Design criteria for a power management system for Microgrids with renewable sources

The paper describes the control functions that a power management system (PMS) needs for controlling a microgrid, with both conventional and renewable sources. According to the IEEE 1547.4, distributed resources island systems – or in brief “microgrids” – are active networks containing both loads and distributed generators, and may require a modification of their control logic if they are connected to a grid or not. A fast load or generator shedding actions may also be required to preserve system stability incase the microgrid switches from connected to islanded. Today, most industrial networks are designed to run also in islanded mode, while in public networks transmission system operators (TSO) generally do not allow islands. The presence of renewable sources that are partially not controllable requires there-definition of the control logic compared with microgrids where only fully controllable generators are present. PMS of a microgrid has a double function:- to guarantee the stable operation of the system in presence of the unpredictable variations caused by renewable sources and loads,- to optimize the energy production of renewable and conventional sources. The logic described in the paper was implemented in a PMS that was tested with a software simulator prior to the installation in a real microgrid. The paper reports the results of tests.