Search

Traditional single-circuit high-voltage AC lines, widely used throughout the world, are characterized by a significant disadvantage, which is that when the most probable single-phase permanent failures occur, the line is completely disconnected. This article discusses single-circuit high-voltage lines, one phase of which is built in the form of two parallel operating semi-phases, either of which is used as a backup phase in failure modes, and series capacitors are included at the ends of the line in two normal phases for mode symmetry. An algorithm has been developed for calculating normal modes. Using the example of the proposed 110 and 220 kV innovative lines, the relation between their capacity and the capacity of two-circuit traditional lines is shown. A scheme is proposed that makes it possible, in case of permanent damage to one of the semi-phases or one of the phases, to switch to operation in post-failure mode with the possibility of transmitting at least 50% of the power of the initial maximum mode. A technical and economic comparison of two-circuit traditional and single-circuit 110 and 220 kV innovative lines was carried out. [ABSTRACT FROM AUTHOR]

The optimal size and location of series capacitors is a critical challenge in a distribution network. In this paper, a novel approach for enhancing voltage stability in distribution networks through the optimal sizing and placement of series capacitors is proposed. The study introduces a technique to determine the optimal lines for connecting series capacitors based on line reactance and current. A Modified Elephant Herding Optimization (MEHO) algorithm was used to determine the reactance sizes of the series capacitors and the best lines to place them for optimum system performance. To evaluate the effectiveness of the proposed method, three series capacitors are placed and sized in the standard IEEE 33-bus radial distribution system for stability enhancement. A comparison is conducted between the proposed MEHO algorithm-based approach, the original Elephant Herding Optimization (EHO) algorithm, and the IGWO-TS-based methods reported in the literature. The evaluation is performed by analyzing the system voltage profile, total system losses, and system voltage deviation index under varying loading conditions of 30%, 100%, and 120% of the system nominal loading. Results demonstrate that the proposed MEHO algorithm-based approach outperforms the other two methods significantly in all the scenarios, highlighting its effectiveness in voltage stability enhancement in distribution networks. [ABSTRACT FROM AUTHOR]

Summary: Lossless LC ladder networks have many applications. But at high frequencies, inductor‐free designs are preferred since inductors are heavy and have limited values. An additional reason for not using the inductors (at high frequencies) consists in that the values of very small inductors could be quite imprecise. If LC ladder network is high‐pass type, then parallel inductors must be removed. The resulting network will have only series capacitors, which can be combined as a single series capacitor. But if commensurate transmission lines separate the series capacitors, a high‐pass mixed element network is obtained. In this paper, a procedure is proposed to compute the values of series capacitors and characteristic impedances of the transmission lines in the mixed element ladder network. The usage of the procedure is explained by means of the given example. [ABSTRACT FROM AUTHOR]

In this work, high-pass mixed-element networks with series capacitors separated by unit elements are analyzed. First, the description of the networks via two frequency variables is given. Then, explicit coefficient relations for the descriptive polynomials are derived in terms of the single-variable boundary polynomial coefficients. Finally, the derived relations are used to design a high-pass mixed-element matching network. The series capacitors can be converted to short-ended stubs by means of Richard's transformation. Thus, the obtained network is suitable for microstrip production. [ABSTRACT FROM AUTHOR]

The occurrence of unstable subsynchronous control interaction (SSCI) between wind farms and series‐compensated networks poses a considerable threat to the safety of power system. Different from the conventional eigenvalue analysis and Nyquist method, the black‐box‐model based RLC fitting technique becomes more attractive for the assessment of the SSCI risk. However, the method has merely been verified by radial networks whose SSCI mode can be well explained by an RLC circuit. A practical wind power system, however, can be meshed networks comprising multiple geographically distributed wind farms and series capacitors. Thus, it is questionable whether the application of the RLC fitting technique to such systems can still yield a sufficient accuracy. To clarify this aspect, in this work, the performance of RLC fitting in various test systems was examined. The results indicated that the aggregation technique considerably influences the accuracy of the assessment, and the RLC fitting cannot be applied when multiple series capacitors are involved in the SSCI mode. To address this problem, a more advanced frequency‐domain fitting technique known as vector fitting was adopted, and its robustness and effectiveness were verified considering a modified The Electric Reliability Council of Texas (ERCOT) system. [ABSTRACT FROM AUTHOR]

