Phase Transposition Research Articles

Analysis of Increased Induced Voltages on the Sheath of Double-Circuit Underground Transmission Lines Guaranteeing Ampacity

This paper quantifies and discusses the increase in induced voltage on a sheath due to changes in duct banks in terms of type and dimensions along an underground transmission line, guaranteeing the ampacity required for a project. The four most common duct banks in double-circuit underground transmission lines with phase transposition were considered in this study, along with two special cross-bonding techniques: continuous cross-bonding (CCB) and sectionalized cross-bonding (SCB). These techniques aim to reduce sheath currents and enhance the distribution of the induced voltage on the sheath. The analysis considers two distinct scenarios in which the profile of the induced voltage is calculated: the first one accounts for underground obstructions, intersections with important traffic avenues, and ground with high excavation costs that force changes in the duct bank dimensions and configuration, which is the most exact and realistic case. The second one solely considers one typical configuration of a duct bank along the route. This last scenario is normally applied to calculate the induced voltage when an underground transmission design is required. The results show that when installing cables at a greater depth, it is imperative to increase the distance between them to guarantee the ampacity. The induced voltage on the sheath will rise as the distance increases. Furthermore, the results reveal that instead of calculating the induced voltage by considering the scenario that is exact and most like a real case, it is enough to calculate following the second scenario and then add a scaling factor according to each duct bank configuration.

Decoupled Control of a Multi-Machines System Fed by a Single Multilevel Inverter Six-Phase

The use of multiphase motors offers an additional possibility of independent control of a set of series-connected motors that are supplied from a single inverter.This paper presents independent vector control of six-phase two-motor drive machine series-connected fed by a seven-level six-phase inverter. Via appropriate phase transposition during the series connection of the stator windings, the fully decoupled control of the two machines is possible. The control system multi-machines classic based on vector control with conventional inverters comprise various problems are related to low power quality, pressure on motor bearing, etc. However, decoupling control of a series six-phase two-motor drive machine by a seven-level six-phase inverter is developed. A simulations result clearly shows the possibility of independent vector control of the two machines, although a single seven-level six-phase inverter is used as the supply.

Confined Co9S8 nanocrystals into N/S-Co-doped carbon nanofibers as a chainmail-like electrocatalyst for high-performance lithium-sulfur batteries with high sulfur loading

Accelerating phase transposition efficiency of lithium polysulfides (LiPSs) to L2S and hampering the solution of LiPSs are the keys to stabilizing lithium-sulfur (Li-S) batteries. Hence, the sulfiphilic ultrafine Co9S8 nanoparticles embedded lithiophilic N, S co-doping carbon nanofibers (Co9S8/NSCNF) are prepared via the dual-template method, which are then used as sulfur host in Li-S batteries. Particularly, the double active sites (Co9S8 and N, S) in Co9S8/NSCNF are prone to form “Co-S”, “Li-O” or “Li-N” bonds, and then simultaneously improving the chemisorption and interface transposition capability of LiPSs. In case of the S@ Co9S8/NSCNF composites with high sulfur loading of 89% are employed as cathode, the cell possesses optimized “sulfiphilicity” and “lithiophilicity”, which achieves remarkable sulfur electrochemistry, including outstanding reversibility of 816.8mAhg−1 over 500 cycles at 1.0C, excellent rate property of 742.2mAhg-1at 5.0C, and long-term cycling with a low attenuation of 0.011% per cycle over 1800 cycles at 3.0C. Impressively, a remarkable areal capacity of 11.51mAhcm−2 is retained under the sulfur loading of 15.3 mg cm−2 for 50 cycles. This research will deepen the understanding of the complex LiPSs interface transposition procedure and provide new ideas for the design of new host materials.

Optimal Determination Method of the Transposition Steps of An Extra-High Voltage Power Transmission Line

During the design of extra-high-voltage transmission lines, studies of the influence of asymmetry due to the phase difference of the parameters on its processes and the electrical network were performed. To compensate for this source of asymmetry for transmission lines longer than 100 km, a relatively simple technical means was proposed and implemented—phase transposition (change of the mutual location of phase wires in space). However, at the same time transposition causes additional capital costs in construction and reduces reliability during operation, so when designing a specific transmission line, extra-high-voltage is desirable to evaluate the effectiveness of the use of this measure in the real electricity network. Thus, under certain conditions, even for a transmission line 600 km in length, it was possible to perform either an incomplete transposition cycle, or abandon this measure altogether.

