High Inrush Currents Research Articles

The Design and Construction of Overcurrent Soft Starting on ESP32 Microcontroller Based Water Machine

The advancement of household water pump technology utilizing induction motors provides numerous benefits, such as efficiency and low cost, but also faces challenges like high inrush current. This study demonstrates the necessity of voltage reduction methods to address high inrush currents that can impact home electrical systems. Testing reveals that the device's error percentage is 0.31%, indicating good performance. The DHT22 and PZEM sensors operate optimally in detecting temperature and current, and controlling relays and water pumps according to the specified thresholds, achieving a 100% system success rate. These results confirm that the system operates as expected according to the specifications.

Single source self balanced switched capacitor based singe phase nine level inverter

Multilevel inverters are becoming increasingly significant due to their ability to efficiently convert power in various applications such as renewable energy systems, electric vehicles (EVs), and industrial drives. The growing need for efficient power conversion in these areas has driven heightened interest in multilevel inverters. High inrush current is required for numerous applications, including variable frequency drives, single-phase or three-phase machine drives, locomotives, electric vehicles. However, managing this inrush current is crucial to prevent damage to the power source and other connected equipment, as well as to ensure smooth and reliable operation. The solution for this is to provide isolation between load and source. The proposed single phase switched capacitor multilevel inverter possess the feature of virtual isolation between the load and the source. This topology consists of a switched capacitor cell network and a multilevel inverter. In this work, a simplest architecture is used for the MLI section to reduce the number of switches. The MLI section consists of only eight switches. Although the switched capacitor network in this topology consists of a higher number of switches, the switches in the network carry only very low current, resulting in negligible losses. Additionally, the switched capacitor network is highly modular in nature. The proposed single-phase inverter can be converted to a three-phase multilevel inverter (MLI) by connecting identical units in each phase, with the reference sinewave signal for the pulse-width modulation technique derived from the corresponding phases. Consequently, this proposed topology is suitable for both low-power and high-power applications. This work demonstrates that self-voltage balancing of the level capacitors can be achieved without the need for auxiliary components.In this design, the level capacitors act as the source to the load and are charged through switched capacitors. The voltage THD in the suggested work is less than 5%, which is in accordance with IEEE 519 standards. High voltage gain, better load, and line regulation, are other significant advantages of this novel topology. Another feature of this work is simplicity in design and can be easily extended to higher voltage levels. Comprehensive simulation and experimental results are provided to validate the precise performance of the proposed multilevel inverter

A new‐high efficiency non‐isolated DC‐DC converter with combination of step‐up techniques

SummaryIn this paper, a new high‐step‐up DC‐DC converter without any coupled inductors or transformers is introduced. The structure of the introduced converter consists of two boost techniques, namely, switched inductor and switched capacitor, used simultaneously. The drawbacks of each technique are mitigated according to the proposed structure and the introduced control method. Therefore, the main contribution of the introduced converter is its ability to use boost techniques while avoiding high input current ripples and inrush currents in the path of semiconductor devices. Thus, there is no need for an auxiliary inductor. Additionally, the number of required components is low, and it benefits from a common ground, which are advantages of this converter in terms of economy and reliability. Another advantage is the high efficiency of the proposed converter in comparison with recent topologies, making it suitable for renewable energy applications such as photovoltaic (PV) systems and fuel cell applications. The proposed converter has been implemented in a laboratory to verify its performance. It operates at 94.51% efficiency with a 200 W output power, a 40 kHz switching frequency, a 40 V input voltage, and a 240 V output voltage.

Capacitor Switching Techniques

Capacitance switching applications involve not only interrupting capacitive currents, but also the energizing of capacitor banks, cables and overhead lines. The interruption of a capacitive current can cause dielectric problems for the switching device. The high inrush currents can cause damage to the capacitors of the capacitors bank and to weld the contacts of the switch together. The problems of the capacitive inrush currents and ways to reduce the magnitude of the inrush current, have been chosen for analysis in this paper.

