This review aims to provide an up-to-date, comprehensive, and systematic summary of fault detection and diagnosis (FDD) in building systems. The latter was performed through a defined systematic methodology with the final selection of 221 studies. This review provides insights into four topics: (1) glossary framework of the FDD processes; (2) a classification scheme using energy system terminologies as the starting point; (3) the data, code, and performance evaluation metrics used in the reviewed literature; and (4) future research outlooks. FDD is a known and well-developed field in the aerospace, energy, and automotive sector. Nevertheless, this study found that FDD for building systems is still at an early stage worldwide. This was evident through the ongoing development of algorithms for detecting and diagnosing faults in building systems and the inconsistent use of the terminologies and definitions. In addition, there was an apparent lack of data statements in the reviewed article... [more]

The growing penetration of renewable resources such as wind and solar into the electric power grid through power electronic inverters is challenging grid protection. Due to the advanced inverter control algorithms, the inverter-based resources present fault responses different from conventional generators, which can fundamentally affect the way that the power grid is protected. This paper studied solar inverter dynamics focused on negative-sequence quantities during the restoration period following a grid disturbance by using a real-time digital simulator. It was found that solar inverters can act as negative-sequence sources to inject negative-sequence currents into the grid during the restoration period. The negative-sequence current can be affected by different operating conditions such as the number of inverters in service, grid strength, and grid fault types. Such negative-sequence responses can adversely impact the performance of protection schemes based on negative-sequence comp... [more]

With the continuous improvement of automatization of underground oil and gas resources exploitation, more and more instructions are required for the control technology while drilling in complex processes. The conventional downlink communication technology has shortcomings, such as data transmission lag and high bit error rate, which cannot meet the actual needs. Therefore, developing a new high-speed and low bit error rate (BER) downlink communication technology is very important. In this study, a new type of downlink communication system based on the electric current field is designed. Firstly, based on the theory of electromagnetic field and electromagnetic wave, the current distribution model of the drill string is established. Then, the magnetic field distribution model of the drill string is deduced according to the research on the static electromagnetic field and boundary problems. Finally, the ground simulation experiment platform of the downlink communication system is built an... [more]

The deployment of a 765-kV transmission line on Eskom’s South African Grid marks the beginning of a new era in power industries. The integration of renewable energies by independent power producers (IPPs) leads to an infrastructural change in the stability performance of the entire grid. These developments are expected to bring about a multiterminal direct current (MTDC) system for practical implementation on this grid. Therefore, this study focuses on the dynamic response of the South African transmission grid during a system disturbance. In the carrying out of this study, the South African grid was modeled on PSCAD, and its performance was evaluated. The impact of the MTDC link on the grid’s interarea oscillation was also investigated. An additional current order controller for the MTDC link was developed, and its impact on the MTDC power transfer was analyzed. The results show a better system performance and reduced interarea power swings with the inclusion of the MTDC link.

For deep-buried thick top-coal roadways under high stress, there exists great difficulty in controlling the stability of the surrounding rock as well as in the necessity for low driving speeds. Taking the return air roadway 20201 (RAR 20201) of the Dahaize Coal Mine as the background, this paper presents a typical engineering case of a deep-buried thick top-coal roadway in a western mine. Through methods such as in situ investigation, theoretical analysis, numerical simulation and engineering practice, we studied the deformation and failure mechanisms of the surrounding rock in a deep-buried high-stress thick top-coal roadway, and revealed the driving speed effect. Results show that compared with shallow buried roadways, the deep-buried thick-roof coal roadway suffers a greater range of damage and failure. The roof damage is so deep that it exceeds the action range of bolts, resulting in the stress transferring to both sides, which affects the stability of the roadway surroundings. The... [more]

An in-depth study of harmonic current reduction in European commercial buildings due to the harmonic cancellation effect when a set of single-phase uncontrolled rectifiers and a set of fluorescent lamps are connected at the same voltage level is essential, since both types of non-linear loads are very present in commercial and residential sectors. This paper provides an appropriate index to assess the global cancellation level of the harmonic currents for this study. The equivalent circuit per phase of the typical three-phase power system of European commercial installations is presented and simplified for the cancellation analysis of the harmonic currents consumed by a set of multiple identical single-phase uncontrolled rectifiers and a set of multiple identical fluorescent lamps connected at the same voltage level. The suitability and usefulness of the proposed index are shown by applying it to that analysis, which leads to some results of practical interest. This index can be genera... [more]

