Considering deregulation in power systems and the energy conservation law, power and energy systems require more cost and energy reduction for system planning, operation, and control. Optimization techniques such as linear and nonlinear programming techniques have been utilized as one of the methods for realization of the reduction. Recently, meta-heuristics such as genetic algorithm, simulated annealing, tabu search, and particle swarm optimization have been paid attention as other options for realization of the reduction. In power and energy society, we had one technical committee and one special issue on applications of meta-heuristics for power system. Moreover, panel sessions and tutorials have been held in IEEE and IFAC. This paper presents applications of meta-heuristics to power and energy fields from the practical application point of view.

View full abstract

As the deregulation in the electric industry progress, the electric power market is becoming more competitive. In this study, the simulation of the electric power market using the multi agent system was performed. Modeling and the simulation of pool market was performed first, additionally in the case of monopoly. The effect of the bilateral contract on the power market is also considered. The influence of difference of power market on bid behavior is studied.

View full abstract

This paper compares particle swarm optimization (PSO) techniques for a reactive power allocation planning problem in power systems. The problem can be formulated as a mixed-integer nonlinear optimization problem (MINLP). The PSO based methods determines a reactive power allocation strategy with continuous and discrete state variables such as automatic voltage regulator (AVR) operating values of electric power generators, tap positions of on-load tap changer (OLTC) of transformers, and the number of reactive power compensation equipment. Namely, this paper investigates applicability of PSO techniques to one of the practical MINLPs in power systems. Four variations of PSO: PSO with inertia weight approach (IWA), PSO with constriction factor approach (CFA), hybrid particle swarm optimization (HPSO) with IWA, and HPSO with CFA are compared. The four methods are applied to the standard IEEE14 bus system and a practical 112 bus system.

View full abstract

This paper describes the enhancement of power system stability by using a 2-axis generator with vector type (2-axis) excitation system. The 2-axis excitation generator (machine) is different from the conventional one-axis excitation generator, as it consists of two mutually orthogonal field windings. To make best use of the features offered by this type of generator, two types of control systems, namely Fully Vector Control (FVC) and Partial Vector Control (PVC) schemes are developed and tested for their performance. Each control scheme can independently control the excitation of the 2-axis excitation generator and thereby allows each system to have an additional option of controlling the real power apart from the reactive power. The effectiveness of these control schemes on the 2-axis machine is assessed in terms of operation stability enhancement of the 2-axis excitation generator in comparison to the conventional generator through digital simulations.

View full abstract

Polymer Electrolyte Fuel Cell(PEFC) is expected to become a promising technology for residential energy savings. Becuase daily consumption patterns of hot water demand are quite different, it is very important to evaluate the energy saving effect of PEFC considering the daily difference of hot water demand. Under an assumption which residents forecast a rough information on hot water demand at the next day, this paper proposed a daily start and stop algorithm for residential PEFC system using the forcasted information. Based on an observed data of hot water demand, the algorithm is evaluated from energy saving point of view. The simulation results indicate that (1) 3% improvment of energy savings when the information are set correctly, (2) 1.5% improvment of energy savings even if there are wrong information settings by residents and (3) 80% attainment compared to an ideal potential of energy savings.

View full abstract

The renewable energy resources depend on the natural condition and are difficult to be considered as a stable power source. Moreover, the renewable energy plants tend to be distributed on the demand side and they are difficult to be governed at the central control station. So, the improvements of stabilizing and compensating distributed power system are required to realize the stable power operation.
  This paper describes the effort of application of the Rotary Phase Shifter, which is an phase shifting equipment based on the induction machine technique, as an compensator for the power fluctuation of renewable energy resources, such as wind power stations. It is verified through computer simulation and factory examination using 50kVA-prototype machine connected to the power system simulator with MG set controlled as a wind turbine generator.

View full abstract

Recently, a number of electric consumers have concerned about the reliability of electricity to be served. For example, some consumers need the electricity with a higher reliability by the automation of manufacturing processes. On the other hand, some consumers need the electricity of a cheaper price even if the reliability becomes a little worse. Under such circumstances, it is necessary that power suppliers evaluate the needs of every consumers precisely and propose the most desirable measures for meeting their requirements. This paper develops a tool to analyze the reliability for high-voltage supplied consumers quantitatively. Further, this paper presents a method for evaluating the outage cost of consumers to help them choose the most appropriate measures for maintaining the reliability. The proposed method applies the fuzzy reasoning approach. The validity of the proposed method is ascertained through some numerical simulations.

View full abstract

This paper presents details on the development of a fully digital real-time power system simulator “Hypersim" on a new hardware architecture called PC cluster. PC cluster is a parallel-processing system composed by commodity hardware. Therefore hardware cost of the developed simulator can be reduced compared with simulators implemented on supercomputers. The authors prototyped a real-time simulator “Hypersim" on a 4 CPU cluster. For a small and large size of benchmark power system network, 4 CPU cluster can simulate the network in real-time with 21 and 78 microseconds time step, respectively. This simulator makes us enable to test several equipments in real-time.

