Small-Signal Stability Analysis of The Hydrokinetic Energy Harnessing connected to The Grid

This paper presents the modelling of the hydrokinetic system for the small-signal stability analysis under the small disturbances due to variation and fluctuation of water velocity in the river or marine. The complete modelling of the hydrokinetic system consists of vertical axis H-Darrieus turbine, direct-drive permanent magnet synchronous generator (PMSG), back-to-back converter and the grid network. By linearising all the equation around the steady-state value, the dynamic equation of the hydrokinetic system is derived. The stability of the system is tested with and without the PI controller. The eigenvalues analysis-based approaches have been used to investigate the stability of the system under the small disturbances. The findings show, the stability of the hydrokinetic system with PI controller is improved up to 57.82% by reducing the oscillation frequency at the Rotor Side Converter (RSC)

Maximum power point tracking control of hydrokinetic turbine and low-speed high-thrust permanent magnet generator design

River-based hydrokinetic turbine power generation systems have been studied to introduce an effective energy flow control method. Hydrokinetic turbine systems share a lot of similarities with wind turbine systems in terms of physical principles of operation, electrical hardware, and variable speed capability for optimal energy extraction. A multipole permanent magnet synchronous generator is used to generate electric power because of its ability to reach high power density and high thrust at low speed. A 3-phase diode rectifier is used to convert AC power from the generator into DC power and a boost converter is used to implement energy flow control. On the load side, an electronic voltage load is used for test purposes to simulate a constant DC bus voltage load, such as a battery. A dynamic model of the entire system is developed and used to analyze the interaction between the mechanical structure of water turbine and electrical load of the system, based on which a maximum power point tracking control algorithm is developed and implemented in the boost converter. Simulation and experimental results are presented to validate the proposed MPPT control strategy for hydrokinetic turbine system. Similar to the wind turbine system, hydrokinetic turbine system usually requires a gear box to couple the turbine and the generator because the operating speed range for the hydrokinetic turbine is much lower than the operating speed range for most PMSGs. However, the gear box coupling adds additional transmission power losses. Therefore a high-thrust low-speed permanent magnet synchronous generator is designed to couple with the water turbine without a gear box --Abstract, page iii

Modeling and Control of Diesel-Hydrokinetic Microgrids

A large number of decentralized communities in Canada and particularly in Québec rely on diesel power generation. The cost of electricity and environmental concerns suggest that hydrokinetic energy is a potential for power generation. Hydrokinetic energy conversion systems (HKECSs) are clean, reliable alternatives, and more beneficial than other renewable energy sources and conventional hydropower generation. However, due to the stochastic nature of river speed and variable load patterns of decentralized communities, the use of a hybrid diesel- hydrokinetic (D-HK) microgrid system has advantages. A large or medium penetration level has a negative effect on the short-term (transient) and long-term (steady-state) performance of such a hybrid system if the HKECS is controlled based on conventional control schemes. The conventional control scheme of the HKECS is the maximum power point tracking (MPPT). In the long-term conditions, the diesel generator set (genset) can operate at a reduced load where the role of the HKECS is to reduce the electrical load on the diesel genset (light loading). In the short-term, the frequency of the microgrid can vary due to the variable nature of water speed and load patterns. This can lead to power quality problems like a high rate of change of frequency or power, frequency fluctuations, etc. Moreover, these problems are magnified in storage-less DHK microgrids where a conventional energy storage system is not available to mitigate power as well as frequency deviations by controlling active power. Therefore, developing sophisticated control strategies for the HKECS to mitigate problems as mentioned above are necessary. Another challenging issue is a hardware-in-the-loop (HIL) platform for testing and developing a D-HK microgrid. A dispatchable power controller for a fixed-pitch cross-flow turbine-based HKECS operating in the low rotational speed (stall) region is presented in this thesis. It delivers a given power requested by an operator provided that the water speed is high enough. If not, it delivers as much as possible, operating with an MPPT algorithm while meeting the basic operating limits (i.e., generator voltage and rotor speed, rated power, and maximum water speed), shutting down automatically if necessary. A supervisory control scheme provides a smooth transition between modes of operation as the water speed and reference power from the operator vary. The performance of the proposed dispatchable power controller and supervisory control algorithm is verified experimentally with an electromechanical-based hydrokinetic turbine (HKT) emulator. The permanent magnet synchronous generator (PMSG) is preferred in small HKECSs. So, a converter-based PMSG emulator as a testbed for designing, analyzing, and testing of the generator’s power electronic interface and its control system is developed. A 6-switch voltage source converter (VSC) is used as a power amplifier to mimic the behaviour of the PMSG supplying linear and non-linear loads. Technical challenges of the PMSG emulator are considered, and proper solutions are suggested. Finally, an active power sharing control strategy for a storage-less D-HK microgrid with medium and high penetration of hydrokinetic power to mitigate: 1) the effect of the grid frequency fluctuation due to instantaneous variation in the water speed/load, and 2) light loading operation of the diesel engine is proposed. A supplementary control loop that includes virtual inertia and frequency droop control is added to the conventional control system of HKECS in order to provide load power sharing and frequency support control. The proposed strategy is experimentally verified with diesel engine and HKT emulators controlled via a dSPACE® rapid control prototyping system. The transient and steady-state performance of the system including grid frequency and power balancing control are presented

