Abha Tripathi

Robustness study of dynamic inversion technique used in power system stability analysis

Modern power systems are operating increasingly closer to their control and operational limits. Such stressed conditions can lead a system to become unstable and hence it has become necessary to properly model the effect of such limits on the system. Also, gradual system parameter variations such as load increase, combined with contingencies, lead to system instabilities. The accuracy of power system stability analysis depends on the accuracy of the models used. Use of more accurate models would result in more reliable analysis, in terms of the power transfer capability. In this paper, a single Machine Infinite Bus (SMIB) system has been considered and it has been assumed that the inertia and damping coefficient of the machine is not measured properly and a random variation has been introduced to these parameters. In such a case, the robustness of the nonlinear control law, Dynamic Inversion (DI) has been studied. The control action is achieved using thyristor controlled series capacitor (TCSC).

A Two Level Message Adaptive Steganographic Approach

The need for secrecy during the transmission of digital messages over digital communication media has lead to the development of a number of techniques for covert communication. Steganography deals with the development and study of such techniques. In the present discussion, a two level Steganographic algorithm has been discussed that involves audio based and image based encoding. Also, the stage involving image based Steganography uses a heuristic methodology to adapt the algorithm according to the message stream. Visual and statistical analysis of this algorithm with a previously implemented Message Adaptive Steganographic Algorithm returns satisfactory results.

Effective Damping Control with TCSC Using Dynamic Inversion Technique

To achieve optimal utilization of global resources and reliable operation, modern power systems tend to be interconnected. Hence, many tie lines are built for transferring large amounts of electric power over geographically dispersed areas, especially from generation centers to load centers over long distances. As a result, many challenging issues arise in modern large-scale interconnected power systems. Flexible AC Transmission system (FACTS) devices have been widely employed in large-scale interconnected power systems and provide very good controllability to improve global system dynamics. Hence, research and development on control strategies of FACTS devices has become a significant task. Thyristor controlled series capacitor (TCSC) is a type of FACTS device which has powerful capabilities in damping power oscillations, scheduling power flow, reducing unsymmetrical components and mitigating sub-synchronous resonance and providing voltage support as well. In this paper, a nonlinear technique called Dynamic Inversion (DI) technique has been developed to control the firing angle of the thyristors present in the TCSC. The reactance of the TCSC will indirectly control the electrical power of the machine. This concept has been applied to a single machine infinite bus (SMIB) system.

Effect of electrical vehicle charging on power quality

Electric Vehicles(EVs) are a clean energy alternative to gas and energy powered vehicles. They form a crucial part of the present and future automotive. Electric vehicles being non-linear loads could affect the power quality of the grid. In this paper, we present a view of the fluctuations in power factor and Total Harmonic Distortion (THD) levels when varying number of electric vehicles (two wheeler and four wheeler) are connected to the power system. The system was simulated and studied in Simulink. Here, a captive power plant that is supplying power under base load and peak load conditions is considered.

Damping improvement using Dynamic Inversion technique in power system

In this paper, application of Dynamic Inversion (DI) controller for Thyristor Controlled Series Compensation (TCSC) in a Single Machine Infinite Bus (SMIB) system, has been presented. The performance evaluation of the controller is compared with that of cases for an SMIB system without any controller, with a proportional plus Integral (PI) controller and with fixed compensation. From the case study it is observed that the DI controller applied to TCSC gives excellent damping and also improves the transient stability.

Power system stability through nonlinear control of excitation

Dynamics of power system has always been an area of major concern. Transient and small signal stability during perturbed conditions is of utmost importance for a power system engineer. Whenever there is a disturbance, the rotor angle oscillates and the speed of the machine deviates from the original nominal speed. The perturbation can be of various types. It could be a variation in the load, loss of a line or a unit or it could be the changes in the infinite bus voltage. During such cases, a Flexible AC Transmission System (FACTS) device can be introduced in order to improve the performance of the machine in terms of its speed variation. In this paper, a single machine infinite bus system (SMIB) is considered for studying the performance of a nonlinear Technique called Dynamic Inversion. It has been proved in this paper that speed of the machine can be maintained at synchronous speed through excitation control. In DI technique, zero error dynamics is enforced and the actual output is forced to follow the desired output. The terminal voltage of the infinite bus is assumed to be varying at certain intervals. The speed and the rotor angle are observed. The speed is forced to follow the desired value (synchronous speed) by using DI technique. The results obtained for the rotor angle and the angular frequency (speed) are found to be promising.

Dynamic Inversion Technique for TCSC under varying voltage conditions

The requirement to improve power system stability is of utmost importance. Thyristor controlled series compensator (TCSC), which is a series compensating device, can be used to govern the power flow by compensating the reactance of the transmission line. It can also improve the system stability, sub-synchronous resonance mitigation, power oscillation damping and transient stability. Because of its advantage to damp out the oscillations, TCSC is a suitable device for stability improvement. In this paper, Dynamic Inversion (DI) technique has been used to control TCSC with an objective of improving stability and damping the oscillations arising out of the variation in the infinite bus voltage. DI technique is a non-linear technique wherein the zero error dynamic is enforced and the actual output is forced to follow the desired output.