Tidal Current Generation Research Articles

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.

Advancement of Tidal Current Generation Technology in Recent Years: A Review

Renewable energy provides an effective solution to the problem existing between energy and environmental protection. Tidal energy has great potential as a form of renewable energy. Tidal current generation (TCG) technology is the earliest renewable energy power generation technology. The advancement of science and technology has led to TCG rapidly developing since its emergence in the last century. This paper investigates the development of TCG in recent years based on the key components of TCG systems, both in terms of tidal energy harvesting research and power generation unit research. A summary of tidal energy harvesting is presented, investigating the main tidal energy harvesting units currently available. In addition, research on generators and generator control is summarized. Lastly, a comparison between horizontal and vertical axis turbines is carried out, and predictions are made about the future trends in TCG development. The purpose of this review is to summarize the research status and research methods of key components in tidal energy power generation technology and to provide insight into the research of tidal energy-related technologies.

A Multiple Time Scales Rolling Coordinative Dispatching Method for an Island Microgrid with High Proportion Tidal Current Energy Access and Demand Response Resources

Currently, the ocean energy strategy is rapidly developing, and a high proportionate tidal current energy grid connection presents significant obstacles to the planning and secure and stable operation of an island microgrid. For an island microgrid with high proportion tidal current energy access and demand response resources, this research suggests a multiple time scales rolling coordinative dispatching method. An MPPT control based on Q-Learning algorithm is first developed for real-time maximum power tracking of tidal current energy generation after the island microgrid’s topology has been examined. Following that, a multiple time scales rolling coordinative dispatching’s fundamental architecture and implementation method are provided, with equal time intervals coordinated in a step-by-step recursive way. In the example analysis of an island microgrid, we consider the rigid demand load that does not participate in the demand side response, and the ship load and controllable load that participate in the demand side response. On sea islands, ship loads on the long timeframe achieve traffic and energy interaction, and dispatchable loads on the short timescale participate in supply and demand balancing. This is due to the multiple time scales properties of demand response resources. In addition, a multiple time scales rolling coordinative dispatching model for an island microgrid is developed. It includes day-ahead, intraday, and real-time components. Finally, example analysis is used to confirm the dispatching method’s usefulness and advancement, and we conclude that the tidal current energy consumption rate of the island microgrid is increased by 17.08%.

Design and Simulation Analysis of Low-speed Tidal Current Energy Generator

Abstract As a kind of ocean energy, tidal energy is mainly caused by the flow of seawater accompanied by tidal phenomena. Tidal current power generation uses the rising and falling ocean currents to impinge on the impeller device of the turbine to rotate the impeller to generate electricity. Tidal current power generation has gradually attracted the attention of countries all over the world in recent decades because of its clean, strong regularity, and high energy density.This paper designs the magnetic circuit structure of a low-speed tidal current generator prototype with a rated power of 1KW, selects a suitable electromagnetic topology, initially determines the generator material and electromagnetic structure, and then uses finite element analysis software to conduct a two-dimensional simulation analysis of the generator. The results show that the current, voltage, and power of the prototype meet the design requirements, and the transient no-load and load analysis is completed. The parameters of the generator are verified to be within a reasonable range to ensure the stable operation of the generator.

MPPT of Permanent Magnet Synchronous Generator in Tidal Energy Systems Using Support Vector Regression

In this paper, an improved Maximum Power Point Tracking (MPPT) algorithm for a tidal power generation system using a Support Vector Regression (SVR) is proposed. To perform this MPPT, a tidal current speed sensor is needed to track the maximum power. The use of these sensors has a lack of reliability, requires maintenance, and has a disadvantage in terms of price. Therefore, there is a need for a sensorless MPPT control algorithm that does not require information on tidal current speed and rotation speed that improves these shortcomings. Sensorless MPPT control methods, such as SVR, enables the maximum power to be output by comparing the relationship between the output power and the rotational speed of the generator. The performance of the SVR is influenced by the selection of its parameters which is optimized during the offline training stage. SVR has a strength and better response than the neural network since it ensures the global minimum and avoids being stuck at local minima. This paper proposes a high-efficiency grid-connected tidal current generation system with a permanent magnet synchronous generator back-to-back converter. The proposed algorithm is verified experimentally and the results confirm the excellent control characteristics of the proposed algorithm.

