A Novel Distributed Secondary Coordination Control Approach for Islanded Microgrids

This paper develops a new distributed secondary cooperative control scheme to coordinate distributed generators (DGs) in islanded microgrids (MGs). A finite time frequency regulation strategy containing a consensus-based distributed active power regulator is presented, which can not only guarantee the active power sharing but also enable all DGs' frequencies to converge to the reference value within a finite time. This enables the frequency and voltage control designs to be separated. Then an observer-based distributed voltage regulator involving certain reactive power sharing constraints is proposed, which allows different set points for different DGs and, thus, accounts for the line impedance effects. The steady-state performance analysis shows that the voltage regulator can accurately address the issue of global voltage regulation and accurate reactive power sharing. Moreover, all the distributed controllers are equipped with bounded control inputs to suppress the transient overshoot, and they are implemented through sparse communication networks. The effectiveness of the control in case of load variation, plug-and-play capability, communication topology change, link failure, time delays, and data drop-out are verified by the simulation of an islanded MG in MATLAB/SimPowerSystems

A New Adaptive Fuzzy PID Control Method and Its Applicance in FCBTM

The process of tension control for material testing using the Flexible ircuit Board testing machine (FCBTM) is featured with multi-variable, nonlinearity, ime delays and time variation. In order to ensure the tension precision, the stability of ervo motor’ speed and the reliability of test results, this paper establishes an accurate ystem model for the FCBTM, in which a novel three-dimensional adaptive fuzzy ID controller is designed. Specially, the simulation results show that the proposed daptive fuzzy control method is not only robust to the external disturbance but also ith more excellent dynamic and steady-state characteristics than traditional ones

Synchronization of Hybrid Microgrids with Communication Latency

A distributed cooperative control scheme is proposed in order to implement a distributed secondary control for hybrid lossy microgrids. The designed distributed control is able to synchronize the frequency of inverse-based distributed generators (DGs) and minisynchronous generators (MSGs/SGs) to the desired state with a virtual leader DG/SG (reference value) in a distribution switching network under the existence of time-varying communication delays. The secondary control stage selects suitable frequencies of each DG/SG such that they can be synchronized at the desired set point. Using the proposed algorithm, each DG/SG only needs to communicate with its neighboring DGs/SGs intermittently even if the communication networks are local, the topology is time-varying, and the communication delays may exist. Therefore, the failure of a single DG/SG will not produce the failing down of the whole system. Sufficient conditions on the requirements for the network connectivity and the delays boundedness which guarantees the stability and synchronization of the controlled hybrid lossy microgrid power systems are presented. The feasibility of the proposed control methodology is verified by the simulation of a given lossy microgrid test system

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

A Hybrid Constraints Handling Strategy for Multiconstrained Multiobjective Optimization Problem of Microgrid Economical/Environmental Dispatch

Microgrid (MG) economical/environmental dispatch (MGEED) problem is a complex multiobjective optimization topic. Since the generators are diversified and the operation mode changes frequently, the MGEEED problem always has different types of constraints, such as the load balance constraints and the ramp rates constraints, which make it a nonlinear, nonconvex optimization problem. In this paper, the mathematical model of a typical MG system applied in northwest China is established. Then, a hybrid constraints handling strategy (HCHS) based on nondominated sorting genetic algorithm II (NSGAII) is proposed to deal with the typical constraints, by which the constraints violations can be removed in several steps during the evolutionary process. A dimensionality reduction method is introduced to simplify the optimization model. And an individual repair approach is designed for the violations of ramp rates constraints. In order to balance the weights of various types of constraints, the process of constraints handling in standard NSGAII is revised. Thereafter, HCHS-NSGAII is applied to some typical MGEED problems, considering all kinds of typical constraints. The results show that HCHS-NSGAII can obtain feasible Pareto sets with satisfactory convergence and distribution, which is efficient in handling complex practical industrial MGEED problems with the change of constraints combinations