Fault Disturbance Research Articles

Fault Impact Analysis and Improvements for a Large-scale Offshore Wind Farm Connected to Grid by Long HVAC Cables

A large-scale offshore wind power system with a capacity 200MW will be erected in the Peng-Hu islands, located about 60 km off the west coast of Taiwan. The system will be connected to Taiwan’s main grid by long high-voltage alternating-current (HVAC) submarine cables. The system impact of three phase short circuit faults are analyzed based on PSS/E simulations of type-B, C and D turbines. The system framework, associated parameters, and the features of different types of wind turbines are described. Responses of voltages, frequencies and powers of each turbine type due to fault disturbance are analyzed. In addition, the voltage and frequency variations of the Taiwan and Peng-Hu grids are compared in terms of different turbine types. Finally, improvements based on static VAr compensator (SVC) and static synchronous compensator (STATCOM) technologies are presented and their fault impact mitigation capacities are analyzed. Analysis results show that fault impact is significantly dependent on turbine type and the presented compensators provide useful impact mitigation.

Disturbance attenuation observer design for fuzzy time-delay system with fault1

The T-S fuzzy system with disturbance and fault is considered in the paper, and an observer with disturbance attenuation and fault detection is designed. With the linear matrix inequalities method, a sufficient condition on the existence of the observer with disturbance attenuation is provided, and a sufficient condition on the existence of the observer with fault detection is given, the two performance indices are then combined, and an optimization problem is formulated to solve the two problems simultaneously. A numerical example is given to show the effectiveness of the proposed method.

Mechanisms influencing the lateral roof roadway deformation by mining-induced fault population activation: a case study

Mining-induced fault population activation often leads to dynamic disasters. It is of considerable significance to understand the strata movement and mining-induced stress evolution induced by fault population activation. This paper studied the movement and rotation of the roof strata which are influenced by a complex interaction between two faults in its strike direction of panel 31100 of no. 1 mine in Pingdingshan, China. Protective coal pillars for the lateral roof roadway were designed to be wide enough in case of eliminating fault disturbance. Severe roadway deformation was also observed throughout advancing. Based on the deformation observation of roadways, a structural instability model of considering the fault population was established. Moreover, mining-induced stress distribution and lateral roof roadway deformation mechanisms during fault population activation were investigated by both theoretical analysis and 3D numerical simulations. According to the mining-induced stress distribution, the sliding instability of roof strata above the working face aggravated the structural rotation of the lateral strata. Intense stress concentration induced by lateral roof rotation resulted in lateral roof roadway deformation. As concerning the effect of fault population activation, results obtained are of great importance for reasonable allocation of working face and roadways, and also for the prevention of dynamic disasters. [Received: February 5, 2015; Accepted: July 20, 2015]

Fault detection for singular switched linear systems with multiple time-varying delay in finite frequency domain

ABSTRACTThis paper deals with the problem of the fault detection (FD) for continuous-time singular switched linear systems with multiple time-varying delay. In this paper, the actuator fault is considered. Besides, the systems faults and unknown disturbances are assumed in known frequency domains. Some finite frequency performance indices are initially introduced to design the switched FD filters which ensure that the filtering augmented systems under switching signal with average dwell time are exponentially admissible and guarantee the fault input sensitivity and disturbance robustness. By developing generalised Kalman–Yakubovic–Popov lemma and using Parseval's theorem and Fourier transform, finite frequency delay-dependent sufficient conditions for the existence of such a filter which can guarantee the finite-frequency H− and H∞ performance are derived and formulated in terms of linear matrix inequalities. Four examples are provided to illustrate the effectiveness of the proposed finite frequency method.

