Dispersed Power Systems Research Articles

Frequency Control in Dispersed Power System Using Partially Decentralized Combined Fuzzy-PID (PD-CFPID) Regulator

Frequency Control in Dispersed Power System Using Partially Decentralized Combined Fuzzy-PID (PD-CFPID) Regulator

Grasshopper optimisation algorithm of multistage PDF + (1 + PI) controller for AGC with GDB and GRC nonlinearity of dispersed type power system

This article introduces Grasshopper Optimisation Algorithm (GOA)-based multistage Proportional Derivative filter type (PDF) with One plus Proportional Integral (1 + PI) controller for Automatic Generation control (AGC) in dispersed type three area power system. The control-area 1 consists of thermal, hydro and Wind units. Similarly, control-area 2 consists of thermal, hydro and Diesel units. Control-area 3 consists of thermal, hydro and Gas units. Nonlinearities like Governor dead-band, GRC (generation rate-constraint) and boiler dynamics are included for realistic representation. A comparative analysis is carried out by GOA with multistage PDF + (1 + PI) controller with classical PID/PI controller to justify the superiority of the proposed controller. The dominance characteristic of GOA with PDF + (1 + PI) controller structure is tested over Particle swarm optimisation (PSO) and Genetic algorithm (GA) optimisers with PDF + (1 + PI) controller. The robustness of the complete framework was justified by study and analysis of sensitivity by enhancing and decaying SLP and system elements in a band 50% from its minimal value. From the analysis, it is found that the GOA method with PDF + (1 + PI) controller is providing dominance characteristics performance with random load variations and system parameters of the various components of the power system.

Analysis of exchange processes during parallel operation of wind electric units

Quality control of electric power is usually performed at the point of delimitation, and mutual influence of the elements of power systems and exchange processes between generators is not considered. But in the transition processes, transmission, accumulation or generation of exchange energy take place both between the supporting elements of the power system and between the generators. The influence of exchange processes on the load is compensated by special instruments and the quality of electricity from a consumer’s perspective is almost not affected. However, mutual overflows of energy, even with full compensation, will produce electromagnetic effect on the equipment (for example, magnetic circuit oversaturation) that would cause deterioration in the operating modes of generators, increasing losses, etc. All the above­said predetermines the need for analysis of exchange processes directly in the intersection of generation.So the calculations were carried out of the exchange capacity during the work of two generators with different modes of operation and the influence of perturbations during the work of one generator was studied. We constructed corresponding graphic dependencies of the exchange capacity on the phase shift angle using MathCAD and Excel software applications. By analyzing graphic dependencies, the conclusions were drawn. Even with an active load, the overflows of inactive power in the system are present. We also defined by the graphs the optimal value of the phase shift angle, at which exchange capacity equals zero.The conducted studies make it possible to carry out analysis and optimization of energy processes in dispersed electric power systems with different energy sources, to identify and minimize unwanted energy flows between the elements of the system, as well as to compensate for the mutual influence of various­type electric power sources, both traditional and non­traditional.

Three Dimensional Temperature Distribution Analysis in Directly Internal Reforming SOFC Fuelled by Methane

High SOFC operating temperature allows direct internal reforming (DIR) of methane within the SOFC anode, which is expected to be load-following simple dispersed power system. However, temperature decrease by endothermic reforming reaction leads to carbon formation and increase of thermal stress which cause decrease in the performance and durability of SOFC cells. We have developed a reactor model coupled with computer fluid dynamics and reactions to predict three dimensional temperature distributions. Calculated temperature distributions along flow direction agree with experimentally measured ones in both cases of homogeneous and functionally-graded paper structure catalysts. Detailed three dimensional analyses of temperature distributions tell us the importance of cell structures, gas inlet position, and catalyst thickness. Then, we have extended the analysis tool to more practical model where three SOFC cells are stacked. Temperature distribution in an upstream cell has steeper gradient than that in a downstream cell. Better temperature distribution was obtained by designing functionally-graded paper structure catalysts in two dimensions, along the stacking direction and the gas flow in a cell.

Three Dimensional Temperature Distribution Analysis in Directly Internal Reforming SOFC Fuelled by Methane

High SOFC operating temperature allows direct internal reforming (DIR) of methane within the SOFC anode, which is expected to be load-following simple dispersed power system. However, temperature decrease by endothermic reforming reaction leads to carbon formation and increase of thermal stress which cause decrease in the performance and durability of SOFC cells. We have developed a reactor model coupled with computer fluid dynamics and reactions to predict three dimensional temperature distributions. Calculated temperature distributions along flow direction agree with experimentally measured ones in both cases of homogeneous and functionally-graded paper structure catalysts. Detailed three dimensional analyses of temperature distributions tell us the importance of cell structures, gas inlet position, and catalyst thickness. Then, we have extended the analysis tool to more practical model where three SOFC cells are stacked. Temperature distribution in an upstream cell has steeper gradient than that in a downstream cell. Better temperature distribution was obtained by designing functionally-graded paper structure catalysts in two dimensions, along the stacking direction and the gas flow in a cell.

