The parameter identification method for the equivalent circuit model of lithium-ion battery has a great impact on the model accuracy. To solve the problems of low convergence accuracy and slow convergence speed in a satin bowerbird optimization(SBO) algorithm, an improved satin bowerbird optimization (ISBO) algorithm is proposed. The inertial weights, Cauchy mutation, Gaussian mutation and greedy selection strategies are used to improve the convergence accuracy of the ISBO algorithm, and its convergence performance is verified by standard test functions. Based on the battery charging and discharging data, the proposed ISBO algorithm is applied to the parameter identification of the equivalent circuit model of lithium-ion battery. Experimental results show that compared with the SBO and adaptive weight particle swarm optimization algorithms, the ISBO algorithm has a higher accuracy when it is used in identifying the model parameters and the identification accuracy is not affected by the working conditions of battery.

As the number of charge and discharge cycles of a lithium-ion battery increases, its state-of-health (SOH) will degrade to some degree accordingly. Aimed at this problem, a method for estimating the SOH of lithium-ion battery based on an improved multi-objective Cuckoo search (IMOCS)-BP neural network is designed, which adaptively changes the update probability and search step size of the Cuckoo search (CS) algorithm while avoiding the algorithm from falling into the local optimum, thereby solving the problems of slow convergence speed and low solution accuracy in the CS algorithm. The IMOCS algorithm is combined with BP neural network to conduct a global search in the node space, reduce the influence of initial values of weight and threshold on BP neural network, and realize the parameter optimization. Through Matlab simulations, it is verified that the SOH estimation algorithm based on IMOCS-BP neural network has a low error and a strong performance, thus realizing an accurate SOH prediction of lithium-ion battery.

Aimed at the problems of fast loss and high capacity configuration of battery energy storage equipment in microgrid, an optimal configuration model of battery energy storage capacity of microgrid considering life loss is established in this paper. In addition, a cost calculation method for the battery energy storage life loss based on fixed daily cycle times is also proposed. This method combines the piecewise linearization idea and the scenario analysis method, and it can effectively extend the lifetime by optimizing the discharging depth and daily cycle times of battery energy storage. Moreover, considering the uncertainties in wind power output and load power, a two-stage robust optimization model is introduced, which is further solved by the column-and-constraint generation algorithm. Finally, the effectiveness of the novel model under different uncertainties and different unit prices of battery energy storage is verified by numerical examples.

Aimed at the problem that the influencing mechanism of configuration size of a differential pressure channel in proton exchange membrane fuel cell(PEMFC) for the cell's electrochemical performance is unclear, the influences of channel height and rib width on the oxygen concentration, water concentration distribution characteristics, current density, power density, and pressure drop of a differential pressure channel and a straight channel are studied, and a comparative analysis of the two kinds of channels is performed. Results show that channel height has little effect on both channels, but the differential pressure channel has an obvious advantage when its rib width is 1.25 mm or 1.5 mm. The influence of pressure converter area on the performance of the differential pressure channel is further studied, and results show that its peak power density is the highest when the height and length of the pressure converter area are 0.05 mm and 1.5 mm, respectively. With the comprehensive consideration of influences on power density and pressure drop, the differential pressure channel with a height of 0.4 mm, width of 1.25 mm, rib width of 1.25 mm, and a pressure converter area with a length of 1.5 mm and height of 0.05 mm is selected. In this case, its peak power density is 0.366 1 W/cm², which is 6.3% higher than that of the straight channel.

The insulated-gate bipolar transistors (IGBTs) have been widely applied in the modern power electronics technology, and the paralleling of IGBTs has become an economical and feasible method in some working scenarios where one single device cannot meet the design requirements. The paralleling of IGBT modules can simplify the circuit structure, increase the converter output power, and improve the power density of devices. During the operation of IGBTs in parallel, the current imbalance, which may be caused by the difference in IGBTs' characteristics in a static or dynamic mode, the inconsistency of junction temperature, the asymmetry of a drive circuit or power loop, as well as the aging or failure of IGBTs due to long-term use, will affect the system's reliability and stability. The research hotspots of parallel-operating IGBTs at home and abroad are investigated. The principle and influence of static and dynamic current imbalance are summarized, and the difference in the current-sharing control principles is analyzed. The performance characteristics of current-sharing control are summarized and compared from the aspects of power loop current-sharing control and drive circuit current-sharing control. Furthermore, the development of current-sharing technologies for parallel-operating IGBTs in the future is also prospected.

