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Series capacitive-link universal converters are a relatively new class of single-stage power converters that offer numerous advantages including high reliability, high power density, and high efficiency. One of the limitations of these converters is high current stress of the switches, which lowers their efficiency in high current applications. In this paper, a new class of soft-/hard-switched parallel capacitive-link converters is introduced to address this limitation of the series capacitive-link universal converter while keeping its advantages. A small film capacitor, which is placed in parallel with the input and output switch bridges, is responsible for transferring the power from input towards output. A small inductor can be placed in series with the link capacitor to minimize switching losses and reduce EMI. The proposed parallel capacitive-link converter is expected to offer an enhanced efficiency and reduced current stress compared to the series capacitive-link universal converters. In this paper, principles of the operation of the proposed converter will be presented and its performance and advantages will be verified by simulation.

Capacitors are usually utilized at the DC-link of a power conversion system. Generally low parasitic inductance capacitors such as ceramic capacitors and film capacitors can reduce overshoot voltage during switching and DC bulk capacitors can address the low-frequency ripple. Due to the parasitic inductance, the energy swinging between the two types of caps via parasitic inductance leads to the oscillation which is typically at Mega-Hertz level and increases the voltage stress and power loss of the power devices. This phenomenon has been discovered repeatedly in the power converters with bus bar, integrated power module, and device characterization setup. To investigate and address this oscillation, the mechanism behind this oscillation is analyzed in details via a frequency-domain model in this paper. The impact of various electrical parameters are summarized. The proposed analytical model is validated via SPICE simulation and experimental study.

The accurate extraction of film capacitor equivalent series inductance (ESL) is the key to reliable operation in large-capacity power electronic equipment. In existing common ESL time-domain extraction methods, existed methods based on the integration calculation and short test suffered from the accuracy and test safety. Meanwhile, the ESL value in high frequency domain is hard to achieve. Based on this fact, in this paper, an ESL extraction method based on SiC MOSFET turn-off transient oscillation is proposed. It features in accurate ESL in MHz domain and consistency. Proposed methods are tested on four types of film capacitor, the feasibility is proved by tested results.

An integrated on-board charger uses the motor drive and its voltage source converter for battery charging when the vehicle is not running. This charger in AC-DC conversion stage has an inherent tendency to produce low frequency voltage ripple in both DC-link and split DC-link capacitor voltages. Therefore, bulky high valued electrolytic capacitors are adopted to absorb these low frequency capacitor ripples. Replacing these electrolytic capacitors with low valued film capacitors, results in poor input power quality. Therefore, this paper presents a control strategy based on modified unit-template control with reduced DC-link capacitance value to achieve improved input power quality without using any additional active/passive components. In modified unit-template control, the harmonics information of the grid current is feed-forwarded into the unit template to achieve unity power factor operation and reduced grid current THD. Furthermore, to reduce the influence of double frequency component on EV current/voltage, a DC-link feedforward control is implemented in DC-DC stage. Finally, the effectiveness of the solution presented in this paper, is verified by simulation and experimental results.

This paper presents a novel DC/DC converter for hybrid energy storage system (HESS) in DC microgrids. The proposed converter contributes to significantly reduce the component ratings, cost and size of the conventional HESS converters by using the multi-level, interleaved structure. The multi-level structure helps decrease the ratings and cost of power semiconductor and inductor; whereas the interleaved structure enables the replacement of bulky electrolytic capacitors using film capacitors, which substantially enhances converter reliability. Furthermore, the proposed converter allows the independent control of battery and supercapacitor energy storage. Its performance is verified by simulation results.

