Shunt Capacitor Research Articles

Optimal capacitor placement in northern region of Bangladesh transmission network for voltage profile improvement

This paper solves the problem of optimal placement of shunt capacitors in the northern region of Bangladesh transmission network. During network augmentation event like very high inductive reactive load condition, the weakened voltage profile of the buses can be compensated by optimum allocation of the capacitor banks. In this regard, the aim of this problem is to minimise the costs associated with capacitor banks, transmission system losses and voltage profile improvement whilst satisfying various constraints. Mixed integer linear programming method is introduced for the discrete optimisation problem of placing capacitors in transmission system for cost minimisation and voltage profile improvement. In this proposed formulation, sensitivity dependent voltage magnitude is taken into account for the selection of candidate buses. It is also shown that voltage profile is linearly dependent on reactive load. Therefore, load modelling is done carefully to get a more realistic image of the overall outcomes. The proposed methodology yields integer number of capacitors of particular sizes to be placed on best suited buses. In addition, the proposed approach is applied to IEEE 39 bus system and 33 bus real transmission system of northern region of Bangladesh power system Furthermore, a thorough performance comparison with an existing state-of-the-art capacitor placement method is also performed for validation. The simulation results demonstrate that the proposed methodology is capable of producing optimised solution while successfully mitigating the low voltage issue. Moreover, the proposed approach shows enhanced voltage profile of the buses at a reduced reactive support size than the existing approach.

Pareto Front-Based Multiobjective Optimization of Distributed Generation Considering the Effect of Voltage-Dependent Nonlinear Load Models

Single objective constant PQ load models were extensively considered for site and size of distributed generation (DG) and shunt capacitor (SC) allocation. Which may lead to single non-dominated solution of unpredictable and misleading results about their site and size, loss reduction and payback period. Therefore, primary objective of this study is to investigate the effects of seven nonlinear voltage-dependent load models for the siting and sizing of DG and SC considering various conflicting Multiobjective functions. These objective functions are minimization of active power loss, voltage deviation, cost of energy loss per year, the total cost of installed DG and SC, and emission. Three study cases of simultaneous optimization of two and three objective functions are intended to find optimal integration of DG and SC in the standard 33 and 118-bus radial distribution network considering seven nonlinear voltage-dependent load models. A new Multiobjective evolutionary algorithm (MOEA) called Bidirectional Coevolutionary (BiCo) is applied to the proposed study cases to demonstrate the impact of load model on DG and SC allocation. Further, to show the superiority and performance of proposed algorithm, six state-of-the-art MOEAs are implemented and statistically compared with proposed algorithm using a representative hypervolume indicator (HVI). The maximum savings in annual cost of annual energy loss reaches 58.99% in case1 of PQ load model, 59.4% in case 2 and 64.96% in case 3 of industrial load model considering only DG allocation, whereas, 93.673% in constant PQ load model of case1, 78.908% in constant current load model of case2 and 93.403% of case3 of PQ load model considering simultaneous DG and SC. Simulation results show that the proposed algorithm is adept and suitable to find a better trade-off between various conflicting objective functions compared to other recently designed MOEAs.

Optimal Integration of PV-Based Distributed Generators and Shunt Capacitors for 69 Bus System using Imperialist Competitive Algorithm and ETAP Software

Optimal deployment of photovoltaic-based distributed generators (PVDG) and shunt capacitor units is a perilous task in modern power system planning. This work presents an effective Imperialist Competitive Algorithm (ICA) based on social political process for selecting the best locations and sizes for PVDGs and shunt capacitor units. Three different load patterns, i.e., nominal, decremented and incremented are taken into account while installing PVDG and shunt capacitor units in the typical radial distribution systems of 69-bus. The primary objective of this work is to reduce active power losses and to significantly improve the voltage pattern after positioning of PVDG and capacitor units. The results show that the losses are reduced significantly by integrating the PVDG and capacitor units simultaneously at the optimum position in the test system. Furthermore, results of simulating the 69 bus system (with the integrated PVDG and capacitors) prove to be promising and authentic.

