scispace - formally typeset
Search or ask a question

Showing papers on "Electric power system published in 1993"


Book
01 Dec 1993
TL;DR: In this article, a clear, in-depth explanation of voltage stability, covering both transient and longer-term phenomena and presenting proven solutions to instability problems, is presented, along with planning and operating guidelines, computer methods for power flow and dynamic simulation, and descriptions of actual voltage instability incidents.
Abstract: Voltage stability is a major concern in the planning and operation of electric power systems. This book provides a clear, in-depth explanation of voltage stability, covering both transient and longer-term phenomena and presenting proven solutions to instability problems. The book describes equipment characteristics for transmission, generation, and distribution/load subsystems of a power system, together with methods for the modelling of equipment. Readers will find static and dynamic computer simulation examples for small equivalent power systems and for a very large power system, plus an account of voltage stability associated with HVDC links. They will also get helpful planning and operating guidelines, computer methods for power flow and dynamic simulation, and descriptions of actual voltage instability incidents.

1,355 citations


Journal ArticleDOI
TL;DR: The flexible AC transmission system (FACTS) as mentioned in this paper is designed to overcome the limitations of the present mechanically controlled AC power transmission systems, uses reliable, high-speed power electronic controllers.
Abstract: The operation and components of the flexible AC transmission system (FACTS) are described. FACTS, designed to overcome the limitations of the present mechanically controlled AC power transmission systems, uses reliable, high-speed power electronic controllers. Its benefits are examined. These include greater control of power, so that it flows on the prescribed transmission routes; secure loading of transmission lines to levels nearer their thermal limits; greater ability to transfer power between controlled areas, so that the generation reserve margin may be reduced; prevention of cascading outages by limiting the effects of faults and equipment failure; and damping of power system oscillations. >

655 citations


Journal ArticleDOI
TL;DR: In this article, the implementation of both point of collapse (PoC) and continuation methods for the computation of voltage collapse points (saddle-node bifurcations) in large AC/DC power systems is described.
Abstract: The implementation of both point of collapse (PoC) methods and continuation methods for the computation of voltage collapse points (saddle-node bifurcations) in large AC/DC power systems is described. The performance of these methods is compared for real systems of up to 2158 buses. Computational details of the implementation of the PoC and continuation methods are detailed, and the unique problems encountered due to the presence of high-voltage direct-current (HVDC) transmission, area interchange power control, regulating transformers, and voltage and reactive power limits are discussed. The characteristics of a robust PoC power flow program are presented, and its application to detection and solution of voltage stability problems is demonstrated. >

614 citations


Journal ArticleDOI
TL;DR: In this paper, the use of static voltage stability indices based on a singular value decomposition of the power flow Jacobian matrix and matrices derived from the Jacobian matrices is discussed.
Abstract: The use of static voltage stability indices based on a singular value decomposition of the power flow Jacobian matrix and matrices derived from the Jacobian matrix is discussed. It is shown that such indices, together with the singular vectors, contain substantial and important information about the proximity to voltage instability and also about critical buses and disturbances from a voltage instability point of view. This is done by a theoretical analysis of the linear power flow equations and an analysis from model power systems as well as realistic power systems (1033 nodes). It is argued that indices based on these matrices are useful for the system analyst in planning and operations planning. >

377 citations


Journal ArticleDOI
TL;DR: In this paper, a new controller for the generator excitation system is described that uses a combination of feedback linearizing and the observation decoupled state space, which can be realistically implemented using only local measurements, and whose performance is consistent with respect to changes in network configuration, loading and power transfer conditions.
Abstract: A new controller for the generator excitation system is described that uses a combination of feedback linearizing and the observation decoupled state space. This creates a controller that can be realistically implemented using only local measurements, and whose performance is consistent with respect to changes in network configuration, loading and power transfer conditions. The control differs in this respect from linear constant-gain controllers such as power system stabilizers, whose characteristics can vary significantly with changes in operating conditions. The design is well-suited to a multimachine setting, in that it is not based on an infinite-bus approximation. Simulations were performed on a 38-bus reduced modelof the Northeast Power Coordinating Council system and benchmarked against simulations in which automatic voltage regulators with power system stabilizers were substituted in place of the nonlinear controls. >

