EPE Association: EPE 2017 - DS2l: Micro-grids

EPE 2017 - DS2l: Micro-grids
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2017 ECCE Europe - Conference > EPE 2017 - Topic 06: Grids and Smart Grids > EPE 2017 - DS2l: Micro-grids

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   Application of Cloud Computing in Power Routing for Clusters of Microgrids Using Oblivious Network Routing Algorithm
By Kianoosh BOROOJENI [View]
[Download]

Abstract: In this paper, we propose a comprehensive co-simulation platform for the clusters of microgrids. Our proposed real-time platform considers both physical and communication layers, which can be simulated via real-time digital power system simulator (RTDS) and OMNeT++. We also propose a novel oblivious power routing scheme to prevent congestion and minimize network loss. To this end, we firstly introduce the algorithms referred to as oblivious routing-based economic dispatch. Oblivious network routing, which is applicable to large-scale networks with arbitrary topology, such as power grids, communication networks, and world-wide-web, is a metaheuristic solution to approximate network optimization problems under oblivious constraints utilizing advanced data structures and hypergraphs. Our oblivious power routing algorithms are also well suited for finding the optimal power flows through a cluster of microgrid while preventing congestion as well as minimizing the power loss. Then, we present a two-layer simulation platform which considers both communication layer and physical layer of the microgrids' cluster. In order to improve the security of communication network, we perform the computations regarding the oblivious power routing via a cloud-based network. The proposed framework can be used for further studies that deal with the real-time simulation of the clusters of microgrids. In order to validate the effectiveness of the proposed framework, we implement our proposed oblivious routing scheme on a cluster of 13 microgrids.

   Customized Power Quality Service Provided by Converter Interfaced Microgrids - Voltage Harmonics as a Study Case
By Lexuan MENG [View]
[Download]

Abstract: Customers may have different power quality requirements, thus, the economic operational strategy can try to provide them with distinctive quality levels as customized service. An optimization based method is proposed in this paper to realize this functionality, offering the possibility that the customers can flexibly set and adjust their requirements. Converter interfaced distributed generators are used as compensators. Simulation results show that the proposed method is able to limit the voltage harmonics at each bus within respective limits.

   DC microgrids with energy storage systems and demand response for providing support to frequency regulation of electrical power systems
By Hrvoje BASIC [View]
[Download]

Abstract: Frequency regulation of electric power systems efficiency depends on response time and on power reserves for frequency regulation. As integration of non-dispatchable renewable generation in the power system results with increased need for power reserves from fast responding power units, the idea of using aggregated DC microgrids in frequency regulation is presented. Model proposed in this work is based on using battery energy storage, combined with demand response for achieving efficient usage of battery energy storage. It is shown that large number of DC microgrids can provide sufficient energy and fast responding power, to improve efficiency of frequency regulation of electric power system.

   Design and Small-Signal Stability Analysis of a Virtual-Capacitor Control for DC Microgrids
By Eneko UNAMUNO [View]
[Download]

Abstract: At microgrids, classical grid-regulating generators are replaced by converter-interfaced distributed generation(DG) or energy storage systems (ESSs). This causes a reduction of the total inertia of the systemand hence the microgrid voltage and frequency become more susceptible under power variations. DCmicrogrids are specially affected by this phenomena as systems with rotating inertia can not be directlyconnected. In the case of ac microgrids, an alternative is to employ strategies that emulate the behavior ofclassical generators, such as virtual synchronous machines (VSM), because they are capable of emulatingthe inertial behavior with power converters. Inspired by the operation concept of classical generatorsand VSM techniques, in this paper an autonomous virtual-capacitor control is designed for dc microgrids,which provides synthetic capacitance to the system. One of the most interesting advantages of theproposed strategy over conventional approaches is that the rate of change of voltage can be decreased bysimply varying the virtual-capacitor. In addition, the transient and steady-state behavior of the convertercan be defined independently by varying the virtual-capacitance and virtual-impedance, respectively.This feature enables the integration of generation or storage systems with different dynamics. In orderto determine the values of control parameters and delimit the stability boundaries for different points ofoperation, we analyze the stability of the proposed strategy by looking at the dominant eigenvalues ofthe small-signal state-space model. Simulation results are included to highlight the advantages of thevirtual-capacitor technique over classical strategies and to carry out the parametric stability analyses.

