Control Strategy Applied For Distributed Generatior Systems Through Virtual Synchronous Machine Concept.
Distributed generation, Power Flow Control, Virtual Synchronous Genetator, Virtual Inertia, smooth start up.
The increasing of Distributed Generation (DG) based on renewable energy sources (RES) has contributed to the reduction of several environmental, economic and social impacts caused by the burning of fossil fuels in the conventional generation system. However, the massive increase in the energy production based on FERs, also causes undesirable impacts, such as the decrease of the grid inertia, voltage oscillations and stability margins reduction. In addition, the Electrical Power System (EPS) has changed its configuration and the microgrid concept has gained interest in recent years. In this approach, more efficient and reliable control systems are required for proper EPS operation. Thereby, DG control strategies have been developed aiming, not only to provide the power from primary sources, but also provide voltage and frequency support to the power grid, increasing the stability margins and guaranteeing the energy quality. Thus, this work proposes a control system based on Virtual Synchronous Generator (VSG) approach, aiming to contribute to the stability of the electrical network, providing voltage support by regulating the power flow, using the P/ω and Q/V droop control technique. Frequency support is obtained by introducing a virtual inertia in the DG. The virtual inertia is emulated by means of transport delay techniques applied in the power loop. Unlike most works that use the VSG approach, a smooth start up scheme is developed, using the voltage vector estimation of the electrical grid, made by an SRF-PLL (Synchronous Reference Frame Phase Locked Loop). Simulation results are presented to validate the proposed method.