This paper presents a new non-unit voltage protection algorithm for extra high voltage (EHV) transmission lines. This scheme is developed using wavelet analysis, in which the singularity of fault transient voltage sig...
详细信息
This paper presents a new non-unit voltage protection algorithm for extra high voltage (EHV) transmission lines. This scheme is developed using wavelet analysis, in which the singularity of fault transient voltage signals in one terminal is utilized to discriminate clearly between internal and external faults. Lipschitz exponent (LE) is obtained from wavelet modulus maximum to detect singularity of signals. A typical 500-kV EHV transmission system has been simulated by ATP to evaluate the scheme. The simulation results show that this scheme is capable of providing correct responses under various system configurations and fault conditions
This paper puts forward a novel topology of controllable reactor, the structure is based on many small capacity thyristor controlled reactor (TCR) modules and a three-windings transformer connecting to system. The tra...
详细信息
This paper puts forward a novel topology of controllable reactor, the structure is based on many small capacity thyristor controlled reactor (TCR) modules and a three-windings transformer connecting to system. The transformer secondary adopts duplex winding structure and each has multi-bank TCR modules being in delta connection. In this topology, the harmonic current injected into the powersystem is very small. It not only possesses all the functions a traditional TCR has, but also has many other merits such as occupying small floor space, generating little loss, easy implement control and protection scheme, and high reliability etc. A 500 kVar industrial prototype is under construction in Langfang, Hebei province of ***. Digital simulation based on EMTDC/PSCAD and field test were carried out to verify the perfect harmonics characteristics of topology proposed
A new load detection method was presented based on its running status of powersystem. The loads are sorted according to their index of capacitive, inductive, and none-linear. The static character of each load was got...
详细信息
A novel method is put forward, which the power meter can be read based on compute vision, and the architecture of remote meter auto reading system is designed. Different with the normal automatic meter reading system ...
详细信息
In this paper, a novel HVDC transmission system is presented which is with parallel large capacitor connected in the DC side of the rectifier (shorted form HVDC-C). The fundamental principle and technology characteris...
详细信息
In this paper, a novel HVDC transmission system is presented which is with parallel large capacitor connected in the DC side of the rectifier (shorted form HVDC-C). The fundamental principle and technology characteristics of HVDC-C are analyzed. The study shows that HVDC-C reduces the component of harmonic voltage and harmonic current both side in AC system and DC transmission line, makes control strategy more flexible and the filter structure more simple, etc. Furthermore, the control method, contrast to conventional HVDC and application foreground of HVDC-C is discussed briefly. The simulations based on PSCAD/EMTDC show that HVDC-C can operate steadily, has the capability to restore steadily when short circuit fault occurs, and is feasible technically and obvious in advantages
It's important to make an accurate PD location in transformers for fault diagnosis and maintenances of powersystems. Theoretically it's possible to locate the PD source by measuring the differences in the arr...
详细信息
It's important to make an accurate PD location in transformers for fault diagnosis and maintenances of powersystems. Theoretically it's possible to locate the PD source by measuring the differences in the arrival time at the UHF sensor array. The propagation velocity of EM wave in air is 30 cm/ns, which is extremely fast, so the resolution of the time-delay of UHF signals detected at the UHF sensor array is one of the key points to make an accurate PD location. Here, we propose a mathematical method: cross-correlation-shifting-averaging algorithm that can improve the resolution of the UHF signal's time-delay by increasing the signal to noise ratio and reducing the time dispersion caused by the random nature of PD. The practical processing results of experimental data from our laboratory indicate that the method can increase the time-delay resolution by nano-seconds in some cases, which improve PD location accuracy by tens of centimeters.
This paper presents an identification method based on the iterative Prony to identify transfer function and configure PSS parameters using residue way. The iterative Prony is a very useful method to acquire power syst...
详细信息
This paper presents an identification method based on the iterative Prony to identify transfer function and configure PSS parameters using residue way. The iterative Prony is a very useful method to acquire powersystem oscillation modes, by which the system eigenvalue, oscillation frequency, amplitude, damping and relative phase can be directly estimated using the response of given input signals. Considering the influence of input signal on output signal, the iterative Prony can acquire the transfer function of powersystem, then, according to the corresponding residues we conducted coordinated setting of powersystem stabilizer (PSS) by residue method. The simulation results for two testing system examples prove that this proposal method is effective in the powersystem oscillation mode analysis and parameters determination of PSS, can improve eigenvalues of system and can enhance system damping after PSSs whose parameters are optimized by above method are built into powersystem
Based on rough set, this paper use discernibility matrix to reduce the condition attributes. The reduced samples are laid by weighted mean roughness to avoid blindness and redundancy. By this method, model space can b...
详细信息
Based on rough set, this paper use discernibility matrix to reduce the condition attributes. The reduced samples are laid by weighted mean roughness to avoid blindness and redundancy. By this method, model space can be compressed greatly and weighted mean roughness is easy to calculate. Weighted mean roughness is used to separate attributes' priority in every lay, which make the diagnosis system had strong tolerant ability. When the electric power grid is fault, the result of diagnosis will be correct by searching every lay with priority level. The correctness and effectiveness are validated by the analysis result of emulation
Harmonic pollution and reactive power compensation are the important power quality problems. This paper proposes a combined power filter system consisting of the parallel operation of a hybrid active power filter (HAP...
详细信息
Harmonic pollution and reactive power compensation are the important power quality problems. This paper proposes a combined power filter system consisting of the parallel operation of a hybrid active power filter (HAPF) and the passive power filters or capacitors. The HAPF is formed by a single tuned LC filter per phase and a small-rated three-phase active filter, which are directly connected in series. The characteristics of the combined system and the harmonic current detection method using the combination of load current and the mains current are analyzed and simulated. The simulation results show that good filter performance can be obtained by the combined system. Experimental results from a 100 kVA/380 V hardware prototype parallel operation with capacitors are presented to conform the validity and effectiveness of the combined system
This paper focuses on the research on the DC bias due to magnetic storm and HVDC. In the paper, we introduce the DC bias problem of Jiangsu Yang-Huai transmit electric system and Southern power Grids, discuss the harm...
详细信息
This paper focuses on the research on the DC bias due to magnetic storm and HVDC. In the paper, we introduce the DC bias problem of Jiangsu Yang-Huai transmit electric system and Southern power Grids, discuss the harmful effect of the transformer DC bias and the significance of research, and analyze the compensation, weakening and elimination of transformer bias current. Finally, the problems that should be paid attention to and some corresponding suggestions are proposed
暂无评论