Bidirectional Energy Flow Research Articles

A Survey on Bidirectional DC/DC Power Converter Topologies for the Future Hybrid and All Electric Aircrafts

DC-DC isolated converters allowing a bidirectional flow of energy between High-Voltage DC and Low-Voltage DC networks have been proposed to be integrated in future on board power distribution systems. These converters must meet the specially stringent efficiency and power density requirements that are typical of the aeronautic industry. This makes it specially challenging to determine which converter topology is best suited for each particular application. This work presents a thorough review of several topologies of bidirectional DC-DC power converters that are considered good candidates to meet certain important aeronautic requirements, as those related with high efficiency and high power density. We perform simulations on virtual prototypes, constructed by using detailed component models, and optimized following design criteria that are in accordance with those typically imposed by aeronautic requirements. This comparative analysis is aimed to clearly identify the advantages and drawbacks of each topology, and to relate them with the required voltage and power levels. As an outcome, we point out the topologies that, for the required power level at the chosen switching frequencies, yield higher efficiency in the whole range of required operation points and that are expected to allow more important weight reductions.

When Blockchain Meets Smart Grid: Secure Energy Trading in Demand Response Management

Increasing demand for electricity necessitates the use of efficient mechanisms for demand response management (DRM) in the existing smart grid (SG) system. In the Industry 4.0 era, the usage of information and communication technologies in the energy industry revolutionized the existing grid called SG, which provides a bi-directional flow of energy and data. To handle the energy demand of the consumers, DRM is crucial. It provides the active participation of consumers in the energy trading system (ETS) between consumers and service providers. The traditional energy trading system (TETS) relies on the centralized system or trusted third parties, which may act as a single point of failure. So, it is essential to equip the SG system with a secure energy trading system (SETS) to provide privacy and security to the consumer's data. In this direction, one of the emerging technology, called blockchain, can handle the issue as mentioned above, which is a chain of decentralized and distributed transaction ledger that is retained and maintained by each user. It performs peerto- peer (P2P) energy transactions among different consumers, such as individual houses, using smart contracts, and without a central control body. In a decentralized system, each consumer has its energy storage locally generated using renewable energy resources (RES). In this article, SETS, a blockchain-based decentralized ETS framework, is proposed for storing and processing the data generated from smart meters (SMs). In SETS, miner node is designated to validate the requests of energy requirements, dynamic pricing, and time of stay. Then, an energy transaction execution approach is designed for SETS. The evaluation results obtained show that SETS outperforms the TETS in terms of computation time and communication costs.

Energy Internet, the Future Electricity System: Overview, Concept, Model Structure, and Mechanism

Energy Internet, a futuristic evolution of electricity system, is conceptualized as an energy sharing network. Its features, such as plug-and-play mechanism, real-time bidirectional flow of energy, information, and money can lead to significant benefits and innovation in electricity production and utilization. Energy Internet integrates small-scale renewable energy systems, electric loads, storage devices, and electric vehicles for effective transaction of power backed by emerging technologies such as Internet of Things, vehicle-to-grid, and blockchain. At present, there is no scaled-up working model of Energy Internet, and literature is scarce, which makes the research in this domain significant, novel, and timely. Given this, an attempt is made to develop the conceptual model of an Energy Internet, elaborate its structure and components, and discuss its operational principles. First, a comprehensive overview of Energy Internet is presented along with its aptness as a future evolution of electricity system. Second, concepts, architectures, and features that underpin Energy Internet are outlined. Third, concept of ‘Energy Intranet’ is introduced to denote the scaled-down version of Energy Internet, which embodies energy prosumers and local energy markets to form a local energy cluster. Finally, discussion is presented on the network structure of Energy Internet, relevance of emerging technologies and innovative operational mechanisms.

A Coupled-Inductor-Based Bidirectional Circuit Breaker for DC Microgrid

DC microgrids have attracted more and more attention with its universality, high efficiency, and potential application market. However, dc fault protection is still a challenge to the development of dc microgrids. In this article, a novel bidirectional dc solid-state circuit breaker based on coupled inductor is introduced. It can realize bidirectional energy flow and bidirectional isolation and interruption of short-circuit faults with fewer components. The working principle of the topology and the working process under different conditions are described, and some properties of the novel circuit breaker are explored, including minimum fault current ramp rate and load step analysis, which provide a reference for the selection of component parameters. Finally, the feasibility and performance of the novel bidirectional circuit breaker is evaluated by simulations and experiments.

