The insulation coordination of the converter station is very important for the security and economy of the UHVDC power transmission system, and lightning surge overvoltages at the converter station should be calculated accurately. This paper mainly analyzes the influence of modeling methods on the lightning surge overvoltages caused by the backflashover of the incoming dc transmission lines by using the PSCAD program, such as the selection of lightning stroke current waveform, tower model, flashover criterion of the insulator, and so on. The simulation results show that modeling methods have a great influence on the backflashover lightning withstand level of the incoming dc transmission lines, but their influences on the lightning surge overvoltages of the equipment in the converter station are not so obvious.

It is very important for the +/- 800kV UHVDC transmission project to study the overvoltage protection and insulation coordination of the converter stations because of its importance in the power grid. The paper studies the DC transient overvoltage of the converter station in the Nuozhadu-Guangdong +/- 800kV UHVDC transmission project by using the PSCAD simulation program. The simulation results show that the overvoltages on the equipments are influenced by the modeling methods and control strategy of the UHVDC system, and the overvoltages on several arresters are over their protective levels. At last, proper measures are put forward and analyzed for improving the insulation coordination scheme of the +/- 800kV converter station.

The insulation co-ordination of the ±800 kV converter station is important for the security and economy of the ultra-high voltage transmission system.By using the PSCAD/EMTDC simulation,we analyzed the lightning intruding overvoltage distribution and the lightning impulse withstand voltage of equipment in the Jiangmen converter station,which was the inverter station of the ±800 kV UHVDC power transmission project from Nuozhadu to Guangdong.The electromagnetic transient model of equipment in converter station and the incoming transmission lines was established,and proper operation mode of the UHVDC system was selected to analyze the most serious situations.The leader propagation method,which was proper as the flashover criterion of the insulators compared to volt-time characteristics in any waveform overvoltage,was used to calculate the back flashover and shielding failure current,and the maximum shielding failure current was calculated by electric geometry method(EGM).The maximum lightning intruding overvoltage from AC and DC transmission lines was simulated and the lightning impulse insulation level was checked.It is found that the lightning withstand level of the incoming transmission lines is high when the leader propagation method is used as the flashover criterion of the insulators,and the maximum lightning intruding overvoltage is caused by shielding failure.The simulation results show that the AC incoming transmission lines should be improved to limit the maximum shielding failure current.

A new approach is proposed to choose wide area feedback signals for wide area damping controller (WADC) in bulk power systems. Firstly, a novel signal selection benchmark is proposed, which is related to modulation amplitude of WADC and reflects the real control cost. According to this criterion, an index named dominant mode ratio (DMR) is proposed using linear system theory, and the algorithm based on time-domain curves and Prony analysis is also presented. Then, studies are carried out for the China Southern Power Grid (CSG) when using DMR to select an optimal wide area auxiliary input signal for the modulation control of Gui-Guang I HVDC-link to damp the inter-area oscillation between Yunnan and Guizhou. The effectiveness of DMR index is validated through time domain simulation and eigenvalue analysis.

The idea of coordinated control for the modulation of multi-HVDC transmission line systems in the southern power grid was put forward after analyzing the function of modulation control in HVDC systems for improving AC system stability. Through practical calculation and analysis, it is verified that the coordinated control of multi-HVDC transmission line systems is very important for improving AC system stability in the southern power grid. The preliminary scheme for the coordinated control in the southern power grid are discussed and presented.

There will he several DC lines parallel connected to the South China Power Grid in 2015.A severe fault,i.e.DC bipolar block is selected to go deep into the research by simulation.The transient stability problem caused by this severe fault is theoretically analyzed and the rationality of the analysis is proved by the simulation.A novel new strategy is proposed,in which the filter of the DC fault line at converter station is reserved to enhance the system transient voltage stability under this fault. Finally the feasibility of this approach is proved by simulation.

Firstly, the types and characteristics of the common ground electrode used in HVDC system are analyzed in this paper. The effect of the common ground electrode to the HVDC transmission system and the environment are researched by modeling the common ground electrode with two High Voltage Direct Current (HVDC) transmission systems and analyzing the voltage variation (rise or down) of the neutral bus in converter station. Even more, the stability of the DC system is analyzed. Combining to the parameters of the Yunnan-Guangdong (YG) Ultra HVDC transmission system and Guizhou-Guangdong (GG) II HVDC transmission system, a detailed analysis of the effect of the common ground electrode to the DC transmission system is given. In addition, a comparison of the environment effect of the independent ground electrode and the common ground electrode to the DC system is presented in this paper, too. In the end, solving methods and suggestions to the corresponding negative effect are presented in this paper.

采用Siemens公司的NETOMAC数字仿真计算程序详细分析了2005年广东电网的暂态电压稳定性,对广东电网可能存在的暂态电压稳定问题、电压薄弱环节、影响因素等进行了深入的研究,提出了在系统中装设STATCOM设备和利用直流系统的紧急功率调制功能等措施解决存在的问题.

The Southern Interconnected Power Network will be the most complicated power network in the world at the end of2005.In order to ensure security and stability operation of the Southern Interconnected Power Network,deep research on security and stability control system in the Southern Interconnected Power Network,especially in Guangdong power grid of the receiving-end,shall be carried out.Standing by Guangdong power grid,this paper studies the security and stability level in detail under internal faults and ACHVDC transmission line faults in Guangdong power grid,discusses the strategies of security and stability control system in Guangdong power grid,and presents the problems that need to be solved.