy-based microgrid more efficient and reliable

A Modified High Voltage Gain Quasi-Impedance Source Coupled Inductor Multilevel Inverter for Photovoltaic Application

publishedVersio

Mitigation of power quality issues due to high penetration of renewable energy sources in electric grid systems using three-phase APF/STATCOM technologies: a review.

This study summarizes an analytical review on the comparison of three-phase static compensator (STATCOM) and active power filter (APF) inverter topologies and their control schemes using industrial standards and advanced high-power configurations. Transformerless and reduced switch count topologies are the leading technologies in power electronics that aim to reduce system cost and offer the additional benefits of small volumetric size, lightweight and compact structure, and high reliability. A detailed comparison of the topologies, control strategies and implementation structures of grid-connected high-power converters is presented. However, reducing the number of power semiconductor devices, sensors, and control circuits requires complex control strategies. This study focuses on different topological devices, namely, passive filters, shunt and hybrid filters, and STATCOMs, which are typically used for power quality improvement. Additionally, appropriate control schemes, such as sinusoidal pulse width modulation (SPWM) and space vector PWM techniques, are selected. According to recent developments in shunt APF/STATCOM inverters, simulation and experimental results prove the effectiveness of APF/STATCOM systems for harmonic mitigation based on the defined limit in IEEE-519

A Modified High Voltage Gain Quasi-Impedance Source Coupled Inductor Multilevel Inverter for Photovoltaic Application.

The quasi-impedance source inverters/quasi-Z source inverters (Q-ZSIs) have shown improvement to overwhelmed shortcomings of regular voltage-source inverters (VSIs) and current-source inverters (CSIs) in terms of efficiency and buck-boost type operations. The Q-ZSIs encapsulated several significant merits against conventional ZSIs, i.e., realized buck/boost, inversion and power conditioning in a single power stage with improved reliability. The conventional inverters have two major problems; voltage harmonics and boosting capability, which make it impossible to prefer for renewable generation and general-purpose applications such as drive acceleration. This work has proposed a Q-ZSI with five-level six switches coupled inverter. The proposed Q-ZSI has the merits of operation, reduced passive components, higher voltage boosting capability and high efficiency. The modified space vector pulse width modulation (PWM) developed to achieve the desired control on the impedance network and inverter switching states. The proposed PWM integrates the boosting and regular inverter switching state within one sampling period. The PWM has merits such as reduction of coupled inductor size, total harmonic reduction with enhancing of the fundamental voltage profile. In comparison with other multilevel inverters (MLI), it utilizes only half of the power switch and a lower modulation index to attain higher voltage gain. The proposed inverter dealt with photovoltaic (PV) system for the stand-alone load. The proposed boost inverter topology, operating performance and control algorithm is theoretically investigated and validated through MATLAB/Simulink software and experimental upshots. The proposed topology is an attractive solution for the stand-alone and grid-connected system

Transformerless Inverter Topologies for Single-Phase Photovoltaic Systems:A Comparative Review

In photovoltaic (PV) applications, a transformer is often used to provide galvanic isolation and voltage ratio transformations between input and output. However, these conventional iron-and copper-based transformers increase the weight/size and cost of the inverter while reducing the efficiency and power density. It is therefore desirable to avoid using transformers in the inverter. However, additional care must be taken to avoid safety hazards such as ground fault currents and leakage currents, e.g., via the parasitic capacitor between the PV panel and ground. Consequently, the grid connected transformerless PV inverters must comply with strict safety standards such as IEEE 1547.1, VDE0126-1-1, EN 50106, IEC61727, and AS/N ZS 5033. Various transformerless inverters have been proposed recently to eliminate the leakage current using different techniques such as decoupling the dc from the ac side and/or clamping the common mode (CM) voltage (CMV) during the freewheeling period, or using common ground configurations. The permutations and combinations of various decoupling techniques with integrated voltage buck-boost for maximum power point tracking (MPPT) allow numerous new topologies and configurations which are often confusing and difficult to follow when seeking to select the right topology. Therefore, to present a clear picture on the development of transformerless inverters for the next-generation grid-connected PV systems, this paper aims to comprehensively review and classify various transformerless inverters with detailed analytical comparisons. To reinforce the findings and comparisons as well as to give more insight on the CM characteristics and leakage current, computer simulations of major transformerless inverter topologies have been performed in PLECS software. Moreover, the cost and size are analyzed properly and summarized in a table. Finally, efficiency and thermal analysis are provided with a general summary as well as a technology roadmap.</p

Improvements on the carrier-based control method for a three-level T-type, quasi-impedance-source inverter

