Showing papers on "Electric power system published in 1984"

Power Generation, Operation, and Control

Abstract: Topics considered include characteristics of power generation units, transmission losses, generation with limited energy supply, control of generation, and power system security. This book is a graduate-level text in electric power engineering as regards to planning, operating, and controlling large scale power generation and transmission systems. Material used was generated in the post-1966 period. Many (if not most) of the chapter problems require a digital computer. A background in steady-state power circuit analysis is required.

Bibliography on the Application of Probability Methods in Power System Reliability Evaluation 1996-1999

Abstract: This paper presents a bibliography of papers on the subject of power system reliability evaluation. Papers in such areas as: probabilistic load flow, probabilistic production costing, probabilistic transient stability evaluation, etc. have not been included except where they specifically address power system reliability evaluation. It includes material which has become available since the publication of the four previous papers. 'Bibliography on the Application of Probability Methods in Power System Reliability Evaluation', IEEE Trans. On Power Apparatus and Systems PAS-91, 1972, p.649-660; PAS-97, 1978, p.2235-2242; PAS-103, 1984, p.275-282 and IEEE Trans. On Power Systems, vol.3, no.4,p.1555-1564, 1984. The authors have endeavored to include papers which are readily archival on an international basis. Consequently, the proceedings of such conferences as: CIGRE, Inter-RAM, PMAPS, etc. are regretfully not included. Due to space constraints, only papers written in English were considered for inclusion in this bibliography. >

Optimal pricing in electrical networks over space and time

Abstract: An electrical system is modelled with a transmission network, customers, central generators, and independent generators. The system is subject to stochastic failures and stochastic demand parameters. Optimal spot prices are derived for the system. They vary stochastically with space and time, and depend on electrical load flow patterns. The price difference between two locations or two voltage levels, and the wheeling charge between them, will change magnitude and sometimes sign over time, as a function of events throughout the network. Current spatial pricing methods are significantly different from the spot-price-based methods derived here.

Combined-Cycle System With Novel Bottoming Cycle

Abstract: A new thermodynamic energy cycle has been developed using a multicomponent working agent. This cycle is designed to replace the currently used Rankine Cycle as a bottoming cycle for a combined-cycle energy system as well as for generating electricity using low-temperature heat sources. Several combined power systems based on this cycle have been designed and cost-estimated. The efficiency of this cycle is from 1.6 to 1.9 times higher than that of the Rankine Cycle system, at the same border conditions. The investment cost per unit of power output for this cycle is lower than that for the Rankine Cycle system in approximately direct proportion to the energy advantage. The application of this cycle as a bottoming cycle in combined-cycle systems involves the use of an energy system which utilizes heat from the exhaust of a gas turbine, resulting in an increase in overall efficiency of up to 20 percent above the efficiency of the combined systems using the Rankine bottoming cycle. As a result, a thermal efficiency in the range of 50–52 percent can be achieved using a conventional gas turbine. The project to build the first experimental installation is now in progress. This installation is to become operational at the end of 1984.

Fuel-cost minimisation for both real-and reactive-power dispatches

Abstract: The fuel cost formula is developed for optimal real-and reactive-power dispatch for the economic operation of power systems The problem is decomposed into a P-optimisation and a Q-optimisation module, where both modules use the same fuel cost objective function resulting in the optimal load flow The control variables are generator real-power outputs for the real-power module; and generator reactive-power outputs, shunt capacitors/reactors and transformer tap settings for the reactive-power module The constraints are the operating limits of the control variables, power-line flows and busbar voltages The optimisation problem is solved using the gradient projection method (GPM) for the quadratic objective function and linear constraints The GPM allows the use of functional constraints without the need of penalty functions or Lagrange multipliers among other advantages Mathematical models are developed to represent the sensitivity relationships between dependent and control variables for both real- and reactive-power optimisation modules; and thus eliminate the use of B-coefficients Results of two test systems are presented and compared with conventional methods

Power System Stabilizer Based on Adaptive Control Techniques

Abstract: Characteristics of certain adaptive control techniques are discussed in this paper with particular emphasis on their application to power systems. A modified form of one of the more promising algorithms that makes it more suitable. for power systems is developed and described. Comparative results of studies with adaptive stabilizer based on two alternate adaptive control algorithms and a conventional fixed parameter stabilizer show the improvement in response obtained with the adaptive algorithm.

