Energy Router Research Articles

A Backflow Power Suppression Strategy for Dual Active Bridge Converter Based on Improved Lagrange Method

Dual-active bridge (DAB) converters are receiving increasing attention from researchers as a critical part of the power transmission of energy routers. However, the DAB converter generates a large backflow power in conventional control mode, and when the load is mutated, its output voltage takes longer to return to the reference value accompanied by large fluctuations. To solve the above problems, a hybrid strategy is proposed in this paper to optimize the converter. The mathematical models of the transmitted power and the backflow power were firstly derived through in-depth analysis of the DAB converter under extended-phase-shift (EPS) modulation, and the suppression of the backflow power was performed according to the improved Lagrange method utilized in the obtained results. Moreover, considering the poor dynamic characteristics of DAB converters under PI control, according to the state space average model of output voltage in the paper, a model prediction control equation is established to improve the dynamic response of the converter by predicting the output voltage value at the next moment. The simulation results verify the effectiveness of the optimization strategy presented in the text.

Energy Router Applications in the Electric Power System

Energy router is being investigated to replace conventional transformer in the electric grid. Improvement so far observed in use of converter makes possible the intelligent integration between systems with different characteristics’ in terms of frequency and voltage levels as well as exploitation of generation sources and storage systems typically operating in DC. Consequently, it is believed that Energy Router is able to interconnect different portions of electrical networks and at different voltage levels and types. The Energy Router is an assembly of converters isolated by a medium or high frequency transformer. In its design, different voltage levels and types are made available to achieve high results in terms of system integration, efficiency and flexibility. This paper evaluates the main potentials of this technology if widely introduced in the main power system. Starting from the single component description, a couple of possible applications are presented and discussed.

Triple Active Bridge Based Multiport Energy Router for Subsea – Renewable Interconnection

In order to supply reliable power to the subsea loads at high system efficiency and low emissions, there is a growing interest in employing offshore renewable resources close to the point of use. However, such system has predominantly stayed in the conceptual stage so far. Hence, there is a need to develop methodologies for interconnecting multiple renewable sources with offshore loads. This paper proposes a Multiport Energy Router (MER) based on a Medium Frequency (MF) Solid-State Transformer (SST) that integrates renewable energy sources (RES) and Energy Storage Systems (ESS) to supply clean energy for subsea loads. The MER forms a three-port network, where HVDC Wind Turbine Generator (WTG) power system and MVDC ESS are interfaced with subsea loads. The MER is realized by series-parallel combination of Triple Active Bridge (TAB) converters. The TAB modules are critical to enhance the power density, fault-tolerance, and efficiency of the proposed system. In this paper, a novel simple algorithm for extending soft-switching region of TAB by selecting optimal control variables is proposed. Moreover, this paper presents a control strategy for the MER, which addresses the DC-link voltage imbalance issue for each of the cascaded TAB converters. The simulation and the Hardware-in-the-Loop (HIL) results based on Typhoon-HIL system are presented to verify the proposed converter operation and the control strategy.

Bifurcation Behavior Analysis and Stability Region Discrimination for Series-Parallel Architecture Electric Energy Router

Electric energy routers (EERs) can effectively deal with the energy management issues caused by the access of multi-sources and multi-loads. Different from the energy transmission form in the existing series architecture EER (SA-EER) for low-voltage distribution networks, a new series-parallel architecture EER (SPA-EER) has the advantages of high-power transmission capability and reactive power flexible operation. However, if controller parameters change beyond their critical stability boundaries, SPA-EER will produce slow- and fast-scale bifurcation behaviors, which are manifested as low- and high-frequency oscillations of port voltages or port currents in varying degrees. To avoid the system instability caused by controller parameter changes, how to discriminate the stability regions of controller parameters for SPA-EER is a key research content in this paper. To this end, the stroboscopic mapping discrete model of SPA-EER system is first established, and system bifurcation behaviors are analyzed based on bifurcation theory. Furthermore, the critical stability boundaries of controller parameters are discriminated by using Jacobian matrix, root locus and bifurcation diagram. After that, a time delay feedback control (TDFC) is employed to suppress system bifurcation behaviors. Finally, the correctness of bifurcation analysis and the effectiveness of TDFC are verified by a hardware-in-the-loop (HIL) experimental platform.

