Showing papers on "Power-flow study published in 1998"

Power System Analysis

Abstract: This text is intended for undergraduates studying power system analysis and design. It gives an introduction to fundamental concepts and modern topics with applications to real-world problems. This is the first text in this area to fully integrate MATLAB and SIMULINK throughout. It also provides students with an author-developed POWER TOOLBOX DISK organized to perform analyses and explore power system design issues with ease.

Harmonic and reactive power compensation based on the generalized instantaneous reactive power theory for three-phase four-wire systems

Abstract: This paper presents harmonic and reactive power compensation based on a generalized theory of instantaneous reactive power for three-phase power systems. This new theory gives a generalized definition of instantaneous reactive power, which is valid for sinusoidal or nonsinusoidal and balanced or unbalanced three-phase power systems with or without zero-sequence currents and/or voltages. The properties and physical meanings of the newly defined instantaneous reactive power are discussed in detail. A harmonic and reactive power compensator based on the new theory for a three-phase harmonic-distorted power system with zero-sequence components in the load current and/or source voltage is then used as an example to show harmonic and reactive power measurement and compensation using the new theory. Simulation and experimental results are presented.

Power flow control and power flow studies for systems with FACTS devices

Abstract: In this paper, the modeling of flexible AC transmission system (FACTS) devices for power flow studies and the role of that modeling in the study of FACTS devices for power flow control are discussed. FACTS devices are solid-state power converters that have the capability of control of various electrical parameters in transmission circuits. A number of power flow study programs were developed in order to model various types of FACTS devices. Three main generic types of FACTS devices are suggested and the integration of those devices into power flow studies, studies relating to wheeling and interchange power flow control are illustrated.

Method and apparatus for providing uninterruptible power using a power controller and a redundant power controller

Abstract: A power supply system has a power input to receive input power from a power source, a power output to provide output power to a load, at least one battery module having a battery output that provides battery power, at least one power module coupled to the power input to receive the input power, coupled to the battery output to receive the battery power and coupled to the power output to provide the output power, a controller, coupled to the at least one power module, constructed and arranged to monitor and control the output power from the at least one power module, and a redundant controller, coupled to the at least one power module and to the controller, constructed and arranged to provide redundant monitoring and controlling of the output power from the at least one power module.

An analytical approach for transaction costs allocation in transmission system

Abstract: This paper proposes an analytical approach for allocating transmission transaction costs among users in transmission services. The proposed method allocates the transaction costs over the participants proportional to the ratio of incremental power flow caused by each participant and the total power flows on a designated transmission line. To determine the individual participant's impact on the transmission power flows, the line utilization factors (LUFs) of each participant are developed from a set of power flow equations. In the developed framework, one can directly evaluate the sensitivity of the flow on a line with respect to power generation at all buses. Although the developed allocation rule is very similar to the existing MW-mile method, especially to the modulus method, it does not require load flow analysis to be performed whenever each wheeling transaction is exercised. The main advantage of the developed method lies in its capability to consider multiple wheeling transactions simultaneously.

A power macromodeling technique based on power sensitivity

Abstract: In this paper, we propose a novel power macromodeling technique for high level power estimation based on power sensitivity. Power sensitivity defines the change in average power due to changes in the input signal specification. The contribution of this work is that we can use only a few points to construct a complicated power surface in the specification-space. With such a power surface, we can easily obtain the power dissipation under any distribution of primary inputs. The advantages of our technique are two-fold. First, the required parameters corresponding to each representative point can be efficiently obtained by only one symbolic power estimation run or by only one Monte Carlo based statistical power estimation process. This stems from the fact that power sensitivity can be obtained as a by-product of probabilistic or statistical power estimation runs. Second, the memory requirements for the macromodel are reduced to O(dn), where n is the number of primary inputs of a circuit and d is the number of representative points (d can be as small as 1 in some cases). Results on a number of benchmark circuits demonstrate the effectiveness of our technique.

Interface exploration for reduced power in core-based systems

Abstract: Reducing power dissipation is becoming more important in the design of embedded systems. Core-based system design opens up the opportunity for exploring different bus interfaces in order to optimize for reduced power. We give a first approach for exploring a range of possible bus configurations, such as width and coding schemes, for a given set of communication channels. Our approach uses power estimation formulas, for fast performance. We use this approach to explore different bus interfaces for a real GPS navigation system in order to select the optimal bus interface for minimum power consumption.

Genetic algorithm for optimal reactive power dispatch

Abstract: Scheduling of reactive power in an optimum manner reduces circulating VAr promoting flatter voltage profile which lead to appreciable MW saving on account of reduced power system losses. Hence, the optimal reactive power dispatch assumes extremely important functioning both in the planning stage as well as in day to day operation of the power system. This paper presents an alternative approach to optimal reactive power dispatch based on genetic algorithm techniques (GAs). The technique is used to search for transformer tap settings and the value of shunt capacitors of a given power system such that the total system power loss is minimised. The proposed method is tested on IEEE 14 and 30 bus test systems and their results are compared with those obtained using load flow calculation.