View full abstract

This paper describes a new program which analyzes reliability of composite power systems taking power system operational aspects into consideration. It uses sequential Monte Carlo method and calculates annual risk indices for each load point. The program deals with the system problems involved in load flow, voltage, frequency and small signal stability if necessary. The feature of the program is consideration of power system operation in chorological manner such as generation dispatch and system restoration after equipment faults. This allows the evaluation of both power system planning and operation from reliability point of view. Several new methods to reduce calculation time are developed and implemented including the concurrent LP/load flow method which improves the solvability.

View full abstract

In this paper, a decentralized robust approach is proposed for the Automatic Generation Control (AGC) system based on a modified traditional AGC structure. This work addresses the new strategy to adapt well-tested classical AGC scheme to the changing environment of power system operation under deregulation. The effect of bilateral contracts is considered as a set of new input signals in each control area dynamical model.
  In practice, AGC systems use simple proportional-integral (PI) controllers. However, since the PI controller parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance for a wide range of operating conditions and various scenarios in deregulated environment. In this paper with regard to this problem, the AGC synthesis is formulated as an H_∞ static output control problem and is solved using a developed iterative linear matrix inequalities (ILMI) algorithm to design of robust PI controllers in the restructured power system control areas. A three area power system example with possible contract scenarios and wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance.

View full abstract

Authors are developing a system that measures the differential optical intensity from two flint glass fiber type current transducers (OCT) directly connected in a series by an optical fiber and performs differential current measurement. In this paper, we propose adding a summed current information to the subtracted current information as input information of a relay unit. We designed an experimental model including the relay unit applicable to the under ground power line of 20km, 66kV. Evaluation by numerical analysis and examination was performed. In the large current test this model did not misjudge. The total error of OCT is about ±3%, because its own error ratio is ±1.5% combined with its temperature dependence of ±1.5%. However we confirmed that the error is not a problem in operation of this system. We found that the influence of vibration, shock and bending of the optical fiber for transmission can be reduced by using a depolarizer. It has been checked that the proposed system can satisfactorily operate under the conditions we assumed on practical use.

View full abstract

The authors have studied diagnostic technique of gas insulated switchgear (GIS) using partial discharge (PD) induced electromagnetic wave measured by UHF sensors. So far, we have proposed to discriminate discharge type by introducing amplitude ratio Rp: the positive peak value Vp+ to the negative one Vp- of the first wave of incoming electromagnetic wave measured with UHF sensors. In this paper, we discuss electromagnetic wave radiated from simulated pulse and PD measured with disk-type UHF sensors and built-in sensors consisting of a metal ring embedded in epoxy spacer of GIS. The shape of electromagnetic wave measured by the built-in sensor was distorted and high frequency components attenuated through a spacer in comparison with signal measured with the UHF sensor. It was suggested that the spacer may play the role of a low pass filter. Moreover, we proposed to discriminate discharge type based on the first wave of electromagnetic wave measured with the built-in sensors. We also investigated frequency spectrum of propagating UHF signals in GIS with different tank size by finite difference time domain (FD-TD) method with focusing on the influence of higher-order modes.

View full abstract

The Authors have developed a method for the analysis of the induced current density in the three-dimensional shape model by a two-step process consisting of: (1) the derivation of the induced current flowing in from the surface of the human model by the surface charge method; and (2) the application of these values as the boundary values of the finite-element method using an isoparametric hexahedral element.

View full abstract

Operation characteristics of the closed loop experimental facility for CCMHD power generation which is now under construction at Tokyo Institute of Technology are examined by carrying out time dependent quasi-one-dimensional numerical simulations. It was found that under electrical power generation, the compression ratio increases from 4.9 (under non-power generation) to 5.9 (under power generation) because of the large decrease in total pressure by Lorentz force. Then, the increment of the electrical power input to the high temperature gas heater was found to be small (15kW) to compensate for the extraction of the output power (41kW). This is mainly because the argon gas temperature decreases at the generator exit by electrical power generation, as a result, the amount of cooling in the diffuser and cooling duct reduces. The start-up operation of the closed loop experimental facility is proposed. The rated operating condition can be obtained by increasing discharge flow rate of the compressor through several stages of operations, i.e., argon gas charging and adjustment of heater input power. By following this operation procedure, it is possible to operate this facility without violating any restrictions of the facility.

View full abstract

This paper proposes the wind collector for the wind power generation. By this wind collector, the wind which passed the wind generator system is accelerated. As the result, it is possible that the wind generator system gets the rated wind velocity in low wind. The effectiveness of proposed wind collector is examined using the computer simulation and the wind power generator with the wind collector.

View full abstract