Voltage Oscillations Research Articles

Design of Digital Control System for DC/DC Converter of On-Board Charger

Vehicle charging power supply is widely used because of its small size and portability. Aiming at the problems of slow dynamic response, subharmonic, oscillation and limited soft-switching range of phase-shifted full-bridge DC/DC converter, the paper proposed a modified PSFB converter by introducing clamp diodes at the primary side of the transformer to suppress voltage oscillation of the transformer’s secondary side. Also, digital peak current phase-shifting control and slope compensation are introduced to avoid subharmonic oscillation. Dynamic dead-time control technology introduced adjust the dead-time in different load ranges through the dead-time adjustment subroutine. Finally, an experimental platform of on-board charging phase-shifted full-bridge DC/DC converter is established. The experimental results show that the power supply eliminates subharmonic oscillation, achieves a wide range of soft-switching, improves the dynamic performance and antiinterference ability of the system, and optimizes the power efficiency.

Electric drive systems with long feeder cables

Electric drive systems with long feeder cables connecting inverter and machine are used for oil exploration, mining, remote operated vehicles, industrial, and aerospace applications. Though this topology has the advantage of providing a better operating environment and easier serviceability for the inverter if the machine is located in an inhospitable and inaccessible environment, it does come with its own drawbacks. Steep-fronted switched voltages and cable-machine surge impedance mismatch can lead to high-amplitude, high-frequency (HF) voltage oscillations along the feeder cable, at the machine terminals, and throughout the machine's stator windings. These effects can cause high-electromagnetic interference, corona discharge, insulation failure in the feeder cable and machine's stator windings, common-mode, differential-mode, and bearing currents. This study discusses the HF issues relating to electric drive systems with long cable feeders. HF models for feeder cable and machine to analyse these phenomena are presented. The effects on long feeder cable loading on inverter switching characteristics are discussed. Methods to mitigate high-amplitude and HF oscillations in such systems are shown.

Continuous Nonsingular Terminal Sliding Mode Control of DC–DC Boost Converters Subject to Time-Varying Disturbances

DC-DC converters work as one of the crucial components in DC microgrid intergraded power systems. In this brief, the robust output voltage regulation problem of DC-DC boost converter system is addressed by using a continuous nonsingular terminal sliding mode control (CTSMC) technique based on finite-time disturbance observer. By integrating the disturbance estimations into the controller design, an improved sliding mode control (SMC) approach is developed to achieve better voltage tracking performance. The proposed control method admits the properties of fast transient responses, strong suppression ability against time-varying disturbances and small steady state oscillations of output voltage. Experimental results in the presence of both load variations and supplied voltage fluctuations are provided to validate the effectiveness of the proposed algorithm.

Optimal designing of static var compensator to improve voltage profile of power system using fuzzy logic control

The unbalanced and nonlinear characteristic of many loads connected to the power system can cause power quality problems, which in turn affects other consumers. Electric arc furnaces (EAF) are among the loads that cause major problems for system power quality. The use of static var compensator (SVC) is a way to reduce power quality problems caused by EAF. Since precise quantification of the SVC susceptance function can greatly influence the optimization of the reactive power, in this paper proposed using of a fuzzy logic controller to optimize the susceptance function to further improve the voltage profile and reduce SVC capacitance. The results from simulations show that the SVC based fuzzy method optimally determines the coefficient of the susceptance function. The results show that the proposed method with the proposed method has good performance in reduction of harmonic currents and improving the voltage profile of the system. So, the results clear that in case of EAF load, the SVC is capable of rapidly compensating its effect and improve the system power quality. By maintaining the bus voltage and eliminating voltage oscillations, the active power received is quickly stabilised and power oscillations are removed. Thus, power quality problems of EAF application is eliminated with application of optimized SVC based fuzzy method. In addition, the performance of the proposed method compared to mathematical methods in previous studies has been evaluated, which presents superiority of the proposed method in reducing voltage oscillations and reducing harmonic currents.

