Distributed Generation Plants Research Articles

Model predictive current controller for performance enhancement of grid-integrated single-phase photovoltaic distributed generation plants

Acknowledgement of renewable sources of energy as substitute energy sources for power production has expanded the number of distributed generation plants being incorporated into the conventional power distribution system. The single-phase voltage source inverter allying the photovoltaic plant with the grid has to address various issues identified with the quality of current injected into the grid, output power factor and power exchange between the plant and the grid. This paper concentrates on the investigation, design and implementation of a digital predictive current control technique known as the model predictive current controller for the control of single-phase photovoltaic distributed generation plants. The performance of the controller is evaluated under varied operating conditions. The proposed current controller is compared with the conventional proportional–integral controller in terms of its design methodology, steady state and dynamic response. The simulation and experimental results validates the effectiveness of the proposed model predictive current controller.

Optimal DG Placement with the Aim of Profits Maximization

<p>Using distributed generation power plants is common due to advantages such as system capacity release, voltage support and reduced energy losses in power networks. Prior to the creation of distributed generation plants (DG), economic calculation is needed in order to find the optimum location. In this study, IEEE 57 bus test system is evaluated using two index of LMP and CP. Then, the optimal location of distributed generation plants is studied in experimental network. Finally, the effects of DG correct location on buses LMP after DG installation is studied.</p>

METHODOLOGY OF DETERMINING FORECASTING CONTROLLERS OF DISTRIBUTED GENERATION PLANTS

On the basis of the use of algorithms for forecasting, it becomes possible to set automatic control system with a single parameter - the time of the forecast. Therefore, the predictive algorithms built on the basis of the model laws of regulation may prove to be very promising for real systems of technological process control, especially in the need to accelerate the commissioning of objects, such as distributed generation (DG) plants, working on the basis of synchronous generators with automatic excitation and speed controls (AEC and ASC). The paper presents a methodology of determining the parameters predictive links AEC and ASC and the results of research on the computer model railway power supply systems (RPSS) including in its membership following the DG plants: turbogenerator mini thermoelectric plant, hydro small power plant, wind power plant on the basis of the machine DC and solar power. The results of computer simulation show that the use of predictive units ensures the stability of the generator DG plants at large perturbations in the system without the time consuming procedure of identification of dynamic characteristics and calculation of Проблемы энергетики, 2016, № 11-12 optimal AEC and ASC settings. The proposed method of determining the prognostic regulator parameters can be recommended, if necessary, the operational commissioning of DG plants in railway power supply system.

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ ПРОГНОСТИЧЕСКИХ РЕГУЛЯТОРОВ ДЛЯ УСТАНОВОК РАСПРЕДЕЛЕННОЙ ГЕНЕРАЦИИ СИСТЕМ ЭЛЕКТРОСНАБЖЕНИЯ ЖЕЛЕЗНЫХ ДОРОГ

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ ПРОГНОСТИЧЕСКИХ РЕГУЛЯТОРОВ ДЛЯ УСТАНОВОК РАСПРЕДЕЛЕННОЙ ГЕНЕРАЦИИ СИСТЕМ ЭЛЕКТРОСНАБЖЕНИЯ ЖЕЛЕЗНЫХ ДОРОГ

Relay coordination analysis and protection solutions for smart grid distribution systems

Growing complexity of conventional power grids and their management, increasing power demand and energy quality expectations considering grid reliability, and efficiency and security concerns have triggered the evolution of smart grids. This is an expected result of implementing new technologies in existing grids, including renewable sources such as wind turbines and photovoltaic modules. With implementation of such new elements to the system, the protection concept should be considered by system regulators. In order to analyze protection problems, simulation-based analysis should be carried out before high-cost experimental studies. In this study, a simulation-based evaluation for a smart gridbased distribution system is performed. System simulations are realized considering different fault cases and optimum operating conditions are obtained. A ring grid is designed including a generator and a wind turbine as sources and variable loads as consumers. Several points in the grid are selected as fault locations, and the condition of connecting distributed generation plants to the grid is evaluated in the MATLAB/Simulink environment. This study presents an analysis about the possibility of forming a grid with high reliability and efficiency under fault conditions.

