Synthesizing Virtual Oscillators to Control Islanded Inverters

Brian Johnson, Mohit Sinha, Florian Dorfler, Sairaj Dhople, Nathan Ainsworth

Research output: Contribution to journalArticle

202 Scopus Citations


Virtual oscillator control (VOC) is a decentralized control strategy for islanded microgrids where inverters are regulated to emulate the dynamics of weakly nonlinear oscillators. Compared to droop control, which is only well defined in sinusoidal steady state, VOC is a time-domain controller that enables interconnected inverters to stabilize arbitrary initial conditions to a synchronized sinusoidal limit cycle. However, the nonlinear oscillators that are elemental to VOC cannot be designed with conventional linear-control design methods. We address this challenge by applying averaging- and perturbation-based nonlinear analysis methods to extract the sinusoidal steady-state and harmonic behavior of such oscillators. The averaged models reveal conclusive links between real- and reactive-power outputs and the terminal-voltage dynamics. Similarly, the perturbation methods aid in quantifying higher order harmonics. The resultant models are then leveraged to formulate a design procedure for VOC such that the inverter satisfies standard ac performance specifications related to voltage regulation, frequency regulation, dynamic response, and harmonic content. Experimental results for a single-phase 750 VA, 120 V laboratory prototype demonstrate the validity of the design approach. They also demonstrate that droop laws are, in fact, embedded within the equilibria of the nonlinear-oscillator dynamics. This establishes the backward compatibility of VOC in that, while acting on time-domain waveforms, it subsumes droop control in sinusoidal steady state.
Original languageAmerican English
Pages (from-to)6002-6015
Number of pages14
JournalIEEE Transactions on Power Electronics
Issue number8
StatePublished - 2016

NREL Publication Number

  • NREL/JA-5D00-64761


  • averaging
  • droop control
  • microgrids
  • nonlinear oscillator circuits
  • synchronization
  • Van der Pol oscillators


Dive into the research topics of 'Synthesizing Virtual Oscillators to Control Islanded Inverters'. Together they form a unique fingerprint.

Cite this