No abstract

The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load; this ensures safe and stable operation of non-grid connected wind turbines.

Energy storage technology is to achieve large-scale access to renewable energy sources; the key technology for improving efficiency, safety and economy of power systems is also to increase the ratio of clean energy to power generation, and effective means of promoting haze governance. By the end of 2015, the total installed capacity of the global energy storage equipment was about 167 GW, about 2.9% of the world's total installed power; the energy storage equipment in China is 22.8 GW, about 1.7% of the total installed power of the country. By 2050, China's energy storage equipment will reach 200 GW; the market size will reach more than 2 trillion RMB. The existing energy storage technologies include pumped storage, compressed air energy storage, flywheel energy storage, superconducting storage, lead-acid batteries, lithium batteries, sodium sulfur batteries, liquid flow batteries and super capacitors. Different energy storage technologies are applicable to different applications and fields, depending on system power and discharge time, the main application areas of energy storage technology can be divided into three parts: energy management, power bridging and power quality management. Future energy storage market development will focus on distributed energy storage, distributed photovoltaic PV + energy storage, Micro grid, distribution network side and user side and other fields. In recent years, China's energy storage industry has accelerated the pace of development in terms of project planning, policy support and capacity layout, in the next few years, with the rapid development of renewable energy industry, the energy storage market will also enjoy rapid growth. However, the energy storage industry in this country is still in the initial stage of development, and it is mainly based on demonstration and application, the commercial application of energy storage faces the high cost of storage and the imperfect market of power exchange. Energy storage technology route is not mature, lack of energy storage, effective price and effective incentives are both opportunities and challenges.

The time and space distribution characteristics of future high proportion of renewable energy sources will bring unprecedented challenges to the electric power system's processing and planning, the basic form of electric power system and operating characteristics will have fundamental changes. Based on the research status quo at home and abroad, this paper expounds the four scientific problems of the transmission network planning with high proportion of renewable energy. Respectively, from the network source collaborative planning, transmission network flexible planning. With the distribution network in conjunction with the transmission network planning, transmission planning program comprehensive evaluation and decision-making methods. This paper puts forward the research ideas and framework of transmission network planning considering the high proportion of renewable energy. At the end, the future high proportion of (renewable energy) grid-connected transmission network's opportunities and challenges are presented.