A novel energy router based on multi‐winding line frequency transformer

AbstractEnergy routers based on the electronic power transformer are suitable for the AC–DC hybrid grid with multiple voltage levels, but their structures are complex. This paper proposes a novel energy router based on the multi‐winding line frequency transformer. By a combination of a multi‐winding line frequency transformer and power electronic devices, the proposed energy router can take advantage of the high reliability of the multi‐winding line frequency transformer and the high controllability of power electronic devices. The proposed energy router is suitable for the AC–DC hybrid grid with multiple voltage levels and has the characteristic of a simple structure. The simulations and experimental results demonstrate the effectiveness of the proposed energy router.

Internet of energy (IoE) adoption for a secure semi-decentralized renewable energy distribution

Peer-to-peer power systems are becoming more common due to the increasing popularity of renewable energy and the need for clean energy security in electrical grids. The Internet of Energy proposes energy routers to connect devices, optimize energy dispatch, and manage energy flow. Reliable transfer needs an effective and secure energy routing algorithm. This research outlines an innovative algorithm to manage routing communication securely and minimize processing time and energy loss. It uses a semi-decentralized method to offload computing tasks onto energy routers and a central database for routing information.The proposed energy routing algorithm is tested in MATLAB to assess its handling rate, security, malware filtering, and performance. The results showed a handling rate of over 99.7%, an infection probability of less than 1%, a packet delivery rate of over 99%, and no data loss. Finally, given minimum power loss, the proposed energy routing algorithm requires an energy inquiry of 3.78 seconds per energy router inquired and 2.11 seconds in energy routing per distribution line and energy router combined.

Exergy analysis and particle swarm optimization of clean energy router based on a solar‐thermal‐assisted advanced adiabatic compressed air energy storage system

AbstractThe clean Energy router based on advanced adiabatic compressed air energy storage (AA‐CAES) has the characteristics of large capacity, high efficiency and zero carbon emission which are an effective mitigation scheme for the integration of renewables and peak‐shaving and a new clean energy technology for storing energy in the world. A novel solar‐thermal‐assisted AA‐CAES (ST‐AA‐CAES) is proposed in this paper, integrating variable thermal energy storage to improve the system electric to electric (E2E) and round‐trip efficiency (RTE). The efficiency and exergy evaluation of ST‐AA‐CAES are carried out to determine the performance of ST‐AA ‐CAES. The results illustrate that E2E, RTE, and exergy efficiency can reach 56.4%, 95.5%, and 55.9%, respectively. Meanwhile, the details of exergy efficiency and destruction of each subsystem are demonstrated. Particle swarm optimization algorithm is applied to analyse the economy of optimally integrated energy systems which has the advantages of high accuracy, convenient implementation and fast convergence. The system can be applied in abundant solar energy resources area with high efficiency and multi‐energy supply capability.

An energy router based on multi-hybrid energy storage system with energy coordinated management strategy in island operation mode

With the high penetration of renewable energy, its intermittency and volatility also bring challenges to traditional power system such as maintaining reliable operation of system and improving the utilization of renewable energy. Under the background of Energy Internet (EI), energy router (ER) emerges as the times require. Aiming to improve the ability of support of energy storage units to DC buses and suppressing power shocks both inside and outside the ER, in this paper, an ER based on multi-hybrid energy storage system (MHESS) is proposed. As the principle of maximizing the utilization of renewable energy, a corresponding energy coordinated management strategy is proposed. Charging/discharging timespan optimization model is established to ensure MHESS as available as possible. The reference power of MHESS is allocated based on the proposed optimization model. Simulation analysis of different working conditions in 4 operation scenarios are carried out and the results show that the power oscillation on different buses of ER can be dampened within 0.1s and the bus voltages fluctuate within 2% while operation scenarios are switched, which verifies the feasibility and effectiveness of the proposed energy coordinated management strategy.

