Novel Pilot Directional Protection for the FREEDM Smart Grid System

abstract: The presence of distributed generation in high renewable energy penetration system increases the complexity for fault detection as the power flow is bidirectional. The conventional protection scheme is not sufficient for the bidirectional power flow system, hence a fast and accurate protection scheme needs to be developed. This thesis mainly deals with the design and validation of the protection system based on the Future Renewable Electric Energy Delivery and Management (FREEDM) system, which is a bidirectional power flow loop system. The Large-Scale System Simulation (LSSS) is a system level PSCAD model which is used to validate component models for different time-scale platforms to provide a virtual testing platform for the Future Renewable Electric Energy Delivery and Management (FREEDM) system. It is also used to validate the cases of power system protection, renewable energy integration and storage, and load profiles. The protection of the FREEDM system against any abnormal condition is one of the important tasks. Therefore, the pilot directional protection scheme based on wireless communication is used in this thesis. The use of wireless communication is extended to protect the large scale meshed distributed generation from any fault. The complete protection system consists of the main protection and the back-up protection which are both presented in the thesis. The validation of the protection system is performed on a radial system test bed using commercial relays at the ASU power laboratory, and on the RTDS platform (Real Time Digital Power System) in CAPS (Center for Advanced Power System) Florida. Considering that the commercial relays have limitations of high cost and communicating with fault isolation devices, a hardware prototype using the interface between the ADC (analog to digital converter) and MATLAB software is developed, which takes advantage of economic efficiency and communication compatibility. Part of this research work has been written into a conference paper which was presented by IEEE Green Tech Meeting, 2017.Dissertation/ThesisMasters Thesis Electrical Engineering 201

Demonstration of adaptive overcurrent protection using IEC 61850 communications

This paper contains a description of an adaptive protection scheme that has been implemented and demonstrated in a hardware in the loop simulation environment using commercially available protection hardware and IEC 61850 communications.The implementation is based on an actual 11kV system which includes distributed generation and network automation. IEC 61850 communications offers several benefits for the implementation of adaptive protection, but also presents some limitations which are discussed in the paper. An alternative approach to overcome a number of the limitations is also presented

Development of overcurrent relay model and power system simulator using National Instruments devices in real-time

One of the major objectives at Mississippi State University’s Power and Energy Research Laboratory (PERL) is to develop an adaptive protective controller for Shipboard Power System (SPS) protection. This thesis work focuses on developing an overcurrent relay model in LabVIEW software and validating the developed model by conducting Hardware-in-the-Loop (HIL) tests with Real-Time Digital Simulator (RTDS) and commercial Schweitzer Engineering Laboratories (SEL)-351S directional over-current relay. Simulation results show that the developed relay model is quite flexible, efficient and can be used in real-time. Modeling efforts to establish a HIL platform using National Instruments devices have been presented here. This thesis work also proposes a high-performance and low-cost National Instruments-PXI platform for power system simulations. Two-bus, eight-bus and shipboard power system (SPS) test cases are developed using Matlab/Simulink.Software-in-the-Loop (SIL) tests are conducted for these test cases with Matlab/Simulink overcurrent relay model for several fault conditions. To determine the performance of the NI-PXI system, open loop tests are done between the NI-PXI and the SEL-351S relay and these results are compared with the results of open loop test conducted between the RTDS and SEL-351S relay. HIL tests are done between the NI-PXI system and the dSPACE relay model. HIL tests are also done between the NI-PXI and the commercial SEL-351S relay. These results show that the NI-PXI controller can be used as a power system simulator

Out-of-step Protection Using Energy Equilibrium Criterion in the Time Domain

Disturbances in power systems are common and they result in electromechanical oscillations called power swing. The power swings could be severe and it may lead to loss of synchronism among the interconnected generators. This is referred to as out-of-step condition. The voltage and current swings during an out-of-step condition damage power system equipments and also cause unwanted operations of various protective devices. The protection systems require an effective algorithm for fast and accurate detection of out-of-step condition. This research is focused on the development of a simple and effective out-of-step relay capable of detecting out-of-step condition in a complex power system. To achieve this, the research has gone through four distinct stages: development of an algorithm, simulation, hardware implementation and its testing. An out-of-step algorithm is proposed based on equal area criterion in time domain. The equal area criterion in time domain is obtained by modifying the traditional equal area criterion in power angle domain. A single machine infinite bus system, a two machine infinite bus system and a three machine infinite bus system and a 17-bus multiple machines system are used as case studies and are modeled using simulation tool(PSCAD™). To test the effectiveness of the proposed algorithm, various out-of-step conditions are simulated by applying disturbances at various locations in the above chosen power system configurations. For hardware implementation and testing of the algorithm, a digital signal processing board (ADSP-BF533 from Analog Devices ™) is used. To test the performance of the developed digital relay in a closed loop, real time power system signals are necessary and therefore for this purpose, a Real Time Digital Simulator (RTDS™) available in the power research laboratory is used. The RTDS™ simulator mimics the actual power systems in real time. The signals required by the relays can be tapped from the RTDS™ and the signals coming from relay can be fed back into the RTDS™, which makes the closed loop testing of the digital relay possible. This research has yielded a simple out-of-step algorithm and unlike the other out-of-step detection techniques proposed in the literature does not need offline system studies to arrive at a solution.The developed digital out-of-step relay is capable of making decisions based only on the information available from its point of installation, thus it avoids the communication devices which is advantageous for the out-of-step protection of a complex power system. Finally, the simulation results show that the proposed algorithm can be applied to any power configurations and is faster compared to the conventional concentric rectangle schemes used in the literature

