Line Impedance Research Articles

Lightning Arrester Analysis at Pandu 150 Kv Substation

The process of distributing electricity from the substation to the consumers often occurs interference, electrical interference at the station caused by two factors that are internal factors and external factors. Internal factors such as lack of good equipment, while external factors such as human error and natural disturbances such as lightning, earthquakes, flood, wind and others. Safety protection system on electrical equipment of Pandu substation. Surge arresters play an important role in Pandu substations to limit switching overvoltages and lightning strikes, followed by overvoltages from lightning current to earth. the efficiency of the arrester is a function of the distance from its location to the protected equipment, the maximum system voltage achieved is 165 kilo vot, the arrester`s rated voltage is 132 kilo volt line impedance /conductor 475,764 ohms, air insulation breakdown voltage 1515.8 kilo voltv, arrester discharge current 4.27 kilo ampers and an optimal distance between arrester and transformer 10.96 meters.

Multi-target fault ride-through strategy for transformerless MMCs under asymmetric grounding faults in AC/DC hybrid distribution networks

In AC/DC hybrid distribution networks (HDNs), when asymmetric grounding faults occur, transformerless multiterminal modular multilevel converters (MMCs) should achieve three key targets of fault ride-through (FRT): 1) limiting the unbalanced fault currents; 2) injecting currents to support grid voltages in case of disconnection from grids; and 3) eliminating the zero-sequence circulating currents (ZSCCs) from fault networks through MMCs to nonfaulted networks. However, in medium voltage-level HDNs, the line impedances are mainly resistive-inductive, and traditional current injection methods are no longer effective. Moreover, in neutral nondirect grounding networks with multiple AC voltage levels, the voltages of nonfaulted phases rise, and it is difficult for MMCs to achieve fault current control. To solve the above issues, this manuscript proposes a multi-target FRT strategy. First, negative-sequence current controllers are used to eliminate the negative-sequence fault currents. Then, to support the positive-sequence voltages of grids, optimal and suboptimal active-reactive current references based on the line impedance ratios are proposed. To help transformerless MMCs with low modulation indices eliminate zero-sequence circulating currents, two zero-sequence voltage compensation modes and an improved zero-sequence current eliminator are proposed. Finally, the proposed fault current control is verified in MATLAB/Simulink.

Distributed control for multiple hybrid energy storage systems using consensus algorithm in direct current power supply system

Multiple hybrid energy storage systems (multi-HESSs) consisting of batteries and supercapacitors (SCs) is widely used to share the requirement of system pulsating power, reducing the dependence on a single hybrid energy storage system (HESS) to improve the system reliability. The filter composed of virtual resistance droop control (VRDC) and virtual capacitance droop control (VCDC) in a HESS can achieve frequency distribution of pulsating power between a battery and SC. However, it suffers from the output voltage deviation and terminal voltage variation. Mismatched line impedances and different system parameters can cause different output voltages and inaccurate current sharing in the multi-HESSs. Meanwhile, the differences in the terminal voltages of SCs can affect the transient output capability. Therefore, this paper proposes a consensus-based distributed control strategy (CDCS) for multi-HESSs, which not only achieves global average output voltage and current sharing for batteries but also realizes restoration and consistency of SCs terminal voltage. The state variable information of adjacent converters for multi-HESSs is exchanged by the sparse communication network, and the steady-state analysis of state variables is proved. The direct current (DC) power supply system with four HESSs is established to verify the effectiveness of the proposed control strategy.

Effect of Shunt Resistor Value on the Performance of Resistive Superconducting Fault Current Limiters

Resistive-type superconducting fault current limiters (r-SFCLs) have generated great interest for research and technical applications. This is attributed to their superior features, which include self-action, fast response, and simple operation. In low line impedance systems, r-SFCLs are seen as a viable protective mechanism for limiting high-magnitude fault currents. However, overcurrent caused by faults results in an increased temperature of the r-SFCL, possibly damaging the coils. Thus, the r-SFCL must be appropriately engineered to protect it while still allowing for effective fault current limitation. To achieve this goal, an appropriately sized shunt resistor must be used. Adding a shunt resistor benefits the r-SFCL in several ways, from lowering its maximum temperature to speeding up its recovery. Additionally, the shunt resistor protects the r-SFCL from excessive surges in temperature by giving the current an alternative path to flow down, thus saving it from further damage. A multilayer thermoelectric model was developed to examine the thermoelectrical behavior of the r-SFCL coil throughout a fault occurrence and the subsequent recovery period using three shunt resistors ranging from 4 to 16 Ω. MATLAB®/Simulink was used as the simulation platform in this study. The dependence of the current limitation capability and the voltage profile on the shunt resistor value was studied compared to the basic case without an r-SFCL. Increasing the shunt resistor value led to an enhanced ability to limit fault currents, although at the cost of higher temperatures and a longer recovery time. This study also presents guidance for optimizing the design parameters of r-SFCLs.