Distributed neurodynamic optimization for multi-energy management with time-varying external disturbances considering time-varying emission limitations and load demand in multi-microgrid

An emerging time-varying distributed multi-energy management problem (MEMP) considering time-varying load and emission limitations for resisting time-varying external disturbances and communication time delays in the multi-microgrid (MMG) system is investigated. Each microgrid (MG) contains some smaller microgrids (SMGs), which are connected by energy routers (ERs) of the system and can monitor energy in real-time with each other. In addition, a time-varying multi-energy management optimization model (MEMOM) is proposed in this paper in order to minimize the total cost of the MEMP which considers environmental cost, renewable energy cost and fuel cost. Furthermore, time-varying distributed neurodynamic optimization algorithms are proposed for solving the above MEMP based on consensus theory and sliding mode control technique. Compared with the optimization algorithms which consist of symbolic functions proposed in traditional energy management problems, algorithms consisting of hyperbolic tangent functions proposed in this paper can effectively reduce the oscillation of the algorithms and improve the stability of algorithms. Furthermore, the algorithm can converge the optimal trajectory of optimization problems with time-varying external disturbances and communication time delays. Meanwhile, the stability and convergence of the algorithms are proved theoretically by constructing appropriate Lyapunov functions. Finally, the performance evaluation results of numerical simulations show that the proposed algorithms can efficiently handle energy trading under time-varying load and maintain excellent stability with time-varying external disturbances and communication time delays.

The effect of the thyristor energy router on harmonics

Energy routers (ER) are the key equipment of the energy internet that provides control over bidirectional power flows and the voltage level of an electric network. The paper presents the thyristor-powered ER (TER) for an Internet-style medium voltage distribution electric network (6, 10, 20 kV). The developed scheme of the device implements longitudinal and transverse voltage regulation at the ER connection point and it allows changing the power flow and the voltage level in the network. The article is devoted to the study of the harmonic components of voltage introduced into the electrical network by the semiconductor elements of the TER. A mathematical and a computer model and a prototype of an electric network section with a TER have been developed. The studies carried out with the help of the developed models have shown that the device does not significantly distort sinusoidally. The harmonic components factor of the output voltage has acceptable values over the entire range of an effective regulation.

Design and Control of a Novel Wireless Energy Router With Independent Power Transmission Channels

Energy routers are intelligent power electronic systems that enable energy sharing and flexible power flow regulation among various distributed energy sources. Combining the excellent feature of wireless power transfer technology for contactless transmission of electrical energy, this article proposes a novel wireless energy router to realize the power exchange of multiple energy storage devices, such as various mobile electronics, electric vehicles, and energy storage stations. Independent power transmission channels with specific operating frequencies are built between any two of the power-exchanging units. The multiple resonating decoupling compensations are designed and implemented, which offer each power-exchanging unit and various resonate operating frequencies while suppressing the frequency components from irrelevant channels. Moreover, through generation by the bidirectional multilevel converter, the drive voltage of each unit can naturally realize the synthesis of multiple-frequency voltage components. In addition, the decoupled dual-side phase-shift control with capacitor voltage balancing strategy is proposed to regulate the power flow in each power channel. As a result, simultaneous energy sharing among power storage devices can be achieved. And the power flows can be adjusted independently without cross interference. Finally, both simulation and experimental results are presented to verify the effectiveness of the proposed wireless energy router.

A New Five-Port Energy Router Structure and Common Bus Voltage Stabilization Control Strategy

Multi-port energy routers are a core device that integrates distributed energy sources and enables energy-to-energy interconnections. For the energy routing system, the construction of its topology, the establishment of internal model switching and the control of common bus voltage stability are the key elements of the research. In this paper, a five-port energy router structure is proposed, including a PV port, an energy storage port, a grid-connected port, a DC load port, and an AC load port. Among them, the energy storage port and the grid-connected port involve bidirectional energy flow, which are the core ports of control. For the system state, a model switching strategy is proposed based on the topology and the port energy flow direction. When the external conditions change, the system can be stabilized by means of a quick response from the energy storage port. When the energy storage is saturated, the state is switched, and the grid-connected port works to achieve system stability. The rapid stabilization of the bus voltage and the free flow of energy are achieved by combining the fast response of the model predictive control with the properties of multiple model switching. Finally, the feasibility of this energy router topology and control strategy is verified by building simulations in MATLAB.