   Distributed Control Strategy of DC Microgrid for Islanding Mode operation
By Dong-Keun JEONG [View]
[Download]

Abstract: This paper proposes a DC-bus signaling (DBS) method for a power management in a DC microgrid. In order to autonomously increase its reliability and response speed. As opposed to a centralized power management system, which needs communication among the power sources and load, the proposed DBS method uses the common DC-bus voltage to determine proper operation and does not require communication. The DC-bus voltage is the information that signals the status of the DC-bus. In addition, DC-bus voltage bands are proposed to classify the scenarios of DC-bus conditions. The DC microgrid components operate individually to achieve the functionality of the system control in the DC-bus voltage band. This paper suggests a control strategy for power management of various independent components when in islanding mode. A microgrid test-bed is used to test the power management algorithm. The proposed power management algorithm in the islanding mode is analyzed and verified via simulation result from the proposed DC microgrid test-bed.

   EFFICIENT MANAGEMENT STRATEGY OF THE POWER CONVERTERS CONNECTED TO THE DC BUS IN A HYBRID MICROGRID OF DISTRIBUTED GENERATION
By Robert SALAS-PUENTE [View]
[Download]

Abstract: Hybrid Microgrids are currently of great interest and are considered the distribution and transmissionsystems of the future, because they enable the coexistence of the AC microgrids and DC microgrids.This paper deals with the implementation of a new power management algorithm of the powerconverters that form part of the hybrid microgrid of Distributed Generation. The hybrid microgridconsists of a DC bus, an AC bus and a connection to the public utility grid across a static switch. Themanagement algorithm executes the secondary control of the energy in the microgrid by means of aMicrogrid Central Controller. The system applies the most appropriate configuration of the powerconverters, depending on the changes of the solar irradiation, the load, the power limit and the state ofcharge of the battery bank. A communication system is used to controls each one of the microgridelements. Experimental and simulation results demonstrate that the algorithm allows to control thepower dispatch inside the microgrid properly, by performing the following tasks: (1) thecommunication among power converters, the grid operator and the intelligent loads, (2) the connectionand disconnection of the loads, (3) the control of the power exchange between the distributedgenerators and the energy storage system, (4) the compliance of the power dispatch limit set by thegrid operator, (5) the synchronization with the grid and (6) the control of the voltage at the DC bus.

   HYBRID ISOCHRONOUS-DROOP CONTROL FOR POWER MANAGEMENT IN DC MICROGRIDS
By INAM ULLAH NUTKANI [View]
[Download]

Abstract: This paper presents a new approach for generation source management in a dc microgrid, which uses a hybrid isochronous-droop (HID) control strategy to overcome the inherent drawbacks of traditional droop control and achieve a performance more towards that which can be achieved by communication-based distributed or centralized control schemes. In particular, the approach allows the number of dc sources in operation to be readily reduced at light loads, sources to be dispatched in defined priority order as load increases, and better voltage regulation to be achieved without requiring communication-based secondary control. However, since the strategy still retains the simplicity and flexibility of a traditional droop scheme, non-dispatchable and dispatchable sources controlled using traditional droop control can still be easily included into the microgrid operation. The power management and voltage regulation performance of the proposed HID scheme has been validated for different operating scenarios of the considered dc microgrid.

