A Review of Virtual Inertia Techniques for Renewable Energy-Based Generators

Abstract

Over recent decades, the penetration of renewable energy sources (RES), especially photovoltaic and wind power plants, has been promoted in most countries. However, as these both alternative sources have power electronics at the grid interface (inverters), they are electrically decoupled from the grid. Subsequently, stability and reliability of power systems are compromised. Inertia in power systems has been traditionally determined by considering all the rotating masses directly connected to the grid. Thus, as the penetration of renewable units increases, the inertia of the power system decreases due to the reduction of directly connected rotating machines. As a consequence, power systems require a new set of strategies to include these renewable sources. In fact, 'hidden inertia,''synthetic inertia' and 'virtual inertia' are terms currently used to represent an artificial inertia created by inverter control strategies of such renewable sources. This chapter reviews the inertia concept and proposes a method to estimate the rotational inertia in different parts of the world. In addition, an extensive discussion on wind and photovoltaic power plants and their contribution to inertia and power system stability is presented.

Analysis and Improvement of an Algorithm for the Online Inertia Estimation in Power Grids with RES

“…We carried out a systematic analysis of the effect of W on the quality of data fitting and subsequent inertia constant estimation, in terms of⌫ 0 and RMSE 0 . The results with n = 1 and W 2 [5,100]s are shown in Fig. 3.…”

“…Recently, the penetration of renewable energy sources (RES), such as photovoltaic (PV) and wind power plants, has become more and more prominent [3], also due to environmental policies and limited fossil fuel reserves. On the other hand, the presence of converter-interfaced generation reduces the global inertia of the system, thus compromising stability and reliability of power systems [4], [5]. To combat the decrease in system inertia and effectively integrate RES into power grids, various control strategies able to provide synthetic inertia have been developed [6], [7].…”

Inertia Pricing in Stochastic Electricity Markets

“…Therefore, power systems with a high penetration of inverter-interfaced RES require new frequency control technologies that replenish the inertial response of retired conventional power plants with spinning synchronous generators for sudden power imbalance. Such technologies are commonly referred to as virtual (or hidden, emulated, synthetic) inertia [5]. To co-optimize the procurement of energy, reserve and inertia services in renewable-rich power systems, this paper formulates a chance-constrained unit commitment (CC-UC) problem that internalizes (i) RES uncertainty and resulting reserve requirements and (ii) inertia requirements.…”

An Adaptive Control Scheme for Variable Speed Wind Turbines Providing Frequency Regulation in Isolated Power Systems with Thermal Generation

“…As a consequence, the first approach (deloading technique) consists of operating the VSWTs in a suboptimal power point p del , below p MPP (s w ). Therefore, a certain amount of power ∆p d can be supplied in case of a power imbalance [23,24]. Two different possibilities are identified [25]: (i) the pitch-angle control and (ii) over-speed control.…”