A Hierarchical Coordinated Control Strategy for Power Quality Improvement in Energy Router Integrated Active Distribution Networks

The energy router (ER) is a current power electronic device which can integrate distributed energy, provide power for different types of loads, and simultaneously realize the free flow of energy. In traditional active distribution networks, power quality is affected due to the access of photovoltaics (PV) and various loads. Hence, this problem can be improved by accessing the ER. This paper shows the power quality improvement of the grid when the ER is used to integrate PV, energy storage, and AC/DC loads. At the same time, an energy coordination strategy for ER is proposed. The IEEE 13 node model is developed to analyze power quality fluctuations when distributed energy and AC/DC loads are directly connected to the grid. For the power quality analysis, five indicators were selected and the hierarchical analysis method was used to obtain the indicators of power quality. After the use of ER under the coordinated control of ER, the energy is distributed twice and the power quality of the grid improves. The feasibility of ER topology and the control strategy have been verified through an established active distribution networks model with ER. It is verified that when the ER is connected to active distribution networks, the power quality improves accordingly, and it can effectively deal with the characteristics of distributed energy fluctuations and improve the flexibility of the power grid.

Multi-agent deep reinforcement learning based distributed control architecture for interconnected multi-energy microgrid energy management and optimization

Environmental and climate change concerns are pushing the rapid development of new energy resources (DERs). The Energy Internet (EI), with the power-sharing functionality introduced by energy routers (ERs), offers an appealing alternative for DER systems. However, previous centralized control schemes for EI systems that follow a top-down architecture are unreliable for future power systems. This study proposes a distributed control scheme for bottom-up EI architecture. Second, model-based distributed control methods are not sufficiently flexible to deal with the complex uncertainties associated with multi-energy demands and DERs. A novel model-free/data-driven multiagent deep reinforcement learning (MADRL) method is proposed to learn the optimal operation strategy for the bottom-layer microgrid (MG) cluster. Unlike existing single-agent deep reinforcement learning methods that rely on homogeneous MG settings, the proposed MADRL adopts a form of decentralized execution, in which agents operate independently to meet local customized energy demands while preserving privacy. Third, an attention mechanism is added to the centralized critic, which can effectively accelerate the learning speed. Considering the bottom-layer power exchange request and the predicted electricity price, model predictive control of the upper layer determines the optimal power dispatching between the ERs and main grid. Simulations with other alternatives demonstrate the effectiveness of the proposed control scheme.

A Novel Knapsack Algorithm-Based Energy Routing in a Microgrid

The increase in penetration of renewable energy sources has transformed the existing grid into a multisource and multipath energy network. For real-time energy transactions in the new microgrid, it is essential to realize an energy router interface, which is the core of the energy internet. The energy router controls the bidirectional energy and data flow and achieves end-to-end energy transmission efficiently. With this consideration, this article proposes a new energy routing algorithm based on the knapsack optimization technique. The proposed work aims to minimize the net energy from the main grid and efficiently utilize solar photovoltaic (SPV) energy through meticulous energy routing. The effectiveness of the proposed work is validated for case studies with various types of loads viz residential, non-residential, and electric vehicle loads. In this work, the best set of loads for optimal energy routing with minimum energy costs are determined. The results show a substantial reduction ranging from 16 to 28% in the peak energy drawn from the grid and at the same time, the cost of electricity to be paid to the utility is noticeably reduced in the range of 39% to 50% for various load types. Further, a sensitivity analysis is carried out to evaluate the effect of variations in input parameters such as PV output, and load demand on the cost of electricity.