A power system simulation platform for planning and evaluating distributed generation systems based on GIS

A flexible platform is presented that can effectively be used for planning and analyzing the steady state and dynamic behavior of dispersed power systems, such as distributed generation systems. The proposed platform is developed on geographic information system environment providing an easily handled simulation platform. The functionality of this platform facilitates the utility internal business process by providing planning engineers with a single graphical analysis framework rather than the conventional manual utilization of stand-alone applications within individual desktop studies and avoids the use of paper maps and databases.

Regulation of Parallel Converters with Respect to Stored Energy and Passivity Characteristics

A regulation of converters connected in parallel is discussed considering their stored energy and passivity characteristics. From the viewpoint of stored energy, a new regulation method to conserve and share the stored energy can be found. The energy stored in inductors and capacitors is transferred to loads so that the load keeps the energy dissipation constant. Though numerical simulation, the method is validated for a parallel converter system.

Study on Generator Dispatching Considering Partial Load Efficiency of GT under a Daily Load Curve in Microgrids

Renewable energy technologies such as wind power and photovoltaic energy are getting attentions from view points of energy conservation and environmental issue. However, fluctuation of output power of renewable energy may cause excess variation of voltage or frequency of the grid. Increase of the amount of renewable energy would violate the quality of the grid. The micro grid in which dispersed power systems compensate the variation from the renewable energy can expand the installation limit of the renewable energy by maintaining the quality of the interconnected grid. In this paper, evaluation of the ratio of gas turbines is discussed from the point of power flow stability of the grid, efficiency, economy and CO2 emission in a daily load curve. In addition to the discussion in a daily load curve, the number of gas turbines to be in operation is discussed in this paper.

小規模系統に分散配置された可制御負荷による系統周波数制御法

From depletion of energy resources and consideration to natural environment, dispersed power system such as wind power generator is scheduled for introduction. Additionally, all electrification apartment house or residence and electric vehicles are increase in recent years. However, due to the fluctuating power from renewable energy sources and loads, frequency fluctuation of power system become problematic. This paper presents a methodology for grid frequency control by distributed controllable loads. This system consists of diesel generator, wind farm, and loads. By applying power consumption controller with H∞ control theory, grid frequency fluctuation is maintained around rated value. In order to verify the effectiveness of the proposed system, MATLAB/Simulink is used in simulations.

Study on islanding of dispersed photovoltaic power systems connected to a utility power grid

Photovoltaic (PV) systems and other dispersed power systems need to be connected to a utility power grid for the systems to work effectively as energy sources. Protection against islanding is one of the most important techniques to develop for the dispersed power systems supplying surplus power back to the utility power grid. It is considered that active methods where the outputs of the power systems are actively perturbed are necessary to detect islanding. Various active methods have been developed. It has been shown that these methods work when a single power system is connected to one power distribution line. However, most of these methods have a limit in detecting islanding when multiple power systems are connected to one distribution line. In this paper, we compare the detection characteristics of typical active methods, frequency shift methods, a pulse perturbation method and a method using a correlation technique by simulation analysis for the case of multiple PV power systems. The study shows that the method using the correlation technique is the most promising when multiple power systems are operated on one distribution line.

Training and photovoltaic rural electrification

Utilizing small dispersed photovoltaic power systems for rural electrification has been an attractive idea for many years, but has been hampered by a number of infrastructure and implementation issues. ‘Training’ is often hailed as an important part of the solution, and indeed properly trained installers and designers are essential for the successful growth of this industry, but any training activity must be viewed in the larger context of the realities that it is intended to influence. A well-intentioned training program may still not improve market growth or customer satisfaction. Careful selection of training candidates and accreditation for certification are important overall issues that should be dealt with by the international photovoltaic community to allow ‘Training!’ to make the difference that it should. © 1998 John Wiley & Sons, Ltd.