Analytical Models for Fast and Accurate Calculation of Electromagnetic Performances of Segmented Permanent Magnet Synchronous Machines with Large Angular Gaps

In this paper original analytical models to determine the electromagnetic performances of segmented permanent magnet synchronous machines (with removed active parts in the stator or the rotor) are presented. These models are adapted to PMSM with large air gap width, large diameter, a high number of poles and large angular gaps. This method based on analytical approach is validated by comparizon with a 2D Finite Element calculation (Altair FluxTM 2D) for the specifications of a large diameter, low speed tidal high power current turbine generator. The presented method allows fast and accurate evaluation of the performances of this kind of particular machine and can be used in a systematic design process.

A radial-grouping-based planning method for electrical collector systems in tidal current generation farms

This paper proposes a radial-grouping-based planning method for the electrical collector systems (ECSs) to design the topology and select the cross-sections of ECS submarine cables in tidal current generation farms (TCGFs) while minimizing investment and operation costs. First, an angle-based radial-grouping method is proposed to group the tidal current turbines (TCTs) in a TCGF, considering their capacity limitations while avoiding the trans-region crossing of submarine cables. Second, an optimal planning model is presented to determine the connection scheme for the TCTs within the same group in a TCGF. The investment and trenching costs of submarine cables and ECS power losses are modeled to minimize the comprehensive annual equivalent cost of ECS, while satisfying the submarine cables’ voltage drop and capacity limitation constraints. Third, an efficient solution method is developed by modifying a genetic algorithm with the Prufer number, which retains the ECS radial topology and connectivity with high computational efficiency. Finally, two TCGFs with distinct characteristics in the North Orkney Islands, Scotland, and their measured tidal current data are used to demonstrate the effectiveness, correctness and adaptability of the proposed method.

Effective algorithms of a power converter for tidal current power generation system

This study investigates design procedures and experimental results of power converters for the tidal current power generation system installed at Jin-Do in Korea. The designed power converters consist of a grid-connected converter and a power converter to control the permanent magnet synchronous generator. Many theoretical control algorithms are required to design the power converter for a tidal current power generation system. In this study, the effective algorithm of power converters for a tidal current generation on the phase lock loop algorithm of the grid-connected converter and maximum power point tracking algorithm of generator-side converter was investigated. For the feasibility study of the commercial tidal current power generation system, the down-scaled 20-kW tidal generation system has been installed and empirically evaluated.

Design and comparative survey of high torque coaxial permanent magnet coupling for tidal current generator

This paper presents design and comparative study of high torque coaxial permanent magnet couplings (CPMC) for the use in a tidal current generation (TCG) system. Two different models such as a radial flux-CPMC (RF-CPMC) with magnet retaining rings and a flux concentrating-CPMC (FC-CPMC) with inner and outer rotor yoke changed by retaining rings are analyzed to find the best model under certain design constraint conditions to achieve a minimum pull-out torque of 1.0 kNm. Moreover, the effect of the electromechanical characteristics such as the radial force, stress and deformation are analyzed for both models. Based on the analysis it is found that both RF-CPMC and FC-CPMC are capable of producing the pull-out torque higher than 1.0 kNm, however considering the installation environment and the magnet use, RF-CPMC is selected for prototyping, which is tested using a 3 MW induction motor based dynamometer system to compare its torque production capability with respect to the simulated model. The comparison shows that the prototype is capable of producing the required amount of pull-out torque.

A Tidal Resource Evaluation-Based Method for Tidal Current Generation Farm Allocation Considering the Directionality of Tidal Currents

This article proposes a tidal resource evaluation-based planning method for profitable and reasonable allocations of tidal current generation farms (TCGFs). The directionality and variability of tidal current velocity (TCV) and their correlation are addressed. First, a TCGF power output model is developed. The correlations between tidal current directions and the probability distributions of TCV magnitudes are modeled by rose diagram, and wake effects in TCGFs are simulated by the semi-analytical wake model. Second, a tidal current resource evaluation method is proposed to determine the TCGF's capacity. An optimization planning model is proposed to optimally coordinate tidal current turbine (TCT) micrositing, offshore substation position selection and the ECS planning scheme. The positions of TCTs and substation are modeled by continuous coordinates. The objective is to minimize the levelized cost of energy, subject to the geographical boundary and security operation requirements of the TCGF. Third, the Prufer number-based particle swarm optimization (PN-PSO) algorithm is developed to solve the proposed planning model. The requirements of ECS radial topology and no cable crossings can be fully satisfied. Finally, the measured TCV data collected from Alaska and North Orkney Islands were used to verify the effectiveness and adaptability of the proposed method.