Voltage Disturbances and Inrush Current of DC Power Supplies

The potential damaging effects of high inrush currents occurring after power quality disturbances on switch-mode dc power supplies (SMPS’) have been reported, but have not been studied in detail. This paper presents a new analytical model for the accurate representation and calculation of inrush currents of low-power SMPS devices. This model is verified against previously developed circuit-based simulation model and compared with the only other analytical model available in existing literature. The developed analytical model is also used to investigate device protection co-ordination, in order to demonstrate two important effects of high-inrush current: nuisance tripping of protection and damage of internal SMPS components. Key words. Inrush current, load modelling, analytical representation, switch-mode dc power supply (SMPS), power quality disturbance, short interruption, voltage sag

A Modular Magnetic Linked Converter Station for Offshore Power Transfer Through HVDC Link

This paper proposes a modular magnetic linked converter station (CS) for offshore power transfer through a high voltage dc (HVDC) link. The proposed converter station can collect medium voltage ac and dc power simultaneously and transform the power to HVDC suitable for offshore power transmission. The proposed CS adopts multiple half-bridge (HB) converters to form a front-end interface that can collect both medium voltage ac and dc power. Moreover, several high-frequency magnetic linked multiport converters (MLMCs) are employed in the CS to isolate and step up the voltage. The MLMC is operated at a unity step-up voltage ratio which matches the turn ratio in multiple windings shared by a common magnetic link. This condition facilitates minimum current stress on the switches and inherent soft-switching operation. In the proposed CS, the hard switching operation of the front-end HB converters does not affect the switching condition of the MLMCs. Furthermore, the application of the switched capacitor-based HVDC converter enables discretized dc-link capacitor arrangement to limit high inrush current under dc fault. A controller structure is also proposed for the CS to balance the electrical parameters. The results from a simulation study of the proposed CS, both in steady-state and dynamic conditions, show that the proposed CS performs satisfactorily with the proposed controller, which is validated by the laboratory scale experiment.

Improving the performance of differential relays in distinguishing between high second harmonic faults and inrush current

Differential relays have faced challenges such as failure to detect the inrush current, inappropriate performance in high second harmonic faults, and maloperation when the current signal becomes noisy. Therefore, in this paper, a new method is proposed to tackle these challenges. The proposed method is based on the calculation of the distance between the sampled data obtained from the compressed sensing theory (CST). In this method, first the currents on both sides of the power transformers are sampled and a single signal is formed. In the next step, the obtained signal will be compressed by the proposed CST algorithm. Since Discrete Fourier Transform Matrix (DFTM) is used to implement CST, the output of the algorithm will be a signal consisting of complex numbers. Using the imaginary part of this signal, a detection index will be proposed. Choosing a threshold value for this index enables the proposed method to differentiate between types of faults and inrush currents. The proposed method has been implemented on DIgSILENT and MATLAB software. The results prove that the proposed method has the ability to quickly detect all types of faults, including faults with high second harmonics. In addition, this method is immune to signal noise.

Transformer Inrush Current Mitigation Techniques for Grid-Forming Inverters Dominated Grids

The use of inverters-based resources (IBRs) is rising rapidly in power networks due to increased renewable energy penetration. This requires revisiting of classical network operation standards. For instance, high transformer energization inrush current has been studied extensively under the classical network paradigm. Whereas this paper investigates transformers' energization techniques in the context of inverters dominated grids, where inverters with limited short-circuit current are expected to utilize their grid-forming capabilities for black-start. Common transformer energization techniques such as controlled switching and soft energization are first analyzed with a new perspective aiming to assess their feasibility when used with grid-forming inverters and existing network assets. Parameters influencing soft energization voltage ramp-up time ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{ramp}$</tex-math></inline-formula> ) are investigated, and a new <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T_{ramp}$</tex-math></inline-formula> estimation framework for transformer energization from IBRs is introduced. Due to the variability of available point-on-wave circuit breakers (CBs) in distribution networks, controlled energization using single-pole and three-pole CBs is investigated for various configurations and their application limits are identified. A comprehensive case study is then presented using a test network with multiple transformers to benchmark the performance and requirements of each technique when the network is energized from an IBR, followed by a set of practical recommendations.

