In traditional power systems, power electronic devices are predominantly governed by grid-following control. However, with the increasing share of renewable energy, new power systems face issues such as a lack of inertia and damping, which threatens the system stability. The grid-forming energy storage technology based on virtual synchronous generator (VSG) can simulate traditional synchronous generator and actively support the system voltage and frequency, thereby enhancing the system stability. As a result, this strategy has attracted widespread attention from scholars. At present, various VSG control strategies have been developed. However, different control strategies result in challenges in unified parameter tuning, and the grid-forming capability may not meet standard requirements in some cases. Firstly, on this basis, parameter tuning is carried out according to national and power industry standards, and an active/reactive power small-signal model is established to ensure that the designed parameters meet national grid-forming standards. Subsequently, grid-forming energy storage VSG need to have seamless switching functionality at the application level, so as to reduce the impact of grid-connected current. Then, a novel pre-synchronization strategy based on eliminating phase-angle jumps is proposed, featuring advantages such as simplicity and ease of engineering implementation. Finally, simulations and experiments validated the feasibility of the proposed parameter design, as well as the effectiveness of the seamless switching strategy.

The unique characteristics of source-grid-load in oilfield distribution networks make the power quality issues particularly prominent. The power quality assessment and comprehensive governance strategies for oilfield distribution networks are studied. By monitoring and tracing the harmonic characteristics of loads at a typical station, the types, features and distribution of harmonic sources are revealed, and the level of power quality is quantitatively assessed. Furthermore, aimed at the harmonic sources, a double-layer harmonic governance scheme using active and passive measures is proposed. Passive filters are designed based on reactive power compensation, and a harmonic optimization compensation objective function for the local power grid is established. Simplified geometric calculations combined with nonlinear programming algorithms are employed to find the optimal solution, thus determining the optimal placement and capacity of active filtering devices in the distribution network. Finally, the effectiveness of the proposed algorithm was validated using an IEEE 33-bus test system. In addition, governance experiments in oilfield distribution networks were carried out, and the overall harmonic performance was optimized with active filters of the minimal quantity and smallest capacity, reducing the voltage total harmonic distortion (THD) from 7.2% to 2.1% and current THD from 44.5% to 7.1%, thus proving the efficacy of the proposed scheme.

The problem of neutral-line voltage harmonics in Zhangbei flexible HVDC transmission system results in the following effects. The capacitor in a neutral-line voltage transformer will generate harmonic current due to the influence of high-order harmonics in the system, which makes the capacitor device heat up seriously and fail to work accordingly. The switching of capacitors may cause harmonic amplification in the system, which may also affect the stable operation of other electrical equipment nearby and thus pose a major threat to the safety and normal operation of the power system. To solve this problem, first, a harmonic analysis model of an modular multilevel converter (MMC) is established, and the harmonic interaction between AC and DC in a multi-terminal flexible HVDC transmission system is analyzed in detail. Then, the research results of harmonic characteristics of a converter station are further applied to Zhangbei flexible HVDC transmission system, the characteristic harmonics of the neutral-line voltage of the system are obtained. Finally, a model of Zhangbei flexible HVDC transmission system is also built, and a control strategy of DC active damping is adopted to suppress resonance using the PSCAD simulation software, and it is verified that this strategy can effectively suppress harmonics of the neutral-line voltage.

To solve the problem of impedance mismatch in a DC microgrid system, a stability discrimination method for DC microgrid based on convolutional neural network (CNN) and long short-term memory (LSTM) network is proposed. First, a CNN-LSTM composite network model is constructed, and the basic structure and principle of the proposed method are expounded. Second, a simulation model of the DC microgrid system is built in MATLAB/Simulink, and a case study is carried out to describe the implementation process of the proposed algorithm in detail. Finally, the performance of the proposed method was compared with those of the artificial neural network (ANN), CNN and LSTM models, and the experimental verification was carried out on a hardware-in-the-loop simulation test platform. Experimental results show that the proposed method can automatically extract features and achieve fast and accurate stability discrimination of the DC microgrid system.

The laser wireless power transmission (LWPT) technology offers advantages such as long-range capability, high directivity and high power density, showing great application promise in the fields such as unmanned aerial vehicle (UAV) charging. However, the environmental disturbances including atmospheric scattering, absorption and turbulence induce strong nonlinearity and time-varying characteristics in a medium transmission state. The conventional mechanism models rely on environmental parameters, so they are unsuitable for online awareness. To solve this problem, a feature-attention enhancement neural network (FAENN) is proposed, which enables high-accuracy online prediction of transmission efficiency by only using easily measurable electrical signals such as laser diode current and photovoltaic current. The architecture integrates feature-wise gating with residual connections to balance the modeling capacity and training stability. Experimental results show that this model achieves an R² of 0.995 54 on the test set, significantly outperforming the linear regression, support vector regression and feedforward neural network. On a 6-m LWPT experimental platform, a mean absolute error of only 0.036 kW/m² in irradiance power density prediction was obtained. The proposed method requires no atmospheric sensors, and it has high accuracy, low latency and strong generalization capability, providing reliable state awareness support for intelligent LWPT systems.

