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• This paper proposes a fault location method based on composite traveling wave, which can easily eliminate the traveling wave from adjacent lines. • The traveling wave from other adjacent lines, which is never detailed discussed in previous research, hinders the accurate identification of wavefront. • The refraction coefficient of busbar with multiple transmission lines is negative for current traveling wave, but positive for reflection coefficient. • The time–frequency matrix is able to present the energy of traveling wave in wideband. As the speedy expansion of power gird, the traveling wave fault locator in substation may not always connect to newly added transmission lines in time, which reduces the effectiveness of fault locator. In this paper, an adjacent fault-free line based fault location scheme for newly additional line is proposed. Since the traveling wave from adjacent fault-free line results in severe difficulty for identification of traveling waves from faulty line, the time–frequency matrix is performed to screen traveling waves. Firstly, in order to remove the influence of waves from remote terminals of adjacent fault-free line, the current refraction coefficient is theoretically analyzed. Due to the negative refraction coefficient, traveling waves from remote terminals of adjacent fault-free line can be reduced by the proposed composite traveling wave. Secondly, the time–frequency matrices of composite traveling wave and original traveling wave is obtained by S-transform. Then, these matrices are applied to form ratio matrix which thoroughly eliminated waves from remote terminals of fault-free lines. Moreover, the robustness of the proposed fault location scheme is thoroughly validated by the simulation of PSCAD/EMTDC. Finally, the proposed fault location method has the great accuracy in simulation tests and field data test. [ABSTRACT FROM AUTHOR]

The synchronization of the voltage and current from different terminals is generally unachievable in the power grids at mountainous area, which leads to the fault location method with synchronized data to be impossibly utilized. This paper proposes a voltage distribution based fault location scheme with asynchronous data for three-terminal transmission lines. At first, the faulty section is identified by the voltage computed from each terminal due to the boundaries formed by fault point and tee-point. Since the fault current is stable after the transients decay, the asynchronous calculated voltage and current from the terminals without faults can be synchronized by their angle differences to form the voltage and current at faulty section near the tee-point. Then, the voltage distribution of the faulty section can be obtained from the tee-point and the terminal to find the intersection point of them. In order to fully utilize the fault characteristics in the voltage and current, the earth mode and the minimum of the voltage distribution are applied to optimize the fault location results for grounding faults and multi-phase faults, respectively. Moreover, the robustness of the proposed fault location scheme is thoroughly validated by the simulation of PSCAD/EMTDC. At last, a set of the field data acquired by wave recorders is applied to test the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

Large-scale wind farms are generally far away from load centers, hence there is an urgent need for a large-capacity power transmission scheme for extremely long distances, such as half-wavelength transmission lines (HWTLs), which can usually span thousands of kilometers from large-scale wind farms to load centers. An accurate fault location method for HWTLs is needed to ensure safe and reliable operation. This paper presents the design of a modal voltage distribution--based asynchronous double-end fault location (MVD-ADFL) scheme, in which the phase voltages and currents are transformed to modal components through a Karenbauer transformation matrix. Then, the modal voltage distributions along transmission lines are calculated by voltage and current from double ends. Moreover, the minimums and intersection points of calculated modal voltages from double ends are defined as the fault location estimation. In order to identify incorrect fault location results and reduce calculation errors for the correct ones, air modal and earth modal voltage distributions are applied in the fault location estimations. Simulation results verify the effectiveness of the proposed approach under different fault resistances, distances, and types. Lastly, a real-time digital simulator (RTDS)--based hardware-in-the-loop (HIL) test is undertaken to validate the feasibility of implementing the proposed approach. [ABSTRACT FROM AUTHOR]

Reflected wave identification is the core of single‐ended travelling wave fault location, in which the obvious superimposed oscillation is the main obstacle for precise reflected wave identification with field data. This study proposes a reflected wave identification method based on speeded‐up robust features, which can gradually approximate from the possibly largest fault distance to the near‐end fault distance so as to exclude the reflected wave from time window containing initial wave. In particular, the time window segmentation divides initial wave and reflected wave into two inconsistent time windows, hence the reflected wave from the superimposed oscillation that usually follows the travelling wave can be effectively separated, such that the identification of reflected wave can be significantly simplified. Lastly, the superimposed oscillation is thoroughly analysed while both the field data with and without obvious superimposed oscillation are presented to evaluate the effectiveness of the proposed approach. Field data obtained from 21 substations scattered among Yunnan power grid of China validate the implementation feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

