Tidal Energy Conversion System Research Articles

A maximum power point tracking control strategy of tidal energy conversion system based on fixed-time observer technology

To achieve maximum tidal current energy capture in complex and harsh marine environments, this paper proposes a nonlinear control based on fixed-time observer (NCFTO) for tidal energy conversion system (TECS). The TECS operating in the ocean not only needs to face time-varying ocean current speed, but also needs to consider the adverse effects brought by parameter uncertainties and unknown disturbances in actual operation. Considering the high nonlinearity of TECS, conventional linear control systems may not necessarily provide satisfactory performance. Therefore, the NCFTO takes into account the TECS parameter uncertainties and unknown disturbances in its design. This mainly involves using a designed fixed-time observer to accurately estimate a concentrated disturbance term containing TECS nonlinearities, parameter uncertainties, disturbances in real time, and offsetting the adverse effects of actual disturbances on the control system. Meanwhile, a linear controller is designed based on the linearization of TECS to ensure satisfactory performance of NCFTO under time-varying ocean current speed, thus laying a solid foundation for achieving maximum tidal current energy capture. In addition, to verify the feasibility and effectiveness of NCFTO, three simulation testing scenarios have been set up, namely time-varying ocean current speed, rotor inertia uncertainty, and unknown disturbance torque.

TSR-Based optimization using auxiliary motor in Tidal Energy Conversion System: An experimental study

The fluctuating nature of renewable energy is one of the factors that reduces its ability to compete with traditional forms of power generation. In the context of ocean current energy, tidal oscillations are the primary reason for the average power generation being significantly lower than the designed value. Increasing energy production through optimization is necessary for ocean current energy to compete successfully in the market. This experimental study is intended to increase electrical power production through electromechanical engineering with tip speed ratio (TSR) control using auxiliary motors, and adapts the Motor Generator Pair (MGP) approach, where the generator and motor are connected in series. A physical model of a Tidal Energy Conversion System (TECS) was developed. The system consists of a turbine simulator in the form of an AC motor with separate torque and speed controls, torque sensors, a hydraulic transmission system, and auxiliary motors. With this system, a typical tidal turbine profile was built and simulated TSR-based optimization control. The results of this optimization control show that power production can be increased through optimal tip-speed ratio control.

Performance Evaluation of Hydrostatic Transmission Systems in Tidal Energy Conversion

The growing need for renewable energy has brought oceancurrent energy’s promise as a consistent and ecologically benign source front stage. One can effectively harness this energy with tidal energy conversion systems (TECS). This work examined the performance of a hydrostatic transmission (HST) system in a prototype tidal stream power producing configuration. Comprising a turbine simulator, hydraulic transmission, and permanent magnet synchronous generator (PMSG) with torque, power, and speed sensors, the experimental setup Under different torque settings, tests were performed to assess if the system could separate submerged components from those above sea level and improve rotational speed. According to the findings, the HST system has rather poor efficiency, averaging about 22%, even as it delivers the intended speed gain. Efficiency loss results from elements including hydraulic fluid viscosity, internal wear, and shaft alignment. These results highlight the need of more study to maximize HST systems for improved dependability and performance in tidal energy uses.

Hyper Spherical Search (HSS) Algorithm Based Optimization and Real-Time Stability Study of Tidal Energy Conversion System

Hyper Spherical Search (HSS) Algorithm Based Optimization and Real-Time Stability Study of Tidal Energy Conversion System

Learning From Field Testing Experiences for Developing Small Scale Tidal Current Energy Conversion System

Tidal current energy conversion system (TCECS) has been tested in potential straits such as the Larantuka Strait and Madura Strait. In its development, the technology will be improved by increasing its capacity to 100 kW. The new capacity is planned to use a farming system with vertical axis turbines. The experience of installing and operating a TCECS prototype with a capacity of 10-20 kW in Indonesia could be a valuable experience for the implementation phase of a TCECS with a higher capacity. This paper aims to report the experience of TCECS installation in Indonesia. According to previous installation experience, TCECS was made floating using a catamaran type as a supporting structure. This was done to facilitate the transportation process from the production site to the installation site. TCECS production was carried out in an area that is quite far from the installation area because there is not enough land around it to assemble or produce the technology. This condition is one of the factors that need to be considered in the TCECS installation step in Indonesia. Another factor to consider is the size of the TCECS technology to be utilized. The Installation facilities in Indonesia, especially in the eastern region, have been yet inadequate in using large equipment, e.g., a heavy crane. Therefore, the dimensions of the TCECS to be installed should not have large dimensions. To take the experience of the installation, other factors are described in several chapters in this paper.

