To better compensate for the voltage drop of DC-side bus in an electric vehicle (EV) fast charging station and limit the power ramp rate of power grid, a nonlinear control strategy of flywheel energy storage system for the DC fast charging station is proposed based on the immersion and invariance theory. First, considering the power balance relationship of the power supply system in the fast charging station, the impact characteristics caused by the charging load instantaneous access under the traditional control strategy of flywheel energy storage system are analyzed, and the voltage stability of DC-side bus is determined as the optimization objective. Then, the effect of bus voltage control and the control accuracy of energy storage output current are considered, an affine nonlinear model of flywheel energy storage is established, the manifold surface and control law are constructed using the immersion and invariance method to provide the capability to quickly respond to the charging load current mutation and flywheel speed change, and a charging and discharging control strategy for the energy storage system is designed. Finally, a simulation model is built to compare and analyze different control strategies under single-and multi-EV access, and results show that the proposed control strategy can effectively suppress the influence of electric vehicle access and flywheel speed change on the bus voltage, thereby alleviating the impact on the distribution network.

The cascaded H-bridge is considered as one of the most suitable topologies for photovoltaic (PV) power generation. Aimed at the problems of the traditional three-phase cascaded H-bridge PV inverter such as a large capacitor volume, a short service life, inter-phase power mismatch and a complex control communication system, a novel modular three-phase PV inverter and its distributed control strategy are proposed based on the principle of magnetic flux cancellation. First, the basic structure of the proposed modular topology is introduced. Then, the basic principle of magnetic flux cancellation power decoupling and the influencing factors of double-line frequency voltage ripple are analyzed in detail, and a distributed control strategy is proposed to suppress the double-line frequency voltage ripple and ensure the balance of three-phase output power. Finally, the correctness of theoretical analysis and the feasibility of the proposed control strategy were verified by simulation and experimental results.

A novel nine-level inverter topology with double boost and reduced components is proposed by combining the voltage boost capacity of switched capacitors with the voltage halving characteristics of a coupling inductor. This inverter consists of 12 switches, 2 switched capacitors and 1 reverse polarity coupling inductor. The charging and discharging of each capacitor in the inverter can maintain a self-balance, so the additional balance circuit is not needed. Compared with the topologies of most of the existing nine-level inverters that are based on switched capacitors, the proposed topology has a smaller capacity of switched capacitor. The output voltage levels are greatly increased by the adoption of the reverse polarity coupling inductor, and the current stresses on some switches are reduced by half, which can further reduce the switching loss. The working modes, modulation strategy, design of switched capacitors and loss analysis of the proposed topology are discussed in detail. In addition, the proposed topology is compared with those of other nine-level inverters, and its advantages are introduced. Finally, simulation and experimental results verified the effectiveness of the proposed topology.

Aimed at the problem that the particle swarm optimization (PSO) algorithm has a poor global search capability and is easy to fall into local optimum when it is applied to the selective harmonic elimination pulse width modulation (SHEPWM) of an inverter, an improved PSO algorithm is proposed. The vertical crossover operation of genetic algorithm is introduced to the search process, and the elite retention strategy is used to improve the global and local search capabilities of the algorithm and retain excellent individuals, thereby increasing the accuracy of switching angle and improving the performance of SHEPWM. This algorithm is used to solve the SHEPWM nonlinear transcendental equation of a novel asymmetric cascaded switched capacitor multi-level inverter, which overcomes problems such as the high dependence of traditional numerical methods on initial value and the low accuracy of the traditional PSO algorithm in solving the switching angle. Finally, the feasibility of the proposed topology and the effectiveness of the proposed algorithm applied to SHEPWM were verified by simulation and experimental results.

To study the influence of electron irradiation on the reliability of silicon carbide metal-oxide-semiconductor field-effect transistor(SiC MOSFET) with different aging degrees of the gate oxide, the electrical characteristics of SiC MOSFET were analyzed by combining high-temperature gate bias and electron irradiation experiments. The influence of electron irradiation on the threshold voltage of SiC MOSFET after the gate oxide was stressed by high temperature and a strong electric field was discussed. To avoid the impact of the packaging material on the threshold voltage under high temperature and electron irradiation, the device under test was exposed to air during the experiment. Experimental results show that the threshold voltage after the high-temperature positive gate bias experiment was more sensitive to electron irradiation. The exponential relationship of the influence of electron irradiation on the threshold voltage of SiC MOSFET after the high-temperature gate bias aging was proposed. The threshold voltage after the high-temperature gate bias at 39 V and 150 °C for 2 h can be restored to the initial value by 0.2 MeV and 300 kGy electron irradiation. A basic numerical model of SiC MOSFET was established in the Sentaurus TCAD simulator. By setting the electron concentration and hole traps in the oxide, the effect of high-temperature gate bias and electron irradiation on the threshold voltage of the device was simulated, and the threshold voltage recovery mechanism was discussed.

