N. Rathina Prabha

Adaptive neuro-fuzzy inference system based representative quality power factor for power quality assessment

Under sinusoidal operating conditions of electric power system, the classical definitions of apparent power and power factor work well as long as the loads are linear and the source voltage waveform is sinusoidal. Increase in use of power electronic devices, adjustable speed drives and other nonlinear loads cause the voltage and current waveforms to become non-sinusoidal and highly distorted. A new adaptive neuro-fuzzy inference system based representative quality power factor (ANFIS RQPF) is proposed in this paper to represent the existing different power factors-displacement power factor, transmission efficiency power factor and oscillation power factor. The ANFIS RQPF can represent an essential module for evaluating and amalgamating the three power factors. The ANFIS RQPF was applied to different cases-linear, nonlinear, sinusoidal and non-sinusoidal considering lagging and leading power factors. It is shown that the ANFIS RQPF is expressive and accurately represents the existing power factors in all cases and in all situations. Taking into consideration the advantages of the ANFIS such as simplicity, ease of application, flexibility, speed and ability to deal with imprecision and uncertainties, this factor can be useful for power quality assessment, cost-effective analysis of power quality mitigation techniques, as well as billing purposes, in these situations.

Fuzzy controlled UPQC for power quality enhancement in a DFIG based grid connected wind power system

Owing to fuel scarcity and environmental contamination set off by the conventional sources, renewable energy resources rule the world of power generation. Up gradation of energy production through wind farms is being encouraged now-a-days, as the wind power is dirt free, readily available renewable alternative. The integration of wind farms with power grid leads to Power Quality (PQ) issues such as voltage sag, swell, flicker, harmonics etc. Most of the industrial and commercial loads are of non-linear type which indeed the starting place of harmonics. As 70% of PQ problems are voltage sag which is one of the most severe disturbances to sensitive loads. As an outcome of the aforementioned issues both consumer sector and production sector gets affected with poor quality of power which urge PQ enhancement at its best level. Among many of custom power devices, Unified Power Quality Conditioner (UPQC) is the only device used to diminish both voltage sag and current harmonics. This paper analyzes PQ problems, voltage sag and current harmonics due to the interconnection of grid connected wind turbine and also provides PQ enhancement by introducing UPQC. To improve the performance of UPQC, a novel control strategy using Fuzzy Logic Controller (FLC) is proposed which eliminates the drawback of using fixed gains in conventional PI controller. From the simulation results, by comparing controller performance, the proposed fuzzy controlled UPQC provides effective and efficient mitigation of both voltage sag and current harmonics than the conventional PI controlled UPQC, thus making the grid connected wind power system more reliable by providing good quality of power.

Adaptive neuro-fuzzy inference system based total demand distortion factor for power quality evaluation

An adaptive neuro-fuzzy inference system based total demand distortion factor (ANFIS TDDF) is proposed in this paper. When considering a single range of short circuit level, the values of total demand distortion (TDD) are enough to quantify harmonic distortion in a certain current waveform. When considering multiple ranges of short circuit levels the TDD is unable to determine whether the distortion is within the acceptable limits or not. The ANFIS TDDF indicates the level of distortion in the current waveform or how close is the waveform to a pure sinusoidal wave shape and also allows deciding whether the distortion contained in the current is within the acceptable limit or not. Moreover, the use of an adaptive neuro-fuzzy inference system (ANFIS) has the advantages of being simple, easy to implement and contains its knowledge base. The proposed ANFIS TDDF is sensitive to the TDD and short circuit level changes in all distortion cases in sinusoidal and non-sinusoidal situations. Therefore it will be very useful for many applications such as power-quality (PQ) evaluation, cost-benefit analysis of PQ mitigation techniques and setting penalty tariffs for customers generating harmonics.

Design of ultra-capacitor based DVR for power quality improvement

Power Quality (PQ) is the most significant perspectives at transmission and distribution levels. The supply of high grade electrical services required to the customers illustrates this concept. The voltage sag and swell are the most frequent PQ problems that mainly occur in the distribution systems since it may cause equipment tripping, failure of drive systems, shutdown for domestic and industrial equipment. The Dynamic Voltage Restorer (DVR)connected in series has magnificent dynamic capabilities and is a flexible solution for PQ problems. Ultra-capacitors (UCAP)have ideal characteristics such as high power and low energy density essential for the mitigation of voltage sag and swell. This paper presents an enhanced DVR topology capable of delivering deep, extended mitigation for power quality problems. In the proposed DVR, UCAP is used as energy storage as it provides excessive power in a short interval of time. The DVR is integrated into Ultra-capacitor via bidirectional DC-DC converter which supports in presenting a rigid dc-link voltage, and also helps in compensating temporary voltage sag and voltage swell. PI Controller is used in DVR for power quality enhancement. The simulation model for the proposed system has been developed in MATLAB and the performance over conventional DVR is validated with the results obtained.