Renewable Energy Impact on Distance Relay Power Swing Blocking and Fault Discrimination: A Review

The annual increase of the global load demand has led to higher penetration of inverter-based renewable energy resources like wind farms and solar PV into the modern grid system. Distance relay may mal-operate by incorrectly estimating line impedance as fault during swing scenarios considering the infeed contributions impact from renewable sources. The negative impact of these integrated power electronics-based devices on the power swing blocking (PSB) and out-of-steps tripping (OST) functions of the distance relay characteristics has not been extensively discussed in previous studies. This study divulges a comprehensive review of the various PSB and OST schemes studies conducted to prevent relay mal-operation during power swing (PS) and symmetrical faults. Also, the large-scale renewable resources penetrations impact the PS characteristic and trip decision operation of the distance relay divulged. The mining of distance relay event records for hidden useful knowledge deployment for intelligent PSB and OST functions is the future research direction. Using the distance relay divulged knowledge will assist in reducing the failure rate level of PSB and OST function distance relaying schemes, hence improving the degree of reliability/dependability of the power system under different operating conditions.

A Brief Review on Power Quality Improvement using UPFC

Abstract: Load demand is rising rapidly these days, necessitating an increase in generation capacity. Voltage instability arises as a result of external and internal imbalance, causing the bus voltage to vary. The FACTS device Unified Power Flow Controller (UPFC) is used to maintain stable voltage and improve power flow in transmission lines. This study examines the comparison of different FACTS devices as well as the analysis of UPFC to control both. In comparison to other FACTS devices such as STATCOM, which regulates only voltage, TCSC, and SVC, which controls only impedance, UPFC is one of the most promising FACTS devices since it can manage phase angle, voltage magnitude, impedance, and many line parameters selectively or concurrently

Power decoupling control of paralleled virtual synchronous generators based on virtual complex impedance

With the high ratio of distributed generation (DG) linked to power system via converters, power system stability is degraded in terms of inertia and damping. In recent years, the virtual synchronous generator (VSG) has become a potential solving method to deal with these issues. However, the power coupling problem exists in the traditional VSG control method, which severely impacts the VSG power control performance. The impedance characteristics of the transmission line are closely related to the effect of the power decoupling control of VSGs. To solve the voltage sag and poor robustness issues resulting from traditional virtual impedance control, a virtual complex impedance power decoupling and sharing control strategy for VSGs based on coordinate transformation is proposed. Combining the characteristics of traditional virtual impedance control and virtual power control, the power coupling mechanism in parallel VSGs caused by line impedance is analyzed. The virtual complex impedance control loop is introduced in VSG control to realize the matching of the equivalent line impedance and the precise decoupling of VSG power output. Then the load can be accurately allocated in the light of the proportion of VSG capacity.

Power-frequency admittance model of multi-VSGs grid-connected system considering power coupling

The high penetration of renewable energy decreases the inertia of power systems. The virtual synchronous generator (VSG) control technology has good inertia compensation effect and has attracted considerable attention because of the similar external characteristics of synchronous generators. However, the power and frequency oscillation of multi-VSG grid-connected systems seriously threatens the stability of power system. Existing multi-VSG power frequency admittance (PFA) models ignore the power coupling caused by the large line impedance ratio in medium- and low-voltage microgrids, and the accuracy of these models needs improvement. Thus, this study aims to establish a multi-VSG grid-connected PFA model considering power coupling. The influence of power coupling on model accuracy is analyzed, and the impacts of line impedance and reactive loop coefficient on the power-frequency response characteristics are investigated. Simulation results verify that the proposed model has higher accuracy over existing models.