The phenomenon of dynamic avalanche occurring during the IGBT turn-off process is one of the important reasons for its failure. To study the dynamic avalanche failure mechanism of IGBT, the Silvaco software was used to simulate and analyze this mechanism. Through the simulation and analysis of the breakdown mechanism, current density distribution and temperature distribution of dynamic avalanche, it is concluded that dynamic avalanche can generate moving current filaments and dead filaments which are either moving slowly or fixed. However, the failure of the device is caused by the dead filaments formed by dynamic avalanche. The dead filaments will lead to a sharp increase of local temperature in the IGBT, and the IGBT will eventually fail because the local temperature is too high to burn the device. On this basis, the causes of dead filaments are analyzed, and specific measures to prevent the dynamic avalanche failure of IGBT are also put forward.

The development of power modules towards high temperature, high power and high density raises higher requirements for the packaging structures of modules. Compared with the traditional wire-bond structure, the double-sided structure has attracted more and more attention owing to its characteristics such as high heat dissipation capacity and low parasitic inductance. However, the mismatch of thermal expansion coefficient between materials used in the double-sided structure makes the structure suffer tremendous thermo-mechanical stress, thus reducing the reliability of power module. Therefore, to develop double-sided bi-directional modules with low thermo-mechanical stress, the effects of chip layouts on the heat dissipation performance of modules and the parasitic inductance were analyzed by simulations at first. Then, a flexible buffering spacer with low Young's modulus is proposed accordingly. The feasibility of reducing the thermo-mechanical stress and improving the reliability of the module was preliminarily proved by simulation and experimental results.

Silicon carbide (SiC) is a promising wide-bandgap semiconductor material owing to its excellent electrical and thermal characteristics. Power metal-oxide-semiconductor field-effect transistors (MOSFETs) based on SiC are suitable for high-power fields, and their high-temperature gate oxide reliability is one of the most concerned characteristics. In this paper, the high-temperature gate oxide reliability of self-developed SiC MOSFETs is compared with that of the foreign SiC MOSFETs of the same specification by positive and negative high-temperature gate bias (HTGB) tests. The negative HTGB test results show that the deviation of threshold voltage of self-developed SiC MOSFETs is almost equal to that of the foreign SiC MOSFETs, and the maximum discrepancy between them is about 4.52%. However, the positive HTGB test results show that the deviation of threshold voltage of self-developed SiC MOSFETs is smaller than that of the foreign SiC MOSFETs, with a maximum discrepancy of 11%. The reason for the better performance of self-developed devices is that an appropriate amount of nitrogen is added to the SiC/SiO2 interface, which can passivate interface defects and reduce the generation of fast interface states, so that the total interface state density is minimized.

A modeling data and optimization algorithm driven electrothermal behavior model of gallium nitride high electron mobility transistor (GaN HEMT) is proposed to facilitate the quantitative analysis of problems caused by high speed switching, such as turn-on overvoltage, false turn-on, oscillation and EMI noise. Compared with the traditional behavior models of GaN HEMT, the proposed model can precisely depict the electrothermal characteristics of GaN HEMT in a wide temperature range in both the first and third quadrants by only two compact equations. Meanwhile, the nonlinear parasitic capacitances of GaN HEMT can be accurately modeled by one compact equation. In addition, an optimization algorithm combing the genetic algorithm and Levenberg-Marquardt algorithm is put forward, and a one-step extraction of modeling parameters is realized based on this optimization algorithm and modeling data, which can reduce the modeling time and work load to a certain degree. Results show that the proposed modeling method can precisely model multiple types of GaN HEMT devices manufactured by different companies. Finally, the correctness and effectiveness of the proposed modeling method was verified by the well-matched simulated dynamic waveforms and experimental measurement data.

To improve the performance of modern unipolar power diodes and further break through the "Silicon limit", by increasing the junction depth of P+ region in traditional JBS diodes and introducing a super junction structure to reduce the chip thickness, the contradiction between on-state voltage drop and reverse blocking voltage of traditional unipolar devices is alleviated and the conduction current density of devices per unit area is improved. The effects of P-pillar concentration, N-pillar width and N-pillar concentration of super junction JBS diode on the forward conduction and reverse blocking characteristics are analyzed using a numerical method. The forward conduction and reverse blocking mechanism of super junction JBS diode is analyzed using the theory of electric field coupling effect, and a super junction JBS diode with 300 V is designed.