Toshihisa Shimizu

Bio: Toshihisa Shimizu is an academic researcher from Tokyo Metropolitan University. The author has contributed to research in topics: Inverter & Inductor. The author has an hindex of 30, co-authored 241 publications receiving 5517 citations. Previous affiliations of Toshihisa Shimizu include Japan Advanced Institute of Science and Technology & Tokyo Institute of Technology.

Topologies of single-phase inverters for small distributed power generators: an overview

Abstract: This paper presents an overview of single-phase inverters developed for small distributed power generators. The functions of inverters in distributed power generation (DG) systems include dc-ac conversion, output power quality assurance, various protection mechanisms, and system controls. Unique requirements for small distributed power generation systems include low cost, high efficiency and tolerance for an extremely wide range of input voltage variations. These requirements have driven the inverter development toward simpler topologies and structures, lower component counts, and tighter modular design. Both single-stage and multiple-stage inverters have been developed for power conversion in DG systems. Single-stage inverters offer simple structure and low cost, but suffer from a limited range of input voltage variations and are often characterized by compromised system performance. On the other hand, multiple-stage inverters accept a wide range of input voltage variations, but suffer from high cost, complicated structure and low efficiency. Various circuit topologies are presented, compared, and evaluated against the requirements of power decoupling and dual-grounding, the capabilities for grid-connected or/and stand-alone operations, and specific DG applications in this paper, along with the identification of recent development trends of single-phase inverters for distributed power generators.

Flyback-Type Single-Phase Utility Interactive Inverter With Power Pulsation Decoupling on the DC Input for an AC Photovoltaic Module System

Abstract: In recent years, interest in natural energy has grown in response to increased concern for the environment. Many kinds of inverter circuits and their control schemes for photovoltaic (PV) power generation systems have been studied. A conventional system employs a PV array in which many PV modules are connected in series to obtain sufficient dc input voltage for generating ac utility line voltage from an inverter circuit. However, the total power generated from the PV array is sometimes decreased remarkably when only a few modules are partially covered by shadows, thereby decreasing inherent current generation, and preventing the generation current from attaining its maximum value on the array. To overcome this drawback, an ac module strategy has been proposed. In this system, a low-power dc-ac utility interactive inverter is individually mounted on each PV module and operates so as to generate the maximum power from its corresponding PV module. Especially in the case of a single-phase utility interactive inverter, an electrolytic capacitor of large capacitance has been connected on the dc input bus in order to decouple the power pulsation caused by single-phase power generation to the utility line. However, especially during the summer season, the ac module inverters have to operate under a very high atmospheric temperature, and hence the lifetime of the inverter is shortened, because the electrolytic capacitor has a drastically shortened life when used in a high-temperature environment. Of course, we may be able to use film capacitors instead of the electrolytic capacitors if we can pay for the extreme large volume of the inverter. However, this is not a realistic solution for ac module systems. This paper proposes a novel flyback-type utility interactive inverter circuit topology suitable for ac module systems when its lifetime under high atmospheric temperature is taken into account. A most distinctive feature of the proposed system is that the decoupling of power pulsation is executed by an additional circuit that enables employment of film capacitors with small capacitance not only for the dc input line but also for the decoupling circuit, and hence the additional circuit is expected to extend the lifetime of the inverter. The proposed inverter circuit also enables realization of small volume, lightweight, and stable ac current injection into the utility line. A control method suitable for the proposed inverter is also proposed. The effectiveness of the proposed inverter is verified thorough P-SIM simulation and experiments on a 100-W prototype

Generation control circuit for photovoltaic modules

Abstract: Photovoltaic modules must generally be connected in series in order to produce the voltage required to efficiently drive an inverter. However, if even a very small part of photovoltaic module (PV module) is prevented from receiving light, the generation power of the PV module is decreased disproportionately. This greater than expected decrease occurs because PV modules which do not receive adequate light cannot operate on the normal operating point, but rather operate as loads. As a result, the total power from the PV modules is decreased if even only a small part of the PV modules are shaded. In the present paper, a novel circuit, referred to as the generation control circuit (GCC), which enables maximum power to be obtained from all of the PV modules even if some of the modules are prevented from receiving light. The proposed circuit enables the individual PV modules to operate effectively at the maximum power point tracking, irrespective of the series connected PV module system. In addition, the total generated power is shown experimentally to increase for the experimental set-up used in the present study.