The active-clamped soft-switching inverter can realize the soft-switching of power devices, which is conducive to improving the power density and dynamic performance of the inverter. However, when overcurrent occurs, if the conventional cycle-by-cycle(CBC) current limit strategy( i.e., a strategy under which power devices will be blocked once overcurrent occurs) is adopted, the DC bus current will change its direction from flowing to the inverter bridge to flowing to the DC side. Due to the existence of a resonant inductor, both the DC bus current and the current flowing through the resonant inductor flow through the auxiliary switch, so there is high current stress on the auxiliary switch. In this paper, an improved CBC current limit strategy is proposed. By changing the switching state of the inverter bridge after the CBC current limit strategy is triggered, the DC bus current flowing to the DC side is reduced, thus significantly suppressing the current stress. In addition, the protection strategy was verified by an experiment of 3 kW active-clamped soft-switching inverter.

The three-phase inverter is an important part of the motor drive system in an electric vehicle (EV). When a fault occurs, the fault sample size will be limited due to the short occurrence time, resulting in sample imbalance. To solve this problem, an inverter fault diagnosis method combining conditional generative adversarial network (CGAN) and convolutional neural network (CNN) is proposed in this paper. First, the phase current is taken as a fault sensitive signal, its frequency-domain characteristics are obtained by fast Fourier transform, and normalized preprocessing is carried out. Then, each sample is labeled and input into the CGAN model for countermeasure training to generate new samples in each fault mode. Finally, the CNN model is used to distinguish various fault modes of inverter. Through experimental research, it is found that the fault diagnosis accuracy based on CGAN-CNN can reach more than 98%, indicating that the proposed sample generation method is better than the traditional Smote and GAN methods. The results in this paper provide theoretical support for the intelligent operation and maintenance of new energy EVs.

Since there is only one working mode of continuous wave or pulse after the design of a traditional spaceborne travelling wave tube(TWT) amplifier is finished and the output power at the saturated working point is fixed, a novel design scheme for space TWT power supply is proposed, which is compatible with multiple working modes including continuous wave and pulse. The TWT power supply and multi-mode TWT designed through this scheme are integrated into a multi-mode TWT amplifier, which have functions of continuous wave mode, low repetition rate pulse mode, high repetition rate pulse mode and adjustable on-orbit power. As a result, it can be applied to communication, navigation, data transmission and remote sensing observation satellites, thus making the on-orbit reconfigurable load possible. Through a simulation test, it is found that the power efficiency of the multi-mode space TWT reaches 94%, the repetition frequency range covers the continuous wave up to 10 kHz, and the adjustable output power ranges between 47 and 53 dBm.

The electromagnetic radiation emitted by an AC/DC telecommunication power supply is prone to exceeding the limit standards, so the researches on its electromagnetic radiation mechanism and prediction methods can improve the corresponding electromagnetic compatibility (EMC) design. First, after the analysis of the source and propagation path of common-mode(CM) electromagnetic interference in an AC/DC telecommunication power supply module, it is suggested that its far-field electromagnetic radiation can be decomposed into two types, which are driven by input-port and output-port CM voltages, respectively. Then, a novel method of far-field electromagnetic radiation prediction is proposed by combining the CM voltage-driven sources with the radiation transfer functions of parasitic radiators. The spectrum measurement of each CM voltage-driven source is realized by designing a spectrum analyzer and a resistor attenuator, and the radiation transfer functions of each parasitic radiator is numerically calculated using an electromagnetic simulation software FEKO. Finally, the radiation prediction of a 4 kW AC/DC telecommunication power supply module was achieved, and the effectiveness of the proposed prediction method was verified by test results.

Aimed at new energy combined power supply systems such as photovoltaic and fuel cells, a non-isolated dual-input high step-up DC-DC converter is proposed. This converter is based on a dual-input Boost circuit, and the two input sources and output, as well as each switch tube, share a common ground. A diode capacitor network is introduced at the later stage to achieve high voltage gain and reduce the voltage stress of switching devices. The two input sources can supply power at the same time, and any one of them can supply power independently without adding extra switch tubes. In addition, the voltage gain can be further improved by expanding the booster unit to adapt to different application scenarios. The working principle for the converter and its extended circuit and the corresponding performance such as voltage gain characteristics and voltage stress of switching devices in three power supply modes are analyzed in detail, and its performance is compared with those of the existing similar converters. Finally, an experimental prototype was built to verify its feasibility.