Showing papers on "Microgrid published in 2007"
TL;DR: In this paper, the authors developed a model for autonomous operation of inverter-based micro-grids, where each sub-module is modeled in state-space form and all are combined together on a common reference frame.
Abstract: The analysis of the small-signal stability of conventional power systems is well established, but for inverter based microgrids there is a need to establish how circuit and control features give rise to particular oscillatory modes and which of these have poor damping. This paper develops the modeling and analysis of autonomous operation of inverter-based microgrids. Each sub-module is modeled in state-space form and all are combined together on a common reference frame. The model captures the detail of the control loops of the inverter but not the switching action. Some inverter modes are found at relatively high frequency and so a full dynamic model of the network (rather than an algebraic impedance model) is used. The complete model is linearized around an operating point and the resulting system matrix is used to derive the eigenvalues. The eigenvalues (termed "modes") indicate the frequency and damping of oscillatory components in the transient response. A sensitivity analysis is also presented which helps identifying the origin of each of the modes and identify possible feedback signals for design of controllers to improve the system stability. With experience it is possible to simplify the model (reduce the order) if particular modes are not of interest as is the case with synchronous machine models. Experimental results from a microgrid of three 10-kW inverters are used to verify the results obtained from the model
2,482 citations
TL;DR: The paper explorers the resistive output impedance of the parallel-connected inverters in an island microgrid and proposes a novel wireless load-sharing controller for islanding parallel invertes in an ac distributed system.
Abstract: In this paper, a novel wireless load-sharing controller for islanding parallel inverters in an ac-distributed system is proposed This paper explores the resistive output impedance of the parallel-connected inverters in an island microgrid The control loops are devised and analyzed, taking into account the special nature of a low-voltage microgrid, in which the line impedance is mainly resistive and the distance between the inverters makes the control intercommunication between them difficult In contrast with the conventional droop-control method, the proposed controller uses resistive output impedance, and as a result, a different control law is obtained The controller is implemented by using a digital signal processor board, which only uses local measurements of the unit, thus increasing the modularity, reliability, and flexibility of the distributed system Experimental results are provided from two 6-kVA inverters connected in parallel, showing the features of the proposed wireless control
928 citations
TL;DR: The results obtained show the successful implementation of HFAC Microgrid with adequate power flow and power quality control, as well as the optimization of operation cost by the DIEMS with Fuzzy ARTMAP-based day-type forecasting.
Abstract: In this paper, a single-phase high-frequency AC (HFAC) microgrid is shown as a novel solution towards integrating renewable energy sources in a distributed generation system. Better utilization of the Microgrid is achieved by solving power flow and power quality issues using p-q theory-based active filtering called universal active power line conditioner and unified power quality conditioner, respectively. A distributed intelligent energy management system (DIEMS) is implemented to optimize operating costs. As the optimization greatly depends on the power generation and the power output from renewable sources strongly depends on the weather, the forecast of power generation is required for DIEMS. A Fuzzy ARTMAP neural network is used to predict hourly day-type outputs based on which generation can be forecasted. Depending on the forecast, an optimization scheme is developed utilizing linear programming along with heuristics. The results obtained show the successful implementation of HFAC Microgrid with adequate power flow and power quality control, as well as the optimization of operation cost by the DIEMS with Fuzzy ARTMAP-based day-type forecasting. The improvement in the battery life is also achieved due to optimization of storage charge states using the proposed DIEMS
393 citations
15 Oct 2007
TL;DR: In this paper, an adaptive control system for a dc microgrid for data centers is proposed, which coordinates the control of converters, sources and switches used in the DC microgrid.
Abstract: In this paper, an adaptive control system for a dc microgrid for data centers is proposed. Data centers call for electric power with high availability and a possibility to reduce the electric losses and hence the need for cooling. By using local energy sources, high reliability can be achieved, and by using dc the number of conversion steps, and therefore also the losses, can be reduced. The dc microgrid can also be used to supply closely located sensitive ac loads during outages on the utility grid. The proposed dc microgrid can be operated in eight different operation modes described here, resulting in 23 transitions. The adaptive control system coordinates the control of converters, sources and switches used in the dc microgrid. The adaptive control system is tested in the simulation software packages PSCAD/EMTDC, and the results of the most interesting operation modes and transitions are presented. The results show that it is possible to use the proposed dc microgrid to supply sensitive electronic loads, and also during utility grid outages, supply closely located sensitive ac loads. To reduce transients in the voltage experienced by the sensitive ac loads, the dc microgrid requires fast utility outage detection and fast switches.
