This paper presents the behavior analysis of Modular Multilevel Converter (MMC) under DC pole-to-pole (PtP) Short-Circuit (SC) fault, which is an important issue in fault management, electrical system design and MMC based power system protection and control. Firstly, the transient behavior is analyzed where the conduction overlapping angle γ is defined. Secondly, seven possible SC current paths induced by different γ are identified, and the corresponding engineering SC current calculation methods for both AC and DC sides are proposed. And then, the influences of impedance distribution factor k and equivalent SC resistance RSC on SC currents are elaborated. Finally, case study is provided to verify the effectiveness of the proposed analysis methods.
Low-NOX combustion retrofit is performed by adopting staged combustion technology for a 600 MW utility boiler with a four-corner tangential firing system. The emission data of NOX before and after retrofit are compared and analyzed. The test results show that the emission concentration of NOX decreases obviously after the low-NOX retrofit. Additionally, the emission of NOX decreases by nearly 50% when the unit load is higher than 350 MW. It can also be concluded that the emission of NOX is influenced significantly by the amount of SOFA, the damper opening of auxiliary air, the differential pressure between the secondary air windbox and the furnace, and so on.
Because of the action of strong magnetic forces, it’s difficult to avoid end winding vibration in the large turbo-generator stator. Sometimes it leads to the occurrence of accidents and affects the normal operation of the generator. This paper firstly lays out the calculation method for end winding magnetic force. Second, based on the structure of large machines, the natural vibration frequency equation and forced oscillation equation is set up. Third, through the analysis of magnetic force calculation and vibration on the end winding of turbo-generator, it will be shown that the end winding vibration is related to the magnetic force and the position of winding binds as well as binding tightness. We can ease the winding vibration by distributing binding position appropriately or add more bindings, and test the concept through experimental data.
In this paper the author proposes the choice of nuclear power is inevitable for China’s energy and electricity power development from strategic viewpoint. The challenges to efficient and safe nuclear power development are analyzed in details and corresponding suggestions are provided.Since the Fukushima nuclear accident, the nuclear energy safety and development have been reviewed profoundly all over the world. Although the nuclear safety plan
For the power generation groups in China, many urgent issues have come up to be resolved regarding how to properly decentralize the company management, distinguish the responsibilities between the parent and subsidiary companies as well as those among different subsidiary companies, and coordinate the subsidiary companies in order to maximize the interests of entire group. In recent years, featured by large scale and large amount of members across
