Capacitor Selection Research Articles

Supplier Selection and Performance Evaluation for High-Voltage Power Film Capacitors in a Fuzzy Environment

Rapid advances in technology have shortened the upgrade and replacement cycles in industries such as electronics, household appliances, and communication technologies. Within these industries, high-voltage power film capacitors have become indispensable electrical components due to their good electrical performance and high reliability. The selection and evaluation of suppliers of these capacitors is therefore increasingly important. Suppliers play a crucial role in the electronics industry; the quality of their products determines the degree to which the quality of the final product can be guaranteed. Supplier quality also affects the ability of all the members in a supply chain to control costs. Evaluation by decision-makers is highly significant in the supplier selection process. However, when the opinions of multiple decision-makers are combined, issues such as cognitive differences, fuzzy linguistics, and uncertainty are common. This study presents a supplier performance index SPL and derives the estimates of the index SPL and its statistical properties. The proposed index is not only helpful for the accurate measurement of supplier performance; it can also reduce cognitive differences among evaluators in the decision-making process (that is, the sample variability associated with the Likert scale). Evaluation scores for each criterion for the linguistic labels are converted to triangular fuzzy numbers in order to reduce ambiguity. Subsequently, integrated crisp values are obtained by defuzzification in a fuzzy inference system. A real-world case study of the supplier selection of high-voltage power film capacitors is provided to illustrate the efficacy of the proposed method.

Analysis of Ripple Current in the Capacitors of Active Power Filters

This article provides formulae to determine the root mean square (rms) value of a capacitor current in an inductive-capacitive-inductive (LCL) filter used in a parallel active power filter (PAPF) circuit. The article presents an analysis of three components of the capacitor current: a component forced by the usually distorted voltage of the grid; a component forced by the nonlinear load current harmonics and harmonics in the output current of the PAPF that compensates them (a novel aspect presented in this document); and a component forced by the inverters of the PAPF containing carrier and sideband harmonics. The article also presents formulae for determining the rms value of current harmonics in dc-link capacitors forced by the ripple of the ac output current without load of the filter inverters (also novel to this document). The results of the analysis have been confirmed by simulation and experimental research of a commercial active filter consisting of two parallel interleaved voltage inverters. Elements of the LCL filter of the PAPF have been selected according to dependencies available in scientific and technical literature. In addition, the formulae presented in the article are used to verify the correctness of selection of capacitors from the point of view of their catalogue acceptable rms value of capacitor current.

Design and Validation of A 250-kW All-Silicon Carbide High-Density Three-Level T-Type Inverter

This article presents a comprehensive design and validation of a compact all-silicon carbide (SiC) 250-kW T-type traction inverter with a power density of 25 kW/l and 98.5% peak efficiency. All the operation modes and switching transitions in a T-type phase leg are analyzed to model the semiconductor power losses over a fundamental cycle. Special attention has been paid to investigate the behavior and losses due to the reverse conduction of the SiC MOSFETs. Then a loss model is built based upon this analysis to calculate the device loss distribution and system efficiency, which is further used to determine the optimal switching frequency. In addition, detailed inverter system design and prototyping procedure, including the selection of SiC modules and dc-link capacitors, and the optimization of a four-layer laminated busbar, are presented. In this article, the T-type phase leg is formed by a normal half-bridge module and a common-source module. The switching performance and losses in this configuration are different from two-level topology that only uses one SiC module. Therefore, the switching performance and the associated switching energy in each switch position are characterized using a custom clamped inductive load (CIL) test setup designed for a T-type phase leg. The performance of the full power traction inverter prototype has been verified experimentally using pulse testing and continuous power testing.

Single-Turn Air-Core Coils for High-Frequency Inductive Wireless Power Transfer

The efficiency of megahertz-frequency inductive wireless power transfer designs is currently limited by the quality factor of the resonant tanks and the coils. In this article, we use two-dimensional finite-element analysis to optimize the cross section of single-turn air-core inductors for this application and demonstrate coils for wireless power at high-frequency and very-high-frequency industrial, scientific, and medical (ISM) bands. Our resonant tanks achieve diameter-normalized quality factors (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ) that are 25%-70% better than the state of the art for air-core coils at 6.78 MHz (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> = 73 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) and 13.56 MHz (102), and we show significant improvements at the 27.12 MHz (123) and 40.68 MHz (137) ISM bands. We highlight the importance of capacitor selection and the tank configuration for designing high-Q resonant tanks and recover the increase of Q with frequency that is missing from the existing literature. Furthermore, we show that maximizing height is not ideal for wireless power transfer applications and build high-performance coils at small heights. We integrate these coils into a wireless power transfer system at 6.78 MHz and 500 W output power, showcasing a maximum dc-dc efficiency above 89% with a gap (3 cm) equal to the coil radius, a significant efficiency improvement over existing work.

