Reactive Load Research Articles

Drivers of annual suspended sediment and nutrient yields in tributaries to Lake Erie

Abstract In the early 2000s, harmful algal blooms and hypoxia returned to Lake Erie following a period of ecosystem recovery from the late 1980s through the 1990s. This corresponds to a drastic increase in dissolved reactive phosphorus loads and flow-weighted mean concentrations in the major tributaries to the Western Lake Erie Basin. However, there is substantial variability in suspended sediment and nutrient yields across Lake Erie tributaries. It is well known that agricultural and urban land uses lead to increased watershed sediment and nutrient yields, especially in the absence of proper management practices. Yet attributes such as watershed soil types and slope can also affect yields. We examined the influence of watershed land use, hydrology, soil type, and slope on annual nutrient and sediment yields from tributaries to Lake Erie monitored as part of the Heidelberg Tributary Loading Program. A minimum of one sample and, during storm runoff, up to three samples a day are analyzed for all major nutrients and suspended sediments. The 5-year average annual yields across these watersheds exhibited distinct geographic patterns from west to east, with high suspended sediment but lower nutrient yields from the eastern most tributaries (Cuyahoga, Old Woman Creek, Huron) and the lowest sediment along with lower nutrient yields from the western most tributaries (Raisin, Tiffin, Lost). The Maumee, Portage, Sandusky, along with select subwatersheds tended to have intermediate sediment yields with high nutrient yields. Altogether, the % cultivated crops and poorly drained soil in the watershed increased nutrient yields whereas a higher % slope and lower % pasture increased sediment yields. These patterns highlighted unique regional differences that can help guide management decisions for these watersheds that ultimately would improve the health of Lake Erie.

Designing of a multi-frequency vibrator antenna on meander line with resonant loads and fragmented “floating ground”

Problem definition. Many VHF communication devices include multi-frequency vibrator antennas, among which a special place is occupied by the vibrator antennas with reactive loads as the most compact and simplest to produce. However, inductive loads usually used in practice don’t provide current cut-off at higher operating frequencies, which results in deformations of radiation patterns, and resonant circuits loads don’t provide sufficient shortening of the vibrator antenna due to appearance of shunt inductances. There is a need to formulate the new idea of the designing the multi-frequency vibrator antenna, which has absolutely another mechanism of work, is needed. Purpose. The purposes of this article are: to suggest the idea of the design the multi-frequency vibrator antennas, based on hybrid of meander line with parallel LC-circuits and fragmented “floating ground”; to form an equivalent scheme for calculating characteristics; to develop a methodology for calculating this type of antennas characteristics (input impedance, VSWR, current distributions over the vibrator and far-field radiation patterns); to do the calculation of characteristics of the monopole antenna on meander line with loads and to make an experimental check of the theoretical results. Results. A design of the multi-frequency vibrator antenna on meander line with parallel LC-circuits loads and fragmented “floating ground” is shown. An equivalent scheme for calculating antenna characteristics is given, an algorithm of calculation of input characteristics and current distributions over the antenna (both meander and “floating ground”) is described. The calculation of input impedance, VSWR, current distributions and radiation patterns of the vibrator antenna with two LC-circuits loads in meander line is done. An experimental check of the theoretical results in VSWR and far-field radiation patterns is made. Applicability of the proposed idea and methodology for the design the multi-frequency vibrator antennas on meander line is shown by analyzing calculated and experimental data. Practical significance. The results of this work can be used to design the multi-frequency VHF vibrator antennas with resonant loads, which have the identical radiation patterns at all operating frequencies.

Metamaterial inspired electromagnetic bandgap filter for ultra-wide stopband screening devices of electromagnetic interference

Presented here is a reactively loaded microstrip transmission line that exhibit an ultra-wide bandgap. The reactive loading is periodically distributed along the transmission line, which is electromagnetically coupled. The reactive load consists of a circular shaped patch which is converted to a metamaterial structure by embedded on it two concentric slit-rings. The patch is connected to the ground plane with a via-hole. The resulting structure exhibits electromagnetic bandgap (EBG) properties. The size and gap between the slit-rings dictate the magnitude of the reactive loading. The structure was first theoretically modelled to gain insight of the characterizing parameters. The equivalent circuit was verified using a full-wave 3D electromagnetic (EM) solver. The measured results show the proposed EBG structure has a highly sharp 3-dB skirt and a very wide bandgap, which is substantially larger than any EBG structure reported to date. The bandgap rejection of the single EBG unit-cell is better than − 30 dB, and the five element EBG unit-cell is better than − 90 dB. The innovation can be used in various applications such as biomedical applications that are requiring sharp roll-off rates and high stopband rejection thus enabling efficient use of the EM spectrum. This can reduce guard band and thereby increase the channel capacity of wireless systems.