Multi-Objective Optimal Siting and Sizing of Distributed Generators and Shunt Capacitors Considering the Effect of Voltage-Dependent Nonlinear Load Models

Load modeling is essential to distribution system analysis, planning, and control. Therefore, in this work, effect of non-linear load models has been considered for the optimal site and size of DG and SC allocation. A new and efficient modified branch and bus ordering-based forward-backward load flow method has been applied to solve load flow problem in radial distribution system. Recently implemented several state-of-the-art evolutionary algorithms (EAs) are employed to solve optimal site and size of DG and SC allocation problems and it is shown that performance of multi-operator/multimethod is better than other algorithms that are based on a single operator and/or algorithm. Therefore, a new hybrid EA based on various state-of-the-art operators such as GA, DE, and PSO is designed and applied to solve optimal site and size of DG and SC allocation problems. Various technical objective functions (index of active and reactive power loss and voltage deviation index) are considered to show the impacts of non-linear load models. From the simulation results, it is shown that DG and SC allocation problem is multi-objective. Therefore, further weighted sum multi-objective technical, economic, and environmental functions are formulated to find the solution to DG and SC allocation problems. The gathered results demonstrate that the proposed methodology significantly minimizes the cost of energy supplied by grid, total operating cost, and active and reactive power losses. Consequently, it can be stated that the suggested methodology has considerable economic and technological benefits and may be used to address many optimization issues in various distribution networks.

Multi-period Two-stage Robust Optimization of Radial Distribution System with Cables Considering Time-of-use Price

In the existing multi-period robust optimization methods for the optimal power flow in radial distribution systems, the capability of distributed generators (DGs) to regulate the reactive power, the operation costs of the regulation equipment, and the current of the shunt capacitor of the cables are not considered. In this paper, a multi-period two-stage robust scheduling strategy that aims to minimize the total cost of the power supply is developed. This strategy considers the time-of-use price, the capability of the DGs to regulate the active and reactive power, the action costs of the regulation equipment, and the current of the shunt capacitors of the cables in a radial distribution system. Furthermore, the numbers of variables and constraints in the first-stage model remain constant during the iteration to enhance the computation efficiency. To solve the second-stage model, only the model of each period needs to be solved. Then, their objective values are accumulated, revealing that the computation rate using the proposed method is much higher than that of existing methods. The effectiveness of the proposed method is validated by actual 4-bus, IEEE 33-bus, and PG 69-bus distribution systems.

Parallel computing for reducing time in security constrained optimal power flow analysis

This paper presents a novel approach for solving the security-constrained optimal power flow (SCOPF) optimization problem using parallel Computing. In this approach, switched shunt capacitors, generation power ramp, and demand response are considered in the SCOPF by maximizing the market surplus during regular operation and for a set of contingencies of branches and generators. The optimization problem is solved using the Nonlinear Interior Point Method. The contingency assessment is paralleled in multiple CPU cores to decrease the computation time. Additionally, the test systems used in ARPA-GO competition were used and compared with the ARPA benchmark results to assess the proposed algorithm. The numerical results show this method is suitable for fast SCOPF using paralleling Computing.

Harmonic current variation characteristics of shunt capacitors based on full-phase FFT algorithm

