Juan Carlos Vasquez Quintero

Economic Dispatch for Operating Cost Minimization Under Real-Time Pricing in Droop-Controlled DC Microgrid

In this paper, an economic dispatch problem for total operation cost minimization in dc microgrids is formulated. An operating cost is associated with each generator in the microgrid, including the utility grid, combining the cost-efficiency of the system with demand response requirements of the utility. The power flow model is included in the optimization problem, thus the transmission losses can be considered for generation dispatch. By considering the primary (local) control of the grid-forming converters of a microgrid, optimal parameters can be directly applied to this control level, thus achieving higher control accuracy and faster response. The optimization problem is solved in a heuristic method. In order to test the proposed algorithm, a six-bus droop-controlled dc microgrid is used in the case studies. Simulation results show that under variable renewable energy generation, load consumption, and electricity prices, the proposed method can successfully reduce the operating cost by dispatching economically the resources in the microgrid.

A Robot-Soccer-Coordination Inspired Control Architecture Applied to Islanded Microgrids

Nowadays, islanded microgrids present a high interest due to the increasing penetration of renewable energy resources, especially in remote areas, or for improving the local energy reliability. A microgrid can operate in grid-connected or islanded mode, being necessary the use of energy storage systems (ESSs) under islanded operation, in order to ensure the generation/consumption power balance and smooth uncertainties in the dynamics of the renewable energy sources (RESs). Particularly, in islanded operation at least one of the distributed energy resources (DERs) should assume the regulation of the common bus. In a microgrid, every DER may be able to cooperate with the grid regulation in accordance to its particular operational conditions. In this sense, a centralized unit with a global perception of the load demand, the power provided by the RESs, and the storage capacity of the ESSs, may ensure proper and reliable operation of the microgrid. This paper proposes a structured architecture based on tactics, roles, and behaviors for a coordinated operation of islanded microgrids. The architecture is inspired on a robot soccer strategy with global perception and centralized control, which determines the changes among operation modes for the DERs in an islanded ac microgrid.

Voltage Unbalance and Harmonic Compensation in Microgrids by Cooperation of Distributed Generators and Active Power Filters

In this paper, the power quality of microgrids is addressed. To achieve the desired level of power quality, a strategy based on the coordinated control between DGs and APFs is proposed. In this regard, hierarchical control is applied where primary control consists of power droop controller of DGs, selective virtual impedance and voltage/current regulators. Based on the secondary control, at first voltage harmonic compensation and voltage unbalance compensation of point of common coupling (PCC), that might includes sensitive loads, is carried out by DGs. Voltage compensation of PCC by DGs may cause severe voltage distortion at DGs terminals. Thus, the coordinated control is used to mitigate the voltage distortion to the defined maximum allowable value at DGs terminals. Evaluation of the proposed hierarchical control is carried out by a simulation study.

Distributed Coordination of Electric Vehicle Charging in a Community Microgrid Considering Real-Time Price

The predictable increasing adoption of EV by residential users imposes the necessity of Electric Vehicle charging coordination, in order to charge effectively while minimizing the impact on the grid. In this paper, a two-stage distributed coordination algorithm for electric vehicle charging management in a community microgrid is proposed. Each local EV charging controller is taken as an agent, which can manage the charging to achieve the optimization of the whole community by communicating in a sparse network. The proposed algorithm aims at optimizing real-time, which manages the charging activity based on the real-time price, while meeting the requirement of technical constraints of the distribution system.

High-Order Frequency-Locked Loops: A Critical Analysis

In very recent years, some attempts for designing high-order frequency-locked loops (FLLs) have been made. Nevertheless, the advantages and disadvantages of these structures, particularly in comparison with a standard FLL and high-order phase-locked loops (PLLs), are rather unclear. This lack of knowledge is attributable to the difficulty of small-signal modeling of these high-order FLLs, which has limited their analysis to numerical studies. Focusing on three-phase FLLs, the idea of designing high-order FLLs is first generalized in this letter. Then, a second-order FLL is considered as the case study, and its small-signal modeling, stability analysis, and parameter tuning are presented. Finally, to gain insight about advantages and disadvantages of high-order FLLs, a theoretical and experimental performance comparison between the designed second-order FLL and a standard FLL (first-order FLL) as well as a unification between FLLs and PLLs is presented.

Method for Load Sharing and Power Management in a Hybrid PV/Battery Source Islanded Microgrid

This paper presents a decentralized load sharing and power management method for an islanded microgrid composed of PV units, battery units and hybrid PV/battery units. The proposed method performs all the necessary tasks such as load sharing among the units, battery charging and discharging and PV power curtailment with no need to any communication among the units. The proposed method is validated experimentally.

A Root-Locus Design Methodology Derived from the Impedance Stability Criterion and Its Application for LCL Grid-Connected Converters

This paper presents a systematic methodology for design and tuning of the controller of LCL grid-connected converters. The proposed approach is derived from the impedance/admittance stability formulation, which eases the controller modelling of LCL grid-connected systems. After system modelling, a modified sensitivity function is defined to analyze the closed loop dynamics. For practical development, the control objectives are linked to main requirements in wind turbine applications: 1) the current control time constant should be minimized and 2) active damping actions should effectively mitigate the LCL resonance. After the theoretical development, an insightful case study is provided. It is shown that the tuning problem can be solved approximately by root-loci inspection and an optimum solution can be found by direct search. The theoretical approach is experimentally verified by a lab-scale prototype that uses the same parameters of the case study.

Control Design of VSIs to Enhance Transient Performance in Microgrids

This paper discusses the control design for an islanded microgrid in order to ensure acceptable performance in terms of voltage quality and load sharing by focusing on transient conditions. To this aim, state feedback decoupling approach has been applied. Experimental tests have been performed to demonstrate the effectiveness of the proposed approach.

Advanced Smart Metering Infrastructure for Future Smart Homes

Smart buildings and homes are becoming a key player in the future green and sustainable energy grid, due to the integration of distributed energy sources and the demand control capabilities. Advanced smart metering systems are required for the operation of the future smart grid. Smart metering systems allow to monitor the energy consumption of end-users, while provides useful information regarding power quality. The information provided by these systems is used by the system operator to enhance the energy supply, and several techniques, as load scheduling, demand side management, non-intrusive load monitoring, can be applied for this purpose. This paper shows an advanced smart metering infrastructure for integration in future smart homes, where not only the electrical consumption is monitored, but also the gas, water, and heating. Therefore, by monitoring all energy systems in the building, the users could be aware of their whole energy consumption, and advanced control techniques can achieved by the Energy Management Systems (EMS).