Performance Evaluation Of Permanent Magnet Synchronous Generator (PMSG) On Tidal Power Generation Optimization

In a tidal current energy generation system, optimization of power generation can be done through turbine design, system design, and control of mechanical transmission from the turbine to the generator, as well as from the aspect of electronic generator output control. This research aims to analyze the performance of the PMSG generator from a prototype of the tidal current energy power plant. Turbine rotation is simulated using an ac motor equipped with an ac drive that supports separate speed and torque control. The hydraulic transmission system consists of a pump and a hydraulic motor that transfers the rotation of the turbine to the generator, where the power output is observed with variations in turbine speed and torque. The results indicate that the transmission system has worked well in transmitting the turbine’s mechanical power and increasing the rotational speed. The decrease in speed with increasing load and low average efficiency (less than 20%) occurs, mainly due to the characteristics of the generator being tested. The generator has a large rated torque requirement of 32 Nm, which is much higher than the main drive capacity of the turbine simulator. The design of a tidal energy conversion system, in which the tidal current speed fluctuates, requires careful selection of the generator, not only from the aspect of power capacity and rated rotational speed, but also from the initial torque value and required rated torque.

Dynamics analysis of the power train of 650 kW horizontal-axis tidal current turbine

Power trains are an important component of the tidal current energy conversion systems; however, the variable drive-torque and unbalanced moments produced by flow shear and turbulence cause power trains to vibrate. When the scale of the tidal current turbine increases, the vibration problem becomes prominent. The dynamic characteristics of power trains are complex. In this study, the power train of a 650 kW horizontal-axis tidal current turbine was studied. The power train adopted a low-speed-ratio semi-direct drive scheme proposed by Zhejiang University. A mathematical model of the power train was constructed. The influence of external excitations (including tidal current condition, unbalanced moments, and internal excitation) on dynamic characteristics was studied using simulations and sea trials. The simulation results showed that the radial and torsional vibrations of the low- and the high-speed shafts increased when the tidal current velocity increased. The fluctuation range of the bearing load increased under increases in the pitch and yaw moments. The meshing motion of the planetary gear plays a leading role in the vibration of low- and high-speed shafts. The power train model was validated by comparing the results of the experiment and simulation.

EMR modelling of tidal turbines integrated into Orkney grid

The main challenges for renewable energy integration in electrical grid system are their variability and prediction. Tidal renewable energy is considered low variability in comparison to wind energy generation and due to tides regular periodicity, it is often quoted as predictable. This paper presents the modeling of Orkney's distribution network with the integration of tidal energy. This multi-physics model is based on the graphical formalism tool, Energetic Macroscopic Representation (EMR). This tool has been used to analyze the Tidal energy conversion (TEC) system based on the behavior of permanent magnet synchronous machine (PMSM). The daily, monthly and yearly variations of marine water speed in Orkney were observed. The EMR has been efficiently used in the representation of Orkney energy system integration of Orbital O2 tidal systems, and showing its effectiveness to adopt the control strategy. More precisely, the data of current water profile for 2009 has been chosen from 10 years big data to test the adopted deduced control technique. The methodology of this tool is described in details and the simulation results obtained in MATLAB environment are presented.

An Improvement on Slot Configuration Structure of a Low-Speed Surface-Mounted Permanent Magnet Synchronous Generator with a Wound Cable Winding

This paper are concentrated on low-speed surface-mounted permanent magnet synchronous generator (LS-SMPMSG) electromagnetic design using finite-element (FEM)-based method. Introduced LS-SMPMSG as an important generator in the industry is utilized in marine energy conversion (MEC) and tidal energy conversion (TEC) systems. The main feature of the designed LS-SMPMSG exhibited is its ability to generate electrical power in MEC and TEC systems at a low speed of approximatively 100 rpm. In this paper, a new slot structure for LS-SMPMSG has been proposed to enhance the LS-SMPMSG performance. The FEM analysis and comparing results shows that the new slot structure reduced the torque ripple and the cogging torque equal to 19.54% and 87.5%. respectively. Also, it influenced the LS-SMPMSG Joule losses by reducing it close to 16.1%. Another advantage of the new slot structure of LS-SMPMSG is its easy construction and assembly. The FEM analysis as a powerful method validates the advantages of the proposed structure.

