Transient-based fault identification algorithm using parametric models for meshed HVDC grids

Transmission Line Fault Detection and Identification in an Interconnected Power Network using Phasor Measurement Units

The protection of meshed HVDC grids requires the fast identification of faults affecting the transmission lines. Communication-based methods are thus not suited due to the transmission delays. Many approaches involving a model of the transient behavior of the faulty line have recently been proposed. Nevertheless, an accurate description of the traveling wave phenomenon in multi-conductor lines such as overhead lines requires complex computations ill-suited for fast fault identification. This paper presents a single-ended fault identification algorithm using a closed-form parametric model of the fault transient behavior. The model combines physical and behavioral parts and depends explicitly on the parameters that characterize the fault, namely the fault distance and impedance. When a fault is suspected, the fault parameters are estimated so that the model fits best the received measurements. The confidence region of the estimated fault parameters is used to decide whether the protected line is actually faulty or not. The proposed algorithm is tested on a 4 station grid simulated with EMTP-RV software. The method is able to identify the faulty line using a measurement window of less than 0.5 ms. This allows ultra-fast fault clearing and can hence improve the overall reliability of future HVDC grids.

Detection and isolation of faulty line in an active distribution network using intelligent numerical relay

With an increasing number of power electronics connected renewable energy sources, electromagnetic transient (EMT) simulations become increasingly important to accurately simulate the behavior of electric power grids. EMT simulations are computationally expensive, and often specialized hardware, such as Real-Time Digital Simulators (RTDS), are used to run simulations in real-time. As individual simulators are limited in their computational capabilities, they can be interconnected in order to fully leverage their potential and enable more complex simulations. However, since these simulators are expensive and often located near power hardware for hardware-in-the-loop simulation, they are regularly distributed across multiple locations of different research institutions or organizations. The main contribution of this paper is the assessment of different approaches to connect multiple RTDS systems to form a locally distributed simulation infrastructure. For this, we combine a realistic and comprehensive model of a campus grid with a microgrid model to investigate the benefits and limitations of the different connection approaches.

An automatic grid partitioning technique of large grids based on CloudPSS

Electromagnetic transient (EMT) simulation is one of the routine tasks being executed in modern power systems. Typically, the most common EMT simulation method is the trapezoidal integration method, however, sustained numerical oscillations are possible to appear using this method, for instance, getting the voltage waveform across an inductance during a sudden current interruption. Two-stage diagonally implicit Runge-Kutta (2S-DIRK) method is a L-stable numerical method, which is able to avoid numerical oscillation. The 2S-DIRK method has been applied to solve simple RLC circuit simulations, in this paper, it is extended to system level EMT simulations considering the electromagnetic transient characteristics and nonlinearity for generators, transformers and loads. Case studies are performed to verify the effectiveness of the 2S-DIRK method in power system level EMT simulation, by comparing the accuracy and numerical stability with traditional methods.

In this paper a smart remote sensing prototype for fault detection and identification of photovoltaic arrays is presented. A simple fault detection and identification algorithm has been incorporated into the designed prototype. The designed system detect automatically the fault, and then identify the origin of some investigated faults (such as open circuit, short circuit, dust accumulation and shedding effect). The prototype has been tested experimentally at the Renewable Energy Laboratory of Jijel University, Algeria. The experimental results showed the capability of the prototype to remote sensing, detecting and faults identification. The status of the system can be checked online via a website using Internet of Things (IoT) and the user could be also notified by a SMS.

This study presents a method to interface an electromagnetic transient (EMT) simulator with a dynamic phasor (DP) simulation program. The hybrid DP–EMT simulator offers flexibility in deciding the harmonic contents to be preserved in the DP domain; additionally, it offers significant reduction in computing time of large networks compared with EMT simulation. The proposed interfacing method is based on a generic transmission line, which uses specialised numerical techniques to transfer discretised waveform samples between the two simulators. These numerical methods produce the required mapping between EMT simulation samples and their counterpart DPs. This study describes the mathematical foundations of the DP–EMT interface and demonstrates them using an illustrative example. Several large networks are then studied to assess the interface's accuracy and performance in reducing computing time.