A sliding-mode voltage regulator for salient pole synchronous generator

This paper presents a sliding-mode control strategy for voltage regulation of synchronous generators connected to the power grid that combines sliding mode and linear control laws. This hybrid control scheme contributes preventing system instability, by suppressing the low-frequency oscillations arising from power grid fault disturbances. In addition, this strategy does not require the estimation of system parameters. This control strategy was designed to be introduced easily in a conventional automatic voltage regulator (AVR) algorithm. Experimental results obtained with a laboratory test set-up, consisting of the synchronous generator connected to the grid and subjected to severe power transients, was employed to validate the proposed control approach. Comparisons with a conventional as well as with two hybrid control schemes demonstrate the advantages of the proposed control strategy.

Performance Tradeoffs for Networked Jump Observer-Based Fault Diagnosis

In this paper, we address the fault diagnosis problem for discrete-time multi-sensor systems over communication networks with measurement dropouts. We use the measurement outcomes to model the measurement reception scenarios. Based on this, we propose the use of a jump observer to diagnose multiple faults. We model the faults as slow time-varying signals and introduce this dynamic in the observer to estimate the faults and to generate a residual. The fault detection is assured by comparing the residual signal with a prescribed threshold. We design the jump observer, the residual and the threshold to attain disturbance attenuation, fault tracking and detection conditions and a given false alarm rate. The false alarm rate is upper bounded by means of Markov’s inequality. We explore the tradeoffs between the minimum detectable faults, the false alarm rate and the response time to faults of the fault diagnoser. By imposing the disturbances and measurement noises to be Gaussian, we tighten the false alarm rate bound which improves the time needed to detect a fault. A numerical example is provided to illustrate the effectiveness of the theory developed in the paper.

Multiobject Holographic Feedback Control of Differential Algebraic System with Application to Power System

A multiobject holographic feedback (MOHF) control method for studying the nonlinear differential algebraic (NDA) system is proposed. In this method, the nonlinear control law is designed in a homeomorphous linear space by means of constructing the multiobject equations (MOEq) which is in accord with Brunovsky normal form. The objective functions of MOEq are considered to be the errors between the output functions and their references. The relative degree for algebraic system is defined that is key to connecting the nonlinear and the linear control laws. Pole assignment method is addressed for the stability domain of this MOHF control. Since there is no any approximation, the MOHF control is effective in governing the dynamic performance stably both to the small and major disturbance. The application in single machine infinite system (SMIS) shows that this approach is effective in the improvement of stable and transient stability for power system on the disturbance of active power or three-phase short circuit fault.

Testing Disturbance Faults in Various NAND Flash Memories

NAND flash memory is one popular non-volatile memory. Flash memory is prone to disturbance faults due to its specific mechanism of functional operations. Furthermore, different NAND flash memories might be different on the array organizations and the supported functional operations. For example, some NAND flash memories can support the random program operation, but some cannot; some NAND flash memories with single-page wordlines and some with multiple-page wordlines. The differences on the array organizations and the functional operations result in the heavy influence on the testing of disturbance faults. In this paper, therefore, we analyze the disturbance faults for NAND flash memories with different array organizations and functional operations. Also, test algorithms for covering the disturbance faults in various types of NAND flash memories are proposed.

A Fault Detection Method Based on Feedforward Compensation in Mechatronic Control System

For the fault detection of mechatronic control system, based on observer a feedforward compensation approach was presented. The model of a mechatronic control system was investigated and divided into two loops for disturbance compensation and fault detection. The external disturbance of the vehicle was analyzed, and the relationship between the support shaft friction moment as main disturbance element and the attitude effect of the vehicle was built by the way of data curve fitting. The adjustment coefficients were proposed respectively in nine kinds of running section of the vehicle, because disturbance was very complicated and time-variant in different section. Fault detection observer was designed to generate residuals in the inner loop, and the whole residual was calculated. The compensation was deduced in accordance with responses produced by the disturbance, so the disturbance could be compensated. Band filter was proposed for other noises. Finally, an example was presented to illustrate the proposed approach. The simulation results showed that the disturbance elements can be compensated rapidly.

