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Aiming at the formation control problem for unmanned surface vehicles under input overload and external disturbance, a leader-follower formation control law based on input saturation and the adaptive super-twisting algorithm was designed in this paper. Firstly, the mathematical model of underactuated unmanned surface vehicle formation based on the leader-follower method is established, and the virtual expected velocity is designed by the back-stepping method to improve the control accuracy of formation. Secondly, the parametric uncertainties and unknown external disturbances in the USV’s dynamical model are compensated by the proposed adaptive super-twisting control laws. In addition, the input saturation function is added to the controller to avoid machine necrosis caused by input overload. Finally, Simulation results show that the controller can roughly keep the trajectory of the USV consistent with the expected trajectory and ensure that the input values are within the safe range, which proves the effectiveness of the method in this paper.

We propose an ontological Chinese legal consultation system (CLCS) based on Chinese legal characteristics by integrating statutes and judicial precedents to facilitate the retrieval of relevant statutes and judgments for the general public. Ontology, an emerging research topic in recent years, incorporates a hierarchical structure and supports logical reasoning, which can reduce semantic ambiguities and extract implied semantic information. We constructed statutes ontology and a case ontology using a bottom-up method and a top-down method, respectively. Then, to test the retrieval precision of the proposed CLCS, we performed experiments using emotional damage compensation as an example by combining genetic algorithm and k-nearest neighbor approaches. Experimental results demonstrate that the proposed method improves retrieval precision.

With an increasing number of inverter-interfaced generators (IIGs), the power system is undergoing massive shifts toward the power electronic dominated power system. Such paradigm change poses significant challenges to existing fault analysis theory and the protection system, as a result of the disparate short-circuit response. Given this, the fault analysis theory needs to be further investigated and expanded to address issues arising from the new grid paradigm. Under this context, this article proposes an analytic model for short-circuit analysis of IIGs with decoupled sequence control (DSC) based on the Laplace transform. With the proposed model, the analytic fault current expression can be obtained and the fault characteristic can be analyzed. Compared with existing studies, the proposed model distinguishes itself by three key merits. First, the proposed model takes into account the delay feature of the controller, which enables transient analysis. Second, the model covers the impact of controller parameters and low voltage ride through strategy in detail which is missing in the most existing literature. Third, the proposed model provides a theoretical foundation of IIGs with DSC in the fault analysis, which makes it more applicable for the protection setup issues in reality. In the end, the correctness and feasibility of the proposed model is validated by the simulation and experimental result. [ABSTRACT FROM AUTHOR]

This article proposes an efficient thermoelectric temperature control system based on an improved proportional integral differential (PID) algorithm in which energy feedback technology is used to enhance thermoelectric cooling. In the proposed power management system, two groups of batteries are efficiently and alternatingly charged and discharged such that the information of the circuit can be monitored in real time. The PID algorithm is improved by using the idea of a state machine to control the thermoelectric coolers (TEC) through an H-bridge circuit with pulsewidth modulation. Finally, the energy feedback circuit combined with improved synchronous switching technology is designed to recycle the energy to drive the sensor. By inputting current of 3.1 A, a wide range of temperature control from 1.437 to 60.187 °C was implemented. While targeting a temperature of 10 °C at an ambient temperature of 22 °C, the proposed temperature control system had a control time of 30.5 s, compared with 287 s when using the conventional method, with an accuracy of 0.1 °C, and an error of only ±0.35 °C. The results confirm that electric energy at a peak voltage of 1.2 V and current of 24 μA can be recovered. The proposed energy feedback system can thus improve the efficiency of energy utilization of TEC from a peripheral circuit. [ABSTRACT FROM AUTHOR]

To promote the integration of renewable energy resources into modern energy systems, high-voltage dc (HVdc) and circuit breaker (CB) technologies have become critical to achieving secure and efficient energy transmission. This article reviews the technical development of the related areas, compares diverse breaker concepts and topologies, investigates possible coordination and testing solutions, and points out the remaining challenges as well as future needs. The time-domain simulation and comparative analysis are adopted in this article to analyze and compare the performances of different HVdc CBs. By making use of different selectivity levels of multiterminal HVdc (MTdc) grids, the suitable planning and placement of HVdc CBs can be conducted. Furthermore, by providing insights into the performance of HVdc CBs, the work presented in this article can serve as a useful asset for the upcoming standardization and industrial application process of HVdc grid and CB design and testing. [ABSTRACT FROM AUTHOR]