Abstract Shunt capacitors can effectively improve the system voltage level and increase the economy of grid operation. However, under the effect of harmonics, the capacitor bank is prone to harmonic resonance, which causes overcurrent and overvoltage and threatens the safe operation of the capacitor itself and the system. To avoid damage to capacitors due to harmonics, the harmonic current variation characteristics of shunt capacitors are investigated. Based on the established mathematical model of shunt capacitors, the characteristics of harmonic current amplification under different harmonic states are analyzed. Based on the amplification characteristics and sampling law, the harmonic current signal is acquired using the full-phase fast Fourier transform algorithm. The full-phase fast Fourier transform algorithm is improved by the phase difference algorithm to complete harmonic current detection. The experiments show that the dynamic response time is 1.6 cycles with minimum steady-state error before and after the load current jump. When the capacitor changes from unit power factor to 0.89 inductance, the harmonic current at point A changes from 17.59A to 21.34A and 11.65 to 22.38A, respectively. The deviation values are 3.75A and 10.73A, respectively. It shows that the algorithm has good tracking ability for load currents and can effectively detect the harmonic currents of shunt capacitors and obtain accurate variation characteristics. It can ensure that the harmonic content of the shunt capacitor in the distribution system is relatively reasonable, and realize the safe, stable and economic operation of the equipment.

A Plasma-Switch Impedance Tuner With Microsecond Reconfiguration

With many frequency bands previously allocated solely for radar now being reallocated for sharing, radar transmitters must be frequency-agile, able to quickly change operating frequency while maintaining detection range. This article details the design of a 2–4-GHz reconfigurable impedance tuner using 35-W plasma switches. The tuner consists of switched shunt capacitor and inductor branches loading a series microstrip line. For many RF matching applications, a reconfigurable impedance tuner must have a broad tuning bandwidth, real-time switching speeds, high power handling, low loss, and broad Smith chart coverage. The implementation of the tuner using semiconductor plasma switches illuminated by laser diodes is described. The tuner is demonstrated in measurements using a custom search algorithm, adjusting and optimizing the tuner settings to provide maximum output power in approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300~\mu \text{s}$ </tex-math></inline-formula> upon changes in operating frequency or antenna impedance. This tuner provides superior reconfiguration times over other high-power tuners in the literature. The tuner possesses losses as low as 0.77 dB and at least 30% Smith chart coverage over the entire tunable bandwidth. With a 26.7- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> switching speed, the impedance tuner is also demonstrated to handle 20 W of power at all frequencies and states with over 40 W of power for greater than half of the octave bandwidth and power handling measured as high as 70 W. The combination of fast reconfiguration and high power handling in an impedance tuner can enable cognitive radar systems to adapt to a congested and dynamic environment in real time.

Planar Inverted Antenna With Embedded Patch Excitor for On-Metal Tag Design

For the first time, a non-resonating patch is embedded inside a planar inverted antenna structure for the design of a low-profile metal-mountable tag antenna. The tag has a compact and low profile with a footprint of 40 mm × 40 mm × 3.3 mm. Efficient coupling between the excitation patch and the radiating patch, which are separated by a narrow and long slotline can improve the radiation efficiency. The slotline can provide sufficient shunt capacitance so that the antenna reactance can match with the chip reactance. The antenna and chip impedances are in conjugate match for the proposed tag, maximum power transfer between the chip and the antenna is possible for a better radiation performance. Being tested with 3.28 W effective isotopically radiated power (EIRP), the proposed tag can attain a good read range of 16 m. The tag antennas resonant frequency is very stable, and it is not significantly impacted by the metallic backing object underneath.

Setting Free Fault Location for Three-Terminal Hybrid Transmission Lines Connected With Conventional and Renewable Resources

