Bus Microgrid System Research Articles

A novel high impedance fault detection in the micro-grid system by the summation of accumulated difference of residual voltage method and fault event classification using discrete wavelet transforms and a decision tree approach

Conventional overcurrent protective relay is unable to detect high impedance faults (HIFs) in the micro-grid system owing to the reduced levels of fault magnitude. In this paper, numerous fault detection methods are discussed for developing a technique to identify HIFs, and also three steps approach of summation of accumulated difference of residual voltage, discrete wavelet transform (DWT), and decision tree(DT) approach has been used to detect and classify the fault. It also differentiates the faulty events from the various non-faulty ones such as switching of generators, capacitors, loads, etc. The residual voltage is used for the extraction of wavelet coefficients by DWT and fed to a DT classifier for fault event classification and confusion matrix created to view the accuracy. After classification, the predicted fault and the actual fault are obtained subsequently by training the data is 99.5% true positive rate and 0.5% false-negative rate. Similarly, this approach is also applied for faulty zone and non-faulty zone classification. The accuracy of the technique is analyzed with other classifiers like support vector machine(SVM), k-nearest neighbor(KNN), and ensemble classifiers. The DT classifier yields more accurate results compared to other classifiers. The proposed method performance is further evaluated by taking different performance indicators such as precision, recall, and F-measure. The proposed technique gives an overall accuracy of 99.95%, precision index of 100%, recall index of 99.9%, and F-measure index of 99.94% as compared to other classifiers under normal operation. The proposed method is also validated with unbalanced loading, varying DG parameters, varying distribution line length, and the addition of noise in the signal. To implement and demonstrate this method, a 5 bus micro-grid system integrated with a wind turbine-based system(WTS) generator is simulated using Power System Computer-Aided Design (PSCAD) software.

Ranking Load in Microgrid System Based on the Priority Weight Calculation of Power Supply

This paper proposes a method of ranking load in Microgird system based on the calculation of priority weights on the continuity of power supply of the loads. The proposed method applies the covariance matrix of the criterion layer to determine values of each criterion. The fuzzy preference relation matrix is used to replace the pairwise comparison matrix of the scheme layer. The weight of the criterion layer and the scheme layer are combined to get the final weights of each load bus. This solves the problem of consistency factor when evaluating loads from experts and Microgrid system operators. The calculation of priority weighting on the continuity of power supply for loads supports system operators to be proactive in planning load shedding or load shedding due to system failures, thereby minimizing damage to the system and electricity customers. The proposed method is calculated on the diagram of the IEEE 16 bus Microgrid system with six sources and eight loads.

A novel three-phase unbalanced power flow solution for islanded microgrids with distributed generations under droop controls

With the increasing penetration rate of distributed generations (DGs) in the distribution network, microgrids are widely applied for the benefits of efficiency and flexibility. The demands of power flow analysis for microgrids are increasing. However, the traditional power flow algorithms cannot be utilized directly when microgrids operate in islanded modes and the DGs are adjusted by a droop control scheme. To increase the effectiveness and generalization of the power flow, a novel two-layer iteration method for microgrids is proposed. First, the three-phase unbalanced power flow is calculated by the power-injection algorithm in the inner iteration. Then, the node admittance matrix of the transmission line, the loads, the power generations and voltage of DGs are updated directly through the power flow results in the outer iteration. Finally, the processes of calculating convergence solutions with inner and outer iterations are presented. The proposed method was implemented on the CloudPSS platform and tested with a modified IEEE-13 bus microgrid system. The power flow results of the proposed method are compared with the electromagnetic transient (EMT) simulation. The comparison results demonstrate the practicability and effectiveness of the proposed algorithm.

Fuzzy Logic Controlled Four Bus Micro-grid system employing Hybrid Power Flow Controller

Fuzzy Logic Controlled Four Bus Micro-grid system employing Hybrid Power Flow Controller

S-Transform Based Kurtosis Analysis for Detection of LG and LL Faults in 14 Bus Microgrid System

Low currents and voltage levels in a microgrid system make the fault detection by the conventional methods, very difficult. Due to ground faults voltage level drops to a very low level and thus, it becomes even more difficult to detect in case of a microgrid system. In this paper, a method of fault location identification and discrimination of fault type has been proposed. IEEE standard 14 bus microgrid system has been considered for this purpose. Faults are made to occur in two specific load buses and the outgoing currents of two generator buses were analysed in different conditions. S-Transformation is performed on the generator bus outgoing currents and kurtosis of the S-Transformation matrices has been calculated. An algorithm has been proposed for the detection of fault type and location. It has also been verified with different unknown cases. The simulation is carried out on the IEEE standard 14 bus system using MATLAB. The method presented here may be useful for the design of better protection schemes for such systems.