• It concludes that the compensation circuit for HWTL is a low-pass passive filter. • The suitable type and the proper order for half-wavelength transmission lines is analyzed. • The voltage distribution is simulated to verify the feasibility of the proposed method. • Transient responses of tuned lines are compared to verify the superiority. Compensation circuit, which can increase electrical length, is the most feasible solution for flexible applications of half-wavelength transmission lines (HWTL). In previous studies, it is always assumed that the compensation circuit is structured by passive components with identical parameters to represent the distribution parameter of transmission lines. However, the structure of the traditional compensation circuit is actually equivalent to that of the constant k filter, which concludes that the compensation circuit is fundamentally a low-pass filter. In consideration of basic requirements for tuned HWTL, the Bessel filter, which has smooth group delays without waveform distortion, is selected for the calculation of compensation circuit parameters in this paper. Lastly, the Bessel-based compensation circuit is compared to natural HWTL and tuned HWTL with Butterworth filter-based and traditional compensation circuits. Comprehensive cases simulated by PSCAD are undertaken, which validate that the voltage distribution of Bessel-based compensation circuits is quite similar to that of traditional compensation circuits. Moreover, electromagnetic transients can induce significant high-frequency oscillations in tuned HWTL with traditional compensation circuits, but high-frequency oscillation is significantly reduced by Bessel-based compensation circuits. Therefore, the Bessel-based compensation circuit is verified to be a better solution for tuned HWTL. [ABSTRACT FROM AUTHOR]

The phenomenon of wind abandoned caused by fault of transmission lines has occurred frequently. Since fault current output by wind turbine after fault may induce the frequency variation of the fundamental frequency, fault location based on the fundamental resistance is easily invalid. In order to locate fault accurately and rapidly after wind farm transmission line faults, a time‐domain‐based novel fault location method for transmission line of wind farm is introduced in this paper. The main idea of the proposed scheme is to discretise the distributed‐parameter model of transmission line that is given in the form of partial differential equations by using the finite‐difference time‐domain. In addition, the phase current and voltage at both ends of lines are regarded as boundary conditions. Then, the variational iteration method is utilised to calculate transmission line equations to obtain line length function. At last, fault location function is constructed by a minimised objective function. This paper builds wind power transmission line system simulation model and carries out simulation experiments on PSCAD/EMTDC. To verify the performance of the algorithm, several factors are taken into account for simulation including different fault distances, different fault types, different fault resistances, and different fault inception angles. Simulation results reveal the performance of the proposed method to locate fault for transmission lines connected to wind farm with high accuracy. [ABSTRACT FROM AUTHOR]

• This paper proposes a fault location method based on directional traveling wave principle for wind power transmission line. • The similarity of forward current traveling wave and reverse current traveling wave at both ends of line is higher after external fault, while similarity of forward current traveling wave and reverse current traveling wave at both ends of line is lower after internal fault. • Discrete Frechet distance is utilized to calculate similarity coefficient of forward traveling wave and reverse traveling wave at both ends of transmission line. The short-circuit current from the new energy power generator presents special characteristics such as frequency shift, restricted amplitude, unequal positive and negative sequence impedance, high percentage of harmonic content, etc., resulting in the risk of misoperation or rejection of conventional protection. By analyzing the propagation characteristics of traveling wave in the transmission line after the fault, this paper reveals difference between traveling wave waveforms at both ends of the line under internal fault and external fault. The similarity between forward traveling wave and reverse traveling wave at both ends of line is higher when an external fault occurs, while the similarity between the forward traveling wave and reverse traveling wave is lower after internal fault. According to this difference, a pilot protection algorithm based on discrete Frechet distance is proposed, which can calculate similarity coefficient of forward traveling wave and reverse traveling wave at both ends of line to construct protection criteria, and then identify internal and external fault. Through the analysis of PSCAD/EMTDC and experiment platform of hardware-in-the-loop test verify that the proposed protection algorithm can accurately and reliably distinguish internal and external fault. [ABSTRACT FROM AUTHOR]

