This paper presents a novel maximum power point tracking (MPPT) control method for variable-speed constant-frequency wind energy conversion systems (WECS). The proposed tracking method combines the ideas of sliding mode (SM) control and extremum seeking control (ESC). The only input needed in this method is the output active power of the generator. It avoids some difficult problems in traditional tracking algorithms, such as measuring the wind velocity, needing wind-turbine model and parameters, and detecting the gradient of power vs. rotor speed. The proposed method is tested on a double fed induction generator based wind energy conversion system. The back-to-back converters connected to the generator adopt the vector control method. The simulation model of an example WECS is established in MATLAB. The reference input of speed loop in the vector control is the optimal result resulting from the MPPT based on sliding mode ESC. Simulation results confirm the validity of this method.

In this paper, the consensus control of unmanned surface vehicles (USVs) is investigated by employing a distributed model predictive control approach. A hierarchical control structure is considered during the controller design, where the upper layer determines the reference signals of USV velocities while the lower layer optimizes the control inputs of each USV. The main feature of this work is that a post-verification procedure is proposed to address the failure states caused by local errors or cyberattacks. Each USV compares the actual state and the predicted one obtained at the previous moment. This allows the estimation of local perturbations. In addition, the failure state of the USV can also be determined if a preset condition is satisfied, thus forcing a change in the communication topology and avoiding further impact. Simulations show that the proposed method is effective in USV formation control. Compared with the method without post-verification, the proposed approach is more robust when failure states occur.

Multiple batteries in uninterruptible power supply (UPS)-microgrid systems based on multiagents composed of multiple electric vehicles (EVs) can encounter state of charge (SoC) consistency problems. To solve this differential expansion and controller saturation problem, an adaptive command filter sliding-mode control strategy based on virtual synchronous generators (VSGs) and considering the power allocation principle is proposed. First, based on directed graph theory, an SoC consistency algorithm and power allocation strategy for multiple EVs were proposed, forming a dc power system with a fixed communication topology. Second, the rotor motion equation of synchronous generator (SG) is introduced into the inverter control algorithm to form the mathematical model of VSG. Third, a low-pass filter (LFP) was introduced in the voltage control process to simulate the excitation attenuation characteristics of the SG. Based on the above, a backstepping control strategy, including a command filter and sliding mode controller is proposed, which improves the operating stability of the system based on the system errors of angle, frequency, and power output. Finally, the UPS-microgrid system based on multiagents is simulated to demonstrate the stability of the system and the effectiveness of the proposed control strategy.

The complicated manufacturing process and poor industrial environment inevitably produce unacceptable scratches on glass screen surface. In this study, a machine vision system is developed to automatically detect fine scratch, which has a width smaller than 30 $\mu \text{m}$ , on glass screen surface for the purpose of appearance quality assessment. The imaging hardware of the proposed machine vision system is made up of a high-resolution camera and a wide field lens so that a high-quality image is achieved in a relatively large image area. The captured glass screen images were first classified with YOLOv3 to exactly distinguish fine scratches in two other kinds of defects including dusts and stains. Then, the U-Net network was applied on the selected scratches to estimate their dimensions approximately. The proposed algorithms combination has a fast image processing speed and it is able to effectively reduce the false segmentation of other defects. The results of the developed machine vision system show a relatively good agreement with the well-established microscopic method. It demonstrates our machine vision method is able to image and quantitatively analyze scratches with dimensions between 25 and 100 $\mu \text{m}$ .

The continuous development of microgrid’s technology creates favorable conditions for the access of distributed energy. Firstly, in order to consider the interests of the demand side and the power side, this paper presents a dual-layer optimal dispatching model of microgrid based on demand response. The objective of the first-layer optimization is to obtain the maximum load satisfaction and to optimize the load curve. The objective of the second-layer optimization is to make the microgrid system economical and environmentally friendly and to optimize the power utilization ratio. And a microsource control strategy based on the isolated microgrid is proposed, which can optimize the operation state of battery and improve the economy of the system. Finally, the Nondominated Sorting Genetic Algorithm-II (NSGA-II) is adopted to solve the optimal scheduling problem of the isolated microgrid. The simulation results indicate that the microsource scheduling strategy proposed in this paper can improve the operation economy and environmental conservation of the system. It can improve the reliability of microgrid power supply and reduce energy waste.

Aiming at improving the harmonic spectra spreading effect, two randomized pulse position modulation strategies are proposed for three-phase four-leg inverters. Based on the volt-second balance law and the fixed switching frequency, the first proposed strategy places the center randomly during one carrier cycle with a limited degree of freedom, and the second proposed strategy randomly changes the carrier slope in each carrier cycle. To get better randomization effect of the proposed strategies, Well Equidistributed Long-period Linear algorithm was introduced to generate random numbers. In order to verify the validity of the proposed strategies, the modulation strategies are implemented with dSPACE DS1007-based real-time operating system. The experimental results show that the proposed strategies have dispersed the discrete harmonics to a wider sideband. Compared with the first strategy, a larger degree of freedom can be achieved in the second proposed strategy with lower harmonic spikes.