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This letter focuses on the power module (PM) capacitor voltage balancing of a $\pm 350$ -kV/1000-MW modular multilevel converter (MMC). For this MMC, the current flowing through the IGBTs will exceed the nominal current of the adopted commercial high-voltage (3.3 kV or higher) IGBT products, i.e., 1500 A. As for the PM voltage balancing of this MMC, the switching frequency must be kept low to reduce the losses and the accurate calculation of the PM switching frequency is of great importance to the design of the cooling system. This letter presented a low-switching frequency PM balancing method by introducing the balancing adjusting number (BAN). The PM switching frequency calculation method is also presented with different BANs. Computer simulation and the real-time control hardware in the loop test results based on RT-LAB show the effectiveness of the proposed PM balancing method and the accuracy of the switching frequency calculation method under the rated power.

Pulsed power research for military and civil applications has been conducted at the China Academy of Engineering Physics (CAEP) for more than 50 years. The pulsed power research activities include development of pulsed power components, such as different kinds of high-voltage switches, series of pulsed power sources and pulsed X-ray machines, high-current accelerators for $Z$ -pinch and flash X-ray radiography, as well as medical application and electromagnetic launch. The most recent progress of pulsed power research at CAEP will be presented.

Real-time simulation of modular multilevel converter (MMC)-based HVDC is one of the most important and difficult technologies in the area of power electronics research. This paper presents a methodology for the hardware in loop (HIL) CPU/FPGA-based real-time simulation of a one-terminal MMC HVDC of up to 468 levels using a detailed equivalent model, and the simulation system is based on full-scale physical control system, including actual sub module control boards. The testing subject control system and the accompanying one are based on same hardware and symmetric structure, without expensive third part HIL simulation system, such as RT-lab or RTDS. Small time-step sub module transient simulation in device level with FPGA based parallel computing is discussed in this paper.

Because the numerous nonlinear components and fiber interfaces are used in Module Multiple Converter (MMC), the HIL test of MMC with detailed EMT model and the full-scale interface is hard to be implemented. In recent years, this existing disadvantage caused the MMC controller hardware and software difference between the HIL test and real project. In this paper, a detailed EMT model of hybrid MMC fitting for full-scale interface HIL test is proposed, and the equivalent arm circuit of hybrid MMC and the nonlinear feature of the sub-module are introduced. Then the full-scale interface HIL test system is built to test the performance of proposed model under various conditions. Comparing with the reference model built in MATLAB with detailed semiconductor model, the accuracy of the proposed method can meet the requirement of HIL tests, the current difference of two methods is less than 0.73% and the capacitor voltage difference is less than 0.39%. Due to the full-interface structure, the proposed method can simulate the divergence of capacitor voltage and all faults of the submodule. The MMC controller tested by the proposed method can be directly used in the real project without hardware and software modification.

The industrial x-ray diode with high impedance configuration is usually adopted to generate repetitive x-ray, but its performance would be worsened due to lower electric field on the cathode of diode when a voltage of several hundreds of kV is applied. To improve its performance, a novel metal-ceramic cathode is proposed in this paper. Key factors (width, relative permittivity of ceramic, and so on) affecting electric field distribution on triple points are analyzed by electrostatic field calculation program, so as to optimize the design of this novel cathode. Experiments are done to study the characteristics including emission current of cathode, diode voltage duration, diode mean dynamic impedance, and diode impedance drop velocity within diode power duration. The results show that metal-ceramic cathode could improve diode performance by enhancing emission current and stabling impedance; the impedance drop velocity of diode with spoke-shaped metal-ceramic cathode was reduced to -5 Ω ns(-1) within diode power duration, comparing to -15 Ω ns(-1) with metal foil cathode.