363 citations


Journal ArticleDOI
TL;DR: In this paper, the instantaneous power theory was introduced for steady and transient states and for generic voltage and current waveforms, and an example showing how this theory can be used to design and control an active power filter is presented.
Abstract: Conventional active and reactive power theory, valid for the steady-state analysis is reviewed. The instantaneous power theory, introduced by H. Akagi et al. (1983, 1984) is also presented. This instantaneous theory is valid for steady and transient states and for generic voltage and current waveforms. Some examples explaining the physical meaning of the new concepts are presented. By using the concepts of symmetrical components together with the new theory, the powers in an unbalanced system are analyzed, including the zero-sequence instantaneous power. An example showing how this theory can be used to design and control an active power filter is presented. Some simulation results are presented and discussed. >

361 citations


Journal ArticleDOI
TL;DR: In this paper, the relations between currents, voltages and power quantities are analyzed in the time domain using the FBD method and treatment in the frequency domain on the basis of Fourier series expansion of the time functions is also possible.
Abstract: Starting from the most general case of m-wire unbalanced multiphase power systems with unsymmetrical loads under nonsinusoidal conditions, it is explained how the relations between currents, voltages and power quantities are analyzed in the time domain using the FBD method. Treatment in the frequency domain on the basis of Fourier series expansion of the time functions is also possible. It is shown that components of the total nonactive currents may be compensated without any time delay and without changing the collective instantaneous power. Rules are given for deriving simple equivalent circuits with m-equally structured branches from given voltages and currents. >

354 citations


Journal ArticleDOI
G.K. Morison1, B. Gao1, P. Kundur1
TL;DR: In this article, the authors discuss voltage stability analysis of power systems using static and dynamic techniques, using a small test system, results of time domain simulations are presented to clarify the phenomenon of voltage instability and to better understand modeling requirements.
Abstract: The authors discuss voltage stability analysis of power systems using static and dynamic techniques. Using a small test system, results of time domain simulations are presented to clarify the phenomenon of voltage instability and to better understand modeling requirements. The same system is then analyzed using a static approach in which modal analysis is performed using system conditions, or snapshots, which approximate different stages along the time domain trajectory. The results obtained using the dynamic and static methods are compared and shown to be consistent. >

347 citations


Journal ArticleDOI
TL;DR: In this paper, the transient stability and voltage regulation of a single-machine-infinite-bus power system under the effects of a symmetrical three-phase short-circuit fault is detailed.
Abstract: Improvement of the transient stability and voltage regulation of a single-machine-infinite-bus power system under the effects of a symmetrical three-phase short-circuit fault is detailed. The dynamical model of the system is described. A design strategy for nonlinear controllers is considered, and the design of a nonlinear variable-structure excitation controller is described. Simulation results obtained using the nonlinear excitation controller are given, and a new nonlinear coordinated controller is proposed. Simulation results obtained by using the nonlinear coordinated controller are presented. >

310 citations


Journal ArticleDOI
TL;DR: In this paper, a static VAr generator (SVG) using self-commutated inverters of 80 MVA capacity was developed and successfully applied to an annual 154 KV power system to stabilize the power system.
Abstract: A static VAr generator (SVG) using self-commutated inverters of 80 MVA capacity was developed and successfully applied to an annual 154 KV power system to stabilize the power system. The SVG consists of 48 pulse multiple inverters whereby gate turn-off (GTO) thyristors are applied. After installing it at a power system site, a field test was conducted to confirm the system stabilizing effect. The test results displayed the expected performance, and the SVG was proven to be effective power system stabilizer. The outline of the 80 MVA SVG, technical features, and the test results are described. >

309 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed new iterative and direct methods to compute load powers at which bifurcation occurs and which are locally closest to the current operating load powers.
Abstract: Voltage collapse and blackout can occur in an electric power system when load powers vary so that the system loses stability in a saddle node bifurcation. The authors propose new iterative and direct methods to compute load powers at which bifurcation occurs and which are locally closest to the current operating load powers. The distance in load power parameter space to this locally closest bifurcation is an index of voltage collapse. The pattern of load power increase need not be predicted; instead the index is a worst case load power margin. The computations are illustrated in the six-dimensional load power parameter space of a five bus power system. The normal vector and curvature of a hypersurface of critical load powers at which bifurcation occurs are also computed. The sensitivity of the index to parameters and controls is easily obtained from the normal vector. >

Journal ArticleDOI
TL;DR: In this paper, the requirements of an islanding, or "loss of grid", protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined.
Abstract: The requirements of an islanding, or 'loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system. >