Dynamic Distributed Collaborative Control for Equitable Current Distribution and Voltage Recovery in DC Microgrids

In a stand-alone DC microgrid featuring several distributed energy resources (DERs), droop control is adopted to achieve a proportional distribution of current among the DERs within the microgrid. The operation of the droop control mechanism leads to a variation in bus voltage, which is further amplified by the line impedance between the DC bus and DERs. This paper proposes an enhanced distributed secondary control technique aimed at achieving equitable current sharing and voltage regulation simultaneously within a DC microgrid. The proposed distributed secondary control is incorporated into the cyber layer of the microgrid, facilitating the exchange of information among the controllers. In the event of a communication link breakdown, this technique upholds the reliability of the entire system. The control loop utilizes a type-II fuzzy logic control framework for the adaptive selection of the control parameters to improve the control response. Furthermore, the proposed technique can handle both resistive and constant power loads without any particular prerequisites. Utilizing the Lyapunov method, appropriate stability criteria for the proposed controller have been formulated. Various tests were performed across a range of operational scenarios to assess the robustness of the proposed control technique through MATLAB/Simulink® models, which have been validated with real-time experiments. The outcomes revealed that the proposed control effectively achieves its control objectives within a DC microgrid, showcasing rapid responsiveness and minimal oscillation.

A Novel Islanding Detection Method for Distributed PV System Based on μPMUs

With the rapid development of distributed PV systems in distribution grids, unintentional islanding is one major concern which maybe cause safety hazards. The existing passive islanding detection methods are mainly based on the voltage and frequency deviations during islanding conditions. Passive methods have relatively large non-detection zone (NDZ) and susceptible to power system faults. Active islanding detection methods applied in inverters have relatively small non-detection zone, but they are usually harmful to power quality. This paper presents a new islanding detection method based on equivalent inter-connection line impedance, which is normally a small value. A measured impedance is calculated with the synchronous phasors from two lPMUs which are installed in a utility substation and a PV system. Under the grid-connected condition, the measured impedance is no more than the equivalent line impedance. While under the islanding condition, the measured impedance is much larger than the equivalent line impedance. So, an islanding condition can be effectively detected by the comparison of the measured impedance with the equivalent line impedance. The non-detection zone of this proposed method is nearly zero. The detection time is normally less than 250ms. This method is applicable for PV systems connected to the power system with a distribution transformer. It is also applicable for a distribution grid with multiple distributed generation systems.

Linking the Intrinsic Electrical Response of Ferroelectric Devices to Material Properties by Means of Impedance Spectroscopy

Ferroelectric devices have gained attention in recent years as a potential solution for ultra-low power computing due to their ability to act as memory units and synaptic weights in brain-inspired architectures. One way to study the behavior of these devices under different conditions, particularly the influence of material composition and charge trapping on ferroelectric switching, is through impedance spectroscopy. However, the parasitic impedance of the metal lines that contact the electrodes of the device can affect the measured response and interpretation of the results. In this study, we examined the frequency response of ferroelectric tunnel junctions (FTJs) with a metal-dielectric-ferroelectric-metal (MDFM) stack at various voltages, starting from the analysis of single layer capacitors (MFM and MDM) to better interpret FTJs results. To accurately assess the intrinsic response of the device, we developed a method that estimates and removes the parasitic access impedance contribution, which was validated by means of physics-based simulations. This method allows quantifying the intrinsic device-level variability of FTJs and, for the first time, to investigate the relation between the thickness of the dielectric layer, the equivalent phase composition of the ferroelectric material, and the magnitude of the peak in the frequency response, often assumed to be related to charge trapping only.

A microstrip patch antenna for 5G mobile communications

The advantages of microstrip patch antennas include small size, adaptable surface, ease of fabrication, and compatibility with integrated circuit technology. Numerous experiments have been done over the past few decades to enhance the performance of this antenna, and both military and commercial sectors have found many uses for it. This paper introduces a microstrip patch antenna with an operating frequency of 28GHz for 5G mobile communication. This research designed and simulated a rectangular microstrip patch antenna with 3.494 mm * 5.3 mm * 0.003 mm. The proposed antenna resonates at 28 GHz with a reflection coefficient of -24 dB, a bandwidth of 280 MHz, and a gain of 2.2 dBi. The inset feed technique matches the 50 Ω transmission line impedance. In the design, Rogers RT5880 substrate and copper ground are used. The antenna’s geometry was calculated, and simulated results were analyzed using Computer Simulation Technology Microwave Studio. In conclusion, the proposed antenna has a reflection coefficient of -24 dB, VSWR of 1.24, an input impedance of 51.6Ω, and a gain of 2.2 dBi at operating frequency with a compact geometry can be used in 5G mobile communications. The future shift in resonance frequencies and beams can be considered to make the antenna operate as a smart antenna.