The short-circuit breaking function of a DC circuit breaker is realized by a repulsion mechanism driven by a customized MKMJ2-200 film capacitor. In order to ensure the reliable operation of the rapid repulsion mechanism, it is necessary to conduct in-depth research on its action characteristics. In this paper, a mathematical model is established around the design index of the repulsion mechanism; the results of voltage, current, electromagnetic repulsion, and the displacement of the repulsion plate are simulated and analyzed. Focusing on the problem that the excessive internal resistance RC of the film capacitor may cause the breaking failure, the simulation and analysis of the influence of the RC change on the characteristics of the repulsion mechanism; the calculation method combining simulation and actual measurement is used to quantitatively analyze the composition of the RC, and the RC is formulated

The increasing utilization of electronic converters to interface distributed energy resources (energy storage units and renewable energies) with the grid, has decreased the inertial spinning reserves of the power system. In this context, an isolated and bidirectional two-stage DC-AC converter with grid-forming virtual inertia capability and film capacitor on the DC-Link is presented. The proposed converter allows to interface energy storage units (ESU) with the single-phase grid. The two-stage DC-AC converter is composed of a dual active bridge series resonant (DABSR) DC-DC converter cascaded with a single-phase voltage source inverter (VSI), linked by a film capacitor. In the proposed control strategy, the DABSR controls the DC-Link voltage allowing the power decoupling on the DC-side while the VSI is controlled to emulate a virtual synchronous machine (VSM) when the ESU are connected to the grid. Therefore, the proposed converter has the following advantages: (1) high durability with reduced volume due to film capacitor instead of electrolytic capacitor on the DC-Bus, (2) high efficiency due to ZVS in the DC-DC converter and, (3) virtual inertia provided by VSI controlled as a VSM, increasing inertial energy reserves in the grid. The converter functionality and control strategy are validated by simulation of a 3.3kW system.

This article presents an isolated single-stage Dual- Active-Bridge Series-Resonant (DABSR) DC-AC converter with series-power decoupling (SPD) to interface PV with the single-phase grid. A third port is added in the proposed DABSR DC-AC converter, which is series-connected on the AC side to power decoupling. Therefore, the electrolytic capacitors, typically used on the DC side, are replaced by film capacitors. The single-phase time-variant power is decoupled by controlling the time-variant voltage on the third port, which depends on the power amplitude, the filter capacitor and the grid frequency. A novel modulation is proposed where the grid and the third port voltages are modulated by unipolar PWM while the PV voltage is modulated by duty ratio. The power flow is controlled by phase-shift modulation. High efficiency is obtained due to soft-switching operation into all active bridges. Besides, low THD in the grid current is obtained. MPPT is performed with high accuracy. Finally, the proposed converter is compared with a similar DABSR DC-AC converter without SPD (WoSPD). The novel modulation, converter design and the control strategy are presented and validated by simulation.

Long-term reliability testing time of power electronic components (e.g., film capacitors) entails delayed feedback of their performance, often many months to years, which has been one of critical limitations for accelerating power electronic technology development. In this paper, we explore a method to reduce the reliability testing time by exploiting capacitor's early-degradation information. In contrast to the conventional testing methods based on end-of-life (EOL) data alone, the proposed method makes more use of early degradation information in the reliability testing. The proposed method can predict the EOL lifetime of the film capacitor with 2.5% degradation testing only. The maximum error of the predicted result is less than 5% error compared to the conventional test-to-fail method. The proposed work serves as a first step to reduce the reliability testing time and accelerate the technology development of power electronics.

Non-inverting buck-boost converter is a classical topology that can provide wide range of voltage conversion and bidirectional power transfer; thus, it is frequently used in industrial applications. However, the conventional hard-switching configuration can only reach a high voltage conversion ratio at the expense of low efficiency due to switching loss. In this paper, a soft switching non-inverting buck-boost converter is proposed. This converter uses a small film capacitor in parallel with the link inductor to provide zero voltage switching (ZVS) by allowing the link capacitor and link inductor resonate between power transfer states. This paper presents the principles of the operation of this converter and verifies its performance through simulation and experiment.