Journal ArticleDOI
TL;DR: The impact of electric vehicle charging on the energy and power demand is determined not only by the number of electric vehicles (EVs) in use and their usage pattern, but also by the charging profile of the battery module as discussed by the authors.
Abstract: The impact of electric vehicle charging on the energy and power demand is determined not only by the number of electric vehicles (EVs) in use and their usage pattern, but also by the number of EVs being charged at an instant and the charging profile of the battery module. Case studies that reveal several important issues regarding the impacts EV load may have on utility distribution systems are examined. First, it is not adequate to have only sufficient generation capacity during off-peak hours to assure a system's ability to absorb EV loads without adverse effects. The constraints at the distribution level must be properly studied. Second, a sizable EV load can introduce a new peak in the early off-peak period. This may have scheduling implications and can completely throw any load management programs off balance. Third, at the present state of EV technology, including that of battery modules and chargers, a typical distribution system may not be able to supply EV loads beyond 20% penetration level. This constraint is created by the long (up to 12 hours) charging cycle of batteries. >

Journal ArticleDOI
TL;DR: In this article, the effects of a 30 MW battery on the frequency regulation in the isolated power system were quantified on a single area model representing the whole power system and containing a first order transfer function that represented the BES performance.
Abstract: Large battery energy storage (BES) facilities may provide significant dynamic operation benefits for electric utilities. One area in which a BES facility could be useful is the frequency regulation requirement. This feature is significantly important for island power systems. The purpose of this paper is to quantify the effects of a 30 MW battery on the frequency regulation in the Israeli isolated power system. The study was performed on a single area model representing the whole power system and containing a first order transfer function that represented the BES performance. >

Journal ArticleDOI
01 Jan 1993
TL;DR: In this paper, a robust controller based on the Riccati-equation approach is proposed for power system load-frequency control, which is simple, effective and can ensure that the overall system is asymptotically stable for all admissable uncertainties.
Abstract: A robust controller, based on the Riccati-equation approach, is proposed for power system load-frequency control. Only the bounds of the system parameters are required to design the robust load-frequency controller. The proposed robust controller is simple, effective and can ensure that the overall system is asymptotically stable for all admissable uncertainties. Simulation results show that, for the example system, the proposed robust load-frequency controller can achieve good performance even in the presence of generation rate constraint.

Journal ArticleDOI
TL;DR: In this article, a methodology for expansion planning of power systems under uncertainty in factors such as demand growth, fuel cost, delay in project completion, and financial constraints is described, and case studies within the Brazilian system are presented.
Abstract: A methodology is described for expansion planning of power systems under uncertainty in factors such as demand growth, fuel cost, delay in project completion, and financial constraints The approach draws upon three classes of techniques: decomposition and stochastic optimization provide the basic framework, and allow an implicit representation of alternative investment strategies; decision analysis is used to represent the dynamic aspects of decision-making as uncertainties are resolved over time; and hedging objectives from tradeoff analysis help select flexible and resilient expansion strategies. Case studies within the Brazilian system are presented and discussed. >

Journal ArticleDOI
TL;DR: In this paper, a theory for analyzing power system damping enhancement by application of static VAr compensators (SVCs) has been developed using the equal area criterion, where the SVC reactive power output at discrete points is determined from the power deviation on a transmission line.
Abstract: A theory for analyzing power system damping enhancement by application of static VAr compensators (SVCs) has been developed using the equal area criterion. Some fundamental issues, such as the effect of SVCs on a power system, how to control an SVC to improve system damping, and the differences between continuous and discontinuous control of SVC reactive power to achieve the maximum damping improvement, are discussed. A discontinuous SVC reactive power output at discrete points is determined from the power deviation on a transmission line. Time-domain simulations of the application of this approach to a one-machine system to increase swing oscillation damping and to a four-machine system to increase the damping of an interarea oscillation mode demonstrate that the theory and method can be applied to solve practical power system damping problems. >

Journal ArticleDOI
TL;DR: In this article, power flow control in electric power systems by use of controllable series power capacitors and phase shifters is discussed and models suitable for incorporation in power flow programs are developed and analyzed.
Abstract: Power flow control in electric power systems by use of controllable series power capacitors and phase shifters is discussed. Models suitable for incorporation in power flow programs are developed and analyzed. The power flow control problem is defined in a stringent way, and a method for solving the power flow control problem is proposed based on decomposition. This method is applied on test systems and the convergence rate of the algorithm is discussed. Simplified models of the components are also derived. These simplified models are shown to be quite accurate in most situations, and are used to construct regions of feasible power flows of the controlled lines. >

