Distributed Generation Research Papers - Academia.edu (original) (raw)

This study presents techno-economic analysis that compares the isolated and grid-connected Micro-hydropower plant (MHP) for sustainable rural electrification. The critical factors that need to be considered in order to analyze the MHP are... more

This study presents techno-economic analysis that compares the isolated and grid-connected Micro-hydropower plant (MHP) for sustainable rural electrification. The critical factors that need to be considered in order to analyze the MHP are characterized, and the risk analysis is performed by evaluating the probability of the Net Present Value (NPV), Internal Rate of Return (IRR), Benefit to Cost ratio (B/C), and Profitability. Furthermore, technical analysis is done by performing the load flow analysis of the system for different case scenario. It is found that the project is not feasible even for private investment under subsidy rate. However, the profitability of the grid-connected system depends upon various factors such as tariff rate, load factor, amount of load, power trading with utility.

The reconfiguration of a power distribution system, by exchanging the functional links between its elements, represents one of the most important procedures to improve the performance in the operation of a distribution system. The... more

The reconfiguration of a power distribution system, by exchanging the functional links between its elements, represents one of the most important procedures to improve the performance in the operation of a distribution system. The optimization through reconfiguration (or optimal reconfiguration) of a power distribution system is not a new problem but still represents a difficult one and is specified in some strategies for smart grids. The paper addresses this problem as a single objective one, where, as main criterion, active power losses have been chosen. There is no unique acceptance regarding which approach (based on heuristics, meta-heuristics, genetic algorithms, etc.) is the most proper to use in order to solve this problem. The most important thing is how the specific knowledge of the problem domain is used and modeled in the implementation. Moreover, the indices which can quantify the quality of a reconfiguration method consist in runtime and the obtained solution and these indices can be confirmed only by experimental results. In order to solve the problem (to search and find the optimal solution) an original genetic algorithm based on connected graphs is proposed. Comparative tests performed on some test systems demonstrated the accuracy and the promptness of the proposed algorithm.

A generalized macroscopic representation of electrical steels used in transformer manufacturing industry is developed. The proposed representation is specifically formulated for integration in the finite element method. Usage of the... more

A generalized macroscopic representation of electrical steels used in transformer manufacturing industry is developed. The proposed representation is specifically formulated for integration in the finite element method. Usage of the specific technique enables the accurate evaluation of electromagnetic field distribution of transformer cores under heavily saturated conditions. Advantages over conventional techniques include numerical stability, numerical accuracy, and reduction of iterations of the Newton–Raphson method.

Load balancing functionalities are crucial for best Grid performance and utilization. Accordingly,this paper presents a new meta-scheduling method called TunSys. It is inspired from the natural phenomenon of heat propagation and thermal... more

Load balancing functionalities are crucial for best Grid performance and utilization. Accordingly,this paper presents a new meta-scheduling method called TunSys. It is inspired from the natural phenomenon of heat propagation and thermal equilibrium. TunSys is based on a Grid polyhedron model with a spherical like structure used to ensure load balancing through a local neighborhood propagation strategy. Furthermore, experimental results compared to FCFS, DGA and HGA show encouraging results in terms of system performance and scalability and in terms of load balancing efficiency.

In this paper a robust three-dimensional (3D) finite element (FE) anisotropy model is introduced based on a particular scalar potential formulation. The specific 3D FE model is suitable for the accurate evaluation of the peak flux density... more

In this paper a robust three-dimensional (3D) finite element (FE) anisotropy model is introduced based on a particular scalar potential formulation. The specific 3D FE model is suitable for the accurate evaluation of the peak flux density distribution and no load loss of one-phase and three-phase wound core distribution transformers. The accuracy of the proposed 3D FE anisotropy model is validated by local flux density and no load loss measurements.

In recent years, sustainable and clean renewable energy resources are widely used instead of fossil fuel energy resources in electrical energy generation systems. Especially, wind and solar energy conversion systems are utilized together... more

In recent years, sustainable and clean renewable energy resources are widely used instead of fossil fuel energy resources in electrical energy generation systems. Especially, wind and solar energy conversion systems are utilized together in stand-alone systems. In this study, reliability analysis of a hybrid system installed in Davutpasa Campus of Yildiz Technical University is investigated. The system includes a wind turbine, PV panels, a hybrid charge regulator, a MPPT charge controller, an inverter, battery group and loads. Reliability indexes are calculated for analyzed system. The obtained results are examined and presented in this paper.

