To ensure the safety of new energy vehicles during the entire period of use, it is necessary to conduct health monitoring for the full life cycle of lithium-ion batteries. Aimed at the low learning rate due to the small capacity of training data set for the remaining useful life (RUL) prediction model based on neural network and the duplicate collinearity of the extreme learning machine(ELM) method, a method for augmenting the training data set is proposed. In addition, based on the improved ELM, an RUL prediction model for the full life cycle of lithium-ion battery is built. First, the early operation data of battery is extracted to formulate health factors, and the Akima interpolation method is used to augment the amount of training data. Then, the salp swarm algorithm is used to improve the ELM network, and the RUL prediction model for the full life cycle of lithium battery is established. Finally, the NASA battery data set is used to validate the model. Experimental results show that the proposed method for augmenting the training data capacity is effective, the capacity tracking capability of the RUL prediction model in full life cycle is strong, and the prediction error is small.

A single-phase transformerless inverter for photovoltaic power generation is proposed, which has a common ground between its input and output and thus eliminates the common-mode current in the photovoltaic system. Meanwhile, its voltage gain is higher than that of the traditional single-phase quasi-Z-source inverter. In addition, the use of thin film capacitor makes the inverter more reliable and prolongs its service life. The working principle of this inverter is also analyzed in detail. Finally, a 140 W prototype was built, and results verified the correctness of the proposed inverter topology and the effectiveness of the control strategy in islanding and grid-connected operation modes.

The magnetic leakage from an indoor air-core reactor leads to problems such as serious nearby electromagnetic pollution and heat generation by metal equipment. To solve these problems, based on the ANSYS finite element simulation platform, the indoor air-core reactor and its surrounding ancillary facilities and building structure of a 500 kV substation are modeled in three dimensions, and the building roof is equipped with a shielding plate. Through the optimization analysis of shielding materials, thickness and gap width, a scheme is formulated to improve the electromagnetic environment surrounding the indoor reactor. Simulation results show that the magnetic induction intensity of the steel structure can be effectively reduced by adding a shielding plate which is overlapped by 3 mm thick aluminum plates above the steel beam. The temperature change of the reactor during its operation meets the insulation heat resistance requirement for the air-core reactor. The edge section temperature of the shielding device is higher, with a peak of 53.26 °C. The average temperature of surrounding buildings and facilities increases by about 5-10 °C, which meets the requirements of safe operation.

The three-port converter studied in this paper includes three ports, i.e., power supply, energy storage and load, in which the load can directly obtain electric energy from the power supply or the energy storage port. First, a mathematical model of Euler-Lagrange form is established, a passivity-based controller is designed, and the simulation of passivity-based control (PBC) is carried out. The PBC strategy has advantages of strong global stability and strong robustness to system parameter deviation and external disturbance in the nonlinear system. Based on the PBC theory, the passivity of the three-port converter system is demonstrated. Through the PBC and single-phase-shift control of dual-active-bridge (DAB), the energy transfer between the three ports is realized. Finally, simulation results in Matlab/Simulink are given, which proves that the load in the device can directly obtain electric energy from the energy storage port and run safely, stably and reliably.

Aimed at the problems of current spikes and voltage fluctuations in the charging process of existing multi-level inverters, a novel quasi-resonant five-level inverter is proposed in this paper. A carrier-stacked pulse width modulation scheme is adopted, and the switched capacitor technology is combined with the traditional five-level inverter, which reduces the accumulated level at the previous stage and realizes the output of five-level voltage. In addition, the capacitor charging process and the series inductance resonate to eliminate current spikes and voltage fluctuations, while reducing the heating problem of the capacitor and prolonging the service life of the circuit. Finally, simulation verification is carried out, and results prove the correctness and feasibility of the scheme for the proposed inverter structure.

Aimed at the problem that the performance of dielectric barrier discharge (DBD) load cannot be fully utilized by the common load resonant-type power supply with continuous waveform and the deficiency that the topologies of existing pulsed power supplies are complicated, a power supply with unipolar forward pulse is proposed in this paper, which consists of one power switch, two diodes and one coupled inductor. Through the analysis of its working modes, it is shown that this power supply can provide a fast-rising pulse voltage for DBD load. In addition, the power switch operates in a soft-switching state. Simulation and experimental results verified the feasibility of the proposed power supply, indicating that it can provide certain reference for the upgrade of the existing power supplies for DBD load.

The two-switch Buck-Boost converter has been widely applied in step-up and step-down scenarios. However, it usually operates under hard switching conditions in the existing various control and modulation modes. In addition, its interleaved control circuit is usually complicated. A three-switch interleaved Buck-Boost circuit with co-directional coupling inductor and its control method are given based on the characteristics of co-directional coupling inductor. First, the coupling process of the coupling inductor during the switching process is analyzed under a large coupling coefficient, based on which the circuit's fundamental operating principle is given in detail. Then, it is concluded that the extended duty cycle and soft switching of Boost-side power switches can be achieved in the discontinuous self-induction current mode, so as to avoid the synchronous and current-sharing circuits in the two-phase interleaved control circuit, thus obviously simplifying the control circuit. Finally, simulation and experimental results verified the analysis results.

In view of the high fluctuation and randomness of wind turbine output, which affects the safe and stable operation of power system as well as the accuracy of wind power prediction, a wind power prediction method based on the fluctuation characteristics of wind power is proposed. First, the fluctuation characteristics of wind power are analyzed in terms of time scale and unit scale, and the appropriate wind power data is selected for wind power prediction. Then, a wind turbine short-term power prediction model based on least squares-support vector machine (LS-SVM) is established. The adaptive variational mode decomposition (AVMD) is used to decompose the wind power data to achieve frequency division, and the improved particle swarm optimization(IPSO) is used to optimize the model parameters affecting the re-gression prediction in the LS-SVM model. Experimental results show that the prediction model has strong adaptability, and the effectiveness of the prediction method can be proved by prediction error evaluation indexes.

As power lithium-ion batteries play a key role in the electric vehicle industry, ensuring their working reliability has become a research hotspot at present. In this paper, the materials and manufacturing processes of lithium-ion batteries are reviewed. The battery state estimation and remaining useful life prediction methods are summarized in detail, and the advantages and disadvantages of these methods are discussed. From the perspective of battery management system, the relevant knowledges of equalization management system and thermal management system are sorted out in turn. From the perspective of electric vehicle hybrid energy storage system, the performance degradation mechanism under actual working conditions and the relevant technologies are elaborated upon. Finally, the status quo of key technologies related to the reliability of power lithium-ion batteries used in electric vehicles is summarized from four aspects, and the development possibilities in the future are forecasted.

Due to the duty cycle constraint on the traditional Boost converter, its applications to high-voltage-gain power supply are limited to certain degree. In this paper, a DC-DC converter with high voltage gain based on an isolated Boost converter and Cockcroft-Walton voltage multiplier cell (VMC) is studied, and its working principle and characteristics are analyzed. This converter achieves a conversion with an ultra-high step-up ratio by integrating the isolated Boost converter with the VMC. Compared with the traditional Boost converter, this topology has a high voltage gain in a low duty cycle, a low voltage stress of active switching device, and a simple control circuit with one single switch. Finally, a 35 W prototype with an efficiency of 89.5% was built to achieve a high step-up conversion from 24 V to 1 000 V, and the theoretical analysis results was verified by experimental results.