On-Line Handwriting Recognition Based on Hopfield Neural Network

In this paper, Discrete Hopfield Neural Network (DHNN) is adopted to realize handwritten characters recognition. First, learning samples are preprocessed including binarization, normalization and interpolation. Then pixel features are extracted and used to establish DHNN. The handwritten test samples and noise corrupted samples are finally inputted into the network to verify its recognition performance. Simulation results reveal that DHNN has good fault tolerance and disturbance rejection performance. In addition, the recognition system is realized with MATLAB neural network toolbox and GUI, which verifies the feasibility of the algorithm.

Machine Condition Monitoring Software Agent Using JADE and Data Mining

In recent days there is a huge demand to increase the production of any mechanical components without any disturbance or mechanical faults in the machine. Therefore, to increase the productivity, it is necessary to monitor the running machine at regular intervals. To overcome such difficulties, a new machine condition monitoring software is designed using the multi agent software. This software is designed using the JADE framework and the data are analyzed using free open source Weka explorer for statistical calculations.

Coordinated Control of Variable-Speed Constant-Frequency Wind Farms in Weak Grids

Variable-speed constant-frequency (VSCF) wind farms are gradually becoming a significant proportion of generation in weak grids with constantly increasing penetration rate, and it should certainly take responsibility of the grid frequency and voltage stability. Based on the P-Q performance curve of doubly fed induction generator (DFIG), by introducing static synchronous compensator (STATCOM), this paper presents a coordinated control strategy of active power and reactive power to deal with fault and load disturbance in weak grids. Simulation results show that the proposed coordinated control strategy can effectively improve the frequency and voltage stability of the grids.

Modeling and Simulation of DIGSILENT-based Micro-grid system

The accurate modeling of micro-grid access to power system planning and design stage needs is the primary problem to solve. This paper modeled the micro grid photovoltaic power generation system ,including silicon solar cell, photovoltaic inverters, battery energy storage system, and the micro power distribution system .The use of power system analysis software (DIGSILENT) of actual power system simulation, the simulation results verify the model's correctness. In the power grid fault disturbance, the light intensity of disturbance and the load disturbances, the simulation results show that the optical storage combined with micro network has fast dynamic response characteristics, and its network of grid-connected voltage influenced by the changes of the light and load is little, while more affected by the network fault influence. DOI : http://dx.doi.org/10.11591/telkomnika.v12i6.5471

Fault-relevant Principal Component Analysis (FPCA) method for multivariate statistical modeling and process monitoring

For industrial processes, there are always some specific faults which are not easy to be detected by the conventional PCA algorithm since the monitoring models are defined based on the general distribution information of normal data which may not highlight the abnormal changes. For these specific faults, if fault data are available and used for model development, more meaningful directions may be extracted for monitoring which can improve fault detection sensitivity. In the present work, a fault-relevant principal component analysis (FPCA) algorithm is proposed for statistical modeling and process monitoring by using both normal and fault data. The key is how to extract and supervise the fault-influential data distribution directions. By analyzing the relative changes from normal to fault with available fault data, the new model structure further decomposes the original PCA systematic subspace and residual subspace into two parts respectively. The part that will present larger variation relative to the normal case under the disturbance of fault is regarded to be more informative for fault detection (called fault-relevant part here). It is then separated from the fault-irrelevant part and highlighted for online monitoring which is deemed to be more effective for fault detection. The proposed method provides a detailed insight into the decomposition of the original normal process information from the fault-relevant perspective. Its sensitivity to fault detection is illustrated by data from a numerical example and the Tennessee Eastman process.