The boost feature that characterizes Z-source and quasi-Z-source converters is usually achieved by means of a proper insertion of short-circuit states in the full DC-link. In this work, a novel pulse width modulation carrier-based strategy for a three-phase, three-level T-type, quasi-Z-source inverter is introduced, based on the addition of alternate short-circuits in the two halves of the DC-link bus. This technique achieves better performance, less electromagnetic interference, and lower harmonic distortion of the output line-to-line voltage compared to the traditional methods based on the full DC-link shoot-through. At the same time, generating the switching states is to easy implement. The proposed strategy permits the use of electronic devices with lower blocking voltage capability, thus improving converter reliability, size, and cost. The new method may be implemented in another multilevel inverter with an impedance-source network as well. A comprehensive simulation study is performed in order to validate the adopted method, with different inverter input voltages, which is taken as representative of a photovoltaic array. Comparisons are conducted with conventional strategy insertions using the same topology in order to show the improvements achieved.• Junta de Extremadura (Regional Government), Spain. Programa de Becas de Movilidad para Personal Docente e Investigador de la Comunidad Autónoma de Extremadura 2018, por el fondo para el grupo de investigación (GR18087) y el proyecto regional (IB18067). • Agencia Estatal de Investigación (AEI) y Fondo Europeo de Desarrollo Regional (FEDER) españoles, bajo el Proyecto TEC2016-77632-C3-1-R (AEI / FEDER, UE), y a través de FCT bajo los contratos UID / CEC / 50021/2019 , Pest-E / EEI / LA0021 / 2014 y UID / Multi / 00308/2019.peerReviewe

Bipolar DC output fed grounded DC-AC converter for photovoltaic application

Introduction. In recent years the usage of electricity has increased tremendously as the electrical needs and loads got increased. Hence the researchers focused on the electricity generation from renewable sources in order to promote sustainable green environment. Owing to the lesser cost and more reliable high efficiency system with reduced use of equipments became prominent for the grid connected photovoltaic single phase systems. The novelty of this proposed converters are to reduce total power loss and to analyze the performance of the converter under various modulation index and to have lesser harmonics using sinusoidal pulse width modulation technique for both T-type and F-type inverter. Interest of the work is to merge two DC-DC converters which have same output voltage in order to have transformer less utilization of power. This has given pathway to develop a new DC-DC converter network by merging the common input nodes of CUK and SEPIC converter. Purpose. This similar structure of both converters made it easy to combine the input stages of and to get bipolar output. Methods. Here we can get bipolar output without the utilization of transformer which minimizes the overall size of the proposed system. In this paper, a combined CUK-SEPIC based grid connected transformerless inverter for photovoltaic application is suggested. Results. The suggested converter is simulated using MATLAB and the results were discussed. Further the circuit is extended with a 1 kW F-type inverter to demonstrate grid connection of the converter. Practical value. This converter can be implemented for photovoltaic applications for obtaining the bipolar DC output from the DC source.Вступ. В останні роки використання електроенергії значно зросло, оскільки потреби в електроенергії та навантаження збільшились. Тому дослідники зосередилися на виробництві електроенергії з відновлюваних джерел, щоб сприяти стійкому зеленому середовищу. Через меншу вартість та більш надійну високоефективну систему зі зменшеним використанням обладнання набули популярності фотоелектричні однофазні системи, підключені до мережі. Новизна пропонованих перетворювачів полягає у зниженні загальних втрат потужності та аналізі характеристик перетворювача при різних індексах модуляції, а також у зменшенні гармонік з використанням методу широтно-імпульсної модуляції синусоїдального типу для інверторів як Т-типу, так і F-типу. Інтерес роботи полягає в об'єднанні двох перетворювачів постійного струму з однаковою вихідною напругою, щоб мати менше використання потужності трансформатора. Це дозволило розробити нову мережу перетворювачів постійного струму шляхом об'єднання загальних вхідних вузлів перетворювача CUK та SEPIC. Мета. Подібна структура обох перетворювачів дозволила легко поєднати вхідні каскади та отримати біполярний вихідний сигнал. Методи. Тут ми можемо отримати біполярний вихід без використання трансформатора, що мінімізує загальний розмір пропонованої системи. У цій статті пропонується комбінований безтрансформаторний інвертор на основі CUK-SEPIC, підключений до мережі, для фотоелектричних застосувань. Результати. Пропонований перетворювач моделюється за допомогою MATLAB, результати обговорюються. Далі схема розширена інвертором F-типу потужністю 1 кВт, щоб продемонструвати підключення перетворювача до мережі. Практична цінність. Цей перетворювач може бути реалізований для фотоелектричних застосувань для отримання біполярного виходу постійного струму джерела постійного струму