Research on concentrated frequency-dependent parameter model for short overhead transmission lines based on first-order rational function fitting

The impedance of power lines is influenced by geological conditions and skin effect, resulting in frequency-dependent characteristics. In this study, a centralized parameter frequency-dependent line model based on first-order rational function fitting is investigated for short overhead transmission lines. The proposed model incorporates a parallel branch consisting of resistance and inductance obtained through rational function fitting, which mimics the frequency-dependent behavior of the line. The coupling between multiple conductors is represented using controlled sources. Comparative analysis of fitting accuracy and computational efficiency across various orders of rational functions reveals that the first-order rational function fitting offers superior computational efficiency while maintaining high accuracy in the medium and low-frequency range. Simulation results demonstrate that the proposed model, when disregarding wave propagation effects, exhibits comparable accuracy to the distributed parameter line model while achieving higher computational efficiency. Moreover, in transient analysis predominantly influenced by power frequency, the proposed model outperforms the frequency-independent pi(π) line model in terms of accuracy.

A kind of planar waveguides for cheating the high-speed digital signals into misidentifying the characteristic impedance

Since a planar periodic transmission line can suppress drastically the electromagnetic coupling, it would be advantageous to use such a kind of transmission lines in solving the problem of miniaturization of circuit area. By adjusting the lattice constants and geometric parameters of periodic microstrip lines, a time domain characteristic impedance that is the same as that of conventional microstrip lines (CMLs) can be achieved. Such periodic microstrip lines can therefore be used to trick high-speed digital signals, causing a digital signal to misjudge the time domain characteristic impedance of the transmission lines. The theoretical analysis has been verified by our experimental measurement results. Besides, a specific expression for the characteristic impedance of lossless periodic artificial materials is deduced by a circuit model and a standard of misidentification for the characteristic impedance of periodic microstrip lines is given for the digital signals.

The characteristic impedance calculation method of microstrip line and application in embroidered microstrip line

Presently, it is difficult to measure the characteristic impedance of embroidered microstrip line for its conductive anisotropy directly. The published work had proposed to use S-parameters to estimate the port impedance of a balanced dipole antenna, and it cannot be used to calculate the characteristic impedance of microstrip lines with one arm. Thus, it is still a problem on measuring and obtaining 50 Ω characteristic impedance of embroidered microstrip line. Therefore, taking the reflection coefficient as an intermediate variable, this work proposes to use return loss [Formula: see text] to derive the expression of the characteristic impedance of microstrip line. Combined theoretical calculation with experimental testing on characteristic impedance of the fabric-based microstrip line, the expression of the characteristic impedance was verified. Then, the expression of the characteristic impedance of microstrip line was used to calculate the characteristic impedance of embroidered microstrip line and determine its equivalent substrates. The results show that the fabric embroidered with a single-layer conductive strip is a part of its equivalent substrate, and the fabric embroidered with a double-layer conductive strip is not a part of its equivalent substrate.

A consensus based adaptive virtual capacitor control strategy for reactive power sharing and voltage restoration in microgrids

In the islanded microgrid, virtual synchronous generator (VSG) control can solve the problems of insufficient damping and low inertia of the system. However, reactive power among distributed generation (DG) units controlled by VSG scannt be shared according to capacity due to the mismatch of line impedance, and the bus voltage can be significantly below the rated value due to the influence of droop control and line impedance. In this paper, an adaptive virtual capacitor control strategy (AVSSC) based on consensus is proposed to solve this problem. The strategy ensures the accurate sharing of reactive power among VSGs and adjusts the estimated bus voltage to the rated value by paralleling virtual capacitors. The voltage estimates used in AVSSC are obtained by the proposed discrete dynamic consensus algorithm (DDCA). The algorithm can obtain the average value of the local voltage estimates of all VSG units to eliminate the limitation of local information and the influence of accidental factors on voltage estimation. The multi-agent consensus theory proves that AVSSC can achieve the expected goal. The simulation results of a microgrid system with four parallel VSGs show that the AVSSC can accurately share reactive power, and the bus voltage error decreases from 0.81% to 0.39%.