Experimental Evaluation of Capacitors for Power Buffering in Single-Phase Power Converters

Single-phase inverters and rectifiers require the use of an energy buffer to absorb twice-line-frequency power ripple. Historically, this challenge has been addressed by the use of large electrolytic capacitors. Lifetime constraints and the need for improved system performance have motivated designers to seek other capacitor technologies, such as ceramic and film, which are frequently used in conjunction with active filtering converters to reduce the capacitance required. Active filtering converters cycle the capacitor voltage over a wide voltage range while maintaining a constant dc bus voltage. This large-swing operation demands different capacitor qualities than most other filtering applications, and the data sheet parameters available for commercial capacitors may be ineffective or require special care for calculating characteristics, such as efficiency and energy storage capability. This work presents an experimental setup for evaluating capacitor performance under a large voltage swing along with detailed experimental results. Energy storage data for a number of capacitors in the 50–630 V range from several manufacturers are included. The approach and findings of this paper can serve as an aid to power electronics designers for the selection and evaluation of capacitors in energy buffering applications.

A Study on the Selection of DC Bus Link Capacitor

A Study on the Selection of DC Bus Link Capacitor

Inductive Power Transfer to Charge Electric Bicycles

Inductive power transfer is nothing but wireless power transfer. That is transferring power from transmitter to receiver side without any physical contact. Nowadays this technique has wide applications. Mainly it is used to charge the batteries of the electric vehicles (EV). Due to the increasing pollution rate and scarcity of fuel in future days, the demand for the electric vehicles is increasing. Charging EV’s using IPT is simpler and risk free when compared to traditional wired charging systems. Using IPT technique the battery can be charged in constant current (CC) and constant voltage (CV) modes without using any feedback. A switch (consists of 2 AC switches and capacitor) is used to change the mode from CC to CV. The current output from the CC and the voltage output from the CV mode are load independent. This can be obtained by proper selection of inductances and capacitors. Here the feedback control techniques are not required to regulate the output according to charging profile. This IPT technique to charge battery is economical because using a single inverter many batteries can be charged at a time. The possibility of this method of charging is tested with an experimental prototype for efficiency and using MATLAB/SIMULINK software the simulation results are obtained for stability of current and voltage output of CC and CV mode.

Evaluation of DC‐link voltage ripple in five‐phase PWM voltage source inverters

This paper presents the analysis of the DC-link voltage switching ripple in five-phase PWM voltage source inverters with balanced load. The analysis is particularly important for the design and selection of a DC-link capacitor making it possible to meet desired electrical performance of the inverter system. Simple and practical equation for designing the DC-link capacitor is proposed relating the value of capacitance to the maximum value (peak-to-peak) of the DC-link voltage ripple. The amplitude of the DC-link voltage switching ripple is analytically derived as a function of modulation index, and the amplitude of the output current and phase angle. In order to show peak-to-peak voltage ripple distribution, different diagrams are introduced. Reference is made to continuous symmetric centred PWM modulation (i.e., space vector modulation SVM). In order to verify proposed developments, simulations have been carried out by Matlab/Simulink considering full range of modulation index and output phase angle.

Optimization Parameter Design of SEPIC-Cuk Converter

This paper discusses the optimization parameters design of combined SEPIC-Cuk converter based on SEPIC and Cuk operation for dual output voltage polarities. The SEPIC-Cuk converter is designed to be operated in continuous conduction mode, the selection of passive components, i.e., inductor and capacitor are based on the switching frequency, the duty cycle and inductor current ripple. The range of duty cycle for buck operation is 0<D<0.5, meanwhile for boost operation, the duty cycle range is 0.5<D<1.The simulation and experimental results show a good agreement. Thus, the designed parameters of the converter are confirmed. The finding shows that during buck operation, the output voltages are +3.96 V and -3.96 V with duty cycle of 0.25 when the output voltage is 12 V. Meanwhile, during boost operation, the output voltages are +36 V and -36 V with the duty cycle of 0.75 when the output voltage is 12 V.

Voltage Control of Rectification-type Three-Phase Squirrel-Cage Induction Motor

The VSCF squirrel-cage generation system mostly adopt full power double pulse width AC/DC/AC modulation. In order to reduce the capacity of the rectifier, a rectification system and its voltage control strategy is proposed. The rectifier and capacitor in parallel with the generator are used to compensate the excitation current and to adjust the generator voltage. Uncontrolled rectifier bridge and inverter are connected to the generator to supply electricity for the AC loads. The selection of build-up voltage capacitor is analyzed and system voltage control method is simulated and experimented. The rectification voltage can be kept basically a constant when the rotor speed and load change in a certain range. The rectifier compensating current is small which proves that the system structure is feasible and control method is effective.

