Damping of Electromechanical Oscillations in Power Systems using Wide Area Control

The design of local H∞-based power system stabilizer (PSS) controllers, which uses widearea or global signals as additional measuring information from suitable remote network locations, where oscillations are well observable, is developed in this dissertation. The controllers, placed at suitably selected generators, provide control signals to the automatic voltage regulators (AVRs) to damp out inter-area oscillations through the machines’ excitation systems. A long time delay introduced by remote signal transmission and processing in wide area measurement system (WAMS), may be harmful to system stability and may degrade system robustness. Three methods for dealing with the effects of time delay are presented in this dissertation. First, time delay compensation method using lead/lag compensation along with gain scheduling for compensating effects of constant delay is presented. In the second method, Pade approximation approach is used to model time delay. The time delay model is then merged into delay-free power system model to obtain the delayed power system model. Delay compensation and Pade approximation methods deal with constant delays and are not robust regarding variable time delays. Time delay uncertainty is, therefore, taken into account using linear fractional transformation (LFT) method. The design of local decentralized PSS controllers, using selected suitable remote signals as supplementary inputs, for a separate better damping of specific inter-area modes is also presented in this dissertation. The suitable remote signals used by local PSS controllers are selected from the whole system. Each local PSS controller is designed separately for each of the inter-area modes of interest. The PSS controller uses only those local and remote input signals in which the assigned single inter-area mode is most observable and is located at a generator which is most effective in controlling that mode. The local PSS controller, designed for a particular single inter-area mode, also works mainly in a frequency band given by the natural frequency of the assigned mode. The locations of the local PSS controllers are obtained based on the amplitude gains of the frequency responses of the best-suited measurement to the inputs of all generators in the interconnected system. For the selection of suitable local and supplementary remote input signals, the features or measurements from the whole system are preselected first by engineering judgment and then using a clustering feature selection technique. Final selection of local and remote input signals is based on the degree of observability of the considered single mode in them. Finally, this dissertation presents the extension of the scheme, described in the above paragraph, to very large power systems. The suitable remote signals used by local PSS controllers are selected from the whole system. The approach uses system identification technique for deriving an equivalent lower order state-space linear model suitable for control design. An equivalent lower order system of the actual system is determined from time-domain simulation data of the latter. The time-domain response is obtained by applying a test probing signal (input signal), used to perturb the actual system, to the AVR of the excitation system of the actual system. The measured time-domain response is then transformed into frequency domain. An identification algorithm is then applied to the frequency response data to obtain a linear dynamic reduced order model which accurately represents the system. Lower-order equivalent models have been used for the final selection of suitable local and remote input signals for the PSS controllers, selection of suitable locations of the PSS controllers and design of the PSS controllers

Nonlinear coordinated excitation and TCPS controller for transient stability enhancement in power systems

The research work presented deals with the design of a robust nonlinear coordinated generator excitation and TCPS controllers to enhance the transient stability of power systems.Master of Engineerin

Heat Removal Under Various Wind Speeds

This paper investigated the impact of velocity variation in wide streets. The building AR (Aspect Ratio) (Street-canyon-width-to-building-height i.e. W/H) has been calculated by varying the width of street canyon. The k-? turbulence model was applied to ideal street canyons of aspect ratio 0.5, 0.75 and 1.0 while the wind speed was varied from 0.5 to 4.0 m/s. The street canyon aspect ratio 1.0 was obtained by increasing the width of the street two times (i.e. W=1) as much as for AR0.5 (i.e. W=0.5). However, different results obtained from AR1 were compared with AR0.5 to analyze the impact of wide streets. Results show that the temperatures reduce with an increase in ambient wind speed. However, the impact of ambient wind speed was comparatively higher in narrow street canyons since temperature reduced by over 1.4 K with an increase of 3.5 m/s in ambient wind speed. On the other hand, in the case of AR1.0 the area weighted average temperature reduced by 1.3 K with an increase of 3.5 m/s in ambient wind speed. It is found that removing heat from narrower street canyons is comparatively difficult. Results show that the temperatures within the target street canyon of AR0.5 with ambient wind speed of 0.5 m/s were around 0.71 K higher than that in AR1

Modeling the Effect of Wider Canyons on Urban Heating

The k-? turbulence model is adopted in this study to simulate the impact of street canyon AR (Aspect Ratios) on heating within street canyon. The two-dimensional model was validated for RANS (Reynolds Averaged Navier Stokes) and energy transport equations. The validation process confirms that the results of the model for airtemperature and wind speed could be trusted. The application of the said model is carried out to ideal street canyons of ARs (ratio of building-height-to-street-width) from 0.4 to 2 with the same boundary conditions. Notably, street canyon aspect ratio was calculated by varying the street width while keeping the building height constant. Results show that the weighted-average-air-temperature within AR 0.4 was around 0.8% (i.e. 2.4K) higher than that within AR 2.0. Conversely, there was strong correlation (i.e., R2>0.9) between air temperature within the street canyon and street canyon AR. Results demonstrate stronger influence of vertical velocity on heating within street canyon. Evidently, increased vertical velocity decreased the temperatures. Conversely, temperatures were higher along the leeward side of the canyon in lower ARs