Shifted-frequency based electromagnetic transient simulation for power system dynamics using two-stage singly diagonally implicit Runge–Kutta method

Parallel-in-time methods are emerging to accelerate the solution of time-consuming problems in different research fields. However, the complexity of power system component models brings challenges to realize the parallel-in-time power system electromagnetic transient (EMT) simulation, including the traveling wave transmission lines. This paper proposes a system-level parallel-in-time EMT simulation method based on traditional nodal analysis and the Parareal algorithm. A new interpretation scheme is proposed to solve the transmission line convergence problem. To integrate different kinds of traditional EMT models, a component-based EMT system solver architecture is proposed to address the increasing model complexity. An object-oriented C++ implementation is proposed to realize the parallel-in-time Parareal algorithm based on the proposed architecture. The results on the IEEE-118 test system show 2.30x speedup compared to the sequential algorithm under the same accuracy with 6 CPU threads, and a high parallel efficiency around 40%. The performance comparison of various IEEE test cases shows that the system's time-domain characteristics determine the speed-up of Parareal algorithm, and the delays in transmission lines significantly affect the performance of parallel-in-time power system EMT simulations.

As more generators and loads are integrated by power electronic converters with complicated controls, electromagnetic transients (EMTs) simulation becomes an important tool for studying dynamic characteristics of large‐scale power systems. To accelerate system‐level EMT simulations, a fine‐grained parallel algorithm on graphics processing units (GPU) is proposed. By decomposing the computational models of the EMT simulation into heterogeneous, homogeneous and network solution computations, the simulations are mapped into three unified GPU kernels. To incorporate control signals and non‐linear features of electrical components, heterogeneous computations are formulated as layered direct acyclic graphs (LDAG) of primitive operations. An LDAG kernel is designed to carry out theses primitive operations efficiently by grouped threads. Then, homogeneous computations for state updates of electrical components are modelled as sets of fused multiply‐add (FMA) operations, which are concurrently processed by an FMA kernel. Moreover, a hybrid network solution kernel is designed to solve the network equations, which can adaptively select dense or sparse solvers. Large‐scale test systems are created and simulated on an NVIDIA K20x GPU. The results show that the proposed GPU‐based EMT simulations are accurate and achieve 10x speedups over the CPU‐based ones.

High Voltage Direct Current (HVDC) systems are increasingly popular in electric power grids. Control system of such devices can cause instabilities when interacting with other equipment in a power system. Depending on the control system dynamics, instability and resonance can occur in a wide range of frequencies (up to few kHz). Low and high frequency resonances have been registered in several power electronics based project. In this article, several realistic test cases where oscillations can occur between HVDC links and power system components are illustrated using electromagnetic transient (EMT) simulations. In order to analysis and identify the cause of such instabilities, this paper illustrates how to conduct a frequency domain analysis by means of EMT time domain simulation. As EMT-type models provided by the manufacturers are often inaccessible (or black-boxed), the method presented considers black-boxed HVDC link model.

Much research has been devoted to system-level diagnosis. Two issues have been addressed. The first of these is diagnosability. The second is the design of fault identification algorithms. This paper focuses on the second of these concerns. This paper investigates the process of fault identification itself, introduces a new formal approach, and proposes a fault identification algorithm which runs in O(n/sup 2//spl radic//spl tau///spl radic/log n), /spl tau/<n/2.

A Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) are the most efficient and reliable method for electrical power transmission and implementation of HVDC grids over long distances. Generally, a meshed HVDC transmission grid has major problems such as protection against dc faults and to manage the power flows between the lines. As Current Flow Controllers (CFCs) will be required to balance line currents between nodes in meshed-HVDC grids. Hybrid circuit breaker with forced commutation can interrupt the fault current and thus protect grids of HVDC from dc faults but the fault clearing time for the available dc breakers are not fast enough and reliable to provide adequate protection for dc faults on multi-terminal networks. In order to overcome these problems CFCs is interline with hybrid dc circuit breaker. So, CFC will be interline with Pro-active Hybrid DC-Circuit Breaker (PHCB) by suffling the switches orientation within the Load Commutation Switch (LCS). The CFC design and its control performance will be verified by MATLAB Simulink. The two cases are studied which include, an integrated system consisting of CFC with Circuit Breakers (CBs) and the separate design that includes CFC and CB separately that are compared and thus power losses can be reduced.

This paper presents a multiple time-step solver based on a time-domain explicit integration algorithm for improving the computational speed of high-voltage transmission line electromagnetic transient (EMT) simulation. For weakly rigid EMT models of high-voltage transmission lines, the previous precise Runge-Kutta integration method with a small time step is adopted; for strongly rigid nonlinear EMT models of high-voltage transmission lines, a an improved precise integration method using a large time step is used for the solver of EMT simulation. Practical simulations for overvoltages of high-voltage transmission line show that multiple time-step EMT solver can be applied to different cases of EMT simulation for transmission line.