DESIGN OF ARTIFICIAL NEURAL NETWORK BASED TID CONTROLLER FOR TRANSIENT STABILITY IMPROVEMENT

This paper is to present the design of the neural network based TID controller applicable to static VAR compensator (SVC) on two machine 3-bus transmission system to improve the transient stability when sudden disturbances occur in transmission system. i.e three phase fault. The power system network considered is to simulated using phasor simulation method. Comparisons regarding stability are done for the system without controller, PI control ler, TID controller and Neural Network based TID controller. Simulation results show that the proposed Adaptive Neural network based TID controller was effective in reducing power system oscillations compared to other controllers

Isolated induction generator, induction motor scheme for borehole pump and other application

Imperial Users onl

Development of Voltage Controller and Fault Analysis of Self Excited Induction Generator System

Increasing fuel cost and attempt to get pollution free environment, renewable sources of energy such as the wind, solar, micro-hydro, tidal wave, and biomass, etc. have grabbed recently the attention of researchers. Among these available energy resources, the use of wind energy is growing rapidly to generate and supply electricity as grid connected or stand alone mode. To generate electric power from such non-conventional sources, self-excited induction generator (SEIG) is found to be a suitable option for either using in grid connected mode or isolated mode. Selection of SEIG in these areas depends on its advantages such as low cost, less maintenance, and absence of DC excitation. High maintenance and installation costs including transmission losses of conventional power supply to remote or isolated place by means of power grid can be reduced by installing stand-alone wind driven SEIG system at those places. In the year of 1935, self-excitation concept in squirrel cage induction machine with capacitors at their stator terminals was introduced by Basset and Potter. But the problems associated with SEIG are its poor voltage and frequency regulation under load and prime mover speed perturbations which put a limit on the use of SEIG for a long time. By controlling active and reactive power accurately, it is possible to regulate frequency and voltage of SEIG terminal during load and speed perturbations. Various efforts have been put by researchers in developing SEIG voltage and frequency controller but these control schemes demand multiple sensors along with complex electronic circuits.This dissertation presents some studies and development of new voltage controller of the SEIG system for balanced resistive, R − L and induction motor (IM) load that is used in isolated or remote areas. So in this context, an attempt is taken to develop an optimized voltage controller for SEIG using Generalized Impedance Controller (GIC) with a single closed loop. Stable zones of proportional and integral gains for GIC based SEIG system are computed along with parameter evaluation of the GIC based SEIG system. Further, Particle Swarm Optimization(PSO) technique is used to compute the optimal values of proportional and integral gains within the stable zone. The research work on SEIG system is extended to develop a voltage controller for SEIG with minimum number of sensors to make the system less complex and cost effective. Here, a voltage peak computation technique is developed using Hilbert Transform and computational efficient COordinate Rotation DIgital Computer (CORDIC) which requires only one voltage sensor and processed to control SEIG voltage for GIC based SEIG system. This voltage control scheme is implemented on commercially available TMS320F2812 DSP processor and performed laboratory experiment to study the performance of GIC based SEIG system during load switching. The work of this thesis is not confined only to study an optimal and simple voltage controller for SEIG system but also extended to investigate the fault identification methodologies of SEIG system. Here, the features of non-stationary SEIG signal with faults are extracted using Hilbert-Huang Transform (HHT). Further, different classifiers such as MultiLayer Perceptron (MLP) neural network, Probabilistic Neural Network (PNN), Support Vector Machine (SVM), and Least Square Support Vector Machine (LS-SVM) are used to identify faults of SEIG system. In this study, it is observed that LS-SVM among above classifiers provides higher classification accuracy of 99.25%