A Three-Port Energy Router for Grid-Tied PV Generation Systems With Optimized Control Methods

In grid-tied photovoltaic (PV) generation systems, intelligent energy management is required to maximize its performance. In this article, a novel three-port energy router with optimized control is proposed for this application. The proposed converter can interface among three ports (PV source, battery, and dc-link) with high integration. The PV panel is connected to the battery through an interleaved boost structure on the primary side. The primary-side PV-battery system and secondary-side dc-link are connected through a dual-active-bridge (DAB) converter. The battery operates as an energy buffer to compensate for the power mismatch due to the intermittent nature of the PV source. According to the daily power profile and intelligent power management between the grid and battery, six operating modes are possible. Optimized control strategies are customized in different operating modes. The maximum-power-point-tracking (MPPT) of the PV panel can be always realized. The zero-voltage-switching (ZVS) condition for all <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, reducing circulating current over a wide range, and flexible energy flow among three ports are all taken into considerations in the design. To verify the proposed concept, a 500 W rated prototype is designed. The designed prototype exhibits high efficiency in various operating modes. The experimental results agree well with the theoretical analysis.

Design and Analysis of a DC Solid-State Circuit Breaker for Residential Energy Router Application

Energy routers act as an interface between the distribution network and electrical facilities, which meet the requirements of clean energy substitution and achieve the energy sharing and information transmission in the energy network. However, the protection of the dc load side of residential energy routers including interruption and isolation of short-circuit fault currents is vital for discussion. Since the traditional mechanical and hybrid circuit breakers for dc fault protection have the drawback of slow operation, a solid-state circuit breaker (SSCB) is an optimal solution for fast dc fault interruption. In this paper, a dc SSCB is proposed that uses an RCD + MOV snubber circuit, which is considered the best and most complete circuit used in common SSCBs. There are two main contributions in this paper: First, a dc SSCB is designed, which isolates both positive and negative terminals of a circuit and its working principle and operating modes along with the formulas for calculation of crucial time intervals, voltages, and currents along with the design procedure are provided. Second, a soft turn-on auxiliary is designed to prevent a high current surge caused by the capacitance difference between the source and the load. The experimental results demonstrate the proper performance of the topology and the validity of the findings.

The Energy Management of Multiport Energy Router in Smart Home

Although smart home has received wide attention in recent years, numerous scholars focus more on energy optimization strategy than energy dispatch hardware device (named energy router). Meanwhile, this energy router should have several features, i.e., high renewable energy utilization, energy multi-port and low volume. Thus, this paper designs a nine-port energy router regarding smart home and proposes a multimode hierarchical management strategy for this energy router. First, for the multi-port demand of wind, solar, storage and utilization, this paper presents a nine-port energy router to improve the renewable energy consumption and power supply flexibility. In addition, to reduce the volume of the energy router, a non-isolated AC/DC hybrid topology is constructed through embedding the integrated power electronic converters, which achieves the miniaturization of the energy router. In order to improve the renewable energy utilization rate, the decentralized module control is proposed for the components of energy router to provide the voltage and frequency support for system, and realizes the power sharing of distributed generations (DGs). Furthermore, the power exchange control with three-mode switching is proposed to guarantee the global energy flow balance under complex conditions. Eventually, the feasibility of the energy router is verified by the simulation and experiments.

Distribution of renewable energy through the energy internet: A routing algorithm for energy routers

Fossil fuels are rapidly running out, and with the demand for environmentally friendly energy sources increasing, power grids are looking for distributed power generation-based renewable resources. The distribution of these energy sources is significantly linked to the development of smart microgrids, which are also extensively connected with the energy internet. This paper explores the energy internet operation, focusing on developing a routing algorithm for an energy router. The energy routing algorithm is further substantiated with the aid of simulations. This algorithm can find all the paths available for energy transmission between two nodes and selects the track with the most negligible losses as the path for transmission. All the possible routes are displayed along with the losses associated with each direction to ensure that the approach with the lowest losses is taken. The algorithm is also tested for 24 h at an hourly interval to observe the change in power transmitted on the system.

Overview of energy routers control strategies

In order to solve the problem of effective utilization of renewable energy, energy Internet technology came into being. As the key equipment of the energy Internet, the research on energy routers is of great importance. This paper introduces the energy router from the aspects of structure and operation mode, and summarizes a general energy router structure. At the same time, the control strategies of the energy router are systematically discussed. In view of the complex and diverse control strategies of the current energy router, this paper summarizes the research status of energy router control strategies and discusses the control strategies according to different classification methods.