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As a natural result of the electrified integration and electrical energy revolution, the electromagnetic launch (EML) technology will be inevitably used for future launch missions. This paper has summarized research focuses in this field according to the published papers on EML in China during the past decade and mainly introduced the current research and progress in several key technologies, including launcher, integrated launch package, high-power high-density supply, and overall control/maintenance. Some common pressing problems are pointed out to provide direction for the application of EML technology in engineering and many other fields, such as launcher life, miniaturization of power supply, and improvement of energy availability. [ABSTRACT FROM AUTHOR]

The development of new technologies in power generation and application, together with the demand for the reliability and capability of power supply has drawn increasing attention to dc distribution and microgrid technology. This paper introduces the renovation project for a single-circuit XLPE cable line being converted into dc operation after its second failure under 35 kV ac. This is the first time ever in China for this type of system conversion, in which the existing XLPE cable line was put into operation in a bipolar voltage-source converter (VSC) dc system of 10 kV voltage and 150 A current to maintain its 3 MW capacity. The test methods for cable performance that were checked under the designed dc scheme were put forward and conducted on sectioned cable samples. After the cable test and equipment installation, the line was put into operation under the VSC dc topology in 2011. It has now been running for four years without any interruption. Compared with other alternatives for ac operation, this proposal shows advantages in aspects of economy, reliability and engineering. Besides, the theoretical evaluation suggests that the system capacity can be further increased by four times, and the first step is underway for that goal. [ABSTRACT FROM PUBLISHER]

The 100 T pulsed magnetic field project is under development at the Wuhan National High Magnetic Field Center, Wuhan, China. Using the NI CompactRIO hardware and Lab-VIEW software platforms, a control and data acquisition system (CADAS) for the 100 T pulsed high magnetic field facility is designed and implemented. This paper briefly introduces the design of the control system and presents the aspects of the implementation. The CADAS developed in this paper communicates with three types of power supply systems and controls their discharge coordinately, and records discharge waveforms. It has been put into test, and 67.6 T pulsed magnetic field has been generated by a test three-coil magnet. [ABSTRACT FROM AUTHOR]

A quasi-continuous high magnetic field is a special kind of pulsed magnetic field with a flat-top field longer than 100 ms. This paper proposes a hybrid power supply that consists of a capacitor power supply and a generator-rectifier power supply. A dual-coil magnet is powered to generate a 65 T/100 ms quasicontinuous high magnetic field with a ripple less than 500 ppm at the Wuhan National High Magnetic Field Center, Wuhan, China. A protection circuit consists of an R-C branch and a diode array is discussed for the worst short-circuit fault, which occurs between the first turns of inner coil and outer coil. This type of faultwill produce oscillation voltage with a high peak value and high frequency on the rectifiers. A self-adaptive PI controller with the coefficients corrected by a back propagation neural network is adopted to reduce the ripple of a flat-top. [ABSTRACT FROM AUTHOR]

With the increasing development of AC/DC hybrid power systems, local synchronous generators in receiving-end grids are being replaced by high-voltage direct current (HVDC) power. The risk of short-term voltage instability exists because of the decline in dynamic reactive power resources from generators, the presence of high-proportioned induction motors and the demand for vast reactive power of HVDC under AC faults. In this situation, unit commitment (UC) should take short-term voltage stability into account. Hence, crucial generators can be retained to provide sufficient dynamic reactive power. This paper proposes a UC model incorporating short-term voltage stability constraints (SVSCUC). Furthermore, a decomposition-based solution approach is presented, which involves an alternate iterative solving of UC and differential-algebraic equations (DAEs). Time-domain simulation (TDS) is utilized to quantify the stability with an indicator. Linear stable cuts are formulated through trajectory sensitivity analysis and added into the UC. The UC is decomposed into a master problem based on mixed-integer linear programming (MILP) and subproblems. The SVSCUC is illustrated using benchmark systems and a real system in eastern China. The results show the effectiveness and efficiency of the proposed methods. Violations of short-term voltage stability for credible contingencies are eliminated under the commitment of SVSCUC. [ABSTRACT FROM AUTHOR]

A higher magnetic field can provide more opportunities to reveal new phenomena in a scientific research. Aiming to achieve a higher magnetic field, Wuhan National High Magnetic Field Center (WHMFC), Wuhan, China has designed a a power supply system for 100 T magnetic field under existing power supply conditions in April 2015. The 100 T magnet consisting of three coils is energized by a multipower supply system. The outer coil is energized by a pulsed generator-rectifier connected to battery bank in series. The middle coil and the inner coil are energized by two capacitor bank, respectively. To ensure safety and reliable operation, control sequence as well as protection system for the power system is designed and developed. A test system including the prototype of three-coil magnet is established at WHMFC. A series of tests are carried out on hybrid power supply systems. 73.3 T peak field has been achieved as the highest magnetic field in the test. The test results presented in this paper show the hybrid power supply system is feasible and operable. [ABSTRACT FROM AUTHOR]