Technique for Reactive Loss Reduction and Loading Margin Enhancement Using the Curves of Losses versus Voltage Magnitude

This paper presents an alternative methodology to obtain the precise amount of shunt reactive power compensation in order to simultaneously reduce the total reactive power losses, improve the voltage profile and increase the loading margin of power systems. The amount of shunt reactive power compensation to be allocated is determined based on the curve of the total reactive power losses versus the voltage magnitude of a chosen bus. The best places for shunt reactive compensation are defined by the load bus participation factors of the critical mode provided by the static modal analysis. Simulation results employing shunt capacitors obtained with the new approach for the IEEE test systems (14, 57 and 300 buses) show that the procedure leads to a reduction in total reactive and active power losses and simultaneously improves the voltage profile and loading margin.

Resilient power distribution network reconfiguration under variant load scenarios

This paper addresses the applicability of a resilient reconfiguration of power distribution networks (PDNs) via inserting on-line tie switches (TSs) whenever necessary. Recent metaheuristic algorithms such as Arithmetic Optimization Algorithm and Marine Predators Algorithm are used to look for the best positions of inserting new TSs in the PDN. Two IEEE systems, namely the 33-bus and the 69-bus systems are considered. Simulations show that using three TSs is sufficient for the 33-bus system to handle doubled active and reactive power loads, while only two new TSs can raise the 69-bus systems’ capability when the loads are elevated by 85%. Static and day-ahead variant load scenarios are considered. Using the proposed approach, power losses (Ploss) reduction can reach 57.88% and the minimum voltage magnitude becomes 0.9838 p.u. for the 33-bus system (PQ × 0.5 scenario). In day-ahead scenario, Ploss can be reduced by >69% at peak hour, for both systems.

Design of Circularly Polarized Smartwatch Antenna With Reactive Loads

Designing multi-functional antennas is challenging for smartwatches enclosed by metallic frame. In this letter, we propose an efficient and practical method to realize circular polarization (CP) and multiband operation for smartwatch antennas. The method is based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -port network, with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> ports initially placed along the ground clearance. By varying the impedance matrix using reactance, the total currents of the antenna and hence the far-field properties are optimized. The optimization is performed using multi-objective optimizer NSGA-II. As a result, three reactive loads, with the optimized locations and values, are applied to the smartwatch with metallic frame, providing an axial ratio (AR) of 2.2 dB at the GPS L1 band and wide bandwidths at both the GPS L1 and WLAN/BT bands in the arm-worn scenario. Antenna prototype was fabricated, with the measured results agreeing well with the simulated ones. The simple and practical implementation is quite attractive for commercial smartwatch antennas.

Efficient Anomalous Reflector Design Using Array Antenna Scattering Synthesis

A perfect anomalous reflector is designed by employing the receiving and scattering array antenna theory to optimize the scattering characteristics of a planar reflecting surface. For periodic reflectors with a supercell consisting of a relatively few reactively loaded radiating elements, reflection amplitudes into propagating Floquet modes are controlled in an algebraic optimization of the load reactances, avoiding brute-force optimization via electromagnetic simulations. Wide-angle reflectors are numerically designed and compared with the conventional reflectarray designs, showing that the proposed design approach achieves reflection efficiencies higher than the linear reflection phase gradient method in a computationally efficient manner.

Optimal reactive power planning under active and reactive power steady state load model

This research article proposes a unique planning strategy of reactive power (VAr) considering static load model in power transmission system. An exponential static load model of active and/ or reactive power is considered during the study of load flow solution through Newton-Raphson method. This load model is designed with active and reactive exponents on the flow of active and reactive power through the transmission network. The power losses from load flow solution is measured and minimized through the proper placement of compensation devices. Here two types of FACTS (flexible ac transmission systems) are used in order to compensate reactive power. The separate and collective effect of active and reactive power modeling on load flow is also observed during the calculation of total operating cost (TOC) of the system. The TOC is formulated mathematically by adding different cost components such as cost due to real power loss, VAr generation cost component, compensation device cost component. To validate the impetus of the proposed planning strategy small, medium and large transmission systems are considered in this research work.

