Secondary Control Strategies for Frequency Restoration in Islanded Microgrids with Consideration of Communication Delays

One of the well-known methods to share active and reactive power in microgrids (MGs) is droop control. A disadvantage of this method is that in steady state the frequency of the MG deviates from the nominal value and has to be restored using a secondary control system (SCS). The signal obtained at the output of the SCS is transmitted using a communication channel to the generation sources in the MG, correcting the frequency. However, communication channels are prone to time delays, which should be considered in the design of the SCS; otherwise, the operation of the MG could be compromised. In this paper, two new SCSs control schemes are discussed to deal with this issue: 1) a model predictive controller (MPC); and 2) a Smith predictor-based controller. The performance of both control methodologies are compared with that obtained using a conventional proportional integral-based SCS using simulation work. Stability analysis based on small signal models and participation factors is also realized. It is concluded that in terms of robustness, the MPC has better performance.FONDECYT 1140775 Advanced Center for Electrical and Electronic Engineering Basal Project FB0008 Fondequip EQM13005

Distributed secondary voltage regulation for autonomous microgrid

© 2017 IEEE. This research addresses the control problem of microgrids and presents a robust distributed secondary control system for voltage regulation of an islanded microgrid with droop-controlled and inverter-based distributed generators (DGs). A consensus-based distributed control approach is proposed to restore the voltage and frequency of the islanded microgrid to the reference values for all DGs within a very short time. The proposed method is flexible to system topology variations which AIDS the plug-and-play operation of microgrid. An autonomous micogrid test system consisting of four DGs is constructed in MATLAB using SimPowerSystem Toolbox to test the proposed design method, and the simulation results show the effectiveness of the proposed control strategy. The performance of the proposed controller is shown through several test case studies

An enhanced secondary control approach for voltage restoration in the DC distribution system

The paper will deal with the problem of establishing a desirable power sharing in multi-feed electric power system for future more-electric aircraft (MEA) platforms. The MEA is one of the major trends in modern aerospace engineering aiming for reduction of the overall aircraft weight, operation cost and environmental impact. Electrical systems are employed to replace existing hydraulic, pneumatic and mechanical loads. Hence the onboard installed electrical power increases significantly and this results in challenges in the design of electrical power systems (EPS). One of the key paradigms for future MEA EPS architectures assumes high-voltage dc distribution with multiple sources, possibly of different physical nature, feeding the same bus(es). In our study we investigate control approaches to guarantee that the total electric load is shared between the sources in a desirable manner. A novel communication channel based secondary control method is proposed in this paper. Stability of the proposed method is investigated and it proves that the system stability margin is upgraded using the compensation method. The analytical results of the study will be supported by both time-domain simulations and experimental results

Local frequency restoration for droop-controlled parallel inverters in islanded microgrids

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksIn islanded microgrids, voltage source inverters working in parallel are expected to provide regulation of the local frequency while granting active power sharing. This paper presents a local control approach at each inverter based on an event-driven operation of a parameter-varying filter. It ensures perfect active power sharing and controllable accuracy for frequency restoration without requiring the exchange of control data between inverters over the communication network. The paper includes stability analysis and design guidelines for the control parameters using a modeling approach that considers the interaction between inverters. Selected experimental results on a three-inverter laboratory microgrid corroborate the effectiveness of the proposed control scheme, and outlines its advantages with respect to previous similar schemes and the performance cost that implies not using communicationsPeer ReviewedPostprint (author's final draft