Bidirectional Energy Flow Research Articles

Common-Mode Conducted EMI Prediction for Dual Active Bridge Converter Based on Unterminated Behavioral Model

A dual active bridge (DAB) converter is widely used in electric vehicles due to its advantages of electrical isolation function and bidirectional energy flow. However, compared with other converters, the number of switching tubes is large; the internal structure is complex, and the electromagnetic interference (EMI) at the input and output ends is more serious. In this article, a predictive behavioral model is established to predict the common-mode (CM) conducted EMI on both sides of the DAB converter. First, the converter is treated as a linear two-port network. Second, the impedance of the two-port network in the CM loop is calculated from the extracted S-parameters of the converter. Then, an equivalent model is established to predict the conducted EMI combined with the CM current of the input and output buses. Finally, the proposed model is verified by experiments on a 140-W DAB converter system.

Research on Bidirectional Isolated Charging System Based on Resonant Converter

This paper proposes a two-stage bidirectional isolated charging system, which can realize the bidirectional flow of electric energy, not only making the electric energy flow from the grid side to the battery side but also converting the battery’s energy into single-phase alternating current to supply other electric equipment. The charging system also has the function of power factor correction and wide-range voltage output. The front stage of the charging system is a bidirectional totem pole structure power factor correction converter with a voltage and current double closed-loop control strategy to ensure the stability of the DC bus voltage, and the rear stage is a bidirectional CLLLC resonant converter, which adopts a high-frequency soft start strategy to reduce the inrush current during start-up and ensure the safe operation of the converter. Moreover, the frequency control strategy is used to make it have a wide range of DC output characteristics. In this paper, the principle analysis and parameter calculation of the charging system is carried out, the simulation platform and hardware circuit design are built, and a test prototype is piloted to verify the bidirectional operating characteristics of the charging system. The simulation and experimental results demonstrate the correctness of the theoretical analysis and topology design.

Electric Vehicles and Vehicle–Grid Interaction in the Turkish Electricity System

Electric vehicles and energy storage systems are technologies in the stage of intensive development. One of the innovative ways to use electric cars is the Vehicle to Grid (V2G) concept. V2G charging points are characterized by the ability of bidirectional energy flow while charging EV/BEV (Electric Vehicles/Battery Electric Vehicles). In periods of low energy consumption and the presence of the highest shares of renewable sources, the cleanest electricity is drawn from the grid at the lowest prices and stored in a “mobile warehouse”, which is an electric car. During the reported peaks in electricity demand and the presence of high tariffs, the previously stored energy may be sold back to the distribution network operator. Thanks to this application, the technology determines the highest profitability of the system and assigns EV/BEV the ability to manage electricity flows, while improving the energy balance of the economy. The prospects for the spread of V2G have increased along with the growing requirements for domestic economies, closely related to the significant share of renewable energy sources. The vision of connecting EV/BEV with the power grid creates completely new ways of managing energy and makes it possible to build smart agglomerations in line with the Smartcity idea. Especially since Turkey is one of the countries promoting this idea. The scientific aim of the study is to maximize the aggregator’s profits for V2G by creating a coalition with renewable energy producers and combining the capacities of many EVs and offering their total capacities to the electricity markets. The subject of the research was to obtain extensive knowledge about the vehicle–grid interactions taking place in the Turkish power system. For this purpose, an analysis is conducted to determine the optimal preferred operating points and the amount of regulation proposals that maximize the profit of the EV users while satisfying the constraints of each stochastic parameter. The results show the system benefits from the implementation of the algorithms are significant to optimal bidirectional V2G impacts on distribution systems with high penetration of EVs. The research can find practical applications in assessing the role of electric vehicles and their integration in the vehicle–grid system in power systems. At the same time, pointing to the benefits related to the implementation of such solutions for Turkey and other countries in the field of electromobility, stability of energy systems, and energy independence through the possibility of achieving the desired synergy effect.