371 citations
TL;DR: In this article, the authors proposed a system approach which views generation and associated loads as a subsystem or a microgrid, where the sources can operate in parallel to the grid or can operate on an island, providing utility power station services.
Abstract: Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a “microgrid.” The sources can operate in parallel to the grid or can operate in island, providing utility power station services. The system will disconnect from the utility during large events (e.g., faults and voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. University of Wisconsin laboratory verification of microgrid control concepts are included.
364 citations
16 Apr 2007
TL;DR: The paper summarizes and highlights the operating principles and key conclusions of research and field trials to-date for Microgrid operation, and an overview on demonstration projects for Microgrids which have been, and are being, constructed.
Abstract: Microgrids are networks of small, distributed electrical power generators operated as a collective unit - a system of energy systems. The range of hardware and control options for Microgrid operation are reviewed. The paper summarizes and highlights the operating principles and key conclusions of research and field trials to-date. An overview is given on demonstration projects for Microgrids which have been, and are being, constructed.
360 citations
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TL;DR: In this article, the static switch is designed to open for all faults and the philosophy for protection is to have the same protection strategies for both islanded and grid-connected operation.
Abstract: In general, a microgrid can operate in both the grid-connected mode and the islanded mode where the microgrid is interfaced to the main power system by a fast semiconductor switch called static switch, (SS). It is essential to protect a microgrid in both the grid-connected and the islanded modes of operation against all types of faults. The major issue arises in island operation with inverter-based sources. Inverter fault currents are limited by the ratings of the silicon devices to around 2 p.u. rated current. Fault currents in islanded inverter based microgrids may not have adequate magnitudes to use traditional overcurrent protection techniques. The philosophy for protection is to have the same protection strategies for both islanded and grid-connected operation. The static switch is designed to open for all faults.
351 citations
TL;DR: In this paper, a systematic approach to small-signal modeling of a micro-grid system that includes conventional (rotating machine) and electronically interfaced distributed resource (DR) units is presented.
Abstract: A systematic approach to small-signal modelling of a micro-grid system that includes conventional (rotating machine) and electronically interfaced distributed resource (DR) units is presented here. The proposed approach incorporates fundamental frequency deviations in the overall system model and provides a methodology for the analysis of autonomous micro-grid, which inherently is more prone to frequency changes than the conventional utility grid. The model represents (i) electro-mechanical dynamics of the synchronous machine including the exciter and the governor systems, (ii) dynamics of the voltage-sourced converter and its real/reactive power controllers and (iii) the network dynamics. The model is intended for the controller design/optimisation, evaluation of angle/voltage stability, investigation of torsional dynamics, controller interactions of electronically interfaced DR units and low-frequency power quality issues. Typical results from application of the proposed modelling approach to a study system are presented. The results are qualitatively verified on the basis of the comparison with those obtained from time-domain simulation in the PSCAD/EMTDC environment
307 citations
TL;DR: In this article, a sequence of actions and conditions to be checked during service restoration in the low voltage area are identified and tested through numerical simulation, and the need of storage devices is addressed in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality.
Abstract: Under normal operating conditions, a MicroGrid is interconnected with the medium voltage network; however, in order to deal with black start and islanded operation following a general blackout, an emergency operation mode must be envisaged. A sequence of actions and conditions to be checked during the restoration stage are identified and tested through numerical simulation. Voltage and frequency control approaches, inverter control modes, and the need of storage devices are addressed in this paper in order to ensure system stability, achieve robustness of operation, and not jeopardize power quality during service restoration in the low voltage area
269 citations
TL;DR: In this article, a cooperative harmonic filtering strategy for the interface converters of distributed generation sources is proposed, and a droop control method based on the reactive volt-ampere consumption of harmonics of each interface converter is implemented.
Abstract: Increasing demand for premium electric power, in terms of both quality and reliability, and emerging new energy technologies have led to the development of distributed generation systems Due to rapid penetration of power electronics equipment, many of the loads within distributed generation systems are nonlinear in nature, and the resulting harmonics pollution needs to be addressed This paper proposes a new cooperative harmonic filtering strategy for the interface converters of distributed generation sources A droop control method based on the reactive volt-ampere consumption of harmonics of each interface converter is designed and implemented In this strategy, the overall harmonic filtering workload can be evenly shared without any communications The operation principle is explained in detail Computer simulations and laboratory test results validate the distributed harmonic damping capability of the proposed strategy
261 citations
12 Apr 2007
TL;DR: In this paper, a generalized formulation for determining the optimal operating strategy and cost optimization scheme as well as reducing the emissions of a microgrid (MG) is presented. And the optimization is aimed at minimizing the cost function of the system while constraining it to meet the costumer demand and safety.
