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Comments on an article appearing in the January 2000 issue of 'IEEE Transactions on Power Delivery,' which dealt with the features of power distribution quality events. Methods for extracting power quality events from recorded voltage and current waveforms; Transformer energization events.

The voltage collapse phenomenon is one of the serious concerns for power system stable operation. Power system blackout can take place in a part or entire system due to severe voltage instability and inadequate power transfer capability. Therefore, power system operation continuous monitoring and enhancement of the power transmission capability are major concerns for power system planning, design and operation. This study proposes an improved voltage stability index by drawing analogy from existing indices, which are based on active and reactive power changes in a power system. The objective of the employed computational technique is to measure the critical boundaries, therefore, the proposed index is called Critical Boundary Index CBI. The Lagrange Constant computational method is employed to derive the improved index. Then a comparative analysis of the similar indices are presented to show the advantage of the proposed index. Lastly, proposed and conventional indices are evaluated using IEEE 5, 14, and 57 bus test systems. The results indicate some advantages of the proposed index compared to the conventional indices in the same way. Such as applicability of the proposed index for various types of power system topologies with high accuracy. [ABSTRACT FROM AUTHOR]

Abstract: Recently, renewable energy technologies such as wind turbine generators and photovoltaic systems have been introduced as distributed generation. The connection of large number of distributed generators causes voltage deviation beyond the statutory range in a distribution system. In this paper, a methodology for voltage control in proposed by using the tap changing transformers and the inverters interfaced with the distributed generators. In the proposed method, information of the voltage and power is collected via a communication network. Based on these information, the optimal reference values are calculated at the control center, and sent to the transformers and the inverters. The proposed method accomplishes a coordinated operation among the control equipments and reduces the voltage deviation. Effectiveness of the proposed method is verified by the numerical simulation results. [Copyright &y& Elsevier]

Abstract: In recent years, distributed generations based on natural energy or co-generation systems are increasing due to global warming and reduction of fossil fuels. Many of the distributed generations are set up in the vicinity of customers, with the advantage that this decreases transmission losses and transmission capacity. However, output power generated from renewable energy such as wind power and photovoltaics, is influenced by weather conditions. Therefore if the distributed generation increases with conventional control schemes, the voltage variation in a distribution system becomes a serious problem. In this paper, an optimal control method of distribution voltage with coordination of distributed installations, such as On Load Tap Changer (OLTC), Step Voltage Regulator (SVR), Shunt Capacitor (SC), Shunt Reactor (ShR), and Static Var Compensator (SVC), is proposed. In this research, the communication infrastructure is assumed to be widespread in the distribution network. The proposed technique combines genetic algorithm (GA) and Tabu search (TS) to determine the control operation. In order to confirm the validity of the proposed method, simulation results are presented for a distribution network model with distributed (photovoltaic) generation. [Copyright &y& Elsevier]

The authors have proposed Flexible, Reliable and Intelligent ENergy Delivery System (FRIENDS) as a future power distribution system. In the FRIENDS, new facilities called quality control centers (QCCs), which consist of power electronics devices, distributed generators (DGs), energy storage systems (ESSs), etc., are installed between distribution substations and customers. By controlling and operating those devices in QCCs adequately, various functions can be realized. Particularly, when a power supply from the transmission network is interrupted, isolated local networks which consist of some QCCs are composed in order to realize uninterruptible power supply. In the isolated local network, the DG and ESS in QCCs are employed as backup generators. This paper proposes a novel distributed and autonomous method for balancing the supply and demand during isolated operation. This paper also investigates the effectiveness of the proposed method through some computational simulations using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

Electric utility deregulation enabled PPSs (Power Producers and Suppliers) to enter the electricity market. PPSs are supposed to achieve 30-minute balancing control for stable power supply of electric power. In addition, load rejection and instantaneous voltage drops greatly affect turbine shafting, that is, torsional torque oscillation. Therefore, PPSs must consider a reduction of torsional torque in order to prevent generator shaft damage. This paper proposes a control system which allows the achievement of both 30-minute balancing control and reduction of torsional torque by using an H∞ controller. The effectiveness of the proposed controller is validated by using MATLAB. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 16–25, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20868 [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the control method under the 30-min balancing rule for grid-connected PV power. It is possible to adjust the noticed power for PV supply before two hours. The noticed power, that is the adjusted PV supply, and the measured power are controlled under the 30-min balancing rule using a battery, and the 30-min control section is divided. [Copyright &y& Elsevier]

A novel multi-agent-based system based on the contract net protocol (CNP), intended to achieve a distributed approach to power distribution network restoration, is proposed. In the proposed system, agents are assigned to areas sectioned by switches and constantly exchange environmental information among themselves. The information is used to construct a CNP overlay network to guard against network accidents. The parameters of the CNP required for robustness and effectiveness are optimized by the genetic algorithm (GA) in the operation phase. When a network accident occurs, the agents restore power distribution service autonomously through the CNP overlay network constructed. Simulation experiments indicate that CNP allows an effective power distribution network restoration strategy to be created by cooperation among agents. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 56–63, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20661 [ABSTRACT FROM AUTHOR]

This paper presents a new approach to the fuzzy unit commitment problem using the absolutely stochastic simulated annealing method. In every iteration, a solution is taken with a certain probability. Typically in the simulated annealing minimization method, a higher cost feasible solution is accepted with temperature-dependent probability, but other solutions are accepted deterministically. However, in this paper, all the solutions, both higher and lower cost, are associated with acceptance probabilities, e.g., the minimum membership degree of all the fuzzy variables. Be- sides, the number of bits flipping is decided by the linguistic fuzzy control. Excess units with system-dependent distribution handle constraints efficiently and reduce overlooking the optimal solution. To reduce the economic load dispatch calculations, a sign bit vector is introduced with imprecise calculation of the fuzzy model as well. The proposed method is tested using the reported problem data sets. Simulation results are compared to previous reported results. Numerical results show an improvement in solution cost and time compared to the results obtained from powerful algorithms. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in utilizing dispersed generation systems, which are grouped into micro turbine systems, co-generation systems, and so on, as a substitute for fuel oil energy and a technology to prevent global warming. Since start-up time of dispersed generation systems is short, it is possible to operate systems to supply load power corresponding to a demand. Moreover, PPSs (Power Producers and Suppliers) can participate in a power retail sales company, since deregulation of electric utilities was instituted in March 2000. However, PPSs have to keep instantaneous generating power commissioning rule, to maintain supply-and-demand balance between customer and supplier. Therefore, in this paper, we examine instantaneous generating power commissioning for dispersed generators where start-up time is short and it is possible to operate systems to supply a power load corresponding to a demand. We adopt a PI controller as a controller. The system is composed of double control loop in inner loop and in outer loop. In inner loop electric power is controlled and in outer loop electric energy is controlled. The controller parameters are designed using the pole-placement technique. The effectiveness of the proposed control system is confirmed by simulations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(2): 58–66, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10200 [ABSTRACT FROM AUTHOR]

This article discusses various issues related to the article "A Fast Technique for Unit Commitment Problem by Extended Priority List," T. Senjyu, K. Shimabukuro, K. Uezato, and T. Funabashj, that was previously published in the May 2003 issue of the periodical "IEEE Transactions on Power Systems." Since the extended Priority List (EPL) creates the priority list using a simple index, it may not provide the sufficient information for determining the optimal or a near-optimal priority commitment order. However, EPL can compensate the drawback by applying some suitable heuristics, which consider the cost characteristics of unit and prevent load base unit from operating at peak load. It is possible to apply EPL to multi-area unit commitment.