In this paper, the samples preparation, experimental details, and characterization of the Electrophoretic Deposition (EPD) of a thick film Barium Strontium Titanate (BST) capacitor intended for radio-frequency applications are reported. With a bias voltage from 0 V to 20 V, the Ba 0.7 Sr 0.3 TiO 3 capacitor fabricated demonstrates 49% of tunability. The quality factor and the microwave (MW) loss tangent are calculated from 500 MHz to 5 GHz. Using an one-tone measurement setup, the small signal S-parameters measurements for the BST thick film capacitor are also presented by applying input signals from -20 dBm to 4 dBm. The linearity and loss tangent are analyzed considering a comparison of two different bias voltages, 0 V and 10 V. For the first time, the BST thick films fabricated with EPD are implemented and measured in the MW regime.

Power density of film capacitor is lower than that of electrolytic capacitor. It is significant to study how to reduce the capacitance for replacing electrolytic capacitor with film capacitor for cascaded h-bridge STATCOM. Increasing fluctuation amplitude on DC-link voltage is able to effectively reduce the capacitance for cascaded H-bridge STATCOM. However, there are few papers on the capacitance design of DC- link capacitor under increasing voltage fluctuation amplitude. The existing methods only consider the capacitive capacity of STATCOM when designing the capacitance. This paper first analyzes the relationship between capacitance and output current under capacitive and inductive conditions, respectively. In addition to considering rated capacitive capacity, a design method is proposed, where certain inductive capacity is retained according to the actual demand. Finally, the theoretical analysis is verified by some key simulation results.

As an energy storage element, capacitors are gradually being used in various complex environments. When subjected to high-energy radiation, the internal and surface of the dielectric material wilt accumulate charges and cause discharge, and it will cause irreversible changes in the physical and chemical structure of the dielectric, which will affect the performance of the capacitor. In this paper, polypropylene film and metallized film capacitors have been tested, and the effect of gamma-ray irradiation on the crystallinity of polypropylene film, the basic parameters of metallized film capacitors (relative permittivity, dielectric loss and ESR), voltage maintaining performance and space charge polarization characteristics are studied. The preliminary results show that when the total radiation dose is small (less than 100kGy), the relative permittivity of the capacitor does not change significantly before and after the radiation. When the absorbed dose reaches 1000kGy, the relative permittivity of the capacitor decreases by 5.1×10-1%; irradiation will cause the voltage maintaining capacity of the capacitor to decrease. When the absorbed dose increases from 0kGy to 1000kGy, the voltage drop within 10s of the capacitor increases from 1.62% to 6.54%; with the increase of the radiation dose, the crystallinity of the film gradually decreases, and the space charge polarization degree of the metallized film capacitor gradually increases. When the radiation dose increases from 0kGy to 1000kGy, the film crystallinity changes from 48.56 reduced to 34.52%, Q/A increased from 0.5 to 3.56.

In this paper, a low-cost 63kW/L DC-DC converter operated at 300kHz is proposed for 800V fuel cell electric vehicles. Four modules of Dual Floating Output Boost Converter (DFOBC) are adopted to process 100kW power from the FC stack. For each module, an inverse coupled inductor and ZVT cells are employed. Advantages of the proposed converter over the Conventional Interleaved Boost Converter (CIBC) which is usually used in the previous FDC are found to be: 1) Planar core with PCB winding can be used for the main inductor; 2) Tall film capacitors are replaced by a low-profile ceramic capacitor; 3) Only a single discrete SiC mosfet is needed for the main switch of a 25kW module. A 25kW prototype of proposed converter is built and tested. The peak and full-load efficiencies confirm at 99% and 97.7%, respectively.

This paper proposes a novel circuit configuration and control method for a power converter for a grid-connected inverter that does not require both a transformer and a large- capacity electrolytic capacitor. A power conditioning system (PCS) with a single-phase power supply requires a large- capacity electrolytic capacitor in the DC link to keep the input current of the PV panel constant. In addition, the PCS requires an isolated transformer for system safety due to the stray capacitance of PV panels. The proposed circuit consists of a six- pack power module. Besides, the input current is constantly controlled by the active power decoupling (APD) method with a small-capacity film capacitor. Furthermore, the proposed circuit has the feature that it does not require a transformer for isolation because the input terminal and the output terminal can be connected. The experimental results show that the APD operation with an output power of 500 W, and twice the grid- frequency components on the input current, which is a power pulsation, is reduced by 91.2%.

