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Due to the depletion of fossil resources and the increase in carbon dioxide emissions, renewable energy systems (RESs) such as photovoltaic (PV) and wind generator (WG) have become an active player in power systems (PSs). In Japan, diesel generators (DGs) are the means of power generation in most isolated islands. Therefore, the introduction of RESs into these islands is of great importance. However, due to the uncertainty of RESs, battery energy storage systems (BESSs), fuel cells (FCs), and exploiting the electric vehicles (EVs) owned by customers are expected as vital power sources for the next generation. Moreover, demand response programs are utilized in this paper. As a result of reforming PSs in recent years, transactions on power markets have also been increasing in Japan. The Japan electric power exchange provides day-ahead market, intraday hour-ahead market, and forward market. It is expected that these markets make it possible to deal with uncertainties related to the generated power fluctuatio...

A recent trend of the power system is the ever increasing number of distributed generators (DGs) utilizing renewable energy sources, which have output powers that fluctuate due to unpredictable weather and ambient conditions. This causes fluctuations in system frequency and bus voltages, resulting in poor quality power, higher prices for electricity, and increased chances of reverse power flow and voltage collapse. In order to allow higher levels of DG penetration, methods of reducing the effects of fluctuations must be implemented. This paper proposes a method to mitigate these fluctuations using controllable loads such as heat pump water heaters (HPs) and battery storage systems. The HPs are controlled using a decentralized bang-bang (on/off) control based on the cumulative distribution of water temperature of HPs in the local area and the local frequency. Battery systems are controlled using a smart frequency and voltage droop characteristics based control. The decentralized bang-bang control mitigates local frequency fluctuations by increasing active power consumption to lower frequency as well as decreasing active power consumption to increase the frequency. The smart droop characteristics based control applies a commonly used droop characteristics control to voltage and frequency; however, the control system monitors the state of charge (SOC) of the battery system and takes appropriate actions to prevent the SOC from reaching a critical level. The results of simulations show that fluctuations in frequency and bus voltage are mitigated by the application of the proposed control methodologies without adversely affecting the comfort level of consumers.

This paper proposes an uninterruptible all-electric smart house equipped with photovoltaic system and storage battery. There is a control delay in the conventional control system, because the system uses root mean square or average values for the control method. Therefore, it causes transient currents when load variation and system faults occur. The transient current adversely affects the in-house loads (e.g., precision equipment). In this paper, the control delay is reduced by using a control system with single-phase dq-transformation information. Therefore, the smart house achieves a reduction of the transient current caused by load variation and system faults through the use of instantaneous inverter control. The effectiveness of the proposed method is verified by simulation results given by the Matlab/SimPowerSystems® environment.

In recent years, the increased use of renewable energy sources (especially photovoltaic (PV) systems) has been remarkable, and use is growing because of considerations for environmental problems. However, renewable energy sources dependent on weather conditions, such as PV systems, cause output power fluctuations. In an electric distribution system, many PV systems are connected with distribution lines, and PV systems generate unstable power and inject unbalanced power to each line. Therefore, it is possible for voltage imbalance to occur in three-phase distribution systems. In this paper, we propose a method of voltage imbalance compensation by injecting active and reactive power using inverters in Power Conditioning Systems connected to smart houses. If voltage imbalance compensation is executed considering only the distribution voltage, there is a concern that the voltage at the power receiving end will deviate. Therefore, the optimum quantity of power injection is decided depending on the proper rate ...

DC smart house is receiving attention as means for the management of electric power. Since many domestic appliances are also DC devices, the DC smart house can also reduce conversion losses. Recently, the increased introduction of residential photovoltaic generators (PV) has been remarkable. However, since the output power of PV fluctuates according to weather conditions and is commonly allowed to flow into the power grid, it is difficult for the supply side to balance supply and demand. The purpose of this study is to prevent the fluctuations of the PV output power connected to the DC smart house from flowing into the power system. This paper proposes compensation methods for fluctuations in the output power of the PV as well as those caused by consumption power of uncontrollable loads. The proposed scheme achieves a stable constant active power interconnection point between the smart house and the grid by cooperative operation of Electric Vehicle (EV) and Electric Water Heater (EWH). The control scheme of both the EV and the EWH uses the H∞ control method. H∞ control improves the control performance because the gain can be regulated according to the frequency domain. The proposed scheme is tested by comparing with two other cases, of which the control group comprises no-controller for each device and Proportional-Integral (PI) controllers for each device. In the no-control scenario, these devices follow a randomly generated load profile. The effectiveness of the proposed method is verified by simulation results in the MATLAB/Simulink® environment.