Transformerless High-Gain Three-Port Converter With Low Voltage Stress and Reduced Switches for Standalone PV Systems

This article proposes a high-gain transformerless three-port converter (TPC) for standalone photovoltaic (PV) systems. The TPC is designed and developed based on a dual-inductor high-gain two-port converter by utilizing one of the buffer capacitors to derive the third part for PV input. A hybrid pulse-frequency modulation scheme unified with a pulsewidth modulation control strategy is adopted, which realizes the maximum power point tracking control, load voltage regulation, and bidirectional energy flow at the battery port. The proposed TPC offers the unique advantages of high voltage gain, continuous battery port current, reduced power semiconductors, lower voltage stresses, common ground shared by all the ports, low-cost gate driver, and small size of the rear-end inductor. The working principle, steady-state characteristics, small-signal models, and the control method, including design conditions, are comprehensively analyzed. The correctness of the theoretical analysis is verified by developing a 300-W experimental prototype, which shows that the maximum efficiency is 97.7%.

Efficient and Fast Active Equalization Method for Retired Battery Pack Using Wide Voltage Range Bidirectional Converter and DBSCAN Clustering Algorithm

This article presents an efficient and fast echelon battery equalization method based on wide voltage range bidirectional converter combined with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DBSCAN (density-based spatial clustering of applications with noise)</i> clustering control strategy. Thanks to the wide voltage range and bidirectional buck-boost characteristics of the four-switch bidirectional converter, the battery energy can be reasonably redistributed between the battery and the super capacitor. The converter operating in synchronous rectification mode can not only achieve bidirectional energy flow in a wide voltage range, but also has a high energy conversion efficiency. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DBSCAN</i> clustering algorithm is used to divide all battery cells into groups, and each group may contain one or more adjacent and nonadjacent battery cells. First, the nonadjacent single cells are balanced and integrated into adjacent group with the closest voltage. Then, the groups with different voltages are balanced by group-to-group, thereby realizing rapid balance of the entire battery pack. In order to verify the effectiveness of the proposed method, simulations and experimental verification were carried out. The experimental results show that, comparing with traditional battery balancing methods, the proposed method achieves shorter balancing time and higher balancing efficiency.

A simulation model for the design and analysis of district systems with simultaneous heating and cooling demands

Latest generations of district heating and cooling systems are characterised by low network temperature with uninsulated pipes, decentralised heat pumps and chillers to modulate the network temperature, and shared energy flows between interconnected buildings. This paper presents a simulation model for the design and analysis of these systems. The model was developed using the Modelica language and it consists of component models from thermal, fluid, and control domains. The model was employed to simulate and analyse the first existing Swedish district system with simultaneous heating and cooling demands and bidirectional energy flows. The system currently connects nine buildings with total respective annual heating and cooling demands of 4.2 and 1.2 GWh. Simulation results revealed several benefits for integrating district and heat pump technologies, including (1) sharing energy flows between interconnected buildings to cover 40 % of the total carried heat in the network, (2) reducing the total purchased energy by 69 % compared to a traditional four-pipe district system, and (3) reducing distribution losses by 28 % compared to traditional networks with insulated pipes. The model can be utilised to support future research and development of new advanced district heating and cooling systems.

A synchronous rectification control method of bidirectional full-bridge LLC resonant converter with SIC MOSFETs

Bidirectional LLC resonant converters have the advantages of ZVS and ZCS characteristics, high switching frequency, high transmission efficiency, wide voltage gain range, bidirectional power flow characteristics and etc which are widely used in intelligent micro-grid, new energy power generation, electric vehicles, uninterruptible power supply system(UPS) and other fields. Meanwhile, with the development of silicon carbide(SiC) as the third-generation semiconductor material, the power density and efficiency of LLC resonant converters have been greatly improved. This paper proposes a new synchronous rectification control method suitable for the SiC bidirectional full-bridge LLC resonant converters. Whether the SiC LLC converter works in the boost or buck mode, all of SiC MOSFETs can realize ZVS and ZCS through the zero-crossing detection module.The strategy proposed in this paper can effectively reduce the effect of circulating power of SiC converter, improve the output voltage gain of the converter, and further realize the bidirectional flow of energy. This paper analyses the principle of the control strategy in detail, establishes the equivalent model of the fundamental wave, analyses its voltage gain characteristics and soft switching characteristics, and completes the derivation of the corresponding formulas. Finally, the proposed control strategy is verified by PSIM simulation.

