Hong-Chun Shu

Study on Traveling Wave Propagation Characteristics of ±800 UHVDC Transmission Lines

Traveling wave produced by a short-circuit fault or lightning will propagate along transmission lines with deformation and attenuation, which are due to energy loss and frequency-dependent line parameters. By the phase-modal transform method, the multi-conductor transmission lines could be decoupled into independent modal. Each modal is a single uniform line described as two-port networks. In this paper, the frequency-dependent parameters of uniform transmission lines are calculated in complex frequency domain. Based on the telegraph equation in complex frequency domain, the transfer functions between traveling wave signal source and observation point (relay location) are derived. The time domain waveforms of traveling wave at the observation point are calculated by Hosono numerical Laplace inverse transform method. Compared with PSCAD/EMTDC simulation results, the proposed method in this paper is proved effective.

Coordination Control between PSS and SVC Based on Fuzzy-Satisfactory Degree and MOEA

Power system dynamic stability includes two problems: power angle stability and voltage stability. For the former, the best way is to install power system stabilizer (PSS) on the key generator groups, and for the latter, however, Flexible AC transmission systems (FACTS) devices such as static var compensator (SVC), static compensator (STATCOM) and so on are the popular methods. PSS can effectively enhances the damp of the system, so is helpful for improving the stability of power angle, but it has little affects on the voltage stability. SVC not only improves the voltage stability but also reinforces the damp of the system if additional control is suitable. A multi-aim optimal designing method which is based on fuzzy-satisfactory degree theory is presented to solve the problem of cooperation control of PSS and SVC. Simulation results show that, used the solution presented in the paper, the stability of power angle and voltage can be effectively enhanced.

A New Advanced Genetic Algorithm for Optimal Unit Commitment of Power System

Genetic algorithm (GA) is applied to the calculation of optimal unit commitment (UC) in this paper. Based on the theory of GA and the characteristics of UC in power system, a new advanced genetic operation is developed. The test results demonstrate that not only does the advanced GA consider the constraints very well, but also has some advantages, such as good convergence, fast calculating speed and high precision. The results also prove the efficacy and correctness of the method.

Modeling and Simulation of Lightning Electromagnetic Transient and Identification of Shielding Failure and Back Striking in ±800kV UHVDC Transmission Lines - Part II: Identification of Shielding Failu

The identification of shielding failure and back striking in transmission lines has always been a difficult subject. This paper analyzed the process of back striking and shielding failure in ±800kV UHVDC transmission lines. Because the mechanisms of produced transient zero module voltage and its propagation paths is different between back striking and shielding failure, their wavelet energy of different frequency bands of transient voltages is different. Thereby, from the perspective of protective relaying, this paper proposed an identification method to shielding failure and back striking in ±800kV UHVDC transmission lines based on wavelet energy. The data can be acquired from high speed protection device. The EMTDC simulation shows that the proposed method can effectively identify shielding failure and back striking in the whole UHVDC transmission lines, and is not affected by various wave shapes of lightning current.

Full process dynamic voltage stability of 2015 Yunnan-Guangdong ultra-high voltage AC/DC hybrid transmission system

Till 2015, a large scale, ultra-high voltage and AC/DC hybrid power transmission configuration, including three ±800kV ultra-high voltage DC systems, will be formed. For such a complex system, dynamic characteristic will become attention focus. Based on the 2015 Yunnan-Guangdong ultrahigh voltage AC/DC hybrid system, full-process dynamic voltage stability is analyzed in this article, for which models of on-load tap changer transformer (ULTC), over-excitation limit and under-excitation limit, and under-voltage load-cutting are established. Under serve disturbances, influence of on-load tap changer transformer action on full-process dynamic voltage of the sending system Yunnan power grid is analyzed, which provides reference for the planning of 2015 Yunnan-Guangdong ultra-high voltage AC/DC hybrid system.

Lightning Withstand Level Calculation and Anti-lightning Method Research for Transmission Lines Across Heavily Icing Region

Due to the impact of heavy ice loading conditions and high altitude geographical environment, discharge between lightning shielding wires and conductors frequently happens as a result of uneven ice shedding in part of 220 kV Fugong-Lanping transmission line across Biluo snow-capped mountain in Yunnan province. This condition is often accompanied by tripping accidents. The line is even out of service for several months when it has threatened the safe operation of neighboring power networks. So other anti-lightning method is eagerly needed instead of double lightning shielding wires to weaken the bad influence causing by heavily icing condition. Based on the situation above, two line reconstruction schemes are put forward. One is to install single coupling ground wire after removing lightning shielding wires; the other is to install double side shielding ground wires after removing lightning shielding wires. Simulation models of this line under different anti-lightning methods were constructed and lightning stroke simulations were conducted on EMTDC. The proposed methods are verified effective by comparisons of lightning withstand levels. Simulation results indicate that lightning withstand levels can meet the demand of power enterprise standard under both anti-lightning methods. And lightning withstand levels are higher if double side shielding ground wires are installed and electrical connection is made between side shielding ground wire system and transmission line system.

HVDC modulation of three Yunnan-Guangdong ±800kV DC transmission systems in 2015

The control and modulation scheme of DC system greatly effect on transient stability in AC/DC hybrid power grid. Taking Southern China Power Grid in the year of 2015 for example, when fault occurs in the sending system Yunnan power grid, influence of modulation scheme such as large power flow modulation and bilateral frequency modulation on transient stability margin of hybrid system is explored. Study results are available for reference in the programming and the making of DC modulation measures for ultra-high voltage Yunnan-Guangdong transmission system in the year of 2015.

Adaptive Genetic Algorithm Applied in Coordinated Control of PSS and STATCOM

Firstly, an adaptive genetic algorithm (AGA) is proposed. For traditional genetic algorithm, it easily premature and falls into local optima. A better initial population should have differences among the individuals and distributes uniformly in the whole solution space. In AGA of this paper, initial population is selected according to the Hamming distances to solve this question. Adaptive crossing and mutation probability method also is presented to optimize the population and find the global solution. Secondly, a multi-aim optimal designing method which is based on AGA is applied in the cooperation control of power system stabilizer (PSS) and static compensator (STATCOM). Simulation results show that, used the solution presented in the paper, the stability of power angle and voltage can be effectively enhanced.

One Phase to Three Phase Converter Based on Thyristor Controlled Reactor

The technology of converting one phase AC to three phase AC should be widely used in electric railway and mountainous area which is out of the way. But the technology has not been solved well for a long time. It is necessary to find a one phase to three phase way to satisfy those occasions which need no-high request and reasonable price. This paper introduces the basic theory of converting one phase AC to three phase AC , and gives out two theory schemes to realizes it, introduces the working theory of TCR (Thyristor Controlled Reactor). According to the theory of one phase AC to three phase AC and the theory of TCR, give out the one phase to three phase converter based on TCR. Educes the one phase to three phase converter which is conformable to electric railway and mountainous area which is out of the way. At last, the simulation with MATLAB/Simulink is gived out to validate the controlling strategy.

Modeling and Simulation of Lightning Electromagnetic Transient and Identification of Shielding Failure and Back Striking in ±800kV UHVDC Transmission Lines - Part I: Modeling and Simulation of Lightni

Lightning stroke to transmission lines was introduced in this paper. Modeling and implementation method of tower, corona and insulator for lightning electromagnetic transient research was discussed. Comprehensive model for study of UHVDC lightning electromagnetic transient was built, and lightning caused fault and lightning disturbance were simulated in PSCAD/EMTDC based on the model, which offered a research platform for identification of shielding failure and back striking in plusmn800 kV UHVDC transmission lines.