Emulating Rotational Inertia of Synchronous Machines by a New Control Technique in Grid-Interactive Converters

Meysam Saeedian,Bahram Pournazarian,Edris Pouresmaeil,Bahman Eskandari,S Sajjad Seyedalipour

doi:10.3390/su12135346

Meysam Saeedian, Bahram Pournazarian + Show 3 more

Open Access

https://doi.org/10.3390/su12135346

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Abstract

Integration of renewable energy sources (RESs) into power systems is growing due to eco-friendly concerns and ever-increasing electricity demand. Voltage source converters (VSCs) are the main interface between RESs and power grids, which have neither rotational inertia nor damping characteristics. Lack of these metrics make the power grid sensitive to frequency disturbances and thereby under frequency, to load shedding activation or even large-scale collapse. In this regard, the contribution of this paper is to develop a new control technique for VSCs that can provide virtual inertia and damping properties with the DC-link capacitors inhered in the DC-side of grid-tied VSCs. The applied VSC is controlled in the current controlled model, with the capability of injecting extra active power with the aim of frequency support during perturbations. The dynamics assessment of the proposed platform is derived in detail. It is revealed that the control scheme performs in a stable region even under weak-grid conditions. Finally, simulations are conducted in MATLAB to depict the efficacy and feasibility of the proposed method. The results show that frequency deviation is mitigated under step up/down changes in the demand, and the rate of change of frequency is improved by 47.37% compared to the case in which the synthetic inertia loop is canceled out.

Highlights

The major portion of electricity demand is generated by synchronous generators (SGs), which have inherent rotational inertia and damping properties
The kinetic energy preserved in the rotational mass of the SGs is highly important in the primary control, which imposes a limit on the frequency oscillations and slows down frequency dynamics [2,3]
Motivated by conventional SG dynamics, the concept of providing synthetic inertia using virtual synchronous generators (VSGs) VSGs was introduced in 2007 [11]. This method emulates the inertial response of real SGs by the grid-connected voltage source converters (VSCs) through a control technique, resulting in fast frequency support during contingencies

Summary

Introduction

The major portion of electricity demand is generated by synchronous generators (SGs), which have inherent rotational inertia and damping properties. Motivated by conventional SG dynamics, the concept of providing synthetic inertia using virtual synchronous generators (VSGs) VSGs was introduced in 2007 [11] This method emulates the inertial response of real SGs by the grid-connected voltage source converters (VSCs) through a control technique, resulting in fast frequency support during contingencies. Employing energy storage systems (ESS) ESSs such as supercapacitors and battery banks on the DC-side of VSCs and proportional linking their active power references with the frequency oscillations is another emerging method of enhancing inertial response in power systems [17,18] These approaches can provide sufficient inertia and damping properties for fast restoring power balance in the grid. IIggnnoorriinngg ppoowweerr lloosssseess iinn tthhee ccoonnvveerrtteerr,, tthhee oouuttppuutt ccuurrrreenntt ooff tthhee VVSSCC ccaann bbee ttrraannssllaatteedd iinnttoo tthhee DDCC--lliinnkk ccaappaacciittoorr vvoollttaaggee ((uuddcc))bbyy:: G1G(1s()s=) =.

DDyynnaammiicc AAnalysis of the Phase-Locked Loop

Findings

Dynamics Assessment of the Proposed Control Technique