Power Analysis of a 32-bit Embedded Microcontroller

Abstract: A new approach for power analysis of microprocessors has recently been proposed [14]. The idea is to look at the power consumption in a microprocessor from the point of view of the actual software executing on the processor. The basic component of this approach is a measurement based, instruction-level power analysis technique. The technique allows for the development of an instruction-level power model for the given processor, which can be used to evaluate software in terms of the power consumption, and for exploring the optimization of software for lower power. This paper describes the application of this technique for a comprehensive instruction-level power analysis of a commercial 32-bit RISC-based embedded microcontroller. The salient results of the analysis and the basic instruction-level power model are described. Interesting observations and insights based on the results are also presented. Such an instruction-level power analysis can provide cues as to what optimizations in the micro-architecture design of the processor would lead to the most effective power savings in actual software applications. Wherever the results indicate such optimizations, they have been discussed. Furthermore, ideas for low power software design, as suggested by the results, are described in this paper as well.

Eigenvalue-based methods for analysis and control of power system oscillations

Abstract: This paper reviews eigenvalue-based methods for analysis and control of power system oscillations. The characterization of power system oscillations using the eigenvalues and eigenvectors of the state matrix is detailed. Design of power system damping controllers is addressed with the aid of sensitivity measures. Special techniques to deal with large power systems are also discussed.

A comparison of load flow analysis using DistFlow, Gauss-Seidel, and optimal load flow algorithms

Abstract: The state of a power system and the methods of calculating this state are extremely important in evaluating the operation of the power system, the control of this system, and the determination of future expansion for the power system. The state of the power system is determined through load flow analysis that calculates the power flowing in the lines of the system. There are several different methods to determine the load flow of a given system. For the purposes of this paper, only three methods of load flow algorithms are evaluated: Gauss-Seidel, optimal load flow, and the DistFlow method.

Reactive power optimization based on genetic algorithm

Abstract: This paper presents an improved genetic algorithm (GA) for optimizing power system reactive power. Based on a basic GA, an integer/float mixed coding GA is proposed in this paper. The objective function of the proposed method is to minimize the system active power loss. The control variables are generator bus voltages, transformer tap positions and switchable shunt capacitor banks. The refined GA overcomes the drawbacks of conventional reactive power optimization methods. The proposed method has been applied to the practical ward-Hale 6 bus system and IEEE 30-bus system. The test results show that this method is a very feasible and practical method.

An analysis of costs related to the loss of power quality

Abstract: This paper aims to analyze disturbance effects related to the loss of power quality on transformers, cables, and induction motors, amongst others. In addition to this, the relationship between power quality and extra costs associated to the increase in power consumption for a typical industry is also taken into account. The study uses a modern computational platform known as the SABER simulator that utilizes the time domain strategy to represent the system components. Qualitative as well as quantitative analysis are carried out to illustrate the phenomenon.

Power and signal distribution for automotive electronics using area and feature modules

Abstract: The invention is directed to an electrical distribution system for an automobile having a power distribution bus and a signal distribution bus. An area module has an electrical connection with the power distribution bus and the signal distribution bus. The area module has connections to individual feature modules. The feature modules have power and signal distribution for electrical components. The area and the feature modules distribute power and signal to the electrical components from the power distribution bus and the signal distribution bus.

Optimal operation and allocation of reactive power resource considering static voltage stability

Abstract: In this paper, new formulation of the reactive power equipment operation and planning problem in the power system has been proposed for providing maximum active power supply margin (transmission margin) as viewed from static voltage stability, while satisfying various system operation constraints. While clarifying the fact that the problem related to reactive power operating and planning problems are rooted in the load flow optimization, a new optimal power flow problem for solving such problems has been introduced. Also, an algorithm based on the successive quadratic programming method has been developed. Furthermore, taking the optimal allocation problem relative to reactive power equipment as an example, its effectiveness in the 5-bus and 11-bus systems has been confirmed.