Hinge clamp for securing a sensor module on a power transmission line

Abstract: Self contained radio transmitting state estimator modules are mounted on power conductors on both sides of power transformers in electrical substations and on power conductors at various places along electrical transmission lines. They are electrically isolated from ground and all other conductors. These modules are capable of measuring current, voltage, frequency and power factor (or the fourier components thereof) the temperature of the conductor, and the temperature of the ambient air. The modules transmit these parameters to local receivers. The receivers are connected by an appropriate data transmission link, to a power control center which allows determination of the state of the power system. Appropriate control signals are transmitted back to the electrical switchgear of the system to bring it to the appropriate optimum state. Direct local control may also be effected, for example, the prevention of overloading a transformer. A "donut" state estimator module comprises a novel hot stick operated hinge clamp and a novel voltage sensor which measures the current between an isolated capacitor plate and ground. The donut measures the fourier components of voltage and current over a number of cycles and transmits the components to the local receiver. The local receiver derives the desired electrical measurements such as voltage, current, power factor, power, and reactive power and transmits them to local or remote control stations. Up to 15 donut modules may transmit on a single channel to a single local receiver. Each transmits at intervals which are an integral number. The intervals between transmissions of all donuts do not have a common factor and the average interval is the desired transmission rate. Each donut uses the zero crossover of current of its conductor to establish its transmission interval. The system is self-calibrating using known reference signals within the donut module.

Design of variable-structure load-frequency controller using pole assignment technique

Abstract: This paper presents a new technique for designing the variable structure load-frequency controller for a single-area power system. The variable-structure controller effectively enhances the dynamic performance of the integral controller which ia usually designed with the primary aim of zero steady-state error. Further, when the variable-structure system is operated in the so-called sliding mode, the response of the system becomes insensitive to changes in the plant parameters. The control problem is formulated and the results of a simulation study are presented for illustration.

Probabilistic Load Flow Considering Dependence Between Input Nodal Powers

Abstract: This paper presents a new method for obtaining a probabilistic load flow solution when dependence between the input nodal powers is considered. Such dependence is modeled in order to account for the criteria used to balance the system active power and also the correlation between loads due-mainly to environmental and social factors. The proposed technique is applied to a typical power system and the results discussed.

Application of a Thyristor Controlled Var Compensator for Damping Subsynchronous Oscillations in Power Systems

Abstract: This paper presents a new concept for controlling static VAr compensators (SVC) in power systems. It allows thyristor controlled VAr compensators to effectively damp subsynchronous resonance (SSR) oscillations besides controlling the system voltage. Eigenvalue analysis and digital time simulations for the IEEE SSR benchmark system are utilized to investigate the role of the main voltage regulator of the SVC in stabilizing the system and alleviating the SSR modal interactions that may be introduced by the auxiliary speed signal alone. Stability zones are identified to optimize the compensator parameters for economical application.

Bound Estimates of the Severity of Line Outages in Power System Contingency Analysis and Ranking

Abstract: The effect of line outages on the real power flows of a system is analyzed using the DC load flow model. It is shown that the effect of the out4ge of line jk on the power flow of an arbitrary line lm can be bounded above and below by a series of progressively tighter values which in the limit correspond to the exact DC load flow solution. The calculation of these bound estimates on the contingency line flows is progressively more computationally demanding as the limits tighten, however, the simple to compute bounds, although more conservative, still serve to filter out a large portion of the non-critical contingencies. The remaining few potentially critical outages can then be ranked and analyzed through the full DC load flow.

System and apparatus for monitoring and control of a bulk electric power delivery system

Abstract: Self contained radio transmitting state estimator modules are mounted on power conductors on both sides of power transformers in electrical substations and on power conductors at various places along electrical transmission lines. They are electrically isolated from ground and all other conductors. These modules are capable of measuring current, voltage, frequency and power factor (or the Fouier components thereof), the temperature of the conductor and the temperature of the ambient air. The modules transmit these parameters to local receivers. The receivers are connected by an appropriate data transmission link to a power control center which allows determination of the state of the power system. Appropriate control signals are transmitted back to the electrical switchgear of the system to bring it to the appropriate optimum state. Direct local control may also be effected, for example, the prevention of overloading a transformer.

A generalized energy function for transient stability analysis of power systems

Abstract: In this paper, an "energy function" is derived for transient stability analysis of power systems. The main contribution of this paper is the generality of the model for the loads. The loads are modeled as constant real power loads but the reactive part of the loads are modeled as arbitrary function of the load bus voltage. This model accounts for the voltage transients of the load busses and for this general model, it is shown that the system satisfies the law of conservation of energy. An efficient algorithm for determining the stability of the system for a given disturbance is described. Results of simulation of the system studied by El-Abiad and Nagappan [2] are included and it is shown that due to the fluctuations in the system voltages, the commonly used energy function over estimates the energy of the system during system transients.