The new energy source utilization and development, gradual rise of distributed power grid miniaturization, intelligence, control has become a trend. In order to make microgrid reliable and efficiently run, control technology of microgrid... more

The new energy source utilization and development, gradual rise of distributed power grid miniaturization, intelligence, control has become a trend. In order to make microgrid reliable and efficiently run, control technology of microgrid has become a top priority and an inverter as microgrid basic unit, its control has become the most important part in microgrid. In this paper, three inverters are operated in parallel using an P-V/Q-F droop control is investigated. Mathematical model of three phase inverter with LC filter is derived, which is based on the voltage and current dual control loop. Parallel control strategy based on P-V/Q-F droop control, does not require a real time communications between the inverters and more suitable for microgrid applications. To verify the feasibility and validity of the droop control scheme, simulation is done in Matlab/Simulink and results indicate droop control has significant effect on power sharing and balancing the voltage magnitude, frequency.

Design of control strategies for Distributed generation systems is very important to achieve smoother transition between the grid connected and islanding modes of operation. The transition between these two modes of operation should be... more

Design of control strategies for Distributed generation systems is very important to achieve smoother transition between the grid connected and islanding modes of operation. The transition between these two modes of operation should be seamless, without any severe transients during the changeover. In this paper, two different control strategies namely inverter output current control and indirect grid current control for the seamless transfer between the modes of operation has been explored for the suitability. The design and analysis of the cascaded control loops based on Proportional Integral (PI) controller has been dealt in detail for both inverter output current control and indirect grid current control strategy. Control parameters are designed using the control system toolbox in MATLAB. A 10kW grid connected microgrid system has been designed and simulated in MATLAB/Simulink and the results are presented under grid connected operation, islanding operation and the transition between the modes considering fault condition in the grid side. The simulation studies are carried out using both the control strategies and the results are presented to validate the design methodology.

Looking back from the year 2050, this article provides a retrospective snapshot of the U.S. electric system - how it looked in 2015, how it had changed so much by 2030, and how the drivers of change that were rampant and seemed so... more

Looking back from the year 2050, this article provides a retrospective snapshot of the U.S. electric system - how it looked in 2015, how it had changed so much by 2030, and how the drivers of change that were rampant and seemed so disruptive during the twenty-teens converged eventually to form a coherent, well-functioning, new electric system paradigm.

— Due to transmission system constraints and load growth and in order to properly supply the consumers, Distributed Generation (DG) penetration in power systems has been increased. Therefore, DG placement is one of the major topics in... more

— Due to transmission system constraints and load growth and in order to properly supply the consumers, Distributed Generation (DG) penetration in power systems has been increased. Therefore, DG placement is one of the major topics in power system studies in recent years. In order to have a better voltage profile and minimize the loss in distribution networks, optimal allocation of DGs must be noticed. The optimal placement of DGs reduces the operational cost and network losses and improves the power quality. Different methods have been developed by researchers to determine the optimum location and size of the DGs. These solutions are based on either analytical tools or heuristic global optimization methods. In this paper, Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Harmony Search Algorithm (HSA) are used to find the optimal location and operating point of DGs considering the voltage profile improvement and loss reduction. The optimization procedure is applied to a 682-bus radial distribution network of Iran. This distribution network has a poor voltage profile because of supplying outland villages and feeding lots of agriculture water pumps. Besides that, these issues result in an increase in power loss.. The basis of the loss calculation and voltage profile determination is the load flow studies. The forward-backward sweep load flow method is used in this paper. The simulation results show the importance of the application of DGs in Iranian distribution networks.