In the paper, a new cascade control system for an autonomous flight of an unmanned aerial vehicle (UAV) based on Proportional−Integral−Derivative (PID) and finite-time State-Dependent Riccati Equation (SDRE) control is proposed. The PID and SDRE controllers are used in a hybrid control system for precise control and stabilization, which is necessary to increase the drone’s flight stability and maneuver precision. The hybrid PID-SDRE control system proposed for the quadrotor model is quasi-optimal, since the suboptimal control algorithm for the UAV stabilization is used. The combination of the advantages of PID and SDRE control gives a significant improvement in the quality of control while maintaining the simplicity of the control system. Furthermore, the use of the suboptimal control technique provides the UAV attitude tracking in finite time. These remarks are drawn from a series of simulation tests conducted for the drone model.

The Ledong submarine channel and the Dongfang submarine fan, two remarkable sedimentary systems developed during the late Miocene, are considered promising hydrocarbon reservoirs in the Yinggehai Basin of the South China Sea. A comparative study was conducted to reveal the differences between the source-to-sink characteristics of the two gas-bearing and gravity-driven depositional systems to determine their provenances, formation mechanisms and migration paths as well as their key controlling factors. The heavy mineral assemblages and detrital zircon U-Pb dating results suggest that the Ledong channel was fed by the Hainan provenance from the eastern margin, whereas the Dongfang fan was supplied by northwestern terrigenous sources. The relative sea level transgression and sufficient sediment supply triggered the delivery of deltaic loads toward the continental shelves. Seismic data show that fracture activity had a great impact on the tectono-morphologic features of the margins. During... [more]

Helical gears are widely used in powertrain systems. The computerized design of a new type of non-generated external helical gears based on critical control points at the transverse tooth profile is presented. The entire tooth profile is divided into different parts including the active tooth profile and fillet by control points. Involutes, circular arcs and Hermite curves are defined between two critical control points and smoothly connected with each other at those control points. The parametric equations for the tooth surfaces are derived considering the position of the mentioned control points. The basic design parameters and equations of the geometric sizing are proposed. The contact patterns, variation of the maximum stresses and peak-to-peak level of loaded transmission errors for six cases of design of the proposed new geometry of helical gear drives are studied with two cases of traditional helical gear drives as a reference, including gears with and without micro-geometry mod... [more]

The migration and accumulation of oil in tight sandstone reservoirs are mainly controlled by capillary force. Due to the small pore radius and complex pore structure of tight sandstone reservoirs, the capillary force is very sensitive to wettability, so wettability significantly affects oil migration and accumulation. However, the study of oil migration and accumulation in tight sandstone reservoirs often needs to combine multiple methods, the process is complex, and the research methods of wettability are not uniform, so the mechanism of wettability affecting oil migration and accumulation is not clear. Taking the tight sandstone of the Shahejie Formation in the Dongying sag, Bohai Bay Basin, as the research object, the wettability characteristics of a tight sandstone reservoir and their influence on oil migration and accumulation were analyzed by means of a pore permeability test, XRD analysis, micro-CT experiment, contact angle tests, spontaneous imbibition experiments, and physical... [more]

The investigation of the shale oil development potential of the lower third section−upper fourth section (ES33−ES41) of the Eocene−Oligocene Shahejie Formation in the Dongying Sag, Bohai Bay Basin, eastern China, continues to be a scientific challenge. A total of 23 shale samples was collected from these strata, and the organic petrology, organic geochemistry, mineral composition, porosity, and pore structure of these samples and their relationships with the retained oils were investigated. The results indicated that these shales with type I−IIa kerogen are rich in lamalginite and its debris, and the Ro values of these shales range from 0.70% to 1.00%. The non-micropores (>2 nm) that are mainly developed from inorganic minerals are greater than the micropores ( 0.90%), and the siltstone or carbonate rock interlayer, especially with laminated or layered textures, will further control the sweet spot intervals of shale oil. This study provides new geological evidence for revealing the ret... [more]