Using Fe nanoparticles as raw material, we manufactured Fe16N2 nanoparticles by hydrogen reduction and ammonia nitriding process. X-ray diffractometer (XRD) and Mössbauer spectroscopy analyses show that the prepared nanoparticles are composed of Fe16N2 and $\alpha $ -Fe. The proportion of the Fe16N2 phase could reach 75%, and the saturation magnetization of the nanoparticles reaches 197 emu/g. The Fe16N2 nanoparticles are mixed with paraffin, and the microwave absorption properties of the composites are measured. The reflection loss (RL) of the Fe16N2/paraffin composite can reach −18.3 dB at 4.8 GHz, with a thickness of 2.2 mm. The ratios of the magnetic loss and dielectric loss are 40% and 59%, respectively. Only 1% (100%–40%–59%) of the incident microwave energy is reflected, which shows Fe16N2/paraffin composite is a potential candidate for microwave absorbing materials. [ABSTRACT FROM AUTHOR]

Due to the increasing penetration of gas-fired units and power to gas facilities, the electrical power system and natural gas system are more and more bi-directionally coupled. To tackle the challenges on the optimal scheduling operation of an integrated gas and power systems (IGPS), this article focuses on developing a novel approach to build a continuous spatial-temporal optimal operation schedule model. In the light of different time constants of the electrical power and natural gas systems, the continuous spatial-temporal optimal operation schedule model of IGPS is formulated in function space. Additionally, Bernstein polynomials are used to reformulate the continuous spatial-temporal optimization problem of IGPS to mixed-integer linear programming. In the study cases, the simulation results of a simple integrated system and a combined IEEE 39-bus power system and Belgian natural gas network demonstrate the accuracy and effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

HVDC technologies are widely acknowledged as one of solutions for the interconnection of renewable energy resources with the main electric power grid. The application of the latest modular multi-level converter (MMC) makes power conversion much more efficient. Due to the relatively low impedance in a DC system, DC fault currents may rise to an extremely high level in a short period of time, which can be very dangerous for HVDC converters. To improve the sustainability and security of electricity transmission, protection solutions for HVDC systems are being developed. Nevertheless, they have various drawbacks on fault signal detection and timely clearance. This paper proposes a protection method that provides a fast and reliable solution addressing those drawbacks. A protection algorithm based on travelling wave simulation and analysis is proposed to detect abrupt transient signals. The algorithm shows high efficiency, reliability, selectivity and has low sampling frequency requirements. The proposed protection method has been validated through a cyber-physical simulation platform, developed using a real-time digital simulator (RTDS) and IEC 61850 communication links. The obtained results show that the proposed method has good potential for practical applications. [ABSTRACT FROM AUTHOR]

Controllers learned from data are more practical and promising than the existing model-based ones and their capability can be enhanced if a priori information about the controlled plant is available. Under this viewpoint, a data-driven guaranteed cost control (GCC) design is investigated for linear systems with time-varying parameter uncertainties. Initially, the GCC design is shown to be equivalent to an $H_{\infty }$ state feedback control problem subject to a specific disturbance attenuation performance requirement. Then such an $H_{\infty }$ control problem is regarded as a zero-sum game and reduces to seek the stabilizing solution of a parameterized algebraic Riccati equation (ARE). Furthermore, to solve the ARE approximately, a modified simultaneous policy update algorithm (SPUA) and the corresponding data-driven variant based on off-policy reinforcement learning (RL) and experience replay technique is proposed. Finally, a numerical simulation for aircrafts with harsh uncertainties is illustrated to validate the merits of the proposed methods. [ABSTRACT FROM AUTHOR]

For onshore wind farms where all wind turbine (WT) locations are fixed, it is necessary to design corresponding cable connections to collect electricity generated by each WT. The cable connection system should ensure the collection of electricity successfully and reduce the cable cost optimally. Cables are prohibited from crossing restricted land areas, such as reserves, oil wells, and rocky areas. Therefore, in this article, a restricted area is added to the planning area of onshore wind farms. To obtain more accurate final optimized results, we consider topographic factors of onshore wind farms in the optimization process. The algorithm used for cable connection optimization is the dynamic minimum spanning tree. Results indicate the nonnegligible effects of the restricted area and topographic factors on the cable connection topology. The total cable cost savings can exceed 1.8% compared with the reference cable connection topology, in which the topographic factors and restricted area are not considered. [ABSTRACT FROM AUTHOR]

eAssessment The application of multiterminal (MT), high-voltage dc (HVdc) (MTdc) grid technology requires test procedures for the operation and implementation of the protection solutions. The test procedures are usually derived from experience and from extensive measurement data, which, at present, are still not widely available. Based on a hardware-inthe- loop (HIL) method, advanced dc protection testing strategies, utilizing existing experience for ac grids and requirements for MTdc grids, may overcome this gap. [ABSTRACT FROM AUTHOR]