Current Issue : January - March Volume : 2017 Issue Number : 1 Articles : 5 Articles
The increasing penetration of renewable generators can be a significant challenge due to\nthe fluctuation of their power generation. Energy storage (ES) units are one solution to improve\npower supply quality and guarantee system stability. In this paper, a hybrid microgrid is built\nbased on photovoltaic (PV) generator and ES; and coordinated control is proposed and developed to\nachieve power management in a decentralized manner. This control scheme contains three different\ndroop strategies according to characteristics of PV and ES. First, the modified droop control is\nproposed for PV, which can take full utilization of renewable energy and avoid regulating output\nactive power frequently. Second, to maintain the direct current (DC) bus voltage stability, a novel\ndroop control incorporating a constant power band is presented for DC-side ES. Third, a cascade\ndroop control is designed for alternating current (AC)-side ES. Thus, the ES lifetime is prolonged.\nMoreover, interlinking converters (ICs) provide a bridge between AC/DC buses in a hybrid microgrid.\nThe power control of IC is enabled when the AC- or DC-side suffer from active power demand\nshortage. In particular, if the AC microgrid does not satisfy the reactive power demand, IC then acts\nas a static synchronous compensator (STATCOM). The effectiveness of the proposed strategies is\nverified by simulations....
The importance of energy-constrained processors continues to grow especially for\nultra-portable sensor-based platforms for the Internet-of-Things (IoT). Processors for these IoT\napplications primarily operate at near-threshold (NT) voltages and have multiple power modes.\nAchieving high conversion efficiency within the DCââ?¬â??DC converter that supplies these processors is\ncritical since energy consumption of the DCââ?¬â??DC/processor system is proportional to the DCââ?¬â??DC\nconverter efficiency. The DCââ?¬â??DC converter must maintain high efficiency over a large load range\ngenerated from the multiple power modes of the processor. This paper presents a fully integrated\nstep-down self-oscillating switched-capacitor DCââ?¬â??DC converter that is capable of meeting these\nchallenges. The area of the converter is 0.0104 mm2 and is designed in 28 nm ultra-thin body\nand buried oxide fully-depleted SOI (UTBB FD-SOI). Back-gate biasing within FD-SOI is utilized\nto increase the load power range of the converter. With an input of 1 V and output of 460 mV,\nmeasurements of the converter show a minimum efficiency of 75% for 79 nW to 200 Ã?¼W loads.\nMeasurements with an off-chip NT processor load show efficiency up to 86%. The converterââ?¬â?¢s large\nload power range and high efficiency make it an excellent fit for energy-constrained processors...
Recently, high power-density, high power-efficiency, and wide regulation range isolated DC-DC converters have been required.\nThis paper presents considerations of physical design and implementation for wide regulation range MHz-level LLC resonant DCDC\nconverters. The circuit parameters are designed with 3ââ?¬â??5MHz-level switching frequency. Also, the physical parameters and\nthe size of the planar transformer are optimized by using derived equations and finite element method (FEM) with Maxwell 3D.\nSome experiments are done with prototype LLC resonantDC-DC converter using gallium nitride high electron mobility transistors\n(GaN-HEMTs); the input voltage is 42ââ?¬â??53V, the reference output voltage is 12V, the load current is 8 A, the maximum switching\nfrequency is about 5MHz, the total volume of the circuit is 4.1 cm3, and the power density of the prototype converter is 24.4 W/cc....
The three-port converter has three H-bridge ports that can interface with three different\nenergy sources and offers the advantages of flexible power transmission, galvanic isolation ability and\nhigh power density. The three-port full-bridge converter can be used in electric vehicles as a combined\ncharger that consists of a battery charger and a DC-DC converter. Power transfer occurs between\ntwo ports while the third port is isolated, i.e., the average power is zero. The purpose of this paper\nis to apply an optimal phase shift strategy in isolation control and provide a detailed comparison\nbetween traditional phase shift control and optimal phase shift control under the proposed isolation\ncontrol scheme, including comparison of the zero-voltage-switching range and the root mean square\ncurrent for the two methods. Based on this analysis, the optimal parameters are selected. The results\nof simulations and experiments are given to verify the advantages of dual-phase-shift control in\nisolation control....
The aim of this study is to investigate the improvement of the performances and transient stability of grid\nconnected Squirrel Cage Induction Generator based on Wind Farm (SCIG-WF) by using a new coordinated control\nbetween Grid Side Converter (GSC) of the Doubly Fed Induction Generator (DFIG) and photovoltaic solar plant\nconverter (PV-SPC) as STATCOM. Thereby, the reactive power required by the SCIG-WF can be supplied either\nby the DFIGs (during normal condition) and with the PV-STATCOM during grid disturbances. This control strategy\ncan fulfill the grid codes requirement such low voltage ride through capability by ensuring a no uninterrupted\noperation of the wind farm. The proposed control scheme is simulated by means of MATLAB/Simulink platform,\nbased on a detailed system model. Through the simulated results, we can conclude that the proposed control for PVSPC\nto operate as STATCOM is validated and the performances of the system are improved during normal and\ntransient conditions....
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