Making isolated renewable energy systems more reliable Luiz A. de S. Ribeiro , Osvaldo R. Saavedra, Shigeaki, José G. de Matos, Guilherme Bonan Electrical Energy Institute, Federal University of Maranhão, São Luís, MA, Brazil R&D Department, CP Eletrônica S.A, Porto Alegre, RS, Brazil

Introduction The supply of electricity to isolated communities in Brazil and other developing countries, in general, is still done in a precarious way, using diesel generators, which operate for 3e4 h a day [1,2]. This has happened mostly due to the high cost associated with the expansion of the conventional power grid to these communities. In some cases, technical and environmental constraints also have been factors that have prevented the full electrical service in these communities, especially those located on oceanic islands. For societies to have or attempt to maintain a sustainable development it is necessary a lot of effort in the discovery and use of renewable energy sources as well as in the increase of the efficiency in the processing of use these energy sources. In this aspect, the electric power generation based on solar photovoltaic and wind turbines technologies has been effective in distributed generation systems and also in standalone systems for supplying isolated communities [3,4]. In standalone systems, those solutions have been shown appropriate for areas of difficult access, dispersed, with environmental restrictions or with a population formed by low-income people, even when these adverse characteristics represent a difficulty for the sustainability of the designed generation system. Technical and operational troubles, and supply interruptions are difficult to be solved due to the non availability of technical assistance. The delay of remote assistance leads to long periods of lack of electrical service, causing loss of credibility in this kind of system [5,6]. Thus, to overcome these difficulties, isolated systems must be projected taking into account reliability, minimizing the dependence of maintenance and human intervention, mainly because it is expensive and quite often not available.
 LINK
https://sigaa.ufma.br/sigaa/verProducao?idProducao=145039&key=b1ef3085988018312827ca9d7bd09bba

Case study Large Hadron Collider CERN : Borri protects the particle accelerator

CASE STUDY UPS BORRY ITALY

CERN
Large Hadron Collider (LHC), the largest and most complex
scientific instrument ever built and the highest energy particle
accelerator in the world is protected by Borri solutions.
“Made in Italy protagonist at CERN: after the success of Italian
researchers in the discovery of the Higgs Boson the world’s largest
centres for scientific research chooses the Italian UPS Borri”

Borri Spa has provided both AC and DC. After a joint analysis with experts, CERN, has opted for a distributed power protection system, with equipment of various sizes that feed, in a redundant configuration, security systems and controlled shutdown of the accelerator. All UPS units are characterized by Borri technology sinusoidal absorption input (unity power factor and harmonic current distortion less than 3%) and they are derived from B8000FXS, B9000FXS and B9600FXS series with customisations that involved special painting and the system EPO (UPS emergency Power Off ). A specific redundancy configuration is also included, with three UPS in cascade, resulting in a system tolerant to the second failure.

The protection of the auxiliary 48 Vdc systems has been developed according to the requirements of CERN, from an Oil & Gas based rectifier, RTB.e series 100 A, with a custom redundancy system, providing a dual path for both the power supply of the loads, and the charging of the backup batteries. Even the battery cabinets have been develo- ped ad hoc, to meet the higher safety and maintainability requirements of the installation. Borri UPS also protect: Atlas project data center, with a system of three B9600FXS 500 kVA UPS in parallel with a 2000 A centralised static bypass switch and 4 minutes autonomy; LHC data center, with two B9600FXS 400 kVA UPS in parallel (dual feed redundant configuration) and 10 minutes autonomy Batteries are VRLA type (sealed lead acid) in all AC UPS systems and Ni-Cd type for DC UPS systems.

FULL PAPER
http://www.borri.it/public/docs/CS_EN_CERN-Borri-14.pdf

A Study on the Multi-level PV-PCS Using Cascade 3-Phase Transformer Kim, Ki-Seon ; Song, Sung-Geun ; Cho, Su-Eog ; Choi, Joon-Ho ; Kim, Kwang-Heon ; Park, Sung-Jun ;

A Study on the Multi-level PV-PCS Using Cascade 3-Phase Transformer
Kim, Ki-Seon ; Song, Sung-Geun ; Cho, Su-Eog ; Choi, Joon-Ho ; Kim, Kwang-Heon ; Park, Sung-Jun ;


Abstract
The study on the multi-level inverter has been increasingly progressing to reduce the switching loss and improve the THD of output current in photovoltaic inverter. Recently, the main topics of multi-level inverter are to reduce the number of devices maintaining the power quality. Therefore, the novel topology was proposed for these problem which is composed of the isolated H-bridge multi-level inverter using the three phase low frequency transformer. The proposed multi-level inverter may not be need for a independent DC power, diode and capacitor. Specially, It has a advantage in generating high voltage source. The proposed approach is verified through simulation and experiment.

