Voltage balancers have been extensively employed in hybrid microgrids in order to maintain the feeder DC voltage. The closed-loop control system needs the voltage across the output capacitor and the current through the output inductor to be measured. In this paper, a current sensorless control scheme is proposed for controlling the voltage balancer. First, the state-space equations of the system are derived. Then, using the derived equations, the state variables of the system are estimated using an observer. The proposed observer eliminates the need for the current sensor required in the closed-loop control system. Simulation results and experimental results verify the feasibility of the proposed sensorless control technique.
This paper propose bi-directional multiport converter as one of the DC power supply system suitable for renewable energy. The seamless power transmission within a certain voltage range can be realized by using bi-directional multiport converter. Moreover, a circuit configuration and control method of bi-directional multiport converter are included. The effectiveness of the proposed converter and control method has been investigated analytically by simulation and experiment on power transmission.
Solar power plants have methods of diagnosing the failure of their solar panels. In this paper, we propose a remote automatic diagnose failure method that uses PV string data. Some string measurement devices are used for continuous remote monitoring of solar power panels. Solar panels generate low power due to panels breaking, shadows from structures, weeds, etc. If these failures can be classified by fault classification using remote string measurement data, a reduction in unnecessary repair actions and more efficient preparations are possible. We use machine learning to automatically classify causes of decreased solar power generation, such as broken panels, shadows, or weeds. We applied this diagnosis method to some large solar plants. The results of our experiment proved that the learning accuracy of this proposed method is 100%. When we tested this classification method in another solar plant, the classification accuracy was 99%. This result suggests that this diagnosis method is useful and can decrease maintenance work.
This paper discusses the effects of hurricanes Harvey, Irma and Maria, that affected the U.S. and the earthquake that affected central Mexico in 2017 on information and communication networks (ICNs) infrastructure. The discussion is based on data and information collected at the time of these natural disasters and on field damage assessments conducted in the affected areas. Hence, the description of the effects of these events is presented through extended photographic evidence collected during these damage assessments.
A kind of intelligent power online monitoring system is designed for the requirements of power quality monitoring and power conversion measurement in the new green power generation system named FGC Wind Photovoltaics Storage integrated power station. The core hardware adopted the embedded modular structure design, the embedded software adopted three layer architectures, and many kinds of communication mode and B/S architecture of remote monitoring. The function of different electric power energy conversion measurement is achieved by combining the Online power monitoring of the FGC power station each power line with the harmonic analysis of power quality. The system structure is reasonable, easy to install, and convenient to manage.The system meets the requirements of the integrated power station quality monitoring, and has realized the electrical energy conversion measurement and the evaluation of green energy saving.
Metal oxide varistors (MOVs) are commonly mounted as a lightning protection measure (LPM) in power systems such as the 48 V DC system in telecom facilities. However, degradation in the performance of the MOVs causes electric leakage of 50 Hz commercial AC power. In order to prevent such electric leakage, it is recommended that a fuse be connected in series with the MOVs for short-circuit protection. However, because the fuse is connected in series with the MOVs and a lightning surge will flow through it, such fuses must not be blown out by the lightning surge. Therefore, the authors propose a fuse with a dual structure: an outer conductor through which the lightning surge current and some of the overcurrent from commercial power will flow, and an inner conductor through which the overcurrent from commercial power and some of the lightning surge current will flow. In this study, authors evaluated whether the proposed fuse can control the current flow or not. First, by measuring the lightning surge currents that flowed through a prototype, which was installed on small coils, it was found that the proposed fuse can control the lightning surge current flow, which favors higher frequency current flow through the outer conductor. Second, by simulating the current separation rate (CSR), which is the ratio of current flow through the outer and inner conductor, it was found that the efficiency of current separation can be improved by changing the thickness and diameter of the outer conductor.
This paper presents a method for d-q frame impedance measurement and the small signal stability analysis of 3-ϕ power electronic converter based system with constant power loads (CPLs). The method is based on the Newman’s multi-tone low crest technique in which the perturbed frequencies are added at the optimal phase angle. The resultant perturbation signal has the lowest crest factor compared to the conventional multi-tone sinusoidal signal. The optimal perturbation signal is suitable for impedance measurement of strong/weak grids. In this work, a multi-tone current signal is generated based on the Newman’s optimal phase angle method to measure d-q frame impedances and subsequently the system stability is analyzed using general nyquist stability criteria based on the source and load impedances. Once the stability is analysed, an active control method is applied to improve the stability margin of the system based on the grid impedance conditions by reshaping the impedance profile of the load subsystem contains the CPL. The effectiveness of active control method has been tested in MATLAB/Simulink simulation environment for a three-phase motor drive system feeding through an active front end (AFE) rectifier, which behaves as the CPL.
