Wave Power Generation System Research Articles

Evaluating the Dependability Measures of a Hybrid Wind–Wave Power Generation System Under Varied Weather Conditions

Evaluating the Dependability Measures of a Hybrid Wind–Wave Power Generation System Under Varied Weather Conditions

Research on Fourier Coefficient-Based Energy Capture for Direct-Drive Wave Energy Generation System Based on Position Sensorless Disturbance Suppression

In order to improve the energy capture efficiency of direct-drive wave power generation (DDWEG) systems and enhance the robustness of the reference power tracking control, a Fourier coefficient-based energy capture (FCBEC) and a position sensorless disturbance suppression (PSDS) control strategy are proposed. For energy capture, FCBEC is proposed to construct the objective function by maximizing the average power over a period of time and expanding the variables in the Fourier basis when the maximum power is captured, which is used as the basis for obtaining the reference trajectory. To address the limitations of the mechanical encoder, the position sensorless technique, based on a sliding mode observer (SMO), is used in the power tracking control, and the position information is obtained through an inverse tangent function. The perturbation caused by the inverse electromotive force error in the system is theoretically analyzed. A full-order terminal sliding mode approach is employed to design a current controller that suppresses the perturbation and ensures accurate tracking of the reference current. Simulation results show that the ocean-wave energy capture strategy proposed in this paper can make the energy captured by the PTO reach the optimal value under the impedance matching condition, and that the response speed and robustness of the full-order terminal sliding mode are better than the traditional PI control.

Research on Maximum Power Control of Direct-Drive Wave Power Generation Device Based on BP Neural Network PID Method

Ocean wave energy is a new type of clean energy. To improve the power generation and wave energy conversion efficiency of the direct-drive wave power generation system, by addressing the issue of large output errors and poor system stability commonly associated with the currently used PID (proportional, integral, and derivative) control methods, this paper proposes a maximum power control method based on BP (back propagation) neural network PID control. Combined with Kalman filtering, this method not only achieves maximum power tracking but also reduces output ripple and tracking error, thereby enhancing the system’s control quality. This study uses a permanent magnet linear generator as the power generation device, establishes a system dynamics model, and predicts the main frequency of irregular waves through the Fast Fourier Transform method. It designs a desired current tracking curve that meets the maximum power strategy. On this basis, a comparative analysis of the control accuracy and stability of three control methods is conducted. The simulation results show that the BP neural network PID control method improves power generation and exhibits better accuracy and stability.

The Energy Conversion and Coupling Technologies of Hybrid Wind–Wave Power Generation Systems: A Technological Review

Based on the mutual compensation of offshore wind energy and wave energy, a hybrid wind–wave power generation system can provide a highly cost-effective solution to the increasing demands for offshore power. To provide comprehensive guidance for future research, this study reviews the energy conversion and coupling technologies of existing hybrid Wind–wave power generation systems which have not been reported in previous publications. The working principles of various wind and wave energy conversion technologies are summarised in detail. In addition, existing energy coupling technologies are specifically classified and described. All aforementioned technologies are comprehensively compared and discussed. Technological gaps are highlighted, and future development forecasts are proposed. It is found that the integration of hydraulic wind turbines and oscillating wave energy converters is the most promising choice for hybrid wind–wave power extraction. DC and hydraulic coupling are expected to become mainstream energy coupling schemes in the future. Currently, the main technological gaps include short their operating life, low energy production, limited economic viability, and the scarcity of theoretical research and experimental tests. The field offers significant opportunities for expansion and innovation.

Study on hydrodynamic characteristics of a hybrid wind-wave energy system combing a composite bucket foundation and wave energy converter

In this paper, a new type of combined wind-wave system is proposed, that is, composite bucket foundation-oscillating buoy (CBF-OB) combined device. A three-dimensional numerical wave flume is established by using the renormalization group k–ε model. The hydrodynamic characteristics around the wave and the combined power generation device are studied. The relationship between wave parameters and wave run-up and wave pressure is analyzed. The absorption efficiency performance of the combined power generation device is evaluated. The results show that in the combined power generation system, the wave run-up and wave pressure at 0°–135° around the CBF are smaller than those in the presence of only CBF, but near 180° the ones are larger than those in the presence of only CBF. In the rear side of the combined power generation system, the smaller the scattering parameters, the more obvious the phenomenon of the second wave peak, and the stronger the nonlinearity of the wave and CBF-OB combined power generation system. The proposed CBF-OB combined power generation device can significantly improve the absorption efficiency of the buoy, which can be increased by about 1.5–4.0 times compared with the absorption efficiency under the action of only the buoy alone. There is an optimal power takeoff parameter, that is, when the damping parameter is 500 N·s/m, to maximize the absorption efficiency of the combined power generation device.

