Future Renewable Electric Energy Delivery And Management Research Articles

Implementation and Design of FREEDM System Differential Protection Method Based on Internet of Things

This paper introduces an enhancement of the protection and operation of the Future Renewable Electric Energy Delivery and Management (FREEDM) system. It uses the solid-state transformers to connect the residential A.C. and D.C. microgrids to the distribution system and fault isolation devices for faulty line isolation. In this paper, a current differential protection scheme has been proposed to detect faults in the FREEDM-based microgrid network. This method is based on the current measurement at the two-line terminals using phasor measurement units to ensure data synchronization and minimize the measuring error. Also, a communication scheme that is based on the Internet of things technology and Wi-Fi is constructed for data monitoring and interlinking between the relays, transducers, and the fault isolation devices in the two-terminals lines. A hypothetical FREEDM system has been used for the verification and testing of the proposed method. Different fault types at different locations and fault resistances have been applied to prove the effectiveness of the proposed protection method in detecting the fault condition. The performance of the proposed method is investigated using the security, dependability, and accuracy indices. A prototype of the FREEDM system is designed, implemented, and tested using the Proteus software simulator and in the laboratory. The results prove the efficiency of the proposed protection method in detecting and isolating the fault conditions in a fast, reliable, and accurate manner. Moreover, the protection scheme achieved high accuracy for all faults, equal to 98.825%.

Adaptive Protection Scheme for FREEDM Microgrid Based on Convolutional Neural Network and Gorilla Troops Optimization Technique

Microgrids (MGs) suffer from unpredictable faults on the feeders for various random reasons. These faults could obstruct the stability of the MG operation and damage the components. Moreover, many uncertainties elements affect the MG’s response to faults, such as faults’ types and locations and resistances, MG operation modes, DG penetration levels, load variations, and system topologies. Therefore, fault detection, classification, and location are vital for the MGs as they provide rapid restoration and protect the components. This paper proposes an adaptive protection (AP) scheme for the future renewable electric energy delivery and management (FREEDM) system. The proposed scheme is based on the convolution neural network (CNN), in which the measured current and voltage at buses are processed in multidimensional arrays for the images’ identification and classification. The gorilla troops optimization (GTO) technique has been used to improve the CNN by acquiring the optimal architecture and hyperparameters of the proposed CNN. The proposed protection scheme can detect the system fault, classify the fault type, and determine the fault location using three proposed CNN-GTO protection scheme models. A communication channel has been performed to transfer the data, information, and tripping signals between the different devices in the FREEDM system. The proposed method is tested using a hypothetical FREEDM microgrid system under different fault conditions. The results show that the proposed CNN-GTO models can detect, classify, and location feeder faults in the FREEDM system with high accuracy. A comparison with the existing schemes such as Support vector machine, Fuzzy logic, conventional CNN, and wavelet-based CNN is performed. The optimized CNN-based GTO models can achieve an overall accuracy for fault detection, classification, and location of 99.37, 99, and 98.2%, respectively.

Delay-Aware Energy-Efficient Joint Power Control and Mode Selection in Device-to-Device Communications for FREEDM Systems in Smart Grids

Cellular technology with long-term evolution (LTE)-based standards is a promising technology for smart grid communication networks. However, the integration of cellular technology and smart grid communications is a significant challenge due to the transmission of simultaneous and delay-sensitive smart grid data. The Device-to-device (D2D) communications are proposed as critical solutions to enhance the performance of the LTE. In this paper, we study energy efficiency and delay problems in D2D underlaying cellular communications for the future renewable electric energy delivery and management (FREEDM) system in smart grid with different message sizes and varying channel conditions. We adopt a D2D-assisted relaying framework to assist links that meet poor channel conditions in order to increase the data rate of intelligent energy management devices with large size report. We propose a joint power control and mode selection scheme to deal with the problem and develop a brute-force-based algorithm to find the solutions. We conduct simulations to show the effectiveness of the proposed scheme in balancing the trade-off between energy efficiency and end-to-end delay and show significant energy efficiency improvements when exploiting the proposed scheme compared to direct and relaying schemes in a variety of different conditions.