Grid Voltage Synchronization for Distributed Generation Systems Under Grid Fault Conditions

The actual grid code requirements for the grid connection of distributed generation systems, mainly wind and photovoltaic (PV) systems, are becoming very demanding. The transmission system operators (TSOs) are especially concerned about the low-voltage-ride-through requirements. Solutions based on the installation of STATCOMs and dynamic voltage regulators (DVRs), as well as on advanced control functionalities for the existing power converters of distributed generation plants, have contributed to enhance their response under faulty and distorted scenarios and, hence, to fulfill these requirements. In order to achieve satisfactory results with such systems, it is necessary to count on accurate and fast grid voltage synchronization algorithms, which are able to work under unbalanced and distorted conditions. This paper analyzes the synchronization capability of three advanced synchronization systems: the decoupled double synchronous reference frame phase-locked loop (PLL), the dual second order generalized integrator PLL, and the three-phase enhanced PLL, designed to work under such conditions. Although other systems based on frequency-locked loops have also been developed, PLLs have been chosen due to their link with dq0 controllers. In the following, the different algorithms will be presented and discretized, and their performance will be tested in an experimental setup controlled in order to evaluate their accuracy and implementation features.

Investigation on North American Microgrid Facility

According to international reports that have also cited in this article, North America covers the 66% of the global electricity that has generated in microgrids. Besides its 2088 MW installed microgrid capacity in 2012, many new microgrids have been installed in North America. The microgrid plants under development, new planned, and proposed will pursue the leading rank of North America all over the world. Therefore, it has intended to analyze the microgrid plants and studies performed in this region to disseminate the findings. This paper presents a review of various North American distributed generation plants together with their tabled test-beds. The microgrid (MG) projects introduced in this study are surveyed according to their generator structures, their integration to the point of common coupling (PCC), and operation structures. The uniqueness of each MG project has shown in comparison to several others. In addition, the emergency and crisis management methods, precautions against overcharge and low generation issues are also introduced for each MG plant. This allows the researcher to visualize today’s microgrid and to gain insight into the possible evolvement of future grids. The study concludes by emphasizing significant findings and by suggesting potential research areas that would enhance microgrid facilities.

Electrical production of a small size Concentrated Solar Power plant with compound parabolic collectors

The use of the solar energy for electricity or useful heat generation has been extensively investigated as an alternative to fossil fired energy conversion. Particularly in the last decade, many studies have been carried out on Concentrated Solar Power (CSP) which was developed worldwide with Spain acting as the leading country in this field. Concentrating solar energy requires complex mirror systems which continuously move to track the sun. In comparison with flat mirrors, Parabolic Through Collectors (PTCs) have allowed to reduce costs, but they still remain quite an expensive solution. Instead, compound parabolic collectors (CPCs) are able to collect a higher fraction of both the direct and the diffuse radiation, although they have a lower efficiency at high temperature. Moreover, at least within certain limits, they do not require a tracking system. Their employment is therefore suited for the collection of medium temperature heat (up to 200 °C) and is useful for the reduction of the installation cost of Concentrated Solar Power (CSP) heating/cooling and energy generation systems. Small size plants (10–50 kW) were studied in this paper since they are more likely to be realized due to their smaller initial investment cost and to the capability of being installed on the roof of existing buildings. While the Organic Rankine Cycle (ORC) solution is well established to be the optimal for small size, distributed generation plants, the technology of the expansion device is still to be defined for the investigated installed power range. Accordingly to previous studies, an expansion device based on the Wankel mechanism was employed.Based on these considerations and prior to more detailed analyses, a study of the annual energy production of a small scale ORC power plant using CPCs as a heat source and a volumetric machine as an expansion device was carried out. The influence of the thermodynamic cycle parameters, the working fluid, the concentration and the tilt angle of the collectors on the electrical energy production were taken into account. The thermal module power output, the expansion device isentropic efficiency and the overall efficiency were evaluated by means of a numerical model developed within the simulation tool AMESim v.12.0.The aim of this work is to provide a contribution in the assessment of the optimal configuration of such kind of plants in terms of collectors concentration and tilt angle on one hand, and thermodynamic parameter of the thermal module on the other. The annual electricity production was used as a criterion of comparison among the various parameters combinations. The number of operating hours per year was also taken into account for the sake of ensuring a regular production of energy. A selection of commercial solar tubes for the realization of the solar field was carried out and the optimal configuration for both the solar field and the thermal module was found. The results of this study are encouraging and constitute the basis for the development of future analyses.