The coefficient of variation of the dissipation factor of PP (polypropylene) film capacitors was examined in dependence on the time of heat treatment and the frequency. Five groups of PP film capacitors from five manufacturers were taken under test. Every group was composed of twenty capacitors. The nominal capacitance of the capacitors was 0.1 μF and the maximum operating voltage 275 V AC. All capacitors were of the type X2. The heat treatment was carried out at the temperature of 100 °C for a total time 22 983 hours. The dissipation factor was inspected in the frequency range of 1 kHz – 1 MHz. The courses of the coefficient of variation of the dissipation factor of every group of capacitors were compared mutually. It was found that the inspection of the variation coefficient can be good additional information to the monitoring the loss factor.

in this paper, a high-precision integrated simulation model for conducted emission prediction and of multi-in-one electric drive system with EMI filter is established. In this model, a novel IGBT accurate modeling method of “Data Sheet Combined Double Pulse Test” is proposed, the motor impedance model and π type filter circuit model including high frequency parasitic parameter effect are established, the stray parameter of DC cable and AC copper bar was extracted by 3D finite element method. The validity of the model is proved by verification of test result and simulation. Using this model, the influence of the parasitic parameters of Y capacitor and film capacitor is further analyzed. It is proved that quantitative analysis of conducted EMI prediction and filter design of multi-in-one electric drive system can be realized by modeling in this paper.

Metallized polypropylene film capacitors (MPPFCs) are widely used in Modular Multilevel Converters (MMC), owing to its high energy density self-healing capability, and high reliability. However, the impact of temperature on the dielectric properties of capacitors is usually neglected for the existing research. It is significant to investigate temperature effect on dielectric properties of MPPFC, and for more accurate assessment of insulation condition. This work is oriented to evaluate the dielectric performance of MPPFCs by using LCR meter, at the frequencies from 20 to 105 Hz and the measuring temperature ranging from 20 to 160 °C. The variations of characteristic parameters of the capacitance and dielectric loss at different temperatures are compared. The results show that, for lower temperatures (up to 140 °C), capacitance as well as dielectric loss acquires a constant value and does not change significantly. While at higher temperatures (>140 °C) as it approaches its melting temperature, increment in temperature results in a sharp decrease in dielectric constant. Compared with room temperature samples, the capacitance of sample is dropped by 12.5% for 150 °C and 31% for160 °C. It could provide a reference for the accelerate aging test of metalized film capacitor in the MMC converters.

In this paper, novel polypropylene (PP) films were designed for metallized film capacitors (MFCs) by crystallization control. Modified PP films were doped with a kind of organic additives, which had a well dispersion in PP and could promote the crystallization process. The change of micro morphologies in films was confirmed by thermal measurements. Besides, the doping content was optimized based on the breakdown experiments under DC voltage. When the content was 0.03 wt%, the breakdown strength of modified films was 584.8 kV/mm, an increase of 19.57 % compared with that of the pure PP. The amplitude and frequency of harmonics were taken into consideration in actual operation of the capacitor in converter valves. The optimized film showed stable advantages in breakdown properties without increasing the conduction loss. This work can provide a reference for the performance improvement of PP films for MFCs.

Current-induced defects were observed in segmented electrodes of metallized film capacitors. Aperiodical current pulses of different amplitude and duration were applied to the experimental samples. It was found that thin demetallized lines (cracks) propagate in the direction of current streamlines. Scanning electron microscope was used to determine a width of investigated defects. Current density value needed to demetallized lines appear was calculated using numerical simulation in COMSOL Multiphysics software. It was proved that these defects are fast electromigration cracks.