The design of power supply for HF MRI superconducting magnet

High-field (HF) magnet resonance imaging (MRI) is designed as a large aperture human body imaging system. The superconducting magnet provides magnetic field B0 for HF MRI. The power supply is a key component, provides excitation and demagnetization functions for superconducting magnet. According to the requirements, the superconducting magnet power supply needs to be designed and developed with small volume and high reliability and bidirectional energy flow. A combination topology is proposed, including a pulse-width-modulation (PWM) rectifier, a dual-active-bridge (DAB), and a H-bridge. In this paper, the principle of the combination topology is introduced briefly. Meanwhile, the analysis and test results of a PWM rectifier based on hybrid active-neutral-point-clamped (ANPC) three-level are given.

Research on Applications of An Improved Current Type Push-pull Full bridge bidirectional DC-DC Topology in UPS

Uninterruptible power supply (UPS) boasts the superiority of fast dynamic response and clean output power, which can ensure the stable operation of the system and the safety and reliability of data. Currently, it takes up a large proportion in the backup power market and is extensively applied in key industries such as energy and the Internet. UPS is connected between commercial power and power load, and furnishes uninterrupted, reliable and high-quality power to vital loads when the input power fails. Bi-directional DC-DC converter can realize bi-directional flow of energy, which is functionally equivalent to two uni-directional DC-DC converters, rendering the system to carry the advantages of high power density and low cost, which has become a research focus at home and abroad in the passing years. The traditional current-mode push-pull full bridge topology fails to realize the soft start of the on-line UPS and stable operation of it under empty and light load. Based on this topology, the inductor secondary coil and two freewheeling diodes are added to make the push-pull tube work in any duty ratio state, thus meeting the design requirements of the bi-directional DC-DC converter in UPS. The working principle of the improved topology is described in this thesis, and Saber and Matlab are used for simulation analysis. Prototype is made and debugged to verify the feasibility of the design so as to achieve the expected design goals.

Integration of Novel Sensors and Machine Learning for Predictive Maintenance in Medium Voltage Switchgear to Enable the Energy and Mobility Revolutions.

The development of renewable energies and smart mobility has profoundly impacted the future of the distribution grid. An increasing bidirectional energy flow stresses the assets of the distribution grid, especially medium voltage switchgear. This calls for improved maintenance strategies to prevent critical failures. Predictive maintenance, a maintenance strategy relying on current condition data of assets, serves as a guideline. Novel sensors covering thermal, mechanical, and partial discharge aspects of switchgear, enable continuous condition monitoring of some of the most critical assets of the distribution grid. Combined with machine learning algorithms, the demands put on the distribution grid by the energy and mobility revolutions can be handled. In this paper, we review the current state-of-the-art of all aspects of condition monitoring for medium voltage switchgear. Furthermore, we present an approach to develop a predictive maintenance system based on novel sensors and machine learning. We show how the existing medium voltage grid infrastructure can adapt these new needs on an economic scale.

The reservoir network: A new network topology for district heating and cooling

Thermal district networks are effective solutions to substitute fossil fuels with renewable energy sources for heating and cooling. Moreover, thermal networking of buildings allows energy efficiency to be further increased. The waste heat from cooling can be reused for heating in thermal district systems. Because of bidirectional energy flows between prosumers, thermal networks require new hydraulic concepts. In this work, we present a novel network topology for simultaneous heating and cooling: the reservoir network. The reservoir network is robust in operation due to hydraulic decoupling of transfer stations, integrates heat sources and heat sinks at various temperature levels and is flexible in terms of network expansion.We used Modelica simulations to compare the new single-pipe reservoir network to a basecase double-pipe network, taking yearly demand profiles of different building types for heating and cooling. The electric energy consumed by the heat pumps and circulations pumps differs between the reservoir and base case networks by less than 1%. However, if the reservoir network is operated with constant instead of variable mass flow rate, the total electrical consumption can increase by 48% compared to the base case. As with any other network topology, the design and control of such networks is crucial to achieving energy efficient operation.Investment costs for piping and trenching depend on the district layout and dimensioning of the network. If a ring layout is applied in a district, the reservoir network with its single-pipe configuration is more economical than other topologies. For a linear layout, the piping costs are slightly higher for the reservoir network than for the base case because of larger pipe diameters.