An Upper Bound on Magnitude Error of Voltage Drop Phasors in Distribution Lines Due to Phase Transposition Assumption

A renewed interest in comprehensive modeling of distribution system components arose in recent literature. This trend can be attributed to, aside from the inherent imbalance of such systems, the rapid and system-wide integration of technologies, e.g. non-linear loads and distributed generators, which further increase grid imbalance effects. Such phenomena, in turn, demand sufficiently detailed models for their proper assessment. Despite the described scenario, it remains reasonable to inquire whether approximate component models can still be used for simplifying computations without causing exceedingly high modeling error. In this context, an approximation of particular interest is assuming phase transposition for distribution lines, due to its property of impedance matrix decoupling on the symmetric component frame. In this paper, the derivation of a closed-form upper bound for voltage drop magnitude error, due to assuming transposition in a general M-phase line, is carried out. The bound is validated by means of a case study based on the IEEE 4-bus feeder considering generalized feeder geometries. Obtained results suggest that the upper bound is tight with respect to actual error and thus provides a practical means of estimating voltage drop error yielded by the assumption of distribution line transposition.

Y-shaped graphene-based antenna with switchable circular polarization

In this paper, an antenna with the ability to provide the right- and left-hand circular polarization in the THz band is presented. The central frequency of the antenna is set at 0.45 THz according to the proposal requirements. The antenna structure is designed to control its polarization rotation by adjusting the graphene conductivity with chemical potential changing. Two symmetric orthogonal arms of antenna are key point of proposed structure. By controlling the chemical potential of each arm, this capacity is created to control the conductivity of them. With this control, phase transposition between the two orthogonal arms is obtained. This precedence or delay of the phase is regulated by the chemical potential changes of the antenna arms, which results in a 90° phase difference between them. By moving the phase of each arm, two right- and left-hand circular polarization patterns is realized. In the frequency range of 0.42–0.48 THz the axial ratio less than 2.15 dB is reached in the antenna axis direction. Whereas the S11 is less than −12 dB for the aforementioned frequency range.

Analysis of load sharing capability of a series-connected twin synchronous motor drive coupled to a common load shaft by gearing

Torque limitations on gear teeth led to the use of two motors on opposite sides of the gear to drive large grinding mills. For such systems, motor overheating and rapid gear-teeth wear have been observed, especially when using synchronous motors due to load imbalance between the two motors. This paper studied a drive system consisting of two separate three-phase synchronous motors whose phase windings are split into two sections in a manner that makes them appear as six-winding machines, and then each of the resulting six windings of one motor are connected in series with those of the other motor, with no phase transposition, such that only three terminals of each motor are available to be connected to supply. The field windings are connected in parallel to the same source. Again, the motors, running on separate shafts, are connected to a common load shaft through a speed reduction gear driven through pinions. A detailed mathematical model is developed in the q-d axis, and the system is implemented on the MATLAB/ SIMULINK environment. A circumferential error in the girth gear was modeled to introduce load imbalance. It is observed that despite the load imbalance, the stator currents and the load torque seen by the two motors are the same. However, a variation is observed in their rotor angles. This suggests that while the motor units inherently share the mill load equally thereby removing the possibility of motor overheating, the varying rotor angle may represent a problem for the motor shafts. Keywords: Six-winding Machine, Synchronous Motors, Series-Connected, Common Load Shaft, Speed Reduction Gear, q-d Axis

A six-phase series-connected two-motor drive with decoupled dynamic control supplied by a three-level six-phase inverter

This paper presents independent vector control of six-phase two-motor drive machine series-connected fed by a three-level six-phase inverter. Via appropriate phase transposition during the series connection of the stator windings, the fully decoupled control of the two machines is possible. The control system multi machines classic based on vector control with conventional inverters comprise various problems are related to low power quality, pressure on motor bearing, etc. However, decoupling control of a series- six-phase two-motor drive machine by a three-level six-phase inverter is developed. A simulations results clearly shows the possibility of independent vector control of the two machines, although a single three-level six-phase inverter is used as the supply.

