With the rapid development of the grid, smart grid has become an undoubted trend. World's major power companies are searching for local smart grid technologies in transmission intelligence, substation intelligence and distribution intelligence and other areas. And China is leading our own smart grid revolution with world-class UHV power technologies, both in AC and DC. Chinese UHV have suffered countless hardships on our road. The development of UHV and smart grid technologies in China and their position in the world prove that the UHV technologies line with China's national conditions. It is the road we must follow in the development of smart grid in China.
As a result of using converter and the other power electronic devices on the side of doubly-fed induction generator (DFIG) rotor, it will produce a large amount of harmonic current at runtime. In order to reduce the harmonic pollution to power network, DFIG uses a variety of harmonic suppression measures. This paper introduces the working principle of DFIG and the harmonic suppression, at the same time, the effect of harmonic suppression through the Matlab simulation is analyzed.
Based on WAMS technology and the demand of real projects, a method of mixed measurement of zero-sequence parameters for two parallel coupled transmission lines is proposed. The principles and specific methods of mixed measurement mainly based on the incremental method are explained in details.The mathematical model is given and a digital simulation of coupled transmission lines with different zero-sequence parameters is conducted to verify the method.
In recent years, a new type of 380V low voltage fixed circuit breakers are used in newly built substations. Fixed circuit breakers without chassis only have two states. They are on and off. They can not provide a clear break point in circuit. So Their isolation function is not obviously. Low voltage equipment in Hub substations should have automatic mutual transfer function. Recently Automatic Transfer Switch (ATS) is often chosen in the newly built digital substation, intelligent substation or large hub substations. Automatic Transfer Switch has interlocking function to avoid the collision of two different power. With the popularize of new equipment such as the 380V fixed circuit breaker and Automatic Transfer Switch, the operation and management of low-voltage equipment in substations puts forward higher requirements as well. The conclusion contains the better ways in operation and maintenance of these new low-voltage equipment.
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