Dynamic Performance Of Microgrid Research Articles

Optimal Communication Network Design of Microgrids Considering Cyber-Attacks and Time-Delays

Distributed secondary control stands out for its flexibility and expandability in microgrids (MGs) control, in where communication network plays a fundamental and critical role. The communication topology and link-weights have significant impact on the attack-resilience and dynamic performance of MGs, which should be appropriately designed. However, the joint optimization problem of communication topology and link-weights in the existing literature of consensus-based secondary voltage control of MGs is usually neglected. To bridge this gap, we propose a novel two-stage optimization approach for the communication network design, which jointly optimizes the topological structure to enhance the structural survivability and link weights to improve the dynamic performance (including the speed of convergence and robustness to time-delay). The first stage problem is formulated into a mixed-integer semi-define programming (MISDP) model based on convex relaxation technique, which is then converted equivalently into an integer quadratic programming (IQP) problem and then a MISDP feasibility problem to facilitate the solution. The second stage problem is formulated into a bi-objective SDP model to compromise between the convergence performance and robustness to time-delay. Simulations based on a microgrid with 10 distributed generation (DG) units under different scenarios are implemented to verify the effectiveness of the proposed method.

Optimal Model Predictive based on Super-Twisting Fractional Order Sliding Mode Control to Regulate DC-link Voltage of DC Microgrid

This paper aims to essentially regulate the DC-link voltage of DC microgrid during the disturbance conditions in power system. Hence, a novel Optimal Model Predictive Super-Twisting Fractional Order Sliding Mode Control (OMP-STFOSMC) is proposed for three-phase AC-DC converter which can effectively enhance the stability and dynamic performance of microgrid. The conventional model-predictive controllers have severely imposed the dynamic stability which leads to high overshoot, undershoot and settling-time. The sliding mode controller can be replaced instead of these conventional controllers to appropriately triumph over this problem. A main drawback of conventional sliding mode controller is related to its high frequency chattering in the control signal which can affect the system and doesn’t make it satisfactory and feasible for real applications. The proposed OMP-STFOSMC can effectively enhance the control tracking performance and reduce the high frequency chattering problem. The Stochastic Fractal Search (SFS) algorithm due to its high exploration and good evasion of local optima is used to optimally tune the controller parameters. Different operation conditions are considered to evaluate the dynamic and chattering-free performance of proposed controller. As to the simulation results with comparative analysis, it is observed that the proposed OMP-STFOSMC offers better dynamic stability characteristics.

Decentralized control strategy to improve dynamic performance of micro-grid and reduce regional interactions using BESS in the presence of renewable energy resources

Abstract Battery energy storage systems (BESSs) have been recently used in power network specially micro-grids (MGs). These devices increase the self-sufficiency and improve the frequency oscillations caused by the intermittent nature of distributed generations (DGs) or load uncertainty. In this paper, to improve the dynamic performance of MG, a multi-term feedback signal has been proposed. The first term is relating to a constant power which can be injected or absorbed by the battery to supply the load and overcome the lack of power due to the intermittency of renewable energy resources. The second term is based on frequency deviation which regulates the MG frequency dynamically and compensates the low inertia of inverter based resources. In addition, the power variation of tie-line has been also considered to reduce the interaction between two parts of the MG. 3-bus and 13-bus test power systems have been studied to show the effectiveness of the proposed methods in reducing the overshoot as well as damping time of frequency under several events. To evaluate the stability of the system, the eigenvalue analysis based on small signal model has been investigated and finally, the simulation results verified the effectiveness of the proposed controller to enhance the dynamic performance of the MG.

Economic and network feasible online power management for renewable energy integrated smart microgrid

Abstract In this paper, an online power management (OPM) problem is proposed using measured/short term forecasted data. It improves the cost and dynamic performance of microgrid along with the consideration of interval uncertainties in renewable energy and loads. Additional options of grid power trade and demand response (DR) are provided for operational cost reduction, consumer participation and enhanced network performance. A combination of stochastic weight tradeoff particle swarm optimization (SWT-PSO) and interval arithmetic (IA) is proposed to analyze the effects of interval uncertainties of nodal power injections (due to renewable energy sources (RES) and loads) on microgrid cost and power flow variables. The effectiveness of the proposed approach is investigated by adding different power balancing resources one by one, to the residential feeder of CIGRE LV benchmark microgrid. The results are found to be improved in terms of reduction in fuel and emission costs, improved nodal voltages and network feasible OPF solution in interval forms corresponding to system volatilities. Moreover, settling time of online dispatch is reduced, thereby improving the dynamic response of distributed energy resources (DERs). In addition, the paper justifies the use of RES, DR, grid power trade (over islanded mode) and SWT-PSO (over priority listing).

Influence of non-dispatchable energy sources on the dynamic performance of MicroGrids

This paper analyzes the influence of non-dispatchable energy sources on the dynamic stability of stand-alone MicroGrids (MGs) with autonomous control of frequency and voltage based on inverters. The analysis considers the use of eigenvalue techniques. Although this methodology is well known, the contribution of this paper is twofold. First, it proposes an algorithm for designing the inverter interface to meet the requirements associated with the harmonic distortion (THD) and dynamic performance of the inverter. Second, it provides an analysis of the dynamic stability of MG considering different levels of penetration of non-dispatchable energy sources, variations in the network parameters and the presence of dynamic loads (i.e., induction motors).

Hierarchical Structure of Microgrids Control System

Advanced control strategies are vital components for realization of microgrids. This paper reviews the status of hierarchical control strategies applied to microgrids and discusses the future trends. This hierarchical control structure consists of primary, secondary, and tertiary levels, and is a versatile tool in managing stationary and dynamic performance of microgrids while incorporating economical aspects. Various control approaches are compared and their respective advantages are highlighted. In addition, the coordination among different control hierarchies is discussed.

Microgrid Stability Characterization Subsequent to Fault-Triggered Islanding Incidents

With the growing deployment of microgrids, it has become urgent to investigate the microgrid behavior during transient faults and subsequent islanding conditions. The load type and the manner in which distributed generations (DGs) are controlled can have substantial impacts on the dynamic performance of microgrids. In this paper, impacts of different control schemes of the inverter-based DG and microgrid load types on the microgrid stability subsequent to fault-forced islanding are investigated. A microgrid model, simulated on Matlab/Simulink software, is analyzed including a mix of synchronous and inverter-based DG and a combination of passive RLC and induction motor (IM) loads. Simulation results show that in the presence of IM loads, the microgrid may lose its stable operation even if the fault is isolated within a typical clearing time. The critical clearing time of a microgrid is highly dependent on the microgrid control strategy, DG interface control, and load type. Induction motor loads can prove problematical to microgrid transient stability, particularly in situations in which the voltage dip can cause the induction motor to “pull out.”