Capacity Of Power Unit Research Articles

Optimal Backup Power Deployment for Communication Network With Interdependent Power Network

Smart grid has a power network with an interdependent communication network. In such a system, a node failure can lead to another failure in its dependent node in the other network. These inter-network failures can occur recursively in a cascading process, resulting in a complete system collapse. Such cascading failure process can be interrupted by providing backup power to communication nodes, so that they can continue operation when the power nodes they depend on have failed. It is costly to install a backup power unit at each communication node. We have used the two-stage percolation theory to determine the system robustness as a function of backup power deployment density and backup power unit capacity. Then, we propose a novel scheme to determine the optimal backup power deployment density and unit capacity, which can minimize the backup power deployment cost without compromising a desired system robustness. Through extensive simulations, we have found that when the probability of initial node failure is below its critical value, the deployment cost may decrease linearly with a smaller network size and may increase exponentially with a higher robustness requirement.

Assessment of radiation heat transfer influence on parameters of temperature fields of various design fuel rods

VVER-1000 reactors use cylindrical smooth-core fuel rods. Previously, a model to determe the fuel rod temperature field in a two-dimensional problem statement has been developed and verified. However, modelling assumptions do not consider the influence of variable thermophysical properties, radiation heat transfer, and the opening in the fuel rod on the final parameters of the temperature fields. The impact assessment is an urgent task to improve the economic efficiency of the fuel cycle and the capacity of power units. To develop models and study the features of energy release in nuclear reactors, a numerical package of thermophysical modeling COMSOL Multiphysics software is used. The simulation of temperature fields is performed based on the heat equation with an internal heat source, under the boundary conditions of the second kind at the ends of the fuel rod and the boundary conditions of the third kind on the side surface of the rod. Аn axisymmetric model in two-dimensional problem statement and a three-dimensional model of the fuel rod are developed. The temperature distribution fields are determined by the finite element method. The results of calculations of various design fuel rods are presented. The results have showen that the radiation heat transfer significantly affects the maximum fuel temperature (UO2). The impact degree of variability of thermophysical properties and radiation heat transfer is determined. It was found that the temperature characteristics under different specified conditions have a difference in the range of 15,5–282,0 K (0,8–14,4 %). The developed models are reliable and confirmed by the previously verified model, the characteristics of the fuel assembly used on the VVER-1000 units. The results presented can be used for mathematical modeling of heat transfer processes, both during the modernization of the equipment in operation, and during the development, design, and operation, which will increase the efficiency of electric energy generation at the power unit of a nuclear power plant.

Состояние разработок двухфазных систем терморегулирования космических аппаратов

The progress of space technology is leading to more and more energy-equipped spacecraft. The International Space Station already has the capacity of solar panels of more than 100 kW. Autonomous spacecrafts and satellites (including stationary ones) have the capacity of power units of kW, in the nearest future - more than 10 kW. Forced heat transfer using single-phase liquid coolants is still considered as the main method of thermal control on high-power spacecraft (SC). Single-phase mechanically pumped fluid loop is a fully proven means of thermal control of spacecraft with a moderate heat load. A significant disadvantage of such systems is that the coolant temperature varies significantly within the loop. The temperature difference can be reduced by increasing the coolant flow rate, but for this, it is necessary to increase the pump capacity, which inevitably leads to an increase in power consumption, pipeline diameters, and weight of the system as a whole. In the case of spacecraft with high power capacity (more than 5-10 kW) and large heat transfer distances (10 m and more), a two-phase mechanically pumped fluid loop for thermal control is more preferable in terms of weight, the accuracy of thermoregulation, power consumption (and other parameters). The use of a two-phase loop (2PMPL) as a spacecraft thermal control system allows to reduce significantly mass and power consumption for own needs in comparison with a single-phase thermal control system (TCS). The effect is achieved due to the accumulation of transferred heat in the form of latent heat of vaporization and intensification of heat exchange at boiling and condensation of coolant. The article provides a critical review of published works on 2PMPL for spacecraft with high power (more than 5...10 kW) and a large heat transfer distance (more than 10...100 meters) from 1980 up to nowadays. As a result, a list of the main problems on the way of practical implementation of two-phase loops is formed.