• Different circuits are compared to identify the most suitable compensation circuit. • The compensation circuit is designed in the modal system. • Capacitance of the compensation circuit are simplified as the shunt reactor. • The designed compensation circuits are compared with the natural HWTL. The compensation circuits are the core to improve the flexibility of practical application of half-wavelength transmission lines (HWTL), which are restricted to the fixed transmission length due to the constant fundamental frequency. This paper proposes a mode-phase transformation based method to design the parameters of compensation circuits after comparison of frequency responses of three kinds of compensation circuits, e.g., T segments, Π segments and L segments. At first, the compensation circuit parameters are obtained in the modal system that separates the coupling multiconductor system into isolated circuits to avoid the complexity of the three-phase system. Then, the compensation circuit parameters can be transformed into multiconductor system by modal-phase transformation, which accomplishes the compensation circuit parameter design in three-phase system. Lastly, the parameters acquired by the proposed method are compared with the natural HWTL. Comprehensive simulations are undertaken which validate that the proposed method is more suitable for tuning HWTL. [ABSTRACT FROM AUTHOR]

DC electronic current transformer is the data source of the system control and protection device, so its measurement delay has always been concerned. In this paper, the DC current transformer is modelled equivalently and the key factors affecting the delay of shunt and the remote module are analyzed. A field test method for the delay characteristics of the DC electronic current transformer is proposed. Moreover, a complex multi-state large current generator and integrated test system are developed. On the basis of the IEC 60044-8 standard transmission protocol, the accuracy of standard signal acquisition with the shunt is better than 0.2%. The maximum output current of the established testing system is 600 A. Based on the field test in an actual HVDC project, transient step and various frequency signal components are applied for analyzing. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) is a promising future power source, which uses hydrogen energy to generate electricity with the byproduct of water. In general, PEMFC includes several strongly coupled subsystems with high nonlinearity and complex dynamic processes. Therefore, proper control strategies are crucial for a reliable and effective PEMFC operation. This paper aims to carry out a comprehensive and systematic overview of state-of-the-art PEMFC control strategies. Based on a thorough investigation of 180 literatures, these control strategies are classified into nine main categories, including proportional integral derivative (PID) control, adaptive control (APC), fuzzy logic control (FLC), robust control, observer-based control, model predictive control (MPC), fault tolerant control (FTC), optimal control and artificial intelligence control. Furthermore, a comprehensive evaluation and detailed summary of their control deigns, objectives, performance, applications, advantages/disadvantages, complexity, robustness and accuracy are conducted thoroughly. Finally, five valuable and insightful perspectives/recommendations are proposed for future research. [Display omitted] • Summarize nine groups of PEMFC system control strategies. • Control complexity, robustness, and accuracy are summarized and evaluated. • Present the advantages/disadvantages of all methods. • Five invaluable and insightful perspectives/recommendations are proposed. [ABSTRACT FROM AUTHOR]

Being one of the most promising renewable energy sources, ocean wave energy (OWE) demonstrates considerable development and application potential. Consequently, various related technologies have rapidly advanced in recent decades, particularly in the field of wave energy converters (WEC). Power take-off (PTO) stands as a vital element within WEC systems. During the planning and implementation of WEC systems, diverse types of PTO systems and control strategies emerge as crucial factors that impact overall power output and stability. To comprehensively review PTO systems, this paper offers a comprehensive overview and discussion of state-of-the-art development status of PTO, including of based structures, working principles and control strategies. In contrast to prior reviews, a more thorough classification and comparison of different PTO systems have been undertaken in this review with the consideration of seven types of PTO systems in total and detailed control strategies for various PTO types. Besides, the proposed framework includes an evaluation and comparison of advantages/disadvantages, application, complexity, and costs for each controller. Lastly, seven invaluable perspectives are proposed for future research. • Summarize seven operation principles for PTOs. • Advantages/disadvantages, types, and applications e of PTOs are summarized. • Present in detail three types of advanced control strategies. • Six invaluable and insightful perspectives/recommendations are proposed. [ABSTRACT FROM AUTHOR]

The vigorous development of renewable energy has induced multiple sources connected to regional distribution networks. However, the high impedance ground fault that appeared in the distribution network can induce an intermittent arc accompanied by extinction and reignition, which may damage renewable energy generation devices severely. Therefore, the detection of arcing faults is profoundly necessary for practice, but the high impedance arcing fault is easily confused with switches of motor or capacitor bank. In order to solve high impedance arcing fault detection, this paper proposes a high impedance arcing fault detection method that combines complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and Teager energy operator (TEO). Firstly, CEEMDAN algorithm is used to extract the intrinsic mode function (IMF) of transient zero‐sequence current (TZSC). According to the correlation coefficient and waveform similarity, which can select maximum correlation coefficient value as the characteristic component of TZSC; Then, TEO is utilized to track the change of signal in real‐time, meanwhile, wavelet singular entropy (WSE) is applied to calculate the characteristic component of TZSC. In particular, high impedance arcing fault (HIAF), motor switching (MS), and capacitor bank switching (CBS) can be effectively identified by comparing WSE. The effectiveness of CEEMDAN‐TEO detection method is verified by simulation, which owns advantages in extraction accuracy, calculation efficiency, and detection accuracy of feature components. [ABSTRACT FROM AUTHOR]

