Aimed at the problem that the switching frequency under the min-type switching law is too high to be applied in engineering practice, a switched system model of Boost converter operating in continuous conduction mode (CCM) is established, and a novel switching law based on common quadratic Lyapunov function is proposed. According to the mathematical expression of the switching law, the steady-state and dynamic performances of the converter are analyzed, and the regulation mechanism of the converter's switching frequency under the switching law is described. Simulation and experimental results show that under the proposed switching law, the Boost converter's switching frequency is controllable and the Zeno behavior which is specific to a switched system would not occur. Compared with those under the existing control strategies, the converter under the proposed strategy has a good dynamic performance, with fewer voltage fluctuations and a shorter settling time when suffering external disturbances.

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.

The lithium-ion battery equalizer based on switched inductor is still of strong practical value in low-power portable electrical equipment. However, the switching devices in the equalizer operate in a hard-switching state under traditional control strategies. A soft-switching implementation algorithm for battery equalizer based on switched inductor in continuous current mode is proposed. The determinants of the inductor current of the equalizer and the charging and discharging current of a battery cell are analyzed. Then, a soft-switching implementation algorithm for the switching devices in the equalizer is proposed, and its control accuracy is analyzed. The equivalent impedance and open-circuit voltage of the battery cell can be obtained in real time by detecting the change rate of battery cell voltage and charging current, which further ensures the accuracy of the algorithm. Experimental results show that the proposed soft-switching control algorithm has a good performance.

The electric-field coupled wireless power transfer (ECPT) system possesses several advantages, including lightweight coupling pole plates, cross-metal power transmission and negligible eddy current losses. Specifically, the par-ity-time symmetric ECPT(PT-ECPT) system characterized by its capability to maintain a constant output under variations in the coupling pole plate spacing exhibits promising application prospects. Consequently, the electric-field radiation distribution of the PT-ECPT system was studied. The theoretical analysis, simulations and experimental results indicate that compared with those of the conventional resonant ECPT systems, the electric-field distribution of the PT-ECPT sys-tem is more concentrated in the regions of strong coupling while maintaining identical output power. This concentration is particularly pronounced when the coupling coefficient is small, which makes the PT-ECPT system more secure under conditions of reduced coupling coefficients.

Owing to its advantages such as simple structure, strong robustness and good dynamic and static performances, model predictive control (MPC) has been widely applied to three-phase voltage source PWM rectifier systems. However, the PI linear regulator adopted in the voltage outer loop of MPC affects the dynamic performance of DC-side voltage. Aimed at this problem, a virtual torque impulse balance control strategy is proposed to achieve a rapid convergence of DC-side voltage through only one time of regulation. To realize this strategy, the expression of virtual torque is derived based on the mathematical model at first. Second, the virtual torque impulse balance control equation under load mutation is analyzed and established according to the fact that the DC-side output voltage will remain unchanged before and after load mutation while combining the principle of power conservation. Afterwards, the acting time of zero and forward vectors can be obtained. Finally, the virtual torque impulse balance control of the three-phase voltage source PWM rectifier system under load mutation is realized through simulations and experiments, which verifies the correctness and effectiveness of the proposed algorithm.

To ensure the safe, reliable and economic operation of high-speed railway, a multi-dimensional control method for the power supply operation energy of high-speed railway cophase power supply system is proposed. The composition structure and power supply process of the power supply system are analyzed, and a power flow controller is used to compensate the power of the system, thus ensuring its stable operation. Combined with indicators such as three-phase imbalance degree and distortion of voltage and current waveforms, the optimal load model of operation energy is constructed to minimize the loss of transmission energy. Through the active and reactive power compensation for current in two power supply arms, the negative-sequence current is eliminated. A control strategy for the railway power conditioner is formulated, and the changes in the step-down transformer are obtained to ensure a stable DC-side voltage. Afterwards, a proportional integral controller is used to obtain the ideal value of current and get the control signal, thus realizing the multi-dimensional control of power supply operation energy. Simulation results show that the proposed multi-dimensional control method can improve the three-phase current balance degree and achieve an effect of voltage sharing stability.

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.

To improve the state-of-charge(SOC) prediction accuracy of lithium battery, a prediction method based on the fusion model of Attention mechanism and convolution neural network-long short-term memory(CNN-LSTM) is proposed. This model uses one-dimensional CNN and LSTM neural network to learn the nonlinear relationship between SOC and lithium battery discharge data, as well as the long-term dependence existing in SOC sequences. At the same time, it adopts a "many-to-one" structure and establishes a mapping relationship between the SOC at the present moment and the discharge data at multiple historical moments, and pays attention to the historical discharge data which has a greater influence on the SOC at the present moment through the Attention mechanism, thus further improving the SOC prediction accuracy. The SOC prediction experiments under dynamic conditions show that the average prediction error of the proposed method is 0.89% under different temperature conditions, which is 81.2%, 66.7% and 56.5% lower than those of SVM, GRU and XGBoost algorithms, respectively. In addition, this method is also superior to LSTM and CNN-LSTM models that do not combine the Attention mechanism, showing a higher prediction accuracy and higher application values.

With the increasing attention to environmental issues, more and more distributed energy systems represented by microgrids are appearing in the power system, which also poses some challenges to the traditional power systems. For example, the delay in digital control system, variations in grid impedance of weak grid and the interaction between parallel converters in microgrids will cause adverse effects on the stable operation of microgrids. On this basis, a novel type of grid-forming control method for microgrid considering control delay and variation in grid impedance is put forward to enhance the stability of microgrids under uncertainties. First, the above problems are modeled, and a delay compensation method is proposed to improve the robustness of the control system with respect to the variation in grid impedance. Then, a feedforward loop is introduced into the control system to protect it from the interference of parallel inverters in microgrids. Finally, experimental results demonstrate the effectiveness and superiority of the proposed control method.

Aimed at the problem of wide frequency range and large circulating current with the traditional frequency-controlled LLC resonant converter in wide output voltage applications, a fixed-frequency PWM controlled hybrid bridge dual-LLC resonant converter is studied. According to the difference in the primary-side structure, the converter has three forms of topology, i.e., half-bridge-half-bridge, half-bridge-full-bridge and full-bridge-full-bridge, in which the primary-side structure is in parallel and the two transformers on the secondary-side are in series. Compared with the traditional frequency-controlled LLC converter, the three topologies always work at the resonant frequency, which reduces the switching frequency range. In addition, under the PWM control strategy, the three topologies can achieve 2, 3 and 4 times voltage gain, respectively, thereby adapting to wide voltage scenarios. At the same time, the circuit has a low circulating current loss and a good soft switching performance. Simulink simulation and experimental results verified the feasibility of the proposed scheme.