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
Since 1882, when electricity was first generated and used in Shanghai, the electric industry has experienced a history of continuous formation and development for nearly 130 years. For more than 100 years, particularly since the reform and opening of China, many changes have taken place in China’s electricity price, which have well suited the needs of national economic and social development. There are a wide range of electricity price policies,
Renewable power modules such as the thermoelectric generator and the PV panel are featured by low output voltage and low power. In the paper "Distributed High Efficiency Renewable Power Systems with Modules in Series Connection," with the aim to maximize output power, a high energy efficiency module integrated converter （MIC）, and its control strategy for series connected distributed （SCD）
As China’s economy continues to grow and energy demand continues to rise, the scale of power transmission lines and buried pipelines is expanding rapidly. The problems of over-voltage protection and electromagnetic compatibility within and between overhead lines and underground cables become increasingly prominent. The impedance and admittance parameters of multi conductor systems consisting of overhead lines, underground cables and
Increasing-block electricity tariff should not be confused with the increase of electricity tariffs. The fundamental of the increasing-block electricity pricing system is to mobilize the use value of electricity product, promote social equity, and ensure the right of people’s livelihood while saving natural resources and protecting the environment.
Standardization in China has achieved rapid development since the membership status of International Standardization Organization (ISO) was restored in 1978.Under the unified leadership of the Standardization Administration of China (SAC),standardization has played a positive role in improving the overall quality of Chinese products,safeguarding citizens and property security,protecting the health of animals and plants,as well as protecting the environment.
Based on real-time digital simulations（RTDS）,a laboratory environment similar to the real-time operation situation of the Three Gorges Hydropower Station is established.Then,the causes for the power fluctuation of the second generator by errors in the rotor rotating speed calculation are found,and the tuning method of the speed related parameters are given.The damping and reverse tuning characteristics of power system stabilizers（PSSs）in the digital automatic voltage regulator（AVR）are compared and investigated in the frequency range of 0.18-1.1 Hz.The efficiency of the proposed tuning method for ensuring power system stability is verified by RTDS.Finally,field tests show the validity of the laboratory test results.
Calculations and analyses are made for the ultimate composition of 158 Chinese power coals.The results reveal that the carbon content on as received basis,C ar ,increases linearly with the increase of the low heating value Q net,ar on as received basis;the hydrogen content on as received basis,H ar ,first increases with the increase of the volatile content on dry ash free basis V daf (V daf <33.0%)and then decreases(V daf >33.0%);the oxygen content on as received basis,O ar ,increases linearly with the increase of V daf ,ranging between 2.0% and 12.5%.By comparison,the nitrogen content on as received basis N ar of bituminous and lean coal is higher, while the sulfur content on as received basis S ar of anthracite is higher than bituminous coal,lean coal and lignite.The hydrogen on as received basis H ar is important for the conversion between low heating value and high heating value on as received basis for Chinese power coals,and S ar is important for the calculation of high heating value from the oxygen bomb heat value for Chinese power coals.
Energy-conservation based generation dispatching is the revolutionary change in operation mode which could reduce energy consumption and pollutant emissions, promote power industry restructuring, and achieve sustainable development. Social benefit evaluation of the energy-conservation based generation dispatching under the new situation and environment has come into being as an important theoretical issue. A new scenario analysis based social benefit evaluating method, which is implemented by comparing the energy consumption and pollutant emissions of different scenarios defined by the key indicators, i.e., load factor and coal consumption structure, is proposed in the paper. Then the composition of social benefit is analyzed from the point of the dispatching mode and the coal consumption structure. The method proposed is of clear physical meaning. It is not only practical, but also applicable for the implementation of energy-conservation based generation dispatching in different phases and with different goals.
The function of the UHVDC test base of the State Grid Corporation of China （SGCC） is oriented to serve UHVDC power transmission and substation projects, especially power transmission from West China to East China, and to promote localization of UHVDC transmission and substation equipment. In essentials, this test base consists of UHVDC test transmission line, corona cage, outdoor test site, UHV test hall, pollution and environment laboratory, electromagnetic environment simulation test site, insulator laboratory, arrester laboratory and live equipment test field. This paper introduces the function and design idea of the test base, presents the main performance parameters of the above-mentioned test facilities, and summarizes the matters of concern when siting and planning.
In order to develop large CFB boilers with independent intellectual property, Xi’an Thermal Power Research Institute （TPRI） established a laboratory with complete functions for the technical development of CFB boilers. This laboratory consists of a 1-MW and a 4-MW CFB combustion test facilities and a laboratory for limestone desulphurization performance evaluation. It carried out tests on CFB combustion and desulphurization for Chinese typical coals and limestone and research on heat-transfer characteristics and key parts, and developed the first home-made 100-MW CFB boiler. Based on the experience of R＆D, the laboratory further researched key techniques for enlarging capacity systematically, and cooperating with Harbin Boiler Co. （HBC）, developed the first domestic 210-MW CFB boiler with independent intellectual property and put it into engineering demonstration, laying a solid foundation for the development of CFB boilers of even larger capacity.
Peak regulation in the Northeast power grid is going from bad to worse. This stimulates the need to pumped-storage hydropower for its role in this respect. Based on the status of power sources and the load forecast in the system, the author puts forward a minimum construction scale of pumped-storage stations by the end of 2020 from technical feasibility, and an economic scale from economy. The analysis and comparison on the two schemes can be regarded as a reference for reasonably planning pumped-storage stations in the northeastern part of China.
A three-phase four-wire distribution system electronic power transformer(EPT) implemented with the input stage,isolation stage and output stage was presented and its load characteristics were analyzed.A simple and appropriate control was developed to obtain good characteristics based on analyzing the demand of the primary system and the loads.In this control scheme the dual-loop decouple control in synchronous rotating d-q frame was adopted in the input stage and the dual-loop control based on voltage instantaneous value was introduced in the output stage.The load characteristics of the electronic power transformer were investigated in detail by simulations under Matlab/Simulink.The results show that the EPT has good performances with the proposed control scheme under balance and imbalance loads,which makes the input current sinusoidal and keeps the load voltage in normal value.
Solar energy photovoltaic power generation is hopeful to be applied in a large amount and possesses a certain proportion in the structure of energy in the future. In this paper, based on the forecasting of electric load demand and energy structure of power generation in the middle of 21century, the pictures of VLS-PV power generation is composed, the operation characteristic of VLS-PV power generation and the adaptability of electric power grid for it is analyzed, the ways for transmitting large amount of PV power and the economic and technical bottlenecks for applying VLS-PV power generation are discussed. Finally, the steps and suggestions for developing VLS-PV power generation and its electric power system in China are proposed.
The high temperature heating surface such as the superheater and reheater of the large-size utility boiler all experience a relatively severe working condition. The failure of the boiler tubes will directly impact the safe and economic operation of the boilers. An on-line life monitoring model of the high temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wall metal temperature and working stress are on-line monitored, and with this model, the real time calculation of the life expenditure of the heating surface tuhe bundles has been realized. Based on the technique the on-line life monitoring and management system of high tem- perature heating surface was developed for the 300 MW utility boiler. An effective device was thus suggested for the implementation of the safe operation and the condition based maintenance of the utility boilers.