Critical Energy for Direct Transient Stability Assessment of a Multimachine Power System

Abstract: This paper describes a criterion for determining the critical energy used in direct transient stability assessment of a multimachine power system using the transient energy function method. This criterion provides a method by which the controlling unstable equilibrium point (u.e.p.), for the disturbance under investigation, is identified.

Uninterruptible power system.

Abstract: In power systems for providing an uninterruptible power supply to a load (24), a problem may arise in the switching of power from a main line (12) to a standby generator (20). A power system that overcomes the above problem further includes a first motor (14), a first generator (16), a flywheel (62) and a transfer controller (92). When the main line (12) fails to provide the necessary power, the energy developed by flywheel (62) is used to supply power to a load (24) until a standby generator (20) is available to supply power. The power system can be used with a three phase 240 voltage load (24).

Passive signal coupler between power distribution systems for the transmission of data signals over the power lines

Abstract: A passive signal coupler transfers data signals being transmitted over AC power lines from a first AC power distribution system to a second AC power distribution system. Each leg of the passive signal coupler coupled to a phase of the power line voltage includes a series LC circuit, tuned to the data signal carrier frequency. Each leg coupled to the first power system is terminated in a first winding of a transformer. Each leg coupled to the second power system is terminated in a second winding of the transformer.

Modeling and Analysis of Under-Load Tap-Changing Transformer Control Systems

Abstract: This paper considers the problem of modeling and analysis of under-load tap-changing (ULTC) transformer control systems. A nonlinear system model is derived, suitable for analysis of voltage and reactive power flow control applications of ULTC transformers in the consideration of mid-term and long-term dynamics and steady-state behavior of power systems. The model is verified with the example of a distribution ULTC transformer, used for the voltage control. As an illustration of the feasibility of the model in various voltage and reactive flow control applications, some digital simulation results of such a distribution voltage control are also presented.

Coordinated Synthesis of Power System Stabilizers in Multimachine Power Systems

Abstract: A new coordinated synthesis method of applying power system stabilizers (PSS) was developed by combining eigenvalue sensitivity analysis and linear programming. This method is simultaneously able to select the generators to which the PSS can be effectively Applied and to synthesize the adequate transfer functions of the PSS for these generators. The proposed itethod is used to synthesize the coordinated PSS for a 12-machine system.

Controls for Variable Pitch Wind Turbine Generators

Abstract: This paper analyzes the control requirements of wind turbine generators connected to electric power systems. The requirements are based on stand-alone as well as interconnected operation. Control systems are developed for wind turbines with synchronous, induction, and doubly-fed generators. Results of detailed, non-linear time response simulation are presented.

Coordinated Stabilization of a Multimachine Power System

Abstract: The paper presents a sequential procedure for coordinated stabilization of a multimachine power system with arbitrary complexity of the system model. The most effective machine to be equipped with a power system stabilizer is identified using eigenvalue analysis. The selection is based on the sensitivity of critical eigenvalues to increases in the coefficient of a damping term which is inserted in each equation of motion, in succession. The method is applied to a three-machine system and simulation studies show appreciable improvements in the small disturbance stability of the system.

Electric Distribution Protection Problems Associated with the Interconnection of small, disperesed Generation Devices

Abstract: This paper discusses the results of simulating three potential protection problems associated with the interconnection of rotating-type, small dispersed storage and generation (DSG) devices to the electric distribution system. These simulations were performed as part of a study to address the-adequacy of the electric utility industry's present protection practices and hardware for distribution systems with DSG. The simulations considered phenomena such as the effect of dispersed generati, on infeed on the coordination of fuses, resonance of an isolated section of feeder with a three-phase DSG device, and the islanding of a DSG device on an isolated feeder. The phenomena were simulated for a 12. 47 kV feeder with DSG. A digital computer program was used to calculate the transient currents and voltages produced on the feeder for the three types of phehomena. Results of the simulations indicate that these are concerns which should be considered by electric utilities in the connection of dispersed generation sources to the electric distribution system.

Improved load-frequency self-tuning regulator

Abstract: A self-tuning regulator is used as a local area controller for interconnected power systems. The area control error, composed of the area frequency error and the total tie-line power deviation for the area, is used as the regulator input variable. By changing the relative weights on the frequency error and on the tie-line power deviation according to their respective variances, it is possible to approach the minimum variances of the individual variables. The proposed regulator can handle unpredicable load changes of random magnitude and duration. Studies on a two-area power system show that with this regulator the system performance is improved over that with the traditional type of load-frequency controller. Because only locally available measurements are required for each area controller, the proposed regulator can be implemented easily using microprocessors.

