With the continuous extension of Smart grid from the grid side to the user side, the expansion of emerging business is deepening day by day. In terms of terminal access quantity demand of provincial companies, from th...
With the continuous extension of Smart grid from the grid side to the user side, the expansion of emerging business is deepening day by day. In terms of terminal access quantity demand of provincial companies, from the original substation of 100 kilo level to the 10 kV distribution system of 100 000 class and the user terminal of 1 million or even 100 million level. Therefore, massive terminal communication is an urgent problem to be solved in power communication network. At present, the stategridcorporation of China is planning to build terminal communication access network, mainly using optical fiber and Narrow Band Internet of Things wireless technology, mainly to solve the 10kV distribution system; and the communication access of tens of millions or even hundreds of millions of user terminals urgently needs a suitable communication technology to solve. At present, NB-IOT technology has the characteristics of enhanced coverage, ultra-low power consumption, mass access, etc., which can meet the above requirements. This paper mainly describes the construction of NB-IOT technology adaptability evaluation index system, introduces the evaluation method of power narrowband Internet of things, and the evaluation results and analysis of adaptability.
According to the signal characteristics of power frequency communication, in order to solve the problem of poor anti-interference ability of time-domain difference method, a time-frequency detection method based on wa...
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ISBN:
(数字)9781728181417
ISBN:
(纸本)9781728181424
According to the signal characteristics of power frequency communication, in order to solve the problem of poor anti-interference ability of time-domain difference method, a time-frequency detection method based on wavelet scale spectrum rearrangement is proposed. This paper discusses the reason why the accuracy of time domain and frequency domain information of wavelet transform restrict each other. The scale spectrum is rearranged to the center of gravity of local energy to obtain more accurate time-frequency information. The characteristics of scale spectrum rearrangement algorithm are analyzed in detail, and the efficiency of the detection method is verified by the actual communication experiments.
Laser wireless power supply technology has the advantages of high energy density, good directionality, small transmitting and receiving aperture, convenient and flexible installation and deployment. It is very suitabl...
Laser wireless power supply technology has the advantages of high energy density, good directionality, small transmitting and receiving aperture, convenient and flexible installation and deployment. It is very suitable for power supply for sensors or mobile electrical equipment in complex high potential environment, such as patrol UAV. Because the beam quality of high-power semiconductor laser is far worse than that of other types of lasers, when it is used as the transmitter of beam shaping system, it must be equipped with corresponding beam shaping system to obtain laser beam with uniform spot, appropriate size and small divergence angle, so as to ensure that the photoelectric cell module has high conversion efficiency and meet the needs of long-distance laser transmission. In this paper, a beam collimation scheme based on aspheric lens group is designed, which integrates optical devices with low cost, reduces the energy loss in the process of laser transmission, and obtains laser beam with certain intensity uniformity. The test shows that the collimator can better meet the parameter requirements of the collimation system.
The ultra-high voltage(UHV) AC thyristor valve-type controllable arrester can realize the access and exit of the controllable unit through the action characteristics of the thyristor, dynamically change the volt-amper...
The ultra-high voltage(UHV) AC thyristor valve-type controllable arrester can realize the access and exit of the controllable unit through the action characteristics of the thyristor, dynamically change the volt-ampere characteristics of the arrester connected to the system, to reliably and deeply suppress the operating overvoltage. Under continuous operating voltage, stray capacitance will cause the uneven distribution of axial potential at the high-voltage end of the thyristor valve. In severe cases, the thyristor with higher voltage may be triggered by mistake, which endangers the system security. Due to the more changeable potential distribution of thyristor valve under different ambient temperatures and charge rates, higher requirements are put forward for the design and application of the thyristor valve. Therefore, based on the test data, this paper simulates and analyzes the influence of the voltage and temperature changes of the thyristor and resistor on the potential distribution of the thyristor valve under the continuous operating voltage, analyzes and compares the configuration modes of various voltage equalizng capacitors, and obtains the voltage equalizng measures with better optimization effect, which provides a reference for the voltage equalizng optimization of the thyristor valve.