Optimal energy efficiency of isolated PAT systems by SEIG excitation tuning

The use of pump working as turbine (PAT) was identified by many researchers as a way to improve the energy efficiency in the water systems. However, the majority of the researches consider the hydraulic machine connected to the electrical grid, which may not fit best when these recovery systems are located in rural or remote areas. To improve the efficiency in these recovery systems for rural areas, this research contributes for a further study and optimization of the off-grid PAT systems with induction generators. The current manuscript proposes a methodology to obtain the best efficiency of the PAT-SEIG (Self-Excited Induction Generator) system when operating under different speeds and loads. For these systems, the selection of capacitors for the SEIG is critical to maximizing the energy efficiency. A methodology is proposed to estimate and select the correct SEIG model parameters and, thus, compute the best capacitor values to improve the PAT-SEIG energy efficiency. Special attention is given to the impact the SEIG parameters have in the efficiency of the recovery system. The accuracy of the analytical model improved, reducing the error between analytical and experimental results from 50.8% (for a model with constant parameters) to 13.2% (with parameters changing according to the operating point of the system). These results showed an increase of the overall PAT system efficiency from 26% to 40% for the analyzed case study.

An LCL-Filter Design With Optimum Total Inductance and Capacitance

LCL -filter is among the best performing filters for grid-connected voltage source inverters. Designing of the filter parameters (grid-side and inverter-side inductors and capacitor), takes an iterative approach due to the coherence between the parameters and design requirements such as IEEE-519 Std for harmonic current limitations, reactive power compensation limit, and maximum allowable voltage drop across the filter to limit the switching losses. Most of the proposed LCL -filter optimization strategies emphasize on reducing the total inductance and losses of the filter while meeting the design requirements. There is less emphasis given on the capacitor selection and optimizing its value. Therefore, this paper proposes a method to compute the optimum capacitance requirement of the LCL -filter based on reactive power compensation of the filter rather than calculating it as a percentage of base capacitance of the filter as found in the literature. The proposed design methodology compared to the previously proposed designs is capable of reducing filter capacitance by 50% while meeting the harmonic limitation demanded by IEEE-519 Std and also considers the impact of the total inductance on reactive power compensation. Based on the proposed methodology an LCL -filter with minimum total inductance and capacitance is realized. Functionality of the proposed LCL -filter is verified and validated through simulations and experimental results.

Selection of Inductor and Snubber Capactor to Optimize the Size and Efficiency of DC-DC Switching Power Converter

This paper presents a selection of inductor and snubber capacitor in non-isolated synchronous DC-DC switching power converter. The circuit is made to operate in Synchronous Discontinuous Conduction Mode (SDCM)/Forced Continuous Conduction Mode (FCCM) of operation for minimum inductor value, to reduce the size, weight and cost of the converter. The turn off loss of the switch induced by SDCM of operation is minimized by connecting snubber capacitor across the transistor switch. Before the switch is turned ON, snubber capacitor requires certain amount of energy must be stored in the inductor to discharge the capacitor energy [1]. The question is how much capacitor and inductor value is required. A series of MATLAB script are executed to find minimum inductor value for FCCM of operation and to select snubber capacitor for maximum efficiency. Complementary gate signals are used to control the ON and OFF of main and auxiliary switch. SDCM of operation due to complementary control gate signal scheme, minimum turn on loss of the transistor switch and low diode reverse recovery loss are achieved. Thus the Zero Voltage Resonant Transition (ZVRT) of transistor switch is realized, both turn on and turn off loss is minimized and also removes the parasitic ringing in inductor current.

Electrolytics and Film Capacitors Continue to Evolve [Happenings

Electrolytics and film capacitors continue to evolve power electronics engineers know that the most important component in a modern power conversion device is the solid- state switch. The properties of this device have widespread impact on the performance achieved in any converter, and advancements in the capabilities of new switch products are widely reported and closely followed. However, filter capacitors are also important components. In fact, much of the volume of any converter is normally taken up by these components and still more is given to other parts that serve to keep these components cool. Indeed, a considerable part of the design process for a converter is devoted to the selection and application of filter capacitors.

Bus Bar Design for High-Power Inverters

This paper presents a comprehensive analysis about bus bar design procedure. Some applications in terms of rated power and shape are investigated regarding their particular requirements and challenges. The dc-link capacitor selection is one of the first and most important steps. It not only dictates the bus bar complexity but also is the key to accomplish a high-power density prototype. Current density and distribution is discussed in this paper based on simulation results. Moreover, the effects of stray inductance and capacitance are explained along with the dc-link capacitors and power semiconductor devices. Simulated results are compared with measurements by a high precision impedance analyzer, which shows the reliability of 3-D modeling-based designs.