Control system for small induction generator based wind turbines

The unpredictable nature of wind makes the design of wind turbines control system a challenging task. Wind turbine system control becomes more difficult when the system is required to connect to the grid. The major issues include connection standard, control system simplicity, cost, reliability, required instrumentation and modes of system operation. A low cost control system and associated instrumentation development is very important for the commercial success of a small grid connected wind turbine. The proposed PIC micro-controller based control system is a good candidate for 3 kW or less grid connected wind power systems. -- The purpose of this thesis is to design a control system for small induction generator based grid connected wind turbines. A PIC16F877 micro-controller is used to connect/disconnect the wind turbine generator to the grid based on real time measurements. The controller is designed and tested for grid connected mode and off-grid mode. The system controller based on the measurements takes decision for grid connection/disconnection or maintains the connection of the system with the grid. Designed controller also takes care of the islanding situation. Such situation occurs in the system while wind is enough to produce power but the grid is absent. The proposed controller will never connect the wind turbine to the grid when grid is absent hence islanding situation will never occur. Low cost instrumentation is also developed to measure the system parameters. -- The designed controller is tested in a laboratory environment using a wind turbine simulator. Wind turbine simulator is an effective platform to evaluate the performance of the wind turbine control system in all possible situations in the lab environment. The proposed wind turbine simulator is based on a 3 kW DC motor. A separately excited DC motor is controlled so that its shaft behaves as a wind turbine rotor. A PI controller is designed which makes sure that the DC motor is producing torque same as wind turbine rotor torque at various wind speeds. -- Soft-starter is also designed to reduce inrush current or surge in current while achieving a proper synchronization between the wind turbine generator and the grid. The designed soft-starter successfully limits the high inrush current during the connection of the wind turbine system to the grid. An experimental investigation is done to find out suitable values of the power resistors for soft-connection of a small wind turbine system to the grid. The designed soft starter limits the initial surge current 1.62 times the rated current of the induction generator. -- While grid is absent, the system controller ceases the power delivery to the grid and connects the wind turbine system to a dump load. However, due to the variation in wind speed the voltage at the load terminal can vary. An electronic PI controller based on phase control relays is developed to regulate the voltage across the dump load while grid is absent. -- The applicability of the proposed system controller for small wind turbines is demonstrated through a number of lab tests. The results show the designed control system is able to control a 3 kW induction generator based wind turbine both in grid connected and off-grid mode

Voltage Stability Enhancement of Wind Generator System Using Superconducting Fault Current Limiter

Wind generator systems have stability problems during network faults. The superconducting fault current limiter (SFCL) has the ability to prevent the magnitude of short-circuit current from increasing. This work proposes the SFCL device to enhance the voltage stability of a fixed-speed wind generator system.In this work the performance of SFCL is compared to that of the thyristor switched capacitor (TSC) method and the pitch control method. The comparison is done in terms of voltage stability enhancement, controller complexity and cost. The effectiveness of the proposed methodology is tested considering permanent and temporary, balanced and unbalanced faults in the power system model consisting of a wind generator and a synchronous generator.From the simulation results it is evident that performance of SFCL is better. On comparison it can be concluded that SFCL performs better when compared to TSC or pitch control method. Simulations are performed through Matlab/Simulink software

Effect of Symmetrically Switched Rectifier Topologies on the Frequency Regulation of Standalone Micro-Hydro Power Plants

Micro-hydro power plants (μHPPs) are a major energy source in grid-isolated zones because they do not require reservoirs and dams to be built. μHPPs operate in a standalone mode, but a continuously varying load generates voltage unbalances and frequency fluctuations which can cause long-term damage to plant components. One method of frequency regulation is the use of alternating current-alternating current (AC-AC) converters as an electronic load controller (ELC). The disadvantage of AC-AC converters is reactive power consumption with the associated decrease in both the power factor and the capacity of the alternator to deliver current. To avoid this disadvantage, we proposed two rectifier topologies combined with symmetrical switching. However, the performance of the frequency regulation loop with each topology remains unknown. Therefore, the objective of this work was to evaluate the performance of the frequency regulation loop when each topology, with a symmetrical switching form, was inserted. A MATLAB® model was implemented to simulate the frequency loop. The results from a μHPP case study in a small Cuban rural community called ‘Los Gallegos’ showed that the performance of the frequency regulation loop using the proposed topologies satisfied the standard frequency regulation and increased both the power factor and current delivery capabilities of the alternator.This contribution is a result of a cooperation between the APlied Electronic Research Team (APERT) at the University of the Basque Country (UPV/EHU), supported by the Department of Education of the Basque Government, within the fund for research groups of the Basque university system IT978-16, the Power Electronics Control in Energy and Motion Systems group (PECEM) at the University of Oriente, and the IRIS project for Cuban energy transformation. Integration of Renewable Intermittent Sources in the power system (IRIS, 2019-2022) is financed by Academy of Science in Finland, Grant/Award Number 320229. The authors of this article gratefully acknowledge these financers and project partners

