Decentralised and interlink-less power interchange among residences in microgrids using virtual synchronous generator control

Abstract When numerous inertia-less distributed power supplies (DPSs) are connected to a microgrid (MG), the inertial force of the entire system may be insufficient. The lack of inertial force will cause the system frequency and voltage to be transiently unstable; thus, parallel operation of multiple inverters may be difficult. As a means of solving these problems, the use of virtual synchronous generator (VSG) control, in which the inverter has a virtual inertial force and simulates the inertial behaviour of a synchronous generator (SG), is attracting interest. In residential applications, photovoltaics (PVs) and fuel cells (FCs) are examples of home DPSs that are connected to grids via inertia-less inverters. The virtual inertial force in a VSG is produced by a storage battery (BAT). Therefore, when using a VSG-controlled BAT as the main power supply in the islanded MG of a residential building, FCs can be employed as stable charging power sources for BATs instead of PVs, which are weather- and time-dependent. In addition, FCs and BATs are complementary in the sense that BATs transiently compensate for the slow responsiveness of FCs. In this paper, an autonomous power management (APM) approach, in which electric power is interchanged within an islanded MG, is proposed, where an MG consists of a set of nanogrids (NGs), meaning residential units. The power sources in the NG are FCs and BATs connected via conventional current- and VSG-controlled inverters, respectively. Both the VSG and conventional current controls are primary controls, while APM acts as a secondary control. As a VSG provides an autonomous governor-free function, interlinks between the NGs and centralised control in a higher layer are not required, and all of the abovementioned controls are installed in each NG. The advantages of communication-less, decentralised autonomous power interchange among NGs are easy operation and improved flexibility and scalability of stable MGs.