Adaptive Marginal Costs-Based Distributed Economic Control of Microgrid Clusters Considering Line Loss

Xiaoqian Zhou,Qian Ai,Hao Wang

doi:10.3390/en10122071

Abstract

When several microgrids (MG) are interconnected into microgrid clusters (MGC), they have great potential to improve their reliability. Traditional droop control tends to make the total operating costs higher as the power is distributed by capacity ratios of distributed energy resources (DERs). This paper proposes an adaptive distributed economic control for islanded microgrids which considers line loss, specifically, an interesting marginal costs-based economic droop control is proposed, and consensus-based adaptive controller is applied, to deal with power limits and capacity constraints for storage. The whole expense can be effectively lowered by achieving identical marginal costs for DERs in MGC. Specially, the capacity constraints only for storages are also included to do further optimization. Moreover, consensus-based distributed secondary controllers are used to rapidly restore system frequency and voltage magnitudes. The above controllers only need to interact with neighbor DERs by a sparse communication network, eliminating the necessity of a central controller and enhancing the stability. A MGC, incorporating three microgrids, is used to verify the effectiveness of the proposed methods.

Highlights

Microgrids can be considered autonomous small-type power distribution systems, which are integrated with several types of distributed energy resources (DERs) and loads [1]
Due to the differences in infrastructure and natural conditions, each microgrid contains distinct DERs and loads; it is beneficial to enhance the reliability and lower the expense if several microgrids are interconnected into microgrid clusters (MGC) for operation [4]
For AC microgrid clusters, considering economy requirements, this paper makes a contribution in the following areas; (i) an adaptive economic droop control framework, considering line loss among sub-microgrids is proposed; (ii) Apart from traditional power constraints of DERs, the capacity limits of storage units are considered, i.e., if the storage has increased to 80% or decreased to 20% of its capacity, its adaptive controller is applied to draw the power of the storage to zero. (iii) to effectively restore the system frequency, a distributed secondary frequency controller (DSFC) is proposed to complete this goal in a distributed way and (iv) the whole design effectively lowers the operating costs of MGC

Summary

Introduction

Microgrids can be considered autonomous small-type power distribution systems, which are integrated with several types of distributed energy resources (DERs) and loads [1]. In [3], for microgrids including the increased penetration of renewable energy sources, storage batteries, DERs and loads, a robust energy management solution to facilitate the optimum and economic control of energy flows throughout a microgrid network, was proposed. The research on MGC is still at the initial stage—in [5], a hierarchical control structure including primary, secondary, and tertiary levels was proposed, to handle power sharing among a cluster of DC microgrids. A consensus-based, distributed control strategies for voltage regulation and power flow control of DC microgrid clusters was presented in [6] and an SOC-based adaptive droop method was introduced at the primary level to equalize SOC of batteries inside each microgrid (MG). A real-time tertiary control algorithm for DC microgrids was developed

Methods

Results

Conclusion