The influence of Al and Zn metallization and demetallization processes on breakdown strength of thin polypropylene film is investigated. The breakdown strength of a polypropylene film drops about 10% upon covering with thermally evaporated 10 to 50 nm thick Al metallization, and it weakly depends on the thickness of metal layer. Al form nanoparticles 10-20 nm in size over polypropylene fibers at the initial stage of metallization layer formation. These nanoparticles grow and coalesce with Al layer thickness increase. The demetallization by the electric explosion and surface arc discharge induced erosion of metal layer (aluminum or zinc) process leads to up to 30% reduction of breakdown strength for aluminum metallization, and up to 20% for zinc metallization, respectively.

Reducing power transmission is a new trend to increasing the whole efficiency. Meanwhile, the presence or absence of electrolytic capacitor (E-cap) is another important criterion for judging the performance of LED drivers. Based on this, a new single-stage AC/DC converter is proposed in this paper, which demands fewer power semiconductors compared to previous works due to the magnetic integration technology and the time-division multiplexing of devices, thus lower cost and higher efficiency is achieved. And, the power flow of decoupling circuit is further optimized, where most of the energy is designed to transfer directly to the load, reducing the intermediate link and simultaneously employing the film capacitor. Besides, a simple automatic PFC scheme is presented, where near perfect power factor is obtained. Finally, all the superior performances of proposed LED driver are verified under PSIM simulation platform.

Single phase ac to dc power converter generally requires an energy storage element to support instantaneous power difference between dc side and ac side. An option to use a large value of electrolytic capacitors as energy storage is not viable due to their limited lifetime and poor reliability. Hence, in reliable rectifier designs, Active Power Decoupling (APD) circuits are preferred to allow the use of long life ceramic or film capacitors. The use of bidirectional buck converter as APD circuit is advantageous due to its simple control and low switch count. With conventional controller for buck APD circuit, dc-link voltage fluctuations during load changes are often large. This may result in maloperation of dc loads and increase the voltage rating of power devices in rectifier. To address said challenges, this study ideates a dc-link voltage feed forward controller for buck APD circuit. Proposed controller does not require additional sensors to synthesize the feed forward signal. Further, it supports seamless integration of buck APD circuit into an existing rectifier design with minimum changes in host system. The design recommendations and stability analysis for buck APD circuit with proposed controller are also provided. The satisfactory operation of proposed controller is confirmed with the help simulations using MATLAB/Simulink.

Power factor correction (PFC) and the elimination of second harmonic ripple without using an electrolytic capacitor (EC) are the key factors for an AC-DC Light Emitting Diode (LED) driver. The ECs are used to diminish the pulsating current with double the supply frequency at the output which reduces the life span of the LED driver. In this paper, a Boost converter with a coupled Inductor Bi-directional converter (CIBDC) configuration is proposed. This configuration consists of a Boost PFC converter and CIBDC for replacing the short life span ECs with long life span film capacitors. Boost PFC is operated in discontinuous conduction mode (DCM) to obtain unity power factor and CIBDC diverts the ac component of the Boost PFC converter and allows the dc component to the LED load. Also, by using coupled inductor zero voltage switching (ZVS) is achieved for the power switches to reduce the switching losses. Hence, the proposed configuration has advantages of near unity power factor, reduced switching losses for improved efficiency, elimination of ECs, and low output current ripple. A 100 W AC-DC LED driver configuration is validated using PSIM software.

Increasing the power density of PV inverters have been of great interest in the PV industry. With a smaller and lighter inverter, the installation cost can be greatly reduced, making solar energy more affordable. To improve the power density of PV inverters, a new internal parallel converter has been proposed in the literature and prototyped. This paper presents the key design considerations of the Gallium Nitride (GaN) based power stage as the high switching frequency (HSF) module in the modularized prototype. Two issues have been addressed in detail, i.e. the sizing of film capacitor based flying capacitor (FC) and design of GaN power board. A current stress based sizing has been investigated for FC indicating that the volume of the FC bank is dominated by the current stress instead of the switching frequency. Furthermore, design of the GaN power board based on insulated metal substrate (IMS) board has been discussed in detail. In addition to improved thermal performance, the metal substrate can serve as a shielding layer and help reducing the power loop parasitic inductance. Experimental results have confirmed that the designed GaN HSF module can safely operate under full power.

