Multilevel Inverter Based Power Quality Enhancement Using Improved Immune Control Algorithm

Multilevel inverter (MLI) especially cascaded H-bridge-type MLI provides transformer-less solution in case of medium-voltage and high-power distribution scenario for mitigating current-related power quality (PQ) problems. Performance of MLI-based shunt filtering unit is dependent on control and extraction technique used. Therefore, a lot of control algorithms are already proposed for conventional two-level inverter-based shunt active power filter (SAPF). However, most control algorithms and their capabilities are yet to be explored for MLI-based SAPF. In view of this concern, this paper aims at presenting an advanced control technique for cascaded H-bridge multilevel inverter-based shunt active power filter. This control scheme composed of three parts, i.e., sensing of source voltage, load and source current, DC-link voltage regulation, and reference current generation technique. DC-link voltage regulation and its characteristics are important in terms of settling time and peak overshoot during load changing condition. Normally, PI compensators are used for DC-link voltage regulation during transient and steady-state conditions. However, soft computing techniques give better response in case of DC voltage regulation. Therefore, modified three-layered artificial neural network (M3L-ANN) is used in this paper for regulating DC-link voltages. The proposed control technique is simulated in MATLAB/Simulink with three-phase and five-level CHB-MLI-based SAPF. Extensive simulation analysis is presented and verified. It shows better performance in terms of settling time and peak overshoot during load changing condition. Simultaneously, source current also becomes well below 5% as per IEEE-519 standard.

In today’s scenario, the integration of a grid-connected load system with a hybrid energy system (HES) is encouraged to improve the reliability of the system. With the stunning rise in nonlinear loads in HES over the last two decades, the power quality (PQ) of the system has emerged as a paramount concern in contemporary times. The power quality problems include the injection of harmonics in the source current, low input power factor, poor voltage regulation, the burden of reactive power, etc. So, to mitigate these power quality problems in a single-phase distribution system, a 3-level Cascade H-bridge (CHB) inverter-based shunt active power filter (SAPF) is employed alongside a proposed Trianguzoidal pulse width modulation (TRZ PWM) strategy. The single-phase distribution system with SAPF is simulated in fixed and dynamic load conditions to check the system’s efficacy. The proposed PWM techniques for SAPF are compared with conventional PWM techniques, i.e., level shift, phase shift, and hybrid PWM techniques. Results indicate satisfactory performance of the proposed PWM techniques, exhibiting low harmonic distortion in source current, well within IEEE 519 limits, and high active filtering efficiency (AFE) compared to conventional PWM methods. Furthermore, this paper provides detailed comparisons of conventional and proposed PWM techniques in the context of active & reactive power supplied or delivered by load, source, and compensator, input power factor, harmonics in source or grid current, AFE, and individual harmonic components concerning fundamental component of source current.

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 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 recent years, power electronics devices have evolved, and used for varies applications. Also, this device caused the problem of power quality in electrical system. In the utility side arc furnaces, variable frequency drives (VFD), personal computer, fluorescent lamp such non-linear load produces current harmonics. For consumer and distributed side the power quality is an important issue. The active power filter which is capable for improving the power quality and reactive power compensation. In this paper the harmonics problem which is created by non-linear load is discussed. Shunt active filter is used for eliminating the harmonics from non-linear load and in the retrieval technique for controlling the current hysteresis current controller is used. In this paper for producing the reference current instantaneous reactive power (PQ) theory is used. The simulation result of shunt active filter using PQ theory is carried out using Matlab-Simulink toolbox.

Due to the proliferation of non-linear modern power electronics, currents and voltages produced by non-linear loads have lead to the deterioration and distortion of the output sine wave forms of the source currents and voltages. These distortions have resulted in the power quality problems. The non-linear load draws reactive power and harmonics from the ac source in the fundamental current. The harmonics in power system caused by non-linear loads such as, arc furnaces, switch mode power supply, fluorescent lamps rectifiers etc all are the main sources of harmonics, as a result of these non-linear loads the supply system lead to overheating of cables and conductors, electromagnetic interference to nearby communication facilities etc. Therefore, as a result of theses harmonics, a traditional passive filters are used to suppressed the integer multiple fundamental frequencies, but due to the passive filter draws back in producing series or parallel impedance with the supply impedance and heavy in sized, its limitations in service becomes an old scheme. The application of shunt active power filter in mitigating these harmonics problems supersedes the used of passive filter. This paper, presents the modeling and simulation of single-phase shunt active power filter controlled with fuzzy logic controller (FLC) to mitigate the harmonics drawn by non-linear loads. The proposed scheme is performed by using MATLAB fuzzy tool box environment. Simulation results obtained by the proposed control algorithm found to be satisfied and within the recommended imposed IEEE 519-1992 harmonic standard limit.

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.

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.

Power quality (PQ) problems include harmonics, voltage flicker, three-phase imbalance, voltage swell/sag, interruption, switching transient and so on. Identification of accurate location and occurrence time of PQ problem is important for understanding the underlying cause and to prevent future occurrence. This study presents a new method for placement of power quality measurement facilities to identify PQ problems. The power harmonics and capacitor switching transients are used as disturbance sources for illustration. The proposed method first utilises harmonic voltages and wavelet coefficients as PQ features. An enhanced genetic algorithm is proposed for solving the modified K-means clustering to place PQ measurement monitors. Simulation results for an 18-bus system show that the proposed approach is effective in comparison with the existing approaches.

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 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.

This paper presents a design and simulation of a controller circuit for Power Factor Correction applied to BLDC Motor Control. To achieve accurate and dynamic performance from a BLDC motor, it is usually fed from a Voltage Source Inverter (VSI). Such drives have to deal with problems in power quality and poor power factor at AC mains input as they include a diode bridge rectifier. To overcome such problems and provide faster dynamic performance a power factor correction One Cycle Controlled Cuk converter is proposed to feed the Voltage Source Inverter based BLDC motors. The Cuk PFC converter inherits many advantages like low output current and voltage ripple, near unity power factor with simple control. The One Cycle technique provides excellent power source disturbance rejection, fast dynamic response, automatic switching error correction and robust performance.

The term power quality (PQ) has got major attention at the distribution side and consumer side in the recent years. Continuous rise of power electronic devices in grid-tied applications, uninterruptable power supplies (UPS) and motor drive applications etc, simplifies the control technology, and makes the system robust and flexible. But, these devices inject the current harmonics into the line which pollutes the electrical system. In addition, it draws more reactive power and creates the unbalance in the system. Initially, passive filtering techniques (inductors and capacitors) were used to lessen the PQ problems. Because of the lacking of the quality performance, the passive filter methods have been replaced with advanced power electronic topologies. Researchers, constantly investigates for better and cost effective solutions to improve system PQ. Shunt active power filter (SAPF) is one of the better solutions for enhancing the power quality by compensating the harmonic currents and other reactive power problems in the grid-tied system. In this paper, the basic structure of SAPF is briefly discussed along with the detailed control system functionalities. This paper provides a concise assessment on SAPF classifications, topologies and comparisons of single-phase, three-phase three-wire (3P3W) and four-wire (3P4W) systems. The features of all the configurations are provided along with their complications, so as to identify the better topology for specific application. The merits and demerits of these configurations are also discussed briefly.

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