Plug and play solar photovoltaic (PV) systems are affordable, easy to install and portable grid-tied solar electric systems, which can be purchased and installed by an average prosumer (producing consumer). The combination of recent... more

Plug and play solar photovoltaic (PV) systems are affordable, easy to install and portable grid-tied solar electric systems, which can be purchased and installed by an average prosumer (producing consumer). The combination of recent technical/safety analysis and trends in other advanced industrialized nations, indicate that U.S. electrical regulations may allow plug and play solar in the future. Such a shift in regulations could radically alter the current PV market. This study provides an estimate of this new U.S. market for plug and play PV systems if such regulations are updated by investigating personal financial decision making for Americans. The potential savings for the prosumer are mapped for the U.S. over a range of scenarios. The results show the total potential U.S. market of over 57 GW, which represents an opportunity for sales for retailers from 14.3–14.3–14.3–71.7 billion depending on the capital cost of plug and play solar systems ($0.25-$1.25/W). These systems would generate ∼108,417,000 MWh/year, which is 4 times the electricity generated from U.S. solar in 2015. This distributed solar energy would provide prosumers approximately $13 billion/year in cost savings, which would be expected to increase by about 3% per year over the year lifetime of the systems.

MICROGRID is one of the new emerging power distribution infrastructures with prominent potentials in modern civilization. The concept of microgrid has the potential to solve major problems arising from distributed generation in... more

MICROGRID is one of the new emerging power distribution infrastructures with prominent potentials in modern civilization. The concept of microgrid has the potential to solve major problems arising from distributed generation in distribution systems. Microgrid is defined as the cluster of multiple distributed generators (DGs) that supply electrical energy to consumers without any shortage. The realization of demand response, efficient energy management, high capability of Distributed Energy Resources (DERs), and high-reliability of electricity delivery leads to a successful microgrid. In a microgrid network, total maximum load matches to the generated power. Large growth in electricity consumption and rise in number of sensitive or critical loads leads to increase in demand of electricity in daily life. A proper control strategy should be implemented for a successful operation of a microgrid and in utilization of renewable energies such as PV arrays, hydro, thermal and wind turbines. In this technical context an overview of microgrid has been carried out based on the reports from the literature present in past two decades.

：In autonomous microgrids frequency regulation (FR) is a critical issue, especially with a high level of penetration of the photovoltaic (PV) generation. In this study, a novel virtual synchronous generator (VSG) control for PV generation... more

：In autonomous microgrids frequency regulation (FR) is a critical issue, especially with a high level of penetration of the photovoltaic (PV) generation. In this study, a novel virtual synchronous generator (VSG) control for PV generation was introduced to provide frequency support without energy storage. PV generation reserve a part of the active power in accordance with the pre-defined power versus voltage curve. Based on the similarities of the synchronous generator power-angle characteristic curve and the PV array characteristic curve, PV voltage Vpv can be analogized to the power angle δ. An emulated governor (droop control) and the swing equation control is designed and applied to the DC-DC converter. PV voltage deviation is subsequently generated and the pre-defined power versus voltage curve is modified to provide the primary frequency and inertia support. A simulation model of an autonomous microgrid with PV, storage, and diesel generator was built. The feasibility and effectiveness of the proposed VSG strategy are examined under different operating conditions.

Increasing penetration of distributed or dispersed generation (DG) is transforming low voltage feeders from passive to active, increasing the complexity of ensuring operating conditions comply with regulatory standards for voltage... more

Increasing penetration of distributed or dispersed generation (DG) is transforming low voltage feeders from passive to active, increasing the complexity of ensuring operating conditions comply with regulatory standards for voltage magnitude. The Herman-Beta (HB) transform meets the growing need for tools that accurately replicate passive and active feeder systems with new types of loads and DG. The robust analytic-probabilistic calculation already adopted as the standard for voltage drop calculations for passive feeders in South Africa and Kenya has been modified to calculate voltage variation in active feeders with DG. This paper extends the modified algorithms to a new C# platform, providing a stand-alone open-source program. The input interface enables efficient setting up and editing of all feeders, including multiple branches and up to 1000 nodes. The feeder performance output includes a voltage profile. Examples illustrate how the program simplifies planning and operational studies of practical distribution systems.

This paper analyses the technical impact of Distributed Generation on the Medium Voltage (MV) and Low Voltage (LV) Networks using ERACS specifically considering the changes in voltage profiles, real and reactive power flows caused by the... more

This paper analyses the technical impact of Distributed Generation on the Medium Voltage (MV) and Low Voltage (LV) Networks using ERACS specifically considering the changes in voltage profiles, real and reactive power flows caused by the introduction of small scale distributed generators(SSDGs) both at the medium voltage (MV) and low voltage (LV) levels of distribution networks.

