Temperature sensitive electrical parameter method has characteristics such as strong online capacity, non-invasiveness, and rapid response, so it has become a research hotspot at present. The on-state voltage drop is taken as a temperature sensitive electrical parameter, and an online monitoring method for IGBT junction temperature is studied based on the on-state voltage drop. First, the data of on-state voltage drop, collector current, and junction temperature of IGBT is obtained through the double-pulse test circuit. Then, based on the measured data, a three-dimensional mapping representation model of IGBT collector current, junction temperature, and on-state voltage drop is constructed. Finally, a novel on-state voltage drop sampling circuit was designed, and an online monitoring experimental of IGBT junction temperature was conducted. Experimental results verified the accuracy and validity of the obtained three-dimensional junction temperature representation model.

A novel low delay and low power consumption low-to-high level shift circuit with a logic correction function is proposed, which uses a low delay level shift circuit and a low power consumption level shift circuit to work in parallel. After the logic is corrected, the low level between 1 V and 1.5 V is converted to a high level of 5 V, so this circuit can be widely applied in GaN driver circuits. Based on the 0.5 µm BCD process, 1.5 V power supply low voltage and 5 V power supply high voltage, the circuit is verified at 5 MHz. Results show that although the layout area of this circuit increases as a whole, the rise and fall delays are reduced to 2.3 ns and 1.8 ns, respectively, with a total power consumption current of only 11 μΑ.

Aimed at the problem that the simulation of electromagnetic radiation interference of a switching power supply module is not combined with its actual working conditions, a method combined with near-field scanning was proposed. First, a simulation model of the switching power supply was built by software Cadence Allegro, and the software Cadence Sigrity was used to obtain the near-field radiation image and data by performing eletromagnetic radiation simulations of the switching power supply module. Then, a near-field scanning system of electromagnetic radiation was built to test the electromagnetic radiation interference of the switching power supply module, and its near-field electromagnetic radiation cloud map and electric field distribution data were obtained. Finally, by comparing the electromagnetic radiation distribution data obtained from near-field scanning and simulations, the simulation results were verified, and the MOSFET switch tube device and the surrounding circuit in the switching module were determined to be the source of electromagnetic radiation with the highest intensity.

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.

For evaluating the capacity of wind powers, photovoltaics and other power electronic grid-connected units supporting power systems, the core foundation is to correctly understand the unit's functional role (i.e., the unit characteristics) that unit adjusts its own internal voltage amplitude/frequency according to the active/reactive power imbalance. However, the mainstream PLL-based grid-connection structure in power electronic units seriously hinders the understanding of the unit's functional role. In particular, based on a specific PLL-based grid-connection structure, the industry and academia at present form a "grid following" role perception that the internal voltage of unit follows the grid voltage or terminal voltage, and have not recognized the functional role that the unit should take during the system operation. Therefore, through an in-depth understanding of the independent excitation-response mechanism of current control which is hidden under the PLL-based grid-connection structure, i.e., the internal voltage response depends on current excitation alone, the functional role of PLL-based grid-connected units in which the active/reactive power imbalance independently adjusts the internal voltage amplitude/frequency is clarified. Afterwards, a role characterization method for unit is proposed based on the relationship between active/reactive power imbalance excitation and internal voltage amplitude/frequency response, i.e., the amplitude-frequency motion equation. Finally, the inevitability of characterizing the role of PLL-based grid-connected units through the relationship between power excitation and internal voltage response is elaborated on, and the existing limitations in the understanding of the role of PLL-based grid-connected units in industry and academia are pointed out.

The new generation of wide bandgap power semiconductors such as SiC and GaN are driving the rapid high-frequency, high-efficiency, and small volume development of power electronic equipment. However, they are also more likely to interfere with sensitive loads, affect wireless communication, and even endanger their own safety and reliable operation, which poses great pressure and challenges to the electromagnetic compatibility (EMC) performance of power electronic equipment. In recent years, the radiated frequency(RF) characteristics of power switches, wideband electromagnetic models of magnetic components, electromagnetic radiation mechanisms of switched mode power supplies, near-field characteristics of wireless power transmission(WPT), and the new designs of electromagnetic interference(EMI) filters have become current research hotspots and received continuous attention from academia and industry. The Journal of Power Supply has specially released the album "Electromagnetic Compatibility in Power Electronic Systems" to promote the exploration of difficult and hot issues in the field of EMC analysis and design of power electronic systems.

Nowadays, wide band gap(WBG) semiconductor power electronic devices have caused increasingly serious electromagnetic interference(EMI) problems as noise sources due to their high switching frequency, fast switching speed and large parasitic parameters. However, the conventional study on noise sources mainly focused on the conduction emission frequency range within 30 MHz, and how to evaluate the impact of noise sources within the radiated emission frequency range(30-300 MHz) still remains uncertain. Therefore, an enhanced analytical EMI model for WBG devices is proposed. Compared with the conventional asymmetric trapezoidal wave EMI model, the proposed model takes into account the nonlinear characteristics of junction capacitor and transconductor in WBG devices in detail for the first time. The impact of nonlinear parameters on noises within the radiated emission frequency range is evaluated, and the application of the proposed model to the suppression of noise sources in this frequency range is further put forward. Simulation results demonstrated the accuracy of the proposed calculation method, and the results of hardware tests based on SiC devices were consistent with the theoretical analysis.

The common-mode(CM) inductor is composed of windings and a magnetic core. Mn-Zn ferrite can be used as the magnetic core of CM inductor, and the frequency-dependent characteristics of its high-frequency parameters make the CM inductor exhibit non-linearity within a range of 150 kHz-30 MHz. It is difficult to accurately predict the impedance characteristics of the CM inductor in a high-frequency band due to the large deviation between the traditional lumped circuit model of CM inductor and the measured impedance characteristics. The effects of material parameters of the magnetic core and the winding scheme on the high-frequency impedance characteristics of CM inductor are analyzed, and the mechanism of magnetic material parameters and the winding structure affecting the distributed capacitance is described from the perspective of the distributed capacitance characteristics of CM inductor. A wide-band impedance simulation modeling method for CM inductor with the consideration of related frequency-dependent parameters of magnetic core was proposed, and its validity was verified by combining with the impedance test result.

An evaluation platform for the CM noise suppression characteristics of high-frequency transformer was established, which was suitable for batch applications in engineering. The conduction mechanism of common-mode (CM) noise in a transformer was analyzed, and the conduction characteristics of CM noise along the coupling path in the transformer was investigated for evaluating the transformer's capability of suppressing the CM noise. First, a function generator was used to generate a high-frequency voltage pulsation signal, which was assigned on the primary winding of the transformer to simulate the transmission characteristics of CM noise. Then, an oscilloscope was used to capture the voltage drop generated by the CM signal on the sampling resistor to judge the suppression effect of the transformer on the CM noise, so as to analyze the influence of the sampling resistor selection on the evaluation results. The effectiveness of the proposed evaluation method for the CM noise suppression characteristics of transformer was verified by comparing the evaluation results with the test results of conducted electromagnetic interference spectrum.

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.