Controle de uma microrrede ilhada baseada em geração eólica-diesel com alto nível de inserção de geração eólica

Abstract

The insertion of distributed generation units in the electric power systems have contributed to the popularization of microgrid concepts. With the microgrids, several potential benefits can be achieved in regard to power quality and supply reliability. However, several technical challenges related to the control and operation of microgrids, which are associated with high insertion of generation systems based on static converters, must be overcame. Among the opportunities in the context of microgrids, there is the islanded operation of microgrids temporarily disconnected from the electric power systems and also the autonomous operation of geographically isolated microgrids. The frequency in large power systems is traditionally controlled by the generation units based on traditional synchronous generator. The insertion of distributed generation units based on static power converters may bring difficulties to the frequency control in microgrids, due to the reduction of the equivalent inertia of conventional synchronous generators present in islanded and isolated microgrids. In this context, it becomes necessary the proposition of new operational and control strategies for microgrids control, taking into account the presence of distributed generation units based on full-rated converter. This paper proposes an operational and control strategy for the islanded operation of a winddiesel microgrid with high insertion level of wind generation. The microgrid adopted in this study comprises of a wind energy conversion system with synchronous generator based on full rated converter, a diesel generator (DIG) and a dump load. Due to the high insertion level of wind generation, the wind unit operates in Vf mode and the diesel generator operates in PQ mode. The diesel generator and the dump load are used to regulate the DC-link voltage of the wind generation unit. The proposed control allows the islanded operation of the microgrid only with wind generation, wind-only mode (WO), and with wind-diesel generation, wind-diesel mode (WD). For the wind-only mode, with 100% of penetration level of wind generation, it is proposed a DC-link voltage control loop based on the use of a DC dump load. For the winddiesel mode, it is proposed a DC-link voltage control loop added to the diesel generator, which is connected to the AC side of the microgrid, in coordinated action with the dump load. The proposed operational and control strategy does not require the use of batteries and aims to maximize the energy production from wind generation, ensuring the uninterrupted operation of the microgrid. The results have showed that the operational and control strategy allowed the stable operation of the islanded microgrid and that the DC-link voltage control loop added to the diesel generator and the dump load proved to be effective during the typical variations of wind speed and load.