Reduction of Starting Current in Large Induction Motors

Large induction motors can have a high inrush and run-up current during starting, often up to ten times the rated current. In weak supplies, this could be a problem, causing system stability issues and the voltage to dip below acceptable levels. In islanded systems, the capacity could be pulled below its maximum. There are several different starting methods possible, but they are often only suitable for smaller machines. One method not investigated is the use of parallel capacitor compensation during the starting because large induction motors are very inductive during the starting sequence, so that supplying reactive power may be more effective than supplying energy. This paper first investigates several different induction motors with increasing size and assesses their compensation requirements in terms of the reactive power requirement during starting. It is shown that they do generally become more inductive as they increase in size. It is illustrated, using simulations, that using parallel capacitors during starting can significantly reduce the starting current. The concept is tested using a small experimental motor. Series inductors are added to the motor to make it more inductive and look more like a larger machine. The experimental results confirm that the method works. It is also found that the parallel capacitors require series filters to prevent harmonic current, and these can be realized using inductors in series with the compensation capacitors. Point-on switching using solid-state relays was tested, and these can reduce the transient switch-on current over the first voltage cycle.

Renewable energy based charging station with power quality features for multi EV spots using maximum correntropy sub-band adaptive technique

ABSTRACT Here, a photovoltaic (PV)-based multi-spots electric vehicles (EVs) charging station (CS) is presented by using maximum correntropy criteria with affine projection sub-band adaptive filter (MCC-APSAF). The presented CS also includes the features of power quality at nonlinear loads connected at the point of common coupling (PCC). This CS comprises a battery bank, multi-EV batteries, and ultra-capacitor (UC) charging spots. However, a dramatic increase of EVs and charging stations in the existing grid has raised the issues related to the harmonics, voltage fluctuations, reactive power, and burden on the grid. These issues are addressed in the presented charging station. Moreover, the ultra-capacitor can provide fast charging, which minimizes the high inrush current of the CS. Therefore, the batteries during the high EVs load at the CS are protected by the ultra-capacitor spots. To stabilize the DC bus voltage, separate cascaded controllers for ultra-capacitor and battery spots are used. The CS shows the multifunctional capabilities, which include PV array to grid (PV2G), PV array to the EV battery (S2EVB), EV battery to grid (EVB2G), and PV array to home (PV2H) when PV source is present. The various EVB2G, G2EVB, battery to home (EVB2H), and grid to home (G2H) behaviors are also presented. This CS shows good dynamic efficacy under insolation variation, EVB2G, G2EVB modes, load throw, and load reconnection operations. The grid current THD using the proposed current control is 1.44%, which is in accordance with the IEEE-519 standard. Moreover, the maximum power obtained from the PV generation is 63 kW, which is successfully distributed in the battery bank and six EV batteries (30 kW), in nonlinear load (14 kW), and the rest of the power is injected to the grid (29 kW). This CS is simulated in the MATLAB/Simulink library and test results are obtained using the experimental workbench with OPAL-RT (OP5600) in the laboratory.

Variable Speed Drive DC-Bus Voltage Dip Proofing

This paper proposes a power electronic module that uses a switched capacitor for retaining the integrity of the dc-link voltage of a variable speed drive (VSD) during a 0.2 s short-term power interruption (STPI). Ride-through was achieved through switched capacitor onto the dc bus. However, this technique presents a challenge of the high inrush currents during a ride through compensation. In this work both analytical and experimental investigations were conducted in order to reduce the in-rush currents and its impact on the performance of the VSD during the STPI. Inrush peak currents were reduced by approximately 90%. Experimental results showed torque pulsations of 12.8% and 14.3% at the start and end of dc-link voltage compensation, respectively. A method for sizing the switched capacitor and the inrush limiting resistors is proposed. This methodology is based on the use of readily available nameplate information of the VSD and the electric motor. The proposed module can be retrofitted to existing VSDs that are based on v/f control.