   Industrial DC Microgrid Analysis with Synchronous Multipoint Power Measurement Solution.
By Armands SENFELDS [View]
[Download]

Abstract: Paper is presenting application of synchronized power flow measurement system within 13 locations of DC microgrid installation in production plant with specific measurement equipment system developed for dynamic energy flow analysis. Insight into internal DC bus power exchange behavior and interconnected operation advantages with respect to energy efficiency improvement is provided. Future trends towards DC based manufacturing infrastructure are discussed. Presented results provide insight into electrical energy distribution behavior within DC microgrid system structure operated based of realistic industrial manufacturing tasks. Application of multipoint power measurement system provide real measurement data of various manufacturing technology tool load profiles that serve as important basis for future system modelling and dimensioning tasks.

   Inertia time constant design in microgrids with multiple paralleled virtual synchronous generators
By Zhenxiong WANG [View]
[Download]

Abstract: Control of power electronic generations is important in microgrids and power systems. Droop control is proposed for reasonable power allocation among different inverters. Moreover, virtual synchronous generator is proposed to improve frequency dynamics in transient state. Therefore, inertia design in VSG is necessary for integrating power electronic generations into grids. Frequency dynamic and stability are critical issues in traditional parameter design. However, power allocation for multiple virtual synchronous generations is usually ignored in transient state. This paper discuss inertia influence in paralleled virtual synchronous generators in microgrids. Transfer function model is constructed, where influence of inertia time constant is analyzed in terms of both frequency response and transient power allocation. Theoretical analysis and simulation results provide practical advice in inertia design for transient power allocation.

   Power Sharing Analysis of Power-Based Droop Control for DC Microgrids Considering Cable Impedances
By Guangyuan LIU [View]
[Download]

Abstract: This paper introduces a power-based droop controller for parallel operation of distributed energy resources in dc microgrids. This controller achieves power flow control when the bus voltage is imposed by a grid-interface converter that links the microgrid to an upstream grid. In such a case, accurate load distribution is allowed regardless of cable impedances. On the other hand, the proposed controller is able to provide bus voltage support like a classical droop controller, but precise power sharing is no longer ensured in this operation. Cable impedances taken into account, power sharing performance of power-based droop controller is analyzed and compared with that of traditional droop controller. Furthermore, the design procedure of the proposed controller is also presented herein. The simulation test based on Matlab/Simulink and the experimental test implemented on a laboratory-scale dc microgrid prototype are carried out to verify the performance of power-based droop controller.

   Pre-Synchronization Method for Grid-connection of Virtual Synchronous Generators Based Micro-grids
By Jiaqi WU [View]
[Download]

Abstract: Since the photovoltaic power generation, wind power and other distributed power supply are volatile and random, they will affect the stability of the grid frequency. In order to improve the voltage and frequency in micro-grid, the virtual synchronous generator control strategy is proposed for inverter control, which can emulate the behavior of synchronous generator, decrease rate of change of frequency and provide dynamic power support to grid. However, when virtual synchronous generators based micro-grids switch from islanded mode to grid-connected mode, inrush current may deteriorate the power quality of micro-grids and damage the device in micro-grids. This paper discusses the problem of pre-synchronization and presents a new pre-synchronization method for grid-connection of virtual synchronous generators based micro-grids. Accordingly, parameter matching between virtual inertia and capacity among virtual synchronous generators is analyzed in detail. Simulation results show the validation of the proposed method.

   Voltage Rise Mitigation and Low Voltage Ride Through Capabilities for Grid-Connected Low Voltage Microgrids
By Alexander MICALLEF [View]
[Download]

Abstract: The total real power injected by distributed renewable energy sources (RES) in the low voltage (LV) grids can cause voltage rise effects during light load scenarios. Integrating RES in microgrid architectures can result in improved power quality of the electrical grid, by avoiding the voltage rise effect from occurring and also by providing ancillary services to the grid. In this paper, a cascaded hierarchical architecture was proposed with the aim to regulate the voltage magnitude and reactive power at the point of common coupling (PCC) of the microgrid. This enables the microgrid to maximize the real power injected in the grid while avoiding the voltage rise effect. In addition, the hierarchical architecture can also support the LV grid during faults due to the added low voltage ride through capability of the microgrid.