Resource Assessment of Tidal Stream Power in Pakiputan Strait, Davao Gulf, Philippines

During the last years, there are ongoing efforts on the development of tidal energy conversion systems in the Philippines. This study conducts tidal energy resource assessment in the Pakiputan Strait following a methodology outlined as stage 2a tidal resource assessment published by the European Marine Energy Centre (EMEC). The study assessed the preliminary results of the tidal velocities at Pakiputan Strait with a mean spring peak velocity (Vmsp) of 1.7m/s at 3m from the water surface from 15 days of continuous data collection using a seabed-mounted acoustic Doppler current profiler. This corresponded to an estimated Annual Energy Production (AEP) of 1350kWh/y for 1m2 of capture area of the generic device. Sensitivity analysis showed that the spatial distribution of hydrodynamic model results does not vary significantly with variations in certain input parameters. It further showed that a 10% decrease in the nominal value of Vmsp on-site led to a 15% decrease in the nominal value of AEP, while a 10% increase in the nominal value of Vmsp led to a 30% increase in the nominal value of AEP, assuming that the considered Vmsp still corresponded to the velocity distribution from observations. A static survey and the use of computational fluid dynamics modeling are recommended to further enhance the analysis of the study.

An FTC Design via Multiple SOGIs with Suppression of Harmonic Disturbances for Five-Phase PMSG-Based Tidal Current Applications

This paper firstly adopts a fault accommodation structure, a five-phase permanent magnet synchronous generator (PMSG) with trapezoidal back-electromagnetic forces, in order to enhance the fault tolerance of tidal current energy conversion systems. Meanwhile, a fault-tolerant control (FTC) method is proposed using multiple second-order generalized integrators (multiple SOGIs) to further improve the systematic fault tolerance. Then, additional harmonic disturbances from phase current or back-electromagnetic forces in original and Park’s frames are characterized under a single-phase open condition. Relying on a classical field-oriented vector control scheme, fault-tolerant composite controllers are then reconfigured using multiple SOGIs by compensating q-axis control commands. Finally, a real power-scale simulation setup with a gearless back-to-back tidal current energy conversion chain and a small power-scale laboratory prototype in machine side are established to comprehensively validate feasibility and fault tolerance of the proposed method. Simulation results show that the proposed method is able to suppress the main harmonic disturbances and maintain a satisfactory fault tolerance when third harmonic flux varies. Experimental results reveal that the proposed model-free fault-tolerant design is simple to implement, which contributes to better fault-tolerant behaviors, higher power quality and lower copper losses. The main advantage of the multiple SOGIs lies in convenient online implementation and efficient multi-harmonic extractions, without considering system’s model parameters. The proposed FTC design provides a model-free fault-tolerant solution to the energy harvested process of actual tidal current energy conversion systems under different working conditions.

Energy-Based Combined Nonlinear Observer and Voltage Controller for a PMSG Using Fuzzy Supervisor High Order Sliding Mode in a Marine Current Power System

A permanent magnet synchronous generator (PMSG) in s grid-connected tidal energy conversion system presents numerous advantages such as high-power density and ease of maintenance. However, the nonlinear properties of the generator and parametric uncertainties make the controller design more than a simple challenge. Within this paper we present a new combined passivity-based voltage control (PBVC) with a nonlinear observer. The PBVC is used to design the desired dynamics of the system, while the nonlinear observer serves to reconstruct the measured signals. A high order sliding-mode based fuzzy supervisory approach is selected to design the desired dynamics. This paper addresses the following two main parts: controlling the PMSG to guarantee the maximum tidal power extraction and integrate into to the grid-side converter (GSC), for this the new controller is proposed. The second task is to regulate the generated reactive power and the DC-link voltage to their references under any disturbances related to the machine-side converter (MSC). Furthermore, the robustness of the controller against parameter changes was taken into consideration. The developed controller is tested under parameter variations and compared to benchmark nonlinear control methods. Numerical simulations are performed in MATLAB/Simulink which clearly demonstrates the robustness of the proposed technique over the compared control methods. Moreover, the proposed controller is also validated using a processor in the loop (PIL) experiment using Texas Instruments (TI) Launchpad.

