Tomonobu Senju

Optimal Operation Method of Smart House by Controllable Loads based on Smart Grid Topology

Abstract From the perspective of global warming suppression and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all electrification apartment house or residence such as DC smart house have increased in recent years. However, due to fluctuating power from renewable energy sources and loads, supply–demand balancing fluctuations of power system become problematic. Therefore, “smart grid” has become very popular in the worldwide. This article presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuations. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuations, it is possible to reduce the maximum electric power consumption and the electric cost. This system consists of photovoltaics generator, heat pump, battery, solar collector, and load. In order to verify the effectiveness of the proposed system, MATLAB is used in simulations.

Optimal Operation Planning of Wind Farm Installed BESS Using Wind Power Forecast Data of Wind Turbine Generators Considering Forecast Error

Abstract In order to solve the problems of global warming and depletion of energy resource, renewable energy systems such as wind generation are getting attention. However, wind power fluctuates due to variation of wind speed, and it is difficult to perfectly forecast wind power. This paper describes a method to use power forecast data of wind turbine generators considering wind power forecast error for optimal operation. The purpose in this paper is to smooth the output power fluctuation of a wind farm and to obtain more beneficial electrical power for selling.

A new method for next-day price forecasting for PJM electricity market

In the framework of the competitive electricity markets, electricity price forecasting is important for market participants in a deregulated electricity market. Rather than forecasting the value, market participants are sometimes more interested interval of the peak electricity price forecasting. Forecasting the peak price is essential for estimating the uncertainty involved in the price and thus is highly useful for making generation bidding strategies and investment decisions. The choice of the forecasting model becomes the important influence factor how to improve price forecasting accuracy. This paper proposes new approach to reduce the prediction error at occurrence time of the peak electricity price, and aims to enhance the accuracy of the next day electricity price forecasting. In the proposed method, the weekly variation data is used for input factors of the ANN at occurrence time of the peak electricity price in order to catch the price variation. Moreover, learning data for the ANN is selected by rough sets theory at occurrence time of the peak electricity price. This method is examined by using the data of the PJM electricity market. From the simulation results, it is observed that the proposed method provides a more accurate and effective forecasting, which helpful for suitable bidding strategy and risk management tool for market participants in a deregulated electricity market.

A Hybrid Control Method for Output Power Smoothing of a PMSG-Based WECS

This paper presents a smoothing method of output power by using pitch angle control, inertia of a wind turbine and DC-Link voltage control of a wind energy conversion system (WECS) using a permanent magnet synchronous generator (PMSG). The output power fluctuations in low and high frequency domains are smoothed by the pitch angle control of the WECS and the DC-Link voltage control, respectively. The remaining frequency, i.e., middle frequency is smoothed by the inertia of the wind turbine. The generator-side converter controls the generator torque of PMSG while the grid-side inverter controls the DC-Link voltage and grid voltage. From the proposed method, the generator torque is smoothed and kinetic energy generated by the inertia of the wind turbine is used to smooth the power fluctuations of the PMSG and wind turbine blade stress is mitigated as the pitch action in high frequency domain is reduced. Due to the DC-Link voltage in this paper by an appropriate operating region, the output power smoothing is achieved with stability and low cost. The effectiveness of the proposed method is validated by numerical simulations.

Control Strategies for Smoothing of Output Power of Wind Energy Conversion Systems

Abstract This article presents a control method for output power smoothing of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG) using the inertia of wind turbine and the pitch control. The WECS used in this article adopts an AC–DC–AC converter system. The generator-side converter controls the torque of the PMSG, while the grid-side inverter controls the DC-link and grid voltages. For the generator-side converter, the torque command is determined by using the fuzzy logic. The inputs of the fuzzy logic are the operating point of the rotational speed of the PMSG and the difference between the wind turbine torque and the generator torque. By means of the proposed method, the generator torque is smoothed, and the kinetic energy stored by the inertia of the wind turbine can be utilized to smooth the output power fluctuations of the PMSG. In addition, the wind turbines shaft stress is mitigated compared to a conventional maximum power point tracking control. Effectiveness of the proposed method is verified by the numerical simulations.

Transient Behavior Analysis of Induction Generator at Three-Phase Fault Condition

In recent years, renewable energy generation has been coming up for effective use of natural energy, such as wind energy. Induction generators consisting squirrel-cage rotors are widely used as wind generators because of their salient features like robust rotor design, simplicity in the construction, maintenance free operation, etc. In this paper, it is derived that the transient current, electromechanical torque, and active power taking into account rotor speed change of induction generators at three-phase fault conditions. The output equations of the induction generator has nonlinearity, and the speed-time characteristic in a fault period is also expressed by the nonlinear equation. The approximation to derive analytical formulas for transient conditions is proposed, and the transient behavior of the induction generator is analyzed by the developed equations. The simulation block diagram in MATLAB/SIMULINK is constituted using the system equation in consideration of the nonlinearity of the induction generator. The simulation results obtained from each theoretical analysis are in close agreement with that of results obtained using MATLAB/SIMULINK simulation. Furthermore, theoretical discussion also developed to determine the fault phase angle and the time at which maximum transient currents flow in the system.

Frequency Control Method using Automated Demand Response for Isolated Power System with Renewable Energy Sources

Abstract In response to mounting concerns regarding environmental problem and depletion of Energy Resources, the introduction of Renewable Energy Sources (RESs), has been advancing in recent years. The system frequency deviation is a serious problem for a RESs-integrated power system. In this paper, we propose a system frequency control method using the automated demand response (ADR) for an isolated power system with RESs. The ADR can automatically adjust the consumption power of appliances after receiving the DR signal. It is assumed that consumption power of controllable loads is automatically varied based on the electricity price information from the real-time pricing (RTP). This method improves the supply-demand balancing, and hence the system frequency control is achieved. Furthermore, the stability of controller is demonstrated by indicating the poles of the control system.

A New Phase Detection Method by Using Kalman Filter

This paper proposes a phase detection method for harmonics and unbalanced voltage conditions. The proposed method uses harmonics and unbalanced voltage compensation circuit in addition to basic PLL (Phase Locked Loop) circuit. In the harmonic compensation circuit, the harmonic voltage component are eliminated from the input voltages using specific harmonic detection method. Besides, frequency information of power system used in the specific harmonic detection method is estimated by an extended complex Kalman filter. In the unbalanced voltage compensation circuit, the input voltage is normalized after the calculated positive sequence component. By means of the proposed method, excellent phase detection performance can be achieved under harmonics and unbalanced voltage conditions. Moreover, detection of positive sequence voltage component becomes possible under voltage drop conditions due to faults in power systems. The effectiveness of the proposed method is verified by simulation results.