A grid computing environment provides a type of distributed computation that is unique because it is not centrally managed and it has the capability to connect heterogeneous resources. A grid system provides location-independent access to... more

A grid computing environment provides a type of distributed computation that is unique because it is not centrally managed and it has the capability to connect heterogeneous resources. A grid system provides location-independent access to the resources and services of geographically distributed machines. An essential ingredient for supporting location-independent computations is the ability to discover resources that have been requested by the users. Because the number of grid users can increase and the grid environment is continuously changing, a scheduler that can discover decentralized resources is needed. Grid resource scheduling is considered to be a complicated, NP-hard problem because of the distribution of resources, the changing conditions of resources, and the unreliability of infrastructure communication. Various artificial intelligence algorithms have been proposed for scheduling tasks in a computational grid. This paper uses the imperialist competition algorithm (ICA) to address the problem of independent task scheduling in a grid environment, with the aim of reducing the makespan. Experimental results compare ICA with other algorithms and illustrate that ICA finds a shorter makespan relative to the others. Moreover, it converges quickly, finding its optimum solution in less time than the other algorithms.

— A combined savonius and darrieus vertical axis wind turbine would have many advantages over an individual savonius or darrieus rotor. A savonius produces high torque which would be useful in self-starting and darrieus rotor having a... more

— A combined savonius and darrieus vertical axis wind turbine would have many advantages over an individual savonius or darrieus rotor. A savonius produces high torque which would be useful in self-starting and darrieus rotor having a high tip speed ratio useful for electrical generation. However research on combined savonius and darrieus rotors is very scarce. This developed a two bucket savonius rotor and placed it on the central shaft of a traditional darrieus. Though the tip speed ratio is a still a little low for use as an electrical generator, the research demonstrated a simple way to enable a darrieus VAWT to be self-starting and achieve higher efficiencies. Historically VAWTs cost more to operate and maintain than HAWTs Finally, traditional Darrieus rotors are not self-starting under most of wind conditions and manufacture of their blades is a challenge because of the complex shape which adds expense to the turbine. However, evidence shows that a Darrieus turbine using fixed geometry symmetrical airfoils can self-start in the field during atmospheric gusting it was suggested that using a Darrieus blade together with a Savonius blade has better performance than using them individually according to self-start ability and efficiency of the turbine. Using a counter rotating wind turbine with a freely rotating generator can produce higher amounts of power than common wind generators.

Following requirements of the Energy Policy Act of 2005, most U.S. states require utility companies to adopt interconnection and net metering policies, allowing customers to become prosumers who both consume and produce electricity,... more

Following requirements of the Energy Policy Act of 2005, most U.S. states require utility companies to adopt interconnection and net metering policies, allowing customers to become prosumers who both consume and produce electricity, generating electricity using distributed renewable energy technologies, connecting to the existing electric utility grid, and receiving compensation for excess electricity generation. This paper reviews existing interconnection and net metering policies instituted by investor owned utilities (IOUs) across the U.S., specifically focused on policies regulating small scale, residential or Tier 1 (a term used to indicate policies applicable to smaller scale rather than larger scale, although the size at which DG systems are classified as either Tier 1 or higher tiers varies by utility) installations. Publicly available data from each IOU reveal inconsistencies in interconnection and net metering policies, within states and even within individual companies. In addition, accurate information is often unavailable to consumers. Perhaps most importantly, results suggest that compensation for excess distributed generation is often obscured in utility policy. The results of this study provide important insight into interconnection and net metering policies for distributed renewable energy generation, as states and utilities continue to modify interconnection and net metering policies in response to increased adoption of distributed renewable energy systems.

Several conventional and artificial algorithms have been used to find the location of distributed generation DG in power systems. Particle swarm optimization PSO is one of the most used, but some convergence problems have been reported... more

Several conventional and artificial algorithms have been used to find the location of distributed generation DG in power systems. Particle swarm optimization PSO is one of the
most used, but some convergence problems have been reported in literature. In this paper, the use of the metaheuristic Bat-inspired algorithm BA is proposed to place different number and capacities of DG for meshed and radial distribution networks. The aim of this work was to solve an optimization problem defined as minimization of power losses installing generators at load busses. A binary combination is included to represent the states and locations of generators. The search for the minimum value is achieved using the movement of bats at iterations, considering location and size. IEEE 14-bus, IEEE 30-bus and IEEE 33-node systems were used to test the metaheuristic techniques using five cases of power increasing considering from 1 to 5 generators. Results showed that bat algorithm is a good method to locate and find size of DG and maintain convergence to improve power losses. Voltage level and power losses were improved for all cases maintaining consistent results.

