Half-wavelength AC transmission (HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the systempower frequency. The countries with a large territory h...
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ISBN:
(纸本)9781509041695
Half-wavelength AC transmission (HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the systempower frequency. The countries with a large territory have a big demand for HWACT. The fault characteristics of an HWACT line can be different from those of a conventional transmission line. So it is necessary and significant to analyze the fault characteristics of an HWACT line. In this paper, the influence of fault distances and fault resistances on the fault voltages and currents of two buses is analyzed after different types of faults occur on an HWACT line. And the analysis results are compared with the simulation results from EMTP.
In this paper, we consider the design of linear precoding in Multiple Input Multiple Output （MIMO） power Line Communication （PLC） systems with finite-alphabet input. First, we derive mutual information of MIMO-PLC...
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In this paper, we consider the design of linear precoding in Multiple Input Multiple Output （MIMO） power Line Communication （PLC） systems with finite-alphabet input. First, we derive mutual information of MIMO-PLC systems with impulsive noise. Considering the non-concavity of the objective function and the low-cost requirement of PLC systems, we choose the lower bound of the mutual information as the objective function. Subsequently, we propose a novel approach to design the precoding scheme to reduce computational complexity. Specifically, our work primarily includes the following two contributions： （1） We design the right unitary matrix that is a product of two fixed unitary matrices, which only depends on the modulation mode. Hence, the results can be saved and require less computations. （2） For the power allocation matrix, we first reduce the space of power allocation using constraints of the optimal power allocation policy. Consequently, we propose a non-linear search method to obtain the optimal power allocation in small space. In regards to the computational complexity of the analysis, we conclude that the proposed precoding matrix design scheme has low complexity and is easy to implement. Moreover, the numerical results are proven to demonstrate the performance of the proposed precoding design scheme.
As for aero-engine,it is relatively difficult to obtain the displacement signal,only to measure the acceleration *** the paper,aimed at the dual-rotor system test rig,the rub-impact is simulated and the acceleration s...
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ISBN:
(纸本)9781510868434
As for aero-engine,it is relatively difficult to obtain the displacement signal,only to measure the acceleration *** the paper,aimed at the dual-rotor system test rig,the rub-impact is simulated and the acceleration signals collected from the bearing pedestal are analysed to extract the rubbing faults' ***-component extraction is an available method for vibration signal analysis of rotary machinery,so a novel method of rubbing fault diagnosis based on variational mode decomposition(VMD) is *** is a newly developed technique for adaptive signal decomposition,which can non-recursive decompose a multi-component signal into a number of quasi-orthogonal intrinsic mode *** the rub-impact fault occurs in the dual-rotor system,the acceleration vibration signals of the dual-rotor system will present amplitude-modulated feature because of the periodic rub-impact between the rotor and the *** is then applied to detect multiple rubbing-caused signatures for rotor-stator fault diagnosis via practical vibration *** using VMD,the rub-impact signal,background signal and noise signal can be separated efficiently and the fault feature of vibration signal of a rotor system with local rub-impact fault can be ***,the VMD method can be applied to the rub-impact fault diagnosis of the rotor systems efficiently.
Very fast transient over-voltage (VFTO), induced by disconnector operations in gas-insulated switchgears, has become the limiting dielectric stress at ultra-high voltage levels. Much work has been done to investigate ...
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Very fast transient over-voltage (VFTO), induced by disconnector operations in gas-insulated switchgears, has become the limiting dielectric stress at ultra-high voltage levels. Much work has been done to investigate single-strike waveforms of VFTO. However, little study has been carried out investigating the repeated strike process, which would influence VFTO significantly. In this paper, we carried out 450 effective experiments in an ultra-high voltage test circuit, and conducted calculations through the Monte Carlo simulation method, to investigate the repeated strike process. Firstly, the mechanism of the repeated strike process is proposed, based on the experimental results. Afterwards, statistical breakdown characteristics of disconnectors are obtained and analyzed. Finally, simulations of the repeated strike process are conducted, which indicate that the dielectric strength recovery speed and polarity effect factor have a joint effect on VFTO. This study enhances the understanding of the nature of VFTO, and may help to optimize the disconnector designed to minimize VFTO.
