In order to cope with the global warming, importance of energy conservation technologies becomes large and large. This paper shows outline of the recent technology trends and future R&D strategies of national projects in Japan. The basic concept and some important R&D topics of the technology strategies, which will be determined by this September are summarized. They are Super combustion system technologies, Energy utilization technologies beyond time and distance restrictions, Future life environment technologies on energy conservation, Advanced traffic technologies, and New generation device technologies for energy conservation. Some relative R&D themes in industrial sector, civil sector, and transportation sector are also shown.
In order to investigate the impacts of the integration of wind farms into utilities networks, transient stability should be analyzed before connecting wind turbine generator system (WTGS) to the power system. In this paper, a new logical pitch controller equipped with fuzzy logic controller (FLC) has been proposed, which can enhance the transient performance of WTGS during severe network disturbances. Moreover, it can maintain the output power at rated level when wind speed is over the rated speed. Before transient stability analysis, it is necessary to determine initial values of WTGS connected to the external network. In this paper, the initial value calculation method of WTGS is discussed at different wind conditions. Finally, in order to evaluate the effectiveness of the proposed controller in improving the transient stability, simulations have been carried out for severe network disturbances and windy conditions, considering mechanical dead zone of the pitch actuation system. Simulation results clearly indicate that the proposed controller can enhance the transient stability of wind generator at any network, fault or windy condition, and maintain output power of wind generator at rated level when wind speed is over the rated speed.
Recently, numbers of distributed generators (DGs) connected to distribution systems have been increasing. The system operators should know how large capacity of DGs can be connected without problems to one feeder or one bank of the system to control the system appropriately. Conventionally, there are many studies on the protection for short circuit faults. However, there is few studies on the maximum capacity of DGs in the restriction condition of short circuit current (=12.5[kA], S.C.C). The authors deal with sets of DGs that are dispersed on distribution lines widely and limited in the restriction condition of SCC. The maximum capacity of DGs is calculated by quantitative current analysis regarding several parameters such as line length, short circuit impedance of transmittion line and reactance of DGs, etc. The following can be shown from the numerical calculation result. The larger short circuit impedance of transmission system or the reactance of DGs becomes, the larger the maximum capacity of DGs becomes. The maximum capacity of DGs increases if the length of system is longer, or the distribution of DGs capacity is increasing linearly to the end of feeder. The maximum capacity of DGs increases if feeder number is more.
A new CO2-capturing power generation system is proposed that can be easily realized by applying conventional technologies. In the proposed system, the temperature of middle-pressure steam in a thermal power plant is raised by utilizing oxygen-combusting regenerative steam-superheater. The generated CO2 by combusting fuel in the superheater can be easily separated and captured from the exhaust gas at condenser outlet, and is liquefied. The superheated steam is used to drive a steam turbine power generation system. By adopting a high efficient combined cycle power generation system as an example, it has been shown that the proposed system can increase power output by 10.8%, decrease the CO2 emission amount of the total integrated system by 18.6% with power generation efficiency drop of 2.36% compared with the original power plant without CO2-capture, when superheated steam temperature is 750°C
We already proposed “monthly temperature coefficient”(1)(2) as the coefficient that indicates the losses caused by the temperature rise, etc., of the photovoltaic generation system (PV system). This coefficient contains non-linear based losses under the low irradiance of the PV system adding to the loss due to the temperature rise of the photovoltaic module. In this paper, we compare “monthly temperature coefficient” and “cell temperature factor”, and discuss the followings: ·The difference in the fundamental view of two coefficients, and two coefficients of the installed 40kW class photovoltaic generation system ·Calculation results and analysis of the photovoltaic module output and temperature coefficient under the typical irradiance and cell temperature of the photovoltaic module ·Simulation calculation results and analysis of two coefficients in the case that the characteristics of the photovoltaic module, location, and support structure of the photovoltaic module are different Next, the embodiment of practical use method of “monthly temperature coefficient” is described as follows: (1) The calculation method of annual power generation using the table of “monthly temperature coefficient” (2)The separation method of losses of the installed photovoltaic generation system using “monthly temperature coefficient”
This work presents a method for investigating the voltage stability of multi-infeed HVDC systems, which is based on the eigenvalue decomposition technique known as modal analysis. In this method, the eigenvalue of linearized steady-state system power-voltage equations are computed to evaluate the long-term voltage stability. The contributions of this work to modal analysis method are control systems of HVDC system, such as an Automatic Power Regulator (APR) and an Automatic (DC) Current Regulator (ACR) on its rectifier side and a changeover between an Automatic (DC) Voltage Regulator (AVR) and an Automatic extinction advance angle Regulator (AγR) modes on its inverter side, were taken into account, and the formularization for modal analysis considering not only these control systems of HVDC system but also generator and load characteristics was fulfilled and presented in this paper. The application results from an AC/DC model power system with dual HVDC systems verified the efficiency of the proposed method and quantitatively illustrated the influence of control systems of HVDC system on AC/DC system long-term voltage stability.
The authors have developed a new central VQC (Voltage Q(reactive power) Control) method that cooperates with local voltage control devices AVQC (Automatic V-Q Controller). Each AVQC, located at principal substations or power stations, brings bus voltage close to its target voltage independently by controlling the on-load tap changers and shunt capacitors and reactors status. Each target bus voltage is optimally determined through on-line optimal power flow calculation to minimize active power transmission losses in the bulk power grid. Using this central VQC method, efficient voltage control is realized in comparison with the conventional VQC since the target voltage is updated continuously in accordance with the current power grid state. The voltage control function employing the described method has been already implemented into the energy management system at Tohoku EPCO and has been in operation from 2004. This paper presents the newly developed method for central VQC and its excellent performance through bus voltages behaviors at the real Tohoku EPCO power grid.
