This article takes a 120 W direct-drive permanent magnet synchronous generator (PMSG) for tidal current energy as the research object, with the aim of starting at low flow velocity, low voltage regulation, and high sealing performance. The research was conducted on the design method of the generator, and the parameter calculation formula is modified based on the structural characteristics of the generator. The design scheme is simulated using the finite element method, and the voltage regulation is optimized using evolutionary algorithm. A prototype was manufactured based on the optimized scheme, and drag experiments and sealing tests were conducted. After that, the generator and impeller were assembled, and water tank drag experiments were conducted. The experimental results verified the reliability of the motor design method in this paper.

Tidal energy, as a sustainable and environmentally friendly energy source, has attracted widespread attention in recent years. The technology of blade active pitch control is the key technology to cope with tidal velocity change and improve the stability and efficiency of horizontal-axis tidal generator sets. When solving the problem of speed variation, the core algorithm is the key to ensuring stable operation and improving the efficiency of power generation. When traditional PID is used to manage complex systems, the controller faces the challenge of complex parameter tuning and insufficient robustness. The application of a particle swarm optimization (PSO)–PID controller and fuzzy PID controller in the independent interval system of tidal generator sets is introduced for the first time in this paper. This paper presents a comparative study of unified pitch control and independent pitch control (using electric pitch control) for a three-rotor tidal generator with a rated capacity of 300 kw and a blade radius of 8.5 m. Simulation was carried out on the MATLAB/Simulink (2023a) platform to evaluate the performance of the two controllers under different flow rates and interference conditions. The results show that the PSO-PID controller has significant advantages in reducing overshoot, speeding up response times, and improving power generation efficiency. At the same time, the PSO-PID controller also shows superior performance in pitch angle adjustment frequency and generator output power and realizes timely and effective system stability control.

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.