Journal ArticleDOI
TL;DR: In this paper, an artificial neural network (ANN)-based power system stabilizer (PSS) and its application to power systems is presented, which combines the advantages of self-optimizing pole shifting adaptive control strategy and the quick response of ANN to introduce a new generation PSS.
Abstract: An artificial neural network (ANN)-based power system stabilizer (PSS) and its application to power systems are presented. The ANN-based PSS combines the advantages of self-optimizing pole shifting adaptive control strategy and the quick response of ANN to introduce a new generation PSS. A popular type of ANN, the multilayer perceptron with error backpropagation training method, is used in this PSS. The ANN was trained by the training data group generated by the adaptive power system stabilizer (APSS). During the training, the ANN was required to memorize and simulate the control strategy of APSS until the differences were within the specified criteria. Results show that the proposed ANN-based PSS can provide good damping of the power system over a wide operating range and significantly improve the dynamic performance of the system. >

Journal ArticleDOI
TL;DR: In this article, an improved real and reactive power control technique using linear programming (LP) for an integrated power system is developed, where the real power generation, voltage magnitude, and transformer tap settings are optimized using a unified approach.

Journal ArticleDOI
Abstract: This paper introduces a decentralized control scheme for the parallel connection of multiple rectifiers feeding a DC network with numerous inverters. The coordination of multiple HVDC power systems without explicit communication is accomplished by the use of DC-side voltages as a "droop" mechanism. The DC side voltage serves the role of frequency in an ordinary AC system. The approach is most suitable to superconducting DC systems and to DC systems that span small distances and where voltage is relatively uniform throughout the DC system. This paper presents the concept in the context of a high capacity superconducting 10 kV urban infeed. >

Journal ArticleDOI
TL;DR: In this article, a tool based on the determination of critical modes is proposed to determine the most suitable sites for system reinforcement in the vicinity of the point of collapse, which does not rely on base case linearizations.
Abstract: The location of SVC (static VAr compensators) and other types of shunt compensation devices for voltage support is an important practical question. This paper considers a tool based on the determination of critical modes. Critical modes are computed by studying the system modes in the vicinity of the point of collapse. System participation factors for the critical mode are used to determine the most suitable sites for system reinforcement. Because the method does not rely on base case linearizations, the method is able to properly consider all system limits and nonlinear effects. The paper tests the proposed method by performing an assessment of the impact of the addition of static VAr compensators to a 1380 bus model of the BC Hydro system. >

Journal ArticleDOI
TL;DR: In this paper, a model for short-term operation planning for a hydrothermal power system is supplemented with a wind power model and the results include an estimation of whether there is a deficit or excess of instantaneous, fast, or slow reserves during each hour of the planning period.
Abstract: A method for studying the effect of wind power on power system reserve margins, need of extra resources, etc. is presented. A conventional model for short-term operation planning for a hydrothermal power system is supplemented with a wind power model. The wind power model includes the forecast of total wind power generation and the uncertainty of the forecast. The conventional hydro-thermal model is extended to take into account load forecast uncertainty and reserve margins of the generation units. The requirements of instantaneous, fast, and slow reserves, depending on possible forced outages of thermal units and uncertain load and wind speed forecasts etc., are calculated together with the available capacities of the corresponding reserve type. The results include an estimation of whether there is a deficit or excess of instantaneous, fast, or slow reserves during each hour of the planning period. A numerical example shows an application of the method to the Swedish power system. >

Journal ArticleDOI
TL;DR: In this paper, the development of dynamic load models using the measurement approach for the Taipower system is described. But the authors focus on the use of the measured data from an online transient recording system to develop dynamic load model structures.
Abstract: Accurate dynamic load models allow more precise calculations of power system controls and stability limits, which are critical in the planning and operation of power systems. The development of dynamic load models using the measurement approach for the Taipower system are described. Two dynamic load model structures are developed. A procedure for applying a set of measured data from an online transient recording system to develop dynamic load models for the Taipower system is described. A technique based on the concept of confidence interval is used to validate the developed high-order load model structure. Case studies are also presented. >

Patent
05 May 1993
TL;DR: In this paper, a multicell battery power system for providing power to a load is described, which consists of a plurality of battery modules and a power bus for transmitting power between the battery module and the primary load, each of which includes a battery for providing electrical power and connection circuitry for connecting the battery to the power bus.
Abstract: A multicell battery power system for providing power to a load is disclosed. The battery power system includes a plurality of battery modules and power bus for transmitting power between the battery modules and the primary load. Each of the battery modules includes a battery for providing electrical power and connection circuitry for connecting the battery to the power bus. The battery modules each include circuitry for monitoring the power output and status of the battery means. Each battery module also includes a programmable battery controller for controlling the operation of the battery and the connection circuitry. The battery controller is programmably responsive to the power monitoring circuitry, and in an illustrated embodiment is also be responsive to a system power controller or to one or more other battery modules. A battery charger may also be included in each module to provide programmably controlled individual recharging of batteries by module.