This paper proposes a new framework of distribution system planning under the condition of mass installed Distributed Generators (DGs). At present, distribution system planners do not pay much attention to the interconnection of DGs. However, if some DGs can supply power instead of conventional power stations, they will give a significant impact. The planners will have a new option to build a network system plan without unnecessary investment to distribution networks. In this study, an objective function for distribution system planning is formulated to obtain maximum profits for utilities, and the authors discuss reduction of the utilities' investment cost and distribution system loss for installation of DGs. In addition, the authors propose a solution method using a genetic algorithm technique in order to find quasi-optimal solutions for large scale problems. Furthermore, the authors also discuss the connection tariff in order to increase the utilization rate of distribution networks. The advantage of the proposed method is demonstrated through several numerical simulations with successful results.
We have developed the Relaxation Pipe (RP) for the prevention of electrostatic charging hazard on a transportation pipe system in petroleum industry. This paper describes that many factors of RP have been discussed, and we have obtained a 100% relaxation factor of discharging rate of static charge. The velocity distribution of flowing petroleum in RP must be known accurately to make a more effective RP, because many hydrodynamic factors are involved obscurely decreasing the relaxation factors. Our experimental results discovered their hydrodynamic factors. We have measured a velocity distribution of kerosene in the RP using a laser Doppler velocimeter (LDV), and we have a computer simulation of the velocity distribution of flowing kerosene with the Navier-Stokes equation. These could be extremely useful for designing more effective RP.
This paper describes a newly-derived theoretical equation on the skin effect factor of power cables, and its application to large-size OF and XLPE cables with segmental conductors, including insulated wires. The skin effect factors calculated with the new equation were fit very well to measurements in wide range conductor sizes. In the new equation, the important factor which characterizes the skin effect of segmental conductors is the `equivalent conductivity ratio' ν defined by the ratio of longitudinal conductivity in axial direction of conductor to conductivity of conductor wires. Since the obtained ratio ν in XLPE cable was three times greater than that in OF cable, the larger longitudinal eddy current passing from a wire to another increased the eddy current loss in conductor, which increased the conductor loss of XLPE cable. The new equation enables us to investigate quantitatively the dominant loss component affecting the skin effect factor. Then, the skin effect factors and coefficients for OF and XLPE cables were investigated with the new equation. It was revealed that the best number of separation, in which the skin effect became minimum, existed in OF and XLPE cables with segmental conductors. In addition, it was confirmed that the skin effect coefficients ks1 calculated with the new equation were consistent well with those used in JCS.
With high hydrogen utilization operation, a minor imbalance in the distributed flow of the stack causes a shortage of hydrogen gas. In order to achieve high hydrogen utilization operation, we investigated the flow pattern for cells internally humidified at the cathode side. We fabricated both counter flow and co flow type cells for humidification of the cells inside the cathode and carried out electricity generation tests on single cells and cell stacks. Also we measured the distribution of relative humidity at the anode electrode for counter flow and co flow humidification of the cell inside the cathode. From these test results we concluded that the counter flow method is superior as a humidification cell inside a cathode when using the stack division method.
A three-in-One HTS cable has been developed. Its cable core is composed of a conductor and a shield wound with BSCCO wires and electrical insulation of the PPLP. The three cable cores are covered in thermal insulated stainless corrugated pipes. Recently, BSCCO wires were drastically innovated by virtue of a newly developed process named as Controlled Over-Pressure (CT-OP). As a new cable technology, a 350m thermal insulation pipe was tested for 7 months to find that a life of the vacuum property is more than 10 years. The HTS cable with tension members was designed for installation into an underground duct. In addition, a fault current of 23kA, 0.63sec, was applied to a sample cable with no damage on the BSCCO wires and the cable insulation. These technologies will be applied to Albany project in USA.
To realize the effective management of grounding resistances, it is necessary to establish a measuring technique of resultant resistance. Especially on underground system, it is too complex the connection of grounding system to understand the resultant resistance exactly by using of calculation, etc. Therefore, we propose a new measuring technique of resultant resistance. That is the way to apply the voltage on two different circuits with auxiliary grounding electrode, and to measure each current of the route on the circuits. Additionally, we produced a test measuring equipment, and performed the verification on electric circuits, practice lines and commercial lines.
A power generating efficiency of solid oxide fuel cell (SOFC) and gas turbine combined cycle is fairly high. However, the exhaust gas temperature of the combined cycle is still high, about 300°C. So it should be recovered for energy saving, for example, by absorption chiller. The energy demand for refrigeration cooling is recently increasing year by year in Japan. Then, we propose here a cogeneration system by series connection of SOFC, gas turbine and LiBr absorption chiller to convert the exhaust heat to the cooling heat. As a result of cycle analysis of the combined system with 500kW class SOFC, the bottoming single-effect absorption chiller can produce the refrigerating capacity of about 120kW, and the double-effect absorption chiller can produce a little higher refrigerating capacity of about 130kW without any additional fuel. But the double-effect absorption chiller became more expensive and complex than the single-effect chiller.