The wireless power transfer technology is usually employed to charge batteries that come with the load. First, to prolong the battery life, a novel compensation network with constant-current and constant-voltage output characteristics based on a bilateral LCC compensation network is proposed, which can achieve the switching of an introduction power transfer (IPT) system between a constant-current output mode and a constant-voltage output mode by using only one variable capacitor on the primary side, thereby reducing the number of components and AC switches. Second, the corresponding compensation parameter design principles are put forward based on the safe charging strategy, so as to guarantee that the fluctuation rates of load power and power factor angle are within the safety threshold during switching, which improves the charging safety of the system. Finally, a 30.0 W experimental prototype was constructed with constant output voltage of 20.21 V and constant output current of 1.14 A, thus verifying that the novel compensation network has characteristics in constant-current and constant-voltage output modes. During the switching between the output modes, the output power was 19.8 W with a power factor angle of 73.17° in the constant-current mode, and the output power was 26.1 W with a power factor angle of 76.57° in the constant-voltage mode. Therefore, the analysis of the compensation parameter design principle was verified.

A wireless power transfer (WPT) system usually needs dual-side cooperated control for efficiency optimization and power regulation, which requires the establishment of a wireless communication link between the transmitter and the receiver. Phase shift keying (PSK) communication is a good choice for WPT systems because of its advantages of high security and low hardware cost. However, the converter phase modulation required by the PSK communication will cause output power and voltage fluctuations. The relationship between the phase modulation depth and output fluctuation amplitude is analyzed. Then, a pulse density modulation-based feedforward power compensation method is put forward to compensate for the output voltage fluctuations caused by the PSK communication. Experimental results show that the proposed power compensator can suppress the output voltage fluctuations to an insignificant level without a large output filter capacitor, indicating that the proposed method overcomes the main drawback of PSK communication in WPT systems.

The potential of gallium nitride (GaN) power devices in enhancing the high power density and efficiency of aerospace power systems is focused on, and a 250 W GaN aerospace secondary power supply prototype with an integrated controller and driver is designed. The high-frequency transformer winding structure is optimized by Ansys simulations to improve the output efficiency. Experimental results show that the peak output efficiency of proposed GaN aerospace power supply reached 94%, and its power density was as high as about 12 W/m². Compared with those of the power supply of the same grade silicon device, its efficiency was 3.8% higher, and its power density was 2.7 times higher. In addition, the results of single-particle radiation experiments verified the anti-irradiation characteristics of GaN devices.

First, according to the working characteristics of pump-type loads of an aero permanent magnet synchronous motor (PMSM), the sensorless operation of the motor is realized based on a nonlinear flux observer, and an improved time-delay compensation strategy is proposed to obtain the command voltage. Due to the influence of the inverter’s nonlinear time-delay, the phenomena such as an increase in the dq-axis current coupling effect and the time-delay of estimated rotor position will occur in the feedback current, which degrade the sensorless control performance. Then, to address this issue, an adaptive disturbance observer is designed to obtain the q-axis disturbance voltage caused by the inverter’s nonlinear time-delay under full-speed SVPWM modulation. Finally, the compensation time estimated in real time is obtained under the current control strategy with i_d=0, which is further equivalent to the three-phase voltage compensation value acting on the given three-phase voltage. The proposed nonlinear time-delay compensation strategy for inverters put forward was verified by experiments, and results show that the proposed strategy can effectively improve the sensorless control performance of the nonlinear flux observer at low speeds.

In the traditional hybrid model flux observers (HMFO), errors exist in flux estimation due to phase deviation at low speeds, and the case of parameter mismatch will even bring serious challenges to their stability. To improve the accuracy and parameter robustness of flux observers, a flux observation model taking phase compensation and parameter mismatch into account is adopted, a transfer function for phase compensation is used, and an extended state observer (ESO) is introduced to conduct feedforward compensation for the disturbances caused by parameter mismatch. Finally, phase compensation comparison experiments, parameter robustness experiments, load sudden change experiments and experiments at extremely low speeds for a motor during its startup and in its full speed range were designed. Experimental results show that the proposed control strategy can enhance the system’s robustness with respect to parameter disturbances and improve the estimation accuracy of the system, and they also verify the effectiveness and feasibility of this control strategy.