Sliding-Mode Perturbation Observer-Based Sliding-Mode Control for VSC-HVDC Systems

This chapter develops a sliding-mode perturbation observer-based sliding-mode control (POSMC) scheme for voltage source converter-based high voltage direct current (VSC-HVDC) systems. The combinatorial effect of nonlinearities, parameter uncertainties, unmodeled dynamics, and time-varying external disturbances is aggregated into a perturbation, which is estimated online by a sliding-mode state and perturbation observer (SMSPO). POSMC does not require an accurate VSC-HVDC system model and only the reactive power and DC voltage at the rectifier side while reactive and active powers at the inverter side need to be measured. Additionally, a considerable robustness can be provided through the real-time compensation of the perturbation, in which the upper bound of perturbation is replaced by the real-time estimation of the perturbation, such that the over-conservativeness of conventional sliding-mode control (SMC) can be effectively reduced. Four case studies are carried out on the VSC-HVDC system, such as active and reactive power tracking, AC bus fault, system parameter uncertainties, and weak AC gird connection. Simulation results verify its advantages over vector control and feedback linearization sliding-mode control. Then, a dSPACE-based hardware-in-the-loop (HIL) test is undertaken to validate the implementation feasibility of the proposed approach

A critical survey of power take-off systems based wave energy converters: Summaries, advances, and perspectives

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

Fault Model and Travelling Wave Matching Based Single Terminal Fault Location Algorithm for T-Connection Transmission Line: A Yunnan Power Grid Study

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

Voltage Distribution–Based Fault Location for Half-Wavelength Transmission Line with Large-Scale Wind Power Integration in China

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

A critical survey of proton exchange membrane fuel cell system control : summaries, advances, and perspectives

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