Distributed Battery Storage Units for Overload Prevention in an Islanded Microgrid

In an islanded microgrid, the load demand must be met by the distrusted generators (DGs) connected to it. Usually this can satisfactorily. However load growth increases, especially the peak load. In such a case, more DGs are to be connected to cater to the load growth. Alternatively if the overloading conditions occur infrequently or remain for shorter periods, storage units can be employed. In this paper, distributed battery storage units (BSUs) are employed for the overloading prevention in an islanded microgrid. It has been assumed that the microgrid only contains inertial DGs and ordinarily they share power in a frequency droop control. When an overloading is detected, the BSUs come on line and share power with the DGs using the same frequency droop control. The detection of overloading condition and when overload has been removed are crucial for this operation. An algorithm is proposed for this purpose. Through simulation studies, it has been demonstrated that the BSUs can be switched on and off seamlessly

Overload Prevention in an Autonomous Microgrid using Battery Storage Units

A new control strategy for smooth transition of a battery storage unit (BSU) is proposed in this paper to prevent overloading in an autonomous hybrid microgrid. The BSU is controlled to come online to prevent overloading to the distributed generators (DGs) in the autonomous microgrid and to go offline when the load demand is less than the total rating of the DGs in the microgrid. The microgrid can contain either inertial DG or non–inertial DGs, which are controlled in a frequency droop. The sensing of switching on and switching off of the BSU depends on the frequency signal, which is developed in the paper. The proposed strategy is validated through PSCAD/EMTDC simulation studies

Multi-level supervisory emergency control for operation of remote area microgrid clusters

Remote and regional areas are usually supplied by isolated and self-sufficient electricity systems, which are called as microgrids (MGs). To reduce the overall cost of electricity production, MGs rely on non-dispatchable renewable sources. Emergencies such as overloading or excessive generation by renewable sources can result in a substantial voltage or frequency deviation in MGs. This paper presents a supervisory controller for such emergencies. The key idea is to remedy the emergencies by optimal internal or external support. A multi-level controller with soft, intermedial and hard actions is proposed. The soft actions include the adjustment of the droop parameters of the sources and the controlling of the charge/discharge of energy storages. The intermedial action is exchanging power with neighboring MGs, which is highly probable in large remote areas. As the last remedying resort, curtailing loads or renewable sources are assumed as hard actions. The proposed controller employs an optimization technique consisting of certain objectives such as reducing power loss in the tie-lines amongst MGs and the dependency of an MG to other MGs, as well as enhancing the contribution of renewable sources in electricity generation. Minimization of the fuel consumption and emissions of conventional generators, along with frequency and voltage deviation, is the other desired objectives. The performance of the proposal is evaluated by several numerical analyses in MATLAB®

Integration of Wind Energy Conversion System with Microgrid and Utility

An integration of a Permanent Magnetic Synchronous Generator (PMSG) based Wind Energy ConversionSystem (WECS) into a microgrid is discussed in this paper. A back-to-back Voltage Source Converter (VSC) is employed for the power conversion from the PMSG to the AC grid. The Sinusoidal Pulse Width Modulation (SPWM) technique is adopted for the Wind-side Converter (WSC), while for the Gridside Converter (GSC), Space Vector Pulse Width Modulation (SVPWM) is applied. A Maximum Power Point Track (MPPT) control scheme called the Optimal Power Control (OPC) is used for the WSC to draw the maximum power from wind energy. The DC voltage of the back-to-back converter is controlled by the GSC. The microgrid contains a microturbine and a diesel generator, along with loads. The power flow from the WECS to the microgrid is controlled through another back-to-back converter. Four different cases are studied to validate the performance of the WECS integration with the microgrid system

Proposing a New Algorithm for Defining the Shortest Distance among ZigBee-Based Communication Devices in Microgrids

To improve the controllability within Future microgrids, a communication network needs to be available to provide data transfer within the MG. Wireless technologies such as ZigBee seem to be a good alternative for data transfer within MGs mainly due to low cost, more flexibility and acceptable data transfer rate. In such networks ZigBee-based repeaters are required to strengthen the communication signals if the DG units are scattered over a vast area. This paper mainly discusses on the algorithms required for defining the shortest distance between the DG units and the MG central controller. Different methods are discussed and a new algorithm is presented. Through the numerical analyses, it is demonstrated that the proposed method leads to a high reduction in the number of repeaters than other conventional algorithms

Techniques for a Wind Energy System Integration with an Islanded Microgrid

This paper presents two different techniques of a wind energy conversion system (WECS) integration with an islanded microgrid (MG). The islanded microgrid operates in a frequency droop control where its frequency can vary around 50 Hz. The permanent magnet synchronous generator (PMSG) based variable speed WECS is considered, which converts wind energy to a low frequency ac power. Therefore it needs to be connected to the microgrid through a back to back (B2B) converter system. One way of interconnection is to synchronize the MG side converter with the MG bus at which it is connected. In this case, this converter runs at the MG frequency. The other approach is to bring back the MG frequency to 50 Hz using the isochronization concept. In this case, the MG side converter operates at 50 Hz. Both these techniques are developed in this paper. The proposed techniques are validated through extensive PSCAD/EMTDC simulation studies

Developing the ZigBee Based Data Payload Coding for Data Communication in Microgrids

