Inertia

About: Inertia is a research topic. Over the lifetime, 12006 publications have been published within this topic receiving 164291 citations.

Virtual synchronous generator control in autonomous wind-diesel power systems

Abstract: This paper addresses the problem of frequency stability in an autonomous wind-diesel power system with energy storage. At high wind penetration levels and due to the lack of controlled rotating machines, wind fluctuation might cause unacceptable frequency excursions in the system and they need to be mitigated. A virtual synchronous machine control is designed to emulate a virtual inertia via power injection from/to the energy storage system. The impact of this control strategy on the system is analyzed. Based on the case study, the major conclusion is that virtual inertia control reduces the maximum rotor speed deviation, but in exchange for increasing the inertia, the system becomes slower and more oscillatory. Possible solutions for the latter are pointed out, but further work is required. Parameters for sizing the energy storage are proposed.

Optimal Placement of Virtual Inertia in Power Grids

Abstract: A major transition in the operation of electric power grids is the replacement of synchronous machines by distributed generation connected via power electronic converters. The accompanying "loss of rotational inertia" and the fluctuations by renewable sources jeopardize the system stability, as testified by the ever-growing number of frequency incidents. As a remedy, numerous studies demonstrate how virtual inertia can be emulated through various devices, but few of them address the question of "where" to place this inertia. It is however strongly believed that the placement of virtual inertia hugely impacts system efficiency, as demonstrated by recent case studies. In this article, we carry out a comprehensive analysis in an attempt to address the optimal inertia placement problem. We consider a linear network-reduced power system model along with an H2 performance metric accounting for the network coherency. The optimal inertia placement problem turns out to be non-convex, yet we provide a set of closed-form global optimality results for particular problem instances as well as a computational approach resulting in locally optimal solutions. Further, we also consider the robust inertia allocation problem, wherein the optimization is carried out accounting for the worst-case disturbance location. We illustrate our results with a three-region power grid case study and compare our locally optimal solution with different placement heuristics in terms of different performance metrics.

Equations of motion for a two-axes gimbal system

Abstract: Equations of motion for the two-axes yaw-pitch gimbal configuration are discussed on the assumption that the gimbals are rigid bodies and have no mass unbalance. The equations are derived and different terms are brought together into separate groups for the sake of clarity and to facilitate certain interpretations. Different kinds of disturbances and their elimination or reduction are discussed, as is the yaw gain dependence on the pitch angle. Inertia cross couplings are also given. The purpose is twofold: to simplify the picture of the two-axes gimbals and to further illustrate the properties of this configuration.

Method for determining inertia effects for a hybrid powertrain system

Abstract: A method for controlling a hybrid powertrain system based upon determined inertial effects for a continuously variable operating range state includes monitoring an operator torque request and a rotational speed of the output member, determining an inertial effect on an input speed of the input member for a continuously variable operating range state, and controlling motor torque outputs from the electric machines to meet the operator torque request based upon the inertial effect on the input speed of the input member.