Design of Over/Under Voltage Protection Relay using Arduino Uno for FREEDM System

This paper presents a new design for over/under voltage (OV/UV) protection scheme using Arduino microcontroller. The protection scheme is designed to protect the solid-state transformer (SST) branch of a Future Renewable Electric Energy Delivery and Management (FREEDM) system. It is used as backup protection for the instantaneous, momentary and temporary voltage fluctuation of distribution medium voltage loop. Very simple, user-friendly software and hardware simulators are created to represent a branch of the FRREDM network with the designed OV/UV relay. A software program is formulated using c-code through Proteus software package and easily integrated to the hardware circuit. The designed microcontroller monitors the network voltage and the OV/UV relay energies in case that its value exceeds a preset limit according to IEEE 1159. To validate and prove the effectiveness of the proposed system, different tests are performed for both software and hardware simulators at instantaneous, momentary and temporary OV/UV operation conditions. The results are compared with IEEE 1159 standard values and shows fine and high accuracy.

Over Current Protection Relay using Arduino Uno for Future Renewable Electric Energy Delivery and Management (FREEDM) System

The FREEDM (Future Renewable Electric Energy Delivery and Management) system is a smart grid that enables wide integration between the Distributed Renewable Energy Resources (DRER) and Distributed Energy Storage Devices (DESD) with the conventional distribution system. This paper presents the design and implementation of an Arduino Uno microcontroller-based overcurrent relay with different characteristics (inverse, very inverse and extremely inverse) for FREEDM systems. An open source model with simple utilization of both hardware and software is created. A practical printed circuit board is designed with the required inputs and outputs to monitor and protect the branch connecting solid state transformer (SST) to the closed loop zones in the FREEDM system. A special program is designed using Proteus software package and easily integrated to the hardware card. To validate the proposed relay, the inverse, very inverse and extremely inverse overcurrent relay characteristics are tested using the proposed system simulator and compared with the characteristic recorded by the well-known IEC 60255-151standard. In order to guarantee the effectiveness of the system, a practical circuit including the proposed relay is formed, connected to a small load (motor) and normally inverse relay characteristic is tested. The proposed protection scheme proves high performance and accurate results.

Protection Coordination Optimization for FREEDM (Future Renewable Electric Energy Delivery and Management) System

Protection Coordination Optimization for FREEDM (Future Renewable Electric Energy Delivery and Management) System

Dynamic Modeling and Feasibility Analysis of a Solid-State Transformer-Based Power Distribution System

This paper presents a comprehensive state-space dynamic model of a future power distribution system for plug-and-play interface of distributed renewable energy resources and distributed energy storage devices. The system, called the future renewable electric energy delivery and management (FREEDM) system, comprises of multiple solid-state transformers (SSTs), and load, generation, and storage connected to each SST in a distributed network. The system allows for high penetration of renewable generation with energy storage at the distribution level. A physics-based 70th-order state-space average model is first developed considering the physical and controller properties of a single-SST FREEDM system along with its distribution components. This fundamental model is then extended to build a multi-SST FREEDM system for feasibility and dynamics behavior analysis of the entire system, which is essential to ensure system power balance. The full average model with multiple SSTs has been incorporated in an IEEE 34 bus distribution testbed for a scaled analysis of the system.

15-kV/40-A FREEDM Supercascode: A Cost-Effective SiC High-Voltage and High-Frequency Power Switch

High-voltage wide bandgap semiconductor devices such as the 15 kV SiC mosfet have attracted great attention because of their potential applications in high-voltage and high-frequency power converters. However, these devices are not commercially available at the moment, and their high cost due to expensive material growth and fabrication may limit their widespread adoption in the future. In this paper, a 15-kV 40-A SiC three-terminal power switch, the Future Renewable Electric Energy Delivery and Management (FREEDM) supercascode, is reported for the first time, which is based on a series connection of 1.2-kV SiC power devices. Compared with the monolithic 15-kV SiC mosfet , the FREEDM supercascode demonstrates obvious advantages in cost and thermal conductivity. The design and voltage-balancing mechanism of the FREEDM supercascode are introduced, and the performance including the voltage balancing, conduction characteristics over a wide range of temperatures, and dynamic switching performance, is analyzed. The FREEDM supercascode's low cost and excellent thermal dissipation capability will facilitate early applications of SiC in very high voltage and high frequency power converters.

A Novel Method for Fault Detection in Future Renewable Electric Energy Delivery and Management Microgrids, Considering Uncertainties in Network Topology

The use of solid state transformers (SSTs) in microgrids has created a new kind of network called Future Renewable Electric Energy Delivery and Management (FREEDM) microgrid. The FREEDM microgrid provides an appropriate means for enhanced energy management, loss reduction, and network flexibility by reducing the number of converters used for a variety of AC-DC links. In this work, we propose a novel method for fault detection in FREEDM microgrids when considering uncertainties in network topology. The proposed method makes use of the Clarke and S-transforms to characterize the transients in three-phase current and voltage waveforms in the event of a fault. The extracted features of the waveforms will be used to form appropriate indices for detection, location, and characterization of the fault. The main feature of the proposed method is its capability to operate in a dynamic microgrid with varying topology. The performance of the proposed method is investigated by applying it to a sample FREEDM microgrid with ring and radial structures. It is shown that the proposed method is well capable of fault detection and diagnosis while being able to differentiate between short-circuit faults and switching transients due to variations in the network topology.