EPE 2017 - DS2l: Micro-grids
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2017 ECCE Europe - Conference > EPE 2017 - Topic 06: Grids and Smart Grids > EPE 2017 - DS2l: Micro-grids
	[return to parent folder]

	Application of Cloud Computing in Power Routing for Clusters of Microgrids Using Oblivious Network Routing Algorithm By Kianoosh BOROOJENI	[View] [Download]
Abstract: In this paper, we propose a comprehensive co-simulation platform for the clusters of microgrids. Our proposed real-time platform considers both physical and communication layers, which can be simulated via real-time digital power system simulator (RTDS) and OMNeT++. We also propose a novel oblivious power routing scheme to prevent congestion and minimize network loss. To this end, we firstly introduce the algorithms referred to as oblivious routing-based economic dispatch. Oblivious network routing, which is applicable to large-scale networks with arbitrary topology, such as power grids, communication networks, and world-wide-web, is a metaheuristic solution to approximate network optimization problems under oblivious constraints utilizing advanced data structures and hypergraphs. Our oblivious power routing algorithms are also well suited for finding the optimal power flows through a cluster of microgrid while preventing congestion as well as minimizing the power loss. Then, we present a two-layer simulation platform which considers both communication layer and physical layer of the microgrids' cluster. In order to improve the security of communication network, we perform the computations regarding the oblivious power routing via a cloud-based network. The proposed framework can be used for further studies that deal with the real-time simulation of the clusters of microgrids. In order to validate the effectiveness of the proposed framework, we implement our proposed oblivious routing scheme on a cluster of 13 microgrids.

	Customized Power Quality Service Provided by Converter Interfaced Microgrids - Voltage Harmonics as a Study Case By Lexuan MENG	[View] [Download]
Abstract: Customers may have different power quality requirements, thus, the economic operational strategy can try to provide them with distinctive quality levels as customized service. An optimization based method is proposed in this paper to realize this functionality, offering the possibility that the customers can flexibly set and adjust their requirements. Converter interfaced distributed generators are used as compensators. Simulation results show that the proposed method is able to limit the voltage harmonics at each bus within respective limits.

	DC microgrids with energy storage systems and demand response for providing support to frequency regulation of electrical power systems By Hrvoje BASIC	[View] [Download]
Abstract: Frequency regulation of electric power systems efficiency depends on response time and on power reserves for frequency regulation. As integration of non-dispatchable renewable generation in the power system results with increased need for power reserves from fast responding power units, the idea of using aggregated DC microgrids in frequency regulation is presented. Model proposed in this work is based on using battery energy storage, combined with demand response for achieving efficient usage of battery energy storage. It is shown that large number of DC microgrids can provide sufficient energy and fast responding power, to improve efficiency of frequency regulation of electric power system.

	Design and Small-Signal Stability Analysis of a Virtual-Capacitor Control for DC Microgrids By Eneko UNAMUNO	[View] [Download]
Abstract: At microgrids, classical grid-regulating generators are replaced by converter-interfaced distributed generation(DG) or energy storage systems (ESSs). This causes a reduction of the total inertia of the systemand hence the microgrid voltage and frequency become more susceptible under power variations. DCmicrogrids are specially affected by this phenomena as systems with rotating inertia can not be directlyconnected. In the case of ac microgrids, an alternative is to employ strategies that emulate the behavior ofclassical generators, such as virtual synchronous machines (VSM), because they are capable of emulatingthe inertial behavior with power converters. Inspired by the operation concept of classical generatorsand VSM techniques, in this paper an autonomous virtual-capacitor control is designed for dc microgrids,which provides synthetic capacitance to the system. One of the most interesting advantages of theproposed strategy over conventional approaches is that the rate of change of voltage can be decreased bysimply varying the virtual-capacitor. In addition, the transient and steady-state behavior of the convertercan be defined independently by varying the virtual-capacitance and virtual-impedance, respectively.This feature enables the integration of generation or storage systems with different dynamics. In orderto determine the values of control parameters and delimit the stability boundaries for different points ofoperation, we analyze the stability of the proposed strategy by looking at the dominant eigenvalues ofthe small-signal state-space model. Simulation results are included to highlight the advantages of thevirtual-capacitor technique over classical strategies and to carry out the parametric stability analyses.