PI control of multi level inverter based shunt active power filter for harmonic mitigation in three phase systems

Cascaded multilevel inverter is a power electronic device developed to synthesize a desired voltage or current waveforms from several levels of dc voltages making use of its reduced switching stress and modular structure. Such inverters have been recognized as very attractive topologies for implementing shunt active power filters in medium and high voltage applications. This paper presents a five-level cascaded multilevel inverter based Shunt Active Power Filter (SAPF) to compensate reactive power and mitigate the harmonic currents generated by the non-linear loads. The functioning of the proposed system is improved by the inclusion of PI controller for dc-side voltage regulation of SAPF and triangular carrier current controller for the generation of switching pulses for the inverter switches. The control strategy of SAPF also incorporates Synchronous Reference Frame (SRF) theory to extract the harmonic components from distorted line currents which in turn are utilized in the production of required reference compensation currents. This paper primarily focuses on the mitigation of the harmonics produced by the use of nonlinear loads with the aid of PI controller for dc voltage regulation. Extensive simulations are carried out to validate performance of the proposed SAPF system using MATLAB/ SIMULINK for diode bridge rectifier with RL load. The dynamic responses of the proposed SAPF system is verified under varying load conditions.

Interval Type-2 Fuzzy Logic Controller-Based Multi-level Shunt Active Power Line Conditioner for Harmonic Mitigation

The use of variable speed drives in industries introduces harmonics that should be attenuated so as to improve the power quality. To overcome the shortcomings of the traditional passive filters in electric power system, shunt active power line conditioners (APLC) are employed. The regulation of DC capacitor voltage plays a vital role in deciding the performance of shunt APLC. Several intelligent controllers have been developed for the voltage control; however, due to high uncertainties associated with the electric power system, an interval type-2 fuzzy logic controller (IT2 FLC) is proposed. This work compares IT2 FLC, type-1 fuzzy-tuned proportional integral (PI) controller, and their performances are assessed with reference to conventional PI controller using MATLAB. Thus, the paper deals with the investigation of three-level Multi-Level Inverter which is used as shunt APLC in high-power applications using a fuzzy logic scheme.

Simulation of Reduced Rating Dynamic Voltage Restorer using SRF–ANFIS Controller

Power Quality (PQ) and reliability in distribution system have been appealing to a greater extend in modern era and also have become an area of concern for current industrial and commercial applications. This paper examines the problem of voltage sag and swells and also deals with the improved design of Dynamic Voltage Restorer (DVR) for PQ enhancement. A novel control algorithm Synchronous Reference Frame (SRF) theory with Adaptive Neuro-Fuzzy Inference System (ANFIS) controller is proposed for the creation of reference DVR voltages. In addition, different voltage injection schemes are analyzed to focus on novel method for the design of Reduced Rating DVR (RRDVR) to improve its performance in terms of output power, cost and size. The proposed DVR is demonstrated for PQ problems sag and swell using MATLAB/SIMULINK. During compensation, the output power attained from the proposed DVR is also compared with other intelligent controllers, namely Fuzzy Logic (FL) and ANFIS controller. Simulation results proved that the proposed SRF–ANFIS controller-based RRDVR offers economic solution for both utilities and customers by providing extremely deep compensation for voltage-based PQ problems occurring at very short duration of time.

PEMFC supported dynamic voltage restorer for power quality enhancement

The continuity of supply and quality of power supplied to the customers must be uninterrupted from the reliability point of view. The Dynamic Voltage Restorer (DVR) is a custom power device which has an advantage of fast dynamic response and can generate real or reactive power independently. This paper presents the improved topology for DVR by the integration of Proton Exchange Membrane Fuel Cell (PEMFC) with boost converter as a DC input to the DVR. Thus the proposed DVR ensures a constant DCvoltage across the DC link during the process of voltage compensation with active power injection to the grid. The performance of the proposed work is endorsed by comparing the results with conventional DVR and the simulation results are also validated to prove the effectiveness of the proposed work.