When a single-phase grounding fault occurs in the low-current grounding system,the fault characteristic of the zero-sequence current is weak and highly complex,therefore the reliability of the traditional line selection method is badly in need of improvement.To address this issue,a fault line selection method for distribution networks based on variational mode decomposition(VMD)and dilated convolutional neural network is proposed in this paper.Firstly,the electrical characteristics of healthy lines and faulty lines are analyzed,and zero-sequence current is used as fault characteristic signal to provide theoretical basis for the input of the line selection model.Secondly,the zero-sequence current sequence is decomposed into different frequency intrinsic mode functions(IMF)using the VMD technique to enhance the stability and distinctiveness of the fault signal features.Secondly,dilated convolutional neural network is used as line selection network to improve the adaptive classification ability of the model by enlarging the receptive field of convolutional operation.Finally,a 10 kV distribution network is constructed in MATLAB/Simulink for the case study analysis.The results suggest that the proposed method yields favorable conductor selection outcomes across various fault scenarios,thus verifying the robustness and accuracy of the proposed approach.
Although some results have been obtained in the analysis of factors affecting commutation failure,but the influence of fault clearance time(fault division angle)on commutation failure still needs to be studied further.Firstly,based on the commutation failure process,the effect of zero-crossing offset angle on the turn-off angle is analyzed.Secondly,based on the time area of commutation voltage,the influence of different initial fault angles on the first commutation failure of the inverter is analyzed,and the influence of fault division angle and zero-crossing offset angle on subsequent commutation failure is further analyzed.It is found that the risk of subsequent commutation failure is greatest when the fault is cleared in commutation.Finally,taking single-phase grounding fault as an example,simulation test results of different initial fault angles and fault division angle based on PSCAD/EMTDC and CIGRE HVDC models verify the correctness of the theoretical analysis.
In order to ensure the stability of the transmission voltage and effectively control the operation of the DC transmission system in the event of three-phase short circuit fault, this paper proposes a DC transmission system operation control method based on multilevel converter module (MMC). The multilevel converter module is designed by using the anti parallel diode and parallel capacitor to obtain the AC equivalent inductance, ensure that the AC/DC flow of the converter station is the same as the active power, and clarify the power situation in the converter station; The module is combined with the feedforward decoupling compensation term, and the PI is used to obtain the input value of the current inner loop operation controller to realize current decoupling, increase the stability control of DC voltage, and improve the anti-interference of the transmission system; The corresponding reference value is obtained through the correction and control link, and the optimal operation control result is obtained. The experiment proves that the designed module can ensure the smooth operation of the power transmission system under normal working conditions, control the impact in a safe range when a fault occurs, and ensure the stability of the power transmission system.
With the increasing penetration of distributed renewable energy and flexible loads in the distribution network, the traditional distribution network is gradually transitioning to an active distribution network. Due to the vigorous development of new power system, the economic dispatch of active distribution network faces great challenges. Therefore, this paper introduces V2G technology while considering the carbon emission of the system, establishes an orderly charging and discharging model for electric vehicles and then builds demand response modeling based on transferable load and interruptible load, and then conducts second-order cone relaxation on the branch power flow constraints of the distribution network. Finally, With the goal of minimizing the dispatch cost for active distribution network, this paper proposes a low-carbon economic dispatch model for active distribution network considering V2G and demand response. The Case studies of IEEE 33-node power distribution system verifies that the proposed model can effectively reduce the dispatch cost, enhance the security of system operation and reduce carbon emission.
Since Age of Information (AoI) has been proposed as a metric that quantifies the freshness of information updates in a communication system, there has been a constant effort in understanding and optimizing different statistics of the AoI process for classical queueing systems. In addition to classical queuing systems, more recently, systems with no queue or a unit capacity queue storing the latest packet have been gaining importance as storing and transmitting older packets do not reduce AoI at the receiver. Following this line of research, we study the distribution of AoI for the GI/GI/1/1 and GI/GI/1/2* systems, under non-preemptive scheduling. For any single-source-single-server queueing system, we derive, using sample path analysis, a fundamental result that characterizes the AoI violation probability, and use it to obtain closed-form expressions for D/GI/1/1, M/GI/1/1 as well as systems that use zero-wait policy. Further, when exact results are not tractable, we present a simple methodology for obtaining upper bounds for the violation probability for both GI/GI/1/1 and GI/GI/1/2* systems. An interesting feature of the proposed upper bounds is that, if the departure rate is given, they overestimate the violation probability by at most a value that decreases with the arrival rate. Thus, given the departure rate and for a fixed average service, the bounds are tighter at higher utilization.
