A DC series arc fault is harmful and not easy to distinguish, so its detection technology needs to be continuously improved. This research establishes a DC series fault arc generation and experiment platform. Firstly, this research basically analyzes and summarizes the variations of line current and supply output voltage caused by an arc fault. Then, a DC series arc fault detection method, based on comprehensively using line current and supply output voltage signals, is proposed. In order to extract the characteristic frequency band of the line current, the Local mean decomposition(LMD) is employed which has a better decomposition effect. Then, fuzzy entropy and harmonic power of the corresponding frequency-band signals are calculated to reflect the variation of the line current complexity. Moreover, the standard deviation of the supply output voltage is selected as another characteristic for identifying arc faults. Finally, the support vector machines (SVM) is employed to classify the extracted features. Experiment data and simulation results illustrate that the hybrid method not only has a higher recognition rate, but also can avoid misjudgment and invalid operation of the program to a certain extent.

Light Emitting Diode(LED) has the advantages in high efficiency, long lifetime, energy saving and environmental protection. To achieve the high power factor fed by AC power supply, electrolytic capacitors are usually used to buffer the imbalance between input alternating AC power and output constant DC power in a power factor correction(PFC) circuit. However, the electrolytic capacitor has shorter lifetime compared with LED light source. To solve this issue, this paper proposed a novel flyback PFC converter with two outputs, where one directly supplies the LED load, and the other cascades a DC-AC ripple cancellation circuit(RCC). Based on series compensation structure, RCC generates an opposite ripple waveform to cancel the total ripple current, such that the electrolytic capacitor can be saved. The flyback PFC converter in discontinuous current mode(DCM) can realize PFC automatically. RCC uses a full-bridge inverter topology, which has no DC bias and the input power near the zero-crossing point can still support the required voltage to generate the opposite ripple waveform for ripple cancellation. A 17W LED driver prototype has been built in the laboratory. Experimental results are consistent with the theoretical analysis and verify that the proposed LED driver has good performances of electrolytic capacitor-less, wide AC input voltage range, high power factor and high efficiency.

The large space wireless power transfer(WPT) system that receiving energy from the spatial magnetic field is an attractive alternative for low and medium power mobile devices. The bio-electromagnetic safety is the main issue of the large space WPT system. To reduce the intensity of the space magnetic field while meeting the received power demand, a novel design method based on the magnetic field in space is proposed for the large space WPT system. Different with the traditional magnetic coupling design method, the proposed method takes the spatial magnetic field as the design object, and the primary side and secondary side are designed separately. The relationships between the transferred power and efficiency of the receiver under certain spatial magnetic field are analyzed. The maximum transmission power of the receivers is introduced. The primary side is designed to satisfy the safety requirement, and the receiving side is designed to provide the request power and efficiency. Providing a guideline for the parameter design of the receivers. To verify the effectiveness of the proposed method, a 5 W, 6.78 MHz prototype with a 2-m diameter and 0.5-m distance double-circular single-turn coil is designed. The maximum transmission power state is verified by simulation. The simulated results show that by using the proposed method, the receiving side can satisfy the power requirements while the spatial magnetic field decreased.

A three-coil inductive power transfer(IPT) system, which has inherent constant current(CC) to constant voltage (CV) output characteristic, is suitable for automatic battery charging. However, less effort is taken to reduce effect of undesired cross-coupling which can reduce deviation to CV output. To address this issue and can achieve a stable CV output of three-coil IPT system, an approach is provided in this paper. The approach is theoretically analyzed to eliminate the effect of the proposed undesired cross-coupling on the CV output. In addition, it reduces the space occupancy of three-coil coupler as well. An experimental topology is built to verify the suggested design methodology and the analysis. And the result shows that the deviation to CV output is 7.5 V. This difference is small which can be tolerance in the IPT charging system.

Frequency tuning is widely used in wireless power transfer(WPT) systems for output control. In this paper, a design method of series-series(SS) WPT systems employing frequency tuning control is proposed to achieve a constant current(CC) and constant voltage(CV) battery charging profile over a large coupling and load ranges. Particular attentions have been paid to guarantee zero-voltage switching(ZVS) in the whole CC/CV charging process and the whole coupling range. The relationship between frequency splitting(FS) and frequency bifurcation(FB) is theoretically analyzed and the feasible operating zone for frequency tuning is figured out in kilowatt applications with ZVS. Then, secondary winding is optimized for overall efficiency improvement. A 3.1kW WPT system is designed and built for experiments. The measured DC-DC efficiency of the system with a coupling coefficient range of 0.13-0.31 peaks at 96% and it is higher than 90% throughout CC charging process.