LOSISH—LOad Scheduling In Smart Homes based on demand response: Application to smart grids

The evolution towards Smart Grids (SGs) represents an important opportunity for modernization of the energy industry. It is characterized by a bidirectional flow of information and energy between consumers and suppliers. However, the rapid increase of energy demands in residential areas is becoming a challenging problem. In order to address this issue, Demand-Side Management (DSM) has proven to be an effective solution. In this paper, we propose LOSISH, a price-based Demand Response (DR) system for load scheduling in residential Smart Homes (SHs) that achieves a trade-off between electricity payments and consumer’s discomfort. Our proposed system considers Renewable Energy Sources (RESs), Battery Energy Storage System (BESS) and Plug-in Electric Vehicle (PEV). We formulate our scheduling as a constrained optimization problem and we propose a new hybrid algorithm to solve it. The latter combines two well known heuristic algorithms: Particle Swarm Optimization (PSO) and Binary Particle Swarm Optimization (BPSO). Moreover, we propose a new clustering algorithm based on Machine Learning (ML) to extract consumer’s preferences from a real dataset that contains the historical consumption patterns of his smart appliances. We test our approach on real data traces obtained from a SH and we set up an experiment to evaluate our algorithm on a Raspberry Pi and measure its energy consumption. To prove the effectiveness of our approach, we compare our results with another approach from the literature in terms of electricity bill, Peak-to-Average Ratio (PAR), energy consumption, and execution time. Numerical results show that LOSISH outperforms the other approach in terms of electricity bill (up to 52.92% cheaper), PAR (up to 44% decrease in peak demands), energy consumption (up to 69.44% less consumption), and execution time (up to 63.15% faster).

A Publicly Available Multiobservatory Data Set of an Enhanced Network Patch from the Photosphere to the Corona

New instruments sensitive to chromospheric radiation at X-ray, UV, visible, IR, and submillimeter wavelengths have become available that significantly enhance our ability to understand the bidirectional flow of energy through the chromosphere. We describe the calibration, coalignment, initial results, and public release of a new data set combining a large number of these instruments to obtain multiwavelength photospheric, chromospheric, and coronal observations capable of improving our understanding of the connectivity between the photosphere and the corona via transient brightenings and wave signatures. The observations center on a bipolar region of enhanced-network magnetic flux near disk center on SOL2017-03-17T14:00–17:00. The comprehensive data set provides one of the most complete views to date of chromospheric activity related to small-scale brightenings in the corona and chromosphere. Our initial analysis shows a strong spatial correspondence between the areas of broadest width of the hydrogen-α spectral line and the hottest temperatures observed in Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 radio data, with a linear coefficient of 6.12 × 10−5Å/K. The correspondence persists for the duration of cotemporal observations (≈60 m). Numerous transient brightenings were observed in multiple data series. We highlight a single, well-observed transient brightening in a set of thin filamentary features with a duration of 20 minutes. The timing of the peak intensity transitions from the cooler (ALMA, 7000 K) to the hotter (XRT, 3 MK) data series.