Effect of wind generation system types on Micro-Grid (MG) fault performance during both standalone and grid connected modes

Recently, there are three wind generation (WG) system types. The first type is called Fixed Speed Wind Generation (FSWG) system, which employs squirrel cage induction generators. Double Fed Induction Generator (DFIG) is utilized in the second type. The third type is called Full Converter Wind Generation (FCWG) system, which is interfaced with Micro-Grid (MG) through a back to back converter. During fault occurrence, each WG has its performance and characteristics which are determined by the generator physical characteristics and the MG earthing system configuration. For some WG types, the fault current depends also on the control algorithm of the power converter. The main target of this paper is to investigate and estimate how the fault performance of MG during both standalone and grid-connected modes is influenced by the type of WG. It is found during standalone mode that the type of the employed WG has a dominant impact on the MG performance under fault disturbance. On the contrary, the type of the employed WG has a negligible effect on the MG fault performance during grid-connected mode. This is because the main grid contributes most of the fault current. Effects of earthing system type on MG performance are highlighted.

Consensus Control for Variable Multi-Agent Systems with Faults and Disturbances

This paper investigates multi-agent consensus problem with an active leader as well as external disturbances and some faults. The undirected networks with variable interconnection topology are taken into consideration. Distributed consensus control algorithm is proposed to analyze the disturbance rejection and fault sensitivity problem arising in the coordination control of multi-agent networks. With a proposed control scheme, we then present sufficient conditions under which all agents can reach consensus with the desired performance index. Finally, simulation results are provided to demonstrate the effectiveness of our theoretical results.

Modeling and Simulation of Hydraulic Power System for Maintenance Training Simulator

Study of Hydraulic Power System for development of Maintenance Training Simulator is very important. By analyzing the operational principle of the hydraulic system, presents an aircraft hydraulic system functional simulation model. After the whole hydraulic model has been established, attach to the maintenance training simulation platform. Simulation results show that this model can simulate the normal system operation and indication, and can simulate the impacts of fault disturbances under various conditions, which meets the simulation demand.

Fault Ride through Capability Improvement of Wind Turbine Based DFIG Considering an Optimized Crowbar Along with STATCOM under Grid Fault Condition

Grid disturbances, especially grid faults, have very unfavorable effect on the performance of wind turbine based Doubly Fed Induction Generator (DFIG). In this study active and reactive powers control of DFIG with STATCOM has been carried out to improve Fault Ride Through (FRT) capability of a wind turbine. In order to excel improvement of the DFIG behavior under grid fault disturbances, an optimized crowbar protection method is also considered together with STATCOM. The optimized protection crowbar resistance is achieved through Analytical Hierarchy Process (AHP) algorithm. Simulations results illustrate that an optimized crowbar protection method along with STATCOM has improved the stability of wind farm and provide grid code requirement compared with that of methods without using the optimized crowbar resistance.

A Comparative Study on Frequency Estimation Methods

In this paper, a comparative study on the frequency estimation methods using IRDWT (Improved Recursive Discrete Wavelet Transform), FRDWT(Fast Recursive Discrete Wavelet Transform), and GCDFT(Gain Compensator Discrete Fourier Transform) is presented. The 345[kV] power system modeling data of the Republic of Korea by EMTP-RV is used to evaluate the performance of the proposed two kinds of RDWT(IRDWT and FRDWT) and GCDFT. The simulation results show that the frequency estimation technique based on FRDWT could be the optimal frequency measurement method, and thus can be applied to FDR(Fault Disturbance Recorder) for wide-area blackout protection or frequency measurement apparatus.

Antidisturbance Fault Tolerant Control of Attitude Control Systems for Microsatellite with Unknown Input Delay

The antidisturbance fault tolerant control problem of attitude control systems for microsatellite is investigated in the presence of unknown input delay, stuck faults from the reaction wheel and the multiple disturbances. The multiple disturbances are supposed to include the vibration disturbance torque from the reaction wheel and modeling uncertainties. The fault diagnosis observer and disturbance observer are constructed to estimate stuck faults and vibration disturbance torque from the reaction wheel, respectively. A composite fault tolerant controller is designed by combining a PID controller, the fault accommodation estimation based on the fault diagnosis observer, and the disturbance compensator based on the disturbance observer. The controller and observer gains can be easily obtained via a set of linear matrix inequalities. Simulation results are given to show that the faults can be accommodated readily, and the disturbances can be rejected and attenuated simultaneously.