The use of distributed solar photovoltaic (PV) systems is growing more common as solar energy conversion efficiencies increase while costs decrease. Thus, PV system installations are increasing in non-optimal locations such as those... more

The use of distributed solar photovoltaic (PV) systems is growing more common as solar energy conversion efficiencies increase while costs decrease. Thus, PV system installations are increasing in non-optimal locations such as those potentially shaded with trees. Tree-related shading can cause a significant power loss and an increasing collection of laws have been enacted and are under development to protect the right of PV owners to solar access. This paper provides a new method to predict the shading losses for a given tree species, orientation to a PV array, and geographic location using existing free tools in order to assist in the prevention of conflicts by creating an environment where PV systems and trees can coexist while maximizing PV performance. This methodology is applied to a case study in the Midwest US. Tree growth characteristics including height, crown width, and growth rate were investigated. Minimum planting distances were quantified based on tree species and orientation of planting with respect to the PV system and conclusions were drawn from the results. This novel open low-cost method to predict and prevent tree shading from negatively impacting the performance of roof-mounted PV systems assists in planning of technical design.

—The power distribution feeder reconfiguration and optimum placement of distributed generation are two main methods to minimize the active power loss in radial distribution systems. The robustness of the radial distribution system can be... more

—The power distribution feeder reconfiguration and optimum placement of distributed generation are two main methods to minimize the active power loss in radial distribution systems. The robustness of the radial distribution system can be improved by simultaneous manipulation of both optimal DG placement and feeder reconfiguration. In this paper, a novel technique is proposed to minimize the power loss with the simultaneous use of feeder reconfiguration and placement of distributed generation. In general, an electrical power network economics primarily relies on the conductor line losses. Hence in this proposed study, the feeder reconfiguration and finding of desirable bus location and operating power of distributed generation is concurrently modeled as an optimization problem for minimizing the real power loss with subject to all operating equality and inequality constraints. This optimization problem is solved with the guide of unified particle swarm optimization algorithm. The system power loss is handled as the cost function for each particle in a swarm. The proposed method is applied to both IEEE 33-bus and IEEE 69-bus radial distribution systems. The prosperous solutions achieved from the simulation studies manifest that the high level of system loss reduction and desirable bus voltage profile, when analyzed against the system with reconfiguration, and the system with DG.

Solar photovoltaic (PV) technology can provide sustainable power for the growing global population in cities, but it demands considerable land area. This is a challenge for densely populated cities. However, the stranded assets of... more

Solar photovoltaic (PV) technology can provide sustainable power for the growing global population in cities, but it demands considerable land area. This is a challenge for densely populated cities. However, the stranded assets of non-productive parking lots areas can be converted to solar farms with PV canopies, enabling sustainable electricity generation while preserving their function to park automobiles. This study provides a method for determining the technical and economic potential for converting a national scale retail company's parking lot area to a solar farm. First, the parking lot area for the company is determined and divided into zones based upon solar flux using virtual maps. Then the potential PV yield in each zone is calculated. A sensitivity analysis is performed on the price per unit power installed, solar energy production as a proxy for conversion efficiency, electricity rates and revenue earned per unit area. To demonstrate this method, analysis of Walmart Supercenters, USA is presented as a case study. The results show solar canopies for parking lot areas are a profitable as well a responsible step in most locations and there is significant potential for sustainable energy deployment in cities by other similar retailers using solar PV canopies.

