P.V.S. Sobhan

Implementation of Static VAR Compensator for Improvement of Power System Stability

Static VAR compensator (SVC) is incorporated in Newton Raphson method in which Power Flow Solution is a solution of the network under steady state conditions subjected to certain constraints under which the system operates. The power flow solution gives the nodal voltages and phase angles given a set of power injections at buses and specified voltages at a few, both the models of SVC i.e.SVC Susceptance and Firing Angle Models are discussed. It is also shown that the power system losses are decreased after incorporating the SVC in this N-R method. The results are generated for 24-Bus system. The reactors are thyristor-controlled and the capacitors can be either fixed or controlled. Advanced load flow models for the SVC are presented in this paper. The models are incorporated into existing load flow (LF) Newton Raphson algorithm. The new models depart from the generator representation of the SVC and are based instead on the variable susceptance concept. The SVC state variables are combined with the nodal voltage magnitudes and angles of the network in a single frame of reference for a unified, iterative solution through Newton methods. The algorithm for Load Flow exhibit very strong convergence characteristics, regardless of the network size and the number of controllable devices. Results are presented which demonstrate the process of the new SVC models.

Optimal Power Flow by Newton Method for Reduction of Operating Cost with SVC Models

The optimal power flow is a power flow problem in which certain variables are adjusted to minimize an objective function such as cost of the active power generation or the losses,while satisfying physical operating limits on various controls, dependent variables and function of control variables. Current interest in OPF covers around its ability to solve for the optimal solution that takes account of security of the system. Practical solutions for OPF problems with separable objective functions have been obtained with special linear programming methods,but the classical OPF has defined practical solutions, the Newton approach is a flexible formulation that can be used to develop different OPF algorithms suited to the requirements of different applications. In other words, the optimal power problem seeks to find an optimal profile of active and reactive power generations along with voltage magnitudes in such a manner as to minimize the total operating costs of a thermal electric power system, while satisfying network security constraints. The OPF method is based on load flow solution by the Newton’s method, a first order gradient adjustment algorithm for minimizing the objective function and use of penalty functions to account for inequality constraints on dependent variables.

Rotor levitation by Active Magnetic Bearings using Fuzzy Logic Controller

Active Magnetic Bearings(AMB) have many advantages such as no friction loss, no abrasion, lubrication-free quality, and used for high rotational speed applications. A complete system consists of an actuator, power amplifier, a rotor position sensor and a control system. In this paper, a closed loop decentralized Fuzzy Logic control for Active magnetic Bearings is designed. For the numerical evaluation of control algorithm a MIMO (multiple input multiple output) mathematical model of the controlled plant is determined. The majority of industrial applications of active magnetic bearings were still based on conventional PID control system. The proposed control design is based on rule based procedure. It has been shown, that the presented FL control guarantees satisfactory high damping, low parameter variations and measurement noise of the overall system. With this FL control we are able to maintain the rotor in center position in the final steady state.

Robustness of Fuzzy Logic based Controller for Unmanned Autonomous Underwater Vehicle

The underwater vehicle is six degrees of freedom model. The execution of spatial maneuvers are determined mainly by the dynamic properties of underwater vehicle particularly controllability and stability. The control surfaces are situated at the rear end of the underwater vehicle which moves either vertically or horizontally (pitch, yaw, roll, pitch-rate, yaw-rate etc.) used to steer the vehicle to run according to preprogrammed course as per logic till such a time the target is acquired. The underwater vehicle response is slow compared to air scenario due to constraints like higher density of water; the resistance motion is many hundred times greater than air. In this paper a rule-based fuzzy logic controller is designed for yaw control, which is used for the rudder movement of an underwater vehicle. A plant model is extracted using the input and output behavior and is assumed to the either linear time invariant first order or second order. Since the plant models obtained by the above process are very approximate, 50% variations are given on damping (xi) and natural frequency (omegan) of second order plant and similarly the gain and time constant are varied for the first order plant. The performance evaluation of fuzzy logic controller under the above varying plant conditions is done and the results have been presented and analyzed.

Look Up Table Based Fuzzy Logic Controller for Unmanned Autonomous Underwater Vehicle

The underwater vehicle is six degrees of freedom model. The execution of spatial maneuvers are determined mainly by the dynamic properties of underwater vehicle particularly controllability and stability. The control surfaces are situated at the rear end of the underwater vehicle which moves either vertically or horizontally (Pitch, Yaw, Roll, Pitch-rate,Yaw-rate etc.) used to steer the vehicle to run according to preprogrammed course as per logic till such a time the target is acquired. The underwater vehicle response is slow compared to air scenario due to constraints like higher density of water; the resistance motion is many hundred times greater than air. In this paper a rule-based fuzzy logic controller is designed for Yaw control, which is used for the rudder movement of an underwater vehicle. A Plant model is extracted using the input and output behavior and is assumed to be a linear time invariant second order. For on line implementation a decision table is stored in underwater vehicle computer memory in the form of Lookup table. For each combination of Inputs the required search will be done in the table and the appropriate value will be picked up. Using this technique the control algorithm becomes shorter and runs faster than those that reinterpret the rules at each control cycle of the system. This Lookup Table is used in the simulation of Yaw control of a Six Degrees of Freedom Model. The plant responses are compared for both conventional controller and fuzzy logic controller with regard to time of response, overshoot and steady state error.

Design of state-PID feedback controller for magnetically suspended balance beam system

This paper presents the design of an State-PID Feedback Controller (SFCPID) for a highly unstable non-linear system, magnetically suspended balanced beam (MSBB) and analysis of its effects. The modelling of Magnetically Suspended Balance Beam (MSBB) and design of Integral sliding mode controller are carried out using MATLAB/SIMULINK. The disturbance rejection of the controller is investigated and the stabilization performance of the State-PID Feedback Controller is compared with that obtained by a conventional state feedback controller with integral action when a disturbance force applied.

Analysis and design of non-isolated single phase AC/DC PFC topologies to drive LEDs

This paper presents a detailed analysis of several topologies of single stage AC/DC non isolated converters used as a power supplies for driving LEDs. High power factor and regulated voltage is achieved with these topologies. These converters are designed with 230V AC input, 48V DC output for 200W load at switching frequency of 20KHZ. Implementation and comparison of topologies are done on MATLAB/SIMULINK software.