Energy storage technology is widely used in many fields including power system. In recent years, the reorganization of power industry in the world has brought new opportunities for development for various energy storage technologies. With these technologies, This is particularly evident in the energy management of power systems, especially in the fields of renewable energy and distributed generation, which can also be used in traditional power generation and transmission and distribution networks. The following briefly introduces the basic principles of various energy storage technologies and their development status quo. 1 pumped storage Pumped storage power station in the application must be equipped with upstream and downstream two reservoirs. During the low load period, the pumping energy storage equipment works in the motor state and pumps the water from the downstream reservoir to the upstream reservoir for storage. At peak load, the pumped storage facility operates in the state of the generator and uses the water stored in the upstream reservoir to generate electricity. Some high dam hydropower storage capacity, it can be used as a pumped storage power station for power scheduling. The use of mines or other caves to achieve underground pumped storage is also technically feasible. The ocean can sometimes be used as a downstream reservoir. In 1999, Japan built the first pumped storage power plant that utilized seawater. Pumped storage was first used in Italy and Switzerland in the 1890s. Reciprocating units (including pump turbines and electric and generator) appeared in 1933 and now there are speed-adjustable units to increase energy efficiency. Pumped storage plants can be built to any capacity, with energy stored for hours to days and efficiencies between 70% and 85%. Pumped storage is one of the most widely used energy storage technologies in power systems. Its main application areas include energy management, frequency control, and the provision of system spare capacity. At present, more than 90GW of pumping energy storage units are in operation in the world, accounting for about 3% of the global total installed capacity. An important constraint that limits the wider use of pumped storage power plants is the long construction period and the large project investment. 2 advanced battery storage It is estimated that the market demand for batteries in the world is about 15 billion U.S. dollars per year. For industrial batteries, such as UPS, power quality regulation and spare batteries, the total market can reach 5 billion U.S. dollars. In the United States, Europe and Asia, is set up to produce high-performance energy storage battery business. In the past 12 to 18 months, there have been battery production lines with a production capacity of 300MW per year in operation. Lead-acid battery is the oldest and most mature battery technology. It is a low-cost universal energy storage technology that can be used for power quality regulation and UPS. However, due to the short life of such batteries, their use in the field of energy management is limited. ZnBr batteries were successfully developed by Exxon in the early 1970s. After years of research and development, many ZnBr battery energy storage systems with a capacity of several thousand watts have been built and tested, with a net efficiency of 75%. At the beginning of the 1980s, the University of New South Wales of Australia pioneered the development of Vanadium Redox Flow Battery (VRB) batteries. At present, a 500kW / 5MW? H VRB energy storage system has been installed in Japan with a net efficiency of 85% . In recent years, a variety of new batteries have been successfully developed and used in power systems. Regenesys Technologies in the UK is building a 15MW / 120MWh energy storage plant using PSB (Polysulfide Broe Flow Battery) batteries with a net efficiency of about 75%. NaS batteries have a high energy storage efficiency (about 89%), but also has the ability to output pulsed power, the output pulse power in 30s to reach six times the continuous rated power value, a feature that allows NaS batteries can be used simultaneously Power quality regulation and load peak load shifting adjustment two purposes, thereby enhancing the overall equipment economy. In Japan, there are currently over 30 energy storage demonstration projects using NaS battery technology with a total energy storage capacity of over 20MW, which can be used for 8h day-load peak-to-valley regulation. Compared with other batteries, lithium-ion battery is the main advantage of high energy density (300 ~ 400kW? H / m3, 130kW? H / t), high energy storage efficiency (close to 100%) and long service life (3000 times for each discharge not exceeding 80% of storage capacity). Due to the above advantages, lithium-ion battery has been rapidly developed. However, despite the fact that lithium batteries already account for 50% of the market share of small mobile devices in a few years, the major obstacle to producing large capacity lithium-ion batteries is their high cost, which Mainly because it requires special packaging and is equipped with the necessary internal overcharge protection circuitry. Among all the batteries, the Metal-air battery is the most compact and is expected to be the lowest-cost battery, an environmentally-friendly battery. The main drawback is that this battery is very difficult to charge and inefficient. 3 flywheel energy storage Most modern flywheel energy storage systems consist of a cylindrical rotating mass and a support mechanism consisting of magnetic levitation bearings. The purpose of using magnetic bearings is to eliminate friction loss, improve system life. In order to ensure a sufficiently high energy storage efficiency, the flywheel system should operate in a higher vacuum environment to reduce windage loss. The flywheel is connected to a motor or a generator and, through some form of power electronics , adjusts the flywheel speed to achieve power exchange between the energy storage device and the grid. One outstanding advantage of flywheel energy storage is that it requires little or no operational maintenance, has long equipment lifetimes (20 or tens of thousands of deep charge and discharge energy processes) and has no adverse effect on the environment. The flywheel, with its excellent recycle and load following performance, can be used in applications where the time and capacity range between short-term energy storage applications and long-term energy storage applications. In the realization of flywheel energy storage device, the use of solid steel flywheel can also be used composite flywheel, flywheel which specific needs of economic and technical comparison, the system cost, weight, size and material properties and other indicators of compromise. The use of high-density steel, the edge line speed of up to 200 ~ 375m / s, and the use of lighter weight, higher strength composite materials, the edge line speed of up to 600 ~ 1000m / s. The actual amount of energy that the flywheel can output depends on its speed range and it is not possible to output rated power at very low speeds. Currently, high-power flywheel energy storage systems have been developed and used in the fields of aviation and UPS. Research institutes led by Beacon Power are working on the optimal design of flywheel energy storage for use in long-term energy storage services (up to several hours) while reducing their commercial costs. Currently, 2kW / 6kW? H flywheel energy storage systems are used for powering communications equipment. Flywheel Farm Approa