Apparatus and method for controlling reactive power

Abstract: PROBLEM TO BE SOLVED: To provide a reactive power controller which is capable of reducing capital investment and maintenance cost by omitting the reactive power controllers installed at the premises of consumers or power systems. SOLUTION: A reactive power controller, which controls the reactive power of a power system 1 interconnected with a power unit 20 is provided with a DC-AC converter having a reactive power control function, is provided with a voltage measuring means 50 which detects the system voltage or reactive voltage of the private power system of a consumer or a power system 1 for commercial power supply provided with the DC-AC inverter 23, an appropriate reactive power flow value calculating means 41, which receives the signal of the detecting means 50 and calculates the appropriate value of a reactive power flow, a reactive electric energy commanding means 43 which calculates and instructs an appropriate reactive power command value to the converter 23 upon receiving the calculated results of the calculating means 41, and an operation mode discriminating means 42 which discriminates the operation mode of the converter 23 and controls the reactive power of the converter 23 based on the command from the reactive electrical energy commanding means 43. COPYRIGHT: (C)1999,JPO

Power system equipped with load controller fitted to states of power facilities

Abstract: PROBLEM TO BE SOLVED: To implement the states of power facilities connected to a power line and practice consumption-supply operation plans of the respective power facilities, which satisfy consumption-supply characteristics of the respective power facilities and furthermore, satisfy overall requests such as the load levelling, the single operation in a power supply interrupt state, etc. SOLUTION: A measurement device 104 of a current value 103 and a load controller master station 105 are provided. The master station 105 is connected to a power carrier I/O device 106, and a power carrier signal 107 can be inputted/outputted through a power line. An extension station 114 which is connected to the power line through a power plug 109, and outputs a control signal 113 to an inverter 112, which regulates the watthours of a power carrier I/O device 110 and internal equipment 111, is provided in a power facility 108. The respective extension stations transmit respective power consumption-supply characteristics/operation states, by using power line carrier waves to the master station which generates the operation plans of the respective power facilities suitable for the states, in accordance with the information from the extension stations and the current values and delivers control command to the respective extension station.

Generator set with redundant bus sensing and automatic generator on-line control

Abstract: A generator set controller includes a dead bus sensor producing a dead bus signal indicative of a power failure on a power bus that is an input to the controller on a digital input channel. The controller also receives a voltage signal from a phase of a power bus.

A universal active power filter for single-phase reactive power and harmonic compensation

Abstract: In modern power distribution systems, the majority of loads draw reactive power and/or harmonic currents from the AC source along with main active power currents. These nonunity power factor linear and nonlinear loads cause low efficiency of the power supply system, poor power factor, destruction of other equipment due to excessive stresses and EMI problems. Active filters have been considered an effective solution to reduce these problems. This paper presents an active power filter (APF) based on a simple control technique to provide reactive power and harmonics compensation for linear and nonlinear single-phase loads. A voltage source inverter with carrierless hysteresis PWM current control is used to form the APF. A simple PI DC bus voltage controller with a reduced energy storage capacitor is employed in the APF. A set of lagging/leading power factor linear loads and a diode rectifier-fed capacitive load and AC voltage regulator-fed inductive load as nonlinear loads are used to demonstrate the effectiveness of the proposed APF for reactive power and harmonic compensation. The detailed steady-state and dynamic performances of the APF are presented and discussed in brief.

Corona and field effects experience on an operating utility six-phase transmission line

Abstract: A three-year operating period of a six-phase power transmission line on an operating electric utility has given experimental verification to available methods for calculation of electric and magnetic fields, radio noise and audible noise from six-phase overhead power lines. Successful completion of the operational measurement program has provided further encouragement to the future application of high phase order.

A reconfigurable dual output low power digital PWM power converter

Abstract: Most work to date on power reduction has focused at the component level, not at the system level. In this paper, we propose a framework for describing the power behavior of system-level designs. The model consists of a set of resources, an environmental workload specification, and a power management policy, which serves as the heart of the system model. We map this model to a simulation-based framework to obtain an estimate of the system's power dissipation. Accompanying this, we propose an algorithm to optimize power management policies. The optimization algorithm can be used in a tight loop with the estimation engine to derive new power-management policy algorithms for a given system-level description. We tested our approach by applying it to a real-life low-power portable design, achieving a power estimation accuracy of ∼10%, and a 23% reduction in power after policy optimization.

A generalised three-phase power flow method for the initialisation of EMTP simulations

Abstract: Phase voltage and current unbalance is a basic power quality concern. Three-phase power flow analysis is needed to investigate unbalance problems. In this paper, the unique modelling issues associated with unbalanced power flow calculations are discussed. Four types of load models are proposed. Using the concept of component level power flow constraints, a generalized method for three-phase power flow analysis is developed. Case studies supported by field measurement results are used to verify the proposed method and to demonstrate the deficiencies of traditional methods.

Sensitivity analysis of power system trajectories: recent results

Abstract: The development of trajectory sensitivity analysis for power systems is presented in this paper. A hybrid system model which has a differential-algebraic-discrete structure is proposed. Crucial to the analysis is the development of jump conditions describing the behaviour of sensitivities at discrete events, such as switching and state resetting. A power system example which involves a mix of continuous and discrete behaviour is presented to illustrate various aspects of the theory. It is shown that trajectory sensitivities provide insights into system behaviour which cannot be obtained from traditional simulations.