Ice melting with dc is one of the key technologies to prevent the Chinese power grid from ice storms. Especially after the severe ice storm in the southern part of China in early 2008, dc ice-melting technology has drawn more attention than ever before. However, there are few satisfactory methods to select correct parameters so the ice-melting project rarely achieves desired effects in some cases when applied in Hunan, Guizhou, and other provinces in China. Therefore, it is of great significance to develop a method to estimate parameters which is applicable in the practical situation for dc ice melting. To handle this, the factors, such as wind velocity, ambient temperature, current density and ice-layer thickness were analyzed and then a dc ice-melting model is put forward in this paper. Both the results of simulations and experiments show that the ice-melting process can be divided into three stages composed of temperature rising, ice melting, and ice shedding, among which the ice melting is the key stage consuming most of the ice-melting time. In this stage, an elliptic airgap is formed and widened gradually with an influence on the ice-melting time and the temperature of the conductor. The experiments in the artificial climate chamber demonstrate that the results of the presented model are consistent with those of the experiments generally, so it can be employed to estimate the parameters of ice melting in practical engineering as reference. [ABSTRACT FROM AUTHOR]

The breakage of overhead covered conductors on distribution lines resulting from the short-circuit arcs caused by lightning flash becomes a challenge as the application of covered conductors increases on distribution lines. Based on various methodologies and devices developed to avoid the covered conductor breakage in the world, novel arc-guided devices, including arcing protection hardware with barbs, clamping post composite insulator, and barb electrode clamping post porcelain/composite insulator are presented in this paper. Experimental results are also presented to validate these new developed devices. Devices based on the developed technologies have been widely applied on the power grids in China successfully. [ABSTRACT FROM AUTHOR]

Failure probability of system components may vary with the changes of weather, environment and other operation conditions. The time-varying or condition-based failure probability can be represented using a fuzzy model. Based on credibility theory, this paper presents a novel operation risk assessment method to handle the two-fold uncertainty combining randomness and fuzziness in power system operations. In the proposed method, a random fuzzy model is developed to accommodate impacts due to various operation conditions and other factors on the failure probability of system components. The WECC nine-bus system, IEEE 14-bus system and an actual power system in Northeast China were used to demonstrate feasibility and applicability of the presented method. The operation risk assessment module using the proposed method has been embedded in the EMS system in a district control center of a power company to perform real-time operation risk assessment. [ABSTRACT FROM AUTHOR]

The power industry in China has grown significantly over the past decade, spurring the adoption of system-wide automatic voltage control (AVC) technology to meet stricter requirements for security and economical power system operation. To cope with the rapidly developing and frequently changing Chinese power grid, an AVC scheme based on adaptive zone division is introduced in this paper. Logically, this type of system has a three-level hierarchical structure, but, here, both secondary voltage control (SVC) and tertiary voltage control (TVC) are implemented via software at the same control center. The control zones are no longer fixed but are reconfigured online and updated in accordance with variations in the grid structure. The technical details of these procedures are presented here. The implementation of TVC (which is based on an online reactive optimal power flow) and SVC are also discussed, together with some technical details on improvements to their reliability and robustness. Some results obtained from field-site applications based on similar-days testing rather than simulations are employed to evaluate the performance and improvements of the AVC system. This system has been installed at over 20 control centers in China. [ABSTRACT FROM PUBLISHER]

The byproduct gas in steel industry is one of the most significant energy resources of an enterprise. Due to the large quantity of yield, fluctuation, and various categories of users encountered in a blast furnace gas (BFG) system, it is very difficult to accurately predict the amount of gas to be generated and forecast the users' consumption demand. In this paper, a two-stage online prediction method based on an improved echo state network (ESN) is proposed to realize forecasting in the BFG system. In this method, one completes the prediction realized at the levels of BFG generation and consumption using a class of ESN with input compensation and parameter optimization. At the second stage, to predict gas holder level of the BFG system, the energy flows being predicted at the first stage are denoised, and their correlation with the holder level are determined by using a concept of grey correlation with time delay. Then the effect factors exhibiting high correlation levels are extracted to construct the model of the gas holder. The prediction system designed in this manner is applied in the Energy Center of Baosteel Co., Ltd, China. The results demonstrate that the prediction system exhibits high accuracy and can provide an effective guidance for balancing and scheduling of the byproduct energy. [ABSTRACT FROM PUBLISHER]

