Control of an Open-Loop Hydraulic Offshore Wind Turbine Using a Variable-Area Orifice (original) (raw)
Related papers
Energy, 2015
Current research is evaluating the possibility of shifting the mechanical transmission system in offshore wind turbines to a hydraulic system, whereby a positive displacement pump is connected directly to the rotor. The current study adopts the notion of a large-scale open-loop system, using pressurised seawater to transmit energy from the wind turbine to a centralised hydroelectric generation platform. Using deep seawater as the working fluid allows for its use as a cooling medium in district cooling systems by passing it through a heat exchanger after hydroelectric energy conversion. Novel control schemes for such a system are developed and simulated in the steady state. A high-speed rotor scheme is simulated, improving generation at higher wind speeds. Another two schemes are simulated, which improve power extraction beyond the rated condition by increasing the transmission line pressure. A seasonal control scheme is described, which optimises the mix of electricity and cooling. The system is simulated to be operating off the coast of Malta, a country with moderate wind speeds and a substantial cooling demand. Hourly wind and ambient temperature measurements are fed to the model. Results indicate that the performance and yield are improved by developing control schemes that tailor for the specific system.
Control of Hydrostatic Transmission Wind Turbine
CONTROL OF HYDROSTATIC TRANSMISSION WIND TURBINE by Danop Rajabhandharaks In this study, we proposed a control strategy for a wind turbine that employed a hydrostatic transmission system for transmitting power from the wind turbine rotor via a hydraulic transmission line to a ground level generator. Wind turbine power curve tracking was achieved by controlling the hydraulic pump displacement and, at the other end of the hydraulic line, the hydraulic motor displacement was controlled so that the overall transmission loss was minimized. Steady state response, dynamic response, and system stability were assessed. The maximum transmission efficiency obtained ranged from 79% to 84% at steady state when the proposed control strategy was implemented. The leakage and friction losses of the hydraulic components were the main factors that compromised the efficiency. The simulation results showed that the system was stable and had fast and well-damped transient response. Double wind turbine system sharing hydraulic pipes, a hydraulic motor, and a generator were also studied. The hydraulic pipe diameter used in the double-turbine system increased by 27% compared to the singleturbine system in order to make the transmission coefficient comparable between both systems. The simulation results suggested that the leakage losses were so significant that the efficiency of the system was worsened compared with the single-turbine system. Future studies of other behavioral aspects and practical issues such as fluid dynamics, structure strength, materials, and costs are needed.
Design of Speed Control System for Pelton Turbine
International Journal of Scientific and Research Publications (IJSRP), 2018
In hydropower plants, the water turbines are the heart of electricity generation. In this paper, the turbine used for hydropower plant is the Pelton turbine which is one of the impulse turbines. The design data are taken from Wattwon hydropower in Pyin Oo Lwin, Myanmar. This paper is to design the Pelton turbine, its regulating mechanism and speed control system that can develop a power output of 225 kW. The head of water is 213.36m (700 ft) and the speed of the turbine is 1000 rpm. Since it is required to control the quantity of water flowing, the nozzle and the deflector are the main parts of regulating mechanism. The designed nozzle has a jet velocity of 63.73 m/s, jet diameter of 0.052m and nozzle outlet diameter of 0.064m. The other dimensions of the nozzle and the deflector are also calculated. As hydraulic turbines are usually coupled to AC generators which run at a constant speed, it is essential that the speed of the turbine should also remain constant, irrespective of variation in load. This work is done by a device called the governor. In this paper, the specifications of the governor are calculated.
