Three-dimensional numerical analysis of a liquid metal MHD generator has been carried out. The three-dimensional structures of the electromagnetic field and fluid flow in the MHD generator have been clarified, and the effect of the electrode width on the performance has been also examined, taking account of the current flow in the electrode. Structures of the electromagnetic field and fluid flow are complicated owing to the three-dimensional current flow, induced magnetic field, and Lorentz force. The highest performance is found to be obtained when the width of electrode is equal to that of the generator. The performance predicted from three-dimensional analysis is somewhat lower than that from two-dimensional analysis because of the larger input power. The increase in the input power is attributed to the increase in Lorentz force caused by less reduced magnetic flux density and to the additional friction loss on the insulator walls (x-y plane).
Advances in distributed generation technologies together with the deregulation of an electric power industry can lead to a massive introduction of distributed generation. Since most of distributed generation will be interconnected to a power system, coordination and competition between distributed generators and large-scale power sources would be a vital issue in realizing a more desirable energy system in the future. This paper analyzes competitions between electric utilities and cogenerators from the viewpoints of economic and energy efficiency based on the simulation results on an energy system including a cogeneration system. First, we examine best response correspondence of an electric utility and a cogenerator with a noncooperative game approach: we obtain a Nash equilibrium point. Secondly, we examine the optimum strategy that attains the highest social surplus and the highest energy efficiency through global optimization.
This paper deals with a robust H2 output feedback controller design for damping power system oscillations. Sufficient conditions for the existence of output feedback controllers are given in terms of linear matrix inequalities (LMIs). Furthermore, a convex optimization problem with LMI constraints is formulated to design the output feedback controller which minimizes an upper bound on the worst-case H2 norm for a range of admissible plant perturbations. The technique is illustrated with applications to the design of stabilizer for a single-machine infinite-bus (SMIB) and a multimachine power system. The simulation results illustrate the effectiveness and robustness of the proposed stabilizer over a wide range of loading conditions.
It is needed to study the transient performance of grounding systems for lightning surges to ensure the electromagnetic compatibility (EMC) of sensitive electronics such as information devices and digital relays in substations and/or residential houses. Therefore, an easy method of estimating frequency response to represent the transient performance of grounding systems and its incorporation into Electromagnetic Transient Program (EMTP) are highly desired. EMTP based on circuit theory has been applied to resolve the transient performance of electrical apparatus consisting of cables and conductors which are parallel to the ground surface, in which the propagation of TEM waves that are plane waves is implicated, and devices such as surge arresters represented by lumped elements. However, conductors which are vertical to the ground surface have not been modeled because TM waves propagate on such conductors and the characteristics in early time, when the approximation of plane waves is not adapted, are required. In this paper, for the vertical and rotatory symmetric grounding electrodes, we propose a computational method for the impedance, which is defined as the complex ratio of the potential of its top at the ground surface to the current flowing into it in the frequency domain. The potential is derived from the integral of the horizontal component of electric fields along the path reaching the electrode on the ground surface because the potential could be uniquely defined in the case of a horizontal plane by considering the electromagnetic field in the configuration discussed here. We then calculated the potential of the electrode and current flowing into it in the time domain by computational analysis of transient performance based on the FD-TD method (CATP) and the impedance up to 20MHz in the frequency domain were derived using the Fourier transforms of the potential and current in the time domain.
This paper presents a newly developed EDC (Economic Dispatching Control) function for Tohoku EPCO's new EMS system. In this new EDC, we can minimize total fuel cost under system security constraints such as “AFC margin considering band width and ramp rate in future band changing schedule" and “power flow constraint considering future maintenance schedule". We formulate EDC problem as “continuous variable (generator output) optimization" under “combinatorial optimization of band schedule". To optimize this problem, Problem Space Search method and interior point QP method are adopted. Test results and the actual operation show that, this new EDC can follow against steep increase and decrease of electric demand cooperating with AFC. This EDC has been operating successfully in Tohoku EPCO since June 2003.
We propose a new method for finding the direction of arrival (DOA) of the electromagnetic waves emitted from a partial discharge source using Bayesian Network. The time delay between two antennas computed from digital data generally has error because of the effect of sampling time. Therefore the angle of arrival estimated from the time delay also has the estimation error. In order to deal with the estimation error, we investigate a probabilistic method of reasoning with uncertain information. In this method, system provides the probabilities of each angle based on Bayes' Theorem. From results of a simulation and an experiment, we have confirmed that our proposed method is able to estimate the angle of arrival of the electromagnetic waves.
