Placement of power quality monitors using enhanced genetic algorithm and wavelet transform

This study deals with the stabilization of grid connected wind farms. Operation of wind turbines has an impact on the power quality and reliability at the connected electric network. Power quality problems such as voltage flicker and harmonic distortion along with reliability issues are some major concern and in this work the flicker & harmonics issues are considered. Wind turbine connected to an induction generator and synchronous generator is modeled using PSCAD software to analyze power quality and reliability problems. Due to continuously varying wind speed components, the active and reactive power along with terminal voltage fluctuates continuously. A new type of static synchronous compensator (STATCOM) unit is developed to inject reactive power by switching IGBT(s) to mitigate power quality problems and to get stable grid operation. By connecting proposed Electro-Mechanical Switched Capacitor (EMSC) based STATCOM into the grid, reactive power and terminal voltage can be controlled effectively with varying wind speed.

This paper introduces a novel automatic hybrid classifier to detect and classify the Power Quality(PQ) problems in power systems using Wavelet Packet Transform (WPT) and Artificial Neural Networks (ANN). Various PQ events like Normal, Sag, Swell and Interruptions are obtained by modeling three phase distribution system using MATLAB simulink. For classification, the selection of suitable features from the disturbance signal is extremely important. Recent literature survey deals with various signal processing techniques like Fast Fourier Transform (FFT), Discrete Wavelet Transform (DWT) and Wavelet Packet Transform (WPT) were used for feature extraction. From the above techniques, the main issues addressed are selection of optimal feature subset and the design of ANN architecture model. To build a competent and robust classifier, it is essential to extract the utilizable feature vectors from the disturbance signal that can optimize data size as well as incorporate the main characteristics of the signal. This paper addresses these issues, and the distinctive feature vectors are obtained with reduced number of coefficients by using Energy Entropy based WPT. From these, the best discriminative feature vectors with reduced number of coefficients are obtained and are used as input to ANN, so that the burden over classification can be reduced. The classification performance is compared with FFT based ANN. The simulation results obtained have significant improvement over existing methods. Thus the proposed hybrid classifier provides the most excellent detection among PQ problems that arises in real time by improving classification accuracy in terms of both computation time and means square error.

In order to guarantee the safe and economical run of the electrical power system and the security of equipments and users, the power quality problems should be monitored. The definition, cause and harm of power quality problems were introduced. The analysis principle and the compensation methods of voltage fluctuation and flicker, voltage sag, harmonic and three-phase imbalance were expatiated. The classification, the contrast and the summary of measure and analysis methods were presented. The direction and emphasis of studying of power quality problems are put forward.

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

Due to the growing use of sensitive equipment, the power quality (PQ) requirements are becoming much stricter. Many of the equipment malfunctions are due to various PQ problems. Before the mitigations of PQ problems are decided, a monitoring system should be setup to find out the causes of PQ problems. In this study a voltage quality monitoring system was setup in order to understand the power service quality and the seasonal changes of PQ indices of different feeders serving different types of customers. The recorded data are used to calculate different PQ parameters such as voltage sag indices, total harmonic distortion (THD), and voltage flicker.

Electric railway power systems (ERPS) as one of the most critical and high-power end-user loads of utility grids are characterized by outlandish power quality (PQ) problems all over the world. The extension and evolution of different supply topologies for these systems has resulted in significant and various forms of distortions in network voltage and current in all ERPS, the connected power system, and adjacent consumers. During the last years, numerous studies have been offered to investigate various aspects of PQs in a specific supplying topology. Variation in the supply structure of the ERPS and different types of locomotives has propelled the observation of different PQ phenomena. This versatility and development have led to confront considerable types of two-way interactive interfaces as well as reliability and PQ problems in ERPS. In addition, the lack of standards explicitly dedicated to ERPS has added to the ambiguity and complexity of this issue. In this paper, an extensive review of PQ distortions and phenomena in different configurations of ERPS is proposed and a systematic classification is presented. More than 140 scientific papers and publications are studied and categorized which can provide a fast review and a perfect perspective on the status of PQ indexes for researchers and experts.

Multilevel inverters are currently the subject of extensive investigation and are used primarily for medium and high voltage distribution systems. The work presented in this paper provides a cost-effective and realistic solution to mitigate power quality (PQ) problems. A Cascaded H-Bridge multilevel inverter (CHB-MLI) has been configured as a shunt active power filter (SAPF). It is well reported that large-scale use of power electronics-based devices leads to several PQ problems such as poor power factor, unregulated dc voltage, harmonics, voltage regulation etc. In this paper, an improved immune feedback control algorithm is proposed and developed to mitigate PQ issues by predicting the weighted active component of load current and to generate reference current for the grid. Extensive MATLAB simulation and experimental work have been reported for validation on a single-phase system. A low prototype model is developed in the laboratory to study and compare the steady-state and dynamic results of the proposed controller with conventional Least Mean Square (LMS) and Immune algorithm.

