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Abstract Turbines are generally oversimplified in conventional algorithms for steady‐state analysis of hydropower plant (HPP) networks. Moreover, conventional algorithms are hardly suitable for serial HPPs. In this paper, a modified global gradient algorithm (MGGA) is developed by extending turbine models and optimizing turbine interpolation. First, the nonlinear model of turbines is established with the proposed variable resistance factor and added to the global matrix. Then turbine unit quantity interpolation is proposed to compute the turbine operating parameters. Finally, turbine links and pipes can be iterated synchronously, and the global matrix is solved using the Newton–Raphson method. Characteristics of MGGA are evaluated by employing two test HPPs, including rapidity of convergence, computational stability of turbine, and applicability for serial HPPs. The results show that: (a) The iterative numbers of the MGGA are 0.72 and 4.98 times on average less than that of CA1 and CA2 for the accuracy of 10−6 in 400 operating conditions, even though MGGA has an obvious hysteretic nature; (b) Only MGGA can successfully calculate the extreme cases that large head losses in HPP networks; (c) Although fixed head nodes are not present between turbine links, such as serial HPPs, MGGA still works.

Turbines are generally oversimplified in conventional algorithms for steady‐state analysis of hydropower plant (HPP) networks. Moreover, conventional algorithms are hardly suitable for serial HPPs. In this paper, a modified global gradient algorithm (MGGA) is developed by extending turbine models and optimizing turbine interpolation. First, the nonlinear model of turbines is established with the proposed variable resistance factor and added to the global matrix. Then turbine unit quantity interpolation is proposed to compute the turbine operating parameters. Finally, turbine links and pipes can be iterated synchronously, and the global matrix is solved using the Newton–Raphson method. Characteristics of MGGA are evaluated by employing two test HPPs, including rapidity of convergence, computational stability of turbine, and applicability for serial HPPs. The results show that: (a) The iterative numbers of the MGGA are 0.72 and 4.98 times on average less than that of CA1 and CA2 for the accuracy of 10−6 in 400 operating conditions, even though MGGA has an obvious hysteretic nature; (b) Only MGGA can successfully calculate the extreme cases that large head losses in HPP networks; (c) Although fixed head nodes are not present between turbine links, such as serial HPPs, MGGA still works. [ABSTRACT FROM AUTHOR]

Problems of ensuring the high efficiency of steam turbines during operation in partial modes are considered. It is noted that the decrease of steam throttling losses in the control valves has the greatest impact on the efficiency when operating in such modes. A brief overview of known techniques for increasing the efficiency of turbines by optimizing the operating modes of the control stage and the steam admission system, which consist in obtaining additional throttleless modes due to the combined operation of control stage nozzle boxes with different number of nozzles, is given. However, when implementing such techniques in dynamics, problems and limitations arise associated with the need for abrupt switching of control valves. A promising method (algorithm) for controlling the control valves of a steam turbine that ensures the optimization of the operating mode of the control stage and the minimum throttling losses in the control valves is proposed. The technology for implementation of the proposed control method, its advantages over the traditional one, and development prospects are stated. On the example of the T-295/335-23.5 turbine, the results of calculating the efficiency of the control stage with sequential and optimized steam admission, carried out by the proposed control method, are presented. The tests of optimized steam admission implemented by two methods, traditional and proposed one, are carried out on the mathematical model of T-295/335-23.5 turbine. The test results are presented in the form of graphs of transient processes. It is shown that, due to the optimization of steam admission by the proposed control algorithm for control valves, the disadvantages inherent in the implementation of the traditional method are eliminated, namely, the quality of transient processes is increased, there are no abrupt switching of control valves, the amplitude of steam temperature fluctuations in the nozzle boxes decreases, and it becomes possible to control the rate of their heating during optimization. [ABSTRACT FROM AUTHOR]

The paper attempts to correlate simulations and measurements of turbine performance under pulsating flows for automotive turbochargers. Under real automotive powertrain conditions, turbochargers are subjected to pulsating flows, due to the motion of the engine's valves. Experiments on a purpose-built 2.2 L diesel engine gas-stand have allowed the quantification of unsteady pulsating turbine performance. Temperature, pressure and mass flow measurements are fundamental for the characterisation of turbine performance. An adequate sampling frequency of the instruments and acquisition rates are highly important for the quantification of unsteady turbomachine performance. In the absence of fast, responsive sensors for monitoring mass flow and temperature, however, appropriate considerations would have to be taken into account when making estimates of turbine performance under pulsating flows. A 1D model of the engine gas-stand has been developed and validated against experimental data. A hybrid unsteady/quasi-steady turbine model has been adopted to identify unsteadiness at the turbine inlet and outlet. To evaluate isentropic turbine efficiency and reduce the influence of external heat transfer upon measurements, the turbine inlet temperature has been measured experimentally in the vicinity of the turbine rotor in the inlet section, upstream of the turbine tongue. The hybrid unsteady/quasi-steady turbine model considers the presence of unsteady flows in the turbine inlet and outlet, leaving the rest of the turbine to react quasi-steadily. Virtual sensors and thermocouples have been implemented in a 1D model to correlate experimental time-averaged temperature measurements. [ABSTRACT FROM AUTHOR]