Design and Development of Protection Schemes for FREEDM Smart Grid Systems

abstract: This research work describes the design and validation of protection schemes developed to solve the problem of communication with an ability to detect and sectionalize the fault. Protection schemes have been designed according to the requirements of the Future Renewable Electric Energy Delivery and Management (FREEDM) system. Due to the presence of distributed generation (DG), power flow in the loop is bi-directional and conventional protection schemes may face the problem of unwanted tripping. Hence customized protection schemes have been developed specific to the FREEDM system. Former FREEDM students at ASU have developed ultrafast pilot differential protection using fast analog communication (Ethercat communication) and modified it in various ways to speed up the fault detecting capability of the algorithm. However, the National Science Foundation (NSF) criticized the use of Ethernet communication, as it is not compatible for long distances. FREEDM loop uses a fault current limiter (FCL) to limit the fault current and the substation solid state transformer (SST) reduces the system voltage to limit the fault current to 2 per unit. This allows the protection scheme to detect fault current in 2-3 cycles. However a much delayed fault detection is not encouraged as it will disrupt the power supply to healthy parts of the system for a longer duration. Time inverse directional overcurrent protection, pilot directional protection and PMU based protection are developed in this thesis work addressing the communication problem and at the same time with the ability to quickly detect the faults. Validation of the protection scheme is performed on the Real Time Digital Simulator (RTDS) at the Center for Advanced Power Systems (CAPS) using SEL relays and simulation models are developed in PSCAD.Dissertation/ThesisMasters Thesis Electrical Engineering 201

International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

Use of RTDS to investigate the role of digital substation data for realising integrated network operator functions

Modellizzazione di un tratto di linea reale con i simulatori RTDS, applicazione del modello per studi sulla rete quali distanza di guasto, flussi di potenza e campionamento dei dati

Improved faulted phase selection algorithm for distance protection under high penetration of renewable energies

The high penetration of renewable energies will affect the performance of present protection algorithms due to fault current injection from generators based on power electronics. This paper explains the process followed for analyzing this effect on distance protection and the development of a new algorithm that improves its performance in such a scenario. First of all, four commercial protection relays were tested before fault current contribution from photovoltaic system and full converter wind turbines using the hardware in the loop technique. The analysis of results obtained, jointly with a theoretical analysis based on commonly used protection strategy of superimposed quantities, lead to a conclusion about the cause of observed wrong behaviors of present protection algorithms under a high penetration of renewables. According to these conclusions, a new algorithm has been developed to improve the detection of faulted phase selection and directionality on distance protection under a short circuit current fed by renewable energy sources. © 2020 by the author

Coordination of Generator Protection and Control in the Over and Under Excited Regions

This thesis deals with the coordination of protection and control functions associated with the synchronous generators. The excitation control functions are a key component in maintaining the stability of machines and the network. The overall objective of coordination is simple; to allow excitation control functions, the automatic recovery from excursions beyond normal limits, and only take protective action as a last resort. This thesis focuses on four areas of generator control and protection : a) Loss of excitation protection, b) Dynamic underexcitation coordination, c) Dynamic Overexcitation coordination, and d) a generic protective relay development platform for hardware and software development. Loss of excitation (LOE) is a condition in the underexcited region that presents a risk of severe damage to a generator. The state of the art in the detection of a loss of excitation condition is based on the principle that, for a zero Thevenin voltage, the generator becomes a reactance as seen from the power system. The difficulty in detecting a loss of excitation is that several other disturbances may temporarily present a similar behavior, for instance a fault followed by a power swing. In this part of the work, a new algorithm for the detection of a loss of excitation condition is proposed by using the Support Vector Machine (SVM) classification method and a careful design of the necessary feature vectors. The proposed method is robust to changes in conditions including initial load, fault types, line impedance, as well as generator parameter inaccuracies. Coordination in the underexcited region presents difficulties due to the commonly used static characteristics instead of dynamic simulation. The underexcited limit presents an overload characteristic that is not normally known or used. Once the limit is exceeded, the limiting control action is a control loop that presents a dynamic behavior not typically represented in studies in the current industry practice. It is also important to properly model and include dynamic performance of protection functions. An important consideration not typically taken into account is the actual stability limit, which depends on the characteristics and the mode of excitation control used. This thesis includes all the above considerations necessary to achieve the required coordination using the more accurate dynamic simulations. Specific scenarios that present risk to the machine or the system are included to assess the coordination achieved. A real generator from the Alberta power system is used as a case study to demonstrate the proposed coordination methodology. Coordination in the overexcited region again presents practical difficulties due to static characteristics instead of dynamic simulation of conditions that exercise the overexcitation limits. The problems observed relate to coordination methodology and modeling methods for both protection and control limits. Once the limit boundary characteristic is exceeded, the limiting action is a control loop that presents dynamic behavior that needs to be represented. Similar considerations need to be made with the protection function protecting against rotor overload. Current modeling methods mostly use low bandwidth simulations, i.e., transient stability studies. A modeling methodology as well as specific model improvements to the IEEE ST1A excitation control model are proposed to achieve the required coordination. The ST1A type is one model that can represent a wide variety of system models from different manufacturers. The proposed modeling methodology applies to high bandwidth simulations such as electromagnetic simulations. Specific important scenarios, such as severe temporary reactive overload or severe power swing conditions, where the protection and control are required to coordinate but that present risk to the machine or the system are proposed as part of the coordination considerations. The detection of LOE conditions by the proposed SVM method and by traditional methods was implemented in hardware by using a digital signal processor (DSP) platform and tested using real time power system simulations. A new platform for real time protective relay development was designed and used for the purpose of implementation. In the proposed platform, a processor independent code is used so that development can be performed using native host computer development tools. By using the proposed platform-independent code, off line testing can be performed either interactively or in batch mode for evaluating multiple cases