Battery Degradation and Cost Analysis of a Lithium Ion Battery System for a 1 MW Green Energy Hub (GEH)

Studying higher renewable energy penetrations during the electricity generation phase, the Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center has focused on supporting the battery degradation and cost analysis portion of a commercial 1 MW green energy hub (GEH). Cost analysis and battery degradation modeling will be used as part of a coupled approach and consist of the following software applications: NREL's System Advisor Model (SAM) - for identification of load requirement and summarization of PV productions; COMSOL Multiphysics - for determination of efficient electrochemical battery energy storage system (BESS); and MATLAB – for the implementation of state of charge (SOC), state of health (SOH), and peak shaving algorithms. The GEH will provide for various grid services using 20% renewable energy penetration and a Lithium ion based (Li-ion) BESS. Preliminary results using a LiFePO4 based BESS are presented below. Technical Approach with Preliminary Results The LiFePO4 battery was cycled to determine SOC and SOH using the Versastat 4 Potentiostat with the measured data being used as a baseline for the development of the COMSOL model. SAM The System Advisor Model (SAM) is a model developed by the U.S. Department of Energy and National Renewable Energy Laboratory to analyze sustainable energy systems. The SAM was used to determine the photovoltaic footprint capable of supporting 20% penetration. Fig 1. COMSOL COMSOL Multiphysics is a general-purpose software platform, based on advanced numerical methods, for modeling and simulating physics-based problems. COMSOL was used to model battery degradation and the affect of multiple cycling characteristics in a LiFePO4 cell. Fig 2. MATLAB MATLAB is matrix-based software that uses programming language for numerical computation. MATLAB was used for computation and data analysis of the peak shaving algorithm. Fig 3. Acknowledgement This work was supported by the FREEDM ERC program of the National Science Foundation under award number EEC-08212121. References Dubarry, Matthieu, Liaw, Bor Y. (2009). Identify capacity fading mechanism in a commercial LiFePO4 cell Journal of Power Sources Vol 194, pg 541-549.Kim, Jae-Hun, Woo, Sang C., Park, Min-Sik, Kim, Ki J., Yim, Taeeun, Kim, Jeom-Soo, Kim, Young-Jun. (2013). Capacity Fading Mechanism of LiFePO4 Based Lithium Secondary Batteries for Stationary Energy Storage, Journal of Power Sources Vol 229, pg 190-197.Yang, Ye, Li, Hui, Aichhorn, Andreas, Zheng, Jianping, Greenleaf, Michael. (2014). Sizing Strategy of Distributed Battery Storage System With High Penetration of Photovoltaic for Voltage Regulation and Peak Load Shaving. IEEE Transaction on Smart Grid, Vol 5, No2, pg 982 – 991. Figure 1

A network model for the real-time communications of a smart grid prototype

Within a large-scale distributed (or centralized) smart grid, the communication network is designed to connect multiple power management systems and collect data from hundreds or thousands of power sensors over a large geographical area. Due to the ripple effect of inconsistent communication delays, the network performance becomes a major concern to support power system applications. For example, in a large NSF project Future Renewable Electric Energy Delivery and Management (FREEDM), we implement a smart grid prototype, called the FREEDM Hardware-in-the-loop (HIL) testbed. The Distributed Grid Intelligences (DGIs) in the prototype can group specific peers to exchange the power among the power demands and supplies. But the grouping sometimes is not successful due to the inconsistent delays. In this paper, we present a queueing model to describe the performance of the grouping network that supports the communications among the DGIs in our smart grid prototype. First, we develop a queueing model to describe the communication traffic among the DGIs in the network with different topologies. Second, based on the network model, we analyze the delay performance and illustrate that the model can be used to predict the grouping delays. Third, we have collected extensive experimental data which is used to demonstrate the accuracy of the model. Finally, we have implemented the HIL testbed with the capabilities of integrated real-time communication and power exchange. The network model is used to investigate the influence of the communication inconsistency on the total cycle time of power operations so that new grouping protocols can be designed in the future.