Excitation Control of Synchronous Generators Using Adaptive Regulators Part I-Theory and Simulation Results

Abstract: A recent trend in power system operation is towards computerised control and management. One class of digital adaptive regulators called self- tuning regulators is suitable for this purpose. In synchronous generator control a conflict arises between the small sampling interval necessary to track the dynamics and large computation time required by the process computer. A dual-rate sampling model is suggested to alleviate this problem. A class of self-tuning regulators called Dual-rate Sampling Self-Tuning regulators which use a dual-rate sampling model of the power system are described in this paper. Simulation results obtained are used to evaluate the merits, usefulness and viability of the proposed regulator.

Transmission System Expansion Planning by Interactive Methods

Abstract: The objective of any electric utility is to ensure that within a planning horizon, the future load demand is satisfied at a reliable level of performance. A sensitivity-based approach is used to determine the locations of network additions comprising new generation lines and the possibility of a phase-shifter to reinforce a heavily loaded a.c. system. The security of the new system is evaluated using qualitative and quantitative methods with further line additions if necessary. Tests carried out on the IEEE 24-bus reliability system are presented.

Application of Direct Methods to Transient Stability Analysis of Power Systems

Abstract: This paper is an evaluation of the applicability of the direct methods to transient stability analysis of power systems. Recent advances in these techniques have significantly enhanced the accuracy and reliability of these methods. The Power System Engineering Committee has recently sponsored two panel sessions to discuss the state of the art in terms of its practical applications. This paper presents this evaluation by the panel members as a collection of mini-papers. These mini-papers have been edited to form a coherent collection without altering the thrust of each viewpoint.

Optimal Reactive Power Allocation for Improved System Performance

Abstract: This paper presents a fast converging method for finding the optimal capacitor allocation in a power system for minimising power losses and for improving the quality of the supply system which is achieved by optimal allocation of all reactive power sources in the system in a co-ordinated way. The problem is formulated as a Mixed Integer Linear Programming problem and is solved by decomposing it into two smaller subproblems. The method has very fast convergence without zigzagging of the solution about the optimal point. The potential of the model has been demonstrated by its application to sample systems.

A Sparsity-Based Technique for Identifying Slow-Coherent Areas in Large Power Systems

Abstract: A sparsity-based technique is developed for the identification of coherent areas in large power systems The technique, based on the slow-coherency approach, is novel in that it introduces small machines at the load buses to retain the system sparseness Then the computation of the slow eigenbasis for the identification of slow-coherent groups of machines is performed by the Lanczos algorithm which is an efficient eigenfunction computation method for large, sparse, symmetric but unstructured matrices The technique also groups the load buses into coherent areas, information that is useful for network reduction Two large scale models of portions of the US power system are used as illustrations The computation time required is of the order of magnitude of that required for a few load flow solutions

Wind Turbine Generator Interaction With Diesel Generators on an Isolated Power System

Abstract: The Block Island Power Company (BIPCO), on Block Island, Rhode Island, operates an isolated electric power system consisting of diesel generation and an experimental wind turbine. The 150-kW wind turbine, designated MOD-OA by the U. S. Department of Energy is typically operated in parallel with two diesel generators to serve an average winter load of 350 kW. As part of an experimental program to evaluate wind turbine generator performance on the isolated diesel power system, the recordings from an extensive data measurement effort were reviewed and analyzed to define the nature of the dynamic interaction effects. The data were collected over a three-month period on the system to which the DOE/NASA experimental wind turbine was connected. During this time, the diesel units were lightly loaded resulting in up to 60 percent of the total load demand being supplied by the MOD-OA in periods of severely gusting winds. In three of the modes of normal MOD-OA operation. startup???synchronization, shutdown/cutout, and continuous fixed pitch running???power, frequency and voltage transients were comparable with those produced by typical load changes on the diesel system alone. In the fourth mode, variable pitch (constant power) control, a significant reduction in system damping sometimes occurred which gave rise to increased frequency and voltage perturbations under gusty wind conditions. Based on a linear model of the system it is shown that changes in control system settings could be made to improve damping.

On the existence of energy function for power systems with transmission losses

Abstract: In this paper we show that any energy (Lyapunov) function to analyze the stability of equilibrium points of systems with transmission losses would, in general, not be a continuous (with respect to transmission losses) deformation of the standard energy function used for a lossless system. This result implies that stability analysis using Lyapunov functions for systems with losses would require Lyapunov functions that are substantially different from the energy function used for lossless systems.