When does unreliable grid supply become unacceptable policy? Costs of power supply and outages in rural India

Despite frequent blackouts and brownouts, extension of the central grid remains the Indian government׳s preferred strategy for the country׳s rural electrification policy. This study reports an assessment that compares grid extension with distributed generation (DG) alternatives, based on the subsidies they will necessitate, and costs of service interruptions that are appropriate in the rural Indian context. Using cross-sectional household expenditure data and region fixed-effects models, average household demand is estimated. The price elasticity of demand is found to be in the range of −0.3 to −0.4. Interruption costs are estimated based on the loss of consumer surplus due to reduced consumption of electric lighting energy that results from intermittent power supply. Different grid reliability scenarios are simulated. Despite the inclusion of interruption costs, standalone DG does not appear to be competitive with grid extension at distances of less than 17km. However, backing up unreliable grid service with local DG plants is attractive when reliability is very poor, even in previously electrified villages. Introduction of energy efficient lighting changes these economics, and the threshold for acceptable grid unreliability significantly reduces. A variety of polices to promote accelerated deployment and the wider adoption of improved end-use efficiency, warrant serious consideration.

Optimization of Hybrid Distributed Generation Systems For Rural Communities in Alaska

This article summarizes the results from a feasibility study to de-sign optimal distributed generation (DG) plants for three remote com-munities in Alaska. All three of these towns have isolated electrical gridsand currently rely on diesel fuel for 100% of their electricity and heatingrequirements. This assessment included an analysis of each communi-ty’s electrical and thermal load, a wind and solar resource evaluation,modeling and optimization of various DG systems using HOMER soft-ware, and an economic analysis of these systems. For all three of thecommunities, hybrid wind-diesel systems have the potential to providereductions in the cost of energy. However, the economic feasibility ofthese systems is extremely site-specific. In addition to providing possibledecreases in the cost of energy, these hybrid systems can also providesignificant environmental benefits, such as reductions in diesel fuel useand CO2 emissions. Future research should evaluate hybrid solar/windgenerators with combined-heat-and- power (CHP) diesel engines.

Application of Synchronised Phasor Measurement Technology in Renewable Energy Systems

This paper throws light on application of synchronized phasor measurement in renewable energy systems. Power generation from renewable energy system connected to the grid is highly dynamic, non linear which needs to be monitored continuously for efficient and reliable system. There are various methods of monitoring of power from renewable energy system to grid. Nowadays, time synchronized phasor measuring method proves to be a revolutionary method for power system monitoring. Synchronized PMU has wide application such as wide area monitoring, real time monitoring, post even analysis, visualization, state estimation etc. they are employed in micro grid and distributed generation plants mainly for solving islanding issues. This paper summarises the synchrophasor application and its future scope in renewable energy system

Optimization of Hybrid Distributed Generation Systems For Rural Communities in Alaska

ABSTRACTThis article summarizes the results from a feasibility study to design optimal distributed generation (DG) plants for three remote communities in Alaska. All three of these towns have isolated electrical grids and currently rely on diesel fuel for 100% of their electricity and heating requirements. This assessment included an analysis of each community's electrical and thermal load, a wind and solar resource evaluation, modeling and optimization of various DG systems using HOMER software, and an economic analysis of these systems. For all three of the communities, hybrid wind-diesel systems have the potential to provide reductions in the cost of energy. However, the economic feasibility of these systems is extremely site-specific. In addition to providing possible decreases in the cost of energy, these hybrid systems can also provide significant environmental benefits, such as reductions in diesel fuel use and CO2 emissions. Future research should evaluate hybrid solar/wind generators with combine...

