High Power Transfer Capability Research Articles

Investigation of the Transfer Capability of the Nigerian 330 kV, 58-bus Power System Network using FACTS Devices

Over the years, the Nigerian power system is beset with lingering problems, which include severe power losses, as well as very low transfer capability of the transmission network to evacuate power from generating stations to the load at the distribution level. Presently, the Nigerian power industry is undergoing restructuring, especially in the generation and distribution systems. In view of the deregulation of electricity distribution and marketing, the traditional practices of the Nigerian power system are undergoing changes to address the identified problems in the existing power system. Specifically, better utilization of the existing power transmission network to improve on the system transfer capability and minimize cost is one of the key focuses of the deregulation agenda. This work deals with the enhancement of transfer capability of Nigerian 58-bus, 330kV network using FACTS (Flexible Alternating Current Transmission System) devices. FACTS devices are used for controlling transmission voltage, power flow, reducing reactive power losses, and damping of power system oscillations for high power transfer capability. Three FACTS devices; Thyristor Controlled Series Compensator (TCSC), Unified Power Flow Controller (UPFC), and Interline Power Flow Controller (IPFC) were used to investigate the transfer capability of the Nigerian 58-bus power system network. NEPLAN was employed in this work to model the Nigerian 58-bus system and optimally placed the FACTS devices at the weakest buses that were found out through the computation for available transfer capability (ATC) after continuation power flow (CPF) simulation was completed. MATLAB codes were developed and used to calculate power transfer capability of the network without and with FACTS devices. Comparing the three FACTS devices, the results obtained showed that UPFC enhanced the power transfer capability of the network than TCSC and IPFC.

Highly Efficient Full-Bridge Resonant AC/DC Converter Using T-Type Voltage Doubler

This article presents full-bridge resonant ac/dc converter that minimizes switching loss over entire grid voltage cycle. By using the voltage fluctuation at T-type voltage doubler, the existing hard-switched components are turned- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> with almost zero-voltage switching at high instantaneous output power and with less than half of the output voltage at low instantaneous output power. Moreover, no instantaneous reactive current flows through the circuit under wide variations of grid voltages and loads. Furthermore, the proposed converter has balanced loss distribution over the primary-side and secondary-side switches, which ensures high power transfer capability with improved overall switch utilization. A 1-kW prototype is developed and tested to demonstrate the circuit functionality. Finally, the efficiency improvement is investigated; comparisons show the benefit of the proposed converter over conventional converters that use unfolders.

A Single-Ended Hybrid Resonant Converter With High Misalignment Tolerance

This article proposes a single-ended hybrid resonant converter (SEHRC) for wireless charger to provide a cost-effective solution with high misalignment tolerance. A comprehensive characteristics analysis of the proposed converter is performed in both of time and frequency domain. The analysis discloses that the hybrid compensation performs impedance transformation which maintains the input impedance nearly constant. As a result, the optimum operation of SEHRC, including zero-voltage-switching, low voltage stress, high power transfer capability, and high efficiency can be maintained within a wide range of coupling coefficients. Also, it ensures a stable output current for both load and coupling variations. The design constraints and procedure are given. Furthermore, a zero-voltage-switching and zero-voltage-derivative-switching control scheme is proposed to achieve a higher efficiency and smaller output current fluctuation, as well as reduced peak switch voltage. Finally, a 1.3 kW prototype is built to verify the theoretical analysis. The test results demonstrate that the peak voltage of the proposed SEHRC is less than 2.7 times the input voltage. When the coupling coefficient varies 2.7 times, the output current changes by 1.16 times.

A Power Factor Correction LED Driver With Direct Power Transfer Feature

This article presents an isolated bridgeless single-stage light-emitting diode (LED) driver with high power factor, soft-switching performance, and direct power transfer (DPT) capability. In the proposed circuit topology, a bridgeless boost power factor corrector (PFC) is integrated with an isolated current-driven half-bridge dc/dc converter to achieve a bridgeless single-stage PFC structure. Besides, a direct path is provided using coupled inductors to directly transfer power from the input source to the output. The bridgeless structure and DPT capability result in reduced conduction losses, while the soft-switching operation almost eliminates the switching losses. Therefore, the proposed LED driver benefits from low losses and high efficiency. The proposed LED driver is theoretically analyzed. Also, experimental results for a 150-W prototype supplied from a 120-V/60-Hz utility are presented to verify its performance.

Optimal Solutions for Underwater Capacitive Power Transfer.

Capacitive power transfer (CPT) has attracted attention for on-road electric vehicles, autonomous underwater vehicles, and electric ships charging applications. High power transfer capability and high efficiency are the main requirements of a CPT system. This paper proposes three possible solutions to achieve maximum efficiency, maximum power, or conjugate-matching. Each solution expresses the available load power and the efficiency of the CPT system as functions of capacitive coupling parameters and derives the required admittance of the load and the source. The experimental results demonstrated that the available power and the efficiency decrease by the increasing of the frequency from 300 kHz to 1 MHz and the separation distance change from 100 to 300 mm. The maximum efficiency solution gives 83% at 300 kHz and a distance of 100 mm, while the maximum power solution gives the maximum normalized power of 0.994 at the same frequency and distance. The CPT system can provide a good solution to charge electric ships and underwater vehicles over a wide separation distance and low-frequency ranges.

