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Nowadays, harmonic active power direction method is the most widely applied method to judge the main harmonic source, but the power direction method is theoretically different from harmonic current superposition principle. In this paper, it has been got that the power direction method and harmonic current superposition principle are different through mathematical analysis, and the precise conditions...
10kV cross-linked polyethylene (XLPE) cables are widely used in power system because of its advantages of small external influence factors and high reliability and safety. However, cable accessories are weak links of the cable lines. Considering the hot and humid environment in Guangzhou areas, the applicability of cold and hot shrinkable cable accessories is questionable. This paper has carried out...
High voltage transmission line fault location algorithm without synchronization, which does not require sampling synchronization, reduces cost and has a higher practical engineering value. But the algorithm still needs to be improved in the false root identification of ranging equation, this paper makes a further research on this issue. Firstly, the false root problem of fault location algorithm without...
With obvious economic and social benefits, four-parallel lines on the same tower is widely used and has high reliability requirements, the use of live working to carry out maintenance is particularly important. This paper takes 500/220kV four-parallel lines on the same tower as the research object. First, through the analysis of the risk of 500kV and 220kV line typical operation position, it can be...
The use of nonlinear power electronic loads and new energy power generations make harmonic injection to the grid inevitable, lead to transmission line more additional harmonic losses and significant economic losses. Based on the mechanism of harmonic losses, this paper derived current density distribution formula for transmission line, a more precise calculation method of each harmonic resistance...
Numerical study of atmospheric ice accretion on circular conductors in triplex configuration has been carried out at different operating and geometric conditions to get an understanding of ice accretion along conductors in triplex configuration and analyze the effects of changing distance between the conductors. The analysis were carried out for three different cases, where distance between circular...
A pilot protection method of T-connected transmission lines is proposed in this paper. First, the startup information of each segment in three-terminal of T-connected transmission lines can be obtained. On this basis, the pilot protection fault identification criterion can be constructed. Then, according to this criterion, the fault position can be located quickly and accurately. This method simplifies...
The characteristic to shield harmonics of the novel converter transformers is presented in this paper. Then design the DC transmission system of the novel transformer to achieve harmonics shielding function, by adopting the novel transformer on the rectifier side. Based on the calculation method of harmonic content in the HVDC system, calculate and allocate the reactive power compensation on both...
This paper proposes a coordinated voltage control of synchronous condensers using wide-area measurements. The control is able to determine a coordinated control scheme of synchronous condensers to maintain stable post-fault voltages. A voltage control model with synchronous condensers has been established using wide-area measurements. By applying Networked predictive control (NPC), the time delay...
An electromagnetic transient simulation model of 500 kV HVDC Power Networks in Hubei province is established. According to the actual configuration and parameters, all the primary electrical devices in 500 kV AC/DC hybrid power grids are modeled in detail, including HVDC converter, AC/DC transformers, AC/DC breakers, filters, reactors, transmission lines, grounding polar, and all the other power elements...
In recent years, with the advantages of long distance and large capacity, ultrahigh voltage direct current (UHVDC) transmission projects are developing increasingly in China. Also UHVDC transmission projects share corridors with underground oil & gas pipelines has become increasingly prominent. UHVDC ground electrode influences underground oil & gas pipeline is a new problem in China with...
Asynchronous motor is vital for trades and occupations because of simple structure, the reliable running, the convenient service and cheap price. However, it is generally known that motor which is direct-on starting has many malpractices. When electrical machinery light-loading running, the power lose increases, the efficiency and power factors both reduce greatly. Therefore it has extremely vital...
The Conventional Sliding Mode Observer (SMO) collects the rotor position angle information by identifying rotor position angle and needs to introduce phase-locked loop (PLL) to realize the reverse control. It has certain limitations including massive calculation, slow dynamic response and complex methods and not taking the effect from the inverter dead-time on the estimation model into consideration...
According to the mathematical model of a brushless DC motor, using MATLAB / Simulink to build various independent functional modules, and integrated into the simulation model of brushless DC motor control system. The system uses the double loop of control mode, including the inner current loop and the outer speed loop, to ensure that the motor is performance well in the high and low speed, and system...
This paper analyzes the transient process of a DFIG based wind turbine in detail during general grid voltage swell conditions, especially the symmetrical voltage swell cases. And the key points influencing the turbines' high voltage ride-through (HVRT) capability is then evaluated. Furthermore, a HVRT control scheme, based on the resonant control, is put forward, which can meet the grid codes' reactive...
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