Dynamic modeling of DC-DC converters with peak current control in double-stage photovoltaic grid-connected inverters

In photovoltaic (PV) double-stage grid-connected inverters a high-frequency DC-DC isolation and voltage step-up stage is commonly used between the panel and the grid-connected inverter. This paper is focused on the modeling and control design of DC-DC converters with Peak Current mode Control (PCC) and an external control loop of the PV panel voltage, which works following a voltage reference provided by a maximum power point tracking (MPPT) algorithm. In the proposed overall control structure the output voltage of the DC-DC converter is regulated by the grid-connected inverter. Therefore, the inverter may be considered as a constant voltage load for the development of the small-signal model of the DC-DC converter, whereas the PV panel is considered as a negative resistance. The sensitivity of the control loops to variations of the power extracted from the PV panel and of its voltage is studied. The theoretical analysis is corroborated by frequency response measurements on a 230 W experimental inverter working from a single PV panel. The inverter is based on a Flyback DC-DC converter operating in discontinuous conduction mode (DCM) followed by a PWM full-bridge single-phase inverter. The time response of the whole system (DC-DC + inverter) is also shown to validate the concept. Copyright © 2011 John Wiley & Sons, Ltd. In photovoltaic (PV) double-stage gridconnected inverters a high-frequency DC-DC isolation and voltage step-up stage is commonly used between the panel and the grid-connected inverter. This paper is focused on the modeling and control design of DC-DC converters with Peak Current mode Control (PCC) and an external control loop of the PV panel voltage, which works following a voltage reference provided by a maximum power point tracking (MPPT) algorithm. The sensitivity of the control loops to variations of the power extracted from the PV panel and of its voltage is studied. Copyright © 2011 John Wiley & Sons, Ltd. Copyright © 2011 John Wiley & Sons, Ltd.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) under grant ENE2009-13998-C02-02. The company AUSTRIAMICROSYSTEMS co-financed this project.Garcerá Sanfeliú, G.; González Medina, R.; Figueres Amorós, E.; Sandía Paredes, J. (2012). Dynamic modeling of DC-DC converters with peak current control in double-stage photovoltaic grid-connected inverters. International Journal of Circuit Theory and Applications. 40(8):793-813. https://doi.org/10.1002/cta.756S793813408Carrasco, J. M., Franquelo, L. G., Bialasiewicz, J. T., Galvan, E., PortilloGuisado, R. C., Prats, M. A. M., … Moreno-Alfonso, N. (2006). Power-Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey. 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Back-to-back Converter Control of Grid-connected Wind Turbine to Mitigate Voltage Drop Caused by Faults

Power electronic converters enable wind turbines, operating at variable speed, to generate electricity more efficiently. Among variable speed operating turbine generators, permanent magnetic synchronous generator (PMSG) has got more attentions due to low cost and maintenance requirements. In addition, the converter in a wind turbine with PMSG decouples the turbine from the power grid, which favors them for grid codes. In this paper, the performance of back-to-back (B2B) converter control of a wind turbine system with PMSG is investigated on a faulty grid. The switching strategy of the grid side converter is designed to improve voltage drop caused by the fault in the grid while the maximum available active power of wind turbine system is injected to the grid and the DC link voltage in the converter is regulated. The methodology of the converter control is elaborated in details and its performance on a sample faulty grid is assessed through simulation

Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio

Modulation techniques for multilevel converters can create distorted output voltages and currents if the DC link voltages are unbalanced. This situation can be avoided if the instantaneous DC voltage error is not taken into account in the modulation process. This paper proposes a feed-forward space vector modulation method for a single-phase multilevel cascade converter. Using this modulation technique, the modulated output voltage of the power converter always generates the reference determined by the controller even in worst case voltage unbalance conditions. In addition the possibility of optimizing the DC voltage ratio between the H-bridges of the power converter is introduced. Experimental results from a 5kVA prototype are presented in order to validate the proposed modulation technique

Bolts connection technique of bamboo in construction work

The construction industry is increasingly developing and growing rapidly with more advanced technologies. The world timber demand is increasing at a rapid rate but the timber supply is however depleting. It has been found through research that bamboo can suitably replace timber and other materials in constructions. This study was conducted to investigate the structural strength of bamboo connections involving only spliced joint and compared with control samples strength of bamboo which were not connected. Bending test was conducted on four types of bamboo connection structures which werehalf-lapped splice joint using 3 bolts, half-lapped splice joint using 2 bolts, side plate splice joint, sleeves and insert joint and control sample bamboo. Every connection had six samples to determine the structural strength of the bamboo connection. From the tests conducted, the maximum load that can be borne by the bamboo structure and the bending ofthe bamboo structure will be obtained. Data were compared with the theoretical calculation based on the study of Janssen's. The connection structure that can bear maximum load was sleeves and inserts which was 5.997 kN. The control samples bamboo maximum load was 4.504 kN. Meanwhile, half-lapped splice joint using 3 bolts and 2 bolts were 4.789 kN and 4.04 kN. Structural connections that carriedthe lowest load was side plate splice joint which was only 2.659 kN.Compared with the bending moment of Janssen’s theory, all the connections did not exceed the maximum allowable bending moment. This showed that the study was in accordance with the standards approved by Janssen's theory. The study found that the structure of connections that can be used in the construction work was sleeves and inserts

