Offshore wave energy can be easily predicted and is proved to be much better than other forms of ocean energy such as shoreline wave, near-shore wave, and tides. Research on offshore wave energy extraction has been carried out in many countries to meet the growing demand for clean energy and reduce the impact on natural environment. This paper reviews the development of offshore wave energy extraction systems in the recent decade. Several aspects are introduced, including a global wave energy resource assessment, offshore wave energy extraction technologies, and the interaction between wave and floating buoy as well as linear generators. Although various offshore wave energy extraction systems have been proposed and even tested, it is difficult to decide which is the best one. In fact, design of floating buoy and linear generators plays an important role in the operational efficiency of offshore wave energy extraction system. This review provides some useful guidelines for future studies in this field.
As more and more unconventional energy sources are being applied in the field of power generation, the frequency fluctuation of power system becomes more and more serious. The frequency modulation of thermal power unit has disadvantages such as long response time and slow climbing speed. Battery energy storage has gradually become a research hotspot in power system frequency modulation due to its quick response and flexible regulation. This article first introduced the control method based on the signal of ACE (Area Control Error), which is the basic way of secondary frequency modulation and analyzed the features of the basic control mode. Then it zoned the signal of ACE and SOC of the battery energy storage system. On this basis, different frequency modulation methods were proposed according to the requirements of frequency modulation and the characteristics of the output of different regions. In addition, the fuzzy controller is used to smooth the output of the energy storage system under the normal adjustment of the regional control deviation and the normal charging and discharging state of SOC. Finally, a two-region interconnection simulation system was established based on the MATLAB simulation platform, and the simulation results verified the effectiveness of the proposed control strategy.
In order to efficiently use energy storage resources while meeting the power grid primary frequency modulation requirements, an adaptive droop coefficient and SOC balance-based primary frequency modulation control strategy for energy storage is proposed. Taking the SOC of energy storage battery as the control quantity, the depth of energy storage output is adaptively adjusted to prevent the saturation or exhaustion of energy storage SOC. The balanced control strategy is introduced to realize the rational utilization of resources and the fast balance of SOC in the process of primary frequency modulation of energy storage battery under different charge states. Then, four evaluation indexes are proposed to evaluate the effect of primary frequency modulation and SOC maintenance. Taking a regional power grid as an example, a simulation analysis is carried out under step load disturbance and continuous load disturbance. According to the simulation results, the proposed control strategy is effective in power system frequency regulation and battery SOC maintenance.
Under the background of large-scale and rapid development of renewable energy, in order to improve the economic benefit of the system and ensure the reliability of the system, this paper introduces hydrogen production and energy storage into the independent wind/photovoltaic/hydrogen/storage capacity optimization configuration method. In order to minimize the total planning cost and self-sufficiency rate of system power supply, a capacity optimization allocation model was established. On the basis of this model, the Multi-objective Salp Swarm Algorithm (MOSSA) was improved in Algorithm structure, Tent chaotic mapping was introduced to initialize the population, and the positions of leaders and followers were updated based on the adaptive spiral search strategy. The validity of the algorithm is verified by test function. Finally, the specific example is solved by MATLAB programming, and the improved multi-objective Salp Swarm Algorithm (IMOSSA) is used to obtain the capacity configuration scheme, which provides reference for the optimization design of independent photovoltaic hydrogen storage system.
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