Journal of Marine Science and Engineering
The present paper proposes the implementation of a new algorithm for the control of the speed regulators of Pelton wheel turbines, used in many of the pumped hydroelectric energy storage systems that operate in isolated electrical systems with high renewable energy participation. This algorithm differs substantially from the standard developments which use PID or PI governors in that, in addition to acting on the nozzle needles and deflectors, it incorporates a new inner-loop pressure stabilization circuit to improve frequency regulation and dampen the effects of the pressure waves that are generated when regulating needle position. The proposed algorithm has been implemented in the Gorona del Viento wind–hydro power plant, an installation which supplies the primary energy needs of the island of El Hierro (Canary Islands, Spain). Although, as well as its wind and hydro generation systems, the plant also has a diesel engine based generation system, the validation of the results of th...
Canal lock variable speed hydropower turbine design and control
IET Renewable Power Generation
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Controls of hydraulic wind power transfer
2011
The energy of wind can be transferred to the generator by employing a gearbox or through an intermediate medium such as hydraulic fluids. In this method, a high-pressure hydraulic system is utilized to transfer the energy produced from a wind turbine to a central generator. The speed control of wind driven hydraulic machinery is challenging, since the intermittent nature of wind imposes the fluctuation on the wind power generation and consequently varies the frequency of voltage. On the other hand, as the load of the generators increases, the frequency of the voltage drops. Therefore, hydraulically connected wind turbine and generator need to be controlled to maintain the frequency and compensate for the power demands. This paper introduces a closed loop gain scheduling flow control technique to maintain a constant frequency at the wind turbine generator. The governing equations of the renewable energy transfer system are derived and used to design the control system. The mathematical model is verified with a detailed model built using the SimHydraulics toolbox of MATLAB. The speed control profile obtained from a gain scheduling PI controller demonstrates a high performance speed regulation. The simulation results demonstrate the effectiveness of both the proposed model and the control technique.
Journal of Computational and Nonlinear Dynamics, 2014
This paper presents a mathematical model of an innovative offshore wind turbine with fluid power transmission. The proposed concept is a variable-speed, pitch controlled turbine which differs from conventional technology by using fluid power technology as a medium to transfer the energy from the wind. The final aim is to use several turbines to centralize electricity generation. Unlike conventional variable speed concepts, the proposed turbine comprises a passive-torque control method which allows the turbine to operate at optimal aerodynamic performance for different wind speeds. A numerical model of a single turbine is developed and time-domain simulations are used to analyze the dynamic response of the different operational parameters to a turbulent wind speed input. The results are compared with those of a reference offshore wind turbine with similar characteristics. It is shown that operation below rated wind speed with a passive control is possible for a single turbine with a better dynamic performance than the reference in terms of transmission torque. However, the efficiency of the energy transmission is reduced throughout the operational range. The addition and simulation of more turbines to the hydraulic network is necessary to determine to which extent the benefits of a centralized wind farm compensate for the relatively lower efficiency. Downloaded From: http://computationalnonlinear.asmedigitalcollection.asme.org/ on 04/23/2015 Terms of Use: http://asme.org/terms
Hydro-turbine governor control: theory, techniques and limitations
2006
With the entry of Tasmania into the national electricity market, equipment upgrades are required in many parts of the existing power system. This presents an opportunity to embrace new technology, in order to enhance the current efficiency and productivity of the system. One area is that of hydro-turbine speed governors, an integral part of maintaining the frequency of the output. This paper analyses the current standard control algorithm for turbine governors, the PID controller. It illustrates the processes involved, tuning and their limitations. Finally, alternative control systems are discussed.
3 Hydraulic Turbines 3.1 INTRODUCTION
In a hydraulic turbine, water is used as the source of energy. Water or hydraulic turbines convert kinetic and potential energies of the water into mechanical power. The main types of turbines are (1) impulse and (2) reaction turbines. The predominant type of impulse machine is the Pelton wheel, which is suitable for a range of heads of about 150 -2,000 m. The reaction turbine is further subdivided into the Francis type, which is characterized by a radial flow impeller, and the Kaplan or propeller type, which is an axial-flow machine. In the sections that follow, each type of hydraulic turbine will be studied separately in terms of the velocity triangles, efficiencies, reaction, and method of operation.