Maximum Power-Point Tracking Control Using Perturb and Observe Algorithm for Tidal Current Generation System

Because wind turbines and tidal current generation rely on irregular wind or tidal speed, maximum power-point tracking (MPPT) control is required in order to generate maximum turbine power. The most common turbine generation is obtained by employing the MPPT scheme using the tip speed ratio (TSR). However, this scheme has a disadvantage in that it relies on the characteristics of tidal current turbines, and it requires expensive tidal current speed-measurement equipment. The tidal current speed measurement is also affected by the installed location and distance to the equipment. To avoid these disadvantages, this paper proposes the maximum power control scheme using perturb and observe (P&O) for tidal current generation systems. The proposed P&O MPPT scheme can generate maximum power regardless of the characteristics of the turbine and the information about the tidal current speed. The reliability and suitability of the proposed scheme are proven using simulation and experiment results at the tidal current generation laboratory in Jin-do, South Korea.

Analysis of Flow Velocity Change in Blade Installed Shroud System for Tidal Current Generation

Analysis of Flow Velocity Change in Blade Installed Shroud System for Tidal Current Generation

An Alterable Weight Minimum Spanning Tree Method for Electrical Collector System Planning in Tidal Current Generation Farms

This paper proposes an alterable weight minimum spanning tree (AW-MST) method to plan electrical collector systems (ECSs) in tidal current generation farms (TCGFs) toward economic objectives. First, a sector-division-based fuzzy c-means (FCM) grouping algorithm is proposed. The tidal current turbines (TCTs) in the TCGF are divided into several sectors by the improved FCM algorithm to relieve the computational burden. Meanwhile, trans-region crossings and overloads of submarine cables can be simultaneously avoided. Second, an ECS planning model is established which fully considers the tidal current velocity (TCV) characteristics and ECS investment and operating costs. Since the variable factors cannot be considered by the common minimum spanning tree algorithms, alterable weights are used in the AW-MST to optimize the variable factors, including power losses and cable types. Finally, the two different TCGFs and the measured TCV datasets collected from North of Orkney, Scotland, were used to verify the effectiveness and adaptability of the proposed method.

Numerical analysis of a tidal current generator with dual flapping wings

Flapping wings, inspired by the mechanism of birds and fish, can act as generators to harvest energy from tidal currents. The hydraulic system is simplified as a spring-damper system to establish the coupling equations relating to the wing motion and the hydrodynamic forces. To provide guidance for design of a fully flow-induced flapping wings energy harvesting system, the behaviors of both system response and energy extraction performance are analyzed using two-dimensional numerical approach. Depending on the rotary actuator radius R, and the volume ratio β between the cylinder and rotary actuator, three distinguishable behaviors are observed in the system response and energy extraction performance. At larger R and smaller β, the dual wings tend to undergo a damped reduction flapping motion because the pitching motion consumes a significant amount of energy. Both decreasing R and increasing β can reduce the energy consumption of the pitching motion, and thus allow the dual wings to achieve a sustainable flapping motion. Although an irregular response can achieve a self-sustained flapping motion, it is unfavorable owing to its unstable power output. The regular response essential for stable energy harvesting is realized over a range of coupling parameters. The energy extraction performance of the system is closely associated with β but also slightly depends on R.

Probabilistic Power Flow Analysis of Power Systems Incorporating Tidal Current Generation

A probabilistic power-flow analysis method for power systems with tidal power sources is presented in this paper. The regularity of tidal power is modeled using a k -means clustering technique and the randomness of tidal power is modeled by using a nonparametric kernel density estimation method. A stochastic sampling method is also developed to generate random samples of tidal power time series for Monte Carlo based probabilistic power-flow analysis. The influence of tidal current generation on power flows is then evaluated and quantified considering both the regularity and randomness of tidal power. The measured tidal current speed data of two different locations in Florida and Alaska states, USA, and the IEEE 57-bus standard test system are used to verify the correctness and effectiveness of the presented probabilistic power-flow analysis method.