Computation of power quality symmetrical components using fuzzy logic based linear combiners

Abstract: This paper presents a new approach to estimate the symmetrical and /spl alpha/-/spl beta/ components of the voltage and current signals of a power distribution network using Fourier linear combiners. The learning parameter for updating the weights of the combiner is adapted using a fuzzy logic-based algorithm obtained from the error covariances. The new algorithm is tested using recorded data from an industrial load bus supplying power to electronically controlled induction furnace loads. The estimation results are compared with a 19/sup th/ order Kalman filter approach to highlight the accuracy and fast tracking capabilities of the new approach. The linear combiner, however, presents a simple and implementable algorithm in comparison to the well known Kalman filter approach.

Power Flow Analysis of Electrostrictive Actuators Driven by Switchmode Amplifiers

Abstract: In this paper we analyze the power flow between stacked electrostrictor actuators and a pulse-width-modulated switching amplifier. The amplifier and actuator are analyzed as components of a smart skin whose function is underwater acoustic echo cancellation. An integrated model is developed which includes a dynamic structural model of the actuator, a dynamic model ofthe power electronics and a nonlinear electromechanical coupling mechanism of the electrostrictor actuation material. Using a linearized version of this model, the mechanical admittance of the actuator as seen by an external force is analyzed. It is shown that an outer acoustic control loop can modify this mechanical admittance and optimize the power coupling between the actuator and an external fluid medium by impedance matching. With the nonlinear model, the power flow between the electrical and mechanical systems is analyzed through simulation. The flow of power is traced from the power injected by the external force, through the amplifier and into the electrical bus. It is shown that effective power flow occurs only when the frequency ofthe external force is within the bandwidth ofthe amplifier. This analysis also reveals that the electrical power flow through the actuator is two orders of magnitude larger than the external mechanical power extracted by the actuator. This analysis shows that one main requirement on the amplifier design is to manage the charge flow through the actuator.

Optimal reactive power control for industrial power networks

Abstract: In addition to process steam and real power demands, manufacturing processes also have a varying reactive power demand that must be satisfied. Reactive power affects line currents and bus voltages, as well as power factor of the tie-line bringing power into the industrial plant from the local utility. The local utility applies a penalty if the tie-line power demand exceeds an agreed value and often imposes a low power factor penalty as well. Stable system operation requires that bus voltages are maintained within assigned limits, that transformers and connecting cables do not become overloaded, and that generators and synchronous motors run within their reactive capabilities. There can be many acceptable combinations of the settings of generator and synchronous motor excitations, of transformer taps and capacitor banks, all of which lie within the set of electrical system constraints. There are so many variables to manipulate that is very difficult for an operator to make optimal decisions, even under steady-state conditions. It is an even more complicated task during system upsets. This paper discusses a program that runs on a plant's distributed control system that resolves alternatives and presents to the operator the best combination of settings for implementation. The program can be adopted for direct online implementation. The paper discusses cases of three plants where online implementations have been employed.

Power flow-calculating device for power distribution system control system

Abstract: PROBLEM TO BE SOLVED: To accurately and quickly calculate power flow, by using a neural network for calculating the voltage and reactive power values of each detection position based on the load power between detecting devices, a transmission voltage from a transformer, or the like. SOLUTION: In a neural network 500, adjustment amount of voltage ICRV1 - ICRV3 and adjustment amount of reactive power ICRQ1 -ICRQ3 of each regulator, adjustment amount of reactive power TCRQ1 -TCRQ3 of each reactor, load active power P1 -P8 and load reactive power Q1 -Q8 between detecting devices, and a transmission voltage VS and a transmission phase θS from a substation for power distribution are inputted into input layer units 101-1-101-27 for distributing to M. Then, middle layer units 201-1-201-M perform weighting to 27 data to be inputted, and distribute them to 28 portions for outputting. Furthermore, output layer units 301-1-301-28 add M data, and output voltage values VC1 -VC14 and reactive power values QC1 -QC14 at each detection position.

Power swing damping control by HVDC power modulation in an ac/dc hybrid transmission system

Abstract: This paper describes power swing damping control by HVDC power modulation. In a hybrid system (where the ac transmission system and the HVDC system compose a loop transmission system), damping control of power swing by control of HVDC power is called power modulation control. The new HVDC link between the Shikoku and Kansai power systems forms a loop transmission system consisting of the existing ac transmission system and the new HVDC transmission system; therefore, power modulation control can be applied for stabilization of the ac system. This paper deals with a newly developed power modulation control system to damp two power-swing modes occurring in a 60-Hz interconnected system and the neighboring power system to the HVDC converter station. Characteristics of power swings in an ac system, principles of power swing damping control by power modulation, the control system design method, and the results of verification tests by digital and analog simulators are described. It is shown that the developed power modulation system applied to the HVDC link is effective for damping two power swing modes. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 10–18, 1998