Abstract: This paper presents a generalized formulation for determining the optimal operating strategy and cost optimization scheme as well as reducing the emissions of a MicroGrid (MG). Multiobjective (MO) optimization is applied to the environmental economic problem of the MG. The proposed problem is formulated as a nonlinear constrained MO optimization problem Prior to the optimization, system model components taken from real manufactural data are constructed. The model takes into consideration the operation and maintenance costs as well as the reduction in emissions of NOx, SO 2 , and CO 2 . The MG considered in this paper consists of a wind turbine, a micro turbine, a diesel generator, a photovoltaic array, a fuel cell, and a battery storage. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the costumer demand and safety of the system. The results demonstrate the efficiency of the proposed approach to satisfy the load and to reduce the cost and the emissions in one single run.
Journal Article•
TL;DR: In this paper, a transition from DG to microgrid is presented and a typical topological structure of micro-grid is employed to demonstrate its unique characteristics, and the key topics and ongoing research and development programs are also listed and analyzed.
Abstract: As an effective way to solve various problems in modern power systems,microgrid is increasingly adopted in many developed countries.Via detailing the concept and schemes of microgrid worldwide,the paper aims to clarify the differences and similarities between microgrid and distributed generation(DG),and give some advices on its application in China.Firstly,the transition from DG to microgrid is presented and a typical topological structure of microgrid is employed to demonstrate its unique characteristics.Secondly,researches and developments on microgrid in various countries are summarized.The key topics and ongoing research and development programs are also listed and analyzed.Finally,based on the energy strategies and status of power systems in China,the developing potentials and the possible applications of microgrid in China are discussed.
01 Jul 2007
TL;DR: In this paper, a hierarchical approach is presented to deal with the problem of controlling frequency and active power generation of a medium voltage network comprising several mi- crogrids and distributed generation sources operated in islanded mode.
Abstract: This paper presents a new hierarchical approach to deal with the problem of controlling frequency and active power generation of a medium voltage network comprising several mi- crogrids and distributed generation sources operated in islanded mode. The hierarchical approach described here should be cost effective and capable of dealing with large numbers of distributed microsources and performing tasks related to coordinated frequency control.
24 Jun 2007
TL;DR: In this paper, the concept of a specialized microgrid called an intelligent distributed autonomous power system (IDAPS) is presented, which aims at intelligently managing customer-owned distributed energy resources such that these assets can be shared in an autonomous grid both during normal and outage operations.
Abstract: The electric power system is an enabling infrastructure that supports the operation of other critical infrastructures and thus the economic well-being of a nation. It is, therefore, very important to design for resiliency and autonomous reconfigurability in the electric power grid to guard against man-made and natural disasters. One way to assure such self-healing characteristics in an electric power system is to design for small and autonomous subsets of the larger grid. This paper presents the concept of a specialized microgrid called an intelligent distributed autonomous power system (IDAPS). The IDAPS microgrid aims at intelligently managing customer-owned distributed energy resources such that these assets can be shared in an autonomous grid both during normal and outage operations. The proposed concept is expected to make significant contributions during emergency conditions, as well as creating a new market for electricity transaction among customers.
Proceedings Article•
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TL;DR: Field verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included, and utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive.
Abstract: Application of individual distributed generators can cause as many problems as it may solve. A better way to realize the emerging potential of distributed generation is to take a system approach which views generation and associated loads as a subsystem or a "microgrid". The sources can operate in parallel to the grid or can operate in island, providing UPS services. The system will disconnect from the utility during large events (i.e. faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. Utilization of waste heat from the sources will increase total efficiency, making the project more financially attractive. Field verification of the Consortium for Electric Reliability Technology Solutions (CERTS) microgrid control concepts are included.
24 Jun 2007
TL;DR: In this paper, an energy-flow model developed for performance analysis and unit sizing of an autonomous wind-diesel microgrid was introduced for unit sizing and operating constraints of a microgrid with three equally sized diesel generators.
