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Large crossing overhead transmission lines are usually erected on the ultra-high towers with long span, and its lightning withstand performance should be paid more attention to. Considering the propagation process of lightning current along the high tower, an improved simulation model of back striking was established by using the electromagnetic transient program, and then the lightning withstand performance of back striking under different conditions for the ± 1100kV UHVDC large crossing line were studied. The results show that comparing with the conventional transmission line for the ±1100kV UHVDC project, the large crossing section has a much lower lightning withstand level of back striking (LWLBS); The LWLBS for the large crossing line with high tower is not significantly affected by the footing resistance, while enhancing the insulation level can effectively improve the LWLBS. Furthermore, the LWLBS increases with the increase of the distance between striking point and the tower when lightning strikes the large crossing overhead ground wire.

The ideal Gaussian pulse can be more convenient to simulate the excitation of electromagnetic waves and its propagation characteristics, but the pulse and the actual local discharge current waveform is not exactly the same. At the same time, most of the previous research contents have adopted the simplified GIS simulation model, which does not take into account the influence of the arc of the basin insulator, the three-phase cotube, the shield electrode, the circuit breaker and so on, which may lead to the deviation of the actual electromagnetic wave propagation characteristics. In this paper, the real PD current signal of various insulation defects is used as the excitation source. Considering the actual structure inside the GIS, the propagation characteristics of the electromagnetic wave in the GIS are studied by using the electromagnetic simulation software XFDTD6.3.8.4. and the effects of different structures on the propagation characteristics of electromagnetic waves were studied.

With rich reserves and unique advantages, offshore wind resources has become an important development direction for the future wind power generation. However, since the characteristics of offshore wind power are different from that of onshore wind power, many key issues need further study, especially the probability of offshore wind turbine suffering from lightning strike is large, resulting in a high accident rate of lightning damage to the wind turbine facilities, which poses a serious threat to the safe and efficient operation of the offshore wind power generation. Hence, the lightning protection for offshore wind turbines is very important and necessary. In this paper, the research advances of lightning protection for offshore wind turbines were introduced from the aspects of physical mechanism of lightning attachment to offshore wind turbines, discharge characteristics and design of lightning receptor-current channel, the mechanical burst mechanism of the blade, and the strong-field electromagnetic transient effect, and accordingly proposed the major topics of lightning protection for offshore wind turbines to be further studied.

In order to meet the needs of smart distribution grid evaluation in different regions and different information integrity systems, this paper presents a comprehensive evaluation system (CES) based on analytic hierarchy process (AHP) and adaptive correction method. First, a hierarchical frame structure of the CES is put forward. Then, a detailed design of the comprehensive evaluation index system (CEIS) based on AHP method is given. A weighting system based on the adaptive correction method is used to list the evaluation process based on the analytic hierarchy process in detail. Finally, according to the actual situation of the smart distribution grid in a region, the validity and accuracy of the CES are verified. The calculation results show that the CES can assess the actual operation condition of the distribution grid accurately.

Similar to other major electrical apparatuses, the reliability and stability of the dc network is becoming the most important issue when using the voltage-source-converter-based multiterminal dc (VSC-MTDC) system for offshore wind power integration. A coordinated control strategy of VSC-MTDC named master–auxiliary is proposed by combining the advantages of the voltage margin and voltage droop control. This strategy has three advantages. First, the master converter station with the constant dc voltage control can provide reference to the system dc voltage and is helpful for the stabilization of dc voltage. Second, the integrated control of the dc voltage in both master and auxiliary converter stations are helpful for providing adequate active power control (APC) and restraining large power variation. Third, the APC converter station can serve as a backup for the dc voltage control in abnormal conditions. In order to guarantee the reliability and stability of the system under various operating conditions, this paper introduces the priority of dc voltage control to the coordination control strategy. Moreover, a parameter optimizing method of controllers for this strategy is also proposed. Finally, the effectiveness of the master–auxiliary control is verified by simulations under normal and abnormal conditions.

In this paper, new formulations of the power flow and continuation power flow that allow for electro-thermal coupling in transmission lines have been proposed. The new formulations capture the overhead lines' electro-thermal coupling effects by treating their series resistances as temperature dependent variables. They generate results that can differ from the results of conventional formulations markedly, particularly for problems centring on line impedances. The paper demonstrates this by applying the new formulations to the power transfer limit calculation. Generally, power transfer limits are defined either by encountering a line's thermal limit or detecting the onset of voltage collapse in the system. Studies based on 2-bus and 14-bus test systems are used to demonstrate the efficacy of the new formulations for both situations. For these studies, specific point-to-point power transfer limits are calculated with and without the lines' electro-thermal coupling effects and the results are compared.

