Distributed Secondary Control in Microgrids Using Synchronous Condenser for Voltage and Frequency Support

Abstract

A high share of distributed energy resources (DERs) in power distribution grids has posed many challenges for system operation and control. Microgrid (MG) application with different distributed control approaches for DERs has been drawn a lot of attention from the research community to provide more flexibility, reliability and resilience for the system. This paper develops a distributed secondary control for DERs in MGs and on top of that using synchronous condenser (SC) participating in the secondary control for voltage support. The proposed distributed secondary control framework of MGs is designed to obtain four objectives as follows: (i) frequency restoration, (ii) average voltage restoration, (iii) arbitrary active power sharing among SGs and BESSs and (iv) arbitrary reactive power sharing among all SGs, BESSs and SCs. The comparison results under different scenarios show that with SC participating in the distributed secondary control in MGs, the system frequency and voltage response are much improved and quickly recovered to the nominal values thanks to the natural inertia response and fast reactive power control of SC sharing with other DERs in the MGs. Additionally, a multi-agent system is implemented to realize the proposed control method in hardware environment.

Modelling the Steady-State of Secondary Control in Islanded AC Microgrids

“…For the secondary control of islanded MGs, several approaches have been presented in the literature, mainly divided in the following groups [14]: a) decentralized [15]- [17], b) centralized [14] [18], c) distributed averaging [19] [20], d) consensus [21]- [25].…”

“…Al [24]. Although other linear equations have been presented in the literature e.g [21] [23] [25], they are variations of these two basic models. Below, the consensus frequency and voltage controllers of Bidram [22] and Simpson [24] are presented, in two different sub-sections.…”

“…Finally, ( 25) is derived from (24), in a similar sense as (21), where 𝒅𝑽 and 𝒅𝑸 𝑮 are the required variation of positivesequence voltage and reactive power of DGs so that both (24) and the power flow equations are fulfilled.…”

A Generalized Method for Modelling the Steady-State of Secondary Control in Islanded AC Microgrids

“…It is a type of one-to-neighbor communication (wired or wireless), where each local controller receives (sends) the voltage and frequency from (to) the controllers of the neighboring DGs. Then, considering their own and neighboring signals, the local controller of each DG applies consensus algorithms to restore the voltage and frequency [21]- [25]. The communication and computation requirements of consensus algorithms are lower compared to the centralized and distributed averaging schemes.…”

“…The consensus equations can be linear [21]- [25] or nonlinear [29]. Nevertheless, in this paper, only the linear consensus is considered, while the non-linear is left for future research.…”