Robust energy‐based nonlinear observer and voltage control for grid‐connected permanent magnet synchronous generator in the tidal energy conversion system

Robust energy‐based nonlinear observer and voltage control for grid‐connected permanent magnet synchronous generator in the tidal energy conversion system

Development of a 300 kW horizontal-axis tidal stream energy conversion system with adaptive variable-pitch turbine and direct-drive PMSG

The adaptation to changes in flow direction is the premise to harness the bidirectional flow energy for a tidal stream turbine. Present studies usually aim at active variable-pitch or steering with dynamic sealing to carry out this task. In this paper, a 300 kW horizontal-axis tidal stream energy conversion system with an adaptive variable-pitch turbine and an outer-rotor type PMSG is developed. Based on the BEMT, the principle of the turbine with symmetrical airfoils and backward swept blades to follow the bidirectional flow is presented, and the hydrodynamic performances, such as pitching, starting, power and thrust, are discussed. The encapsulated windings and magnets of the PMSG can expose to the seawater, and the output characteristics are analyzed at different conditions in the factory. Both the turbine and generator are characterized by no dynamic sealing. The experiment results in the field show that the bidirectional flow energy can be extracted effectively, and the generator can work well to output electric power steadily. The hydrodynamic performances predicted by the modified BEMT meet the design requirements of the 300 kW prototype. The successful field trial of this novel device lays solid support for the utilization of the bidirectional tidal stream energy.

An Active FTC Strategy Using Generalized Proportional Integral Observers Applied to Five-Phase PMSG based Tidal Current Energy Conversion Systems

In recent years, multi-phase permanent magnet synchronous generators (PMSGs) have become attractive in the field of tidal current energy conversion systems (TCECS) due to their high-power density, reliability, and availability. However, external disturbances and malfunctions in power conversion chains will bring challenges to achieving stable and continuous tidal current energy harnessing. Using generalized proportional integral observers, an active fault-tolerant control (AFTC) strategy is therefore proposed for a five-phase PMSG based TCECS that is subjected to an open switch fault (OSF) in the generator side converter. This proposed AFTC strategy is applied into q-axis current control loops, which contain fault detection and compensation. The fault compensator will be smoothly activated using a sigmoid function once the OSF is detected. Finally, a small-scale power experimental platform emulating the TCECS is established in order to verify the feasibility and efficiency of the proposed FTC strategy. Experiment results show that this AFTC strategy can detect faults rapidly and effectively attenuate torque ripples in the post-fault operation mode.

Passivity-based Voltage Controller for Tidal Energy Conversion System with Permanent Magnet Synchronous Generator

Nonlinear dynamical and time varying parameters of the permanent magnet synchronous generator (PMSG), make it difficult to control. This paper presents a new passivity-based control (PBC) of tidal turbine based PMSG, connected to the grid through a back-to-back converter. The control problem is challenging for at least two reasons. First, the dynamics of the conversion system are described by a highly coupled set of nonlinear differential equations and various uncertainties of the PMSG model. Second, it is preferable to operate this kind of systems at the point of maximum power, which is a nonlinear function. To this end, two kinds of control strategies have been used. A new passivity-based voltage controller (PBVC) design applied to the machine-side, that ensures asymptotic convergence to the MPPT is presented. A proportional integral derivative (PID) is added to design a desired torque dynamic in order to guarantee a fast convergence and stability of the closed loop system, which allows to the PMSG to operate at an optimal speed. Secondly, a classical proportional integral (PI) controllers is applied to the grid-side in order to regulate the DC-Link voltage and to deliver only the active power into distribution network. Finally, the obtained simulation results under MATLAB/Simulink, show that the proposed control strategy ensures stability and fast response of the DC-link voltage and the reactive power generated is extremely minimized.