Extended Kalman Filter Based Sliding Mode Control of Parallel-Connected Two Five-Phase PMSM Drive System

This paper presents sliding mode control of sensor-less parallel-connected two five-phase permanent magnet synchronous machines (PMSMs) fed by a single five-leg inverter. For both machines, the rotor speeds and rotor positions as well as load torques are estimated by using Extended Kalman Filter (EKF) scheme. Fully decoupled control of both machines is possible via an appropriate phase transposition while connecting the stator windings parallel and employing proposed speed sensor-less method. In the resulting parallel-connected two-machine drive, the independent control of each machine in the group is achieved by controlling the stator currents and speed of each machine under vector control consideration. The effectiveness of the proposed Extended Kalman Filter in conjunction with the sliding mode control is confirmed through application of different load torques for wide speed range operation. Comparison between sliding mode control and PI control of the proposed two-motor drive is provided. The speed response shows a short rise time, an overshoot during reverse operation and settling times is 0.075 s when PI control is used. The speed response obtained by SMC is without overshoot and follows its reference and settling time is 0.028 s. Simulation results confirm that, in transient periods, sliding mode controller remarkably outperforms its counterpart PI controller.

The phase structure and electrical performance of the limited solid solution CuFeO2–CuAlO2 thermoelectric ceramics

The limited solid solutions of nominal (1 − x) CuFeO2 − xCuAlO2 have been prepared by conventional solid-state reaction, and thermoelectric property has been measured. From the XRD powder pattern, we found that the major phase of the limited solid solution is rhombohedral delafossite structure when the composition is near the end members. Cubic Cu(Fe,Al)2O4 phase has been formed in composition from x = 0.4 to 0.8. Electrical resistivity of samples with major delafossite structure is lower than that of samples with Cu(Fe,Al)2O4 phase. In the zone of phase transform, the electrical resistivity can be got with lower value, such as x = 0.2, 0.3 and 0.9. The Seebeck coefficient for the limited solid solution with delafossite structure is positive in whole measured temperature range from 300 to 923 K. In the end, the power factor for the limited solid solution with major delafossite structure shows higher value, which is resulted from the lower electrical resistivity by the phase transposition. The highest power factor of 1.14 × 10−4 W/mK2 has been addressed at 907 K for x = 0.2, which value is enhanced by 3–4 times than that of pure phase CuFeO2 or CuAlO2.

Effect of HVTL Phase Transposition on Pipelines Induced Voltage

In this work, a study of the effect of the phase conductor transposition for a multi-circuit high voltage power transmission lines on the induced voltage on a buried pipeline was conducted and considered through modelling. The modelling was done applying Carson’s concept of mutual impedances for a double circuit, three circuits and four circuit power transmission line on a buried pipeline. The simulated results obtained showed that the transmission line with un-transposed phase combination has the greater effect on the induced voltage while for the one or more of the other combinations, a cancellation or reduction can occur. This also is dependent on the tower geometry and the relative position of the pipeline and the transmission line. Also, the magnitude of the induced voltage increases with increasing number of circuits.

Study on Series Control Method for Dual Three-Phase PMSM based on Space Vector Pulse Width Modulation

Decoupling control of two-motor dual three-phase permanent-magnet synchronous motor (PMSM) series-connected system can be realized by using proper phase transposition rules with a single supply from a six-phase voltage source inverter (VSI), which solved the control problem of two motors in series. Since the traditional two-vector SVPWM strategy, which is commonly used in three-phase system, exists 5 th and 7 th harmonics in x-y plane, making it hard to realize decoupling control of two-motor dual three-phase PMSM series-connected system. Meanwhile, the DC bus voltage utilization of carrier-based PWM strategy is lower. Thus one method, which adopted a TBTSB-SVPWM strategy with two modulators, was proposed in this paper. It ensures the inverter output voltage only contains two kinds of fundamental components required by the two seriesconnected motors with a single VSI, making it possible to realize decoupling control of two-motor dual three-phase PMSM series-connected system. Simulation results indicate that there is no influence on the other motor while the speed/load of any one motor changed, achieving the decoupling control of series-connected system, and the feasibility and validness of the proposed approach are verified.