Three-terminal hybrid transmission lines (TTHTLs) are attractive from both environmental and commercial view. Hybrid transmission lines are growing due to urbanization, connecting an industrial load and renewable integration. A TTHTL comprises sections of both overhead lines and underground/subsea cables or overhead lines with different X/R ratios. Faulted section identification (FSI) is key for defining the adaptive/selective auto-reclosing scheme and estimation of the fault location for TTHTLs. In this paper, FSI and fault location algorithms are proposed without using the parameters of any line section. Novelty of the methodology lies in a two-stage approach to the problem. In the first stage, series impedance parameters of all the sections are calculated using closed loop formulae. These parameters are then utilized in identifying the faulted section. In the second stage, the above calculated line section parameters and faulted section are used to estimate complete line parameters including shunt capacitance and subsequently the fault location. The advantage of the proposed method is that it does not require an initial guess of the line section parameters, is non-iterative in the first stage, and provides correct fault section identification for TTHTLs. These features make it suitable for designing the selective auto-reclosing protection scheme for the TTHTLs within traditional protection relaying hardware. More importantly, the series impedance parameters calculated in the first stage constitute good initialization values for the non-linear problem of estimating the complete line parameters. This results in better convergence of the algorithm and accurate parameter estimation. The developed solution is verified using the PSCAD/EMTDC simulations for TTHTLs connected with conventional and different inverter-based renewable resources. The performance of the proposed solution is compared with commercially available solutions, and it is found to be accurate. This solution is amenable for implementation in line differential protection relays without additional infrastructural changes.

Improved Design for the High Gain Wideband Matrix Amplifiers Using Differential Cells and Microwave CMOS Technology

The Matrix Amplifier is a structure designed to increase the gain of the wideband distributed amplifiers. A matrix amplifier is used to improve the pass-band gain while preserving the dispersed design-wide characteristics to use the multiplicative gain mechanism. In this paper, the matrix distributed amplifier methodology is developed using differential cells instead of active amplifier cells to improve the wideband characteristics. Shunt capacitances are connected in the centerline to absorb the peaking impact at a cut-off frequency and reduce gain ripples. As an application of the ideas and concepts of matrix amplifiers, a modified step-by-step design of rows 4 and column 2 matrix amplifier is undertaken using a Quasi Differential amplifier. A Matrix differential amplifier using a shifted-second-tier structure technique is then built and tested in 0.18 µm Complementary Metal Oxide Semiconductors technology. The advantages gained from the proposed design are high gain, high bandwidth, low noise, and no need for balun circuits. The design and simulation results were achieved using ADS. The significant results show a high gain of 40 dB and a 33 GHz bandwidth. The noise figure is also 3.583, with S11, S22, and S12 being -10 dB, -10dB, and -40dB, respectively; the output power at 1-dB gain compression point is evaluated (P1dB) of +6.4 dBm, and the total DC power dissipation is 266mW. The cadence tools produced the layout design and specifications, although the chip size was 1.1mm2.

THz Thin Film Varactor Based on Integrated Ferroelectric HfZrO2.

In this paper, we present a broadband microwave characterization of ferroelectric hafnium zirconium oxide (Hf0.5Zr0.5O2) metal-ferroelectric-metal (MFM) thin film varactor from 1 kHz up to 0.11 THz. The varactor is integrated into the back-end-of-line (BEoL) of 180 nm CMOS technology as a shunting capacitor for the coplanar waveguide (CPW) transmission line. At low frequencies, the varactor shows a slight imprint behavior, with a maximum tunability of 15% after the wake-up. In the radio- and mmWave frequency range, the varactor's maximum tunability decreases slightly from 13% at 30 MHz to 10% at 110 GHz. Ferroelectric varactors were known for their frequency-independent, linear tunability as well as low loss. However, this potential was never fully realized due to limitations in integration. Here, we show that ferroelectric HfO2 thin films with good back-end-of-line compatibility support very large scale integration. This opens up a broad range of possible applications in the mmWave and THz frequency range such as 6G communications, imaging radar, or THz imaging.

Signal-based fault diagnosis in Q-pulse diode rectifier with fast and accurate detection of faulty switch

Several industrial applications utilize diode rectifiers due to their robustness and simple structure. The diode rectifier provides DC voltage for high-technology facilities. The internal fault of this converter could increase the amplitude of the 2nd harmonic in its output voltage and input current. These even harmonics can affect the protection system. Fault detection in this converter can develop the controllability of other devices. This paper proposes a fast and accurate algorithm to detect the open circuit fault in the 1ph, six, and higher pulse diode rectifier. In contrast, further research in this paper has tried to offer a robust algorithm against the shunt capacitor effect on the output voltage signal. Also, the proposed algorithm avoids using many sensors and complicated calculations. The proposed method has been evaluated by simulation and experimental results. The result has shown the accuracy of the proposed algorithm even for less than 3 percent voltage ripple.