In this paper, we aim at designing topology search engine based on graph databases. Compared with traditional relational graph databases, graph databases are potential solutions to analyzing large-scale highly-connect...
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ISBN:
(纸本)9781509064151;9781509064144
In this paper, we aim at designing topology search engine based on graph databases. Compared with traditional relational graph databases, graph databases are potential solutions to analyzing large-scale highly-connected data. Firstly,we propose an analysis framework of topology search engine based on graph databases. Secondly, the three chosen topology search functions, i.e., electrified state initialization, branch outage simulation and power supply range analysis are realized in the topology search engine. Thirdly, a group of simulations are conducted to compare the performances of the topology search functions between graph databases and relational databases.
Web scraping techniques based on XPath enable users to consistently extract information of interest from webpages that do not provide a structured interface. However, XPath-based extraction is likely to fail when enco...
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With the large-scale construction of digital substation, digital energy metering technology based on IEC 61850 standard is widely used. In this paper the research and application status of digital energy metering tech...
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ISBN:
(纸本)9781509050369;9781509050352
With the large-scale construction of digital substation, digital energy metering technology based on IEC 61850 standard is widely used. In this paper the research and application status of digital energy metering technology is summarized. The structure of digital substation and the composition of digital measurement system are introduced. The research and development status of key equipment such as electronic transformers, merging units and digital energy meters in digital measurement system are expounded, and the characteristics of digital metering system are summarized. Finally, the key technology problems in digital measurement system are discussed in terms of the reliability of electronic transformer, measurement algorithm of the digital power meter and the calibration method of electronic transformer and digital energy meter.
According to the complementarity of photovoltaic and battery generation,the structure of photovoltaic and hierarchical storage system and its typical control methods are described in this paper,considering the demand ...
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According to the complementarity of photovoltaic and battery generation,the structure of photovoltaic and hierarchical storage system and its typical control methods are described in this paper,considering the demand of load side and distribution gird,hierarchical control strategy including primary control and secondary control is discussed,the model of converters and the control loop are presented in *** overall structure of hierarchical control composed by P-Q control and voltage-phase droop control is brief and cost-less.A simulation of the basic part in hierarchical control strategy under PSCAD/EMTDC environment is also included in this *** evaluation of hierarchical control strategy shows that photovoltaic and hierarchical storage system is practical for the application of distributed generators.
A set of blackout risk assessment indexes is established according to Electricity Accident (Incident) Investigation Procedures of China Southern powergrid (CSPG) (pilot) and Guide on Operational Risk Evaluation of CS...
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ISBN:
(纸本)9783038351153
A set of blackout risk assessment indexes is established according to Electricity Accident (Incident) Investigation Procedures of China Southern powergrid (CSPG) (pilot) and Guide on Operational Risk Evaluation of CSPG, which can calculate risk values of electricity accidents (incidents). The calculation process is discussed in detail. Based on the proposed indexes and OPA blackout model, a blackout risk assessment method for power system is put forward, with which blackout risk for all 500kV buses in Guangdong powergrid are evaluated. Weak areas in power system are identified and their inducements are analyzed. The identification results accord with actual system long-term operation experience, which verifies the correctness of the indexes and method.
Content-based publish/subscribe systems allow subscribers to specify interests based on event contents, rather than pre-assigned event topics. Since most of existing publish/subscribe systems use FIFO (First In First ...
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ISBN:
(纸本)9781479932153
Content-based publish/subscribe systems allow subscribers to specify interests based on event contents, rather than pre-assigned event topics. Since most of existing publish/subscribe systems use FIFO (First In First Out) as its queue management mechanism, it may face network congestion coming from suddenly burst of huge amount of subscription messages as well as event notifications. To promote the ability to handle congestion challenge, we present a new queue management mechanism called queue reorganization algorithm. By taking advantage of similarities among concurrent subscriptions, queue reorganization algorithm can make covering subscriptions as proxies and remove unnecessary subscriptions at each broker, which in turn greatly reduces pressure from congested input queue. Detailed evaluations under various workloads show significant benefits of the optimizations in terms of input queue size and message routing cost.
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