Automatic Classification of Winding Asymmetries in Wound Rotor Induction Motors Based on Bicoherence and Fuzzy C-Means Algorithms of Stray Flux Signals

Wound rotor induction motors are used in a certain number of industrial applications due to their interesting advantages, such as the possibility of inserting external rheostats in series with the rotor winding to enhance the torque characteristics under starting and to decrease the high inrush currents. However, the more complex structure of the rotor winding, compared to cage induction motors, is a source for potential maintenance problems. In this regard, several anomalies can lead to the occurrence of asymmetries in the rotor winding that may yield terrible repercussions for the machine's integrity. Therefore, monitoring the levels of asymmetry in the rotor winding is of paramount importance to ensure the correct operation of the motor. This work proposes the use of bicoherence of the stray flux signal, as an indicator to obtain an automatic classification of the rotor winding condition. For this, the Fuzzy C-Means machine learning algorithm is used, which starts with the bicoherence calculation and generates the different clusters for grouping and classification, according to the level of winding asymmetry. In addition, an analysis regarding the influence of the flux sensor position on the automatic classification and the failure detection is carried out. The results are highly satisfactory and prove the potential of the method for its future incorporation in autonomous condition monitoring systems that can be satisfactorily applied to determine the health of these machines.

Residual flux impact in controlled switching of HVDC converter transformer

Abstract Converter transformers are an interface point of HVDC frameworks and are basic hardware from activity and reliability view point. Converter transformers are turned off intentionally under planned support and un-deliberately during fault conditions. Random energization of HVDC Converter transformer delivers high inrush currents due to core saturation asymmetries and endanger equipment health. In this paper, charging approach has been proposed. By utilizing point on wave exchanging for moderation of charging drifters during charging of 888 MVA 400/325 kV Converter Transformer of ±800 kV HVDC Sub-station. The proposed procedure has been applied on HVAC electrical Circuit Breaker furnished with Pre-Insertion Resistor considering diverse degree of residual flux. Performance of proposed philosophy has been affirmed by field tests and reproduction in PSCAD programming package and is found very viable. Near investigation is done in this paper and shows that with the use of proposed system, the switching transient during stimulation and field tests of coupled three phase converter transformers is decreased to worthy level.

Switched capacitor based single DC source boost multilevel inverter (S2-MLI) featuring isolation based soft charging with minimum device count

Abstract Multilevel inverters (MLIs) have formed a new wave of interest in research and industry. Switched capacitor-based multilevel inverters are used to avoid the need for multiple separated DC sources compared to cascaded MLIs. However, the inclusion of several capacitors creates problems such as high inrush current, voltage imbalance. To avoid these drawbacks, this paper proposes an isolation-based scheme by using a flyback converter in the switched capacitor multilevel inverter. Further, the overall topology provides step-up AC voltage across the load from a single DC source with fewer power switches. To generate a step-up five-level voltage across the load, switched capacitor-based multilevel inverter needs six power switches and only one capacitor. To get the appropriate switching operation to generate the NL-levels, phase disposition pulse width modulation (PD-PWM) has been developed. The extended nine-level S 2 -MLI is also discussed in this paper under different conditions as change in input source voltage and dynamic load change. Moreover, to prove the superior performance of switched-capacitor single DC source multilevel inverter (S2-MLI), comparative analysis with existing single DC source MLI has been performed. The effectiveness and feasibility of the proposed topology are tested with varieties of loads by simulation using Matlab/Simulink. To validate the simulation results, hardware implementation has been done of five-level S2-MLI considering resistive and motor load by using DSpace 1103 controller.

Melting Pattern of Vacuum Interrupter Contacts Subjected to High Inrush Currents at High Frequencies

One important aspect in capacitor switching concerns the high inrush current during the energizing of the capacitor. For vacuum interrupters, it is assumed that the modification of the contact surface due to high inrush currents has the highest impact on the current breaking performance. One peculiarity of capacitor switching is the high rate of switching operations easily achieving 1000 operations in a couple of years. Two vacuum breakers were therefore operated up to 1000 times in a simple test circuit simulating the making of high inrush currents. According to standards, peak and frequency of inrush currents are 20 kA and 4250 Hz for back-to-back capacitor switching, or around 5 kA and 400 Hz for single bank switching. The range of inrush currents was extended here to peak currents up to 60 kA and frequencies up to 24 kHz. Peak current and frequency have an important impact on radius and current density of the inrush current arc, and thus on the energy deposited under the arc roots. Under the conditions prevailing here, the whole surface of the contacts exhibits a uniform melting pattern with the depth of the solidified melt being less than 1 mm after 1000 operations. It is assumed that the arc moves on the contact surface driven by the radial magnetic forces generated by this kind of contact and distributes the arc energy all over the contact surface. The inrush current integral ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ICI</i> ) might be a measure of the available energy for contact melting or erosion. However, since the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ICI</i> has no relation to the arc current density, it is only representative for a particular melting pattern of the contact surface if frequency and peak inrush currents are varied in a limited range.