Study on the Dynamic Optimal Control Strategy of an Electric-Hydrogen Hybrid Energy Storage System for a Direct Drive Wave Power Generation System

A direct drive wave power generation system (DDWPGS) has the advantages of a simple structure and easy deployment, and is the first choice to provide electricity for islands and operation platforms in the deep sea. However, due to the off-grid, the source and load cannot be matched, so accommodation is an important issue. Hydrogen storage is the optimal choice for offshore wave energy accommodation. Therefore, aiming at the source-load mismatch problem of the DDWPGS, an electric-hydrogen hybrid energy storage system (HESS) for the DDWPGS is designed in this paper. Based on the characteristics of the devices in the electric-hydrogen HESS, a new dynamic power allocation strategy and its control strategy are proposed. Firstly, empirical mode decomposition (EMD) is utilized to allocate the power fluctuations that need to be stabilized. Secondly, with the state of charge (SOC) of the battery and the operating characteristics of the alkaline electrolyzer being considered, the power assignments of the battery and the electrolyzer are determined using the rule-based method. In addition, model predictive control (MPC) with good tracking performance is used to adjust the output power of the battery and electrolyzer. Finally, the supercapacitor (SC) is controlled to maintain the DC bus voltage while also balancing the system’s power. A simulation was established to verify the feasibility of the designed system. The results show that the electric-hydrogen HESS can stabilize the power fluctuations dynamically when the DDWPGS captures instantaneous power. Moreover, its control strategy can not only reduce the start-stop times of the alkaline electrolyzer but also help the energy storage devices to maintain a good state and extend the service life.

A nonlinear generalized predictive control scheme for the oscillating water column plants

Under unknown waves, the efficiency of the wave energy conversion systems can be improved by applying a novel control algorithm that is able to anticipate the behavior of the plant. In this paper, a generalized predictive control scheme for wave power generation systems that includes a Wells turbine and an induction generator is proposed. The main idea is to maintain the flow coefficient at its optimal point for generated power maximization and, at the same time, improve the efficiency of the Wells turbine and avoid the stalling phenomenon by means of regulating the turbine rotational speed. Moreover, by using the capabilities of the predictive controller, the limitations of the stator current and the effect of the mechanical dead time of the system are integrated into the regulator design process, as well as the flux weakening technique. Simulation and experimental results, through a test bench that has been designed and constructed, show the validity and capability of the proposed scheme in both the rated and flux weakening regimes.

Maximum power tracking of wave power generation system based on improved particle swarm optimization

In a wave power generation system, traditional particle swarm optimization (PSO) is prone to premature convergence and local optimal solution when it is used to control the maximum power tracking. Therefore, an improved PSO is proposed, and simulated annealing adaptive particle swarm optimization (SAAPSO) is constructed. The algorithm controls the inertia weight coefficient factor by hyperbolic tangent function and makes the nonlinear adaptive change. Using a linear change strategy to control social learning factors and self-learning factors, a simulated annealing operation is introduced, and a temperature is set according to the initial state of the population. The population is guided to compare the fitness value with the random number in the Metropolis criterion and temperature, and whether a new solution is generated is judged, to improve the problem that the algorithm falls into a locally optimal solution. The simulation results show that the algorithm can effectively prevent the wave power generation system from falling into the local maximum power point, and the maximum wave energy capture ability is significantly improved.

Summary of research on generator of offshore wind wave combined power generation system

In recent years, multi energy complementary utilization has become a new trend of energy development. Offshore wind and wave energy have many advantages, such as no pollution, concentrated energy form, etc. a new wind wave combined power generation system based on two degree of freedom linear rotating generator came into being. The research status of offshore wind and wave power generation system is summarized, and the advantages and disadvantages of independently developed offshore wind and wave power generation system, traditional wind wave combined power generation system and new offshore wind wave combined power generation system are compared. The research status of rotating generator of two degree of freedom straight line as the core energy conversion device of a new offshore wind wave combined power generation system is summarized, and the feasibility of using two degree of freedom generator in the new offshore wind wave combined power generation system is preliminarily verified by finite element method. Then, the research hotspots and difficulties of this kind of generator are discussed. Finally, the main research directions of two degree of freedom generator for offshore wind wave combined power generation system in the future are prospected.