Conceptual Design of the FCC-hh Dipole Circuits With Integrated CLIQ Protection System

The Future Circular Collider (FCC-hh) project is a conceptual study whose goal is to design the successor of the Large Hadron Collider, increasing the collision energy from 14 to 100 TeV. The energy stored in the 16-T superconducting dipole magnets and the length of the sectors composing the 100-km FCC tunnel are considerably larger than those in present accelerators. This means that the energy stored in the FCC-hh dipole circuit is likely to be much higher than that in existing superconducting circuits. In the case of magnet quenches or faults, the circuit needs to be protected, i.e., its energy needs to be rapidly dissipated without inducing excessive voltages in the magnet chain. This article proposes a conceptual design for the FCC-hh dipole circuit, which satisfies the constraint of the maximum allowable voltage-to-ground and fulfills additional requirements related to the FCC-hh operation and tunnel layout. A compromise among the considered requirements leads to a relatively simple circuit layout and a large number of circuits for the entire machine. The behavior of the proposed circuit during the critical fast power abort phase is simulated through a numerical model, which covers the electrical circuit domain and the electrothermal magnet domain. Each FCC-hh dipole magnet is protected by means of the coupling-loss-induced quench (CLIQ) protection system, which also acts at the circuit level. The simulations predict severe voltage oscillations in the FCC-hh dipole circuits that may pose a problem for the quench detection system. The simulations also show that the severity of the oscillations is not due to the presence of CLIQ. This protection system can be integrated into the proposed circuit layout and represents an effective protection system for the entire string of FCC-hh dipole magnets.

SCA Based Interval Type-2 Fuzzy PID Controller for Solar MPPT

In this publication section, novel interval type-2 fuzzy-PID controller (T2FPID) based Maximum Power Point Tracking (MPPT) is implemented in proposed a standalone photovoltaic (PV) system, type-1 fuzzy-PID controller (FPID), and PID controller with strategic control of online set point tracking in association with DC-DC boost converter is enforced in PV system to track maximum power point (MPP) in solar PV system is depicted. The opted controllers are appropriately composed by picking sine-cosine (SCA) algorithm. The proposed T2FPID based MPPT technique is espoused to dig out maximum power under certain circumstances of temperature and irradiance. System performance is enhanced by the act of T2FPID controller. The maximum output power, voltage & current, duty cycle for DC-DC boost converter is relevantly controlled by the novel T2FPID controller tuned by SCA algorithm. The T2FPID based MPPT technique is authenticated by comparing it by P&O based technique. Finally, it is scrutinized that, the supremacy of intended controller is proved over conventional P&O technique, conventional PID & T1FPID controller; conceding the oscillation, time response, settling time and maximum values of voltage, current & power of the solar system. Robustness analysis is performed by varying the irradiance and temperature partly keeping one parameter constant. The proposed work is further validated on OPAL RT system.

Decoupling Capacitance Enabled Water Pumping System using Photovoltaic System

A two-stage PV water-pumping system architecture is represented in this paper. In contrast with other alternatives available in the literature, the electronic drive does not exploit batteries to accomplish energy decoupling, neither large electrolytic capacitors in between stages. Although these two design decisions respectively minimize environmental impacts and increase the converter’s expected lifetime, they also bring about considerable control difficulties. More specifically, the DC link stiffness is reduced and thus large voltage oscillations may occur. In order to overcome this problem, a nonlinear controller interconnection between the individual compensator of each stage is created to account for the low capacitance. Simulations and experimental results demonstrate the effectiveness of the method in stabilizing the DC-link voltage under sudden solar irradiation changes. The final converter was deployed in a remote rural community in Guinea-Bissau for crop irrigation purposes. Despite the harsh conditions such as high temperatures and sea breeze, in situ results were satisfactory and validated the system robustness

Decoupling Capacitance Enabled Water Pumping System using Photovoltaic System

A two-stage PV water-pumping system architecture is represented in this paper. In contrast with other alternatives available in the literature, the electronic drive does not exploit batteries to accomplish energy decoupling, neither large electrolytic capacitors in between stages. Although these two design decisions respectively minimize environmental impacts and increase the converter’s expected lifetime, they also bring about considerable control difficulties. More specifically, the DC link stiffness is reduced and thus large voltage oscillations may occur. In order to overcome this problem, a nonlinear controller interconnection between the individual compensator of each stage is created to account for the low capacitance. Simulations and experimental results demonstrate the effectiveness of the method in stabilizing the DC-link voltage under sudden solar irradiation changes. The final converter was deployed in a remote rural community in Guinea-Bissau for crop irrigation purposes. Despite the harsh conditions such as high temperatures and sea breeze, in situ results were satisfactory and validated the system robustness

The Influence of Parasitic Components on LLC Resonant Converter

In recent years, the LLC resonant converter has been widely used in DC–DC conversion applications. However, the parasitic components of the LLC resonant converter have a significant impact in practical applications, such as influence on the conduction loss and the soft-switching of power devices, the voltage oscillation across rectifier diodes, the unregulated output voltage at light load condition and so on. It is hard to analyze the higher-order circuits by the conventional analysis methods. Focusing on the operational principle of the LLC converter with parasitic components, the differential equation model is presented and solved by the numerical method in this paper. The simulation results verify the correctness of the theoretical analysis. The causes of two different frequency oscillations and the voltage spike are clarified. The design considerations and a specific example of the LLC converter are given. The experimental results are consistent with the simulation results, and the soft-switching of primary-side switches can be achieved in the prototype.

