[in Japanese]

View full abstract

Battery Energy Storage system (BESS) is prospective energy storage in Smart Grid and Hybrid Energy Storage System (HESS) composed of two different kinds of battery is also studied to achieve better performance and lower cost than single kind of BESS. The cost issue, however, has not been evaluated explicitly so far. On the other hand, BESS is studied and expected for ancillary service although HESS has not been applied to frequency control in power system. This paper focuses on HESS application to frequency control and its economic analysis. In this paper, the important battery characteristics in the application to power system are introduced and two kinds of HESS are evaluated in terms of their cost when they are applied to frequency control. In addition, the cost is analyzed for when HESS is used for Peak Shift as well as frequency control.

View full abstract

Recently, the installed capacity of photovoltaic (PV) systems has been increasing rapidly due to the enforcement of the feed-in tariff scheme in Japan. However, the reverse power flow from the roof-mounted PV systems could cause the voltage unbalance such as voltage-rises in distribution network. Conventionally, the voltage is adjusted by the reactive power compensation using SVC (Static Var Compensator) installed in the high-voltage distribution network. On the other hand, reactive power compensation using demand side equipment such as EV chargers in the low-voltage distribution network is promising as cost-effective. This paper proposes an evaluation method for economic value of reactive power compensation. Using this method, we evaluated the cost-effectiveness of the demand side equipment, and compared it with SVC. As a target cost, we revealed an annual equipment cost of the demand side equipment that achieves the same cost saving as SVC.

View full abstract

This paper aims at estimating daily load profiles of plug-in electric vehicle (EV) considering destination charging in Japan. Using the road traffic census data on passenger vehicles, we reveal the charging load at 30% EV penetration. Assuming that EVs are charged at their garages and commercial facilities, we show that the load profile on weekdays has three peaks and that the highest occurs in the evening. When EVs can also be charged at users' workplaces after commuting, the charging peak in the morning becomes higher. On weekends, a highest charging peak occurs in the evening, which is lower than that on weekdays. We also show impacts of charging power and battery capacity of EVs on load profiles. In addition, we assume a charging scenario for weekends where EVs parked all day are utilized in order to consume power generated from photovoltaic (PV) systems. If we can effectively employ EVs parked all day, which account for 48% of all EVs, they would improve the situation with their large charging potential to consume power from PV systems.

View full abstract

In recent years there has been a growing interest in the ecofriendly technologies like residential Photovoltaic (PV) systems and Electric Vehicle (EV). PV systems and the EVs will contribute to reduce CO₂ emissions in the residential sector and the transportation sector respectively. In spite of that, high penetration of the PV system into the power grid can cause grid voltage and frequency stability problems. Also the growth of the EV market will create an extra electricity load (for charging EV fleet) leading to increase the power utility fuel cost.  In this research we proposed the usage of the PV-EV system as a method to mitigate the impact of spreading of the residential PV system and EV on the power grid. We built a PV-EV system simulation model and investigated the PV-EV system contribution in the balance of supply and demand of power and in reducing the total power cost of the household under different electricity pricing scenarios. Also we evaluated the effect of forecast uncertainty of load and PV output on the performance of PV-EV system.

View full abstract

This paper presents an online method for estimating actual load and photovoltaic generation (PV) output in distribution system with PV actual activated capacity estimation. In recent years, it is planned to introduce the renewable energy on a large scale into the power system in order to achieve the low carbon society. However, PV has a negative effect on the distribution system. When PV is introduced on a large scale into distribution system, it is difficult to know accommodating amount of load in accident restoration. Because measured load contains load in consumers and PV output. Thus, it is necessary to estimate actual load and PV output online in distribution system. This paper proposes the hybrid method of independent component analysis (ICA) and PV actual activated capacity estimating method. The former has new formulation that is inputted active power of load and insolation. The latter estimates PV actual activated capacity from results of ICA. The effectiveness of the proposed method is demonstrated using actual data of load in consumers that is regulated reactive power. The proposed method can estimate actual load and PV output more accurately than a conventional method. Moreover, the proposed method can estimate them accurately even if load is changed rapidly.

View full abstract

This research focuses on use of heat pump air-conditioning system (HPACS) as controllable load in microgrid to compensate short-term power fluctuation. A new designing method to determine control parameters for microgrid including HPACS power consumption control is proposed. The proposed method uses microgrid's transfer function and frequency spectrum of microgrid's power and heat demand fluctuation to calculate evaluation values of microgrid control. The search result of Pareto-optimal parameter combination shows that there is a trade-off between SOC fluctuation, stored heat fluctuation, and fluctuation suppression ability. A verification test of power fluctuation compensation using HPACS control is conducted using a microgrid testing facility. The results of experiment shows that power consumption control of HPACS can reduce SOC fluctuation of battery on a large scale. The trade-off relation between evaluation values that was found in parameter decision method was affirmed by the experiment.

View full abstract

More and more dispersed power sources will be introduced to achieve a low-carbon society in recent years. However, many problems may occur when they are introduced too much in the current power system. For example, it can cause a delay or impossibility of fault detection due to the decline of the protective relay sensitivity. This paper proposes a new system of protective relays for distribution lines using section switches with sensors to solve the problem. In addition, this paper shows the experimental results of the proposed system composed of Intelligent Electronic Devices based on IEC 61850.

View full abstract

After the Fukushima nuclear accident, Japanese power generation planning needs to be rearranged reflecting on the technical movement in both power supply and demand sides; Fukushima nuclear accident has complicated the positioning of nuclear energy in Japan's long-term power generation mix due to its public acceptance and other associated issues such as nuclear waste management; the studies are more required about the maximum grid integration of variable renewables such as PV and wind power which are expected to potentially replace nuclear energy; in power demand side, an expected future introduction of electric vehicle (EV) and plug-in hybrid vehicle (PHEV) will have an impact on the grid management in electric power system. In this context, it is important to develop a computational tool to comprehensively analyze the optimal power generation mix and dispatch in a consistent way. This paper develops a dynamic high time-resolution optimal power generation mix model, as large-scale linear programming model with 18 million constraints and 8 million endogenous variables, and analyzes the optimal deployment of variable renewables (VR) and electric vehicles, considering the future possible nuclear scenario and CO₂ regulation policy in Japan. As calculated optimal solutions, electric vehicle plays an important role to integrating variable renewable and treating the imbalance of VR surplus output.

View full abstract

We have developed control system for micro-grid in which a battery compensates fluctuation by solar generation and electrical load. This paper describes an evaluation of control parameters (compensated band, output's initial value) for battery control to obtain peak demand reduction by the micro-grid. We show that by applying this method, amount of peak demand reduction has little influence of prediction error and reliability of this method is verified by two kinds of demand profiles in summer and winter. These results show that the method has applicability to the micro-grid operation.

View full abstract

This paper discusses the demonstration result and business method of peak shifting using battery aggregation technology by the unique demand response method that does not request customers to reduce demand, and shows reality of this method.

View full abstract

The 25th Power and Energy Society Annual Conference was held on September 10 - 12, 2014 at Doshisha University in Kyoto. The total number of technical papers was 363, and technical sessions were 43 (42 oral sessions and 1 poster session). A special lecture and a panel discussion were organized. All events were very well attended and the final enrollment attained to 994 registrations. The conference was successfully closed by the great contribution of all participants. The outline of the conference is reported in this article.

View full abstract