Full Decoupling Control of Two-Connected Motor Drives with Matrix Converter Supply

Multi-phase converters are required mainly for feeding variable speed multi-phase drive systems. This paper discusses one such solution by using direct ac-ac converter (matrix converter) that can be used to supply a six-phase and three-phase two-connected motor drive system. Matrix converter based two-motor drive system is presented for the first time in this paper. Two stator windings of six-phase and three-phase machines when connected in series while the rotors may be connected to different loads. Appropriate phase transposition is introduced while connecting the series stator winding to obtain decoupled control of the two machines. This paper proposes a scalar modulation scheme with three intervals technique of three-phase to six-phase matrix converter supplying series-connected six-phase and three-phase induction machine drive system. The dynamic decoupling of each machine from the group is obtained using the direct vector control algorithm. Mathematical modeling of the series-connected two-machine showed the possibility of independent control of each machine in the group. The independent control is demonstrated by analyzing the characteristics of the stator current references and speed of each machine under direct vector control scheme. The viability of the proposed control techniques is proved using analytically and simulation approach

Carrier-based pulse width modulation technique for a three-to-five phase matrix converter for supplying five-phase two-motor drives

Multi-phase (more than three-phase) converters are required mainly for feeding variable speed multi-phase drive systems. This paper discusses one such solution by using direct ac-ac converter that can be used to supply a five-phase two-motor drive system. Matrix converter based two-motor drive system is presented for the first time in this paper. Two stator windings of two five-phase machines when connected in seires/parallel while the rotors may be connected to different laods, are called series/parallelconnected two-motor drive. Appropriate phase transposition is introuduced while connecting the series/parallel stator winding to obtain decoupled control of the two machines. This paper proposes simple carrier-based Pulse width modulation (PWM) technique of three-phase to five-phase matrix converter supplying series-connected five-phase AC machine drive system. The developed modulation technique is based on the comparison of high frequency carrier signal with the input voltages, similar to the one used in voltage source inverter. Although carrier-based scheme is widely employed for control of voltage source inverter, it is very recently being used for a matrix converter. The similar concept is extended in this paper for controlling a three-phase to five-phase matrix converter. The major aim of the PWM is to generate two independent fundamental frequency components that will subsequently control two series/parallel connecetd five-phase motor. The viability of the proposed control techniques is proved using analytically and simulation approach. Keywords: Carrier-based PWM, Matrix converter, modulation, five-phase, AC machine, drive International Journal of Engineering, Science and Technology, Vol. 2, No. 10, 2010, pp. 67-78

Three-Level Five-Phase Space Vector PWM Inverter for a Two Five-Phase Series Connected Induction Machine Drive

This paper describes the decoupled torque and flux control of a two series connected five-phase Induction Machine (IM) drive that is supplied by a three-level five phase SVPWM inverter, using a well known phase transposition in the series connection. At the first, the decoupled torque and flux controller is developed based on variable-structure control (VSC). Then, a sliding-mode (SM) flux observer in employed to estimate the stator flux; that uses a two reference frames which result in eliminating the speed adaptation. Moreover simple control strategy is introduced for three-level SVPWM voltage source inverter (VSI) that can be easily implemented in practice for a two-series five phase IM drive. Finally, the effectiveness and capability of the proposed control method is verified by computer simulation.