An Enhancement of Protection Strategy for Distribution Network Using the Communication Protocols

One of the main challenges to design a proper protection scheme for a microgrid is the dynamic characteristics in the architecture for the microgrid. The relay settings need to change with every configuration in the system to properly isolate a fault. This article proposes a centralized control approach using a cosimulation platform to monitor operational modes and multiple microgrid topologies to find fault and clear them optimally. The simulation software, embedded microcontrollers, and a real communication architecture are collectively used to perform the protection scheme platform. The data distribution service middleware is used to link between the hardware and software environments. The proposed technique helps to identify the shortest path from the source to the fault location. The proposed main control center is responsible for adjusting the relay settings based on the active topology and the shortest path to the fault. This technique is investigated on IEEE 14 bus microgrid system for all the possible fault paths. The proposed scheme can clear the fault by isolating the minimum part of the system and improving the endurance of the power to supply the different loads in the system.

Harmonic filter‐based improved islanding detection technique for microgrid

Islanding detection in microgrid using harmonic filters connected at the distributed generation units (DGs) end has been described. Traditional islanding techniques related to impedance estimation suffer from poor detection accuracy due to false detection during load switching. In the proposed method, tuned filters connected at DG terminals are utilised for islanding detection in the microgrid. These filters can be connected at the DG end to reduce harmonic injection to the source end, besides helping the islanding detection through the proposed technique. The measured grid-side harmonic impedances at tuned frequency after the filter are used for islanding detection instead of the direct input harmonic impedance calculated in traditional techniques. The proposed method can overcome the difficulties of the existing impedance-based islanding detection techniques like larger non-detection zone (NDZ), false detection during load switching etc. The effectiveness of the proposed method is tested in a six bus microgrid system and comparison with other existing islanding detection techniques reveals the fact that the proposed method has much better performance in terms of improved detection accuracy, detection speed, and it also significantly reduces the NDZ.

A Design and Optimization Tool for Inverter-Based Microgrids Using Large-Signal Nonlinear Analysis

In this paper, large-signal Lyapunov-based stability analysis is performed on an inverter-based microgrid. Most microgrid stability studies have been based on small-signal stability by using linearization techniques. This paper produces the large-signal nonlinear mathematical model of an inverter-based microgrid. The inverter models include the dc-side circuits associated with dc sources. The mathematical model is then used to estimated the domain of asymptotic stability of the microgrid. A three bus microgrid system is used as a case study to highlight the design and optimization capability of such an approach. This paper explores the effect of system component sizing, load transient, and dc-side voltage source variations on the asymptotic stability of the ac microgrid. Thus, this approach quantifies the effect of dc-side variations on the transient stability of the ac-side microgrid. Time domain simulations were used to illustrate the mathematical nonlinear analysis results.

Enabling and Evaluation of Inertial Control for PMSG-WTG Using Synchronverter With Multiple Virtual Rotating Masses in Microgrid

With the ever-increasing penetration level of renewable energy generation units and the replacement of traditional synchronous generators, the issues associated with the deteriorated performance of power system frequency regulation and potential grid frequency instability become more significant. In this paper, the inertial control algorithm using a synchronverter is enabled for variable-speed wind turbines. Besides, the type-4 permanent magnet synchronous generator wind turbine generator using synchronverter inertial control is modeled and the comprehensive analysis and comparison are conducted between frequency-based inertial control and synchronverter inertial controls. Aiming to address the compromised ability of a synchronverter with desirable inertial response to deal with fast changing wind condition, a synchronverter with multiple virtual rotating masses is proposed in order to improve the active power tracking performance as well as to boost inertial control of the synchronverter. The performance of inertial controls is verified in the modified 10MVA IEEE 14 bus microgrid system. The assessment of the simulation results provides a deep insight into different inertial control methods while demonstrating the applicability of synchronverter on wind power generation systems.

Artificial Neural Network Based Fault Detection and Fault Location in the DC Microgrid

Abstract In DC microgrid, power electronic devices may suffer from over current during short circuit faults. Since DC bus systems cannot sustain high fault currents, suitable protection strategy in DC lines is indispensable. This paper presents a novel use of artificial neural network (ANN) for fault detection and fault location in a low voltage DC bus microgrid system. In the proposed scheme, the faults on DC bus can be fast detected and then isolated without de-energizing the entire system, hence achieving a more reliable DC microgrid. The neural network is trained based on the different short circuit faults in DC bus to ensure its validity. A microgrid with ring DC bus, which is segmented into overlapping nodes and linked with circuit breakers, is built in PSCAD/EMTDC to test the performance of the protection scheme.

English

English

DC Ring-Bus Microgrid Fault Protection and Identification of Fault Location

A fault protection and location method for a dc bus microgrid system is presented in this paper. Unlike traditional ac systems, dc bus systems cannot survive or sustain high-magnitude fault currents. And if a fault causes the dc bus to de-energize completely, it makes locating faults very difficult. The main goal of the proposed scheme is to detect and isolate faults in the dc bus without de-energizing the entire system and identifying the fault location. In order to achieve this, a ring-type bus was used in this paper. The bus was segmented into overlapping nodes and links with circuit breakers (CBs) to isolate the segment in the event of a fault. Backup protection is implemented for circuit breaker failures to improve system reliability. A noniterative fault-location technique using a probe power is also presented in this paper. This probe power can also be used for a pilot test before main CB reclosing to avoid system issues that can be expected when the reclosing fails due to a permanent fault. The proposed algorithm can be implemented and executed by an intelligent electrical device for individual node. The proposed concepts have been verified with computer simulations and hardware experiments.