	Distributed Control Strategy of DC Microgrid for Islanding Mode operation By Dong-Keun JEONG	[View] [Download]
Abstract: This paper proposes a DC-bus signaling (DBS) method for a power management in a DC microgrid. In order to autonomously increase its reliability and response speed. As opposed to a centralized power management system, which needs communication among the power sources and load, the proposed DBS method uses the common DC-bus voltage to determine proper operation and does not require communication. The DC-bus voltage is the information that signals the status of the DC-bus. In addition, DC-bus voltage bands are proposed to classify the scenarios of DC-bus conditions. The DC microgrid components operate individually to achieve the functionality of the system control in the DC-bus voltage band. This paper suggests a control strategy for power management of various independent components when in islanding mode. A microgrid test-bed is used to test the power management algorithm. The proposed power management algorithm in the islanding mode is analyzed and verified via simulation result from the proposed DC microgrid test-bed.

	EFFICIENT MANAGEMENT STRATEGY OF THE POWER CONVERTERS CONNECTED TO THE DC BUS IN A HYBRID MICROGRID OF DISTRIBUTED GENERATION By Robert SALAS-PUENTE	[View] [Download]
Abstract: Hybrid Microgrids are currently of great interest and are considered the distribution and transmissionsystems of the future, because they enable the coexistence of the AC microgrids and DC microgrids.This paper deals with the implementation of a new power management algorithm of the powerconverters that form part of the hybrid microgrid of Distributed Generation. The hybrid microgridconsists of a DC bus, an AC bus and a connection to the public utility grid across a static switch. Themanagement algorithm executes the secondary control of the energy in the microgrid by means of aMicrogrid Central Controller. The system applies the most appropriate configuration of the powerconverters, depending on the changes of the solar irradiation, the load, the power limit and the state ofcharge of the battery bank. A communication system is used to controls each one of the microgridelements. Experimental and simulation results demonstrate that the algorithm allows to control thepower dispatch inside the microgrid properly, by performing the following tasks: (1) thecommunication among power converters, the grid operator and the intelligent loads, (2) the connectionand disconnection of the loads, (3) the control of the power exchange between the distributedgenerators and the energy storage system, (4) the compliance of the power dispatch limit set by thegrid operator, (5) the synchronization with the grid and (6) the control of the voltage at the DC bus.

	HYBRID ISOCHRONOUS-DROOP CONTROL FOR POWER MANAGEMENT IN DC MICROGRIDS By INAM ULLAH NUTKANI	[View] [Download]
Abstract: This paper presents a new approach for generation source management in a dc microgrid, which uses a hybrid isochronous-droop (HID) control strategy to overcome the inherent drawbacks of traditional droop control and achieve a performance more towards that which can be achieved by communication-based distributed or centralized control schemes. In particular, the approach allows the number of dc sources in operation to be readily reduced at light loads, sources to be dispatched in defined priority order as load increases, and better voltage regulation to be achieved without requiring communication-based secondary control. However, since the strategy still retains the simplicity and flexibility of a traditional droop scheme, non-dispatchable and dispatchable sources controlled using traditional droop control can still be easily included into the microgrid operation. The power management and voltage regulation performance of the proposed HID scheme has been validated for different operating scenarios of the considered dc microgrid.

