Advanced Materials Research Vols. 1049-1050

Abstract: A structure of ADCs which combines fold-interpolation and pipeline is introduced, as well as corresponding digital calibration method. The simulation shows that the performances of the ADC after calibration are improved a lot. The SFDR achieves 62dB at a sampling rate of 800MHz, when the input analog signal is at 397MHz.

Abstract: Among the current 3G SVCs, the one with the highest compensating capacity is the static var generator, which is featured by smooth and continuous bipolar reactive power, quick responding and small loss, and widely applied in petrochemical, metallurgy, wind power and power transmission and distribution, etc, working out power quality problems. As demand for static var compensators in market grows, LV SVG comes to the stage. Compared with HV and MV SVGs, although LV SVG is simple in structure, it has stricter requirements on compensating capacity and stability, which requires R&D to consider more technical details in product design.

Abstract: The arc furnace is a common load in smelting industry. Due to special structure, it often generates great impact on the grid. It has become a recognized technical means to use dynamic reactive compensation device SVC to eliminate the adverse impacts on grid power quality during arc furnace production. However, the electrical system of some arc furnace load containing sites is complex. Limited by the site condition in which sound commissioning environment cannot be provided for SVC, relevant control parameters can only be configured on the basis of experience, which leads to poor compensation effect, and thus affecting normal production of the user.

Abstract: SVC is a dynamic reactive compensator based on switching type HV electrical and electronic devices, well recognized as an effective means of resolving power quality problems. SVC is complex in structure, consisting of TCR valve sets, FC filter channel, etc. In particular, TCR valve set adopts thyristor serial connecting technology, and over 100 thyristors are adopted, which requires real-time status of devices in SVC to be monitored and uploaded, and even failures to be recorded. Therefore, the monitoring software becomes an important part in ensuring SVC safe operation. Combined with actual cases, this paper introduces a technology of using C++ Builder and Inter Base to design the static reactive compensator monitoring software. The user interface is elegant, with short development period, highly transplantable, and easily modified.

Abstract: impact loads, such as submerged arc furnace, are often used in the smelting industry, their features include high power, low voltage, high current, rated power is from several MVA to tens of MVA, rated voltage is less than 200V. Reactive and harmonic compensation scheme for such load is generally centralized compensation on high voltage side of the power grid, facts have proved that, the effect of such compensation mode is not satisfactory to customers. Therefore, people have designed a special low voltage high power SVG, which is installed on the low voltage side for compensation, it could perform reactive power compensation, and filter out harmonic, protect against grid voltage fluctuation and flicker caused by submerged arc furnace in different production periods effectively.Compared with common SVG project, how to guarantee safe and stable operation of the equipment under high current conditions is critical technical issue in the design. This paper takes an example of an actual project, designs water-cooled copper pipe bus as connecting bus of low voltage high power SVG. Rationality and feasibility of this design has been proved in actual equipment operation.

Abstract: For the problem of leakage, undervoltage and overvoltage fault protection of electromagnetic starter with supply voltage of 660 V and rated current of 200A, a leakage, undervoltage and overvoltage protective system based on PLC LM3108K was designed. This system uses voltage transformer to detect three-phase AC voltage. It protects undervoltage and overvoltage fault by judging effective value of three-phase voltage, protects leakage fault of main switch for electromagnetic starter by additional DC power and protects leakage fault of branch switch by using zero-sequence power direction. This system has good protection functions for leakage, overvoltage and undervoltage faults of electromagnetic starter in coal mine.

Abstract: An intelligent protection system of electromagnetic starter in coal mine was designed. Its controller core is PLC LM3108K. The voltage rank of protection system is 660V and the electric current rank is 400A. It has protection functions for overload, short circuit, break phase and three-phase imbalance. The system achieved overload protection by using the method of inversing time overload. Greater the overcurrent is, Shorter the time of protective action is. The system achieved short circuit protection by using phase sensitive protection method, which improves sensitivity and reliability of short circuit protection. The system can display work status parameters and fault types timely by text LCD. It has the advantages of hardware circuit structure flexibility and automatically reset after fault relieved.

Abstract: There are different safety assessment standards of grounding systems in different countries. Some of standards are widely adopted in the world, such as IEEE-80-2000, IEC-471-1, EA-TS41-24 and BS7354. In order to choose reasonable safety assessment standard in the design of grounding system of substation, these four standards are compared using a practical case. It showed that BS7354 is more conservative than IEEE-80-2000 and EA-TS41-24, and the definitions of allowable current are different between IEEE-80-2000 and IEC-471-1.

Abstract: In paper considers the principle of the control system power grid in the form of multilevel system consisting of a system of planning and allocation of management tasks, control system of the segments the grid, the local management system of elements of the grid. The paper shows the principle of operation of the upper and lower levels of the system, an example of a calculation for a segment of the grid, for which the system provides a balance of power capacities.

Abstract: In view of the existing onshore wind developments, this paper points out the problem in the development process, and thus leads to the development direction of offshore wind in China. the European advanced offshore wind power development status is recalled, and China's offshore wind power started developments are expounded. The key technologies of offshore wind power are presented. The problems of Chinese offshore wind power development are analyzed. Finally, the future of Chinese offshore wind power is prospected.