Detection of islanding of multiple dispersed photovoltaic power systems

Protection from islanding is one of the most important R&D items for photovoltaic (PV) and other dispersed power systems connected to a utility power grid and supplying back surplus power. To protect against islanding, dispersed power systems should be able to detect loss of power in the power grid and be disconnected from the grid immediately. However, a reliable method for detecting the islanding, especially when multiple dispersed systems are connected to one power distribution line, has not yet been developed. We have developed a new method to detect the islanding using correlation techniques. In this article the detecting ability of the correlation method is analyzed when multiple power systems are connected to a power distribution line and compared with that of a usual voltage perturbation method. It is shown that the correlation technique is effective for the case of multiple connection of the PV systems to line, while a usual voltage perturbation method is not effective.

低圧配電線と連系する分散形太陽光発電システムの制御と保護

低圧配電線と連系する分散形太陽光発電システムの制御と保護

Control and protection of dispersed photovoltaic power systems integrated into low—voltage distribution feeders

Control and protection of dispersed photovoltaic power systems integrated into low—voltage distribution feeders

未来都市における太陽光発電技術

In recent years, the siting problem of a large capacity, concentrated power station, especially of nuclear power plant has become serious. Under these circumstances, a new concept has been proposed such that a energy resource must be dispersed in a manner to meet its demand of each area. The concept will change the fundamental constitution of energy system and give a great influence to city planning itself of the area as well.A photovoltaic power generation system can be recommended as a leading member for the dispersed power system because of its nature, e.g., simple system, clean energy, easy handling, maintenance free, etc. It cannot be forgotten for the urban construction of the future.The author explains about a present status and an activity of photovoltaic power generation in accordance with such viewpoint. Further contents are the statistics of solar cell production and its cost, and the technology flow regarding cell production processes and applications, future aspect on conversion efficiency improvement of various kinds of solar cells, a principle system configuration diagram, system classification, etc. Trends in the commercialization toward the introduction to a future city and problems on electric power network at the introduction are also mentioned.

Application of multi-objective stochastic linear programming to power systems planning

In order to further rural development in the Third World, dispersed electrical power systems can be advantageously used. Small communities far removed from the grid expect to be able to produce electricity in the most reliable and self sufficient way with their own limited qualified manpower and primary resources. Solar technologies using thermodynamic or photovoltaic systems may therefore be considered whenever high insolation is available, instead of using diesel engines and expensive fuel. Moreover, the modularity and long lifetime of such systems are very desirable features and it should prove possible to manufacture most components in the developing country itself, after a transition phase. A traditional cost/benefit analysis based on production costs and investment risks is not yet favourable due to the high initial cost of solar systems. Nevertheless, if other criteria such as security of supply, balance of payments, etc., are taken into account, solar energy can possibly be an interesting proposition. An interactive multi-objective analysis can then be developed to consider any number of criteria and to take into account the large future uncertainties associated with projected data available in the energy field. In the first part of this paper, a particular case is described in the context of small rural communities with important solar resources. In section II, the problem is completely modelled as a linear program with three objectives. Scenarios are considered on the basis of average and extreme assumptions of diesel fuel price increases and on solar technology cost reductions. An interactive procedure is applied in section III to resolve this multi-objective stochastic linear program and to obtain a satisfying compromise for the decision maker. A Fortran code, STRANGE, has been written and implemented: the results are presented in terms of the relative production of diesel or solar generators.

Eocnomic Operation of Distributed Power Systems Within an Electric Utility

The authors evaluate the economic operation of distributed power systems within regional synthetic utilities, analyzing the interactions with the utility of customers who can both buy and sell power. These analyses utilize a linked set of economic, financial and engineering models. SYSGEN, an electric utility system operating model, optimizes annual capacity utilization. SYSGEN provides the operation and maintenance data required in ERATES, the utility rate model. ERATES calculates a set of industrial and non-industrial utility rates based on operating and capital costs. The new rates are inputs to SOLOPS and SOLIPS, which are residential, commercial and industrial load simulation models that also compute the economic value of dispersed systems to their owners. The output of SOLOPS and SOLIPS provides load reduction data as input to the SYSGEN model. The modeling cycle allows the authors to analyze the impact of increasing amounts of dispersed power system installations on utility operating and capital costs, thereby analyzing the impact on utility buy and sell rates.

An Economic and Energetic Framework for Evaluating Dispersed Energy Technologies

A model integrating economic and energetic concepts bridges the gap between the natural and social scientists in evaluating the effects of an interface between dispersed energy technologies and auxiliary power systems. The limitations and usefulness of each approach alone are examined and found to be a precise guide to policy when combined because external consideration must be given to national security and the environment. The viability of dispersed systems and their cumulative impact on electricity demand will be a significant part of policy and utility rate debates, and will need to be decided on an individual basis. Research should focus on the application of dispersed systems as supplemental to, rather than replacements for, conventional systems. 43 references, 1 figure, 2 tables. (DCK)