Cascaded H-bridges (CHB) converter equipped with pulse width modulated (PWM) rectifiers has been widely adopted in medium-voltage motor drive applications for the ability of power regeneration. But capacitor in each submodule suffers severe issue of voltage fluctuation at twice the inverter frequency, which can be worse when motor works at low speed and heavy load. The causes of voltage fluctuation are studied in this paper, including low running speed and fluctuating instantaneous power of inductors in front-end rectifiers. The fluctuating power of inductors will cause large voltage fluctuation on capacitors, and this issue is ignored in previous studies. This paper also proposes an improved power feedforward method to tackle the issue of fluctuating power of inductors, in which the input power and output power of submodules are totally counteracted. By counteracting power of input and output totally, voltage fluctuation decreases dramatically and capacitance can be minimized. Therefore, electrolytic capacitors can be replaced by film capacitors with small size and long lifetime. Simulation results based on 6kV, 710kW motor verify the effectiveness and validity of the proposed method.

The self-healing performance of metalized film capacitors is studied by building a repeated charging and discharging setup and a self-healing signal testing setup. The charging and discharging setup imitates the working condition of the metalized film capacitor. The process is repeated until the lifetime of the capacitor came to an end. During the experiment, the self-healing signal was detected and counted at the same time, which was achieved by building a self-healing signal detection setup. The self-healing signal detection setup was used to achieve the acquisition of self-healing waveforms and amplitudes and the number of self-healing signals. In the research, it was found that only the capacitance changed monotonously. The waveform of self-healing discharge has a certain regularity. In the initial stage of the aging test, the waveform is relatively regular, but when the aging test continues to approach the end of the capacitor's lifetime, the waveform is distorted, and the cause of the distortion is analyzed. When the performance of the capacitor continues to deteriorate, the frequency of self-healing discharges also begins to become more frequent, and the amplitude increases. Besides, by dissecting the capacitor, it can be found that the self-healing discharge point is mainly located at the margin. That means the field strength distribution at this place needs to be optimized.

The novel types of electrodes segmentation patterns for metallized film capacitors were suggested. Electrodynamic destruction of segmented electrodes due to self-healing process was numerically calculated using COMSOL Multiphysics software. The dependence of electrodynamic destruction energy versus destruction time was used as a criterion of segmentation pattern efficiency. Advantages and disadvantages of novel electrodes segmentation types were determined. It was found that bridge-diamond segmentation is the most effective patterns configuration.

High-brightness light-emitting diodes (HB-LEDs) is next generation of green lighting. However, the bulky electrolytic capacitor in converters is required to compensate the difference of pulsating power, thereby restricting the lifetime of the whole system. Meanwhile, the existence of full-bridge rectifier circuit and multi-stage transformation hinders the further improvement of power density. In this paper, a three-port network for single-stage bridgeless LED driver is proposed with the way of sharing so as to reduce the use of devices, thus higher power density is achieved; and additional port dedicated to power decoupling function so as to dramatically reduce the decoupling capacitance, thus allowing for film capacitors to be used. Operating principle, design considerations and performance comparisons are examined in detail. Finally, all the superior performances of proposed LED driver are verified by the PSIM platform.