A Sustainability-Oriented Multiobjective Optimization Model for Siting and Sizing Distributed Generation Plants in Distribution Systems

This paper proposes a sustainability-oriented multiobjective optimization model for siting and sizing DG plants in distribution systems. Life cycle exergy (LCE) is used as a unified indicator of the entire system’s environmental sustainability, and it is optimized as an objective function in the model. Other two objective functions include economic cost and expected power loss. Chance constraints are used to control the operation risks caused by the uncertain power loads and renewable energies. A semilinearized simulation method is proposed and combined with the Latin hypercube sampling (LHS) method to improve the efficiency of probabilistic load flow (PLF) analysis which is repeatedly performed to verify the chance constraints. A numerical study based on the modified IEEE 33-node system is performed to verify the proposed method. Numerical results show that the proposed semilinearized simulation method reduces about 93.3% of the calculation time of PLF analysis and guarantees satisfying accuracy. The results also indicate that benefits for environmental sustainability of using DG plants can be effectively reflected by the proposed model which helps the planner to make rational decision towards sustainable development of the distribution system.

Energy and Exergy Analysis of a combined Diesel-Engine Gas-Turbine System for Distributed Power Generation

This paper presents a combined diesel-engine gas-turbine system that enables distributed power generation plants to attain high thermal efficiencies while enjoying the operational advantages of both diesel engines and gas turbines. The configuration of the system presented here improves upon previously proposed configurations through the appropriate use of regeneration and inter-cooling. Energy and exergy analyses of the system's performance were performed using an Excel-based thermodynamic model. The energy analysis studied the effect of the diesel-engine's compression ratio, the gas-turbine's inlet temperature, and the compressors' pressure ratios on the system's performance. This analysis determined the pressure ratios that permit the system to be designed with fewer compressors and turbines. The second law analysis determined the main exergy losses and destructions of the system. Finally, the paper compares the thermal efficiency and network of the proposed system at different modes of operation

Novel Dual-FCL Connection for Adding Distributed Generation to a Power Distribution Utility

A novel dual-connection of fault current limiters is described for use when connecting new distributed generation plants to the electric grid. The operation and control scheme of this connection are described and analysed. The proximate arrangement of the two current limiters has the advantage that they can share one cryogenic system. The dual connection limits fault currents sufficiently to avoid disturbing the original protection relay schemes of the utilities, and also improves synchronism between the new generator and the grid. These benefits are proven by simulations of a 36 MW, 4.16 kV gas turbine generator connected to an infinite grid. This dual-FCL connection reduces fault current contributions of the DG by 97% (from 41 to 1 kA), and maintains the circuit breakers within their duty limits when a three-phase fault occurs at a bus connected to the DG. Otherwise, when a three-phase fault occurs in the infinite system, this connection limits the fault current contribution of the DG from 4.8 to 0.4 kA, and frequency oscillations of the DG from 0.14 to 0.01 Hz. The power continuity in the local network is improved, as the voltage sag at the bus connected to the DG is reduced by 96% (from 851 to 32 V) during and after serious short-circuit faults.

Integrated biomass gasification combined cycle distributed generation plant with reciprocating gas engine and ORC

Abstract The paper theoretically investigates the performance of a distributed generation plant made up of gasifier, Internal Combustion Engine (ICE) and Organic Rankine Cycle (ORC) machine as a bottoming unit. The system can be used for maximization of electricity production from biomass in the case where there is no heat demand for cogeneration plant. To analyze the performance of the gasifier a model based on the thermodynamic equilibrium approach is used. Performance of the gas engine is estimated on the basis of the analysis of its theoretical thermodynamic cycle. Three different setups of the plant are being examined. In the first one the ORC module is driven only by the heat recovered from engine exhaust gas and cooling water. Waste heat from a gasifier is used for gasification air preheating. In the second configuration a thermal oil circuit is applied. The oil transfers heat from engine and raw gas cooler into the ORC. In the third configuration it is proposed to apply a double cascade arrangement of the ORC unit with a two-stage low temperature evaporation of working fluid. This novel approach allows utilization of the total waste heat from the low temperature engine cooling circuit. Two gas engines of different characteristics are taken into account. The results obtained were compared in terms of electric energy generation efficiency of the system. The lowest obtained value of the efficiency was 23.6% while the highest one was 28.3%. These are very favorable values in comparison with other existing small and medium scale biomass-fuelled power generation plants.