with power densities increasing in both Cloud and other HPC data centers there is a need to maximize the efficiency of the cooling systems for two purposes. The first is to provide the additional cooling capacity required in these facilities. The second is to minimize the power consumption of both the electrical delivery system and the cooling system. The cost of power is another driving force in this effort. One major factor of controlling the efficiency of the cooling system is to eliminate Bypass Airflow and Recirculation. A major contributor to eliminating Recirculation is to isolate the hot and cold airflows within the computer room. This is done with aisle containment, creating a physical barrier between the two airflows. These barriers eliminate recirculation of hot air into the Cold Aisle. With this accomplished the cooling task is reduced to providing the servers with just the correct amount of cold air to dissipate the heat generated by the computer equipment. Controlling this task will be touched upon in this paper. The primary purpose of the paper is to examine which configuration to employ, Hot or Cold Aisle containment, in the data centers where In-Room Cooling Units are used. There is no RIGHT answer. The decision depends on the size of the facility, the amount of equipment in the facility that requires high density cooling, the cooling system available or planned to be installed. Is it an economizer cooling system or a traditional central refrigeration cooling system? In addition, the localized cooling systems, e.g. In-Row Cooling units or Rear Door Heat Exchangers are also introduced in the end of the paper. The plusses and minuses will be explored.
The data center will consume huge power in proportion to an amount of data. Thus, the energy saving and management are necessary by high performance power supply system. Although the digital control switching power supply is recognized as the important factor for such a system, the control accuracy, which is one of the important issue of digital control, should be improved for practical application. The purpose of this paper is to improve the control accuracy of digital peak current mode control dc-dc converter. The programmable delay line is additionally implemented and can optimize on-time. The operation principle of proposed method is expressed. The proposed method is validated by simulation and experiment.
A high-efficiency buck-boost converter is developed using a GaN semiconductor field-effect transistor (FET).Conventional boost-type distributed MPPT converters perform only the boost operation, requiring the load-side voltage to be higher than the photovoltaic (PV) voltage. Thus, when the load-side voltage is low, MPPT control cannot be performed, yielding a sub-optimal output. A buck-boost converter was therefore fabricated, with the efficiency reduction arising from the added circuit complexity remedied using a GaN FET. MPPT control could therefore be performed even in the step-down regime, in contrast with a conventional step-up-only converter. The use of a GaN FET to improve efficiency demonstrably therefore addresses the shortcomings of buck-boost converters.
This paper presents an energy management method for single-phase telecommunication backup systems operating in islanded mode. The management of energy has been performed through controlling the power electronic interfaces that connect the backup systems to the telecommunication facilities and the utility grid. The proposed control scheme regulates the backup network parameters, such as the voltage and frequency of the supplied power, and the DC-bus voltage simultaneously. Using the proposed control scheme the reliable and efficient operation of the backup system during power outages and islanded mode, can be guaranteed. The simulation and experimental results approve the superior performance of the proposed controller in comparison with the conventional droop-based controller proposed for backup systems in islanded mode.
This article analysis the bidirectional operation of the so called Isolated Efficient Wide Range Converter (I-EWiRaC), equipped with synchronous rectification, including small signal modelling and controller design. The converter is used in fuel-cell-based back-up systems, with ultra capacitors (UC) as intermediated energy storage between the fuel cell and the power converter. Earlier, an additional converter was used to charge the UC to the required DC voltage. The presented idea can improving the system efficiency and reliability and reduce overall system costs.
The new design of passive cooling device for box TV is investigated. Experimental measurements of different architecture of miniature heat pipes including flat porous heat pipe, cylindrical micro-grooved and porous heat pipes are presented. The heat pipes temperatures distributions are measured for different working fluid filling ratios. Once the optimal volume is obtained and fixed, tests are carried out to evaluate the thermal performance of the heat pipes by measuring evaporator, adiabatic and condenser temperatures within various heat fluxes. Results, after being analyzed, discussed and compared, show that the flat porous heat pipe is the most effective for heat dissipation. This heat pipe is integrated in a box TV instead of conventional forced air cooling device. The flat heat pipe cooling performance is explored using deionized water. Results show that the heat pipe passive cooling device well cooled the box TV electronic components compared to fans cooling mode and the CPU operating temperature remains lower than its limit value.
Based on the detailed analysis of the star-connected three-phase interleaved LLC resonant converter topology, this paper proposes a new control strategy of three-phase interleaved LLC resonant converter PFM mode combined with single-phase full-bridge LLC resonant converter PFM mode and phase-shift mode, which can greatly reduce the hard-switching work range of the three-phase interleaved LLC resonant in low output voltage and light output load case and is suitable for the high power conversion applications of wide range output. A three-phase interleaved LLC resonant converter based on the new control strategy is proposed for detailed analysis to verify the new control strategy's correctness and feasibility.