Tunable underwater low-frequency sound absorption via locally resonant piezoelectric metamaterials

Acoustic metamaterials with passive dissipative elements have demonstrated excellent underwater low-frequency sound absorption abilities, but still suffer from the narrow bandwidth, fixed absorption frequencies and bulky size. In this research, tunable underwater low-frequency sound absorption of the locally resonant piezoelectric metamaterials (LRPM) is systematically studied. A theoretical model of underwater sound absorption based on the LRPM is established. From the perspective of effective materials, the tunable sound absorption characteristics and perfect absorption mechanism are analyzed. The theoretical results are in good agreement with the numerical ones. It is demonstrated that a thin LRPM layer can achieve perfect sound absorption at targeted low-frequency which can be actively tuned by manipulating the resonant shunt circuit. Furthermore, the negative capacitance (NC) shunt can be introduced to the resonant circuit, which significantly improves the sound absorption bandwidth. By applying causality principle to the proposed LRPM, the causal constraints are discussed, which results in an improvement of causal optimality by NC shunt. This research can provide useful guidance for the realization of efficient and widely adjustable ultra-thin underwater sound absorbers.

Performance Analysis and Energy Conservation of PV Based Hybrid Power System

The increase in energy consumption due to population expansion and scarcity of fossil fuels is happening simultaneously in developing countries like India. In this regard, commercial buildings are increasingly required to employ renewable energy sources (like PV) and conserve the energy for improving energy efficiency. This research article examines the performance of such PV-based hybrid power system, consists of 11 kV grid supply, 100 kWp PV plant &amp; 200 kVA diesel generator. The results indicate that the addition of 68.34 kVAr shunt capacitor bank to Automatic Power Factor Compensation (APFC) panel, keeps the Power Factor (PF) unity and also eliminates the PF penalties in electricity bills. The maximum demand (MD) saving Rs 54528.00 (INR) on annual basis is achieved after the integration of PV with low voltage (433 V) distribution system and grid supply (11 kV). This integration has also reduced the average transformer loading to 64.73% and improved the transformer life. However the development of high current harmonics (average value 47.10%) must be reduced to ensure the life of the electrical load.

Distribution network reconfiguration and reactive power compensation using a hybrid Simulated Annealing – Minimum spanning tree algorithm

Change of the climate, environmental pollution and lack of classical energy sources forced many countries to address renewables. In modern strategies of smart distribution network reconfiguration should be applied in order to minimize power losses and economic costs. Also, capacitors switching (placement of shunt capacitors) and presence of distribution generation are always incorporated in modern networks. Further, On Load Tap Changer in the supplying substation has to be used. Simulated Annealing and Minimum spanning tree algorithms work separately in order to find the best appropriate solution. The main goals are minimization of power losses and costs. In addition, many constraints are attended to find the hourly reconfiguration and capacitor banks position. Distributed generators involve both wind generators and solar panels. Two methods described in literature are mixed and implemented for locating fixed nodes for distributed generators. Gauss and Weibull changing nodal loads and wind generators output respectively, as well as daily load curves for working and weekend day with insolation of solar panels are included in analysis. Per unit load diagrams are determined according to real one-year measurement results in one substation in Belgrade, Serbia. IEEE 69 bus network is analyzed. The main contribution of exposed research is near optimal solution for wide time range, realistic network operation/planning forecast (stochastic variation of consumption and production on hour basis) with satisfaction of all technical constraints that are minimum and maximum nodal voltages, limiting feeder’s capacities and not-overcompensation of the network, accompanied with elaborate economic background.

