Implementação de máquina síncrona virtual do tipo Synchronverter para o gerador de indução duplamente alimentado conectado a uma microrrede

Abstract

The high integration of distributed generation based on renewable energy sources (DG-RE) into the conventional electric system brings many challenges to the operational sector, this is a consequence of the fact that renewable resources are intermittent, and consequently DG-FREs are non-dispatchable generation units. This makes it difficult to balance instantaneous demand and generation in the system. In addition, GD-FRE uses a VSC (voltage source converter) at the interface with the grid. The VSCs are fast responding power electronic devices with little or no inertia, thus changing the dynamic behavior of the power system; are controlled by the grid-following control technique, requiring the grid voltage reference, whose ability to support the grid is reduced. This thesis proposes frequency and voltage support of doubly fed induction generators (DFIG) using the virtual synchronous machine technique Synchronverter. In the proposed configuration, the rotor-side converter (RSC) is conventionally controlled and is responsible for maintaining the operation of the wind turbine at the maximum power point tracking (MPPT) and for controlling the stator reactive power, while the grid-side converter (GSC) is controlled by the Synchronverter. In order to achieve self-sufficiency, the Synchronverter has been enhanced to realize: normal operation, where the active power is set by controlling the DC bus voltage, similar to conventional GSC control; synthetic inertia and frequency support/active power and voltage/reactive power. The additional active power required for frequency support comes from a battery energy storage system (BESS) attached to the DC bus. The Synchronverter has also been enhanced to be able to control the charge-discharge of the BESS without using the DC-DC converter, achieving economy and simplicity. In addition, there is the natural advantage of the Synchronverter that it does not need a PLL (Phase-Locked Loop). Simulation tests are performed and the results suggest that the DFIG equipped with the proposed control strategy demonstrates superiority over conventional and previous techniques, being able to satisfactorily control the DC bus voltage, provide the ancillary services mentioned above, and control the loaddischarge of the BESS. In the tests, the DFIG is connected to a microgrid composed of 8 load bars and a hydroelectric power plant, then the following disturbances were triggered: sudden wind variations, symmetrical outage, and abrupt load variations.