Movement toward extra high voltage and large capacity of overhead transmission line induces problems of wind noise and corona noise to the peripheral areas. Accordingly, environmental concern has become a critical issue of overhead transmission line construction. To reduce environmental impact, low noise overhead conductors have been developed. Meanwhile, as the environmental impact of transmission lines, there is a problem of corrosion due to intrusion of sea salt and acid rain to the inside of the wire. To reduce the environmental impact, corrosion-resistant conductors have been developed. This paper presents various environmental technologies applied to the site and future trends.
In order to maintain system voltage within the optimal range and prevent voltage instability phenomena before they occur, a variety of phase modifying equipment is installed in optimal locations throughout the power system network and a variety of methods of voltage reactive control are employed. The proposed system divided the traditional method to control voltage and reactive power into two sub problems; “voltage control” to adjust the secondary bus voltage of substations, and “reactive power control” to adjust the primary bus voltage. In this system, two types of agents are installed in substations in order to cooperate “voltage control” and “reactive power control”. In order to verify the performance of the proposed method, it has been applied to the model network system. The results confirm that our proposed method is able to control violent fluctuations in load.
The PSS is the reasonable controller to stabilize the inter-tie and local oscillations of power network. The PSSs are usually set with the one-machine infinite-bus system model. The coordinated setting of the multiple PSSs considering the characteristics of the network, is expected to improve the stability. For this purpose, the Modal Performance Measure method is applied for adjusting PSS parameters. The model is identified with the N4SID identification method In this paper, the conditions of identification and validation of identification are shown. Identified model are validated by comparison of vector diagram, impulse responses and so on. Identification of power network that consists of many generators is succeeded.
This paper presents a methodology to perform the capacity planning of a grid-independent power system, which is mainly composed of PV panels, small wind turbines, fuel cell systems and batteries. The methodology aims at finding the optimal capacities of these power sources to meet the required system supply reliability, with the lowest value of levelized cost of energy. As the first step in the capacity planning, the mathematical models for characterizing PV panels, wind turbines and batteries are proposed. The second step is to optimize the capacities of the power sources according to the Loss of Power Supply Probability (LPSP) and the Levelized Cost of Energy (LCE) concepts. The configurations, which meet the required LPSP with the lowest LCE, give the optimal choices. The surveyed meteorological data and energy demand data of an apartment in Kanto area are used in the capacity planning.
A large amount of PV penetration may introduce uncertainties in the future power system planning and operations. This paper proposes the concept of “Robust Security (RS)” and “RS region” in order to investigate power system security in the presence of a large amount of uncertainties. The RS region is defined as the region of power system operation where the system is secure under uncertainties. It is shown that the region tends to shrink and disappear for a large amount of PV penetrations. Emerging problems are investigated concerned with security in future power systems.
The layout optimization with the ON-OFF information of magnetic material in finite elements is one of the most attractive tools in initial conceptual and practical design of electrical machinery for engineers. The heuristic algorithms based on the random search allow the engineers to define the general-purpose objects, however, there are many iterations of finite element analysis, and it is difficult to realize the practical solution without island and void distribution by using direct search method, for example, simulated annealing (SA), genetic algorithm (GA), and so on. This paper presents the layout optimization method based on GA. Proposed method can arrive at the practical solution by means of multi-step utilization of GA, and the convergence speed is considerably improved by using the combination with the reduction process of design space.
For the electric power equipment and the cables, prevention of accident is very important. And in substations, a lot of solid insulations using epoxy resin are introduced into cubicle-type switchgears because of its high insulation reliability and down-sizing ability. We know a phenomenon that partial discharge occur when electric installation have degraded. When void or crack exist in the polymer insulating materials or interface of conductor, partial discharge is caused and finally results in breakdown. In recent years, the feature is seen in the partial discharge generated in the epoxy resin before and after the progress of electric tree by our research. Electro-magnetic wave spectra radiated from partial discharge have specific frequency region from 200MHz to 450MHz. We developed the sensing device that can detect the electric discharge by receiving the signal by mobile antenna. We proved the performance of this equipment in operating substations; As a result, partial discharge in epoxy resin was detected by electro-magnetic wave. And then, we removed epoxy resin bushing from the cubicle and measured partial discharge by discharging current, we confirmed that presumed level is correct.