日本沿岸潮流発電の資源量推定に対する潮流の長期変動の影響

Tidal currents have two types of intrinsic long-term fluctuations. The one is single tidal constituent such as Ssa and the other one is interferences between tidal constituents. The effect of the long-term fluctuation of tides on the resource assessment for tidal current energy generation system near Japan has been described based on the predictions using data-assimilative global barotropic tide model results. It is shown that monthly mean tidal energy flux varies by more than 20% over a year in the most of the prospective areas. The result indicates the intrinsic long-term fluctuations need to be considered in the resource assessment of tidal current power generation system.

Development of a simple power controller for horizontal-axis standalone tidal current energy generation system

Tidal current energy, which is one of the most predictable forms of ocean renewable energy, is mainly utilised for electricity generation. This paper presents a simple control strategy for an optimal extraction of output power from a horizontal-axis variable speed tidal current turbine generation system with a permanent magnet synchronous generator (PMSG) that is driven directly by a fixed-pitch turbine. The maximum power point tracker (MPPT) extracts the turbine's maximum power from cut-in current velocity to rated value by measuring only dc link parameters. Together with a dc-dc converter PWM controller, MPPT variable-step searching algorithm is modelled and simulated using Matlab/Simulink software. The simulation results indicate that the variable-step searching algorithm can effectively track the maximum power point without collecting the data of tidal current velocity or rotor speed. Such MPPT controller provides a simple and practical method for the maximum power control of standalone tidal current energy conversion system.

진도 울돌목 조류발전 시스템 실증 평가

The empirical evaluation of grid-connected tidal current generation system is presented in this paper. The Ul-dol-mok in Jin-do has been estimated to have tidal power of 1GW. In order to experiment, HAT (Horizontal Axis Turbine) 3-blade and 20kW grid-connected tidal current generation system was established at Ul-dol-mok in Jin-do. To generate power of generator, the speed reference of the PMSG is generated from the Cp curve and TSR (Tip Speed Ratio) of the designed turbine. The control of the converter connected to the grid is controlled to regulate unity power factor. The result showed that the turbine efficiency and system efficiency is 37 % and 31 %. This was achieved that target rate is 30 %, 20 %, respectively.

Properties Variation of Carbon Fiber Reinforced Composite for Marine Current Turbine in Seawater

Turbine blade which are generally made of composite is a core device among components of tidal current power generator that converts the flow of tidal current into a turning force. Recent years, damages of composite turbine blades have been reported due to reasons like seawater degradation, lake of strength, manufacture etc. In this paper, water absorption, tensile, bending, longitudinal transverse shearing properties of carbon fiber reinforced plastic (CRP) composite which would be applied to fabricate the marine current turbine blade has been investigated. Furthermore, the variations of properties with seawater immersion period were studied. The results indicated that the water absorption increased almost linearly at the beginning of immersion and then became stable. Tensile strength of specimen tended to decrease firstly and then recovered slightly. However, the longitudinal transverse shearing strength showed reverse variation trend comparing to tensile strength. And the bending property of specimens was depressed significantly. The properties variations in seawater shall be referenced to design and fabrication of composite marine current turbine blade.

Design of Special Plastic Bearings and Their Application in Renewable Energy Conversion System

To improve the operational reliability of renewable energy conversion system, high-performance polymers and engineering plastics are used to make some parts and components of the energy conversion device, especially in the marine renewable energy generation field. In this article, special plastic bearings based on the material of polyoxymethylene (POM) were designed and applied in the power generation device of both tidal current energy and island wind energy. The properties of POM were analyzed, and the load of a POM ball was tested. Special structures of the plastic bearings were designed to meet the requirements of pressure resistance and to reduce the friction. These plastic bearings had been used in the prototypes of 20 kW tidal current turbine generation device and 15 kW island wind turbine generation device. According to the prototypes’ operation, the results indicate that these plastic bearings work well and are very suitable for the application in renewable energy conversion system. By optimizing the structure, such plastic bearings would be generalized and applied in the renewable energy generation device with a higher power level.