Manjula G. Nair

Power quality studies on a Soft-start for an induction motor

Three-phase induction motor of ratings beyond 50 kW take very large low power factor currents while being started directly from a 3-phase supply. Normally soft-starts are used for avoiding this problem and to achieve smooth starting of large capacity induction motors. A 3-phase AC voltage controller is employed as a soft-start. But, this takes harmonic-rich current especially while operating at large firing angles. In this paper, the effect of inserting a shunt active filter to provide harmonic and reactive power compensation in a soft-start has been studied. The shunt active filter has been inserted between the AC voltage controller and power supply to take care of the reactive power requirement of the motor and AC voltage controller and also to provide harmonic compensation. Both simulation hardware studies have been done on a 22 kW induction motor with and without soft-start arrangement. The shunt-active filter uses the IcosPhi control algorithm for calculating the compensation currents. The results with the insertion of shunt active filter show a substantial reduction in the current drawn from the source and its harmonic content. This will be a very useful scheme especially in industries where multiple induction motors of large capacity are frequently started from a 3-phase supply.

Power quality improvement using STATCOM with renewable energy sources

The renewable energy sources play an important role in electric power generation with growing environmental concerns. The inter connection of renewable energy sources are incorporated using power electronics converters, with the aim of improving power quality at the point of common coupling (PCC). This paper presents a novel idea where a STATCOM is used innovatively as a load reactive power compensator an interface unit between the grid and renewable energy source, and as an effective method for real power exchange between the dynamic load system, grid and renewable energy source. A controller unit is proposed for the STATCOM based on modified Icosf algorithm by which reactive power compensation and power factor correction is done and also real power support is provided by renewable energy source through STATCOM. The performance of the proposed algorithm is compared with the modified Instantaneous Reactive Power Theory (IRPT) control algorithm to achieve the above objectives.

An enhanced controller for shunt active filter interfacing renewable energy source and grid

Developing efficient interfacing technologies for the renewable energy source are promising research area now days. The interfacing unit becomes crucial as renewable energy sources when directly connected to grid, can inject harmonic components that may deteriorate the quality of power. This paper proposes a shunt active filter as an interface between renewable energy sources and grid with a modified and efficient control scheme. The shunt active filter with this modified controller controls the real power supplied by the grid (source) to load and remaining load requirements is supported by the renewable energy source in addition to its regular functions such as harmonic current elimination, reactive power compensation and power factor correction. In this paper two types of nonlinear loads are considered and simulated for analyzing the effectiveness of control algorithm to achieve the real power sharing from renewable energy source, grid along with harmonic elimination, reactive power compensation and power factor correction using shunt active filter interface.

Grid connected solar photovoltaic system with Shunt Active Filtering capability under transient load conditions

This paper discusses about the active filtering capability that can be incorporated in grid connected photovoltaic systems by proper control of the grid interfacing inverter. Improved Linear Sinusoidal Tracer Algorithm is used for generating the reference signals to control the inverter so that the system feeds the available photovoltaic energy into the grid, provides reactive power compensation and harmonic elimination of the loads connected at the point of common coupling. The controller is tested in MATLAB/SIMULINK for linear and nonlinear loads. The simulation results demonstrate the efficient working of grid connected photovoltaic system as Shunt Active Filter.

An ANN based Digital Controller for a Three-phase Active Power Filter

Three-phase shunt active power filters are designed to effectively compensate for the current harmonics and reactive power requirements in a three-phase system with harmonic loads. An ANN (artificial neural network) based controller selects the amount of harmonic current injection based on the percentage of harmonic distortion present in the source current and also on the reactive power requirement of the load. The selection is done by the ANN with the help of a properly tuned knowledge base.

Control and operation of microgrid connected Hybrid Energy Storage System

The high penetration of the Renewable Energy Sources (RES) can create stability, reliability and power quality problems in the main electrical grid due to their stochastic nature. Microgrids can be analysed as a solution capable of guaranteeing a controlled injection of energy generated by the renewable energy technologies. The use of storage system in a MG plays an essential role in order to ensure energy balance and in maintaining high power quality. Due to the technical limitations of the currently available storage systems, it is necessary to use more than one storage technology to satisfy the requirement of microgrid applications. In order to satisfy the above constraints, this paper proposes the association of a supercapacitor (SC) and a lithium ion battery in a Hybrid Energy Storage System (HESS). A novel control strategy is adopted for the control of the HESS. Hierarchical control is used for the control of the inverter in islanding and grid connected mode. Self synchronization control ensures smooth transition between islanded and grid connected modes. Simulation of the system is carried out in MATLAB/Simulink.

Tariff based fuzzy logic controller for active power sharing between microgrid to grid with improved power quality

Integration of microgrids to grid with the help of modern power electronic devices disturbs the grid stability. For improved integration and power sharing, a knowledge based algorithm using the concept of smart parks is introduced in this paper. Smart parks are electric vehicle charging centers which have a great potential to support the grid. Smart parks uses modified Icosφ control algorithm and by proper control of this algorithm, microgrids can provide active power support, reactive power compensation and harmonic elimination. Fuzzy logic controller is used for controlling the operation of microgrids depending upon certain factors like SOC level, source current and tariff. The simulation of tariff based fuzzy logic controller is performed in MATLAB/Simulink and it shows that it can provide improved integration of microgrids with less power quality issues.

Implementation of consumer level intelligence in a smart micro-grid along with HEMS based price prediction scheme

The consumer demand is increasing day-by-day with the emergence of new technologies for human comfort. The growing demand is expeditiously leading to the depletion of resources and increasing tariff. The improvised structure of the conventional grid namely, smart grid is rapidly gaining attention with its scheme for efficient meeting of the growing demand and the integration of renewables. The implementation of smart grid requires extensive communication methodology and structured control strategy. In this paper, the controls over the smart grid have been segregated into three as primary, secondary and tertiary. This paper deals with the intelligence associated with the primary and secondary levels placed in regard with the consumer and micro-grid operation. A price prediction scheme as a part of Home Energy Management System (HEMS) has also been designed to increase the consumer awareness. The role of the consumer as well as micro-grid in intelligent demand management has been demonstrated in this paper through simulations in MatLab using fuzzy logic. This system was also verified in hardware and the implementation details have been provided.

Simulation analysis of modified DC bus voltage control algorithm for power quality improvement on distributed generation systems

This paper presents a control strategy for shunt active filter interface for distributed generation scheme without degrading the power quality in the grid. The control strategy used enhances the performance of shunt active filter by sharing active power being generated from distributed generation to grid as well as load in addition to regular functions such as current harmonic elimination, reactive power compensation, power factor correction. The modified control algorithm is designed and analyzed for non-linear load using MATLAB/Simulink. The simulation results shows good performance of controller for power quality improvement of distributed generation system interfaced through shunt active filter.

Simulation analysis of half bridge series parallel resonant converter based battery charger for photovoltaic system

An innovative application of half-bridge series-parallel resonant converter (HBSPRC) for photovoltaic system and secondary battery interface is explained in this paper. This converter is designed for eliminating both low and high-frequency current ripples on the battery. This will helps to maximize battery life. The switching frequency greater than that of resonance frequency is preferred for operation, because the power switches turn on at zero current and zero voltage; thus, the freewheeling diodes need not have very fast reverse-recovery characteristics. Moreover the proposed battery charger circuit has a few components. To enhance the overall efficiency of the system energy conversion loss is to be minimized and the performance of the power converters depends upon the control method adopted. In this present work, Fuzzy logic based voltage controller and PI voltage controller have been designed, modeled and simulated in MATLAB/simulink platform and results are presented.