In underground distribution systems, a CVT (Cross-Linked Polyethylene Insulated PVC Sheathed Triplex) cable is installed in a protective pipe. When a fault arc occurs on the CVT cable, instantly the pressure increases due to the high temperature of the arc and it propagates in the pipe. The pressure-rise and propagation may seriously damage to the pipe and connected power equipment. There are many different sizes of pipes and cables depending on the installation situations, and fault arc occurs under various conditions. Therefore, the simulation technique is effective for examining such pressure-rise and propagation in addition to short-circuit tests. The objective of this paper is to present a CFD (Computational Fluid Dynamics) modeling that can be used to evaluate the characteristics of the pressure-rise and propagation by the fault arc in the protective pipe. As a result, the pressure-rise waveforms by the CFD analysis were similar to those short-circuit test results. In addition, the dependences of maximum pressure-rise on the sizes of the CVT cable and arc current were simulated well. Therefore, the CFD modeling is sufficient for the study of the pressure-rise and propagation in the protective pipe.
In the last decade, a Dielectric Barrier Discharge (DBD) plasma actuator driven by combination voltage of AC and nanosecond pulse has been studied. The combined-voltage-driven plasma actuator increased the body force effect, which induces wall jet and flow suction, by overlapping nanosecond pulse voltage while DBD plasma actuator driven by nanosecond pulses is a flow control actuator generating compression waves due to pulse heating, which allows us to do active flow control in high speed flow reported up to Mach number 0.7. In this study, DBD plasma actuator driven by combination voltage of sinusoidal AC and nanosecond pulse has been experimentally studied. Time-averaged net thrust and cycle-averaged power consumption of actuator were characterized by electrical weight balance and charge-voltage cycle of DBD plasma actuator, respectively. The plasma actuator thrust driven with the combination voltage enhanced its thrust with pulse repetition rate increase. Energy consumption in the actuator was controlled by varying AC phase when the nanosecond pulse is applied. Therefore, the thrust and power consumption in the actuator was almost independently controlled by pulse repetition rate and pulse imposed phase.
An optimal control for maximizing extraction of power in variable-speed wind energy conversion system is presented. Intelligent gradient detection by fuzzy inference system (FIS) in maximum power point tracking control is proposed to achieve power curve operating near optimal point. Speed rotor reference can be adjusted by maximum power point tracking fuzzy controller (MPPTFC) such that the turbine operates around maximum power. Power curve model can be modelled by using adaptive neuro fuzzy inference system (ANFIS). It is required to simply well estimate just a few number of maximum power points corresponding to optimum generator rotor speed under varying wind speed, implying its training can be done with less effort. Using the trained fuzzy model, some estimated maximum power points as well as their corresponding generator rotor speed and wind speed are determined, from which a linear wind speed feedback controller (LWSFC) capable of producing optimum generator speed can be obtained. Applied to a squirrel-cage induction generator based wind energy conversion system, MPPTFC and LWSFC could maximize extraction of the wind energy, verified by a power coefficient stay at its maximum almost all the time and an actual power line close to a maximum power efficiency line reference.
Load frequency control in a future power system is investigated. Responses of differential and integral limiters to brown noise are modeled in frequency domain. These models are parameterized by limiting value and frequency band to apply. A small power system composed of a differential limiter, an integral limiter, and a noise source is used to verify the applicability of the proposed methodology.
A new boundary equation is proposed to improve the computation accuracy of charge simulation method, in which analytical derivative of electric field along dielectric surface is effectively implemented in the case of surface charge conduction. The method is verified in a dielectric surface with stepwise-varying conductivity.