Control, regulation and optimization of bidirectional energy flows for electric vehicles’ charging and discharging

Vehicular electrification plays a major role in the reduction of toxic greenhouse gas emissions linked to the transportation sector. However, the differential margin between electricity supply and demand is chaotic; and only a production/consumption balance could reconcile both ends. The adaptation of energy flows is therefore necessary to confront the gigantic energy waste related to electricity storage challenges. Consequently, electric vehicle batteries recently emerged as a solution to the actual limitation of storage capability. Indeed, they are used in this study as means of storage and retrieval of energy.Thus, this paper proposes a control and regulation algorithm aimed at reaching a balanced production/consumption system. The balance is acquired through the bidirectional control of the energy flows related to domestic residences, electric vehicles and the grid. Moreover, a multi-objective optimization of vehicular charging and discharging is assessed using the genetic algorithm to attain an optimal fulfillment of the system’s energetic needs. Once the regulation algorithm is set and the optimizations implemented, the algorithm’s simulation is performed using Matlab. Through the developed algorithm, we aim these major findings: 1. Regulate energy flows depending on supply and demand. 2. Optimize charging and discharging modes. 3. Flows merge towards the system’s equilibrium state.

Day-ahead optimization schedule for gas-electric integrated energy system based on second-order cone programming

This paper proposes an optimal day-ahead optimization schedule for gas-electric integrated energy system (IES) considering the bi-directional energy flow. The hourly topology of electric power system (EPS), natural gas system (NGS), energy hubs (EH) integrated power to gas (P2G) unit, are modeled to minimize the day-ahead operation cost of IES. Then, a second-order cone programming (SOCP) method is utilized to solve the optimization problem, which is actually a mixed integer nonconvex and nonlinear programming issue. Besides, cutting planes are added to ensure the exactness of the global optimal solution. Finally, simulation results demonstrate that the proposed optimization schedule can provide a safe, effective and economical day-ahead scheduling scheme for gas-electric IES.

Editorial: Autonomy and Intelligence in Neurorehabilitation Robotic and Prosthetic Technologies

Neurorehabilitation robotic technologies and powered assistive prosthetic devices have shown great potential for accelerating motor recovery or compensating for the lost motor functions of disabled users. The functioning of these technologies relies on a highly-interactive bidirectional flow of information and physical energy between a human user and a robotic system. Thus, key factors are integrity, intelligence and quality of the interaction loops. As a result, research in this field has focused on (a) enhancing the quality and safety of the physical interaction between disabled users and robotic systems while providing a high level of intelligence and adaptability for generating assistive and therapeutic force fields; (b) detecting the user’s motor intention with high spatiotemporal resolution to provide bidirectional human–machine interfacing; (c) promoting mental engagement through designing multimodal interactive interfaces and various sensory manipulation strategies. This Special Issue has collected papers that contribute to these three research areas, highlighting the importance of different aspects in human–robot interaction loops for augmenting the performance of neurorehabilitation robotic systems and prosthetic devices.

DC/DC half-bridge SST based on energy router

In this paper, a DC/DC half-bridge SST (Solid state transform) based on energy router is proposed. The structure mainly includes high-frequency transformer circuit, half-bridge circuit and control circuit. The DC side is converted to a high frequency AC signal through a half-bridge circuit. Then the high-frequency transformer circuit transmits the AC signal to the secondary side, and the secondary side is connected to the same half-bridge circuit for rectification to make electrical energy output in the form of DC. The whole circuit adopts symmetrical structure, which is beneficial to the bidirectional flow of energy. The simulation results verify the correctness and feasibility of the design scheme.