Electromagnetic wave propagation in a fast pulse line ion accelerator.

The pulse line ion accelerator (PLIA) is a low-cost accelerator concept originally designed to accelerate heavy ions. Our group has been investigating the use of PLIA to accelerate light ions and believe a multi-stage PLIA could be useful for short half-life PET isotope production. The goal of this work was to develop a single prototype fast PLIA structure and demonstrate electromagnetic wave propagation using a high-voltage pulser. A 1.6m fast PLIA structure (wave speed>107 m/s) was constructed along with a high-voltage, sinusoidal pulse generator. The latter uses capacitive voltage doubling and spark gap switching. A step-up transformer couples voltage from the pulser to the PLIA coil. Voltage measurements on the coil were made in air using a high-voltage resistive probe, while capacitive probes placed along the length of the PLIA were used to measure wave propagation with the PLIA structure filled with transformer oil. Voltage measurements acquired on the primary and secondary coils of the transformer coupler in air demonstrated a peak-to-peak voltage step-up of 4.2 relative to the pulser DC charging voltage. The maximum voltage time-rate-of-change on the PLIA coil was 0.76×1013 V/s. Capacitive probe measurements indicated voltage oscillations on the PLIA coil with half-period equal to 43±0.9ns and wave speed (with oil) of 1.2×107 m/s. Average and peak accelerating gradients were conservatively estimated to be 0.44 and 0.60MV/m, respectively, with a charging voltage of 55kV. Wave propagation was demonstrated at these gradients without flashover at a vacuum pressure of 9×10-6 Torr. Submerging the pulser in oil would allow for charging voltages up to 150kV and produce accelerating gradients >1.2MV/m. Use of a multi-stage, fast PLIA for light ion acceleration could provide a low-cost complement to cyclotrons for the production of short half-life isotopes used for PET imaging, including carbon-11, nitrogen-13, oxygen-15, and fluorine-18.

A Carrier-Based Fault-Tolerant Control Strategy for T-Type Rectifier With Neutral-Point Voltage Oscillations Suppression

This paper proposes a carrier-based fault-tolerant control strategy for T-type three-level rectifier with neutral-point (NP) voltage oscillations suppression when an open-circuit fault occurs. The proposed fault-tolerant control is demonstrated by dividing fault into two conditions: the faulty condition of outer switches and inner switches. In the case of outer switches open-circuit fault, the requirement to maintain the normal operation with sinusoidal currents is demonstrated. Meanwhile, in order to suppress the NP voltage oscillations, a hybrid NP voltage control strategy, which is implemented by adding a compensation value to the reference voltage, and a dc bias are used. In the case of inner switches open-circuit fault, the fundamental period of the input current is divided into two areas: normal half-cycle and abnormal half-cycle. In the abnormal half-cycle, the reference voltage of the faulty leg is compared with a single carrier. In addition, a compensation value is added to the reference voltage to suppress the NP voltage oscillations. While in the normal half-cycle, the hybrid NP voltage control strategy and the dc bias are applied. The feasibility and performance of the proposed tolerant control are illustrated and verified through the simulation and experimental results.

PMU-Based Monitoring and Mitigation of Delayed Voltage Recovery Using Admittances

This paper analyzes the delayed voltage recovery phenomenon by simplifying the Western Electricity Coordinating Council (WECC) composite load model using the load admittance and the thermal relay dynamics. From this analysis, a closed form expression approximating the recovery time is derived and the key load parameters impacting the behavior of voltage recovery are identified. A monitoring scheme based on the measured load admittance is then proposed to detect the onset of stalling, even in the presence of voltage oscillations, and estimate the duration of the delayed voltage recovery. A mitigation scheme utilizing smart thermostats and offline learning is also derived to ensure that the voltage recovers to the pre-contingency voltage within a specified time. Both the monitoring and mitigation schemes only need local measurements at a substation making them promising for online applications. Results for the monitoring and mitigation schemes are described in detail for the IEEE 162 bus system validating the various assumptions used for the analysis and establishing the connection between the delayed voltage recovery phenomenon and load admittance.