Steady-State Modeling of Series-Connected Five-Phase and Six-Phase Two-Motor Drives

Two series-connected two-motor drive systems with a single inverter supply have been proposed recently. The first one consists of two five-phase machines supplied from a single five-phase inverter, whereas the second one comprises one symmetrical six-phase machine, a three-phase machine, and a single six-phase inverter. It has been verified experimentally that, by introducing an appropriate phase transposition in the series connection, completely independent dynamic control of the two machines can be realized using principles of vector control. Detailed dynamic models in the stationary common reference frame have also been reported for the two drive systems. These are taken here as the starting point, and equivalent circuit steady-state representation of the series-connected two-motor drive systems is developed. The equivalent circuits can then be used to evaluate steady-state characteristics of the drives in the same manner as it is done for three-phase induction machines, as well as for the inverter design. The dc-link voltage required for operation of the two series-connected machines is investigated next. It is shown that the specific winding connections lead to a dc voltage requirement that is smaller than it would have been had the windings of the two machines been connected directly in series. Experimental results, obtained during steady-state operation of the series-connected five-phase and six-phase two-motor drives, are presented. Developed equivalent circuit representation is finally verified by comparing calculated and experimentally obtained values for various voltages of the two-motor drives.

Analytical Determination of DC-Bus Utilization Limits in Multiphase VSI Supplied AC Drives

Two-level multiphase voltage source inverters (VSIs) are typically used as the supply for multiphase machines. Such machines are often with concentrated winding in which case, certain low-order stator current harmonics are injected to provide torque enhancement. Also, a multimotor drive system can be realized by connecting a number of multiphase machines in series, using phase transposition while supplying the whole system from a single multiphase VSI. In both situations, it is important to know the limits of the inverter operation in the linear modulation region. This paper develops a simple method that enables analytical determination of the boundaries of the linear modulation region for all multiphase inverters with a prime number of phases. The limits are independent of the actual pulse width modulation (PWM) method utilized, and are equally applicable to both carrier-based and space vector PWM techniques. Theoretical considerations are verified experimentally using the five-phase and seven-phase VSI rigs.

Modeling, Control, and Experimental Investigation of a Five-Phase Series-Connected Two-Motor Drive With Single Inverter Supply

This paper analyzes a recently introduced two-motor five-phase drive system with series connection of stator windings. It has been shown, using physical reasoning, that the introduction of an appropriate phase transposition in the series connection of two machines leads to a complete decoupling of the flux/torque-producing currents of one machine from the flux/torque-producing currents of the second machine. Consequently, independent vector control of the two machines becomes possible while using a single current-controlled five-phase voltage source inverter as the supply. The drive system modeling and control are first elaborated in this paper by taking both machines as induction motors. It is shown, using rigorous mathematical derivations, that the independent control of the two machines results due to the placement of machines in two different subspaces of the five-dimensional space. This is enabled by phase transposition in series connection. The models of the complete drive in the stationary common reference frame and in the rotor-flux-oriented reference frames of the two machines are developed. An associated vector control scheme for the two-motor drive is presented next. The second part of this paper describes an experimental setup used further on to evaluate the dynamic behavior of the two-motor drive. Performance is investigated by extensive experimentation for various transients (acceleration, deceleration, reversing, and disturbance rejection). Excellent decoupling of control of the two machines is achieved. Both the concept of the drive and the approach to modeling and control are thus fully verified experimentally. Finally, the advantages and shortcomings of the series-connected five-phase two-motor drive are discussed, and potential application areas are highlighted

Effective properties of two-phase mixtures

Expressions for the effective conductivity and resistivity of a two-phase medium that are represented as series based on Fourier transforms are analyzed. Relationships between the Fourier coefficients for the local conductivity and resistivity of transposed systems (obtained one from the other by phase transposition without changing the geometrical structure of the material) are derived. It is shown that such relationships allow, in a number of cases, calculating an arbitrary member of the series for the effective constants. A way of renormalizing all members of the series that makes it possible to relate the effective constants of transposed systems is demonstrated with a two-dimensional problem.

Negative Phase-Sequence Voltages on E&W Transmission System

In the absence of phase transposition, overhead lines are a major source of unbalance in both currents and voltages on the transmission system. In the England and Wales (E&W) transmission system, the individual circuits are phased such that the average unbalance produced is minimized. The main negative phase-sequence (NPS) voltages on the transmission system arise at loop-in points for generation and load connection under an outage condition of one of the connection circuits and where there is a large NPS voltage induction from the parallel circuit. If not limited, excessive unbalance can cause system incidents and lead to damage of power system equipment.