Analysis, Modeling and Implementation of a Switching Bi-Directional Buck-Boost Converter Based on Electric Vehicle Hybrid Energy Storage for V2G System

This paper presents a switching bi-directional buck-boost converter (SBBBC) for vehicles-to-grid (V2G) system. The topology can provide an energy bi-directional flow path for energy exchange between the Li-battery/supercapacitor (SC) hybrid energy storage system (HESS) of the electric vehicle and the grid. This topology not only has buck-boost capability, but also has the function of energy management. In this paper, the state-space averaging method is used to analyze the stability of the topology in boost and buck modes. The control strategy is given according to the state of charge (SOC) of the energy storage system to ensure that the output voltage and current are stable. And the Li-battery is charged in constant current (CC) and constant voltage (CV) mode. The voltage and current controllers are designed in the frequency domain based on bode plots. Finally, the electrical feasibility of the topology, the suitability of the design controller and control strategy are verified by simulation and experiment.

Energy-Efficient Information and Communication System for Smart Meter

The objective of this work is to develop an electricity Smart Meter, allowing the bi-directional energy flow in the Low Voltage (LV) grid. The developed prototype can be deployed in a Photovoltaic (PV) micro-production installation, being able to cooperate with the Distribution System Operator (DSO) regarding remote readings and dynamic voltage control procedures, while keeping the prosumer informed about the active power, as well as odd or faulty situations (e.g., no production). To accomplish the result proposed with functionalities that are useful in the distributed energy grid, this paper offers a device that is standard compliant by using DLMS, providing specific technical information to the DSO. Additionally, it has two low power wireless communication technologies: Bluetooth Low Energy (BLE), for short range local readings and configuration by the prosumer or maintenance teams; and Sigfox, a long range low power technology, which has a permanent storage and facilitates consultation of past and current records. The latter can be accessed by an Android application from a remote location.

Big data-oriented energy prosumption service in smart community districts: a multi-case study perspective

The smart grid achieves bidirectional information and energy flow between energy consumer and utility grid, aiding energy users not only to utilize energy, but also to produce, sell, and share energy with other consumers or with the utility grid. This type of energy user is referred to as the “prosumer”. Thus, prosumer management structures are important within energy market. However, prior studies on energy sustainability has paid little attention on prosumer involvement and management. Likewise, the continuous growth of cities has increased data processing complexity. Consequently, processing and analysis of historical, online, and real-time streaming data from energy sensors and metering devices has become a major issue in smart cities. Therefore, this research aims to present an architecture based on big data to improve energy prosumption in smart community districts by applying enterprise architecture approach grounded on The Open Group Architecture Framework (TOGAF). Accordingly, qualitative methodology is adopted to collect data by employing case study by focus group interview from two energy companies in Norway to preliminarily validate the architecture. Findings from the case studies was demonstrated in ArchiMate modeling language to evaluate the applicability of the architecture. Moreover, findings from this study provides practical scenario that energy service providers can refer to in designing their own energy data platforms. Essentially, the architecture can be utilized as a guide to help municipalities and policy makers in creating approach for energy data analytics in smart community districts towards making decisions for future energy prosumption planning.

Modeling of the electrical supply system of metropolitenwith a bi-directional energy flow

In order to improve the electromagnetic compatibility of the power supply systems of the metro with the supply network, it is advisable to organize a bi-directional exchange of energy between the source and the load. This article describes the structure of the metro power supply system with a four-quadrant DC drive based on a six-pulse bridge controlled rectifier, created its MatLab model, developed a control system of rectifier bridges with a separate operation algorithm, proposed an auto-regulation system based on a dual-circuit slave current-speed controller and calculated it parameters. When conducting a virtual experiment, it was possible to repeat schedule of movement of the electric train between the stations with high accuracy, to ensure the mode of energy recovery in the braking mode, to obtain the data necessary for calculating the energy performance of such a system. The resulting model will allow to investigate the energy efficiency of the metro power supply system at different operating modes and power line parameters.

Hybrid Micro-Grids Exploiting Renewables Sources, Battery Energy Storages, and Bi-Directional Converters

This paper analyzes trends in renewable-energy-sources (RES), power converters, and control strategies, as well as battery energy storage and the relevant issues in battery charging and monitoring, with reference to a new and improved energy grid. An alternative micro-grid architecture that overcomes the lack of flexibility of the classic energy grid is then described. By mixing DC and AC sources, the hybrid micro-grid proposes an alternative architecture where the use of bi-directional electric vehicle chargers creates a micro-grid that directly interconnects all the partner nodes with bi-directional energy flows. The micro-grid nodes are the main grid, the RES and the energy storage systems, both, on-board the vehicle and inside the micro-grid structure. This model is further sustained by the new products emerging in the market, since new solar inverters are appearing, where a local energy storage for the RES is available. Therefore, the power flow from/towards the RES becomes bi-directional with improved flexibility and efficiency.

