The increasing demand of the data center's computational capacity in recent years has introduced new data center operational challenges among others to maintain the service level agreements (SLA) and quality of services (QoS), while at the same time limiting energy consumption. In this paper, a stochastic operational risk assessment approach is presented that estimates the required number of spare servers in a data center considering the risk of servers’ failure in operation since servers define the computational capability of a data center. A reliability index called “risk of computational resource commitment (RCRC)” is introduced that quantifies the probability of having insufficient spare servers due to failures during the operational lead time, and the complement of the RCRC shows the ability of the resources to maintain SLA of a data center. The failure rates of the servers are obtained using a Monte Carlo Simulation with the failure data, published by Google in 2019. The analysis shows that the RCRC reduces with the increasing number of spare servers, while it also stresses the energy efficiency of the data center. The RCRC index could be used in data center operation to avoid overprovisioning of the servers and to limit the number of spare servers in the data center, while creating a suitable balance between QoS and energy consumption of the data centers.

This paper assesses the communication, information, and functional requirements of virtual power plants (VPPs). A conceptual formulation of the interoperability requirements, as well as a comparative study of their fulfillment by state-of-the-art communication techniques, is presented. VPP requirements are then mapped against services and information models of IEC 61850 and common information model (CIM) power utility automation standards. Proposals are given for extensions of the IEC 61850 standard to enhance the interaction between the VPP controller and the distributed energy resources. Finally, the methodology and concepts are applied to a specific VPP consisting of hydro and wind plants, solar photovoltaic (PV) power, and storage facilities. Several applications to provide grid services from the proposed VPP in an existing 50-kV grid are covered. The implementation of the VPP communication and control architecture in the supervisory control and data acquisition (SCADA) of demonstration plant is also presented.

Power system transients cause problems and disturbances that might be harmful to electronic equipment. However, very little has been done to systematically understand and analyze power system transients. There is also a lack of computational effective methods as transients are short and associated with a wide range of events and system conditions. This paper addresses the following issues: (1) to categorize the power system transients according to their underlying causes; (2) to propose a signal processing method, ESPRIT, for the analysis of a range of transients due to different causes. Experimental results are included to evaluate the usefulness of ESPRIT in power system transient analysis. Remaining open issues for research are also discussed.

Utility deregulation will have tangible and intangible effects on power quality requiring industry-wide action to maintain adequate standards. These effects are discussed in the first part of the paper. The increasing trend towards more extensive use of power electronic control at the generation, transmission and utilization systems following deregulation has power quality implications that will affect the standards, system simulation and monitoring tools. The paper reviews the present methods available in these areas to achieve specified levels of power quality in the deregulated environment.