A smart control strategy for the black start of a microgrid based on PV and other auxiliary sources under islanded condition

Abstract

Microgrids can provide clean, reliable and uninterruptible power. However, under certain situations like islanded condition or faults, it is needed to be shutdown for preventing any adverse impact on systems and loads. Certain situations such as critical (local) load management which needs uninterrupted service demand restoration of the microgrid from shutdown state in shortest time. This is referred to as the `black start'. The black start can be initiated both in the presence and absence of the grid. In case the grid is absent, `black start' becomes a difficult task due to the absence of a reference voltage for the local energy sources, which otherwise use a voltage reference derived from the main grid. This paper presents a smart control strategy for the identification of a suitable local source, which is made to operate in voltage control mode to generate a stable and clean voltage reference in the absence of the main grid voltage reference and facilitates grid synchronization to smoothly switchover from islanded operation to grid connected operation, when the main grid comes back. As per the proposed control scheme, a Microgrid Master Controller (MMC), interfaced with Local Source Controller (LSC) through a Slave Controller (SC), collects information such as solar radiation, temperature, wind speed, availability of a local source etc. MMC reviews the collected information and decides on the most optimal and robust master generator which can serve as a stable voltage reference for the rest of the sources on the microgrid. If the MMC can not determine a stable voltage reference source, the battery powered inverter with PLL operation is brought in to provide the high quality stable reference. All the details of this work are included.