Ozone is recently used for many purposes as an environmental friendly oxidant, so the ozone production device with high ozone concentration and low production energy is desired. One of the candidates for such device is the ozone water production by water electrolysis cell using the solid polymer electrolyte with PbO2 anode catalyst, which has merits to be compact and to produce high-concentration ozone water directly by the deionized water electrolysis. In this study, we have tested ozone water production by changing electrodes and electrolytes constitution in order to improve the ozone production performance. Tested two electrolytes are Nafion117 and a membrane-electrode assembly (MEA) with Pt catalyst on cathode side of Nafion117. Tested two electrodes are mono-layer of Ti expanded metal and four different mesh layers of Ti expanded metal. Ozone water production tests are performed under long-term operations changing temperature and flow rate to optimize experimental conditions. The voltage-current characteristic for electrolysis cell have been improved significantly, when the electrode is four layers of Ti metal and the electrolyte is the MEA with Pt catalyst. The stable ozone water concentration has been obtained by operating the cell for about 8 hours. The optimum temperature and water flow rate for ozone water production are 25˜30° and 33L/h, respectively. Furthermore, the optimum overpotential was measured by a reference electrode at the cathode-side MEA, and the anode catalyst suitable for ozone water production was identified to be βPbO2 by the X ray diffraction pattern.
Emission regulation is being tightened up recently to prevent expansion of air pollution. Economic and efficient technologies are desired to process NOx generated in combustion of fossil fuel. One of the candidate technologies to process NOx is the denitrification of flue gas by pulsed corona discharge, which has been demonstrated experimentally to have the high deNOx performance. However, the optimization of operation conditions and the appropriate understanding of the deNOx process are still remained not to be cleared. Therefore, we have simulated in this study the deNOx process added by hydrocarbon such as ethylene to give its proper operation conditions and its main reaction paths to remove NOx, following our previous study on ammonia addition. The simulated results show that the removal efficiency in a case of ethylene addition becomes lower than that in ammonia addition, but the deNOx energy consumption rate becomes lower than the ammonia injection case. However, the ethylene injection leads to produce the pollutant of formaldehyde, which limits the allowable amount of injected ethylene. In a case of propylene injection its deNOx performance is better than the ethylene addition case, because propylene reacts with OH radical more than ethylene to oxide NOx. However, formaldehyde is also produced in propylene injection case, limiting the allowable amount of injected propylene.
We have been investigating the residual-charge measurement as a diagnostic method for water-tree deteriorated cross-linked polyethylene cable. In the method that we proposed here, the residual charge component detected by higher AC voltage application could correspond to longer water trees. Therefore, this method is effective to diagnose the degree of water-tree deterioration in the long distance cable line.
In the combined-cycle power plant generators are started by using the igniting arrangement up to the ignition rotational speed of the gas turbine. On the other hand, in case of using the superconducting generator, it is difficult to apply the igniting arrangement used to generate electricity on the combined cycle for the structure as it is. Then, we examined the induction motor starting method of superconducting generator by using the 70MW class quick response excitation superconducting model generator and the VVVF power supply. In the result of examination, we confirmed to be able to raise the rotational speed from 6 to 360rpm. Moreover, it was clarified to be able to start 200MW class superconducting generator by the induction motor start method with the analysis.
The secondary batteries for the electric vehicle (EV) generate much heat during rapid charge and discharge cycles, when the EV starts quickly consuming the battery power and stops suddenly recovering the inertia energy. The generated heat increases significantly the cell temperature and causes possibly bad influences on the battery performance and the safely requirement. So we have studied the thermal behavior of nickel/metal hydride (Ni/MH) battery during rapid charge and discharge cycles, applying our previous battery thermal model, which have been confirmed to agree with the experimental results at smaller charge current than the rated current. The heat sources by the entropy change, the hydrogen occlusion and the side reaction have been referred to the published data, and the overpotential resistance and the current efficiency, the ratio of main reaction current to charge current, have been measured experimentally through the rapid charge and discharge characteristics with constant current. By using these data our thermal model for Ni/MH battery has estimated its temperature increase, which agrees well with the measured temperature rise, with the root mean square error of 1.5°C and 2.1°C for charge and discharge cycles, respectively.
Lightning damages of home electric appliances occurred in 154houses of 6,024monitors, were gathered in summer and winter seasons of 1987-1991 and 1996-1997. Types of damaged home appliances are summarized and extent of the damages are investigated. Furthermore the magnitude of invading lightning currents and the path of the invasion were estimated by means of inspections of the inner circuits of damaged home appliances and the experimental verifications. These investigations can lead to the development of lightning protection methods for home electric appliances of this highly computerized society.
As the generated heat mainly limits the maximum unit capacity of tank-type power capacitor, it is important to use low loss capacitor elements. This paper describes the developed wide-width element with folded and extended foil electrodes largely improves capacitor loss, and could make possible for cooling design to perform much larger unit capacitors without cooling apparatus such as radiators. The capacitor loss characteristics of three types of element were examined, which became clear the loss reduction of the developed one caused by less current on the electrode foils and by less electrode edge effect. Next, the temperature rise test results of actual large tank-type capacitors drew the empirical equations, which were considered based on the heat transfer engineering. Calculating the temperature rise of tank and inside oil, the bounds of maximum unit capacity could be estimated on the same design policy as the examined.