Jinsha River has very abundant hydro power reservation, ranking first in all the hydro power bases of China. To deliver the 38-GW hydro power from Jinsha power stations by HVDC transmission lines to load centers 1000-2000 km away, it is necessary to determine the right voltage level and the capacity of each bipole. This paper proposes three preliminary power delivery scheme and presents an optimization method for transmission capacity, dc voltage and conductor size. Based on a comprehensive comparison of cost-effectiveness, technical feasibility and network security and stability, it was recommended that the 3 bipolar ±800-kV ultra HVDC (UHVDC) links with rated capacity of 6.4 GW for each link be adopted as transmission scheme of Phase I Hydro Power station on Jinsha River. [ABSTRACT FROM AUTHOR]

A pulsed high magnetic field laboratory has been funded to be established at the Huazhong University of Science and Technology (HUST), Wuhan, China by the National Development and Reform Committee. The facility is planned to be open for external users in 2011 with the implementation of various experimental techniques in pulsed magnetic fields up to 80 T. Pulse durations are in the range from 15 to 1000 ms with the magnet bore sizes from 12 to 34 mm. The pulsed power supplies are a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. The design and analysis of the power supplies and the magnets of short and long pulse durations and the multi-stage pulsed magnets with controllable waveforms are presented in this paper. [ABSTRACT FROM AUTHOR]

China's first HTS power cable project was started in the second half of 2002 and on site system installation was finished at Puji Substation of China Southern Power Grid in March, 2004. This cable system consists of three 33.5 m, 35 kV/2 kArms cables, six terminations, and a dosed cycle liquid nitrogen cooling station. The conductors of the cables were made of 4 layers of BSCCO 2223 HTS tapes. Off grid field testing and live grid trial operation has been carded out since the completion of the installation. In this paper, we will report the key technical parameters of the system. Descriptions of the installation site, demonstration of the system installation, and results of testing and trial operation will also be presented and discussed. [ABSTRACT FROM AUTHOR]

Long-term electricity consumption forecasting has been a hot issue due to its importance in power systems planning. Recently, system dynamics (SD) have been considered a potential method for electricity consumption forecasting. However, traditional SD methods are failed in forecasting future power systems toward low-carbon, due to the complex influencing factors and the simple SD model structure. In this study, a novel method combining SD and the ImPACT equation is proposed to solve the above problem. First, a new influencing factor system including emerging factors is established to consider the development of future power system. Subsequently, the ImPACT equation is employed to decompose the electricity consumption into four subsystems. By doing this, the linkage between factors and electricity consumption can be better revealed, which helps to improve the forecasting accuracy. Next, models for quantifying the correlation between subsystems and factors are established using SD. Finally, the proposed method is verified by forecasting the power consumption of China in the future year 2030 to 2050. Furthermore, various scenarios are set to analyze the changing trend of future power consumption by different influencing factors. The results of this article can provide important basic information for power supply and power grid planning. [ABSTRACT FROM AUTHOR]

Electricity theft behaviors have caused great harm to the economic benefits of power companies and the secure operation of power systems, thus electricity theft detection is paid much attention in the actual power supply management. In this work, a two-step electricity theft detection strategy is proposed to identify electricity theft users and predict potentially stolen electricity (PSE) for maximizing economic return. In the first step, a neural network model called convolutional autoencoder (CAE) is proposed for electricity theft identification, and the convolutional layer is adopted in CAE to extract and identify the abnormalities of electricity theft users against the uniformity and periodicity of normal power consumption features. In the second step, the PSE of each identified electricity theft user is predicted by the improved regression algorithm named Tr-XGBoost, which combines the extreme gradient boosting (XGBoost) algorithm and transfer adaptive boosting (TrAdaBoost) training strategy. The propsoed Tr-XGBoost could learn the relationship between the extracted electricity features and the PSE of each electricity theft user, and then the predicted PSE can be used to determine the list of electricity theft users to be inspected for maximizing economic return. Case studies on both the IEEE 33-bus test system and a low-voltage distribution system of a province in China show that the proposed two-step electricity theft detection strategy can improve the accuracy of electricity theft identification, and obtain a larger economic return because of a more accurate result of PSE prediction than other state-of-the-art algorithms. [ABSTRACT FROM AUTHOR]

Catenary-free trams powered by on-board supercapacitor systems require high charging power from tram stations along the line. Since a shared electric grid is suffering from power superimposition when several trams charge at the same time, we propose to install stationary energy storage systems (SESSs) for power supply network to downsize charging equipment and reduce operational cost of the electric grid. To evaluate the trade-off between component cost and operational cost, an optimisation problem, which integrates type selection, sizing, energy management and different installation configurations of the SESSs, is introduced and formulated in terms of an annual cost. Disciplined convex modelling is applied to obtain a computationally tractable solution for a case study on an existing line in China. Results show that the optimal solution may reduce tramline cost by 11.48%. [ABSTRACT FROM AUTHOR]