Real-Time Economic Frequency Regulation for Partitioned Microgrids Based
on Cost-Driven Droop Function
Abstract
With the increase of the number and geographic dispersion of distributed
energy resources (DERs), the microgrid (MG) has become scattered along
with the higher complexity of control and communication. This paper
proposes a two-level regulation strategy to achieve the local objective
of frequency regulation and power sharing as well as the global
objective of economic operation in the real time for the scattered MG.
Firstly, the MG integrated with multiple DERs is partitioned into
several nanogrids (NGs) such that DERs connecting on the same
feeder are grouped in the same NG for the efficient and cost-effective
communication and control. Then in the NG level, the total power
mismatch of the entire MG can be learned and an optimal incremental cost
can be agreed by each NG through the fastest distributed linear
averaging (FDLA) and discrete-consensus algorithm, respectively. In the
DER level, a cost-driven droop gain is developed to indicate the
willingness of each DER in the NG to participate into the frequency
regulation service. The pinning-based protocol is formulated to regulate
the frequency and meanwhile enable the proportional power sharing among
DERs based on the economic droop function. Case studies satisfactorily
demonstrate the effectiveness of the proposed regulation strategy for
the economic frequency regulation in the tested MG.