A novel high-performance utility-interactive photovoltaic inverter system

Abstract: This paper presents a novel photovoltaic inverter that cannot only synchronize a sinusoidal AC output current with a utility line voltage, but also control the power generation of each photovoltaic module in an array. The proposed inverter system is composed of a half-bridge inverter at the utility interface and a novel generation control circuit which compensates for reductions in the output power of the system that are attributable to variations in the generation conditions of respective photovoltaic modules. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting the output power of the system. Furthermore, the generation control circuit attenuates low-frequency ripple voltage, which is caused by the half-bridge inverter, across the photovoltaic modules. Consequently, the output power of the system is increased due to the increase in average power generated by the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

Attenuation of Conducted EMI Emissions From an Inverter-Driven Motor

Abstract: This paper provides theoretical and experimental discussions on conducted electromagnetic interference (EMI) emissions from an inverter-driven motor rated at 400 V and 15 kW. It focuses on a line EMI filter and its combination with a motor EMI filter, along with their effects on attenuation of conducted emission voltage. When no EMI filter is connected, the motor drive cannot meet the conducted emission limits prescribed by Category 3 in the IEC61800-3 regulations. The reason is that the common-mode voltage generated by a voltage-source pulse width modulation (PWM) inverter causes a common-mode leakage current flowing into the ground wire lead through parasitic capacitors inside the motor. When the line EMI filter is connected, the motor drive can meet Category 3. The motor EMI filter eliminates the common-mode voltage from the motor terminals, thus bringing a drastic reduction to the leakage current. The combination of the two EMI filters can comply with the limits prescribed by Category 2, which are much stricter than those by Category 3.

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques

Abstract: The many different techniques for maximum power point tracking of photovoltaic (PV) arrays are discussed. The techniques are taken from the literature dating back to the earliest methods. It is shown that at least 19 distinct methods have been introduced in the literature, with many variations on implementation. This paper should serve as a convenient reference for future work in PV power generation.

A review of single-phase grid-connected inverters for photovoltaic modules

Abstract: This review focuses on inverter technologies for connecting photovoltaic (PV) modules to a single-phase grid. The inverters are categorized into four classifications: 1) the number of power processing stages in cascade; 2) the type of power decoupling between the PV module(s) and the single-phase grid; 3) whether they utilizes a transformer (either line or high frequency) or not; and 4) the type of grid-connected power stage. Various inverter topologies are presented, compared, and evaluated against demands, lifetime, component ratings, and cost. Finally, some of the topologies are pointed out as the best candidates for either single PV module or multiple PV module applications.

Interparticle Coupling Effect on the Surface Plasmon Resonance of Gold Nanoparticles: From Theory to Applications

Abstract: 12.2.2. Four-Wave Mixing (FWM) 4849 12.2.3. Dye Aggregation 4850 12.2.4. Optoelectronic Nanodevices 4850 12.3. Sensor 4851 12.3.1. Chemical Sensor 4851 12.3.2. Biological Sensor 4851 12.4. Catalysis 4852 13. Conclusion and Perspectives 4852 14. Abbreviations 4853 15. Acknowledgements 4854 16. References 4854 * Corresponding author E-mail: tpal@chem.iitkgp.ernet.in. † Raidighi College. § Indian Institute of Technology. 4797 Chem. Rev. 2007, 107, 4797−4862

Power electronics as efficient interface in dispersed power generation systems

Abstract: The global electrical energy consumption is rising and there is a steady increase of the demand on the power capacity, efficient production, distribution and utilization of energy. The traditional power systems are changing globally, a large number of dispersed generation (DG) units, including both renewable and nonrenewable energy sources such as wind turbines, photovoltaic (PV) generators, fuel cells, small hydro, wave generators, and gas/steam powered combined heat and power stations, are being integrated into power systems at the distribution level. Power electronics, the technology of efficiently processing electric power, play an essential part in the integration of the dispersed generation units for good efficiency and high performance of the power systems. This paper reviews the applications of power electronics in the integration of DG units, in particular, wind power, fuel cells and PV generators.