Abstract
Virtual Oscillator Control (VOC) is a promising technique that allows several inverters connected to a microgrid to naturally synchronize, without communication. However, the selection of the VOC parameters often require iterative or optimization procedures that render its practical use not straightforward. In this paper, this problem is overcome with the proposition of a novel methodology for determining the dead-zone type VOC parameters based on the describing function method. The methodology consists of a set of analytical equations that use as input data few basic electrical system parameters from the converter and from the microgrid, namely, the operating voltage and frequency ranges, besides rated power. The proposed set of equations is used to calculate the parameters required to control an inverter in voltage mode. The validity of the proposed approach is demonstrated in experiments that encompass different situations such as pre-synchronization, connection, and disconnection of a second inverter from a microgrid.
Highlights
It will be shown that less harmonic distortion, especially third harmonic, can be obtained by following the tuning methodology presented here, which relies on the use of a piecewiselinear nonlinear function, in comparison to the approach relying on a cubic nonlinear function
A new method is proposed for determining the design parameters required for virtual oscillator control
In the the proposed method, all VCO parameters are directly computed with simple expressions that use as input data information that is readily available from the inverter and from the microgrid
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In Wu et al [15], it is shown the effects of PLLs on the converter stability, how the interaction of PLLs with the grid/regulators can lead to instability These drawbacks have motivated the development of a new approach, the Virtual Oscillator Control (VOC), initially proposed in Torres et al [16,17], with mathematical proofs for guaranteeing global asymptotic stability of the synchronization condition for symmetric electrical networks. The proposed strategy consists of a set of analytical equations that use as input data only basic electrical parameters from the converter and from the microgrid, namely, the rated power and voltage and frequency ranges It has the advantage over existing procedures to avoid the use of optimization, numerical solutions or graphical analyzes, and significantly simplifies the VOC tuning process. The ideas presented in Johnson et al [30] and Rosse et al [31], concerning three-phase implementations, are compatible with the method presented here
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