The Improved Control Method of Parallel Microgrid Inverters

The parallel of inverters is inevitable in the operation of distributed generation with a Microgrid. However, due to the difference in line impedance between each parallel inverter and the public AC bus in the microgrid, the m available control method is insufficient to overcome the disadvantages such as unbalancing distribution of power, large circulating current, and poor dynamic characteristics, etc., especially when the line impedance difference is large. To conquer the above problems, the paper proposed an improved droop control strategy, in which a differential module is adapted to the droop control to improve the dynamic response. Further, a modified adaptive virtual resistance is proposed, so that the system can maintain high response speed, high stability, and robustness. These can effectively benefit power sharing and circulation suppression of parallel inverters while ensuring excellent dynamic characteristics of the system. Finally, the effectiveness of the improved control method is verified by the simulation results.

Analysis and Design of Dual-Polarized Millimeter-Wave Filtering Magneto-Electric Dipole Antenna

A wideband dual-polarized millimeter-wave filtering magneto-electric dipole (ME-dipole) antenna design is proposed based on a transmission line model with multiple open-circuited loads. Based on the transmission line theory, the input impedance of a quarter-wavelength open-circuited transmission line is zero. Thus, a transmission line terminated with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> open-circuited loads has <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> transmission zeros. Inspired by this conclusion, the proposed antenna structure is developed which consists of three parts: the microtrip feedlines, the ME-dipole radiator and a printed branch structure. The former three parts can be regarded as three open-circuited loads of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> -stub-loaded transmission line model while the last part is utilized for bandwidth improvement. By optimizing the length parameters of these three parts, three antenna radiation nulls can be generated as predicted. For verification, a dual-polarized antenna is implemented. Measurement results show that the proposed antenna has an operation bandwidth of 42.1% and an average realized gain of 7.5 dBi. In addition, it has three controllable radiation nulls and a better than 16 dB out-of-band suppression level. Above features make the proposed antenna a good candidate for 5G millimeter-wave (mm-wave) applications.

Performance evaluation of planar dipole antenna for smart home applications

In a Smart Home wireless module, the antenna generally occupies one-third of the total circuit advances in the Internet of Things (IoTs). Dipole antenna comes in various shapes, but the planar antenna is the most suitable and attractive design for the IoTs application in Smart Homes because it is smaller in size and has a thin profile, making it suitable for mounting on portable equipment. In this research, two antennae, Meandered Dipole and Wideband Planar Antenna, were designed using Advance Design System (ADS) software on a PCB size of 18.8 mm × 43.2 mm, FR4 substrate with 4.6 dielectric constant and 0.8 mm thickness using copper metal as the conducting element. The transmission line has designed width of 1.25 mm, resulting in a typical line impedance of 50 Ω. A comparison of the analysis of simulation and measurement results from feeding port 1 of the Meandered PIFA Antenna shows a better performance of 95.43% efficiency with a gain of 2.54391dBi and a return loss of −24.49 dB at resonant frequency of 2.4 GHz than that from feeding port 2 whose efficiency was only 73.99%. Whereas, the wideband planar antenna shows an average bandwidth of 93.91% from 1.3 to 2.4 GHz. This range covers the GPS applications, the 2.4 GHz ISM band, and the general WCDMA and the LTE 3GPP bands useable for smart home and IoT applications. The proposed antenna provides low power operation, extended range and compact, cost-effective designs to support vendor's customers, and make quality of life smarter and more economical with the use of the smart home device.

A 0.33–2.61-GHz Rectifier With Expanded Dynamic Input Power Range Using Microstrip Impedance Compression Circuit

In this letter, an ultra-broadband rectifier with expanded dynamic input power range (IPR) for both wireless power transfer (WPT) and radio frequency energy-harvesting (RFEH) is proposed and analyzed. Expanded dynamic IPR and broadband impedance matching are realized by utilizing a microstrip transmission line impedance compression circuit (MTLICC) with the topology of the paralleled voltage doubler. A proof-of-concept prototype shows a dynamic IPR of 8.5–23.5 dBm, a frequency range of 0.33–2.61 GHz (fractional bandwidth of 155%), PCE is greater than 50%, and a peak PEC of 79.7% (achieved at an input-power level of 19 dBm). The measurement results are in good agreement with the simulation. Covering most 3G/4G/5G/ISM frequency bands, this design is promising for RF power transmission and energy harvesting in the age of the Internet of Things systems.