Modelling and control strategies for hydrokinetic energy harnessing

The high prices and depletion of conventional energy resources and the environmental concern due to the high emission of CO2 gases have encouraged many researchers worldwide to explore a new field in renewable energy resources. The hydrokinetic energy harnessing in the river is one of the potential energies to ensure the continuity of clean, reliable, and sustainable energy for the future generation. The conventional hydropower required a special head, lots of coverage area, and some environmental issues. Conversely, the hydrokinetic system based on free stream flowing is one of the best options to provide the decentralised energy for rural and small-scale energy production. Lately, the effort of energy harnessing based on hydrokinetic technology is emerging significantly. Nevertheless, several challenges and issues need to be considered, such as turbine selection for energy conversion, generalised turbine model and control strategies for the grid and non-grid connection. To date, no detailed information on which turbines and turbine model are most suited to be implemented that match Malaysia’s river characteristics. Besides, a large oscillation has occurred on the output current and power during dynamic steady state due to the water variation and fluctuation in the river. Hence, reducing the energy extraction and controller efficiency for stand-alone and grid-connected systems, respectively. Therefore, the study aims to analyse the different turbine's design, proposed the turbine model, and propose the potential control strategies for stand-alone and grid-connected hydrokinetic energy harnessing in the river. In this work, three types of vertical axis turbines, including the H-Darrieus, Darrieus, and Gorlov with twelve different NACA and NREL hydrofoils, were analysed using the QBlade and MATLAB software, respectively. The effect of symmetrical and non-symmetrical geometry profiles, hydrofoils thicknesses, and turbine solidities have been compared to choose one of the best option turbines based on the highest power coefficient (CP) and a torque coefficient (CM), respectively. Subsequently, the turbine power model generalised equation has been proposed to represent the hydrokinetic turbine characteristic using a polynomial estimation equation. On the other hand, the MPPT control strategy is employed for the off-grid system using the sensorless method. The circuit topology based on an uncontrolled rectifier with the DC boost converter is implemented to regulate the rectifier output voltage through duty ratio. Subsequently, the metaheuristic method based on the combination of the Hill-Climbing Search (HCS) MPPT algorithm and the Fuzzy Logic Controller has been proposed to produce a variable step size compared to the fixed step size in conventional HCS algorithm. On the contrary, the dynamic model of the grid-connected hydrokinetic system has been linearised for small-signal stability analysis. The eigenvalues analysis-based approached has been applied to evaluate the system stability due to the small disturbance. The PI controller with the eigenvalues tracing method has been proposed to improve the system stability by reducing the oscillation frequency. The research outcomes indicated that the H-Darrieus with NACA 0018 was the best turbine for energy conversion in the river. Besides, the HCS-Fuzzy MPPT algorithm improved the energy extraction up to 88.30 % as well as reduced 74.47 % the oscillation compared to the SS-HCS MPPT. The stability of grid-connected hydrokinetic energy harnessing was improved up to 63.63 % by removing the oscillation frequency at states of λ8,9,10,11 as well as reducing 40.1 % oscillation of the generator stator current at the rotor side controller (RSC)

