Técnicas de controle para inversores baseadas em osciladores virtuais: aplicação aos sistemas de geração distribuídos

Abstract

The Virtual Oscillator Control (VOC) is a promising technique that allows several inverters connected to a microgrid to naturally synchronize, without communication. In this work, a novel methodology is proposed for determining the parameters of the dead-zone type VOC 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 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. Furthermore, as shown in the results, the proposed method has potential advantages over other technique available in the literature. Following the design guide presented here, the dead-zone type VOC generates less third harmonic distortion and needs less time to synchronize when connected to a network. The study of VOC has inspired the creation of a new control framework, the current Virtual Oscillator Control (cVOC). The cVOC was initially thought as a version of VOC for current mode control. The network voltage is used to generate the converter current loop reference, this strategy allows the control of delivered apparent power and the power factor angle (active and reactive power), according to the desired references. The design technique associated with this new methodology is described in this work too. Like the VOC version, the procedure consists of a set of analytical equations that use as input data only the basic electrical parameters of the converter and the microgrid, the nominal power and frequency and the voltage operating range. In order to validate this new control approach, simulation and bench test results are presented. From the results presented, it is concluded that the technique has potential for the control of converters connected to the distribution network.