Determination of the saturation curve of power transformers by processing transient measurements

The sudden energization of large power transformers may lead to the saturation of the magnetic core and induce resonant overvoltage on weak networks due to low frequency high module inrush currents. The magnetization curve of the transformer and the value of its air-core inductance play a key role in the constraints that can be applied to the equipment due to the switching. The method set out in that document allows to identify the saturation curve of three-phase power transformers from measurements recorded during switching transients.

A benchmark of different starting modes of a passive Fuel Cell/Ultracapacitor hybrid source for an electric vehicle application

A benchmark of different starting modes of a passive Fuel Cell (FC)/Ultracapacitors (UCs) hybrid source is presented. Passive hybridization consist to directly connect the FC and the UC without power electronics. Compared with active sources, passive hybridization presents some advantages: lower volume and weight, ease of implementation, and lower cost. However, the power distribution among the sources is no longer controllable. Additionally, the FC–UC passive hybrid source’s start-up could lead to high inrush currents and faster FC degradation. A FC–UC passive hybrid source start-up is evaluated by simulations and experimentally. Three starting modes for an automobile application are considered: progressive starting, short circuit, and using a resistive pre-charge device.

Wind Power Integration and Its Impact on Power Quality - A Didactic Approach

This paper presents a model of a wind power system integrated with realistic power system, with intention of using it in addressing power quality issues in relations to grid codes during steady-state operation transient-state operation i.e., presence of grid fault events. For that case, a didactic approach of the normal performance of power systems due to the connection of fixed-speed wind turbine with induction generators is used. A study of integrating wind farms will be presented, including the incidence of high inrush current due to switching capacitor banks, out-rush current and voltage sags due to nearby three phase faults. As mandatory for the grid codes regulation, the incidence on the power quality at the point of common coupling is analyzed too. As a result of the contingency study, it will be shown that capacitors bank and fault current limiter can help the wind farm to ride-through a fault.

Inrush Current Control of High Power Density DC–DC Converter

This paper presents a complete mathematical design of the main components of 2 kW, 54 direct current (DC)–DC converter stage, which can be used as the second stage of the two stages of alternating current (AC)–DC telecom power supply. In this paper, a simple inrush current controlling circuit to eliminate the high inrush current, which is generated due to high input capacitor at the input side of the DC–DC converter, is proposed, designed, and briefly discussed. The proposed circuit is very easy to implement in the lab using a single metal–oxide–semiconductor field-effect transistor (MOSFET) switch and some small passive elements. PSIM simulation has been used to test the power supply performance using the value of the designed components. Furthermore, the experimental setup of the designed power supply with inrush current control is built in the lab to show the practical performance of the designed power supply and to test the reliability of the proposed inrush current mitigation circuit to eliminate the high inrush current at initial power application to the power supply circuit. DC–DC power supply with phase shift zero voltage switching (ZVS) technique is chosen and designed due to its availability to achieve ZVS over the full load range at the primary side of the power supply, which reduces switching losses and offers high conversion efficiency. High power density DC–DC converter stage with smooth current startup operation, full load efficiency over 95%, and better voltage regulation is achieved in this work.

A Modified Transient Current Limiter to Mitigate Energization Inrush Current in Wind Turbine Transformers

Energization of wind turbine transformers (WTTs) in wind power plants (WPPs) leads to high transient inrush current, which imposes high mechanical and thermal stresses on transformer windings and voltage sag problems at grid connection point (GCP). Therefore, to solve these problems, the inrush current should be suppressed during the energization time. The current research presents a modified transient current limiter (MTCL) for suppressing WTTs’ inrush current. Two types of MTCL such as resistor type (R-type) and reactor type (L-type) are considered for this purpose. To investigate the efficiency of the MTCL, a WPP includes five wind turbines which are simulated by PSCAD/EMTDC software. The simulation results reveal that the MTCL is an effective means for suppressing the WTTs’ inrush current and mitigating GCP voltage sag during energization. Besides, to show the effectiveness of the proposed MTCL, the performance of the MTCL is compared with the conventional TCL through simulation.