Bridgeless Push–Pull Resonant AC/DC Converter Featuring Balanced Switching Loss Distribution

This article proposes a bridgeless push–pull resonant ac–dc converter featuring naturally balanced switching loss at the primary side. The proposed converter employs a current-fed push–pull structure and two rectifier diodes at the primary side and a series resonance circuit at the secondary side. By incorporating two rectifier diodes, a diode bridge can be removed from the grid side of the proposed converter, and thereby that the number of components and primary-side conduction loss are reduced. One major advantage of the proposed converter is balanced loss distribution over one cycle of grid voltage, which guarantees high power transfer capability with enhanced overall switch utilization. The series-resonant circuit provides zero-current switching turn- off at the output diode, thereby reducing the reverse recovery loss. The operating principles and theoretical derivations of the converter are discussed in detail. The validity and performance of the proposed converter are verified using a prototype with 1.65 kW output power.

Analysis of Six-Phase Transmission Lines for Increasing Power

In the India, especially in metropolitan areas, transmission infrastructure is congested due to a combination of increasing load demands, declining investment, and aging facilities. It is anticipated that significant investments will be required for new construction and upgrades in order to serve load demands. This paper explores higher phase order systems, specifically, six-phase, as a means of increasing power transfer capability, and provides a comparison with conventional three-phase double circuit transmission lines. Line parameters calculations performed in this thesis show that line impedances in six-phase lines have a slight difference, compared to three-phase double circuit line. The electric and magnetic fields calculations show that, ground level electric fields of the six-phase lines decline more rapidly as the distance from center of the lines increase. The six-phase lines have a better performance on ground level magnetic field. Based on the electric and magnetic field results, right of way requirements for the six-phase lines and three-phase double circuit line were calculated. The calculation results of right of way show that six-phase lines provide higher power transfer capability with a given right of way.

Proposing and Evaluation of SC Techniques for Variable Speed High-Power Operation of SEIG

This work presents a novel methodology for variable speed high power Transfer Capability of a self-excited induction generator (SEIG). The proposed methodology is based on the selection of a suitable firing angle of Fixed Capacitor-Thyristor Controlled Reactor (FC-TCR) for achieving constant rated stator current. WDSEIG would produce a variable speed high power without overheating under variable wind speed and connected load. The analytical approach for the proposed methodology has been implemented to predict the optimal operating firing angle of FC-TCR for full load stator current achievement within the allowed operating range of load and prime mover speed. Also, Soft Computing (SC) techniques have been implemented based on Harmony Search Algorithm (HSA), Flower Pollination Algorithm (FPA), and Moth-Flame Optimization (MFO) algorithm to achieve the proposed methodology. A comparison between different SC techniques, analytical approach and experimental work are given and evaluated to verify SC techniques accuracy. This evaluation study can be useful in specifying the appropriateness of the SC techniques for High Power Transfer Capability for a SEIG.

Phase-Shift Modulation for a Current-Fed Isolated DC–DC Converter in More Electric Aircrafts

This paper discussed an active-bridge-active-clamp (ABAC) topology that is suitable for highpower more-electric-aircraft applications. Though conventional modulation techniques can be applied to ABAC converters, they present drawbacks, such as increased low-voltage (LV) current ripple and limited power transfer capability. To address these problems, a phase-shift-modulation (PSM) scheme is proposed to provide clean dc terminal current at the LV side while maintaining high power transfer capability and efficiency in a wide operating range. The proposed PSM has a complete switching harmonics cancellation on the LV terminals independent of the operating conditions. This results in high quality power without any ac components, thus minimizing passive filtering. In addition, when terminal voltages vary from their nominal values, the proposed PSM can improve the maximum power transfer capability of the ABAC converter compared to the conventional approach. The theoretical claims are validated by both simulation and experimental results on a 10-kW 270-V/28-V ABAC converter.

Proposed control policy for high power transfer capability DFIG

This paper aims to extract maximum power from wind turbine at all permissible wind speed range while minimizing the total copper loss of the doubly fed induction generator (DFIG) simultaneously. A proposed steady state model is presented whereby unity rotor power factor (URPF) of the DFIG and wind-turbine MPPT variables are the state variables. The URPF proposed variable is the load angle (α) by which the generator performance characteristics can be controlled over the whole operating speed range. Comparison of URPF with conventional operation is given. This comparison illustrate and evaluate the generator performance characteristics at URPF operation up two twice synchronous speed. An analytical approach has been implemented to predict the optimal load angle and the speed dependent rotor voltage magnitude that insure MPPT at URPF. This speed dependent rotor voltage magnitude may be burnt into the EPROM of the digital reference generator provided by a rotor side converter in DSP system. Experimental results are given to strongly validate the proposed technique. Results have shown the DFIG as high power transfer capability (HPTC) transducer.

The Recognition and Control of Nonideal Soft-Switching Frequency for Wireless Power Transfer System Based on Waveform Identification

Nonideal frequency problems can occur in a wireless power transfer system due to multiple soft-switching frequencies and frequency bifurcation. To make the system work at an ideal frequency with high-power transfer capability and efficiency, a method based on waveform identification is proposed. First, the space state model of a SP type WPT system is built, and the waveforms at ideal and nonideal working frequencies are obtained based on the stroboscopic mapping theory. Second, according to the characteristics of these waveforms, the swing door algorithm is improved by waveform distortion rate and fast Fourier transformation, which is used to recognize nonideal waveforms. Then, a control strategy based on “online self-determined optimization” is proposed to deal with the problem. Finally, the results of simulation and experiments show that the method proposed in this paper can identify the waveforms at nonideal frequency and find an ideal working frequency for the WPT system.