Micro Hydro Power scheme uses thyristor based Electronic Load Controller (ELC) for speed regulation of synchronous generator. ELC mainly controls the ballast load which uses water heater where excess energy is dissipated. The proposed ELC... more

Micro Hydro Power scheme uses thyristor based Electronic Load Controller (ELC) for speed regulation of synchronous generator. ELC mainly controls the ballast load which uses water heater where excess energy is dissipated. The proposed ELC consists of a three phase current controlled Voltage Source Converter (VSC) which is connected in shunt with the system the reference current generation technique utilizes vector controlled approach based on synchronously rotating d-q theory. The DC site of the VSC consists of a battery which thus also acts as a source of real power generation. The VSC is also so developed that it also compensates for load reactive demand. An Electronic Load Controller (ELC) based on STATCOM principle is connected in shunt with the system. Vector control scheme for reference current generation technique of STATCOM is developed. The major objectives in a standalone system are regulation of frequency and voltage. A battery bank is used on the dc side of ELC, thus enabling it for active power control and thus regulating the frequency. This improved ELC also performs other functions such as voltage regulation and reactive power compensation. Besides these simulation model, this project also deals with the hardware fabrication for frequency control of single phase synchronous generator. Arduino programming generates the required switching pulses for the gate of MOSFET respective to change in load. The signal input to the arduino is generated from the sine to square wave convertor after step down the generated voltage. Thus the proposed scheme is seen much superior in its characteristics of frequency and voltage regulation as well as reactive power compensator.

El uso de la generación distribuida con fuentes de energías renovables no convencionales y de sistemas de almacenamiento de energía ha propiciado el cambio de los sistemas tradicionales de distribución de energía hacia las microrredes... more

El uso de la generación distribuida con fuentes de energías renovables no convencionales y de sistemas de almacenamiento de energía ha propiciado el cambio de los sistemas tradicionales de distribución de energía hacia las microrredes eléctricas. La idea principal de esta investigación, es analizar el comportamiento de una microrred por medio de su modelado y simulación usando el programa computacional OpenDSS. Para ello, se modeló el sistema de prueba IEEE de 13 nodos modificado por medio de la ubicación de sistemas de almacenamiento de energía y plantas de generación -solar, eólica y diésel- distribuidas en diferentes puntos de la red de distribución. Lo anterior permite analizar las potencialidades de este software, así como las técnicas de modelado necesarias para su óptimo funcionamiento. Se verifica que el sistema, trabajando como microrred, mejora la eficiencia de la red de distribución en 51.5%.

The U.S. electrical grid, the largest and most complex man-made system in the world, is highly vulnerable to three types of external threats: 1) natural disasters, 2) intentional physical attacks, and 3) cyber-attacks. The technical... more

The U.S. electrical grid, the largest and most complex man-made system in the world, is highly vulnerable to three types of external threats: 1) natural disasters, 2) intentional physical attacks, and 3) cyber-attacks. The technical community has recommended hardening the grid to make it more resilient to attack by using distributed generation and microgrids. Solar photovoltaic (PV) systems are an ideal distributed generation technology to provide power for such microgrids. However, both the deployment velocity and the policy of how to implement such technical solutions have been given far less attention than would be normally considered adequate for a national security risk. To address this threat, this paper reviews the technical and economic viability of utilizing defense contracting for the beginning of a national transition to distributed generation in the U.S. First, the technical scale of electrical demand and the solar PV system necessary is analyzed in detail to meet the first level of strategic importance: the U.S. military. The results found that about 17GW of PV would be needed to fortify the U.S. military domestically. The current domestic geographic deployment of microgrid installations in the critical U.S. defense infrastructure were reviewed and compared to historical grid failures and existing and planned PV installations to mitigate that risk. The results showed a minimal number of military bases have introduced solar PV systems, leaving large parts of the Department of Defense electrical infrastructure vulnerable to attack. To rectify this situation, the technical skills of the top 20 U.S. defense contractors is reviewed and analyzed for a potential contracting transition to grid fortification. Overall the results indicate that a fortified U.S. military grid made up of PV-powered microgrids is technically feasible, within current contractors skill sets and economically viable. Policy recommendations are made to accelerate U.S. military grid fortification.