Paralleling voltage oscillation forecast method of energy device based on hysteresis curve equation

Power battery is widely used in backup power and new energy vehicles. Many countries have paid more and more attention to the safety of power battery. At present, the battery combination mode of series connection to parallel connection is conducive to the fast combination and unloading of high voltage system energy. It is an effective way for modular design and production of the power battery system. However, the voltage oscillation may appear when the voltage difference exists between the parallel modules. The phenomenon may affect the performance and safety of electric power and electric equipment. The voltage oscillation standard deviations in paralleling with different voltages were analysed, the voltage oscillation distribution map can be drawn. The reasonable parallel voltage range can be obtained by hysteresis curves, which were used to predict the limit of paralleling voltage. Lithium-ion+ battery experiment was carried out and the result shows that the proposed method can predict the large voltage oscillation in battery paralleling, it can ensure the safety of battery module and it provided an effective forecast in paralleling for the new energy power electric system.

Dynamic Properties of Vortex States in Mesoscopic Superconducting Strips with a Temporally Periodic Pinning Landscape

Using a finite-element method to numerically solve the time-dependent Ginzburg–Landau equations, we studied the dynamic properties of superconducting strips with a central, time-dependent, weakened superconducting region. Through our research, we obtained the voltage oscillation as a function of time. Particularly, a multiharmonic voltage oscillation was found in the superconducting strip. With increasing period of pinning potential, the frequency of the voltage oscillation decreases.

Ultra-fast measurement circuit for transient space charge limited current in organic semiconductor thin films

The charge carrier mobility is a crucial parameter determining the device performance for numerous different semiconductor applications. Consequently, an accurate measurement of this quantity is crucial. For this purpose, the transient space charge limited current (SCLC) method is commonly applied and is preferable over, for example, Hall or field effect measurements, as the analyzed current direction is in line with typical device architectures. For the transient SCLC method, a voltage step is applied and the transit time of injected charge carriers is determined using displacement currents. Consequently, the difficulty of this method is the use of an adequate RC time constant for the sample charging, as it needs to be much shorter than the transit time. This parameter generally limits the application of transient SCLC strongly, in terms of obtainable charge carrier mobility or minimum required film thickness. Here, we demonstrate a measurement circuit with a low RC time constant, which works in a wide current range (1 A–0.5 A) and thus allows for significant flexibility in terms of minimum film thickness or detectable charge carrier mobility. The circuit is fast enough to measure, for example, charge carrier mobilities of up to for a 76 nm thick 4,4’,4”-Tris[phenyl(m-tolyl)amino]triphenylamine (MTDATA) layer, without using limited bridge circuitry. For this purpose, a capacitor coupled fast transistor switch generates a voltage step to avoid voltage oscillations and a fast operational amplifier is used for amplification of the voltage over a variable measurement resistor. We demonstrate the circuit working principle by measuring benchmarked MTDATA diodes and discuss its range of application.

A Family of Dual Resonant Switched-Capacitor Converter With Passive Regenerative Snubber

In this article, a step-down switched-capacitor converter (SCC) and a step-up SCC with an integrated passive regenerative snubber (PRS) are proposed based on the Cuk dual resonance core (DRC). The members of the DRC converter family overcome the barrier for SCCs to achieve continuous output voltage regulation. One remaining challenge is the turn-off spikes and oscillations during the switch turn-off transient that cause voltage stress and power loss to the transistor and diode. The proposed integrated PRS eliminates voltage spikes and oscillations across the transistor and diode during the turn-off process. Moreover, zero voltage switching (ZVS) turn-on for the clamped mosfet, zero current switching (ZCS) turn-on for the other mosfet and ZCS turn-off for all diodes are achieved. A comprehensive analysis of the operation principle, conversion ratio curves, component stress, and regenerative power of the proposed converters with regenerative snubbers is given. Furthermore, a performance comparison between the proposed snubber configuration and two conventional methods is given. A 50 V/99.25 V step-up converter prototype of 125 W has demonstrated a peak efficiency of 98.4%. The analysis is verified by both simulation and experiments.

Voltage behavior improvement for proton exchange membrane fuel cell stack suffering fuel starvation

ABSTRACT Fuel starvation severely affects the performance and durability of proton exchange membrane fuel cell stack. In this paper, the individual voltage characteristics of a 40-cell proton exchange membrane fuel cell stack under different load currents were studied in detail. The cell voltage oscillation, plunge and polarity reversal were observed. To alleviate the hydrogen concentration loss, an effective and simple hydrogen supply method, dual-path hydrogen provision (DHP), was proposed. In the proposed method, high-pressure hydrogen could be fed to the stack from the anode outlet in addition to the anode inlet. An experiment with identical conditions was carried out. It was found that the proposed mitigation measure could significantly alleviate voltage degradation and delay the polarity reversal. The overall output performance of the PEMFC stack was improved by 13.7%, and the maximum improvement of the individual cell was 664%. This paper contributes to a better understanding of the voltage behavior of fuel cells under fuel starvation and provides an effective, practical and low-cost migration measure for most of the commercial PEMFC stack.