РАЗРАБОТКА КОНЦЕПЦИИ ДВУХФАЗНОЙ СИСТЕМЫ ТЕПЛООТВОДА СПУТНИКА

For spacecraft (SC) with power unit capacity more than 4 ... 6 kW promising construction of thermal control system (TCS) based on two-phase mechanically pumped loops (2PMPL). The development of 2PMPL has been carried out quite intensively since the early '80s. However, so far there are no examples of practical implementation of such high-power systems. One of the main reasons mentioned is the novelty of the system, and insufficient study of its operation in space conditions, which adds risks. The most important component of such systems is a heat rejection subsystem (HRS), whose task is to reject heat from the coolant and radiate it into space. In its turn, HRS is also a system, the design of which requires using a system approach, considering various aspects of its operation. HRS includes a heat-hydraulic network and a radiation heat exchanger (RHE). The key elements of the HRS are condensers (CC), quite new devices for space technology. This paper presents an algorithm for the design and optimization of the heat rejection subsystem (HRS) of a satellite two-phase thermal control system. The methodology of engineering synthesis of complex technical systems and informal procedures for multi-criteria optimization of elements and subsystems at various stages of HRS design is repeatedly used. t is shown that optimization should be carried out both at the level of elements and subsystems, and at the level of the whole thermal control system. As a result of the study, the HRS design is proposed, which uses condensers in the form of smooth steel tubes of constant cross-section and their series-parallel connection scheme in the hydraulic network. Main advantages of the design: traditional for single-phase loops elements are used; operation of elements and subsystems in zero gravity conditions is predictable and allows complete testing on the ground without mandatory flight experiment; the system is operable at high saturation pressures (temperatures) (on ammonia - up to 85℃).

Research on Operation of Electrothermal Integrated Energy System Including Heat Pump and Thermal Storage Units Based on Capacity Planning

In view of the Three North areas existing wind power absorption and environment pollution problems, the previous scholars have improved the wind abandon problem by adding electrothermal coupling equipment or optimizing power grid operation. In this paper, an electrothermal integrated energy system including heat pump and thermal storage units was proposed. The scheduling model was based on the load data and the output characteristics of power units, each power unit capacity was programmed without constraints, and the proposed scheduling model was compared with the traditional combined heat and power scheduling model. Results showed that the investment and pollutant discharge of the system was reduced respectively. Wind power was fully absorbed. Compared with the traditional thermal power unit, the proportion of the output was significantly decreased by the proposed model. The proposed system could provide a new prospect for wind power absorption and environment protection.

Study of feedwater regenerative heating operating modes at reduced loads of a turbogenerator by 300 MW power unit capacity

The article presents the results of numerical studies and analysis of the feedwater regenerative heating operating modes depending on power unit capacity. The main parameters of this system are the enthalpy of the turbine steam extraction for heaters, as well as the steam consumption in these extractions. The dependences of the turbine unit steam flow rate and the change in expansion process of the steam turbine during the load regulation were investigated. The mathematical model of calculation the thermal power plant for a 300 MW power unit capacity was developed. Following on the results of the calculation conclusions of feed water regenerative heating operating modes at reduced loads of a turbine-generator for a 300 MW unit.

Improvement to electricity generation systems by using a refrigeration machine and solar concentrator for air cooling

A process scheme of using the absorption refrigeration machine in electricity generation systems in case of application of air cooling system of the steam turbine electric generators has been developed. The proposed scheme increases thermal power plant efficiency by 0.1-0.2% according to preliminary estimates, primarily by reducing power consumption on pumps and fans drive, as well as by reducing temperature of cooling heat carrier in the period with high ambient temperatures. A feature of the proposed technology is the combination of the most efficient air-cooling scheme and the absorption plant cycle in a single power technology complex. In this refrigeration machine, the working fluid is a binary mixture, one of the components of which is called a refrigerant, and the other one is an absorbent, where the liquid absorbent can absorb the refrigerant vapor. For the first time it is proposed to use an absorption refrigerating machine as the cooling system element of steam turbine electric generators. Currently, there are advanced air-cooling systems using multi-jet cooling for turbo-generators with a capacity of 3 to 180 MW. Finally, it can be used to increase the unit capacity of power units on the thermal power plants that use air-cooled power generators.