Multi-area distribution grids optimization using D-FACTS devices by M-PSO algorithm

This paper presents a model for the optimization of a multi-area distribution grid considering the high penetration levels of photovoltaic (PV) resources and electric vehicle charging station (EVCSs) based on distributed flexible AC transmission system (D-FACTS) devices including on-load tap changer (OLTC) transformers and step voltage regulator (SVR) tap control and shunt capacitor (SC) and shunt reactor (ShR) to reduce losses and voltage deviation. The overarching research aim was to avoid the overvoltage caused by power injection by PV sources and the voltage drop caused by charging EVs in distribution grids. The proposed model was designed based on distribution network load flow and was optimized using a modified particle swarm optimization (M-PSO) algorithm. Two different test networks were tested under different scenarios to analyze the proposed model, revealing the efficiency of the proposed model.

A novel resonant‐type tunable group delay controller based on third‐order fully tunable topology

AbstractA novel resonant‐type group delay controller based on third‐order resonant topology with tunable central frequency and coupling coefficients is proposed. The coupling structure is realized by coupled line resonators loaded with two shunt capacitors for coupling coefficient tuning, and a series capacitor for resonant frequency tuning, then the group delay and working frequency can be tuned. The structure has the advantage of a large range of tunable coupling coefficients and breaks through the group delay tunable range of traditional delay circuits. The circuit is designed, simulated, and measured. The measurement shows that the group delay can be tuned from 5 to 20 ns with a tunable central frequency in the range of 0.8–1.05 GHz, and minimum ± 0.5 ns group delay bandwidth and −3 dB magnitude bandwidth of 12 MHz.

Design of Inductive Power Taking System for Smart Grid Monitoring Equipment

Due to the continuous growth of urban electricity load and the increasing development of high-voltage transmission technology, the effective operation of the online monitoring equipment of the transmission line is particularly important, which is also a necessary condition for the development of the smart grid. However, the power supply conditions for the usage scenarios of smart grid monitoring equipment are limited. Conventional power supply methods such as battery power supply and new energy power generation have disadvantages such as cumbersome battery replacement, and the power supply stability is greatly affected by the environment, so they are difficult to meet the development trend of a rapid capacity increase of power grid and stable power supply of power equipment. Aiming at the technical bottleneck of smart grid monitoring equipment in power supply, this paper proposes a current transformer inductive power taking method based on capacitive reactance matching shunt, using the open air gap current transformer secondary winding set on the bus to connect the capacitor and its excitation inductance in series carry out capacitive impedance matching, and then shunt through another branch with load and connect it at both ends of the open air-gap current transformer to obtain electric energy. Through the circuit model experiment of the inductive power-taking system, it is verified that the current transformer inductive power-taking method based on capacitive reactance matching shunt can obtain more power.

Injected Current Sensitivity Based Load Flow Algorithm for Multi-Phase Distribution System in the Presence of Distributed Energy Resources

This paper presents an injected current sensitivity (ICS) based multi-phase load flow (LF) methodology with minimal Jacobian computation for the three-phase unbalanced distribution system with multiple Distributed Energy Resources (DERs). In the proposed approach, first, a generalized bus admittance and Jacobian matrix have been formulated that include various distribution system components such as lines, shunt capacitors, voltage control devices such as regulators, different transformer connections, and load models. Second, DERs are modeled as a PV bus and incorporated into the proposed LF algorithm by formulating a reactive power injection-based sensitivity matrix that iteratively computes its net power injections. Unlike the traditional Jacobian matrix-based LF methods where an update of Jacobian (size and element) is required for each PV bus, this method does not require any update, hence, making it faster and more flexible to include a large number of DERs. From the various tests performed on the standard IEEE three-phase distribution network and their derivatives, it has been observed that the proposed approach is accurate, efficient, computationally less complex, and scalable.