Wireless power transfer has been recognized as a promising technology for electric vehicles charging. However, the parking misalignments between the transmitter coil on the ground and the receiver coil inside the car ...
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ISBN:
(纸本)9781509007387
Wireless power transfer has been recognized as a promising technology for electric vehicles charging. However, the parking misalignments between the transmitter coil on the ground and the receiver coil inside the car may cause variations in the mutual inductance for the charging system, which will reduce its transfer power and efficiency. In order to improve the transfer efficiency and optimize the operating condition, it is essential to identify the mutual inductance. In this paper, identification models are studied with and without communication feedback from the receiver coil under two typical cases (resonant transmitter and inductive transmitter). A selection method based on sensitivity analysis is proposed to select models of high accuracy against measurement errors and sampling propagations. simulation and experimental results verify the effectiveness and validity of the proposed method. This work is helpful for evaluating and improving the wireless charging system's tolerance against misalignments as well as optimizing its operation condition.
Travelling wave (TW) differential protection fully utilizes the fault information contained in TW at both terminals of a transmission line, so it's a protection with high reliability and high selectivity. However,...
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Travelling wave (TW) differential protection fully utilizes the fault information contained in TW at both terminals of a transmission line, so it's a protection with high reliability and high selectivity. However, because TW differential protection needs a large amount of communication, it cannot be put into practical use. This paper proposes a TW differential protection which is based on equivalent travelling wave (ETW). Fault information is not lost during the process of getting ETW, so the proposed protection has the same reliability and selectivity with traditional TW differential protection. Because only several modulus maxima are needed to be sent to the opposite terminal, the traffic is largely reduced and the protection can operate much more rapidly. Extensive simulations validate the proposed protection.
The active participation of demand side resources in power grid operation not only benefits the individual participant but also benefits the whole system. The optimal goal can promote by excavating the active behavior...
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ISBN:
(纸本)9781538614280
The active participation of demand side resources in power grid operation not only benefits the individual participant but also benefits the whole system. The optimal goal can promote by excavating the active behaviors of demand side. The welfare maximization of market participant is the driving force of such active behaviors. Considering the independence of each user's behavior, the consumer's utility function is selected to depict consumer's preference and demand response behavior. In order to coordinate the consumers' maximum welfare with social welfare maximization, consumers' utility function and units' operation cost are integrated into Unit Commitment (UC) model. The objective function is to maximize social welfare, by subtracting units' operation cost from consumers' total utility, and this objective can be acquired. Considering the proposed model should be solved in a distributed manner, the idea of the centralized coordination and the decentralized decision-making is proposed. Based on the Lagrangian relaxation (LR) principle and distributed real-time pricing scheme, a closed-loop feedback mechanism is constructed to reflect the relationship among generator output, price level, and load demand. The ten generating units example can illustrate the effectiveness of the proposed method.
With the development of smart grid, the self-healing ability of protection device becomes much more important. Pilot protection is of good selectivity, but it needs a highly reliable communication network. Once the co...
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With the development of smart grid, the self-healing ability of protection device becomes much more important. Pilot protection is of good selectivity, but it needs a highly reliable communication network. Once the communication line between two devices is out of work, pilot protection will be forced out of operation. Since there are many ring structures in communication network, circuitous routes can be found to help pilot protection remain operational. In this paper, ant colony algorithm (ACA) are used to find the optimal circuitous route, and simulation results show the method is fast and accurate. To the actual communication network of powersystem, each node is just connected to a few other nodes, so the search process often come to dead ends. Use penalty functions can reduce the probability of coming to a dead end and improve the algorithm efficiency. The whole route accelerating penalty function is most efficient.
The implementation of transmission expansion planning towards low carbon development can effectively alleviate the "carbon lock" effect in the power industry and facilitate the transition to low carbon power...
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