Decentralized Frequency Control of Battery Energy Storage Systems Distributed in Isolated Microgrid

Abstract

The penetration and integration of renewable energy sources into modern power systems has been increasing over recent years. This can lead to frequency excursion and low inertia due to renewable energy sources’ intermittency and absence of rotational synchronous machines. Battery energy storage systems can play a crucial role in providing the frequency compensation because of their high ramp rate and fast response. In this paper, a decentralized frequency control system composed of three parts is proposed. The first part provides adaptive frequency droop control with its droop coefficient a function of the real-time state of charge of battery. The second part provides a fully decentralized frequency restoration. In the third part, a virtual inertia emulation improves the microgrid resilience. The presented results demonstrate that the proposed control system improves the microgrid resilience and mitigates the frequency deviation when compared with conventional ω -P droop control and existing control systems. The proposed control system is verified on Real-Time Digital Simulator (RTDS), with accurate microgrid model, nonlinear battery models and detailed switching models of power electronic converters.

State of Charge Control Integrated with Load Frequency Control for BESS in Islanded Microgrid

“…Moreover, it regulates the battery charge-discharge, charging rate, etc. PCS itself is designed to allow the BESS having many functions in power system application [14,[24][25][26].…”

“…Assume the load demand P L1 is applied, the BESS delivers P b1 ' while the generator delivers P d1 '. By substituting Equation (14) to Equation (11), the curve can be expressed as:…”

“…Several frequency stability issues related to islanded microgrid systems have been discussed. The reduction in inertia increases frequency oscillations of the system, as discussed in [7][8][9][10][11][12][13][14]. A frequency control strategy based on dynamically high-power machines to reduce the load is proposed in [9].…”

“…In addition, a decentralized control synthesis procedure for stabilizing the frequency that enables plug-and-play (PnP) operations is introduced in [11]. The frequency-reactive control is proposed in [12][13][14].…”

A Novel Structure of a Power System Stabilizer for Microgrids

“…These methods can contribute to improving the stability of microgrids in conjunction with protection relay. To overcome the low inertia of microgrids, the methods of utilizing virtual synchronous machines and an energy storage device are proposed in [36,37]. In addition, a study on the drop control technique of distributed power for frequency and voltage maintenance is carried out in [38], and Baneshi et al propose a method to ensure that load fluctuations are efficiently shared by distributed generations [39].…”