A data coding is presented in this paper for ZigBee-based wireless data communication system for future microgrids. It is assumed that each microgrid has a central controller and each distributed generation unit in the microgrid has a local controller. The communication system is responsible for transmitting and receiving data amongst these controllers. This communication system is based on ZigBee technology, which has low cost and low power consumption. The required data to be transferred are defined and a suitable coding is also proposed. Finally, the number of transmitted symbols and the processing time delay of the proposed data coding are numerically analyzed

The energy-water nexus: Renewable energy and water desalination

The essential connection between energy and water, also defined as the energy-water nexus, has been recognized by scientists and policy makers worldwide. Integrated solutions and policies that consider both energy and water aspects into future planning have been developing at a fast pace. In this paper, we review the state of the art of the energy-water nexus, with particular focus on the integration between renewable energy and desalination technologies. We also model the integration of reverse osmosis (RO) desalination and solar photovoltaics in an edge-of-grid coastal town in Western Australia. The current literature agrees on the sustainable use of renewable energy sources to improve the water-energy nexus in the context of water desalination. Although the integration of solar and wind energy with desalination technologies is a mature and well-proven solution at both small and large scales, the intermittency and fluctuating nature of wind and solar power still constitute the main technical challenge that has limited the diffusion of renewable energy powered desalination on a large scale. Several successful applications of renewable energy powered desalination in remote, off the grid, locations have tackled the issue of power intermittency by the use of batteries and diesel generators. Such systems often couple reverse osmosis desalination with solar photovoltaic energy. Large desalination plants have been successfully connected to wind farms and grid electricity to secure uninterrupted plant operations, thus meeting water targets in large-scale systems. Our review identifies a knowledge gap in the integration of decentralized energy systems, e.g. rooftop solar photovoltaic, with small scale RO desalination. Such configuration would benefit those regional towns that have historically suffered from weak and unreliable connections to the electricity grid, thus helping them secure both their energy and water requirements. The modelling exercise on a renewable energy powered RO plant in an edge-of-grid town in Western Australia has identified an operating strategy that maximizes the renewable energy fraction and secures the annual supply of water. The system involves operating the RO unit for six months of the year at a daily variable load and integrating solar energy with grid electricity. Careful evaluation of the RO performance under such operating conditions is necessary to ensure a safe and reliable water treatment process. A niche in the literature of the energy-water nexus has been identified in the integration of rooftop solar photovoltaic, grid electricity and desalination technologies applied in a regional context. A future study will consider the rollout of rooftop solar photovoltaic installations across the whole town, thus enabling the active engagement of the community by integrating the households’ energy demand response patterns to the operations of both rooftop photovoltaics and the desalination unit

The energy-water nexus: Renewable energy and water desalination

The essential connection between energy and water, also defined as the energy-water nexus, has been recognized by scientists and policy makers worldwide. Integrated solutions and policies that consider both energy and water aspects into future planning have been developing at a fast pace. In this paper, we review the state of the art of the energy-water nexus, with particular focus on the integration between renewable energy and desalination technologies. We also model the integration of reverse osmosis (RO) desalination and solar photovoltaics in an edge-of-grid coastal town in Western Australia. The current literature agrees on the sustainable use of renewable energy sources to improve the water-energy nexus in the context of water desalination. Although the integration of solar and wind energy with desalination technologies is a mature and well-proven solution at both small and large scales, the intermittency and fluctuating nature of wind and solar power still constitute the main technical challenge that has limited the diffusion of renewable energy powered desalination on a large scale. Several successful applications of renewable energy powered desalination in remote, off the grid, locations have tackled the issue of power intermittency by the use of batteries and diesel generators. Such systems often couple reverse osmosis desalination with solar photovoltaic energy. Large desalination plants have been successfully connected to wind farms and grid electricity to secure uninterrupted plant operations, thus meeting water targets in large-scale systems. Our review identifies a knowledge gap in the integration of decentralized energy systems, e.g. rooftop solar photovoltaic, with small scale RO desalination. Such configuration would benefit those regional towns that have historically suffered from weak and unreliable connections to the electricity grid, thus helping them secure both their energy and water requirements. The modelling exercise on a renewable energy powered RO plant in an edge-of-grid town in Western Australia has identified an operating strategy that maximizes the renewable energy fraction and secures the annual supply of water. The system involves operating the RO unit for six months of the year at a daily variable load and integrating solar energy with grid electricity. Careful evaluation of the RO performance under such operating conditions is necessary to ensure a safe and reliable water treatment process. A niche in the literature of the energy-water nexus has been identified in the integration of rooftop solar photovoltaic, grid electricity and desalination technologies applied in a regional context. A future study will consider the rollout of rooftop solar photovoltaic installations across the whole town, thus enabling the active engagement of the community by integrating the households’ energy demand response patterns to the operations of both rooftop photovoltaics and the desalination unit

Integrated spatial multiplexing of heralded single photon sources

The non-deterministic nature of photon sources is a key limitation for single photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon correlated photon pair sources, demonstrating a 62.4% increase in the heralded single photon output without an increase in unwanted multi-pair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two photon interference, required at the core of optical quantum computing and quantum communication protocols.Comment: 10 pages, 3 figures, comments welcom