Effects of demi-hull separation ratios on motion responses of tidal current turbines-loaded catamaran

Catamaran has recently been a choice to support a typical vertical axis turbine in floating tidal current energy conversion system. However, motion responses associated with the catamaran can reduce the turbines efficiency. The possibility to overcome this problem is to change the catamaran parameter by varying and simulating the demi-hull separations to have lower motion responses. This simulation was undertaken by Computational Fluid Dynamic (CFD) using potential flow analysis. Cases of demi-hull separation were considered, with ratios of demi-hull separation (S) to the breadth of demi-hull (B), S⁄B of 3.45, 4.95, 6.45, 7.2 and 7.95. In order to compare to the previous works in the literature, the regular wave was set with wave height of 0.8 m. Furthermore, the analysis was carried out by irregular waves with significant wave height, Hs, of about 0.09 to 1.5 m and the wave period, T, of about 1.5 to 6 s or corresponding to the wave frequency, w, of about 1.1 to 4.2 rad/s. The wave spectrum was derived from the equation of the International Towing Tank Conference (ITTC). For the case of turbines-loaded catamaran under consideration, the new finding is that the least significant amplitude response can be satisfied at the ratio S⁄B of 7.2. This study indicates that selecting a right choice of demi-hull separation ratio could contribute in reducing motion responses of the tidal current turbines-loaded catamaran.

Stability and optimisation of direct drive permanent magnet synchronous generator based tidal turbine

Magnetic materials have become more and more user friendly in recent days particularly in an electronic based infrastructure. The study proposes a direct drive permanent magnet based Synchronous Generator as Tidal turbine in a hybrid tidal wave energy conversion system (TWECS) and discusses its performance for better stability. The objective of the study is to analyse the role of permanent magnet based generator in TWECS for overall improvement of stability through reactive power management. The isolated TWECS becomes unstable either by random load variations or by non uniform wind and tidal power inputs. Consequently the overall stability of the TWECS is brought to stable and normal stage by the control of reactive power with the inclusion of the custom power based devices. In addition to the effects of permanent magnet in case of DDPMSG for improving the overall system stability, optimisation tools like PSO, GSA and PSOGSA are added for further improvement in system performance.

Assessment of Energy Production Potential from Tidal Stream Currents in Morocco

Energy extracted from the ocean can provide a source of regular and foreseeable electrical production at higher energy densities than any other renewable energy resource. The marine current resource is potentially great and is focused in several sites around the world. The knowledge of the energy potential, its constraints and availability are all prerequisites to determine the possibilities for the implementation of infrastructure to produce energy. They are also required to anticipate the structuring of energy routes and to respond to increasing technological needs. Several Moroccan regions want to take advantage by their coastal domain and play a role in the development of the tidal energy sector. They also want to benefit from the associated economic advantages knowing that the Mediterranean coast length is 550 km and the Atlantic length is 3000 km, respectively. The Copernicus Marine Service ocean products provide key input for such technologies, as they can be employed to help evaluate the accessible ocean energy devices and choose the most attractive sites to exploit the tidal energy projects in Morocco. The goal of this research was to evaluate and analyze the tidal marine current resource at the sites which are potentially suitable for the installation of Horizontal Axis Marine Current Turbines in Morocco. Distributions of available power of tidal energy in the Moroccan region are provided, and three possible areas are suggested for installing tidal energy conversion systems.

Integrated design and implementation of 120-kW horizontal-axis tidal current energy conversion system

A pragmatic and detailed sequence for the integrated design and implementation of a 120-kW horizontal-axis tidal current energy conversion system is presented, thus offering a valuable experience that contributes to the progress of tidal energy systems. The overall design of a full-scale system, containing the system design, control concept, and sea trial is provided in its entirety. The system design includes the turbine, pitch system, mechanical drive train, and electrical system. The blade parameters, hydrofoil data, and detailed structures of these electromechanical systems are shown. The control concept, comprising the grid-connected, maximum power point tracking (MPPT), and pitch controls, is proposed according to the analysis of the output power characteristic of the tidal energy system operation. The main objectives include confining the captured power at its rated value for protection when the rated current velocity is exceeded, capturing the maximum power below the rated current velocity, and regulating the active and reactive power to ensure electric power quality. A workshop test and a sea trial are carried out. The in situ experimental results of a complete operating period validated the effectiveness and feasibility of the entire system design, control concept, and experimental method.