With the increasing application of nonlinear electrical equipment in the industrial field, the harmonic content in the power grid is gradually increasing, which brings great harm to the foil-film capacitors used in the system. In order to study the breakdown characteristics of the dielectric in the foil-film capacitor under DC superimposed harmonic voltage at different temperatures, a breakdown test platform is established for the foil-film capacitor immersed in benzyl toluene and the foil-film capacitor elements are subjected to DC voltage, DC superimposed 3rd harmonic voltage, DC superimposed 5th harmonic voltage at 40°C, 55°C, 70°C and 85°C respectively. The results show that under the same type of voltage, the breakdown strength of the insulating medium in the foil-film capacitors decreases with the increasing temperature. Besides, in the temperature range of 40°C ~85°C, the breakdown strength of the insulating medium of the foil-film capacitors decreases with the increase of the harmonic order of the harmonic voltage at the same temperature.

In order to meet the challenges of the harsh working conditions for capacitors at high temperatures (>150°C), dielectric polymers with high glass transition temperature (Tg) have been considered as the candidate for the next generation of film capacitors. In addition to high operating temperature, many efforts have been made in developing high dielectric constant and low loss in high Tg polymers. Recently, we report the finding that the dielectric constant of high Tg dielectric polymers can be increased markedly by very small amount of nanofiller loadings (< 1 vol%) without increasing the loss. In nanocomposites, it is well known that the interface effects between the polymer matrix and nanoparticles play important role in determining the performance. In this work, chemically modified nanoparticles are employed to investigate the interface effects of nanofillers in the enhancement of dielectric responses of these nanocomposites.

Dielectric polymer film capacitor with high energy density and efficiency is one of the enabling technologies for the development of flexible electronics and power systems. Herein, we introduce wide-bandgap inorganic fillers into the polymer matrices to yield polymer nanocomposites. It is found that the leakage current is largely decreased, and the charge-discharge efficiency is significantly improved of the nanocomposites, especially at high fields and elevated temperatures, compared to polymer matrices. The increase in activation energy indicates that the presence of wide-bandgap nanofillers in the polymer matrix gives rise to a higher barrier to be overcome for occurring conduction processes. In addition, a strong dependence of high-field conduction behavior on the filler morphology is revealed. Compared to zero- and one-dimensional fillers, two-dimensional nanoplate enables the shortest hopping distance, and is the most efficient in inhibiting conduction loss of the polymer composites.

As the applied voltage increases, partial discharge has become one of the most important factors affecting the service life of metallized film capacitors. Therefore, the insulating structure of the capacitor needs to be optimized to increase the insulating strength. In this paper, a metallized film capacitor is studied by simulation. Its simulation results show that the maximum electric field strength occur at the edges (inside) of the metallization, the thickness of the metallization and the smoothness of the metallization edges also have a great influence on the maximum electric field strength, and the calculation results of the model established after reducing film number and film width in the correct way are valid. Therefore, a targeted increase in the thickness of the dielectric at the metallization edges is an effective way to reduce the occurrence of partial discharge as well as enhance the reliability of capacitors. In addition, proper metallization thickness and metallization edge treatment can also improve the dielectric strength of the capacitor to some extent.

In this paper, a Four-Switch quasi-Switched Boost Inverter (FS-qSBI) is derived from the embedded type-2 qSBI topology. It has all the advantages of qSBIs such as continuous input current, higher ac output voltage, simultaneous operation with both ac and dc loads, and shoot-through immunity. Additionally, it has one less switch and one more capacitor compared to the qSBIs. In order to address the inherent dc-side low-frequency ripple issue of FS-qSBI, this paper also proposes a low-frequency ripple damping scheme so that size of the capacitor can be significantly reduced without using any additional hardware component. Thus, highly reliable film capacitors can be used instead of conventional electrolytic capacitors, which results in improved power density, system lifetime and reliability. A stability analysis of the system, exploring the impact of capacitor reduction, is also presented. The FS-qSBI is implemented in hardware to verify the theoretical analysis and the proposed low-frequency ripple damping scheme.

This paper proposes control techniques for a three-phase diode rectifier with an instantaneous reactive power compensator (IRPC) whose the dc-link voltage is connected to a buck converter to control power of a dc load. At the dc-link voltage, a small film capacitor is inserted in the system causing a square waveform for the ac currents of the rectifier. