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Wang L.,Chongqing University | Zhou H.-X.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | Luo J.,Chongqing University | Tang Z.-D.,Chongqing University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2014

This paper proposes a switching scheme by controlling the inverter in the UPS to meet the demand of uninterrupted power supply for important load. It can make the load such as inductor motors get supplied by the stand-by power after power failure quickly and smoothly. The operational mechanism of the inductor motor is analyzed and the variation of the residual voltage and the influence factors of the impact current are explained. The inverter in the UPS is in Space Vector Modulation (SVPWM), which can immediately track the residual voltage to support the motor. It controls the phase of the output voltage of the inverter toward the stand-by power and makes the switching of the power supply smooth. This phase control scheme can make the power switch for the inductor motor succeed avoiding the impact of the surge current when the phase difference exists. The validity and the feasibility are convinced by the theoretical analysis and the simulation by Simulink as well as experiments in the laboratory. ©, 2014, Power System Protection and Control Press. All right reserved. Source

Yan L.-F.,South China University of Technology | Liu G.,South China University of Technology | Liu J.-N.,Dongguan Power Supply Bureau of Guangdong Power Grid Company
Gaoya Dianqi/High Voltage Apparatus | Year: 2012

It is difficult for experimental methods be used in directly investigating the effects of impurities on internal electric field of power capacitors. In this paper, considering the structure of plate edge, the finite element analysis is adopted for electric field simulation. Simulation of the internal field and the actual operation experience of power capacitors verify the rationality of the improved capacitor element model proposed in this paper. Simulation results illustrate the effects of metal impurities with different diameters and at different locations on the electric field distribution in a capacitor. Source

Liu S.,Guangdong Electric Power Research Institute | Wang C.,CAS Shenyang Institute of Metal Research | Deng J.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | Li X.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | And 2 more authors.
Journal of the Chinese Society of Corrosion and Protection | Year: 2016

Epoxy based conductive anti-corrosion coatings were prepared on the surface of grounding grid Q235 carbon steel with graphite, carbon fiber andaluminum tripolyphosphateas pigments. The influence of the pigment/binder ratio (PBR) on the properties of the coatings was investigated such as the morphology and the electric conductivity of the coatings as well the corrosion behavior of Q235 carbon steel coated by coatings with an optimal PBR by immersion in salt solutions and burying in a selected soil from Shenyang test site. The results indicated that after buried in the soil, the bare Q235 steel suffered from serious corrosion and bubbles occurred on the E44 lacquer coating on the steel, in the contrast, the coatings with the optimal PBR showed excellent protectiveness for the steel even after buried for up to 1000 h in the soil. The volume resistivity and surface contact resistivity of the coatings are 0.65 Ω·cm and 8.72 Ω/cm2 respectively. The coatings exhibited excellent with standing capacity to high current impulse, such as their electrical resistance decreased by 5.95% and 11.09% for the ones suffered from a high current impulse of 1 kA for 20 times and a power frequency current of 10 A for 5 times respectively, while the surface of the coatings maintained unchanged without any destruction. © 2015, Chinese Society of Corrosion and Protection. All Rights Reserved. Source

Wei Z.,Guangdong Electric Power Research Institute | Zhong G.,Guangdong Electric Power Research Institute | Su W.,Guangdong Electric Power Research Institute | Wang W.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | And 3 more authors.
Journal of Energy Engineering | Year: 2016

A battery pack system composed of 32 lithium iron phosphate (LiFePO4) batteries and a battery management system (BMS) were assembled according to the actual load demand of a standard 110 kV power substation. Float-charging characteristics of the system were investigated and the results showed that 97% of its initial capacity was retained after a 1-year float-charging test. Even though the voltages of two batteries showed abnormal changes, which indicated that internal changes had occurred after long-term float charging, 94% of the batteries remained stable. All of the results suggested that the use of a lithium iron phosphate battery holds promise as a substitute for the conventional valve-regulated lead-acid (VRLA) battery in a direct-current power supply system. © 2015 American Society of Civil Engineers. Source

Xie L.,Chongqing University | Xie K.-G.,Chongqing University | He J.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | Zhai Z.-H.,Dongguan Power Supply Bureau of Guangdong Power Grid Company | Hu B.,Chongqing University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

Once upper distribution network is failed or power quality does not meet requirements, micro-grid coordinates various micro-generations output by switching to a pre-set control strategy to ensure normal island operation. During island operation, different control strategies affect micro-grid's supply reliability directly. Through analysis of micro-grid's two most common control strategies (master-slave and peer-peer), this paper builds micro-grid power model taking into account control strategies and proposes sequential Monte Carlo reliability evaluation method of grid-connected micro-gird through main power grid's minimal path equivalent and micro-grid breakdown influence matrix under different control strategies. Through evaluating the improved IEEE-RBTS using this method, reliability impact of two control srategies is analyzed. The illustrative example shows that micro-grid can improve the reliability performance of distribution network; and reliability of micro-grid with peer-peer control strategy is higher than micro-grid with master-slave control strategy. Source

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