A Decentralized Scalable Approach to Voltage Control of DC Islanded Microgrids

Abstract

We propose a new decentralized control scheme for DC Islanded microGrids (ImGs) composed by several Distributed Generation Units (DGUs) with a general interconnection topology. Each local controller regulates to a reference value the voltage of the Point of Common Coupling (PCC) of the corresponding DGU. Notably, off-line control design is conducted in a Plug-and-Play (PnP) fashion meaning that (i) the possibility of adding/removing a DGU without spoiling stability of the overall ImG is checked through an optimization problem; (ii) when a DGU is plugged in or out at most neighbouring DGUs have to update their controllers and (iii) the synthesis of a local controller uses only information on the corresponding DGU and lines connected to it. This guarantee total scalability of control synthesis as the ImG size grows or DGU gets replaced. Yes, under mild approximations of line dynamics, we formally guarantee stability of the overall closed-loop ImG. The performance of the proposed controllers is analyzed simulating different scenarios in PSCAD.

Plug-and-Play Robust Voltage Control of DC Microgrids

“…To evaluate the performance of the proposed control scheme, we consider an islanded DC microgrid consisting of 6 DGs with buck converters, taken from [27], as graphically shown in Fig. 4.…”

“…The optimization problems in (27) and (30) can be solved using some developed control approaches in the literature, e.g. [32], [33].…”

“…The performance of the proposed voltage control approach in terms of PnP operation of DGs is compared with the one in [27]. To this end, it is assumed that DG5 is plugged out at t = 4 s and it is then plugged into the microgrid at t = 6 s. The results obtained via the control strategy in [27] and proposed control approach are depicted in Fig.…”

“…Non-droop-based control approaches have mostly been used for primary voltage control of AC microgrids [20]- [26]. An example of this control strategy used for DC microrgrids is decentralized scalable state feedback control proposed in [27].…”

“…The main problem is that PnP functionality of DGs does affect the microgrid stability and deteriorates closedloop system performance. Although the proposed approach in [27] provides many advantages such as scalability and decentralized structure of primary voltage controllers, it does not allow robust plug-and-play operation. Once a DG is plugged into microgrids or plugged out from the system, the neighbors of that DG have to retune their local primary voltage controllers.…”