Dispatching optimization model of gas-electricity virtual power plant considering uncertainty based on robust stochastic optimization theory

With the rapid development of renewable energy, virtual power plant technology has gradually become a key technology to solve the large-scale development of renewable energy. This paper focuses on the stochastic dispatching optimization of gas-electric virtual power plant (GVPP). Based on this, wind power plant, photovoltaic power generation and convention gas turbines are used as the power generation side of GVPP. Power-to-gas (P2G) equipment and gas storage tank can realize the conversion and storage of electricity-gas energy. Price based demand response and incentive based demand response are introduced into the terminal load side to regulate the user’s electricity consumption behavior. GVPP bilaterally connects power network and natural gas network, which realizes the bidirectional flow of electricity-gas energy. Firstly, taking the maximization of economic benefits as the objective function, combined with the constraints of power balance, system reserve and so on, a dispatching optimization model of GVPP participating in multi-energy markets is constructed to determine the operation strategy. Secondly, wind, solar and other clean energy have the characteristics of random and fluctuation, which threaten the stable operation of the system. Therefore, a stochastic dispatching optimization model of GVPP considering wind and solar uncertainty is established based on robust stochastic optimization theory. Thirdly, the evaluation indicators of GVPP operation is determined, which can comprehensively evaluate the economic benefits, environmental benefits and system operation of virtual power plant. Finally, in order to verify the validity and feasibility of the model, a virtual power plant is selected for example analysis. The results show that: (1) After the implementation of price based demand response and incentive based demand response, the system load variance changes from 0.03 to 0.013. Through the comparison of load curves, it is found that demand response can play a role of peak-shaving and valley-filling and smooth the power load curve; (2) Stochastic optimization theory can overcome the uncertainty of wind and solar by setting different robust coefficients Γ which reflects the ability of the system to withstand risks; (3) The optimization effect after introducing the P2G subsystem makes the amount of abandoned clean energy close to zero. The operation risk of system is reduced, and the carbon emissions are reduced by 370 m3 too. The market space is expanded from electricity market mainly to natural gas market and carbon trading market.

Performance of Multi Port Bi Directional Converter for Energy Management System

The focal intention of this work is to provide incessant power delivery to the load by finding out the accessible supply sources optimistically among the four sources namely solar, wind, battery and diesel generator. Depends up on the availability the sources can be connected in order to have a sustainable power system. Due to the abnormalities of energy sources Solar and Wind, energy storage units are required in order to provide the sustainable constant voltage to the load without any interruption. The five port convert is used to interface the Solar, Wind, Battery, Diesel Generator sources and the load. The circuit topologies of different boost converters are discussed in [1]. The five-port converter can make sense of bidirectional flow of energy between the source, storage medium and load. Also ensure the DC bus maintaining stable voltage [2].

ENERGY EFFICIENCY OF THE SUBWAY ELECTRICAL SUPPLY SYSTEM WITH ELECTRICAL ENERGY RECOVERY AT BRAKING

Purpose. The purpose of the paper is to assess the efficiency of the subway power supply system, which uses a four-quadrant DC drive with energy recovery in the supply network in the braking mode. Methodology. We have applied the theory of electrical circuits and mathematical simulation in Matlab package. Results. The theoretical dependence of the efficiency of the electrical supply system with a bidirectional flow of energy on the coefficient of resistive short circuit at the load terminals has been obtained. The theoretical result is verified by modeling. Originality . The equivalent circuit of the subway power supply system with a four-quadrant DC drive and the possibility of energy recovery to the supply network in braking mode is developed, its parameters are determined, and the schedule of the electric train movement was set. Practical value. The use of the obtained dependencies and simulation results will allow to determine the direction of the future development of the subway power supply system and optimize its energy efficiency.