Full-Wave Numerical Analysis of Dual-Band EPatch Antenna and Reactive Loading Technique to Ascertain the Impedance Driving Point Function

Full-Wave Numerical Analysis of Dual-Band EPatch Antenna and Reactive Loading Technique to Ascertain the Impedance Driving Point Function

Pattern Synthesis for Lossy Antennas Based on N-Port Characteristic Mode Analysis

In this paper, a pattern synthesis methodology for lossy antennas is proposed based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -port characteristic mode analysis (CMA), with the radiation efficiency of the antenna guaranteed at the same time. Reactive loads are chosen as physical implementations. To perform <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -port CMA, N ports are firstly added to the lossy and lossless structures to obtain the impedance matrices. Modal efficiencies are then calculated, based on which the locations of the feed and the loads are selected. With the characteristic solutions and one set of modal weighting coefficients (MWC), where inefficient modes have been excluded, corresponding loads and radiation pattern can be determined. Afterwards, an objective function considering physical implementation and the target pattern is establish and optimized. With optimal MWCs, the lumped components loaded at each port are calculated and implemented. The method is applied to an arm-worn smartwatch antenna operating at GPS L1 band, which aims at radiating towards the sky direction for reliable link with satellites. Following the proposed method, the power radiated towards the target area has been increased by more than 40% compared with the original design. The total efficiency is above -6.1 dB when it is worn on a CTIA arm. The prototype of the proposed antenna has been fabricated and measured, which showed similar performances to the simulated one both in free space and in the arm-worn scenario.

Numerical Simulation Study on the Blast Loading Performance of Reactive Fragment

In this paper, numerical simulation is used to study the buffer layer material, thickness and structure on the reactive fragment load and its action time under blast impact loading conditions. The results show that the buffer layer can significantly reduce the peak pressure of the detonation wave acting on the reactive fragment and prolong the action time; the buffering capacity of different buffer materials is different; for the same material, the buffering capacity is proportional to the material thickness; compared with a single layer of buffer layer, the buffer layer with the same thickness and composite structure has a stronger capacity.

A Hybrid Impedance Matching Network for Underwater Acoustic Transducers

The underwater acoustic transducer (UAT) is an electro-acoustic conversion device, which is a nonlinear reactive load. An impedance matching network is usually added between the power amplifier and the UAT. This paper proposes a hybrid impedance matching network (HIMN) combining passive impedance matching and active impedance matching. Compared with the conventional matching, this method can improve the matching frequency range and reduce matching delay. Firstly, the impedance model of the UAT is proposed, and the matching principle of the HIMN is analyzed. On this basis, the parameter design method is given within the required frequency range. Then, to reduce the matching delay of the system, a control method based on reference signal synchronization is proposed, including the reference compensation voltage calculation method and model prediction control (MPC) with two-step prediction. Finally, the simulation and experimental hardware in loop (HIL) results are given, which verify the effectiveness of the proposed HIMN and control algorithm proposed in this paper. The results show that the proposed HIMN can achieve a wider matching frequency range and shorter matching delay.

Overview of Various Voltage Control Technologies for Wind Turbines and AC/DC Connection Systems

Wind power generation is one of the mainstream renewable energy resources. Voltage stability is as important as the frequency stability of a power system with a high penetration of wind power generation. The advantages of high-voltage direct current (HVDC) transmission systems become more significant with the increase of both installed capacity and transmission distance in offshore wind farms. Therefore, this study discusses various voltage control methods for wind turbines and HVDC transmission systems. First, various voltage control methods of a wind farm were introduced, and they include QV control and voltage droop control. The reactive power of a wind turbine varies with active power, while the active power from each wind turbine may be different owing to wake effects. Thus, QV and voltage droop control with varying gain values are also discussed in this paper. Next, the voltage control methods for an HVDC transmission system, such as power factor control, voltage control, and Vac-Q control, are also summarized and tested in this study. When a three-phase short circuit fault occurs or a sudden reactive power load increases, the system voltage would drop immediately. Thus, various voltage control methods for wind turbines or HVDC can make the system’s transient response more stable. Therefore, this study implemented the simulation scenarios, including a three-phase short circuit fault at the point of common coupling (PCC) or a sudden increase of reactive power load, and adopted various voltage control methods, which aim to verify whether additional voltage control methods are effective to improve the performance of transient voltage. The voltage control method has been implemented in PSCAD/EMTDC, and the simulation results show that the QV control performs better than the droop control. In addition, when applying the voltage control technique during a three-phase fault, transient voltage nadir can be improved through either an HVDC transmission system or an AC transmission system.

Improvement of Power Quality in Primary Distribution Systems Based on Static-Var Compensators

A flexible AC Transmission Systems (FACTS) is a new technology offers a fast and reliable control over the transmission and distribution parameters like voltage and phase angle between the sending end voltage and receiving end voltage. Distribution static synchronous compensator (DSTATCOM) is a second generation member of the (FACTS) controllers. Reactive power compensation is an important aspect in the control of distribution systems. Reactive current in addition to increasing the distribution system losses, introduces voltage drop at lead point and finally it causes poor power quality in power systems. Primary radial distribution feeders have high resistance to reactance ratio, which causes voltage drop and high power loss in radial distribution systems. providing high demanding power to entire load while maintaining voltage magnitude at acceptable range is one of the major system constraints, using of capacitor banks to improve the reactive power have not quite enough at high reactive power feeder, because it have more slow in step by step response and have not capable to generate continuously variable reactive power. In some primary distribution feeders at the state of Khartoum, it is observed that there are some appropriate drops in voltage and quality service at high reactive power loads although some individual capacitor banks have been connected at these feeders, from here we researched for a new technology to overcome this problem. A steady-state model of (DSTATCOM) is proposed and developed to compensate the reactive power by using a Voltage Source Converter (VSC) with Pulse Width Modulation (PWM) and cascade control of four direct proportional integral controllers (PI) in synchronous reference frame. The detailed modeling and control design of (DSTATCOM) with specific typical radial primary distribution feeders (industrial, commercial, residential) are presented and implemented along necessary mathematical model equations in the Matlab software. Simulation schemes of (DSTATCOM) are done with help of control block diagrams and stability analysis. Load flow is an important method for analysis, operation and planning studies of any power system in a steady-state condition. In this research backward forward sweeps load flow method (Kirchhoff’s Laws) has been proposed rather than Newton-Raphson and Fast decoupled methods because the distribution feeders have a high R/X ratio which make the systems are ill-conditioned iterations analysis. (DSTATCOM) was installed on specific typical radial feeders at the (DSTATCOM) which using for distribution lines and load compensation has been the subject of considerable interest beside it is a new technology for a good power quality solution. Keywords: Power System, Flexible AC Transmission Systems (FACTS) Devices, STATCOM, PI Controller DOI: 10.7176/ISDE/13-1-05 Publication date: May 31 st 2023

Single-RF MIMO-OFDM Using ESPAR

A novel beamspace multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) transmission system using a single-radio-frequency (RF) electronically steerable parasitic array radiator (ESPAR) is described. It makes use of recent results for decomposing the patterns of any arbitrary ESPAR onto an orthogonal basis set using the Theory of Characteristic Modes (TCM). Leveraging this decomposition, OFDM symbols can be mapped into the beamspace domain so that the ESPAR can be used to transmit multiple streams of OFDM symbols using a single RF chain. In the proposed approach, we use the Linde-Buzo-Gray (LBG) algorithm to quantize the OFDM symbol vectors and form a codebook. A binary search tree is then utilized to efficiently find the reactive loads of ESPAR to excite the radiation patterns corresponding to the quantized symbols. It is shown by simulation that quantized codewords and the corresponding radiation patterns can be excited using ESPAR. In addition, the simulated bit error rate (BER) results of the proposed approach are shown to be close to that of conventional MIMO-OFDM systems, demonstrating the effectiveness of implementing a single-RF MIMO-OFDM transmitter.

Power Quality Improvement in Rural Grid Using Adaptive Control Algorithm to Enhance Wind Energy Penetration Levels

The intermittency associated with Wind Energy causes Power Quality (PQ) disturbances, which in turn can limit the penetration levels. These penetration levels are further restricted due to the non-linear (NL) loads and the weakness of the grid (especially in the rural grid). This paper proposes a methodology to enhance wind power penetration levels into the rural grid by mitigating PQ disturbances using a DSTATCOM controlled by Adaptive Least Mean Fourth (ALMF) control. The proposed algorithm computes the active and reactive load current components with the help of updated weights by continuously adapting the changes in grid voltages, wind speed and DC-link voltage to generate reference currents, which are used to generate switching signals for the DSTATCOM. Various case studies establish the effectiveness of the proposed algorithm in MATLAB simulation and experimentally to enhance the wind energy penetration level up to 25% into the rural grid with a short circuit ratio as low as 2.74 in the presence of NL loads.

Increasing Reactive Load of a Generator–Transformer Unit under the Influence of Quasi-Direct Currents

Increasing Reactive Load of a Generator–Transformer Unit under the Influence of Quasi-Direct Currents

FORCE STUDY OF REACTIVE LOADS IN KINEMATIC COUPLES OF A WORKING CAPACITY TURNING MACHINE WITH COMPLEX SPACE MOVEMENT AND VARIABLE VOLUME

High productivity when performing finishing technological operations, as well as technological processes of mixing loose fine-dispersed substances, can be achieved with the use of equipment in which working containers perform complex spatial movement. To date, various types of developed felting machines with complex spatial movement of working containers are known. Each type of such equipment corresponds to the implementation of various felting technological operations – separation of parts from sprues, grinding or polishing of products, cleaning of metal parts from corrosion or mixing of loose fine-dispersed substances. During the operation of the rolling equipment, various reactive loads arise in the kinematic pairs, which depend on the design features of the machines. With the use of the automated design system “SolidWorks”, 3D modeling and further strength research of a model of a rolling machine with a working capacity with complex spatial movement and variable volume was performed. In the kinematic chain of the machine under study, an additional moving connecting rod link with rotational and translational kinematic pairs is used. During the performance of the force study, the reactions in all rotational and translational kinematic pairs were determined, the influence of the change in the interaxial distance of the working capacity and the additional moving link of the connecting rod on the maximum values of the reactions in the kinematic pairs of the machine was investigated. The presented results of analytical studies can be applied in the relevant design bureaus of machine-building enterprises at the stage of designing equipment with complex spatial movement of working capacities and felting technological processes.

Presenting a Stochastic Model of Simultaneous Planning Problem of Distribution and Subtransmission Network Development considering the Reliability and Security Indicators

Consumption growth demands power system expansion, and changes in a network lead to changes in operation indices of the upstream network. Hence, to establish a reliable planning of the distribution network, simultaneous planning of the subtransmission network should also be taken into account. It is predicted that this planning impacts different technical indices; therefore, formulation of various technical indices need to be included in the planning model. Therefore, in this study, the stochastic problem model of simultaneous planning of distribution and super distribution network development considering the reliability and security indicators is presented. The aforementioned problem is in the form of an optimization problem whose objective function is to minimize the costs of construction, replacement, operation, maintenance, reliability, and security. Furthermore, the mentioned problem is bound to the equations of power distribution, reliability, and security of voltage in addition to the limitation of network indicators. It is worth mentioning that, in the proposed problem, the active and reactive loads in addition to the operating price are in the form of uncertainty. Thus, the mentioned problem is in the form of a stochastic problem in which the point estimation method is used to evaluate the scenarios. Simultaneous expansion planning of distribution and subtransmission networks along with the placement of distributed generations and capacitors, as well as modeling security and reliability indices, is the novelty of the proposed scheme. In the end, the proposed problem is applied to the test network by GAMS optimization software, and then the capabilities of the proposed problem are extracted. Accordingly, based on numerical results, the expansion of distribution networks imposes considerable cost. Moreover, expansion planning of both distribution and subtransmission networks helps voltage to be in its permissible range, lower power loss, and improve reliability and security to 100%.

A reactive power planning model for power transmission systems using meta-heuristics algorithms

The load patterns in electricity markets are changing rapidly worldwide. The power engineers are becoming more vigilant in providing an uninterrupted power supply at different loading conditions. This study proposes a unique planning strategy of reactive power (VAr) considering a static load model in the power transmission system. The active/ reactive power-oriented exponential load model for static load is considered during the study of load flow solution. The load flow solution’s power losses are measured and minimized by properly placing compensation devices. A flexible ac transmission system (FACTS) technology has been applied in this proposed planning strategy to compensate for reactive power. The separate and collective effect of active and reactive power modeling on load flow is also observed during the calculation of the total operating cost (TOC) of the system. The TOC is formulated empirically by adding different cost components such as cost owing to real power loss, VAr generation cost component, and compensation device cost component. A real-world power transmission system is considered in the study to validate the impetus of the proposed planning strategy.