Synthesis of Boiler Controllers of the Automatic Power Control System of Power Units

The article concerns the problem of structure-and-parametric optimization of a cascade automatic control system (CACS) by an example of a boiler power controller and a fuel controller. This CACS, which is a part of automatic control systems for power units, consists of two loops, viz. of an inner loop (which purpose is stabilization of the system) and an outer loop (designed for the adjustment) and, also, of two controller, viz. an outer controller (which is a basic one) provided for stabilization of the output value of the object (in our case, of the actual power unit capacity) and of an inner controller (which is an auxiliary one) provided to regulate fuel consumption. The internal controller builds up the control action with the aid of the boiler load controller of the power unit. As compared to single-loop automatic control systems, the cascade system provides better quality of transient control due to the higher performance of the internal loop of the system. This advantage is especially noticeable when compensating for disturbances that come through the channel of regulating impact. The article presents two methods of setting, viz. the fuel controller and the boiler power controller. The application of these methods can improve the quality of power control and reduce fuel consumption in transient modes in comparison with the setting of these controllers of a typical power unit automatic power control system. The results of computer simulation of transient processes in CACS for input step surge and internal perturbation confirm the advantages of the methods are presented in this article.

Генераторные выключатели для атомных электростанций

A comparative analysis of the characteristics of foreign and domestic generator circuit breakers is carried out. The necessity of developing a domestic generator circuit breaker for newly constructed nuclear power plants with a power unit capacity of over 1200 MW is shown. The most promising solution is the development of hybrid generator circuit breakers using main contacts, vacuum circuit breakers and controlled arresters. The scheme and operation of elements of hybrid circuit breakers in modes of shutdown of three
phase short
circuit current is resulted. The developed mathematical model of hybrid breakers consisting of generator, busbar and transformer for power plant and given transients disable the short
circuit current in different modes. It is proposed to develop hybrid circuit breakers to replace oil and air circuit breakers at the stages of modernization of nuclear power plants, and in the new construction it is advisable to use generator circuit breakers, as a prototype of which the gas-insulated device developed by ABB is given. Basic electrical formulas for estimation of the switching capacity of the circuit breaker of the generator in the amplitude of the current gap three
phase short
circuit current, degree of asymmetry, amplitude and rate of rise of transient recovery voltage formulated.&nbsp

Numerical Analysis on the Influence of the Twisted Blade on the Aerodynamic Performance of Turbine

Abstract With the gradual increase of the thermal power unit capacity, the inlet steam parameters and flow of the turbine also increase gradually, which causes considerable secondary flow loss. Therefore, studying the causes and distribution of secondary flow loss within the level is of great significance to effectively improve the stage internal efficiency of turbine. Take high-pressure stage moving blade of a turbine as the research object, and adopt the k-ωSST model, the SIMPLEC algorithm to numerically simulate the formation and development process of leakage vortex between the tip clearance of the positive bending twisted blade and its effect on the secondary flow of cascade passage. Results show that relative to the conventional twisted blade, the scope of influence of leakage vortex which the steam flow formed near the suction surface of positive bending twisted blade and the disturbance to passage mainstream become smaller, and the increase of tip clearance has weakened the „C“ type pressure gradient of suction surface of the positive bending twisted blade, increased the thickness of the boundary layer at both ends of blades and the loss of the blade end.

Estimation of lifespan and economy parameters of steam-turbine power units in thermal power plants using varying regimes

The use of potent power units in thermal and nuclear power plants in order to regulate the loads results in intense wear of power generating equipment and reduction in cost efficiency of their operation. We review the methodology of a quantitative assessment of the lifespan and wear of steam-turbine power units and estimate the effect of various operation regimes upon their efficiency. To assess the power units’ equipment wear, we suggest using the concept of a turbine’s equivalent lifespan. We give calculation formulae and an example of calculation of the lifespan of a steam-turbine power unit for supercritical parameters of steam for different options of its loading. The equivalent lifespan exceeds the turbine’s assigned lifespan only provided daily shutdown of the power unit during the night off-peak time. We obtained the engineering and economical indices of the power unit operation for different loading regulation options in daily and weekly diagrams. We proved the change in the prime cost of electric power depending on the operation regimes and annual daily number of unloading (non-use) of the power unit’s installed capacity. According to the calculation results, the prime cost of electric power for the assumed initial data varies from 11.3 cents/(kW h) in the basic regime of power unit operation (with an equivalent operation time of 166700 hours) to 15.5 cents/(kW h) in the regime with night and holiday shutdowns. The reduction of using the installed capacity of power unit at varying regimes from 3.5 to 11.9 hours per day can increase the prime cost of energy from 4.2 to 37.4%. Furthermore, repair and maintenance costs grow by 4.5% and by 3 times, respectively, in comparison with the basic regime. These results indicate the need to create special maneuverable equipment for working in the varying section of the electric load diagram.