Rüzgâr Türbin Sisteminde İki ve Üç Seviyeli Dönüştürücü Tasarımı ve Güç Analizinin Yapılması

Günümüzde artarak devam enerji ihtiyacı ülkeleri yenilenebilir enerji kaynaklarından üretilen enerjilere yönlendirmiştir. Bu çalışmada, büyük güç gereksinimi duyulan rüzgâr türbinlerine uygun, çift beslemeli asenkron generatör (ÇBAG) tabanlı rüzgâr türbin sistemi incelenmiş ve benzetimi yapılmıştır. Bu türbin sistemi 6 adet 1,5 MW toplam 9MW gücünde 25 kV’luk dağıtım sistemine entegre, 30 km’lik bir hat uzunluğuna sahip, 25 kV’luk transformatör ile 120 kV’luk şebekeye güç üretmektedir. ÇBAG tabanlı rüzgâr türbin sistemi çift yönlü enerji akışına uygun olmasından dolayı arka arkaya bağlı iki adet dönüştürücüden oluşmaktadır. Matlab/ Simulink programında üç fazlı iki seviyeli dönüştürücü ve üç fazlı üç seviyeli dönüştürücünün tasarımı yapılmış ve sinüzoidal darbe genişlik modülasyon tekniği ile anahtarlama sinyalleri üretilmiştir. Bu dönüştürücüleri tasarladığımız ÇBAG tabanlı rüzgâr türbini modellemesinde kullanarak ve 15 m/sn rüzgar hızında toplam güç, reaktif güç ve sistemin çıkış gerilimleri değerleri kıyas edilmiştir. Benzetimi yapılan sistem için üç seviyeli dönüştürücü ile daha kararlı ve stabil sonuçlar alınmıştır.

Charging potential of V4G through V2G standard protocol for CCS

The eVIP (Energy Visualisation Integration and Prediction) project aims to predict the load curve of electric vehicles in a semi-private context related to hotels and restaurants. Using the gradient boosted tree algorithm, it is possible to predict the consumption of a hotel with an accuracy of approximately 83.8% with nonintrusive devices. By using this prediction and the data collected when an electric vehicle is being charged at the hotel&apos;s charging station, the peak consumption of the hotel can be optimized. We have also opened the way for V4G (Vehicle for Grid) to allow bi-directional energy flows in this semi-private micro-grid and propose flexibility services to Distribution System Operators (DSO).

Grid-Forming Operation of Energy-Router Based on Model Predictive Control with Improved Dynamic Performance

The focus of this study is on the grid-forming operation of the Energy Router (ER) based on Model Predictive Control (MPC). ER is regarded as a key component of microgrids. It is a converter that interfaces the microgrid (s) with the utility grid. The ER has a multiport structure and bidirectional energy flow control. The ER concept can be implemented in Nearly Zero-Energy Buildings (NZEB) to provide flexible energy control. A concept is proposed where the ER works as a single grid-forming converter. The challenge is to keep the predefined reference voltage and frequency inside the NZEB in all possible modes, including the idle operation mode, current sources, and nonlinear load control. To gain stability and output voltage quality, the MPC is proposed. The design of the modified MPC algorithm with improved dynamics performance is explained. PLECS software is utilized to verify the proposed algorithm. The results demonstrate the suitable performance of the proposed control method in terms of total harmonic distortion of the output voltage. The influence of weighting coefficiencies is evaluated, showing the higher impact of the capacitor filter voltage on lowering the total harmonics distortion of the output voltage. Finally, the capability of the control system toward step change in the reference value is evaluated.

Bidirectional EV integration in home load energy management using swarm intelligence

A swarm-based meta-heuristic search approach has been adopted in this study for Home Load Energy Management set-up (HLEMs) to schedule smart appliances with minimum energy bills utilising the bidirectional energy flow of Electric Vehicles (EV). The Instant state of charge (IOC) level of EV is utilised to achieve the proper scheduling of home loads by considering the energy threshold with a cost-effective user opulence. The problem objective is formulated with a meta-heuristic population-based elephant herding optimisation technique to schedule the home loads along with the EV to incur a minimum bill of daily energy expenditure and also to enhance the utilisation of daily average power by minimising the peak to average ratio of a typical smart home. The analysis has been compared with the Grey Wolf Optimisation scheduling technique to prove the proficiency of the proposed method.