With the wind power generation in power system increase gradually,the problem of power quality which caused by grid-connection is becoming more and more serious. Power quality indexes of 100 MW wind farm including voltage deviation, harmonic.Three-phase unbalance and voltage flicker were made real-time monitoring in Inner Mongolia. Data analysis displays that the wind farm can satisfy the standard of power quality. Researches show that power quality's testing of the wind farm can improve the reliability of the power system stabilization. Moreover,it is beneficial to the wind turbine's security,stability and preventive maintenance.

The unified power quality conditioner (UPQC) is a power conditioning device, which is a integration of back to back connected shunt active power filter (APF) and series APF to a common DC link voltage. For improvement of power quality (PQ) problems in a three-phase four-wire distribution system, two topologies are proposed in this paper. A comparative analysis of these topologies along with the most common four-leg voltage source inverter (VSI) based topology of four-wire UPQC is discussed in this work. The performance of each topology of UPQC is evaluated for different PQ problems like power-factor correction, load balancing, current harmonic mitigation, voltage harmonic mitigation and source neutral current mitigation. The synchronous reference frame (SRF) theory is used as a control strategy of series and shunt APFs. The simulation results using MATLAB/Simulink enviournment are obtained, which support the effectiveness of these topologies of UPQC for power quality improvement.

This chapter introduces the custom power device to solve the various kinds of power quality (PQ) problems. It is generally known as flexible AC transmission system (FACTS) and D-FACTS (FACTs used for low voltage and low current rating in AC distribution system). The D-FACTS are various types like dynamic voltage restore (DVR), static compensator in distribution system (D-STATCOM), and unified power quality conditioner (UPQC). The third one is combination of DVR and D-STATCOM, which is known as UPQC. The UPQC can compensate all the PQ problems. Comprehensive knowledge of UPQC is presented here to understand the trade value of this device. This chapter is organized as follows: The evaluation of power electronic based devices is presented in the background part of this chapter where custom power devices (CPDs) are also discussed. And operating principle with the Matlab model of UPQC and results are presented in the section titled “Working Principle of Unified Power Quality Conditioner (UPQC).” The scope of the one of the functional power electronic based devices are presented in section titled “Scope of UPQC.” At the end, this chapter is concluded.

Power Quality Problem (PQP) includes several kinds of problems such as harmonics and voltage sag. Locating PQP online can help take countermeasures, and it is very important. With help of mobile agents, PQP can be located with dynamically geographically changed agents. The Power Quality Management System (PQMS) is built on agents, and data transmission is implemented using Person to Person (P2P) and Foundations of Intelligent Physical Agents (FIPA). As PQP location is a Multi-Objective Problem (MOP) system, a Feedback Balanced Genetic Algorithm (FBGA) is used to help decide the location of PQP. The algorithm for actual PQP modeling is not discussed, and FBGA is an important algorithm for data collection and ultimate analysis. In FBGA, feedback messages are used to adjust optimization rules, and balanced genetic algorithm is used to achieve the Patero solution for MOP. Convergence of the algorithm is analyzed. Implementation of the algorithm proves feasibility of the algorithm.

96/00456 Heard a flash. Saw a boom. Power quality monitoring defined in P1159

This paper presents an integration of S-Transform and Probabilistic Neural Network (PNN) technique for identifying the location of a switched capacitor causing a power quality problem. The transient caused by the capacitor switching is one of the important power quality (PQ) problems since it may adversely affect the system as well as sensitive loads. S-Transform has the ability to detect the disturbance correctly in the presence of noise riding on the signal. Hence, S-Transform technique is used for locating switched capacitors under noisy environment. In order to extract efficient features, capacitor switching signals are applied to two S-Transform algorithms and they are processed parallely. Those features are then applied to PNN for training and subsequently tested for automatic classification of switching signals. The simulation results reveal that the combination of S-Transform and PNN can effectively locate the switched capacitor even under the noisy environment.

In this paper, the power quality problems of a DC arc furnace load are investigated. An 18-pulse converter is used to provide the DC currents to the furnace. The power quality problems concerned are the harmonics and voltage flicker (voltage fluctuation). Field measurement is used to reveal the harmonic distributions of the rectifiers under balanced and unbalanced conditions. The effect of passive harmonic filters is also investigated. Although the DC arc furnace is operated in constant current mode, there is still an obvious reactive power variation to cause voltage flicker. Statistics is used to reveal the load fluctuation. Finally, a feasible reactive power compensation scheme with instantaneous values is studied to mitigate the voltage flicker problem.

Arc furnaces are used in industries for induction heating and welding. Due to the rapid growth of nonlinear loads, such as power electronic control equipments and Electric arc furnace (EAF) power quality problems such as harmonics and voltage flicker are introduced in the power system. It occurs because of the time-varying and non-linear behaviour of the electric arc furnace operation. Hence an Electric arc furnace model is needed to analyze the power quality. In this paper, a time domain model called hyperbolic model for electric arc furnace is analyzed using MATLAB. The model is used to study its behaviour on the power system using MATLAB. To improve the power quality D-STATCOM is proposed, in which the control strategies used are Direct, Indirect control and Hysteresis controller. Direct control technique uses P-Q theory in which transformation is based on orthogonal reference frame. Indirect control technique uses d-q theory in which transformation is based on synchronous reference frame. Hysteresis controller uses Hysteresis Bandwidth to produce the switching signals.