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The marine energy reserves available for development in China are huge, and the coastal areas are highly concentrated in China’s power load area, so the research and development of marine energy is of great significance. Aiming at the problem of large fluctuation and poor predictability of offshore wind power generation, a combined power generation system of offshore wind power and tidal current is proposed. This paper analyzes the time and space complementary characteristics of offshore wind power and tidal current energy, designs the integrated power generation platform, establishes the system model based on DC bus network, and determines the evaluation index of the system. Based on the Homer software, the optimal allocation of system capacity is analyzed, which verifies that the economy of wind tide combined power generation system is better.

The stability problem caused by the integration of wind farms into the power grid is becoming more and more serious. Reactive power shortage is an important reason for this problem. However, simply using reactive power compensation equipment will greatly increase the investment cost of wind farms. In view of the above problems, this paper puts forward the principle that the wind farm's own reactive power source is the first choice and the external reactive power source is the supplement, and the corresponding coordination is proposed for the two reactive power sources of the double-fed wind turbine grid-side converter and the reactive power compensation device STATCOM Control strategy, and a 3machine 9-node system including doubly-fed wind farm and STATCOM was built in the software DIgSILENT/Power Factory, and two typical fault types were set up. The simulation results show that, compared with the traditional wind farm constant power factor control In contrast, the proposed coordinated control model can ensure sufficient reactive power support in certain emergencies, which plays a very good role in supporting the transient voltage stability of the wind power access system and reduces the installed capacity of STATCOM, Which saves the investment cost of wind farms, and also verifies the correctness and effectiveness of the reactive power coordinated control model.

The energy storage component of the MEES system is mechanical elastic energy storage tank group. Whether the mechanical structure design of energy storage tank is reasonable or not directly determines the performance of the whole system. In this paper, the structural design scheme of series linkage energy storage tank group is proposed, which can take into account the energy storage capacity and power demand. Firstly, the structural group of energy storage tank group is analyzed. Secondly, the operation mode of energy storage and power generation process of energy storage tank group is described in detail. Finally, the mathematical model of energy storage/generation operation is established, which provides theoretical guidance for the configuration of capacity and power of energy storage tank group.

Dynamic voltage regulator (DVR) is regarded as one of the best solutions to voltage sags, so it has attracted many researchers' attention recently. This paper has adopted cascaded multilevel inverter as the main circuit of DVR and proposed one random distribution scheme for SVPWM signals which is based on the logistic mapping in order to choose the working H-bridge units and switching states randomly at low modulation indices, the difference from other schemes is the consideration of previous output states. As known from the characteristics of logistic mapping, its application to cascaded inverter can decrease the switching losses effectively and balance the working probability of H-bridge units. Finally, the simulation results have justified its feasibility and correctness. (6 pages)