Ocean Energy in Belgium - 2019

B

ANÁLISE DE SISTEMA HIDROCINÉTICO COMO CONVERSÃO DE ENERGIA PARA BOMBEAMENTO DE ÁGUA

Como uma alternativa sustentável para a geração de energia elétrica, a energia hidrocinética é capaz de converter a energia cinética dos rios ou corrente marinhas em energia elétrica. A partir disso, este artigo tem como objetivo apresentar uma revisão de literatura, acerca da relação de informações práticas e conhecimento científico, a fim de maximizar os estudos acerca do tema apresentado e contribuir com informações sobre a utilização de energias renováveis aplicadas ao bombeamento de água, discorrendo os componentes do sistema hidrocinético de geração de energia, fatores de desempenho e vantagens aplicados ao bombeamento de agua. Assim, o sistema hidrocinético contribui para a eliminação do uso de combustíveis fósseis e soluções renováveis, dando acesso à energia elétrica em locais remotos

Experimental evaluation of a mixer-ejector hydrokinetic turbine at two open-water test sites and in a tow tank

For marine hydrokinetic energy to become viable it is essential to develop energy conversion devices that extract energy with high efficiency, and to field-test them in an environment similar to the one in which they are designed to eventually operate. FloDesign Inc., with FloDesign Wind Turbine Corp., developed a Mixer-Ejector Hydrokinetic Turbine (MEHT) that encloses the turbine in a specially designed shroud to increase mass flow through the turbine rotor. A scaled version of this turbine was evaluated experimentally at two open-water tidal energy test sites, and in a tow tank. State-of-the-art instrumentation was used to measure free stream and wake velocities, turbine power extraction, test platform loadings and platform motion induced by sea state. The MEHT was able to generate power from tidal currents over a wide range of conditions, with low-velocity start-up. The decay of the wake velocity deficit was found to improve with increasing free stream turbulence

Pengaruh Penambahan Diffuser terhadap Performa 3D Print Turbin Hidrokinetik Helical Savonius (Twist Angle 45o)

Energi potensial dan energi kinetik air merupakan salah satu bentuk energi terbarukan yang sangat potensial dan terus dikembangkan di Indonesia. Tenaga hidro (hydropower) adalah energi yang diperoleh dari air yang mengalir. Potensi energi yang dimiliki air dapat dimanfaatkan dan dirubah ke dalam wujud energi lain seperti energi mekanis dan energi listrik. Teknologi yang memanfaatkan tenaga hidro yang berasal dari arus sungai, saluran irigasi dan lautan ini sering disebut sebagai teknologi hidrokinetik yang merupakan jenis tenaga hidro terbaru. Teknologi ini dapat berfungsi secara efektif pada kecepatan air yang rendah bahkan pada kecepatan air 1 m/s. Teknologi ini cocok dimanfaatkan di desa terpencil yang posisinya di tepi sungai dengan sudut elevasi yang rendah. Pemasangan teknologi hidrokinetik yang mudah yaitu  dengan memasukan bodi turbin secara mengapung. Cara penempatan bodi seperti ini yang menyebabkan biaya instalasi lebih murah dibanding turbin air lain ( kaplan, francis dan lain – lain) maupun sumber energi angin dan energi surya.                 Turbin jenis Savonius dipilih karena beberapa kelebihan, antara lain biaya manufaktur rendah, mampu berputar pada kecepatan air yang rendah, mampu menerima aliran air dari segala arah dan memiliki starting awal yang mudah. Untuk peningkatan performa turbin Savonius dipilih profil sudu yang tepat dan penambahan diffuser. Dalam penelitian ini dipilih profil sudu tipe helical savonius. Kelebihan turbin jenis helical savonius rotor ini memiliki nilai positif pada nilai koefisien torsi statis, sedangkan pada jenis turbin savonius biasa memiliki nilai koefisien torsi statis negatif pada 1350-1650 dan 3150-3450 dalam satu siklus 3600. Penelitian ini bertujuan untuk mengetahui performa turbin angin helical savonius pada sudut puntir 450 jika diterapkan menjadi turbin hidrokinetik. Selain itu penelitian ini juga dilakukan dengan menambahkan diffuser pada sisi inlet yang bertujuan untuk lebih meningkatkan efisiensi turbin bila dibandingkan dengan tanpa penambahan diffuser. Penelitian dilakukan secara eksperimen, diuji pada beberapa variasi angka Reynold antara lain 1,2×〖10〗^5 (V = 0,6 m/s); 1,5×〖10〗^5  (V= 0,75 m/s) dan 1,8×〖10〗^5 (V= 0,9 m/s). Peneliti menguji pada kecepatan air rendah agar dapat diaplikasikan di sungai maupun saluran irigasi