This scientific paper aims to increase the voltage source converter (VSC) control efficiency in a multi-terminal high voltage direct current (MTDC) network during dynamic operations. In the proposed study, the Mayfly algorithm (MA) is used to modify the control parameters of VSC stations. Traditional strategies that modify VSC control settings using approximate linear models fail to produce optimal results because VSCs are nonlinear characteristics of the MTDC system. Particle swarm optimization (PSO) may produce optimal outcomes, but it is prone to becoming stuck in a local optimum. To modify the proportional-integral (P.I.) control parameters of the VSC station, the Mayfly algorithm, a modified form of PSO, is used. The suggested algorithm’s objective function simultaneously optimizes both the outer and inner control layers. A four-terminal MTDC test system is developed in PSCAD/EMTDC to assess the benefits of the proposed algorithm. For VSCs, a comparison of classical, PSO, and prop... [more]

There is tremendous potential in solar energy to meet future electricity demands. Partial shading (PS) and drift are two major problems that must be addressed simultaneously to achieve the maximum power point (MPP) of a stand-alone PV system, which are discussed in this paper. Both of these factors contribute to the voltage drop due to heavy steady-state oscillation. The partial shading and drift problem are associated with severe rapid changes in the insolation. A modified drift-control perturbation and observation DC-(P&O) approach was investigated using a low-cost programmable hardware solution, i.e., the ARM Cortex M4 32-bit Microcontroller (MC) (STM32F407VGT6), with efficient embedded programming and Waijung block sets for real-time solutions. The experimental setup was accomplished on a 40-watt solar panel. It was found that the proposed method had a significant impact on drift control during abrupt changes in current and voltage caused by shading effects, with the controller con... [more]

This article deals with the issue of the reduction of the oscillation of electromagnetic torque in the case of a direct on line (DOL) starting of a 6 kV induction motor. Such engines are used in drive systems where frequent starting may be required. Direct starting in such systems may reduce the mechanical and thermal durability. Therefore, the article presents a method of DOL starting of a 6 kV induction motor with the use of vacuum circuit-breakers and appropriate switching of the voltages supplying the electric machine. To confirm the advantages of the proposed solution, computer simulation and experimental tests were carried out, which are presented and discussed in the article. The obtained results confirm the advantages of the proposed solution, compared to the classic starting known from the literature.

This paper presents a method for supplying stable electricity using renewable energy sources and energy storage systems (ESSs) in a small-scale microgrid (MG) such as an island. Traditional control methods, such as master−slave control and droop control, have focused on equalizing power sharing among a small number of generators and do not deal well with emergencies such as unplanned generator failures. This paper proposes a control method that can stably maintain the frequency of the MG in various situations by combining the advantages of master−slave control and droop control and complementing the disadvantages. Simulations were performed under various conditions to verify the proposed control method.

Low-latency communication is becoming more popular as applications that demand real-time interaction, such as autonomous mobile vehicles and tactile Internet, have recently gained prominence. In this paper, we propose a fast autotuning algorithm to support low-latency communication in the Quick UDP Internet Connection (QUIC) protocol. The transmission rate is adjusted by the fast autotuning based on the quantity of unused buffers. If the buffer has large free space, the receive window is quickly enlarged to increase the transmission rate and reduce the transmission delay. The fast autotuning is evaluated in this paper through extensive simulations, and the results show that the fast autotuning effectively reduces the transmission latency and increases throughput.

This paper studies load frequency control (LFC) for networked power systems with limited communications and probabilistic cyber attacks. Some restrictions exist during the information transmission, which can impair behavior and lead to instability of power systems. Throughout this paper, we consider such power systems that involve multi-path missing measurements and input−output time-varying delays as well as cyber attacks in the communication channels. A feedback controller is presented, which is based on the observer to implement H∞ LFC for power systems with disturbance rejection level γ. By Lyapunov stability theory, adequate criteria are given to ensure the stable operation of power systems. Finally, the validity of theoretical analysis is demonstrated and illustrated by numerical simulations.

In this article, a topology based on the single-phase full-bridge is proposed to decouple control of phase current in current source grid-connected inverters. The DC side of this current source inverter topology can operate with a common DC bus or independently, and the AC side can be independently integrated into the three-phase grid or operate in parallel. This topology needs only a simple control logic and phase information to achieve 3-phase current decoupling control, which can accommodate a wide range of voltage fluctuations. Then, dual-carrier driving and hybrid damping correction strategies are designed to achieve flexible combinatorial operation and eliminate the common-mode voltage. Meanwhile, the method is simple and easy to implement in practice. The effectiveness of the proposed algorithm is validated with experiments.