Journal ArticleDOI
TL;DR: In this article, a short-term hydro generation optimization program was developed by the Hydro Electric Commission (HEC) to determine optimal generation schedules and to investigate export and import capabilities of the Tasmanian system under a proposed DC interconnection with mainland Australia.
Abstract: This paper describes a short term hydro generation optimization program that has been developed by the Hydro Electric Commission (HEC) to determine optimal generation schedules and to investigate export and import capabilities of the Tasmanian system under a proposed DC interconnection with mainland Australia. The optimal hydro scheduling problem is formulated as a large scale linear programming algorithm and is solved using a commercially-available linear programming package. The selected objective function requires minimization of the value of energy used by turbines and spilled during the study period. Alternative formulations of the objective function are also discussed. The system model incorporates the following elements: hydro station (turbine efficiency, turbine flow limits, penstock head losses, tailrace elevation and generator losses), hydro system (reservoirs and hydro network: active volume, spillway flow, flow between reservoirs and travel time), and other models including thermal plant and DC link. A valuable by-product of the linear programming solution is system and unit incremental costs which may be used for interchange scheduling and short-term generation dispatch. >

Journal ArticleDOI
05 Sep 1993
TL;DR: In this paper, a method is proposed to identify the set of buses where load restoration is responsible for the voltage collapse and to determine the corresponding corrective actions, which is implemented in a fast voltage stability simulator, using sensitivity techniques.
Abstract: This paper deals with the diagnosis of power system voltage collapse situations, following large disturbances and/or load increases. A method is proposed to identify the set of buses where load restoration is responsible for the collapse and to determine the corresponding corrective actions. It has been implemented in a fast voltage stability simulator, using sensitivity techniques. Tap changer blocking and load shedding are illustrated on a real-life 410-bus system. >

Journal ArticleDOI
G.P. Chen1, Om P. Malik1, G.S. Hope1, Y.H. Qin2, G.Y. Xu2 
TL;DR: In this paper, an adaptive power system stabilizer employing a self-optimizing pole shifting control strategy and its application to a power system is described, where the control is computed by an algorithm which shifts the closed-loop poles of the system to some optimal locations inside the unit circle in the z-domain.
Abstract: An adaptive power system stabilizer (APSS) employing a new self-optimizing pole shifting control strategy and its application to a power system are described in this paper. Based on an identified model of the system, the control is computed by an algorithm which shifts the closed-loop poles of the system to some optimal locations inside the unit circle in the z-domain to minimize a given performance criterion. With the self-optimization property, outside intervention in the controller design procedure is minimized, thus simplifying the tuning procedure during commissioning. Also, a new method of calculating the variable forgetting factor in real-time parameter identification is discussed. Studies show that the proposed APSS can provide good damping of the power system over a wide operating range and significantly improve the dynamic performance of the system. >

Book ChapterDOI
TL;DR: In this paper, the AC-model is used to estimate real and reactive power spot prices in the presence of voltage constraints, and the full AC-Model is required to determine both real-and reactive-power spot prices.
Abstract: Differences in locational spot prices in an electric network provide the natural measure of the price for transmission. The ubiquitous problem of loop flow requires different economic intuition for interpreting the implications of spot pricing. The DC-Load model is the usual approximation for estimating spot prices, although it ignores reactive power effects. This approximation is best when thermal constraints create congestion in the network. In the presence of voltage constraints, the DC-Load model is insufficient, and the full AC-Model is required to determine both real and reactive power spot prices.

01 Jan 1993
TL;DR: In this paper, a more detailed analy- sis of system operation is required, which has to consider wind speed forecast uncertainties, system load forecast uncertainties and ramp rate of thermal units and spinning reserves etc.
Abstract: With a large-scale introduction of wind power the power system operation planning including keeping of spinning reserves will be influenced since extra uncertain- ties are introduced. To study this a more detailed analy- sis of system operation is required. This analysis has to consider wind speed forecast uncertainties, system load forecast uncertainties, ramp rater of thermal units and spinning reserves etc. This paper shows a new methodol- ogy to analyce the operation planning with an emphasis on keeping of reserves. The result from the calculations include instantaneous, fast and slow reserve marginr at each hour of the planning period.