Analysis of dc-Link Voltage Switching Ripple in Three-Phase PWM Inverters

The three-phase voltage source inverter (VSI) is de facto standard in power conversion systems. To realize high power density systems, one of the items to be correctly addressed is the design and selection of the dc-link capacitor in relation to the voltage switching ripple. In this paper, effective formulas for designing the dc-link capacitor as a function of the switching voltage ripple amplitude are obtained, considering the operating conditions such as the modulation index and the output current amplitude. The calculations are obtained considering the requirements and restrictions referring to the high (switching)-frequency dc-link voltage ripple component. Analyses have been performed considering the dc source impedance (non-ideal dc voltage source at the switching frequency) and a balanced load. Analytical expressions are derived for the dc-link voltage switching ripple amplitude and its maximum value over the fundamental period. Different values of modulation index and output phase angle have been considered and different diagrams are presented. Analytical results were validated both by simulations and comprehensive experimental tests.

Control of D-STATCOM During Unbalanced Grid Faults Based on DC Voltage Oscillations and Peak Current Limitations

The safe operation of grid-connected power converters during abnormal condition is a key issue in order to guarantee operation and to avoid undesired trips. In this paper, different control strategies for the operation of a D-STATCOM are introduced, where the reference currents are determined in such a way that not only will none of the phase currents go over the limits, but also the dc voltage fluctuations remain in safe operation limits. Fluctuating active power interchange during unbalanced condition leads to dc voltage oscillation. Severe unbalanced condition and small dc capacitor selection (to meet the size and cost constraints) intensify the dc voltage oscillation. Therefore, the contribution of this paper relies on the combination of the dc voltage oscillations and the current limit control. The effectiveness of three proposed control strategies is verified by simulating a D-STATCOM tied to an industrial distribution network. Moreover, a scaled scenario has been reproduced experimentally which shows that the results cope well with the analytical equations and the simulation results.

DC‐link current analysis of three‐phase 2L‐VSI considering AC current ripple

DC-link current is an important parameter for selection and design of DC-link capacitor or battery. Considering the AC current ripple, this study introduced a general DC-link current real-time prediction method for three-phase two-level voltage inverters (three-phase 2L-VSI) using the pulse width modulation. Compared with the traditional analysis which just takes AC average current into consideration, the time-domain comparison and spectral analysis of DC-link current have been studied. Meanwhile, accurate calculation of RMS current on the DC-link capacitor has been provided. Simulation results and experimental results are provided to support the analysis and proposed method.

Nine-level Inverter based Solar Power Generation for Micro Grid Application

This paper mainly focuses on to design a nine- level inverter for power generation using solar system to produce a nearly sine wave with reduced total harmonic distortion. The input from PV array is boosted using a dc-dc boost converter and fed into the nine-level inverter as three independent voltage sources. The capacitor selection circuit converts the three output voltage sources into a four-level dc voltage and it is further converted into nine-level ac voltage by full bridge converter. Hence the proposed system generates a sinusoidal output which is in phase with the utility voltage. The advantages of the proposed system is, it uses only nine power electronic switches, which results in reduced voltage stress and reduced total harmonic distortion without using any filter in utility side. Whereas, traditional system uses 16 power electronic switches and four independent dc voltage sources to produce a nine-level output voltage. By using minimum number of power electronic switches, the proposed system is compact and robust. Keywords: Capacitor Selection Circuit, Nine-level AC Voltage, Nine-level Inverter, Sinusoidal Output, Total Harmonic Distortion

Theoretical and Experimental Investigation of Switching Ripple in the DC-Link Voltage of Single-Phase H-Bridge PWM Inverters

Direct current (DC)-link voltage ripple analysis is essential for determining harmonic noise and for DC-link capacitor design and selection in single-phase pulse-width modulation (PWM) inverters. This paper provides an extensive theoretical analysis of DC-link voltage ripple for full-bridge (H-bridge) inverters, with simulation and experimental verifications, considering a DC source impedance (non-ideal DC voltage source). The DC voltage ripple amplitude is theoretically estimated as a function of the output current, both amplitude and phase angle, and the modulation index. It consists of a switching frequency component and a double-fundamental frequency component (i.e., 100 Hz), thereby both components are considered in the analysis. In particular, the peak-to-peak distribution, maximum amplitude, and root mean square (RMS) values of the voltage switching ripple over the fundamental period are obtained. Based on the DC voltage requirements, simple and effective guidelines for designing DC-link capacitors are obtained.