High Step-Up Resonant DC–DC Converter With Resonant Network for Electrical Collection Systems

Abstract The efficiency of renewable energy electrical collection can be effectively improved by adopting the high voltage direct current (HVDC) electrical collection method. The low-voltage DC power is stepped up to the high-voltage level for HVDC transmission by one-stage step-up type, which can reduce the cost of high-voltage large-capacity DC-DC converters. However, the high cost of DC-DC converters which can achieve high step-up ratio, such as modular multilevel converter (MMC), limits the development of the one-stage step-up type. In this paper, a low-cost DC-DC converter with high step-up ratio which can realize the bidirectional flow of energy is proposed. The total step-up ratio is the product of high-frequency transformer ratio, resonant network gain and step-up ratio of voltage doubler rectifier circuit. Meanwhile, the direct power factor control (DPFC) strategy is proposed based on the idea of controlling active power to achieve the goal of controlling output voltage. Finally, the step-up ratio of the DC-DC converter can reach 160 times, and realize zero-voltage switching (ZVS) turn-on of the switches and zero-current switching (ZCS) turn-off of the diodes.

Authenticated Key Agreement Protocol for Secure Communication Establishment in Vehicle-to-Grid Environment With FPGA Implementation

Vehicle-to-grid (V2G) technology enables bidirectional energy flow between the electric vehicle and power grid thereby making the electric vehicle as a virtual power plant. This seamless exchange of energy flow is possible only when the entities involved communicate wirelessly in a secured manner. In order to ensure privacy-preserving in the V2G communication, development of a novel key establishment protocol is an active area of research. This article presents a lightweight mutual authentication and key establishment protocol for secure V2G communication among the electric vehicle user, charging station, and utility service provider. The correctness of the proposed protocol is verified using the formal method BAN logic, and many of its security threats are analyzed informally. Further, the protocol is compared for its security and efficiency with the related protocols in the literature under various aspects, and the comparison results show that our protocol outshines the others. The functional correctness of the protocol is also verified in Xilinx Zynq-7000 series FPGA board so that it can be deployed in any real-time applications.

Emissions assessment of a tanker in a chilean port using bi-directional cold ironing integrated to LNG

Air pollution in coastal cities and nearby communities has become a health problem in the last decades because of the dispersion of pollutants produced by the various port activities. In this context, when a vessel at berth uses its auxiliary engines to generate the electric power to maintain its service, the operational profile is not continuous; the auxiliary engines work outside their fuel efficiency range, producing additional pollutant emissions.To reduce emissions while in port and at berth, two short-term options are considered: the first option is using alternative energy sources such as liquefied natural gas (LNG) instead of current fuels. The second option is using cold ironing technology, which enables to turn-off the vessels auxiliary engines, by feeding the services using shore power supply. In a classical cold ironing configuration, energy only flows from shore to on board.This work presents an emissions assessment of a tanker vessel at berth, applying a novel bi-directional energy flow strategy associated to a cold ironing system, integrating LNG, and compared to current fuels used, focused on the environmental impact on Quintero’s Bay. This bay is one of the most important port areas of the Chilean coast deemed to be affected by emissions generated by intense port activities. Taking current fuels such as heavy fuel oil (HFO) and marine diesel oil (MDO) and ship’s arrivals/departures from port as a reference case, the results presented in this work, show a significant reduction in emissions when applying the bi-directional energy flow strategy.

Operation Optimization of Integrated Energy System considering Power-to-Gas Technology and Carbon Trading

Application of power-to-gas (P2G) technology can implement bidirectional energy flow between power network and gas network, which contribute to improved energy coupling, better operational flexibility, and high economic efficiency in the integrated energy system (IES). This study proposes a detailed IES model based on the refined P2G model according to the characteristics of P2G equipment. An optimal efficiency matching coefficient is proposed to increase the rate of energy equipment utilization. To address the carbon allocation problem, the carbon trading mechanism is employed in an optimization model with the consideration of economic benefits and costs (i.e., sales benefits, operating cost, carbon trading cost, wind power, and photovoltaic curtailment punishments). Case studies verify the advantage of the proposed optimization model. Furthermore, the results show that the P2G with gas tank mode has an obvious advantage in a comprehensive operating capability of IES.