In this paper, a new nonisolated high step-down dc–dc converter with ultrahigh step-down conversion ratio is proposed. Advantages of the proposed converter are high step-down ratio, extended duty cycle, reduced switching losses by a converter operation under zero-voltage switching (ZVS) conditions, reduced reverse reco-very losses of diodes by achieved zero-current switching turn-off condition, and reduced voltage spikes by the inherent active-clamping structure of the converter. In this converter, series capacitors and coupled inductors have been used in power path to achieve the low voltage gain and extended duty cycle. By the inherent active-clamping structure of the proposed converter, the leakage inductance energy is totally recovered in the output; therefore, the high voltage spike across the semiconductor devices is suppressed. The switches of the proposed converter can operate under ZVS conditions, which cause reduced switching losses and improved efficiency. In this paper, the converter operating modes are discussed, and a prototype circuit is implemented. Experimental results are presented to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, the performances of one-ended and two-ended traveling wave (TW)-based fault location techniques in series compensated transmission lines (SCTLs) are thoroughly investigated, highlighting the impact of the series capacitors (SCs) and their associated overvoltage protection on such routines. To do so, a diversity of fault simulations were carried out on a realistic Alternative Transients Program (ATP) power system model of a 500 kV/60 Hz double-circuit SCTL located in the north region of Brazil. From the carried out studies, it is demonstrated that the two-ended algorithm is not impacted when the SCs are installed at the line ends, but the single-ended routines based on correlation functions are more affected by the SCs banks, even though some promising results may be obtained depending on their adjustments. • Novel sensitivity analyses of TW-based functions on series-compensated lines. • Investigation on the performance of one- and two-ended TW-based fault locators. • Analysis considering a realistic power system model with SCs, SVCs, DC lines etc. • Points out the need of new adjustments for one-ended applications in SCTLs. • Addresses the challenges and viability of using TW-based fault locators in SCTLs. [ABSTRACT FROM AUTHOR]

The distribution static compensator (DSTATCOM) is used for load compensation in power distribution network. In this paper, a new topology for DSTATCOM applications with nonstiff source is proposed. The proposed topology enables DSTATCOM to have a reduced dc-link voltage without compromising the compensation capability. It uses a series capacitor along with the interfacing inductor and a shunt filter capacitor. With the reduction in dc-link voltage, the average switching frequency of the insulated gate bipolar transistor switches of the DSTATCOM is also reduced. Consequently, the switching losses in the inverter are reduced. Detailed design aspects of the series and shunt capacitors are discussed in this paper. A simulation study of the proposed topology has been carried out using power systems computer-aided design simulator and the results are presented. Experimental studies are carried out to verify the proposed topology. [ABSTRACT FROM AUTHOR]

Application of controlled series capacitors with antiparallel thyristor combination across the capacitor segment is one of the new and promising countermeasures for enhancement of power system stability. The line reactance can be directly controlled by the controlled series capacitors, hence, it is very effective to apply the capacitors for damping power system disturbances. [ABSTRACT FROM AUTHOR]

In this letter, a new realization of left-handed transmission line (LHTL) is presented; the proposed structure is realized by periodically loading the coaxial waveguide with gaps in the inner conductor and wires between the inner and outer conductors, the gaps and wires act as series capacitors and shunt inductors. The dispersion characteristic of this new LHTL is analyzed by means of high frequency structure simulator (HFSS) eigenmode simulation and microwave network theory, which exhibits LH behavior over a 60% bandwidth. A backward wave behavior is unambiguously demonstrated from HFSS driven modal simulation. The phase front is observed to be in the opposite direction with respect to the energy one for a finite nine-unit cell prototype. [ABSTRACT FROM PUBLISHER]

A metamaterial based compact microstrip T-junction power divider working at 10GHz is proposed. The metamaterial unit cell consists of microstrip gaps and via holes whose behavior is equivalent to the combination of series capacitors and shunt inductors respectively, that is, a dual transmission line (high-pass) configuration. By adjusting the parameters of these structures, the characteristics of the Metamaterial-medium can be set to achieve a desired phase shift. To validate the design, a T-junction power divider is fabricated and measured. A 70% reduction of the length of the impedance transformer, without significant performance degradation, has been achieved [ABSTRACT FROM PUBLISHER]

Recently, three-dimensional composite periodic media comprising split-ring resonators (SRR) and thin wires have been shown to exhibit a negative refractive index in the frequency range around the SRR resonance. In this letter, we propose transmission line models for studying and interpreting the electromagnetic propagation behavior of such materials. Based on these equivalent transmission line models, we show that by periodically loading a network of transmission lines with series capacitors and shunt inductors, a negative refractive index medium can be synthesized without excess resonators, thus leading to wideband behavior. These proposed media have tailorable properties over a broad frequency range. Moreover, they are completely planar, frequency scalable, more compact, and easier to implement for RF/microwave circuit applications than their SRR/wire counterparts. [ABSTRACT FROM PUBLISHER]

This paper presents the development of mathematical models for a thyristor controlled series compensator (TCSC) for voltage regulator devices and for remote bus voltage controls that are suitable to be used with the three-phase current injection method (TCIM) for power flow calculation. TCIM is a Newton method where the equations are written in rectangular coordinates resulting in a 6n x 6n Jacobian matrix. The representation of a control device requires an augmented system of equations to incorporate the additional relationship between each control action and the controlled variable, resulting in an augmented Jacobian matrix. Practical distribution systems are tested and the effectiveness of the proposed formulation is demonstrated. [ABSTRACT FROM PUBLISHER]