Experience gained from mastering the operation of the Kirishi district power station unit 6 modernized using the combined-cycle technology

This article is devoted to the retrofitting of one of the 300-MW power units at the Kirishi district power station carried out using the combined-cycle technology in order to increase the power unit capacity and make it more efficient. The main and auxiliary equipment of the retrofitted power unit are described. The problems revealed and solved in the course of adjustment works are mentioned. Problems concerned with organizing the startup modes of combined-cycle power units fitted with three-loop heat-recovery boilers and a double-bypass startup circuit arrangement are touched. The design and actually achieved technical and economic indicators of the main equipment and the power unit as a whole are presented. A tangible economic effect is noted from a comparison of the key indicators before and after the retrofitting. It is shown that the retrofitted power unit has good environmental indicators and a very high level of automation.

Integration of large-scale hydrogen storages in a low-carbon electricity generation system

This study investigates the overall feasibility of large energy storages with hydrogen as energy carrier onsite with a pre-combustion carbon capture and storage coal gasification plant and assesses the general impacts of such a backup installation on an electricity generation system with high wind power portion. The developed system plant configuration consists of four main units namely the gasification unit, main power unit, backup power unit including hydrogen storage and ancillary power unit. Findings show that integrating a backup storage in solid or gaseous hydrogen storage configuration allows to store excessive energy under high renewable power output or low demand and to make use of the stored energy to compensate low renewable output or high power demand. The study concludes that the developed system configuration reaches much higher load factors and efficiency levels than a plant configuration without backup storage, which simply increases its power unit capacity to meet the electricity demand. Also from an economical point of view, the suggested system configurations are capable to achieve lower electricity generation costs.

Combined heat and power unit capacity for high-heat to power ratio buildings without selling excess electricity to the grid

This study presents a simple approach to estimate the capacity of combined heat and power (CHP) units suitable for installation in high heat-to-power ratio (HPR) buildings when excess electricity cannot be sold back to the grid. The two different methods used in this approach, a graphical method and a simple equation, are capable of predicting the optimum capacity to within 7% and 15%, respectively, of the methods presented in previous studies. In particular, the simple equation has the advantage of selecting the optimum capacity using the base and peak of the demand power load. The two easy-to-use methods can be used with any building, region, and energy-price structure that satisfies the conditions considered in this study, and will be of great use to future CHP owners.

The problem of optimizing the water chemistry used in the primary coolant circuit of a nuclear power station equipped with VVER reactors under the conditions of longer fuel cycle campaigns and increased capacity of power units

It is shown that the optimal water chemistry of the primary coolant circuit must be substantiated while introducing measures aimed at increasing the power output in operating power units and for the project called AES-2006/AES TOI (a typical optimized project of a nuclear power station with enhanced information support). The experience gained from operation of PWR reactors with an elongated fuel cycle at an increased level of power is analyzed. Conditions under which boron compounds are locally concentrated on the fuel rod surfaces (the hideout phenomenon) and axial offset anomaly occurs are enlisted, and the influence of lithium on the hideout in the pores of deposits on the surfaces of fuel assemblies is shown.

Modernizing the K-1000-60/1500 turbine unit’s condensers by replacing the material of cooling tubes

The results obtained from modernization of the K-1000-60/1500 turbine’s lateral condensers are described. This modernization, in which tubes with thinner walls were used, resulted in a larger heat-transfer surface area and in better average vacuum. A 3.2-MW gain in the power unit capacity was obtained, and better reliability of the condenser itself was achieved.

Increasing the rated capacity of power units installed at Russian nuclear power stations equipped with VVER-1000 reactors

Safe operation of the Balakovo nuclear power station’s Unit 2 built around a VVER-1000 reactor at a thermal power output of 3120 MW with meeting of the safety criteria and compliance with the requirements of existing regulatory documents is substantiated. Results from measurements of process parameters at a power output equal to 104% of its nominal value are presented.