Distributed Control and Optimization of DC Microgrids: A Port-Hamiltonian Approach

This article proposes a distributed secondary control scheme that drives a dc microgrid to an equilibrium point where the generators share optimal currents, and their voltages have a weighted average of nominal value. The scheme does not rely on the electric system topology nor its specifications; it guarantees plug-and-play design and functionality of the generators. First, the incremental model of the microgrid system with constant impedance, current, and power devices is shown to admit a port-Hamiltonian (pH) representation, and its passive output is determined. The economic dispatch problem is then solved by the Lagrange multipliers method; the Karush-Kuhn-Tucker conditions and weighted average formation of voltages are then formulated as the control objectives. We propose a control scheme that is based on the Control by Interconnection design philosophy, where the consensus-based controller is viewed as a virtual pH system to be interconnected with the physical one. We prove the regional asymptotic stability of the closed-loop system using Lyapunov and LaSalle theorems. Equilibrium analysis is also conducted based on the concepts of graph theory and economic dispatch. Finally, the effectiveness of the presented scheme for different case studies is validated with a test microgrid system, simulated in both MATLAB/Simulink and OPAL-RT environments

Optimal Generation Capacity Allocation and Droop Control Design for Current Sharing in DC Microgrids

Considering the increasing amounts of renewable energy generation and energy storage required to meet ambitious environmental goals, it is clear that the next generation of power grids will be dominated by converter-connected devices. In addition, the increasing share of loads connected via power electronics and the general transition to non-synchronous grids with distributed generators make dc microgrids an attractive future alternative. However, achieving optimal utilization of distributed generators in such cases is a complex task, as the performance depends on both the grid and control design. In this paper, we consider such a case where the optimal utilization of distributed generators is achieved by optimal power sharing while taking into account the grid topology, the available generators, and the way they are controlled. For the latter, we consider a droop-based decentralized control scheme whose primary objective is to achieve voltage regulation in the allowable operating range. A novel mixed-integer optimization approach is proposed to identify the optimal converter size and location in the network so that the microgrid can operate safely and with optimal use of the available resources. Time-domain simulations are used to validate the proposed approach and demonstrate its robustness to uncertainty in generator availability

Economical Secondary Control of DC Microgrids

This paper proposes a distributed secondary voltage and current control aiming at economic dispatch of DC micro-grids. The dispatch problem is solved with the Lagrange method resulting in the equal incremental costs criterion. The proposed secondary controller realizes this criterion by using an average data consensus algorithm. A distributed dynamic data corrector is also proposed which ensures that the generators' output currents are always kept within the allowable ranges and that the total generation cost is as optimum as possible. Both physical and control systems considering constant impedance-current loads are formulated and stability of the system is briefly discussed. To verify the effectiveness of the proposed scheme, a test microgrid system is simulated in MATLAB/Simulink environment

Economical Secondary Control of DC Microgrids

This paper proposes a distributed secondary voltage and current control aiming at economic dispatch of DC micro-grids. The dispatch problem is solved with the Lagrange method resulting in the equal incremental costs criterion. The proposed secondary controller realizes this criterion by using an average data consensus algorithm. A distributed dynamic data corrector is also proposed which ensures that the generators' output currents are always kept within the allowable ranges and that the total generation cost is as optimum as possible. Both physical and control systems considering constant impedance-current loads are formulated and stability of the system is briefly discussed. To verify the effectiveness of the proposed scheme, a test microgrid system is simulated in MATLAB/Simulink environment

The Synthesis and Characterization of a Novel One-Dimensional Bismuth (III) Coordination Polymer as a Precursor for the Production of Bismuth (III) Oxide Nanorods

A novel Bi (III) coordination compound, [Bi(HQ)(Cl)4]n ((Q = pyridine-4-carbaldehyde thiosemicarbazone), was prepared in this research using a sonochemical technique. SEM, infrared spectroscopy (IR), XRD, and single-crystal X-ray analysis were utilized to analyze the Bi(III) coordination compound. The structure determined using single-crystal X-ray crystallography indicates that the coordination compound is a 1D polymer in solid state and that the coordination number of bismuth (III) ions is six, (BiSCl5), with one S donor from the organic ligand and five Cl donors from anions. It is equipped with a hemidirectional coordination sphere. It is interesting that the ligand has been protonated in the course of the reaction with a Cl- ion balancing the charge. This compound’s supramolecular properties are directed and regulated by weak directional intermolecular interactions. Through π–π stacking interactions, the chains interact with one another, forming a 3D framework. Thermolysis of the compound at 170 °C with oleic acid resulted in the formation of pure phase nanosized Bi (III) oxide. SEM technique was used to examine the morphology and size of the bismuth (III) oxide product produced

The Synthesis and Characterization of a Novel One-Dimensional Bismuth (III) Coordination Polymer as a Precursor for the Production of Bismuth (III) Oxide Nanorods

A novel Bi (III) coordination compound, [Bi(HQ)(Cl)4]n ((Q = pyridine-4-carbaldehyde thiosemicarbazone), was prepared in this research using a sonochemical technique. SEM, infrared spectroscopy (IR), XRD, and single-crystal X-ray analysis were utilized to analyze the Bi(III) coordination compound. The structure determined using single-crystal X-ray crystallography indicates that the coordination compound is a 1D polymer in solid state and that the coordination number of bismuth (III) ions is six, (BiSCl5), with one S donor from the organic ligand and five Cl donors from anions. It is equipped with a hemidirectional coordination sphere. It is interesting that the ligand has been protonated in the course of the reaction with a Cl- ion balancing the charge. This compound’s supramolecular properties are directed and regulated by weak directional intermolecular interactions. Through π–π stacking interactions, the chains interact with one another, forming a 3D framework. Thermolysis of the compound at 170 °C with oleic acid resulted in the formation of pure phase nanosized Bi (III) oxide. SEM technique was used to examine the morphology and size of the bismuth (III) oxide product produced

Ultrasound-Assisted Synthesis and DFT Calculations of the Novel 1D Pb (II) Coordination Polymer with Thiosemicarbazone Derivative Ligand and Its Use for Preparation of PbO Clusters

In the present work, using a sonochemical method, a new lead (II) coordination 1D polymer, [Pb(L)2(CH3COO)]n (L = pyridine-4-carbaldehyde thiosemicarbazone) (1) was prepared. It was characterized structurally with different spectroscopic methods, such as SEM, IR spectroscopy, XRD, and elemental analysis. The coordination compound becomes a stair-step one-dimensional polymer in solid mode. The lead (II) ions have the coordination number of six (PbNS3O2) with two oxygen atoms from acetate anion and three sulfur atoms and one nitrogen atom from organic ligand. It contains a stereo-chemically active lone electron pair and the hemidirected coordination sphere. The high-intensity ultrasound is considered a flexible, environmentally friendly, and easy synthetic tool for the coordination compounds. PbO clusters was achieved with thermolyzing 1 at 180 ˚C with oleic acid (as a surfactant). Furthermore, the size and morphology of the created PbO clusters were assessed via SEM. The estimated gap of HOMO and LUMO is 3.275 eV based on DFT calculations