Dynamic fault location method for distribution networks with distributed generation

This paper presents a new analytical time-based fault location algorithm for radial distribution networks with synchronous generators used for distributed generation (DG). The algorithm uses the voltage and current samples recorded at the main feeder head along with the scheduled injected active and reactive powers by the network synchronous generators to estimate the fault location. A full order synchronous machine model has been used to consider dynamic behaviour of the DG plants during fault transients. The algorithm, therefore, uses time domain analysis and is dynamic in the sense that it uses the updated synchronous machines and network data at each time step. The algorithm is implemented in two sequential steps. In the initialisation step, by using the measured pre-fault voltage at the main feeder head and scheduled power injections by the DG plants, a pre-fault load flow calculation is performed to evaluate different parameters of the synchronous generators, initial values of the network node voltages, line section currents, loads and capacitive charging currents. In the second step, the numerical fault location algorithm is performed by moving the data window from the pre-fault to a post-fault cycle. The accuracy of the proposed algorithm has been validated by several simulated fault studies carried out on a 205-node 20 kV practical radial distribution feeder. The results have shown remarkable accuracy in fault location when considering only the current and voltage measurements at the main feeder head have been used.

Dispachability improvement of wind generation by the Virtual Power Producers

Today, there is a growing environmental concern about where the energy that we use comes from, bringing the attention on renewable energies. However, the use and trade of the renewable energies in the market seem to be complicated because of the lack of guarantees of generation, mainly in the wind farms. The lack of guarantees is usually addressed by using a reserve generation. The aggregation of Distributed Generation plants gives place to a new concept: the Virtual Power Producer (VPP). VPPs can reinforce the importance of wind generation technologies, making them valuable in electricity markets. This paper presents some results obtained with a simulation tool (ViProd) developed to support VPPs in the analysis of their operation and management methods and of their strategies effects.

Radial MV networks voltage regulation with distribution management system coordinated controller

The connection of a great number of distributed generation (DG) plants may cause a critical voltage regulation problem in actual medium voltage (MV) radial distribution networks. After a synthetic survey of different strategies reported in literature to solve this problem, a proposal for an active management of the distribution system which makes use of an innovative controller that coordinates the on load tap changer (OLTC) action with the regulation of reactive exchanges between DG plants and feeders, is presented. In order to test the effectiveness of the proposed regulation, the distribution management system coordinated controller (DMSCC) is applied to a realistic radial structure distribution network and its behaviour simulated in managing the MV system during its worst foreseeable working conditions.

Modeling and control of distributed generation systems including PEM fuel cell and gas turbine

This paper concentrates on the modeling and control of distributed generation systems including fuel cell and gas turbine. The fuel cell is connected to the power system through a dc/ac converter, which is equipped with both voltage- and power-control loops. The gas turbine is also assumed to be equipped with both voltage-control and generation (or frequency)-control loops. Moreover the gas turbine is modeled using the d–q frame of reference. The interfacing of the gas turbine with the power system is achieved by transforming its equations from the d–q frame of reference to power system frame of reference. A multivariable supplementary fuzzy logic controller is proposed for improving the dynamics of the combined fuel cell and gas turbine system. This fuzzy logic controller is designed using the Matlab Fuzzy Logic Toolbox A distribution test system including a load, a fuel cell and a gas turbine, connected to a power grid is simulated using Matlab/Simulink software package. The dynamics of the combined distributed generation plant are analyzed for the cases of with and without controller. The accuracy of the presented model and the effectiveness of the proposed multivariable supplementary fuzzy controller are deduced from the simulation results.