Is a 100% renewable European power system feasible by 2050?

Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. ‘Hidden inertia’, ‘synthetic inertia’ or ‘virtual inertia’ are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper.

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Power systems with high renewable energy sources: A review of inertia and frequency control strategies over time

http://dspace.uniten.edu.my/jspui/bitstream/123456789/13396/1/Gridconnected-renewable-energy-sources-Review-of-the-recent-integration-requirements-and-control-methodsJournal-of-Cleaner-Production.pdf

Grid-connected renewable energy sources: Review of the recent integration requirements and control methods

The utilization of power electronic inverters in power grids has increased tremendously, along with advancements in renewable energy sources. The usage of power electronic inverters results in the decoupling of sources from loads, leading to a decrease in the inertia of power systems. This decrease results in a high rate of change of frequency and frequency deviations under power imbalance that substantially affect the frequency stability of the system. This study focuses on the requirements of inertia and the corresponding issues that challenge the various country grid operators during the large-scale integration of renewable energy sources. This study reviews the various control techniques and technologies that offset a decrease in inertia and discusses the inertia emulation control techniques available for inverters, wind turbines, photovoltaic systems, and microgrid. This study attempts to explore future research directions and may assist researchers in choosing an appropriate topology, depending on requirements.

Future low-inertia power systems: Requirements, issues, and solutions - A review

Integration of inverter-interfaced distributed generators (DGs) via microgrids into traditional power systems reduces the total inertia and damping properties, while increasing uncertainty and sensitivity to the fault in the system. The concept of the virtual synchronous generator (VSG) has been recently introduced in the literature as a solution, which mimics the behavior of conventional synchronous generators in large power systems. Parameters of the VSGs are normally determined comparing the conventional synchronous generators. This paper introduces an extended VSG for microgrids by combining the concept of virtual rotor, virtual primary, and virtual secondary control as a virtual controller to stabilize/regulate the system frequency. An $H_{\infty }$ robust control method is proposed for robust\optimal tuning of the virtual parameters. The effectiveness of the proposed control methodology is verified via a microgrid test bench.

Robust Frequency Control of Microgrids Using an Extended Virtual Synchronous Generator

Preservation of the environment has become the main motivation to integrate more renewable energy sources (RESs) in electrical networks. However, several technical issues are prevalent at high level RES penetration. The most important technical issue is the difficulty in achieving the frequency stability of these new systems, as they contain less generation units that provide reserve power. Moreover, new power systems have small inertia constant due to the decoupling of the RESs from the AC grid using power converters. Therefore, the RESs in normal operation cannot participate with other conventional generation sources in frequency regulation. This paper reviews several inertia and frequency control techniques proposed for variable speed wind turbines and solar PV generators. Generally, the inertia and frequency regulation techniques were divided into two main groups. The first group includes the deloading technique, which allow the RESs to keep a certain amount of reserve power, while the second group includes inertia emulation, fast power reserve, and droop techniques, which is used to release the RESs reserve power at under frequency events.

Inertia response and frequency control techniques for renewable energy sources: A review

Recently, several environmental problems are beginning to affect all aspects of life. For this reason, many governments and international agencies have expressed great interest in using more renewable energy sources (RESs). However, integrating more RESs with distribution networks resulted in several critical problems vis-a-vis the frequency stability, which might lead to a complete blackout if not properly treated. Therefore, this paper proposed a new Under Frequency Load Shedding (UFLS) scheme for islanding distribution network. This scheme uses three meta-heuristics techniques, binary evolutionary programming (BEP), Binary genetic algorithm (BGA), and Binary particle swarm optimization (BPSO), to determine the optimal combination of loads that needs to be shed from the islanded distribution network. Compared with existing UFLS schemes using fixed priority loads, the proposed scheme has the ability to restore the network frequency without any overshooting. Furthermore, in terms of execution time, the simulation results show that the BEP technique is fast enough to shed the optimal combination of loads compared with BGA and BPSO techniques.

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Mohammad Dreidy

Papers

Inertia response and frequency control techniques for renewable energy sources: A review

Application of Meta-Heuristic Techniques for Optimal Load Shedding in Islanded Distribution Network with High Penetration of Solar PV Generation