Abstract: This paper introduces an energy-flow model developed for performance analysis and unit sizing of an autonomous wind-diesel microgrid A remote community in Canada is used as the study system, for which a medium penetration wind power plant has been integrated into a system served by a diesel plant with three equally sized diesel generators Based on field observations and monitored data for almost two years of operation, an energy-flow model is developed which incorporates operating constraints and control requirements of the autonomous wind- diesel system The model is employed to analyze the interaction of wind and diesel power plants in order to identify alternative unit sizing approaches that improve wind-energy absorption rate of the wind plant, fuel savings and overall efficiency of the diesel plant Optimization criteria for unit sizing of the diesel plant in the presence of the wind farm are discussed and system performance for several configurations based on multiple units with reduced-size diesel unit are investigated The simulation results from the energy-flow model for two operation scenarios are compared with the field observations and an optimum combination of multiple diesels with reduced-size units is suggested
TL;DR: In this article, an algorithm is presented, suitable for simulating the dynamic behavior of LV Microgrids both under grid connected and autonomous operation, focusing on low-frequency dynamics, and adjusts the standard methodology so that the dynamic analysis of the system can be carried out, even in the absence of a synchronous machine when all the sources are interfaced to the network with inverters.
Abstract: In this paper, an algorithm is presented, suitable for simulating the dynamic behavior of LV Microgrids both under grid connected and autonomous operation. The algorithm follows the stability approach, focusing on low-frequency dynamics, and adjusts the standard methodology so that the dynamic analysis of the system can be carried out, even in the absence of a synchronous machine when all the sources are interfaced to the network with inverters. Proper network representation allows for the modeling of all the characteristic unbalances of the LV network. The capability of the algorithm to simulate the operating modes of a Microgrid is demonstrated by representative study cases
24 Jun 2007
TL;DR: In this article, a general framework for the control of distributed energy resources organized in micro-grids is presented, which is based on the agent technology and aims to integrate several functionalities, as well to be adaptable to the complexity and the size of the microgrid.
Abstract: This paper presents a general framework for the control of distributed energy resources organized in microgrids. The proposed architecture is based on the agent technology and aims to integrate several functionalities, as well to be adaptable to the complexity and the size of the microgrid. To achieve this, the idea of layered learning is used, where the various controls and actions of the agents are grouped depending on their effect on the environment. A novel approach called multiagent reinforcement learning is introduced in order to increase the intelligence and the efficiency of the microgrid.
04 Sep 2007
TL;DR: In this article, some problems of power electronic converters in author's DC microgrid are discussed, where the converters are divided into groups depending on their destination and the main groups are presented in more details.
Abstract: Some specialists claim that present power systems come to the end. The first of all reason is fossil fuels run low. One of the solutions allows avoiding the problem is local balancing of power production and power demand. The easiest to reach local non fossil carriers are wind, sun and water and biomass energy. But they are unstable and it is very hard to produce stable power from them. Microglia's were developed to solve the problem. The microgrid is small power system composed of power plants, controlled and uncontrolled loads and control system (just like in classic, huge power system). Because microgrid is rather small it has to be an automatic and operate without any staff. Hence, many electronic devices are necessary. First of all these are power plants controllers. The plants using in the microgrid are electronic devices. Also some loads are connected through electronic connection units. Power electronic converters are the most important part of both plants and connections. The paper discusses some problems of power electronic converters in author's DC microgrid. The converters are divided into groups depending of their destination. The main groups are presented in more details.
16 Apr 2007
TL;DR: This paper investigates the fault behaviour of an inverter-only supplied microgrid by computer simulation and numerical analysis to give a qualitative and quantitative understanding of the dynamics involved in a microgrid under fault conditions.
Abstract: This paper investigates the fault behaviour of an inverter-only supplied microgrid by computer simulation and numerical analysis. The purpose of this study is to give a qualitative and quantitative understanding of the dynamics involved in a microgrid under fault conditions in order to supply a tool to help the design of a suitable fault detection strategy. After considering first the nature of microgrids and the control of stand-alone inverters, a model of a microgrid supplied by one single inverter-interfaced source is simulated in PSCAD for two different faults conditions. Simplifications to the inverter model which captures its behaviour under fault conditions are then proposed. Finally the effectiveness of the simplified model is demonstrated using a sequence-component-based fault analysis of the microgrid test network.
TL;DR: In this paper, the authors proposed a method for the economic evaluation of an autonomous independent network of distributed energy resources called Microgrid Microgrid is a new framework of power delivery system that is formed by small, modular generation systems connected to each other to create a small autonomous grid.