The water flow potential in rivers represents significant resources for aquiring cheap energy production. Depending on the three essential parameters of water flow rate, stream velocity and level difference, optimal constructive solutions are usually adopted for choosing the turbine type to be used in order to obtain energy in a hydroelectric power plant. A three-dimensional turbine model has been developed describing the real rotor model which has the possibility of being directly mounted on the water course in order to take over a part from the water energy and to obtain rotational motion at the rotor axis. A water flow analysis is performed in the fluid area built around the rotor model and the results obtained are presented as values for the water flow rate, velocity and water pressure registered within the fluid area. [ABSTRACT FROM AUTHOR]

It is evident the continuous increase of the energy needs, proportionate to the increase of the number of inhabitants, but also due to the increase of the living standards of the human communities. For providing the necessary energy, the fossil fuels are used in the majority proportion, which bring changes to the environment. In order to avoid this disadvantage, energy obtaining methods based on natural renewable resources that are practically unlimited and most importantly do not bring negative changes to the environment are increasingly taken into account. Thus, besides solar energy, wind power, tidal energy and hydro power are solutions that are currently used all over the world, but which need to be further developed in the future. A turbine model working within a hydro power system is described in this paper aiming to highlight the main working parameters. A CFD analysis is conducted on the virtual model and presented the obtained results regarding fluid velocity, absolute pressure, turbine shaft torque and the total power amount calculated values. [ABSTRACT FROM AUTHOR]

The availability of clean energy of wind waves is enough to meet current demand of the world, attracting researches to find devices with good performance to extract this type of energy. The oscillating water column converter is a type of device that has been extensively studied for this purpose. This paper describes a numerical analysis of an onshore oscillating water column device taking into account hydrodynamic and aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The numerical analyses are carried out by the Fluinco model, based on slightly compressible flow method to solve the Navier–Stokes equations, and employing the two-step semi-implicit Taylor–Galerkin method. The aerodynamic model is based on the first law of thermodynamics applied to the air column inside the chamber and on turbines similar to Pico's. The turbine power output with air pressure control inside the chamber due to a relief valve is compared to the one without control. A significant increase in the power output by using the pressure control in comparison with that without control is observed. The analysis of the turbine power output considers different turbine diameters and ranges of rotational speeds. [ABSTRACT FROM AUTHOR]

In this paper, the steady-state and dynamic behavior of a wind farm with reactive power compensation using a StatCom devices is analyzed. An algorithm and a method for calculating the steady-state of the wind farm with SCIG and the random wind speed is proposed. A StatCom is used to minimize the effects of the wind speed variation. Two controllers are analyzed in the StatCom; one PI lineal type and the other is a non-lineal robust type known as Super-Twisting, to regulate the voltage magnitude in the connection node. [ABSTRACT FROM PUBLISHER]

Abstract: The study of ways of converting ocean wave energy into a useful one and the improvement of the existing equipment are complex engineering problems and very important issues in today's society. In this paper, the onshore oscillating water column device, in a 10 m deep channel subjected to 1 m high incident wave and wave periods from 4 s to 15 s, is investigated. The numerical analyses are carried out using Fluinco model that deals with incompressible flow problems based on the Navier–Stokes equations and employs the two-step semi-implicit Taylor–Galerkin method. An aerodynamic model is implemented in the algorithm to determine the air pressure that is imposed on the free surface. Analyses are divided into two sections. In the first section, the flow variables obtained by Fluinco and the commercial model Fluent are compared and similar results are obtained. In the second section, an investigation of the chamber geometry and turbine characteristic relation that provide the best device performance is carried out. In this case, variations in the front wall depth, the chamber length, the turbine characteristic relation and the chamber height, are made. [Copyright &y& Elsevier]

Turkey is a rich country in term of diversity and potential of renewable energy sources. In our country, a large amount of electrical energy is obtained from thermal and hydraulic sources. Hydroelectric power plants (HPP) that have no fuel cost are the cheapest electricity generation plants. A large section of the hydroelectric energy production is obtained from the large HP. Small hydro power plants (SHPP) are alternative energy sources which are especially used in rural areas where the other energy power plants cannot be done and in order to evaluate the small water resources. In this study, the importance of SHPP is emphasized and turbine, generator, and governor models are constructed in Matlab-Simulink to make load-frequency control of a SHPP. Then, combining these models a small hydro electric power plant model was obtained. Power-time and frequency-time variations are obtained for different loading condition using HPP models with linear and nonlinear turbines. [ABSTRACT FROM AUTHOR]

In this paper, the procedure for deriving the parameters of an IEEE governor-turbine model (particularly turbine model) based on a practical study case consisting of a 200-MW tandem compound, single reheat steam unit and its available heat balance data is presented. The main focus of the work is on presenting a regular procedure and using only available heat balance data of the steam unit, to be suitable for training the principles and details of such an approach for educational purposes. Unavailable parameters are approximated with simple thermodynamic assumptions, resulting in good correspondence to typical values. The model response to step changes for special scenarios is simulated and presented as well. [ABSTRACT FROM AUTHOR]