Mode Selective Damping of Electromechanical Oscillations Using Supplementary Remote Signals and Design of Delay Compensator

The objective of this paper is to design an H?-based local decentralized PSS (Power System Stabilizing) controller. The controller is designed for separate damping of specific inter-area modes while considering time-delay. The controller uses remote signals, selected suitably from the whole system, as supplementary inputs. The wide area or global signals have been obtained where the oscillations in the remote network locations could be well observed. The PSS controller uses only those local and remote input signals in which the assigned single inter-area mode is most observable and is located at a generator which is most effective in controlling that mode. A long timedelay due to remote signal transmission and processing in WAMS (Wide Area Measurement System) can cause system instability and degradation of system robustness. Therefore, this paper uses the time-delay compensation method that uses lead or lag adjustment method while integrates the gain scheduling to overcome the impacts of constant time-delay. The effectiveness of the resulting PSS controllers is established through simulations using three machine three area test power system

Delayed-Input Wide Area Power System Stabilizer for Mode Selective Damping of Electromechanical Oscillations

A long time delay due to the transmission and processing of remote signal may degrade stability of power system. This paper discusses the design of H? -based local decentralized delayed-input PSS (Power System Stabilizer) controllers for a separate better damping of inter-area modes. The controllers use selected suitable remote signals from whole system as supplementary inputs. The local and remote input signals, used by the controller, are the ones in which the assigned single inter-area mode is most observable. The controller is located at a generator which is most effective in controlling the assigned mode. The controller, designed for a particular single interarea mode, also works mainly in the natural frequency of the assigned mode. Pade approximation approach is used to model time delay. The time delay model is then merged into delay-free power system model to obtain the delayed-input power system model. The controllers are then redesigned for the delayed-input system

Analysis and Mitigation of Shunt Capacitor Bank Switching Transients on 132 kV Grid Station, Qasimabad Hyderabad

In this paper analysis and mitigation methods of capacitor bank switching transients on 132KV Grid station, Qasimabad Hyderabad are simulated through the MATLAB software (Matrix Laboratory). Analysis of transients with and without capacitor bank is made. Mathematical measurements of quantities such as transient voltages and inrush currents for each case are discussed. Reasons for these transients, their impact on utility and customer systems and their mitigation are provided

Decentralized Hierarchical Controller Design for Selective Damping of Inter Area Oscillations Using PMU Signals

This paper deals with the decentralized hierarchical PSS (Power System Stabilizer) controller design to achieve a better damping of specific inter-area oscillations. The two-level decentralized hierarchical structure consists of two PSS controllers. The first level controller is a local PSS controller for each generator to damp local mode in the area where controller is located. This controller uses only local signals as input signals. The local signal comes from the generator at which the controller is located. The secondary level controller is a multivariable decentralized global PSS controller to damp inter-area modes. This controller uses selected suitable wide area PMU (Phasor Measurement Units) signals as inputs. The PMU or global signals are taken from network locations where the oscillations are well observable. The global controller uses only those global input signals in which the assigned single inter-area mode is most observable and is located at a generator that is most effective in controlling the assigned mode. The global controller works mainly in a frequency band given by the natural frequency of the assigned mode. The effectiveness of the resulting hierarchical controller is demonstrated through simulation studies conducted on a test power system

A Novel Method to Implement the Matrix Pencil Super Resolution Algorithm for Indoor Positioning

This article highlights the estimation of the results for the algorithms implemented in order to estimate the delays and distances for the indoor positioning system. The data sets for the transmitted and received signals are captured at a typical outdoor and indoor area. The estimation super resolution algorithms are applied. Different state of art and super resolution techniques based algorithms are applied to avail the optimal estimates of the delays and distances between the transmitted and received signals and a novel method for matrix pencil algorithm is devised. The algorithms perform variably at different scenarios of transmitted and received positions. Two scenarios are experienced, for the single antenna scenario the super resolution techniques like ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) and theMatrix Pencil algorithms give optimal performance compared to the conventional techniques. In two antenna scenario RootMUSIC and Matrix Pencil algorithm performed better than other algorithms for the distance estimation, however, the accuracy of all the algorithms is worst than the single antenna scenario. In all cases our devised Matrix Pencil algorithm achieved the best estimation results