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.

Highlights

  • Imbalances between generation and consumption cause frequency variations in a power system [1]

  • To maintain frequency in its nominal value, power systems rely on synchronous machines connected to the grid, which store kinetic energy automatically extracted in response to a sudden power imbalance [2]

  • As they are connected to the grid through inverters which electrically decouple them from the grid [7], the effective inertia of the power system can be reduced [8]

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Summary

Introduction

Imbalances between generation and consumption cause frequency variations in a power system [1]. The massive penetration of II-RES into the grid can involve several issues that should be taken into account [5] As they depend on weather conditions, these sources are intermittent and uncertain, placing stress on Renewable Energy - Technologies and Applications power system operation [6]. As they are connected to the grid through inverters which electrically decouple them from the grid [7], the effective inertia of the power system can be reduced [8]. A methodology to estimate the current rotational inertia of power systems based on their electricity generation mix is proposed.

Inertial response of a synchronous generator: inertia constant
Aggregated swing equation: application to power systems
Hidden and virtual inertia emulation from RES: modified equivalent inertia constant
Inertia estimation for power systems
Preliminaries
PV power plant frequency control strategies
Wind power plant frequency control strategies
Findings
Conclusions
Full Text
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