21 May 2007
TL;DR: A generalized formulation to determine the optimal operating strategy and cost optimization scheme as well as the reduction of the emissions for a MicroGrid (MG) is presented.
Abstract: This paper presents a generalized formulation to determine the optimal operating strategy and cost optimization scheme as well as the reduction of the emissions for a MicroGrid (MG). Multiobjective (MO) optimization is applied to the environmental/economic problem of the MG. The proposed problem is formulated as a nonlinear constrainted MO optimization problem. Prior to the optimization, a system model components from some real manufactural data are constructed. The model takes into consideration the operation and maintenance costs as well as the emissions NOx, SO2, and CO2 reduction. The MG considered in this paper consists of a wind turbine, a micro turbine, a diesel generator, a photovoltaic array , and fuel cell. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the costumer demand and safety of the system.The results demonstrate the efficiency of the proposed approach to satisfy the load and to reduce the cost and the emissions in one single run.
01 Jul 2007
TL;DR: A new method, based on stochastic optimization, is proposed to optimize the operation of a microgrid, which involves optimization of the production of the local micro- sources and storage and the exchange with the main distribution grid subject to market conditions.
Abstract: The unbundling of power systems and the emergence of electricity markets favor the deployment of distributed generation in electricity networks. Microgrids are low-voltage distribution networks comprising micro-generation, storage devices and controllable loads that can operate interconnected or isolated from the main distribution grid as a controlled entity. This paper proposes a new method, based on stochastic optimization, to optimize the operation of a microgrid. This involves optimization of the production of the local micro- sources and storage and the exchange with the main distribution grid subject to market conditions. The results of the stochastic approach, and a comparison with a simpler deterministic one are presented using as case study a typical microgrid.
16 Apr 2007
TL;DR: The novel concept of using the central energy storage system (flywheel) as the main fault current source in islanded mode in islanding mode is presented.
Abstract: A MicroGrid is expected to operate both as a sub system connected to the main grid or as an islanded system. However the provision of fault currents, in an islanded MicroGrid consisting only of micro-generation interfaced with relatively low-current power electronics, is a serious system protection issue. This paper presents the novel concept of using the central energy storage system (flywheel) as the main fault current source in islanded mode. The three-phase MicroGrid test rig used at University of Manchester, and the flywheel control system are described. The importance of accurate systems modeling of the whole microgrid and energy storage unit is shown. A fault study is carried out on the test rig and in PSCAD. The flywheel inverter system is shown to contribute enough fault current for a sufficient duration to cause the system protective device to clear the fault.
TL;DR: In this paper, a generalized formulation is presented to determine the optimal operating strategy and cost optimization scheme for a microgrid. And the optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of the systems.
Abstract: This paper presents a generalized formulation to determine the optimal operating strategy and cost optimization scheme for a MicroGrid. Prior to the optimization of the microgrid itself, the system model components from some real manufactural data are constructed. The proposed cost function takes into consideration the costs of the emissions NOx, SO2, and CO2 as well as the operation and maintenance costs. The microgrid considered in this paper consists of a wind turbine, a micro turbine, a diesel generator, a photovoltaic array , a fuel cell, and a battery storage. The optimization is aimed at minimizing the cost function of the system while constraining it to meet the customer demand and safety of the system.
01 Jul 2007
TL;DR: In this article, the authors presented a generalized formulation to determine the optimal operating strategy and cost optimization scheme as well as the reduction of the emissions for a microgrid (MG) in order to minimize the operating cost of the system while constraining it to meet the costumer demand and safety.
Abstract: This paper presents a generalized formulation to determine the optimal operating strategy and cost optimization scheme as well as the reduction of the emissions for a MicroGrid (MG). Multiobjective (MO) optimization is applied to the environmental/economic problem of the MG. The proposed problem is formulated as a nonlinear constrained MO optimization problem. The model takes into consideration the operation and maintenance costs as well as the emissions NOx, SO2, and CO2 reduction. The MG considered in this paper consists of a wind turbine, a micro turbine , a diesel generator , a photovoltaic array , a fuel cell, and a battery storage. The optimization is aimed at minimizing the operating cost of the system while constraining it to meet the costumer demand and safety of the system. We also added a daily income and outgo from sold and purchased power. The results demonstrate the efficiency of the proposed approach to satisfy the load and to reduce the cost and the emissions in one single run.