It is essential to develop an accurate model of proton exchange membrane fuel cell (PEMFC) for a reliable operation and analysis, in which unknown parameters usually need to be determined. The inherent nonlinear, strong coupling, and diversification of PEMFC model seriously hinder traditional methods to identify the parameters. For the sake of overcoming these thorny obstacles, Levenberg-Marquardt backpropagation (LMBP) algorithm based on artificial neural networks (ANNs) is proposed for PEMFC parameter identification. Furthermore, the performance of LMBP is thoroughly evaluated and compared with four typical meta-heuristic algorithms under three cases. Simulation results indicate that LMBP performs a higher accuracy and faster speed for parameter identification. In particular, accuracy and convergence speed can achieve as much as 99.8% and 95.9% growth via LMBP, respectively. • LMBP algorithm is applied to PEMFC parameter identification for the first time. • Performance of LMBP is proved via comparison with four meta-heuristic algorithms. • Feasibility of the proposed method is investigated based on a Ballard-Mark-V PEMFC. [ABSTRACT FROM AUTHOR]

The high‐resistance faults at the far end are the most important factor that causes protection failure of HVDC transmission lines. In the initial stage of the transmission lines fault, the transient information of power grid is abundant, and the sequential overlapping derivative (SOD) transform can emphasise the characteristics of the high‐frequency transient signal and its sudden change direction, amplify fault characteristics, and eliminate noise as far as possible, which is of great benefit to identify the high‐resistance faults at the far end. A fault identification method based on the SOD transform of voltage transient is proposed. In this method, the initial fault voltage travelling wave is processed by the SOD transform, and the initial fault voltage is a travelling wave is quickly detected. The set value of SOD transform is obtained according to the traversal simulation fault location, thus the identification criteria of internal and external faults are obtained. The simulation results show that the method can accurately identify the high‐resistance faults at the far end, and it is hardly affected by transition resistance and fault distance. [ABSTRACT FROM AUTHOR]

This study develops a perturbation compensation based sliding‐mode control (PCSMC) strategy of a permanent magnetic synchronous generator (PMSG) for optimal extraction of wind energy. Firstly, PMSG non‐linearities, uncertain parameters, unmodelled dynamics, and stochastic wind speed variations are aggregated into a perturbation. Then, it is estimated by a sliding‐mode state and perturbation observer in the real time. Further, the perturbation estimate is fully cancelled by sliding‐mode controller (SMC) for global control consistency, together with considerable robustness thanks to the sliding‐mode mechanism. In addition, the upper bound of perturbation is replaced by its real‐time estimate; thus more proper control costs could be achieved without over‐conservativeness. Moreover, PCSMC does not require an accurate PMSG model while only the measurement of d‐axis current and mechanical rotation speed is required. Four case studies are carried out, e.g. step change of wind speed, low‐turbulence stochastic wind speed, high‐turbulence stochastic wind speed, and PMSG parameter uncertainties. Simulation results demonstrate that PCSMC can rapidly extract higher power under different wind speed profiles against vector control and SMC. Lastly, a dSpace‐based hardware‐in‐the‐loop experiment is undertaken which validates its implementation feasibility. [ABSTRACT FROM AUTHOR]

• A novel algorithm is proposed to extract maximum power of photovoltaic system. • Discretization for proposed algorithm is designed to solve discrete problems. • An adaptive threshold is used to balance local exploration and global exploitation. • Consider various movement of clouds to evaluate proposed algorithm effectiveness. • Perform an electrical switching design to implement real-time embedded application. This paper proposes an adaptive evolutionary jellyfish search algorithm (AEJSA) to optimally reconfigure photovoltaic (PV) array under partial shading condition (PSC) for real-time maximum power extraction. Jellyfish search algorithm (JSA) is selected owing to its effectiveness for real-time optimization. Besides, a series of discrete operations are performed on JSA to solve the discrete optimization problem of PV array reconfiguration. Due to the inherent drawback of JSA that it is easy to trap at the local optimal solution, an adaptive threshold for changing search mechanism is adopted to balance the local exploration and global exploitation. If the number of times that the value of objective function keeps unchanged exceeds this threshold, three operations (exchange, moving, and inver-over) will be implemented on the whole population for a wide global exploitation. In addition, to verify the feasibility of the hardware implementation of AEJSA, a hardware-in-the-loop test on a RTLAB platform is employed. Eleven meta -heuristic algorithms are applied and compared to AEJSA under objective PSC and subjective PSC to evaluate the optimized performance of AEJSA under various shadow conditions. The simulation results show that the mismatched power loss obtained by AEJSA is smallest, which reduced by 7.26% against gravitational search algorithm. [ABSTRACT FROM AUTHOR]