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Modular generator and converter topologies are being pursued for large offshore wind turbines to achieve fault tolerance and high reliability. A centralized controller presents a single critical point of failure which has prevented a truly modular and fault tolerant system from being obtained. This study analyses the inverter circuit control requirements during normal operation and grid fault ride-through, and proposes a distributed controller design to allow inverter modules to operate independently of each other. All the modules independently estimate the grid voltage magnitude and position, and the modules are synchronised together over a CAN bus. The CAN bus is also used to interleave the PWM switching of the modules and synchronise the ADC sampling. The controller structure and algorithms are tested by laboratory experiments with respect to normal operation, initial synchronization to the grid, module fault tolerance and grid fault ride-through

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In this paper, a single-phase photovoltaic (PV) inverter fed by a boost converter to supply a freezer motor with variable DC input is investigated. The proposed circuit has two stages. Firstly, the DC output of the PV panel that varies between 150 and 300 V will be applied to the boost converter. The boost converter will boost the input voltage to a fixed 300 V DC. Next, this voltage is supplied to the single-phase full-bridge inverter to obtain 230 V AC. In the end, The output of the inverter will feed a freezer motor. The PV panels can be stand-alone or grid-connected. The grid-connected PV is divided into two categories, such as with a transformer and without a transformer, a transformer type has galvanic isolation resulting in increasing the security and also provides no further DC current toward the grid, but it is expensive, heavy and bulky. The transformerless type holds high efficiency and it is cheaper, but it suffers from leakage current between PV and the grid. This paper proposes a stand-alone direct use of PV to supply a freezer; therefore, no grid connection will result in no leakage current between the PV and Grid. The proposed circuit has some features such as no filtering circuit at the output of the inverter, no battery in the system, DC-link instead of AC link that reduces no-loads, having a higher efficiency, and holding enough energy in the DC-link capacitor to get the motor started. The circuit uses no transformers, thus, it is cheaper and has a smaller size. In addition, the system does not require a complex pulse width modulation (PWM) technique, because the motor can operate with a pulsed waveform. The control strategy uses the PWM signal with the desired timing. With this type of square wave, the harmonics (5th and 7th) of the voltage are reduced. The experimental and simulation results are presented to verify the feasibility of the proposed strategy

Penghasilan modul pembelajaran kendiri bahan dan binaan berasaskan web

Perkembangan teknologi maklumat dalam dunia pendidikan tidak Iagi boleh dinafikan pada masa kini. Keperluan yang meningkat dalam sistem pembelajaran dan pengajaran memerlukan mereka yang terlibat memberi sepenuh tumpuan terhadap mata pelajaran bagi mencapai matlamat, untuk tujuan ini modul pembelajaran kendiri di hasilkan bagi membantu memudahkan pelajar dan pensyarah dalam mata pelajaran Bahan dan Binaan agar dapat mengikuti pelajaran tersebut secara berkesan tanpa membuang masa. Seramai 35 orang pelajar diploma kejuruteraan Awam Politeknik Sultan Abdul Halim Muadzam Shah , Jitra Kedah terlibat sebagai responden. Statistik deskriptif digunakan dalam mengumpul dan menganalisis data. Secara keseluruhannya dari hasil kajian, menunjukkan para pelajar memberikan maklum balas yang positif terhadap modul pembelajaran kendiri Bahan dan Binaan berasaskan web ini. Dari hasil kajian ini juga didapati bahawa kebanyakan pelajar lebih berminat terhadap menggunakan media yang pelbagai seperti teks, audio dan visual. Walau bagaimana pun masih terdapat beberapa aspek yang perlu diperbaiki untuk memantapkan modul pembelajaran kendiri ini. Bagi menyokong perkembangan dan penggunaan teknologi maklumat dalam pendidikan keijasama daripada pelbagai pihak seperti Kementerian dan Politeknik sendiri diperlukan terutama dari segi kemudahan komputer, kursus penggunaan perisian dan sebagainya.ini adalah penting bagi melahirkan graduan yang berkualiti dan mempunyai pengetahuan yang meluas dalam bidang teknologi pada masa akan datang

Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

A plug-and-play ripple mitigation approach for DC-links in hybrid systems

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