Hajime Miyauchi

Elasticity coefficient of climatic conditions for electricity consumption analysis

The aim of this work is to analyze factors influencing electricity consumption in Japan using regression analysis. Every season regression models are developed for forecasting and determining elasticity coefficient associated with climatic conditions. As explanation variables, we use temperature, relative humidity and other factors such us holidays. Then, several statistical tests, for instance, t-test, adjusted coefficient R2 and Durbin-Watson statistic test, are used to validate the models. As an error analysis, MAPE is used to evaluate the forecasting performance. The results indicate that almost all explanation variables of the 4 seasonal models with different time period have significant influence. The models with autoregressive concerning the error term give better forecasting than without autoregressive term. Moreover, 2 scenarios are tested for each season to observe further the effect of changing climatic conditions to the electricity demand.

Risk assessment of power plant investment by three level ordered probit model considering project suspension

Under the deregulation in electricity, electrical power industries encounter may risks. The electrical power supplier should evaluate future uncertainty adequately and plan an appropriate investment project. Therefore, it is necessary to develop a new method to evaluate the risks for the investment. We have already proposed two new asset evaluation methods. One is the method using a net present value based on utility indifference pricing (UNPV method) and the other is probit model which simplifies UNPV method. We have checked their effectiveness through the project evaluation of a gas thermal power plant. In this paper, we propose three level ordered probit model. In the conventional probit model, we pay attention only to execution and rejection of the project. Some project should be suspended because the evaluation of the project is positive, but relatively low. In the new three level ordered probit model, we introduce suspension status for the project evaluation adding to execution and rejection. We apply it to the project evaluation of gas thermal power plant and show the effectiveness of the new method.

Fuzzy logic stabilizing control of power systems by SMES with consideration to loss in inverter unit

Abstract In the electric power system getting more and more complicated recently, the new measure against stabilization control of power systems is becoming important. Superconducting magnetic energy storage (SMES) attracts all of our attentions as the efficient electric power storage equipment. As the electric power can be charged and discharged at high speed, SMES stabilizes the power system if it is properly controlled. We have been experimenting the stabilizing control of power systems using a 50 kJ SMES and one machine infinite bus system. The fuzzy logic type switching control with consideration to loss in the inverter–converter unit is applied to SMES to stabilize power systems. In this paper, the result of the stabilization control experiments of the power system is stated. The proposed fuzzy logic type switching control is equal to or more effective than the conventional method which does not take loss in consideration.

A Load Frequency Control in an Off-Grid Sustainable Power System Based on a Parameter Adaptive PID-Type Fuzzy Controller

Abstract This paper presents a new implementation of a parameter adaptive PID-type fuzzy controller (PAPIDfc) for a grid-supporting inverter of battery to alleviate frequency fluctuations in a wind-diesel power system. A variable speed wind turbine that drives a permanent magnet synchronous generator is assumed for demonstrations. The PAPIDfc controller is built from a set of control rules that adopts the droop method and uses only locally measurable frequency signal. The output control signal is determined from the knowledge base and the fuzzy inference. The input-derivative gain and the output-integral gain of the PAPIDfc are tuned online. To ensure safe battery operating limits, we also propose a protection scheme called intelligent battery protection (IBP). Several simulation experiments are performed by using MATLAB®/SimPowersystems™. Next, to verify the scheme’s effectiveness, the simulation results are compared with the results of conventional controllers. The results demonstrate the effectiveness of the PAPIDfc scheme to control a grid-supporting inverter of the battery in the reduction of frequency fluctuations.

Optimal Energy Utilization of Photovoltaic Systems Using the Non-Binary Genetic Algorithm

Abstract The article presents the energy model development based on the real-time output power of PV system installations at Kumamoto University, Japan. There are four sites of installation inside the university, which consist of two locations with thin-film silicon (5.76 kW and 7.56 kW) in the Faculty of Engineering and in the Faculty of Engineering Research Building, respectively, monocrystalline silicon (50 kW) in the Research Laboratory, and CIGS (30 kW) on the rooftop of the Forico Building. From the real-time output power information in one week continuous measurement during winter and summer in 2013, the accumulative energy and capacity factor are calculated. These data are then used as the raw information for developing an energy model in order to estimate the energy production based on capacity factor. The optimal capacity factor is obtained using the non-binary genetic algorithm (NB-GA). Obtaining the optimal capacity factor is important for the prediction of accumulative energy output following the forecasted meteorological information.

Value assessment of power generation project by UNPV method considering scale effects

Power generation project may face a big risk because of the large amount of investment money. Therefore, it is necessary to develop a new method to evaluate the risks for the investment. We have already proposed two new asset evaluation methods. One is the method using a net present value based on utility indifference pricing (UNPV method) and the other is probit model which simplifies UNPV method. In this paper, we propose UNPV method considering the scale effect. A conventional UNPV method evaluates a power generation project per 1kW. Therefore, it takes no consideration of the scale risk. By considering the scale effect, we can calculate optimal investment scale and maximum allowable scale. We apply it to the project of photovoltaic system and show the effectiveness of the new method.

Fuzzy logic switching of FACTS devices for stability enhancement

This paper presents a new switching control scheme for FACTS devices such as high speed phase shifter, thyristor controlled series capacitor modules, braking resistor, and static var compensator, using a fuzzy logic to enhance overall stability of electric power systems. All the FACTS devices are set on one of the buses including generator terminals in transmission systems. The real power flow at the location of the FACTS devices is utilized to determine the thyristor switching. Because the switching control scheme is simple, it does not require heavy computation on the micro-computer based switching controller. The same fuzzy logic switching control scheme is applied to all of the FACTS devices. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme.

A new control design of maximum power point tracking by fuzzy logic controller for wind turbine connected to low voltage grid

This paper proposed a new control method based on fuzzy logic controller to control the maximum power point tracking in wind turbine system connected to the low voltage grid. To achieve maximum power conditions, the wind turbine must be at the optimum voltage conditions, to shift the actual voltage to the optimum voltage is used boost converter. The simulation shows that the power of wind turbine can be increased 51.11%, quality voltage and frequency to be better by using this new control.

Reliability assessment of small power system with dispersed generators in isolated island

Recently, as it is important to reduce CO2 emission, dispersed generators such as photovoltaic system (PV) and wind turbine generator (WTG) are introduced aggressively. A small power system in such an isolated island is sensitive to output fluctuation of dispersed generators because total generator capacity of the system is small. To reduce the fluctuation, many researches have been studying how to control the fluctuation. Though it is important to smooth the output of the generator, we think the reliability is a more important issue when the dispersed generators are introduced in small systems. In this paper, we discuss on the reliability of a small isolated power system with dispersed generators. We investigate how much capacity of PV or WTG is equivalent to a diesel generator from the viewpoint of supply reliability. Thus, we will make clear the required capacity of dispersed generator to secure the reliability of a power system. The method and results of this analysis for a small island system can be applied to a smart grid.

Value evaluation of ancillary service offered by energy storage systems

Under the deregulation of the electric power industry, the provision of ancillary service takes on an important role. Energy storage systems can provide ancillary service in addition to generators. However, as energy storage systems are still quite expensive, it would be helpful to estimate the potential revenue from the ancillary service. The value of ancillary service related to active power, for example, the frequency control, is relatively easy to estimate. On the other hand, the value of ancillary service related to reactive power is difficult to estimate. In this paper, we propose a new method for assessing the value of reactive power provided by energy storage systems. Reactive power from the energy storage system benefits power systems such as the increase of energy transactions, reduction of transmission losses and voltage sustainability. Reactive power is assessed by converting these benefits into active power causing the same effect.