This paper proposes a three-level transformer condition assessment model based on matter-element cloud theory and evidential reasoning decision-making theory. Both quantitative and qualitative factors are considered in the model. Matter-element cloud model is utilized to integrate the quantitative indices with their optimal weights to assess the condition of items, including Dissolved Gas Analysis(DGA), electrical testing and oil testing in the first level in the form of association degrees with state grades to generate the original basic probability assignments for the second-level model. D-S evidential reasoning decision-making model is utilized in the second level to assess the condition of systems including quantitative system and qualitative system and in the third level to assess condition of the overall transformer. Both fuzziness and randomness are taken into consideration in this model. Experimental cases confirm that the assessing model is capable of offering an overall assessment of the observed transformer condition and assisting the maintenance strategy development.

We propose doubly constrained robust least-squares constant modulus algorithm (LSCMA) to solve the problem of signal steering vector mismatches via the Bayesian method and worst-case performance optimization, which is based on the mismatches between the actual and presumed steering vectors. The weight vector is iteratively updated with penalty for the worst-case signal steering vector by the partial Taylor-series expansion and Lagrange multiplier method, in which the Lagrange multipliers can be optimally derived and incorporated at each step. A theoretical analysis for our proposed algorithm in terms of complexity cost, convergence performance, and SINR performance is presented in this paper. In contrast to the linearly constrained LSCMA, the proposed algorithm provides better robustness against the signal steering vector mismatches, yields higher signal captive performance, improves greater array output SINR, and has a lower computational cost. The simulation results confirm the superiority of the proposed algorithm on beampattern control and output SINR enhancement.

This paper proposes a multi-point DC voltage control strategy of voltage source converter based multi-terminal DC (VSC-MTDC) transmission system for integrating large-scale offshore wind power. Taking a typical four-terminal DC transmission system for example, DC power flow distribution is analyzed, DC flow calculation model is derived and active power control of auxiliary converter station with DC voltage-active power characteristic is proposed. Finally, simulations in PSCAD/EMTDC are conducted to verify the validity of multi-point DC voltage control method under various operating state and MATLAB programming are undertaken to verify the accuracy of DC power flow model. Results show that this method can guarantee the active power allocation of VSC-MTDC transmission system and good control effects are obtained.

A novel robust least squares constant modulus algorithm (LSCMA) is proposed for blind adaptive beamforming, which is based on explicit modeling of uncertainty in the desired signal array. To improve robustness, the weight vector is optimized to involve minimization of cost function, while imposing the oblique projection constraint on the weight vector and maintaining a distortionless response for the worst-case signal steering vector. The proposed algorithm appears to be an appealing technique for blind adaptive beamforming that combines excellent robustness with low computational complexity. The numerical experiments have been carried out to demonstrate the superiority of the proposed algorithm on beampattern control and output SINR enhancement.

Since the crisis of energy and climate intensifies, wind power, one of the most perspective renewable energy, develops rapidly around the worldwide. After the publication and implement of Renewable Energy Law, China wind generation is growing dramatically and Shandong province will be the eighth ten-gigawatt-level wind power base by 2020. In this paper, some characteristics of power grid and wind power development of Shandong province are given, such as features in power grid and power sources, installed capacity of wind power, geographical distribution of wind generation, wind farms and wind turbine generators and off-shore wind power. Next, the problems of wind power operation in this area are proposed in the following aspects: peak regulation and frequency regulation, wind power penetration in regional grid, voltage control in regional network, the stability of power grid and the effect of HVDC system on wind power integration. Then, the reasons for the above problems are analyzed, which can be attributed to several respects: imperfection of technical rules and policies, uncoordinated development with power sources and grid, lack of technical tools for wind power dispatching, poor performance of supervisory control and data acquisition system (SCADA) system in wind farms, poor performance of wind turbine generators. Finally, some suggestions and measures are put forward, which will be a guiding reference for the wind power integrating and operating.

The desired impedance of Thyristor Controlled Series Capacitor (TCSC) is usually obtained by adjusting the firing angle and it is of great importance to make clear the relationship between the two quantities. The relationship between firing angle and conduction angle is proposed in this paper considering the influence of the thyristor conduction characteristics and the equivalent resistance in the reactor branch. In the derivation of the fundamental-frequency impedance, it is found out that there are dual solutions corresponding to the same firing angle in most steady operation area of TCSC. One is inductive and the other is capacitive. This phenomenon is demonstrated by both digital simulation and dynamic emulation experiment. Some conclusions and experiment results can provide reference to engineering exploitation and bottom control design of TCSC.