01 Jul 2007
TL;DR: In this article, the authors examined the feasibility of FHES control, especially dynamic control of electrolyzer system, to secure real power balance and enhance the operation capability of handling frequency fluctuation.
Abstract: Compounding the various kinds of power sources would impact the quality of power supply within the MicroGrid and cause many control problems to be dealt with. This paper focuses on the stability of MicroGrid operation and discusses the control techniques of combining micro turbine and Fuel cell, Hydrogen tank, and Electrolyzer system hybrid System (FHES) to expand the MicroGrid system's ability for solving power quality issue of frequency fluctuation. The paper examines the feasibility of FHES control, especially dynamic control of electrolyzer system, to secure real power balance and enhance the operation capability of handling frequency fluctuation. It is presented that the Proposed PC control and monitoring system can be considered as a means of power quality control to improve the frequency fluctuation caused by a random power fluctuation on generation and load sides and to relax a tie line power flow fluctuation by the frequency one on the interconnected MicroGrid local power system.
07 May 2007
TL;DR: In this article, a novel droop control scheme applied to distributed UPSs forming a microgrid is proposed, which consists of two levels of hierarchy: 1) the P/Q control method of every UPS unit and 2) the management of the microgrid through the control of the setpoints of the units and the intelligent switch connected to the strong grid.
Abstract: In this paper, a novel droop control scheme applied to distributed UPSs forming a microgrid is proposed. The control architecture consists of two levels of hierarchy: 1) the P/Q droop control method of every UPS unit and 2) the management of the microgrid through the control of the setpoints of the units and the intelligent switch connected to the strong grid. This second level of control let us to connect or disconnect the microgrid to the utility mains, resulting in two scenarios: grid-connected and islanding operation mode. Also, it is taken into account the seamlessly transition between both operation modes, the possibility to share power with the utility grid, and the energy management of the overall system.
Journal Article•
TL;DR: In this article, an Hinfin controller is designed for the voltage-source-inverter voltage control in a microgrid to compensate the capacitance-parameter variation.
Abstract: Capacitors are widely used for power-factor correction (PFC) in power systems. When a PFC capacitor is installed with a certain load in a microgrid, it may be in parallel with the filter capacitor of the inverter interfacing the utility grid and the local distributed-generation unit and, thus, change the effective filter capacitance. Another complication is the possibility of occurrence of resonance in the microgrid. This paper conducts an in-depth investigation of the effective shunt-filter-capacitance variation and resonance phenomena in a microgrid due to a connection of a PFC capacitor. To compensate the capacitance-parameter variation, an Hinfin controller is designed for the voltage-source- inverter voltage control. By properly choosing the weighting functions, the synthesized Hinfin controller would exhibit high gains at the vicinity of the line frequency, similar to traditional high- performance P+ resonant controller and, thus, would possess nearly zero steady-state error. However, with the robust Hinfin controller, it will be possible to explicitly specify the degree of robustness in face of parameter variations. Furthermore, a thorough investigation is carried out to study the performance of inner current-loop feedback variables under resonance conditions. It reveals that filter-inductor current feedback is more effective in damping the resonance. This resonance can be further attenuated by employing the dual-inverter microgrid conditioner and controlling the series inverter as a virtual resistor affecting only harmonic components without interference with the fundamental power flow. And finally, the study in this paper has been tested experimentally using an experimental microgrid prototype.
24 Jun 2007
TL;DR: In this paper, the authors presented an optimization approach to choose such systems and their operating schedules using Berkeley Lab's Distributed Energy Resources Customer Adoption Model [DER-CAM], extended to incorporate electrical storage options.
Abstract: The deployment of small (<1-2 MW) clusters of generators, heat and electrical storage, efficiency investments, and combined heat and power (CHP) applications (particularly involving heat activated cooling) in commercial buildings promises significant benefits but poses many technical and financial challenges, both in system choice and its operation; if successful, such systems may be precursors to widespread microgrid deployment. The presented optimization approach to choosing such systems and their operating schedules uses Berkeley Lab's Distributed Energy Resources Customer Adoption Model [DER-CAM], extended to incorporate electrical storage options. DER-CAM chooses annual energy bill minimizing systems in a fully technology-neutral manner. An illustrative example for a San Francisco hotel is reported. The chosen system includes two engines and an absorption chiller, providing an estimated 11% cost savings and 10% carbon emission reductions, under idealized circumstances.