	Industrial DC Microgrid Analysis with Synchronous Multipoint Power Measurement Solution. By Armands SENFELDS	[View] [Download]
Abstract: Paper is presenting application of synchronized power flow measurement system within 13 locations of DC microgrid installation in production plant with specific measurement equipment system developed for dynamic energy flow analysis. Insight into internal DC bus power exchange behavior and interconnected operation advantages with respect to energy efficiency improvement is provided. Future trends towards DC based manufacturing infrastructure are discussed. Presented results provide insight into electrical energy distribution behavior within DC microgrid system structure operated based of realistic industrial manufacturing tasks. Application of multipoint power measurement system provide real measurement data of various manufacturing technology tool load profiles that serve as important basis for future system modelling and dimensioning tasks.

	Inertia time constant design in microgrids with multiple paralleled virtual synchronous generators By Zhenxiong WANG	[View] [Download]
Abstract: Control of power electronic generations is important in microgrids and power systems. Droop control is proposed for reasonable power allocation among different inverters. Moreover, virtual synchronous generator is proposed to improve frequency dynamics in transient state. Therefore, inertia design in VSG is necessary for integrating power electronic generations into grids. Frequency dynamic and stability are critical issues in traditional parameter design. However, power allocation for multiple virtual synchronous generations is usually ignored in transient state. This paper discuss inertia influence in paralleled virtual synchronous generators in microgrids. Transfer function model is constructed, where influence of inertia time constant is analyzed in terms of both frequency response and transient power allocation. Theoretical analysis and simulation results provide practical advice in inertia design for transient power allocation.

	Power Sharing Analysis of Power-Based Droop Control for DC Microgrids Considering Cable Impedances By Guangyuan LIU	[View] [Download]
Abstract: This paper introduces a power-based droop controller for parallel operation of distributed energy resources in dc microgrids. This controller achieves power flow control when the bus voltage is imposed by a grid-interface converter that links the microgrid to an upstream grid. In such a case, accurate load distribution is allowed regardless of cable impedances. On the other hand, the proposed controller is able to provide bus voltage support like a classical droop controller, but precise power sharing is no longer ensured in this operation. Cable impedances taken into account, power sharing performance of power-based droop controller is analyzed and compared with that of traditional droop controller. Furthermore, the design procedure of the proposed controller is also presented herein. The simulation test based on Matlab/Simulink and the experimental test implemented on a laboratory-scale dc microgrid prototype are carried out to verify the performance of power-based droop controller.

	Pre-Synchronization Method for Grid-connection of Virtual Synchronous Generators Based Micro-grids By Jiaqi WU	[View] [Download]
Abstract: Since the photovoltaic power generation, wind power and other distributed power supply are volatile and random, they will affect the stability of the grid frequency. In order to improve the voltage and frequency in micro-grid, the virtual synchronous generator control strategy is proposed for inverter control, which can emulate the behavior of synchronous generator, decrease rate of change of frequency and provide dynamic power support to grid. However, when virtual synchronous generators based micro-grids switch from islanded mode to grid-connected mode, inrush current may deteriorate the power quality of micro-grids and damage the device in micro-grids. This paper discusses the problem of pre-synchronization and presents a new pre-synchronization method for grid-connection of virtual synchronous generators based micro-grids. Accordingly, parameter matching between virtual inertia and capacity among virtual synchronous generators is analyzed in detail. Simulation results show the validation of the proposed method.

	Voltage Rise Mitigation and Low Voltage Ride Through Capabilities for Grid-Connected Low Voltage Microgrids By Alexander MICALLEF	[View] [Download]
Abstract: The total real power injected by distributed renewable energy sources (RES) in the low voltage (LV) grids can cause voltage rise effects during light load scenarios. Integrating RES in microgrid architectures can result in improved power quality of the electrical grid, by avoiding the voltage rise effect from occurring and also by providing ancillary services to the grid. In this paper, a cascaded hierarchical architecture was proposed with the aim to regulate the voltage magnitude and reactive power at the point of common coupling (PCC) of the microgrid. This enables the microgrid to maximize the real power injected in the grid while avoiding the voltage rise effect. In addition, the hierarchical architecture can also support the LV grid during faults due to the added low voltage ride through capability of the microgrid.