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

BALANCED LOAD FREQUENCY CONTROL: CUSTOMIZED WORLD CUP ALGORITHM - DRIVEN PID OPTIMIZATION FOR TWO AREA POWER SYSTEMS

Finding a balance between the loads and generating demands in power systems is a significant challenge since power producers require important inputs such as security, reliability and quality. In this study, a unique method for balanced load frequency control (BLFC) is proposed in two-area power systems, integrating a customized World Cup Algorithm (CWCA)-Driven PID optimization. The primary objective is to enhance the stability and performance of power systems. For this purpose, the integral time-multiplied absolute error (ITAE) is minimized by evaluating the objective function using time-domain simulation. The proposed methodology aims to improve the overall response of the control system, ensuring a reliable and stable power supply. Within the scope of two-area power systems with BLFC, simulation results show the effectiveness and resilience of the CWCA-Driven PID Optimization. The outcomes of the proposed PID controller-based CWCA approach are contrasted with the existing methods

Load frequency control of power system based on improved AFSA-PSO event-triggering scheme

Aiming at the impact of redundant information transmission on network resource utilization in current power systems, an improved event-triggered scheme based on particle swarm optimization and artificial fish swarm algorithm for power system load frequency control (LFC) with renewable energy is proposed. First of all, to keep the stability and security of power systems with renewable energy, the load frequency control scheme is investigated in this paper. Then, to relieve the communication burden and increase network utilization, an improved event-triggered scheme based on the particle swarm algorithm and artificial fish swarm algorithm is explored for the power system load frequency control. Then, by utilizing improved Lyapunov functional and the linear matrix inequality method, sufficient condition for the H∞ stability of the load frequency control system is established. Finally, a two-area load frequency control system and IEEE-39 node simulation models are constructed to verify the effectiveness and applicability of the proposed method

A Review of Current Research Trends in Power-Electronic Innovations in Cyber-Physical Systems.

In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.post-print2.019 K

Stability analysis of load frequency control for power systems with interval time-varying delays

This study investigates the stability problem of load frequency control (LFC) for power systems with interval time-varying delays. The two categories of time delays, the lower bound being zero and non-zero, are considered. The systems can be described as time delay systems of load disturbances. First, an augmented Lyapunov–Krasovskii functional (LKF) is constructed. Some delay-dependent nonintegral terms and single integral terms are additionally introduced to make full use of the information on the system state variables and the time-varying delays. Second, to overcome the problem of nonlinear inequalities caused by the augmented LKF, the nonlinear inequalities are converted into linear matrix inequalities (LMIs) by applying the new negative definite inequality equivalence transformation lemma, which can be solved easily by the MATLAB LMI toolbox. A new stability criterion is presented by applying the Lyapunov stability theory. The stability criterion is less conservative than some existing literature studies, which further improves the stability margin for the power systems based on LFC. Finally, some numerical examples are given to show the effectiveness of the proposed method and the superiority of the results

Electric System Vulnerabilities: a State of the Art of Defense Technologies

Vulnerability of the European electrical infrastructure appears to be growing due to several factors: - demand is always growing, and, although this growth may be forecast, it cannot be anytime easily faced; - transactions increase, following electrical system liberalisation, and this involves operating the whole infrastructure closer to the system capacity and security limits; - an increased control systems complexity, required for secure system operation, may in turn raise system vulnerability, due both to accidental faults and malicious attacks; - critical infrastructures, and the electrical system primarily, are well known to be a privileged target in warfare, as well as terrorist attacks. In recent years, both Europe and America have experienced a significant number of huge blackouts, whose frequency and impact looks progressively growing. These events had common roots in the fact that current risk assessment methodologies and current system controls appear to be no longer adequate. Beyond the growing complexity of the electrical system as a whole, two main reasons can be listed: - system analysis procedures based on these methodologies did not identify security threats emerging from failures of critical physical components; - on-line controls were not able to avoid system collapse. This report provides a state-of-the-art of the technology on both regards: - as far as risk assessment methodologies are concerned, an overview of the conceptual power system reliability framework is provided, and the current N-1 principle for risk assessment in power systems is introduced, together with off-the-shelf enforcement methodologies, like optimal power flow. Emerging methodologies for dynamic security assessment are also discussed. The power system reliability approach is compared with the global approach to dependability introduced by computer scientists, and the conceptual clashes pointed out. Ways ahead to conciliate both views are outlined. - concerning power system controls, the report overviews the existing defense plans, making specific reference to the current Italian situation. The two major recent blackout events in the American North East and Italy are analysed, and the drawbacks of the existing arrangements and the installed control systems are discussed. Emerging technologies, such as phasor measurement units and wide area protection are introduced. Their likely impact on the existing control room is discussed. Finally, potential cyber vulnerabilities of the new control systems are introduced, the role of communication standards in that context is discussed, and an overview of the current state of the art is presented.JRC.G.6-Sensors, radar technologies and cybersecurit