LINK1
http://www.koreascience.or.kr/article/ArticleFullRecord.jsp?cn=DHJGII_2009_v58n12_2359

High power grid-connected PV PCS with power quality improvement and stand-alone operation KIM,JAE HYUNG GRADUATE SCHOOL SUNGKYUNKWAN UNIVERSITY PHOTOVOLTAIC SYSTEM ENGINEERING

High power grid-connected PV PCS with power quality improvement and stand-alone operation
KIM,JAE HYUNG
GRADUATE SCHOOL SUNGKYUNKWAN UNIVERSITY PHOTOVOLTAIC SYSTEM ENGINEERING

ABSTRACT

With the increase of power consumption, the limitation of fossil fuel and global warming, as power generation systems become superannuated, every country has faced several sorts of energy problems. Moreover, since power consumption has increased, not only reserve margin is decreased but also more power plants are required. However, the construction of power plants is restricted since those power facilities are closely related with environmental problems. Consequently, since the use of sensitive loads such as the latest IT products is increased, power quality issue is being magnified as a new controversy. In this research, the power quality improvement function applied to three-phase four-wire H-bridge type photovoltaic power generation system is proposed. When the photovoltaic power generation system is operated in grid-connected mode, grid current distorted by unbalanced load is improved, and the system is operated in stand-alone mode during power failure. Moreover, when the amount of solar radiation is low such as night time, the system is operated as a active power filter and improve the performance of the photovoltaic power generation system. The series dual loop with quasi-resonant proportional controller and 2ndorder deadbeat controller is applied to the system as a controller. Single phase PLL with phase synchronizing function, Goertzel stand-alone detection function with minimized non-detection area and Goertzel power quality control function are proposed. In order to verify the validity of the system performance, simulation and experiment with 100kw H-bridge type three-phase inverter are progressed.

A Study on Improving Efficiency of High-frequency Switching Hybrid Inverter Circuit in Grid-connected Photovoltaic Power Generation Heo, Chan-Yoo Department of Electrical Engineering Graduate School Soongsil University

ABSTRACT
A Study on Improving Efficiency of High-frequency Switching Hybrid Inverter Circuit in Grid-connected Photovoltaic Power Generation Heo, Chan-Yoo Department of Electrical Engineering Graduate School Soongsil University
Supervised by Professor Jeon, Hee-Jong
 The various problems of Energy pluralism by new and renewable energy technique development is in progress mainly from advanced countries due to recent global warming by environmental change and fossil energy resources depletion. And major area of fuel cell, photovoltaic and wind power generation are actively in progress from many types of new and renewable energy. Photovoltaic power system stores the direct current resource generated from photovoltaic module into battery, and converts this into alternating current to use. Photovoltaic power generation uses solar for its energy resource, which does not need fuel, and the equipment has long life since it has no moving parts or heat engine. Also, it is more convenient in operation and maintenance than other existing power generation methods. But, it has higher unit cost than existing power generating methods, and need wide area to install solar cell module to use certain amount of electric power since its energy density is scarce. In addition, it has weak point of close influence by environmental condition such as weather condition. All sections of the photovoltaic power system from raw material to the grid connection are important, but the photovoltaic power inverter, which relates the stable power to the grid or can supply powerto individual load, can be regarded as one of the most important section. The generated power is of no use if the inverter does not make regular output even though a lot of power is generated from the photovoltaic array. The criteria for evaluating the photovoltaic inverter's performance is the power conversion efficiency of the inverter. For domestic photovoltaic power system, the booster converter's efficiency is around 99[%], the inverter efficiency is around 94[%], and studies are in progress to improve inverter efficiency. The Grid connected inverters in photovoltaic PCS(Power Conditioning System) have different efficiency according to their switching methods. 3 Level PWM switching type circuit has half the frequency than the circuit composed of 2 Level PWM, and has improved efficiency because of less switching loss. In general, photovoltaic PCS mainly use IGBT components. But the hybrid circuit composed of MOSFET and IGBT components is considered to improve efficiency even more by improving reverse recovery time and loss by IGBT's tailing current. In this paper, it is intended to prove that the high-frequency switching inverter circuit with MOSFET has improved efficiency than 3 Level circuit with all IGBT components through simulation and 3[kW] PCS hardware.