For the common-mode (CM) noise reduction, many literatures have been reported on CM noise reduction using filters, passive or active, and impedance balancing which in both cases, extra devices needed to be added to the circuit that may increase not only the size of the system but also its cost. However, for different pulse width modulation (PWM) techniques, very few studies are available with the perspective of the conducted CM noise as well as common-mode voltage (CMV) reduction in spite of their cost-effective and flexible control advantages. This paper investigates the effect of different Bus-clamping PWM (BCPWM) techniques on the CMV, CM leakage current as well as electromagnetic interference (EMI) noise behavior due to fast switching power devices used in power electronic converters. Conventional space vector PWM (CSVPWM) as well as BCPWM principles are reviewed and their switching sequences are summarized. Timedomain simulations followed by frequency-domain analysis using Fast-Fourier Transform (FFT) algorithm have been carried out and results are presented. It was determined that, the CMV and its subsequent CM noise can be reduced using BCPWM techniques.
In order to reach the climate and energy targets, every country and territory should promote a sustainable energy plan. The Italian National Energy Strategy 2017, in accordance with the long-term scenario of EU Energy Roadmap 2050, defined the actions to reduce GHG emissions and, in this context, the energy communities can play a strategic role. The Council of European Energy Regulators defines "local energy community" a cooperative / partnership / non-profit organization of final customers, which can involve different stakeholders, such as municipalities, local societies, public and private companies. The stakeholders work together in energy communities for: the production and distribution of energy generated from renewable sources, the optimization of energy demand and supply and the reduction of energy consumptions, GHG emissions and costs. The communities' objectives are to boost energy exchanges, to encourage the establishment of inter-company smart grids and to increase energy efficiency in participating companies. A choice for energy independence that guarantees the energy security with a low environment impact and affordable energy costs. Where energy communities are consolidated, there is a 20-30% savings on energy prices, and a self-production level of around 80% on energy needs.The challenge of this work is to present a future local energy community in Italy: a case study in the Pinerolo area of the Piedmont Region. In particular, this work presents a procedure useful to monitor and manage the energy consumption and production of different stakeholders in a territory. The energy data were collected using an online questionnaire sent to municipalities and companies. The first test of the procedure in the Pinerolo area highlighted the problems related to the various stakeholders in the energy community with different formats and quantities of data, and more or less complicated energy management systems that imply a diversified availability of data and response times.
A new isolated interleaved boost DC-DC current-fed converter is proposed in the paper. The proposed converter is implemented with three main active switches, a transformer, and an auxiliary flyback converter that has a snubber capacitor that can be discharged through the output. In this paper, the general operation of the converter is discussed, its general operating principles and modes of operation are explained in detail and its features and design are discussed. Experimental results obtained from a converter prototype are presented to confirm the converter's feasibility.
This paper is designed for the site of hybrid energy power system of solar and diesel generator. Referring to the site survey information, we propose an optimized configuration method which includes solar photovoltaic panel capacity, battery capacity and diesel generator capacity for the hybrid power system. The optimized configuration method reduce the initial investment of the investors. After analysis of historical data of a large number of hybrid sites, we also propose an intelligent control strategy to achieve the goal of zero discarding solar energy to maximize the use of solar energy, and reduce the running time of diesel generator. And then the maintenance costs of the operator are reduced.
The significant increase of unpredictable and fluctuating injections of energy into the grid by plants fed with Non-Programmable Renewable Energy Sources (NP-RES), and also connected at the distribution level, has triggered critical power system operation issues, which impact, e.g., on procurement and usage of resources for Ancillary Services (AS). In order to involve new resources, changes are needed both in terms of AS specifications and in the regulatory framework, and thus in the Ancillary Service Market (ASM) rules. In Italy, e.g., pilot projects have been started to allow medium-small generation units (including NP-RES ones), load units and Battery Energy Storage Systems (BESS), also in an aggregated form, to participate in the ASM to supply balancing resources (e.g. replacement reserve). In this work, a preliminary techno-economic analysis is carried out about how aggregated load units, in particular Base Transceiver Stations (BTS) for mobile communications, could supply Demand Response Services (DRS) as upward balancing services via participation in the Italian ASM. BTS flexibility could be further enhanced thanks to the presence of local backup sources, such as BESS or diesel generators. The BTS are assumed here to be available to curtail absorption from the main grid for a set availability time range (some hours); during interruptions, their energy supply is replaced by their backup sources. Economic evaluations are carried out by considering fixed-price offers for the curtailed energy, and CAPEX and OPEX for BTS control and communication systems enabling service supply. Results show good profitability if the pay-as-bid remuneration for the curtailed energy is complemented by a capacity remuneration.
Photovoltaic (PV) systems which are subjected to partial or full shading have reduced output power compared to the actual power rating of unshaded systems. Full shading can occur as a result of reduction in irradiance due to cloud cover while partial shading occurs due to nearby objects such as telecommunication antennas. This paper presents a comparative analysis on the performance characteristics of two different PV technologies in shaded environments.
