Yousuke Nozaki

Toward intelligent machine-to-machine communications in smart grid

The advanced metering infrastructure of the smart grid presents the biggest growth potential in the machine-to-machine market today. Spurred by recent advances in M2M technologies, SG smart meters are expected not to require human intervention in characterizing power requirements and energy distribution. However, there are many challenges in the design of the SG communications network whereby the electrical appliances and smart meters are able to exchange information pertaining to varying power requirements. Furthermore, different types of M2M gateways are required at different points (e.g., at home, in the building, at the neighborhood, and so forth) of the SG communication network. This article surveys a number of existing communication technologies that can be adopted for M2M communication in SG. Among these, the most reliable technology to facilitate M2M communication in the SG home area network is pointed out, and its shortcoming is also noted. Furthermore, a possible solution to deal with this shortcoming to improve SG communications scalability is also presented.

An early warning system against malicious activities for smart grid communications

Smart grid presents the largest growth potential in the machine-to-machine market today. Spurred by the recent advances in M2M technologies, the smart meters/sensors used in smart grid are expected not to require human intervention in characterizing power requirements and energy distribution. These numerous sensors are able to report back information such as power consumption and other monitoring signals. However, SG, as it comprises an energy control and distribution system, requires fast response to malicious events such as distributed denial of service attacks against smart meters. In this article, we model the malicious and/or abnormal events, which may compromise the security and privacy of smart grid users, as a Gaussian process. Based on this model, a novel early warning system is proposed for anticipating malicious events in the SG network. With the warning system, the SG control center can forecast such malicious events, thereby enabling SG to react beforehand and mitigate the possible impact of malicious activity. We verify the effectiveness of the proposed early warning system through computer-based simulations.

Toward secure targeted broadcast in smart grid

Significant research efforts have recently been directed toward materializing smart grid for the purpose of transforming the aging power grid into an efficient and intelligent electric power distribution system. Conceptually, smart grid can be regarded as a fusion of different advanced technologies (i.e., electrical power engineering meets sensing, control, digital communication, and network information technologies). However, when these advanced technologies converge at smart grid, we will face many unforeseen challenges, particularly security challenges in smart grid communications. In this article, toward secure targeted broadcast in smart grid, we investigate the applicability of Attribute Based Encryption (ABE) for smart grid communication scenarios. In particular, we focus on the application of Key Policy ABE (KPABE), where a smart grid control center can use KP-ABE to broadcast a single encrypted message to a specific group of users, and each user in the targeted group can individually use the defined key policy to decrypt the message. With this kind of KP-ABE targeted broadcast, it is possible to eliminate the need for issuing multiple unicast messages. As a result, both communication and computation efficiency can be ensured.

A survey of game theoretic approaches in smart grid

The concept of smart grid to transform the age-old power grid into a smart and intelligent electric power distribution system is, currently, a hot research topic. Smart grid offers the merging of electrical power engineering technologies with network communications. Game theory has featured as an interesting technique, adopted by many researchers, to establish effective smart grid communications. The use of game theory, to date, has offered solutions to various decision making problems, ranging from distributed load management to micro storage management in smart grid. Interestingly, different researchers have different objectives or problem scopes for adopting game theory in smart grid. Nevertheless, all the game theoretic approaches for making effective smart grid solutions have a common aspect, namely the Nash equilibrium, arriving at which may lead to an optimal solution to the relevant problem. In this paper, we survey a number of game theory-based applications to solve different problems in smart grid. This survey reveals that game theory can be apparently simple yet become an effective technique to facilitate intelligent decision making in smart grid frameworks.

Developing of higher voltage direct-current power-feeding prototype system

High efficiency power feeding systems are effective solutions for reducing ICT power consumption of ICT equipment, such as routers and servers, or high efficiency cooling systems. We developed a higher voltage direct current (HVDC) power feeding system prototype. This system is composed of a rectifier, power distribution cabinet, batteries, and ICT equipment. The configuration is similar to a −48 V DC power supply system. The output of the rectifier is 100 kW, and the output voltage is 401.4 V. We describe the advantage of an HVDC power feeding system and show that its basic characteristics are stable.

Optimal Scheduling Using Metaheuristics for Energy Networks

This paper describes an optimal scheduling technology for determining the operating schedule of an energy network that minimizes CO2 emission or energy costs over a one-day or several-day period. This technology was implemented in Aichi, Japan, at Expo 2005 and at Central Japan Airport City. In the demonstrative research, the optimal scheduling of various energy sources was computed automatically, and then the results by applying a tabu search and genetic algorithm were assessed comparatively.

Development of power distribution cabinet for higher-voltage direct-current power feeding system

Reducing the feeding loss of information and communications technology equipment, such as servers and routers, is very effective for reducing the total power consumption in data centers and telecommunication buildings. In this paper, the structure and function of a higher-voltage direct-current (HVDC) power feeding system prototype is presented. This system was developed to reduce power delivery and conversion losses by using 380 V DC. For operational safety, a floating ground system with an earth detector is applied and a fuse and circuit breaker in the power distribution cabinet work in cooperation. The system voltage is around 380 V, and the output power of the rectifier is 100 kW. We describe the advantages of an HVDC power feeding system and show that its basic characteristics are stable.

A novel demand control policy for improving quality of power usage in smart grid

Smart grid has emerged as a promising technology for enabling bi-directional communication between the power company and its users to facilitate intelligent, robust, and resilient next generation power grid systems. Through this technology, both the power company and its subscribers can be equally benefited, not only from economic point of view, but also in terms of environment-friendly quality of power usage. One important challenge for the smart grid designers is the demand side management, which can lead to avoiding the peak hours and reducing the cost for the consumers. In this paper, we address the power balancing challenge for the smart grid and discuss different solutions including game theoretic methods and demand control policies. Also, we present our novel demand control policy for achieving an effective management of the power consumption. Computer simulations demonstrate the effectiveness of the proposed policy compared to existing ones.

Basic study on grounding system for high-voltage direct current power supply system

The relationship between grounding systems and a high-voltage direct current (HVDC, 380-V DC) power supply system is presented. To assess the effect of grounding system configurations, a simple model of the HVDC power supply system was assumed, and two typical grounding models were evaluated. The noise emission level (conductive disturbance) was measured by using a prototype HVDC rectifier. By use of the measurement results and evaluations, the advantages and disadvantages of these grounding systems are discussed.

Stability analysis of high-voltage DC power distribution system including long feeders

This paper reports on the stability condition of the DC 300-V distribution network of a demonstrative project on power supply systems offering different service levels analyzed by SPICE simulation. To improve the simulation accuracy, we measured some characteristics of actual devices and incorporated them into the simulation models. Using these models, we repeated the simulation and evaluation of network stability while changing both the length of the feeders and the capacitance of the capacitors in the network. Finally, the relationship among those values required to keep the network stable was derived.