The integration and accommodation of the wind and solar energy pose great challenges on today’s power system operation due to the intermittent nature and volatility of the wind and solar *** efficient large-scale ele...
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The integration and accommodation of the wind and solar energy pose great challenges on today’s power system operation due to the intermittent nature and volatility of the wind and solar *** efficient large-scale electrical energy storage is one of the most effective and economical solutions to those *** the comprehensive review of the existing storage technologies,this paper proposes an overall design scheme for the Non-supplementary Fired Compressed Air Energy Storage(NFCAES)system,including system design,modeling and efficiency assessment,as well as protection and ***,the design principles of the multistage regenerative,*** recovery system which is used to fully recycle and utilize the waste heat from compression are provided,so as the overall system efficiency evaluation *** paper theoretically ascertains the storage decoupling rules in the potential and internal energy of molecular compressed air and reveals the conversion mechanism of gas,heat,power,electricity and other forms of *** this basis,a 500-k W physical simulation system of CAES system(TICC-500,Tsinghua-IPCCAS-CEPRI-CAES)is built,which passed a system-wide 420-k W load powergeneration test with less pollution and zero carbon ***,the multi-form energy conversion of multi-stage regenerative CAES and storage efficiency is verified,especially its incomparable superiority in solving the uncertainty problem in wind and solar power ***,the propaganda and application scenario of the CAES system in China is introduced.
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.
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 power system, 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.
This paper presents an optimal power flow model for AC/DC meshed networks with modular multi-level converter based HVDC transmission system (MMC-OPF). The MMC-OPF problem is formulated to minimize the total network lo...
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ISBN:
(纸本)9781509054190
This paper presents an optimal power flow model for AC/DC meshed networks with modular multi-level converter based HVDC transmission system (MMC-OPF). The MMC-OPF problem is formulated to minimize the total network loss of the whole AC/DC grids by adjusting generators and converters. In addition, a practical method is proposed to consider N-1 static security constraints with OPF calculation. Case studies of IEEE testing system and a practical network have been carried out. The results demonstrate the effectiveness of the method.
The characterization of the closed-loop delays in a wide-area control system (WACS) is an important foundation for further research. The method to estimate and measure the closed-loop delay in actual WACSs were propos...
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ISBN:
(纸本)9781509041695
The characterization of the closed-loop delays in a wide-area control system (WACS) is an important foundation for further research. The method to estimate and measure the closed-loop delay in actual WACSs were proposed in this paper. Then, the closed-loop delays in the actual WACS in Guizhou power Grid in China were measured and analyzed. Also, the measured delays were used to verify the normal distribution estimation model proposed in previous research. The results indicate that the closed-loop delay in the WACS followed a normal distribution.
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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Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR...
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Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR) which is widely used as insulation material for cable accessories. Long-term aging (0- 1000 h) experiments under the different voltages were conducted to observe electrical tree initiation and propagation processes. In trees initiation stage, with increasing of applied voltage, electrical tree initiation probability becomes larger, while tree initiation time dramatically decreases. The experiment observations demonstrated four shapes of trees which are dominated. As applied voltage increasing, the numbers of electrical trees life-cycles increased and exponential relationship was found between tree length and magnitude of applied voltage. It is noted that charges, whose energy exceeding a certain critical value, destroy microstructure of dielectric accumulatively via injection and extraction, and cause electrical trees initiate when it accumulates to a visible extent.
High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse ...
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High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse due to the limited fault current values and the situation is worse in wind farms. The mostly adopted HIF detection algorithms are based on the 3rd harmonic characteristic of the fault zero-sequence currents, whereas these 3rd harmonics are very easy to be polluted by wind power back-to-back converters. To solve this problem, the typical HIF arc flash based on Mayr's arc model is first built, and the typical fault waveforms of HIF in wind farm are presented. Then the characteristics of high impedance faults are analysed to distinguish the occurrence of HIF from other harmonic interference. After that, the performance of the traditional harmonic based HIF detection algorithm is discussed, and a novel detection algorithm is presented to prevent harmonic interference influence in wind farms.
When there is power supply shortage or emergency event in power system, orderly power utilization needs to be applied to cut down electricity demand to maintain power supply for important electricity consumers. Curren...
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