This paper presents a high-performance test bench for Mega Watt(MW) level high-speed machine and MW level 10 kV rectifier with 333 Hz fundamental frequency. It is based on AC pump back topology under the limit of 400 kW grid power capacity. In this paper, the overall structure of the test bench is introduced. Key features those enabling high-speed high-power loop test are analyzed in details. First of all, the mechanism of circuit breaker arc reignition and cable derating caused by high frequency are quantitatively analyzed and a guideline for the design and installment practice for these component is formed, which is different from the guideline at low frequency. Next, based on the multi-level real-time control system which realizes the monitoring and control of the large scale test bench, a multi-time scale protection system is designed for complex faults and failure modes. According to a step-by-step decoupling verification strategy, the DUT and the pump back test bench are both successfully built and experimentally validated at their rated operation points.

A residual current protector suitable for electric vehicle charging mode 2 is introduced in this paper, which can detect the sinusoidal AC, pulsating DC, smooth DC and other residual current waveforms generated during electric vehicle charging. The magnetic modulated current transformer in the protector is used to detect the complex residual current, the low pass analog filter is used to demodulate the signal, and the residual current is collected and analyzed by the MCU. Through the test, the protector meets the leakage protection requirements of IEC62752 《In-Cable Control and Protection Device for mode 2 charging of electric road vehicles, IC-CPD》. Furthermore, the protector characterizes a simple structure, small size and low cost.

The high-power spacecraft power system is the developing trend. The distributed spacecraft power system with the advantage of feasibility and scalability fulfills the high power requirement. The reliability of distributed spacecraft power system is crucial. The high reliable architecture with multiple buses of distributed spacecraft power system is proposed in this paper. The reconfiguration strategy and operation mode of the system is designed. Then, the seamless mode transfer is achieved when different faults occur. The reliability of the distributed spacecraft power system is improved. Finally, the effectiveness of control strategy is verified.

The wide bandgap semiconductor material 4H-SiC has high reliability epitaxy, high electron mobility, ultra-high band gap width, large electron saturation drift speed, large critical breakdown field strength and low mobility, Low anisotropy and other excellent characteristics. Power devices based on SiC materials have been widely used in power grids, ships, high-speed rail, electric vehicles and other fields. Among many power electronic devices, SiC MOSFETs have been used in UHV DC transmission, electric vehicles and other fields due to their excellent high-frequency characteristics, high-temperature characteristics, and high-speed switching characteristics. This article takes 30 1200V/20A SiC MOSFETs developed by the Global Energy Interconnection Research Institute Co.Ltd as the research object, and evaluates the changes in the dynamic and static characteristics of SiC MOSFETs through standard deviation, skewness, kurtosis, deviation and coefficient of variation. The specific parameters include on-resistance R DS ( on ) , threshold voltage V GS ( th ) , transconductance gfs , drain-source capacitance C DS , gate-drain capacitance C GD , gate-source capacitance dispersion C GS , rise time t r , fall time t f , turn-on delay t d ( on ) and turn-off delay t d ( off ) .

The modular multilevel DC-DC converter(MMDC) is a promising solution for the interconnection of MVDC distribution systems with LVDC ports. Due to the symmetric structure and operation scheme, the MMDC is normally only capable of operating with monopole MVDC distribution systems. This paper proposes a bipolar operation scheme of the MMDC. Based on the concept of the flux dc-bias cancellation, a center-tapped high-frequency interface transformer is employed on the MV side of the MMDC. A dedicated operation method is proposed, whereby the power flows of the two MVDC poles can be manipulated independently with a simple control scheme. Compared to the conventional MMDC with monopole operation, no additional component is required and no penalty of increased current rating is imposed on the semiconductor devices or the interface transformer. Moreover, a single-pole operation is also possible with the proposed operation scheme. If the valves of one pole are faulty, it can be isolated from the main converter for maintenance while the MMDC can continue operation without interruption and deliver at least 50% of the rated power capacity. Hence, the reliability and availability of the power delivery can be significantly enhanced. The validity of the proposed bipolar operation scheme of the MMDC has been verified by both simulations and experiments with a down-scale prototype.