Multivariable control of a grid-connected wind energy conversion system with power quality enhancement

This document is the Accepted Manuscript version of the following article: Kaddour Fouad, Houari Merabet Boulouiha, Ahmed Allali, Ali Taibi, and Mouloud Denai, ‘Multivariable control of a grid-connected wind energy conversion system with power quality enhancement’, Energy Systems, Vol. 9 (1): 25-57, February 2018. The final publication is available at Springer via: https://doi.org/10.1007/s12667-016-0223-7This paper proposes the design of a multivariable robust control strategy for a variable-speed WECS based on a SCIG. Optimal speed control of the SCIG is achieved by a conventional PI controller combined with a MPPT strategy. DTC-SVM technique based on a simple Clarke transformation is used to control the generator-side three-level converter in the variable speed WECS. The flow of real and reactive power between the inverter and the grid is controlled via the grid real and reactive currents and the DC link voltage using multivariable H∞ control. The overall WECS and control scheme are developed in Matlab/Simulink and the performance of the proposed control strategy is evaluated via a set of simulation scenarios replicating various operating conditions of the WECS such as variable wind speed and asymmetric single grid faults. The power quality of the WECS system under H∞ control control approach is assessed and the results show a significant improvement in the total harmonic distorsion as compared to that achieved with a classical PI control.Peer reviewedFinal Accepted Versio

Probabilistic engineering analysis and design under time-dependent uncertainty

Time-dependent uncertainties, such as time-variant stochastic loadings and random deterioration of material properties, are inherent in engineering applications. Not considering these uncertainties in the design process may result in catastrophic failures after the designed products are put into operation. Although significant progress has been made in probabilistic engineering design, quantifying and mitigating the effects of time-dependent uncertainty is still challenging. This dissertation aims to help build high reliability into products under time-dependent uncertainty by addressing two research issues. The first one is to efficiently and accurately predict the time-dependent reliability while the second one is to effectively design the time-dependent reliability into the product. For the first research issue, new time-dependent reliability analysis methodologies are developed, including the joint upcrossing rate method, the surrogate model method, the global efficient optimization, and the random field approach. For the second research issue, a time-dependent sequential optimization and reliability analysis method is proposed. The developed approaches are applied to the reliability analysis of designing a hydrokinetic turbine blade subjected to stochastic river flow loading. Extension of the proposed methods to the reliability analysis with mixture of random and interval variables is also a contribution of this dissertation. The engineering examples tested in in this work demonstrate that the proposed time-dependent reliability methods can improve the efficiency and accuracy more than 100% and that high reliability can be successfully built into products with the proposed method. The research results can benefit a wide range of areas, such as life cycle cost optimization and decision making --Abstract, page iv