Research on Acoustic Recognition of Underwater Targets based on the Principle of Sound Absorption

Due to the concealment of underwater engineering, the detection and monitoring of hydraulic structure construction is often more complicated and difficult than surface engineering. Cofferdam construction inspection and settlement construction quality inspection, especially to ensure the accuracy and efficiency of inspection in complex environments, have become an urgent problem to be solved in underwater engineering quality inspection and monitoring. This project designs an offshore fixed-point monitoring device based on wave energy and piezoelectric effect energy. The invention provides a wave power generation system. The system include simple structure, reliability and stability The fixed-point monitoring device combines the cantilever float device, the gas storage tank device and the piezoelectric ceramic energy supply device to provide the marine monitoring device with energy for automatic water surface monitoring, fixed-point and data collection. Finally, the comprehensive utilization of sea surface wave, compressed gas energy storage and piezoelectric effect energy is realized.

Design and Optimization of Linear Permanent Magnet Vernier Generator for Direct Drive Wave Energy Converter

A novel linear permanent magnet vernier generator (LPMVG) for small-power off-grid wave power generation systems is proposed in this paper. Firstly, in order to reduce the cogging force and the inherent edge effect of the linear generator, a staggered tooth modular structure is proposed. Secondly, in order to improve the output power and efficiency of the LPMVG and reduce the fluctuation coefficient of electromagnetic force, the relationship between the parameters of the generator is studied, and a method combining multi-objective optimization and single parameter scanning based on the response surface model and particle swarm optimization algorithm is proposed to obtain the optimal structural parameters of the generator. Thirdly, the output power and efficiency of the optimized generator are calculated and analyzed based on the two-dimensional finite element method, and the effectiveness of the multi-objective optimization design method based on the response surface model and particle swarm optimization algorithm is verified. Finally, a prototype is developed, and the calculated results and the measured results are shown to be in good agreement.

Development of Gas-Liquid Two-Phase Wave Power Generation System

Development of Gas-Liquid Two-Phase Wave Power Generation System

Enhanced Dynamic Performance in Hybrid Power System Using a Designed ALTS-PFPNN Controller

The large-scale, nonlinear and uncertain factors of hybrid power systems (HPS) have always been difficult problems in dynamic stability control. This research mainly focuses on the dynamic and transient stability performance of large HPS under various operating conditions. In addition to the traditional synchronous power generator, wind-driven generator and ocean wave generator, the hybrid system also adds battery energy storage system and unified power flow controller (UPFC), making the system more diversified and more consistent with the current actual operation mode of the complex power grid. The purpose of this study is to propose an adaptive least squares Petri fuzzy probabilistic neural network (ALTS-PFPNN) for UPFC installed in the power grid to enhance the behavior of HPS operation. The proposed scheme improves the active power adjustment and dynamic performance of the integrated wave power generation and offshore wind system under a large range of operating conditions. Through various case studies, the practicability and robustness of ALTS-PFPNN method are verifying it by comparison and analysis with the damping controller based on the designed proportional integral differential (PID) and the control scheme without UPFC. Time-domain simulations were performed using Matlab-Simulink to validate the optimal damping behavior and efficiency of the suggested scheme under various disturbance conditions.

Comparison and Optimization of a Magnetic Lead Screw Applied in Wave Energy Conversions

In order to improve the power density of the wave power generation system, a magnetic lead screw (MLS) is introduced in this paper as a speed-increasing device in a wave energy converter (WEC), which converts low-speed linear wave motion to high-speed rotational motion. Then, several types of MLSs with different topologies, which were optimized, are described. Finite element analysis (FEA) was used to investigate and evaluate their electromagnetic performances, such as the thrust force, torque, air gap magnetic density, etc. The optimized MLS prototype was manufactured, and the measurements verify the FEA results. Finally, a magnetic lead screw hybrid generator (MLSHG) for application to the WEC is proposed. This MLS significantly improved the power density under different wave conditions. When the moving speed v = 0.15 m/s, the output power of the MLSHG and outer-PM linear tubular generator were 923 W and 87 W, respectively, when the load resistance was 5 Ω. The output power of the MLSHG was more than 10 times compared to that of the outer-PM linear tubular generator in a fair comparison. Here, it is shown that the power density and output power of were MLSHG increased greatly.