• IIGA is applied to TEG system reconfiguration for the first time. • Performance of IIGA is proved via comparison with four meta-heuristic algorithms. • Feasibility of the proposed method is investigated based on a 9 × 9 small TEG system and a 15 × 15 large TEG system. • A HIL experiment is undertaken to verify the reconfiguration performance of IIGA. To deal with the problem of low thermoelectric conversion efficiency in thermoelectric power generation (TEG), this work designs an improved immune genetic algorithm (IIGA) to reconfigure TEG system under non-uniform temperature distribution (NTD) conditions to maximize power output. The traditional IGA is a fusion algorithm that combines genetic algorithm (GA) with immune algorithm (IA). Due to IGA's flaws of strict parameter setting and long computation time, three mountain factors are updated dynamically in IIGA to enhance the balance between local exploitation and global exploration. Consequently, the electrical connection of the TEG system is dynamically adjusted and reconfigured via IIGA, which can effectively improve power generation efficiency and reduce power consumption. The effectiveness and reliability of IIGA are testified and compared against four well-established meta-heuristic algorithms under two cases, i.e., 9 × 9 small TEG system and 15 × 15 large TEG system. Simulation results indicate that the output power boost by IIGA reaches 7.502 % under the 9 × 9 small TEG system and 10.281 % under the 15 × 15 large TEG system. Furthermore, a hardware-in-the-loop (HIL) experiment based on RTLAB platform is undertaken to testify the hardware implementation feasibility of IIGA affected by NTD conditions. [ABSTRACT FROM AUTHOR]

Due to the complex structure of the T-connection transmission lines, it is extremely difficult to identify the reflected travelling wave from the fault point and that from the connection point by the measurement from only one terminal. According to the characteristics of the structure of the T-connection transmission line, the reflection of the travelling wave within the line after the failure of different sections in T-connection transmission line are analyzed. Based on the lattice diagram of the travelling wave, the sequence of travelling waves detected at the measuring terminal varies with the fault distance and the faulty section. Moreover, the sequence of travelling waves detected in one terminal is unique at each faulty section. This article calculates the arrival time of travelling waves of fault points at different locations in different sections to form the collection of the travelling wave arrival time sequence. Then the sequence of travelling waves of the new added fault waveforms is extracted to compare with the sequences in the collection for the faulty section identification and fault location. This proposed method can accurately locate the fault with different fault types, fault resistances and system impedances by only single-terminal fault data. Both Power Systems Computer Aided Design/ Electromagnetic Transients including DC (PSCAD/EMTDC) and actual measurement data are implemented to verify the effectiveness of this method. [ABSTRACT FROM AUTHOR]

Summary: This paper designs a novel adaptive fractional‐order PID (AFOPID) control of a permanent magnetic synchronous generator (PMSG)‐based wind energy conversion system, which attempts to extract the maximum wind power by using a linear perturbation observer. The combinatorial effect of generator nonlinearities and parameter uncertainties, unmodelled dynamics, and stochastic wind speed variation is aggregated into a perturbation, which is then estimated in real time by a linear extended‐state observer called high‐gain state and perturbation observer. Besides, the perturbation estimate is used as an auxiliary control signal which is fully compensated by a fractional‐order PID (FOPID) controller to achieve a globally robust control consistency, simple structure and high reliability, as well as an improved tracking performance compared to that of PID control. In addition, AFOPID does not require an accurate PMSG model while only the measurement of d‐axis current and mechanical rotation speed is required, in which parameter is optimally tuned by particle swarm optimization. Four case studies are carried out, including step change of wind speed, low‐turbulence stochastic wind speed, high‐turbulence stochastic wind speed, and generator parameter uncertainties, respectively. Simulation results verify the effectiveness and superiority of AFOPID compared to that of PID, FOPID, and nonlinear control. [ABSTRACT FROM AUTHOR]