A Layered Fault Tree Model for Reliability Evaluation of Smart Grids

The smart grid concept has emerged as a result of the requirement for renewable energy resources and application of new techniques. It is proposed as a practical future form of power distribution system. Evaluating the reliability of smart grids is of great importance and significance. Focusing on the perspective of the consumers, this paper proposes a layered fault tree model to distinguish and separate two different smart grid power supply modes. Revised importance measures for the components in the fault tree are presented considering load priority, aiming to find the weak parts of the system and to improve the design and using. A corresponding hierarchical Monte Carlo simulation procedure for reliability evaluation is proposed based on the layered fault tree model. The method proposed in this paper is tested on a case of reliability assessment for the Future Renewable Electric Energy Delivery and Management (FREEDM) system. The proposed technique can be applicable to other forms of smart grids.

A Novel Hierarchical Section Protection Based on the Solid State Transformer for the Future Renewable Electric Energy Delivery and Management (FREEDM) System

The effectiveness of a protection scheme in any power grid is essential to the reliability of the supply. One of the main goals of the FREEDM systems is to increase supply reliability to end users. However, traditional protection methods, including over current, sequential components, and wide differential area protection, are not suitable for this system for several reasons that will be explained in the paper. A new protection strategy is presented in this paper. This protection scheme takes advantage not only of the system configuration but mostly of the solid state transformer capability and design to minimize any circuit and communication that are needed for a successful protection strategy. A real time digital simulator (RTDS) is used to model a sample FREEDM system in order to verify the proposed protection scheme. Hardware-in-the-loop (HIL) testing was performed to verify the proposed protection scheme.

An Empirical Study of Communication Infrastructures Towards the Smart Grid: Design, Implementation, and Evaluation

The smart grid features ubiquitous interconnections of power equipments to enable two-way flows of electricity and information for various intelligent power management applications, such as accurate relay protection and timely demand response. To fulfill such pervasive equipment interconnects, a full-fledged communication infrastructure is of great importance in the smart grid. There have been extensive works on disparate layouts of communication infrastructures in the smart grid by surveying feasible wired or wireless communication technologies, such as power line communications and cellular networks. Nevertheless, towards an operable, cost-efficient and backward-compatible communication solution, more comprehensive and practical understandings are still urgently needed regarding communication requirements, applicable protocols, and system performance. Through such comprehensive understandings, we are prone to answer a fundamental question, how to design, implement and integrate communication infrastructures with power systems. In this paper, we address this issue in a case study of a smart grid demonstration project, the Future Renewable Electric Energy Delivery and Management (FREEDM) systems. By investigating communication scenarios, we first clarify communication requirements implied in FREEDM use cases. Then, we adopt a predominant protocol framework, Distributed Network Protocol 3.0 over TCP/IP (DNP3 over TCP/IP), to practically establish connections between electric devices for data exchanges in a small-scale FREEDM system setting, Green Hub. Within the real-setting testbed, we measure the message delivery performance of the DNP3-based communication infrastructure. Our results reveal that diverse timing requirements of message deliveries are arguably primary concerns in a way that dominates viabilities of protocols or schemes in the communication infrastructure of the smart grid. Accordingly, although DNP3 over TCP/IP is widely considered as a smart grid communication solution, it cannot satisfy communication requirements in some time-critical scenarios, such as relay protections, which claim a further optimization on the protocol efficiency of DNP3.

A High-Efficiency PV Module-Integrated DC/DC Converter for PV Energy Harvest in FREEDM Systems

The future renewable electric energy delivery and management (FREEDM) system provides a dc interface for alternative energy sources. As a result, photovoltaic (PV) energy can be easily delivered through a dc/dc converter to the FREEDM system's dc bus. The module-integrated converter (MIC) topology is a good candidate for a PV converter designed to work with the FREEDM system. This paper compares the parallel connected dc MIC structure with its counterpart, the series connected MIC architecture. From the presented analysis, the parallel connected architecture was shown to have more advantages. In this paper, a high-efficiency dual mode resonant converter topology is proposed for parallel connected dc MICs. This new resonant converter topology can change resonant modes adaptively depending on the panel operation conditions. The converter achieves zero-voltage switching for primary-side switches and zero-current switching for secondary-side diodes for both resonant modes. The circulation energy is minimized particularly for 5-50% of the rated power level. Thus, the converter can maintain a high efficiency for a wide input range at different output power levels. This study explains the operation principle of the proposed converter and presents a dc gain analysis based on the fundamental harmonic analysis method. A 240-W prototype with an embedded maximum power point tracking controller was built to evaluate the performance of the proposed converter. The prototype's maximum efficiency reaches 96.5% and an efficiency increase of more than 10% under light load conditions is shown when compared with a conventional LLC resonant converter.