Real-time monitoring devices are popularly utilized in modern power grids. To ensure long-term operations of the monitoring systems under complex outdoor conditions, a reliable and stable power supply is essential. In this paper, a general analysis of domino wireless power transfer (WPT) systems with load-independent outputs is proposed to realize a constant power supply for the monitoring equipment. In addition, the methodology of analyzing the self-oscillating points of the proposed domino WPT systems is deduced. The availability and feasibility of the proposed analysis and control method are verified by both simulation and experiment results based on a four-coil WPT system.

This article proposes a method to modify the construction of a medium voltage (MV) heat shrinkable cable termination in cases of atypical damage to the shields of cross-linked polyethylene (XLPE) insulated cables. The proposed solutions include a modified method of assembling electric field control coating. An attempt was made to check the effect of such damage to the shields of MV cables with XLPE insulation on the level of occurrence of partial discharges within the cable termination. The investigations included testing the XRUHAKXS 1 × 240/25 cable type using the electric method (ME) and high frequency (HF) method with sinusoidal AC test voltage. As a result of the measurements, the values of total charges in the period and phase-resolved partial discharge (PRPD) patterns were obtained. The presented experimental results show the influence of the damage of the semiconducting coating surface on the occurrence of a defect in the cable termination without a modified method of control m... [more]

An experimental determination of optimal performance of a steam ejector refrigerator was proposed which aims to indicate the optimal performance under various heat source temperatures. A small-scale steam ejector refrigerator test bench was constructed to carry out the experiment and to determine the optimal performance map. Three primary nozzles with throat diameters of 1.4, 1.6, and 1.8 mm, were tested with an ejector throat diameter of 14.5 mm, providing the ejector area ratios of 107, 82, and 65, respectively. For a particular working condition, the boiler temperature was varied to determine the maximum COP which is recognized as the optimal operation. It was found that the secondary fluid stream is first choked at the optimal boiler temperature. This optimal point varied significantly with the evaporator temperature, condenser pressure, and ejector area ratios. It was found that this steam ejector refrigerator could be operated under the optimal boiler temperature between 102.5 an... [more]

The recent research in the field of electrical and autonomous vehicles is developing in exciting directions [...]

The traditional DGA (Dissolved Gas Analysis) diagnosis method does not consider the dependence between fault characteristic gases and uses the relationship between gas ratio coding and fault type to make the decision. As a tool of the dependence mechanism between variables, a copula function can effectively analyze the correlation between variables when it cannot determine whether the linear correlation coefficient can correctly measure the correlation between variable relationships. In this paper, the edge variable of a copula function is selected from the fault characteristic gas of a transformer, and the distribution type of the edge variable is fitted at the same time. Then, Bayesian estimation with the Gaussian residual likelihood function is used to fit the parameters of a copula function and a copula function is selected to describe the optimal dependence of the fault characteristic gas of transformer. The relationship between a copula function and the state of transformer is st... [more]

Shading facilities are important technology to enable the adjustment of the indoor light and heat environment, and the control logic of the technology relies on data collected by sensors. The sensor position is generally arranged on the work surface, which is only suitable for single rooms with fixed locations. For open-plan offices or other large offices, more study of detailed designs for the sensor position is required. Therefore, various sensor locations for different spaces will be investigated. Based on existing research, the UDI2000 lux [50%] and UDI450−2000 lux [50%] are the key indices for measuring sensor location. The Entropy Weight method is used to determine the weight of each index, and the ideal point method (TOPSIS method) is used to select the best sensor location. Based on the results, recommendations are provided for different space scales, window-to-wall ratios, and building orientations of offices for shading control sensor location.

With the ambition of achieving carbon neutrality worldwide, renewable energy is flourishing. However, due to the inherent uncertainties and intermittence, operation flexibility of controllable systems is critical to accommodate renewables. Existing studies mainly focus on improving the flexibility of conventional plants, while no attention has been paid to the flexible operation of concentrating solar power with thermal energy storage (CSP-TES) systems. To this end, the ultimate goal of this work is to investigate the potentiality and realization of CSP-TES systems to flexibly operate in grid system regulation. With this goal, the dynamic characteristics of a 50 MW parabolic trough collector CSP plant with molten-salt-based TES is analyzed, and its dominant control characteristics are concluded to demonstrate the possibility of the ideal. After that, a coordinated control strategy is proposed. Specifically, a disturbance observer-based feedforward−feedback control scheme and a feedforw... [more]