A Virtual Synchronous Machine to Support Dynamic Frequency Control in a Mini-Grid That Operates in Frequency Droop Mode

Miguel Torres, Luiz A. C. Lopes

Department of Electrical and Computer Engineering, Concordia University, Montreal, Canada.

DOI: 10.4236/epe.2013.53025                

Abstract

This paper addresses the problem of dynamic frequency control in a diesel-based mini-grid. It is shown that a virtual synchronous machine (VSM) can support dynamic frequency control by adding virtual inertia and damping to the system. However, it is found that the typical formulation of damping power does not work properly when the grid forming gen-set operates in droop mode because of the unknown stabilization value of the grid frequency. As a solution to this problem, an estimator for the stabilization frequency that works in conjunction with the damping function of the VSM is proposed. Theoretical and experimental results provide evidence of a satisfactory performance of the proposed VSM with estimator for different values of the gen-set droop factor. The estimated stabilization frequency converges in approximately 2 s and the maximum frequency deviation during the transient is reduced in 34%, on average.

Keywords

Frequency Control; Mini-Grid; Inverter; Virtual Synchronous Machine

Conflicts of Interest

The authors declare no conflicts of interest.

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