Advanced control system for stand-alone diesel engine driven-permanent magnetic generator sets

The main focus is on the development of an advanced control system for variable speed standalone diesel engine driven generator systems. An extensive literature survey reviews the historical development and previous relevant research work in the fields of diesel engines, electrical machines, power electronic converters, power and electronic systems. Models are developed for each subsystem from mathematical derivations with necessary simplifications made to reduce complexity while retaining the required accuracy. Initially system performance is investigated using simulation models in Matlab/Simulink. The AC/DC/AC power electronic conversion system used employs a voltage controlled dc link. The ac voltage is maintained at constant magnitude and frequency by using a dc-dc converter and a fixed modulation ratio VSI PWM inverter. The DC chopper provides fast control of the output voltage by dealing efficiently with transient conditions. A Variable Speed Fuzzy Logic Core (VSFLC) controller is combined with a classical control method to produce a novel hybrid controller. This provides an innovative variable speed control that responds to both load and speed changes. A new power balance based control strategy is proposed and implemented in the speed controller. Subsequently a novel overall control strategy is proposed to co-ordinate the hybrid variable speed controller and chopper controller to provide overall control for both fast and slow variations of system operating conditions. The control system is developed and implemented in hardware using Xilinx Foundation Express. The VHDL code for the complete control system design is developed and the designs are synthesised and analysed within the Xilinx environment. The controllers are implemented with XC95108-PC84 and XC4010-PC84 to provide a compact and cheap control system. A prototype experimental system is described and test results are obtained that show the combined control strategy to be very effective. The research work makes contributions in the areas of automatic control systems for diesel engine generator sets and CPLD/FPGA application that will benefit manufacturers and consumers.EPSR

High-Performance Control of Switched Reluctance Motors

A general high bandwidth, low ripple, instantaneous torque control strategy with a variable field-angle for extended constant-power speed range is presented. The strategy is based on the SR motor's electromagnetic characteristics measured at the motor terminals and is the nearest functional equivalent to AC vector control for this type of machine. Low torque ripple and high bandwidth are achieved over a wide range of speeds and a constant power range of 3:1. The proposed controller, which is applicable to most SR motors, is found to reduce the torque ripple by a factor of 5 in comparison with conventional square-wave current operation, and has been operated over a speed range of 1:6000

DESIGN OF REAL-TIME FUZZY LOGIC PSS BASED ON PMUs FOR DAMPING LOW FREQUENCY OSCILLATIONS

Poorly damped low frequency oscillations is one of the main problems threatening safe and stable operation of the interconnected power systems and reducing the capability of transmission the power. The generator's excitation system has been supplemented with the Power System Stabilizer (PSS) in order to improve the damping of these low oscillations. In the latest smart power grids, the Phasor Measurement Units (PMUs) become a fundamental element in the monitoring, protection and control applications as PMU signals are more accurate than the conventional measurement units and real time GPS stamped. In this study, Fuzzy Power System Stabilizer (FPSS) has been designed and its performance in damping inter-are oscillations compared with the conventional PSS (CPSS) based on the simulation with MATLAB/Simulink model. The results of the simulation with the Simulink model proved that the performance of the designed FPSS in damping inter-area oscillation is better than the CPSS. One of the main features of fuzzy controller is that it doesn't require mathematical modeling as it is designed based on the time-domain and the operator experience while, in contrast, the conventional PSS requires to be designed in the frequency domain. Real Time Digital Simulator (RTDS) has been used to develop the real-time models of the test systems. The time-domain simulations with the RTDS model when the system subjected to the large disturbance (three-phase to ground fault) have been performed to show that the designed FPSS improved the damping of the oscillations effectively. The simulation results have been verified by modal analysis