Optimal design of linear switched reluctance motor for sea wave power generation

The switchless reluctance motor’s non-permanent magnet structure design ensures its high reliability in the marine environment; thus, it is a feasible solution for the generator of a sea wave power generation system. However, the corresponding thrust density and efficiency remain insufficient. This study focused on a new type of flat linear switched reluctance motor (LSRM), using the finite element software to establish a structural model, and optimized the design with the goal of improving the efficiency and energy density. The entropy method was adopted for sensitivity stratification to objectively select weights to avoid the influence of subjectively selected different proportional weights on the optimization results. Based on the entropy method, the sensitivity of different structural parameters was stratified, and the simulated annealing algorithm, response surface method, and single parameter scanning method were combined for optimization. Finally, the optimal structural size parameters of the motor were determined. Based on the two-dimensional finite element method, to simulate the electromagnetic performance of the reluctance motor under different operating conditions, such as thrust, loss, and efficiency, changes in motor performance before and after optimization were compared to verify the high power generation efficiency and energy density of the optimized linear motor.

A communication-free droop control scheme for distributed linear switched reluctance wave power generation system with adaptive voltage compensation

In wave energy generation systems, scaled and improved energy extraction can be realized by utilizing distributed linear switch reluctant generators (LSRGs). However, this type of power generation system often employs supercapacitors (SCs) as the energy storage media, and the system often suffers from output voltage variation and current fluctuation from the LSRGs. Meanwhile, the fixed droop factor also causes bus voltage deviation and aggravates energy imbalance of the energy storage system. In this paper, a communication-free droop control scheme with adaptive voltage compensation is proposed for the distributed linear switched reluctance wave power generation system. First, system stability is improved by applying a high droop factor. When the bus voltage fluctuation exceeeds the compensator threshold, this voltage information of the energy storage unit is introduced into the control loop. In addition, an adaptive voltage compensation algorithm is proposed for the system, and the control algorithm is able to reduce the bus voltage deviation and the energy imbalance of the storage unit, caused by the droop factor. The proposed control strategy can further improve the response and reliability of the energy storage units, and the bus voltage fluctuation can be regulated within ±3%.

Research on adaptive segmented control strategy used in direct-drive wave power generation systems

The problem of unstable output power in direct-drive wave power generation systems (DDWPGS) caused by violent power variation in one cycle of wave is common. The wave power fluctuates violently in a short time, and the lower the frequency, the higher the amplitude. Energy storage devices are usually applied to smooth the power and stabilize the system. This paper proposed an adaptive segmented control strategy (ASCS). It adaptively divided the system voltage into five symmetrical segments and regulated the reference power based on the VMD decompose results according to the different segments. The impedance analysis method (IAM) is implemented to verify its stability. The simulation results confirmed that it can not only automatically adjust the output of the energy storage device to adapt to the frequency and amplitude of wave power signal, but also ensure the safe operation of the system under the impact of charging load and wave power.

Simulation and Optimization Design of Large Wave Power Generation Device Based on Group Array Module

Based on the research achievements of the Haiyuan 1 oscillating buoy wave power generation device, this paper proposes the innovation about a group array of the buoy to increase the output of power generation and realize large-scale power generation. Firstly, the conversion efficiency of wave energy captured by buoys of arrays 3, 6, and 9 for power generation is theoretically estimated. According to wave theory, the energy conversion efficiency of buoy increases with the increase of array number. Then, the modeling and simulation of the buoy array wave energy generation system are carried out by using AMESim simulation software. Through the simulation and optimization of the parameters of the components in the array buoy storage power generation system, the stability and efficiency of the wave power generation device under different array buoys are studied. The simulation results show that by adjusting the volume of the accumulator, precharge pressure and the displacement of the hydraulic motor, the power generation system can not only realize the continuous power output, but also the power output increases with the increase of the number of accumulators. It is proved that the feasibility and rationality of the designed buoy power generation system in group array module, and the research results can make a reliable technical reference for the construction and implementation of large-scale wave power generation system.

A Communication-Free Droop Control Scheme for Distributed Linear Switched Reluctance Wave Power Generation System with Adaptive Voltage Compensation

A Communication-Free Droop Control Scheme for Distributed Linear Switched Reluctance Wave Power Generation System with Adaptive Voltage Compensation

A Review of the Optimization Design and Control for Ocean Wave Power Generation Systems

Ocean wave power generation techniques (converting wave energy into electrical energy) have been in use for many years. The objective of this paper is to review the design, control, efficiency, and safety of ocean wave power generation systems. Several topics are discussed: the current situation of ocean wave power generation system tests in real ocean waves; the optimization design of linear generator for converting ocean wave energy into electrical energy; some optimization control methods to improve the operational efficiency of ocean wave power generation systems; and the current policy and financial support of ocean wave power generation in some countries. Due to the harsh ocean environment, safety is another factor that ocean wave power generation systems will face. Therefore, before the conclusion of this review, a damping coefficient optimization control method based on the domain partition is proposed to improve the efficiency and safety of ocean wave power generation systems.