Synthesizing Virtual Oscillators to Control Islanded Inverters

Johnson, Brian; Sinha, Mohit; Ainsworth, Nathan; Dörfler, Florian; Dhople, Sairaj V.

doi:10.1109/tpel.2015.2497217

Cited by 209 publications

(178 citation statements)

References 26 publications

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“…Most of the common approaches of grid-forming control focus on droop control [1]- [3]. Other popular approaches are based on mimicking the physical characteristics and controls of synchronous machines [4]- [6] or controlling inverters to behave like virtual Liénard-type oscillators [7]- [10]. While strategies based on machine-emulation are compatible with the legacy power system, they use a system (the inverter) with fast actuation but almost no inherent energy storage to mimic a system (the generator) with slow actuation but significant energy storage (in the rotating mass) and may also be ineffective due to deteriorating effects of time-delays in the control loops and current This work was partially funded by the European Union's Horizon 2020 research and innovation programme under grant agreement N • 691800.…”

Section: Introductionmentioning

confidence: 99%

“…Virtual oscillator control (VOC) is a promising approach because it can globally synchronize an inverter-based power system. However, the nominal power injection cannot be specified in the original VOC approach [7]- [10], i.e., it cannot be dispatched. Likewise, all theoretic investigations are limited to synchronization with identical angles and voltage magnitudes.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Transmission-Line Dynamics on Grid-Forming Dispatchable Virtual Oscillator Control

Groß

Colombino

Brouillon

et al. 2019

IEEE Trans. Control Netw. Syst.

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In this work, we analyze the effect of transmission line dynamics on grid-forming control for inverter-based AC power systems. In particular, we investigate a dispatchable virtual oscillator control (dVOC) strategy that was recently proposed in the literature. When the dynamics of the transmission lines are neglected, i.e., if an algebraic model of the transmission network is used, dVOC ensures almost global asymptotic stability of a network of AC power inverters with respect to a pre-specified solution of the AC power-flow equations. While this approximation is typically justified for conventional power systems, the electromagnetic transients of the transmission lines can compromise the stability of an inverter-based power system. In this work, we establish explicit bounds on the controller setpoints, branch powers, and control gains that guarantee almost global asymptotic stability of dVOC in combination with a dynamic model of the transmission network.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Effect of Transmission-Line Dynamics on Grid-Forming Dispatchable Virtual Oscillator Control

Groß

Colombino

Brouillon

et al. 2019

IEEE Trans. Control Netw. Syst.

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“…In the present paper, we focus on frequency synchronization, whichas in any alternating current (AC) power systemis a prime control objective in MGs [5,8]. As such it has received signicant attention in recent years and there are a large variety of possible control schemes to address this objective, such as droop control [11,10], virtual synchronous machines [1214], virtual oscillator control [15] and frequency control schemes implemented Preprint submitted to Automatica in a synchronous dq reference frame [1619].…”

Section: Motivation and Existing Literaturementioning

confidence: 99%

“…Then, also all equilibria are isolated. Furthermore, if and only if (15) is satised with strict inequality, then the equilibria are given by col(η…”

Section: A Necessary and Sucient Condition For Existence Of Equilibriamentioning

confidence: 99%

Global synchronization analysis of droop-controlled microgrids—A multivariable cell structure approach

Schiffer

Efimov

2019

Automatica

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The microgrid concept represents a promising approach to facilitate the large-scale integration of renewable energy sources. Motivated by this, the problem of global synchronization in droop-controlled microgrids with radial topology is considered. To this end, at rst a necessary and sucient condition for existence of equilibria is established in terms of the droop gains and the network parameters. Then, the local stability properties of the equilibria are characterized. Subsequently, sucient conditions for almost global synchronization are derived by means of the multivariable cell structure approach recently proposed in [1]. The latter is an extension of the powerful cell structure principle developed by Leonov and Noldus to nonlinear systems that are periodic with respect to several state variables and possess multiple invariant solutions. The analysis is illustrated via numerical examples.

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“…The above-exposed adverse impacts of the PLL greatly motivate the advancement and development of non-PLL-based synchronization schemes and associated VSC controls. Among these, the Virtual Synchronous Generator (VSG) control (Zhong and Weiss, 2011;D'Arco et al, 2015) and the Virtual Oscillator Control (VOC) (Johnson et al, 2014(Johnson et al, , 2016Sinha et al, 2017) are very popular. Specifically, the VSG controls eliminate the use of PLL by mimicking the behavior of a Synchronous Generator (SG), whereas the VOC achieves non-PLL synchronization by utilizing the intrinsic features of particular types of non-linear oscillators, e.g., Van der Pol oscillator.…”

Section: Introductionmentioning

confidence: 99%

Synchronizing Stability Analysis and Region of Attraction Estimation of Grid-Feeding VSCs Using Sum-of-Squares Programming

Zhang

Molinas

et al. 2020

Front. Energy Res.

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Grid-synchronizing Stability (GSS) is an emerging issue related to grid-feeding voltage-source converters (VSCs). Its occurrence is primarily related to the non-linear dynamics of a type of vastly applied synchronization unit-Phase-locked Loops (PLL). Dynamic characterization and modeling for the GSS analysis can be achieved using a simplified system model, which is a second-order and autonomous non-linear equation, but with the presence of an indefinite damping term. As revealed and demonstrated in this work, this indefinite damping effect can result in an inaccurate Region-of-Attraction (ROA) estimation of the traditional Equal Area Principle (EAP)-based method. To overcome this issue and achieve a valid ROA estimation, this paper adopts the sum-of-squares (SOS) programming technique, which is a numeric optimization method with SOS relaxations. The development and implementation of the SOS program for ROA estimation are presented. Numerical case studies and time-domain verifications demonstrate that this method is valid for GSS analysis, and an almost precise estimation is achieved in the first quadrant. This evidence makes the SOS method a promising tool for GSS analysis because the GSS problem is most concerned with the stability within the first swing cycle, i.e., in the first quadrant.

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Synthesizing Virtual Oscillators to Control Islanded Inverters

Cited by 209 publications

References 26 publications

The Effect of Transmission-Line Dynamics on Grid-Forming Dispatchable Virtual Oscillator Control

The Effect of Transmission-Line Dynamics on Grid-Forming Dispatchable Virtual Oscillator Control

Global synchronization analysis of droop-controlled microgrids—A multivariable cell structure approach

Synchronizing Stability Analysis and Region of Attraction Estimation of Grid-Feeding VSCs Using Sum-of-Squares Programming

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