A High-Performance Embedded SiC Power Module Based on a DBC-Stacked Hybrid Packaging Structure

Silicon carbide (SiC) devices have the advantage of high switching speed. However, the switching speed is limited by the high parasitic inductance which could cause high voltage overshoot, parasitic turn-on, oscillation, and electromagnetic interference (EMI) issues. Thus, the parasitic inductance of the SiC power module has to be reduced for better performance. This paper proposed an integrated half-bridge (HB) power module based on a direct bonding copper (DBC)-stacked hybrid packaging structure. This packaging structure utilizes two DBC substrates to stack together, which form a 3-D power commutation loop. The SiC chips are embedded on the top of the bottom DBC substrate to reduce the thermal resistance. Based on an optimized mutual inductance cancellation design, the proposed DBC-stacked hybrid packaging structure has only 1.8-nH commutation power loop inductance for a 1200-V, 120-A HB power module. Moreover, the geometrical parameters of the laminated power terminal have been analyzed and optimized for the symmetrical current sharing in the multichip paralleled power module. A compact 1200-V, 120-A full SiC HB power module with integrated decoupling capacitors has been fabricated and the dc-link capacitor board, gate drivers can be integrated on the power module compactly. Finally, the static and dynamic characteristics of the proposed module have been tested. The results of double pulse test (DPT) under zero external driver resistor indicate that the voltage overshoot of the proposed module is reduced by approximately 55% compared to the commercial power module, and the total switching energy is only 43% of the commercial module. Moreover, the loss of the 5.5-kW single-phase inverter based on the proposed module is reduced by 28.3% compared with the inverter based on the commercial module under 120-kHz switching frequency.

An Integrated Power Conversion System for Electric Traction and V2G Operation in Electric Vehicles With a Small Film Capacitor

An integrated power conversion system is proposed for electric vehicles (EVs), which consists of a dual active bridge (DAB) dc–dc converter cascaded by a three-phase four-leg (TPFL) dc–ac converter. The integrated power conversion system can realize both vehicle-to-grid (V2G) operation and traction operation for EVs. The large capacitor is avoided in the dc link of the proposed power conversion system. Instead, an active snubber with a small film capacitor is connected to the dc link to suppress the voltage oscillation, which is induced by the removal of the large dc-link capacitor. By designing the phase-shifting control for the primary H-bridge of DAB, a high-frequency pulsating dc-link voltage with zero portions is generated. Setting switching actions of the secondary H-bridge of DAB and TPFL during zero portions of the dc link, the zero-voltage-switching (ZVS) operation is achieved, and the system efficiency can be improved consequently. Therefore, the fixed-switch-moment control strategies, namely, the finite-set model-predictive-control (FS-MPC) and switch-table direct-torque-control (ST-DTC), are proposed to regulate TPFL for V2G operation mode and traction operation mode, respectively. Detailed analysis of different switch states within one half operating cycle is presented. Both simulation and experiment are conducted to verify the effectiveness of the proposed system and control schemes.

Effect of gas flow on the form and characteristics of Glow Discharge

The article is devoted to an experimental study of the effect of gas flow on the characteristics of a glow discharge. The design of the discharge chamber made it possible to change the interelectrode distance a = (2–8) cm. The family of current-voltage characteristics was measured in the following ranges of gas pressure P, its flow rate G, discharge current I and voltage U: P = (4. 7 - 26) kPa, G = (0 – 0.05) g / s, I = (20 - 100) mA, U = (1. 5 – 4. 2) kV. The oscillations of the discharge voltage were recorded with an oscilloscope, the current-voltage characteristic of the discharge was recorded by a two-coordinate recorder. The current-voltage characteristics had a negative differential resistance. The influence of the interelectrode distance on the type and quantitative relationships of these characteristics is analyzed. When gas is pumped through the discharge chamber, the current-voltage characteristics do not change qualitatively, but the discharge voltage and the steepness of the characteristics increase compared to a discharge without gas flow. At pressures of the order of P = 26 kPa, the discharge stability deteriorates, and high-frequency oscillations of the discharge voltage are observed in the gas flow (f ∼ 100 kHz). In this case, the discharge voltage decreases by a value of the order of tens of volts, and the glow of the positive column of discharge becomes intermittent. The typical oscillograms of discharge voltage pulsations are given.