Current Source Mode Bidirectional DC/DC Converter With Multiple-Level Output Conversion Ratios Based on the Hybrid PWM Control of the Switched-Capacitor Structure

The current source (CS) mode bidirectional dc/dc converter (Bi-DCC) with multiple-level output current ratios is presented. Using the hybrid pulsewidth modulation (PWM) method to control the conversion selection mechanism realizes the multiple-level conversion options in both bidirectional energy flows. It is suitable for future all-electrical driving and braking systems in electric vehicles, supplying power to adjust the motor dynamics control during vehicle driving and collecting the energy generated during braking, especially on different road conditions. Moreover, the function that one single converter provides multiple-level conversion ratios, makes the design highly suitable for smart manufacturing as it can simplify the design by type and configuration variations. This design mainly focuses on dealing with applications directly powered by the CS, for example, the connection of photovoltaic (PV) units, CS mode motor controller, current-based power systems, and CS mode light-emitting diodes. A 300 W prototype with a conversion selection structure (CSS), which contains three switching orders and ten levels of current options, has been established. It validated multiple conversion ratio selections for step-down and step-up operation modes, high stability, and low power cost through the simulation and experiment results.

Smart Grid Security and Privacy: From Conventional to Machine Learning Issues (Threats and Countermeasures)

Smart Grid (SG) is the revolutionised power network characterised by a bidirectional flow of energy and information between customers and suppliers. The integration of power networks with information and communication technologies enables pervasive control, automation and connectivity from the energy generation power plants to the consumption level. However, the development of wireless communications, the increased level of autonomy, and the growing sofwarisation and virtualisation trends have expanded the attack susceptibility and threat surface of SGs. Besides, with the real-time information flow, and online energy consumption controlling systems, customers’ privacy and preserving their confidential data in SG is critical to be addressed. In order to prevent potential attacks and vulnerabilities in evolving power networks, the need for additional studying security and privacy mechanisms is reinforced. In addition, recently, there has been an ever-increasing use of machine intelligence and Machine Learning (ML) algorithms in different components of SG. ML models are currently the mainstream for attack detection and threat analysis. However, despite these algorithms’ high accuracy and reliability, ML systems are also vulnerable to a group of malicious activities called adversarial ML (AML) attacks. Throughout this paper, we survey and discuss new findings and developments in existing security issues and privacy breaches associated with the SG and the introduction of novel threats embedded within power systems due to the development of ML-based applications. Our survey builds multiple taxonomies and tables to express the relationships of various variables in the field. Our final section identifies the implications of emerging technologies, future communication systems, and advanced industries on the security and privacy issues of SG.

Load Frequency Control (LFC) of a Microgrid using PSCAD/EMTDC Simulation Program

Continuity of the power quality is important in the modern day grid structure and the smart grid structure of the future. Incorporating the renewable energy sources to the present grid system and the increase of the usage of technology devices will cause the power quality to decrease. Power system harmonics can be characterized as one of the factors that causes a decrease in the power quality. The effects of this factor, if not prevented, will lead to a decrease in the performance and reliability of power systems which will cause economic losses. In this study, a micro grid, which will play a very important role in our lives in the near future and can possibly be an example to the new grid infrastructure, has been designed. This micro grid mentioned above has been simulated with the PSCAD/EMTCD program. Micro grids need to use control methods to increase system reliability, to share power between distributed generation (DG) units and to keep frequency-voltage values at certain limits. Droop control method is preferred in this paper since it is one of the most widely used methods and its success in literature has been proven. The designed system has been tested with four different scenarios and the results have been discussed. Load frequency control (LFC), one of the reasons that effect the power quality, was particularly analysed. The additional costs and the advantages provided as a result of novel solution proposals in the case of electric vehicles (EV) being incorporated to the system were evaluated. Particularly, provision of bidirectional energy flow of the vehicle to grid (V2G) featured electrical vehicles to the grid was examined.