High power AC drives application has lower switching frequency due to the high switching loss of power devices, and many optimized pulse width modulation (PWM)strategies are proposed for the low carrier-frequency ration applications. In some variable frequency application, different PWM strategies are applied in different frequency range for better performance on harmonic current elimination or other optimal characteristics over the full speed range. The smooth shifting of hybrid PWM is a key issue for steady processing of the system. This paper works on the fundamental and harmonic component's transient state of the different PWM strategies during modulation strategies shifting, and propose a compensation algorithm using reference wave phase angle delay compensation and shifting timing selection to reduce the switching impact, and gives the simulation and experiment result under two level voltage source inverter.

A compact, low-jitter, and high repetitive rate all-solid-state flash x-ray generator making use of photo conductive semiconductor switches was developed recently for the diagnostic purpose of some hydrokinetical experiments. The generator consisted of twelve stages of Blumlein pulse forming networks, and an industrial cold cathode diode was used to generate intense x-ray radiations with photon energy up to 220 keV. Test experiments showed that the generator could produce >1 kA electron beam currents and x-ray pulses with ∼40 ns duration under 100 Hz repetitive rates at least (limited by the triggering laser on hand), also found was that the delay time of the cathode explosive emission is crucial to the energy transfer efficiency of the whole system. In addition, factors affecting the diode impedance, how the switching synchronization and diode impedance determining the allowable operation voltage were discussed.

Three-dimensional finite element model of a drum brake is built in this paper. According to test conditions of brake heat fade and other relevant national standards, using ANSYS Workbench, brake drum thermal field is simulated and studied. Through several simulation methods revised about initial conditions, to achieve fitting of the simulation curve and test curve. The boundary conditions for temperature field analysis and simulation methods of the brake drum are confirmed, and the effects of the process of braking speed, braking frequency and braking force etc. to brake drum thermal field are studied. To provide an important reference for the thermal performance analysis of brake at design stage.

Human resources is to develop the productive forces of the core resources during the new era. With the development of Chinese sports career, scientific research plays an important role in the development of sports. The level of the value of human resources has become an important criterion of to judge the competitiveness of sports career. In this paper, we give comprehensive evaluation model of sports science and technology human resources management by building a multi-factor multi-level fuzzy evaluation model, on a basis of pointing out the defect of the traditional econometric model of human resource value, and finally table a instructional proposal on it

In this paper, a three-dimensional (3D) FE model of the healthy human axis was built considered cortical and cancellous bone. The model was validated using numerical results obtained by other authors. The stress distribution and potential fracture patterns of the anterior odontoid were analyzed under different loading direction within coronal plane and sagittal plane. The direction of loading is the main factor resulting in odontoid fracture. The results of FE analysis would be referenced by surgeon.

WebGIS is the application of Web technology to GIS (Geographic Information System). We examine the basic mechanism of implementing a WebGIS. Solutions to some key technical problems are discussed, such as simultaneous multi-user access, improvement in the access speed, and ActiveX DLL.

We investigate the sensitivity and figure of merit (FOM) of a localized surface plasmon (LSP) sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon sensor is 317 nm/RIU, and the FOM is predicted to be above 8, which is very high for a localized surface plasmon sensor. By employing the rigorous coupled-wave analysis (RCWA) method, we analyze the distribution of the magnetic field and find that the sensing property of our proposed system is attributed to the interactions between the localized surface plasmon around the gold nanostrips and the surface plasmon polarition on the surface of the gold planar metallic film. These findings are important for developing high FOM localized surface plasmon sensors.

Utilizing the LCA matrix, we preliminarily analyzed whether wheat-maize rotation system was a carbon sink or a source based on long-term and large-scale straw return in Huantai county. The results indicated that the mode was a carbon source if we comprehensively considered agricultural materials production subsystem and farming subsystem together, with the quantity of net GHGs being -1075.71kgCO2e when producing 1 ton of wheat and maize. But if only farming system was considered, the averaged quantity of cropland carbon sequestration was +262.31 kgCO2e, which could offset the -222.99 kgCO2e carbon emission caused by fertilizes and agricultural machine. Therefore, through straw return and tillage system improvement, farming system might become the carbon sink in the future.