A smart grid will require, to greater or lesser degrees, advanced tools for planning and operation, broadly accepted communications platforms, smart sensors and controls, and real-time pricing. The smart grid has been described as... more

A smart grid will require, to greater or lesser degrees, advanced tools for planning and operation, broadly accepted communications platforms, smart sensors and controls, and real-time pricing. The smart grid has been described as something of an ecosystem with constantly communication, proactive, and virtually self-aware. The use of smart grid has a lot of economical and environmental advantages; however it has a downside of instability and unpredictability introduced by distributed generation (DG) from renewable energy into the public electric systems. Variable energies such as solar and wind power have a lack of stability and to avoid short-term fluctuations in power supplied to the grid, a local storage subsystem could be used to provide higher quality and stability in the fed energy. Energy storage systems (ESSs) would be a facilitator of smart grid deployment and a " small amount " of storage would have a " great impact " on the future power grid. The smart grid, with its various superior communications and control features, would make it possible to integrate the potential application of widely dispersed battery storage systems as well other ESSs. This work deals with a detailed updated review on available ESSs applications in future smart power grids. It also highlights latest projects carried out on different ESSs throughout all around the world.

High demand for photovoltaic (PV), battery, and small-scale combined heat and power (CHP) technologies are driving a virtuous cycle of technological improvements and cost reductions in off-grid electric systems that increasingly compete... more

High demand for photovoltaic (PV), battery, and small-scale combined heat and power (CHP) technologies are driving a virtuous cycle of technological improvements and cost reductions in off-grid electric systems that increasingly compete with the grid market. Using a case study in the Upper Peninsula of Michigan, this paper quantifies the economic viability of off-grid PV+battery+CHP adoption and evaluates potential implications for grid-based utility models. The analysis shows that already some households could save money by switching to a solar hybrid off-grid system in comparison to the effective electric rates they are currently paying. Across the region by 2020, 92% of seasonal households and ~75% of year-round households are projected to meet electricity demands with lower costs. Furthermore, ~65% of all Upper Peninsula single-family owner-occupied households will both meet grid parity and be able to afford the systems by 2020. The results imply that economic circumstances could spur a positive feedback loop whereby grid electricity prices continue to rise and increasing numbers of customers choose alternatives (sometimes referred to as a " utility death spiral "), particularly in areas with relatively high electric utility rates. Utility companies and policy makers must take the potential for grid defection seriously when evaluating energy supply strategies.

Until recently, the relatively high levelized cost of electricity from solar photovoltaic (PV) technology limited deployment; however, recent cost reductions, combined with various financial incentives and innovative financing techniques,... more

Until recently, the relatively high levelized cost of electricity from solar photovoltaic (PV) technology limited deployment; however, recent cost reductions, combined with various financial incentives and innovative financing techniques, have made PV fully competitive with conventional sources in many American regions. In addition, the costs of electrical storage have also declined enough to make PV + battery systems potentially economically viable for a mass-scale off-grid low-emission transition. However, many regions in the U.S. (e.g. Northern areas) cannot have off-grid PV systems without prohibitively large battery systems. Small-scale combined heat and power (CHP) systems provide a potential solution for off-grid power backup of residential-scale PV + battery arrays, while also minimizing emissions from conventional sources. Thus, an opportunity is now available to maximize the use of solar energy and gain the improved efficiencies possible with CHPs to deploy PV + battery + CHP systems throughout the U.S. The aim of this study is to determine the technical viability of such systems by simulating PV + battery + CHP hybrid systems deployed in three representative regions in the U.S., using the Hybrid Optimization Model for Electric Renewable (HOMER) Pro Microgrid Analysis tool. The results show that the electricity generated by each component of the hybrid system can be coupled to fulfill the residential load demand. A sensitivity analysis of these hybrid off grid systems is carried out as a function capacity factor of both the PV and CHP units. The results show that conservatively sized systems are technically viable in any continental American climate and the details are discussed to provide guidance for both design and deployment of PV + battery + CHP hybrid systems to reduce consumer costs, while reducing energy- and electricity-related emissions.

For islanded microgrids, droop-based control concepts have been developed both in single and three-phase variants. The three-phase controllers often assume a balanced network; hence, unbalance sharing and/or mitigation remains a... more

For islanded microgrids, droop-based control concepts have been developed both in single and three-phase variants. The three-phase controllers often assume a balanced network; hence, unbalance sharing and/or mitigation remains a challenging issue. Therefore, in this paper, unbalance is considered in a three-phase islanded microgrid in which the distributed generation (DG) units are operated by the voltage-based droop (VBD) control. For this purpose, the VBD control, which has been developed for single-phase systems, is extended for a three-phase application and an additional control loop is added for unbalance mitigation and sharing. The method is based on an unbalance mitigation scheme by DG units in grid-connected systems, which is altered for usage in grid-forming DG units with droop control. The reaction of the DG units to unbalance is determined by the main parameter of the additional control loop, viz., the distortion damping resistance, Rd. The effect of Rd on the unbalance mitigation is studied in this paper, i.e., dependent on Rd, the DG units can be resistive for unbalance (RU) or they can contribute in the weakest phase (CW). The paper shows that the RU method decreases the line losses in the system and achieves better power equalization between the DG unit’s phases. However, it leads to a larger voltage unbalance near the loads. The CW method leads to a more uneven power between the DG unit’s phases and larger line losses, but a better voltage quality near the load. However, it can negatively affect the stability of the system. In microgrids with multiple DG units, the distortion damping resistance is set such that the unbalanced load can be shared between multiple DG units in an actively controlled manner rather than being determined by the microgrid configuration solely. The unit with the lowest distortion damping resistance provides relatively more of the unbalanced currents.

Hybrid micro-grids require harmony operation of renewable energy resources based voltage source inverters (VSIs) in grid-tied as well as islanded modes. In this paper, the modeling, analysis, and control strategy of VSIs based autonomous... more

Hybrid micro-grids require harmony operation
of renewable energy resources based voltage source inverters
(VSIs) in grid-tied as well as islanded modes. In this paper, the
modeling, analysis, and control strategy of VSIs based
autonomous micro-grid are developed. An integrated control
system for autonomous micro-grid is carried out including two
control levels. The primary control level is comprised of the
current and voltage inner control loops, the virtual inductor
loops, and the droop control loops. This control level is
necessary to regulate voltage and frequency, and also to
achieve accurate power sharing among the paralleled
distributed generators (DGs). However, the secondary control
level is employed to eliminate the voltage magnitude and
angular frequency deviations produced by primary control
level. The parameters of secondary controllers are optimized
using particle swarm optimization technique to achieve good
dynamic and steady state performance for micro-grid voltage
and frequency. Two micro-grid structures are modeled and
simulated in MATLAB environment to accomplish this study.
The first structure consists of only one distributed generation
unit, while the second contains four DGs. Each structure is
tested with and without secondary control level under the load
variations to confirm the robustness of the control system. The
results of the traditional and optimized secondary controllers
are compared.

Power Hardware-In-the-Loop (PHIL) simulation, allows the connection of a physical power component (e.g. Photovoltaic (PV) inverter) to a real-time simulated network. In this paper PHIL simulation is used for laboratory education in a... more

Power Hardware-In-the-Loop (PHIL) simulation, allows the connection of a physical power component (e.g. Photovoltaic (PV) inverter) to a real-time simulated network. In this paper PHIL simulation is used for laboratory education in a systematic way for the first time. Four important topics for the understanding of power system operation are selected and laboratory exercises are designed respectively. The topics focus on the effects of increased integration of Distributed Generation (DG), namely power sharing between synchronous generators and DG, voltage control with On Load Tap Changer (OLTC) and DG, short circuits with inverter-based DG and microgrid operation. The exercises start from the operation of the traditional power system and gradually incorporate DG related topics that show both benefits and challenges. A hands-on approach is supported by the appropriate lab configuration consisting of two independent PHIL setups. The assessment of the laboratory exercises by the students is clearly positive underlining the value of PHIL simulation for power system education.

Global demand for electrical energy has never been higher than it is currently. This high demand for electricity has driven need for innovative and sustainable power production schemes. The current power system is therefore challenged... more

Global demand for electrical energy has never been higher than it is currently. This high demand for electricity has driven need for innovative and sustainable power production schemes. The current power system is therefore challenged with the need for quality, reliable and sustainable power production. In most countries, the system is aging, making it require more resources to meet contemporary challenges, coupled with the requirements to maintain a clean environment and mitigate environmental disasters. These lead to the microgrid concept. Deployment and use of the microgrid comes with new challenges-control and protection. In this paper, some of the most obvious control challenges of microgrid operations have been articulated. Nine (9) of the recent control strategies in literature have also been presented in this paper, including a brief explanation on the fundamental principles of the proposed strategies. Finally, this paper also presents a comparison of the strengths and weaknesses associated with the control strategies in literature.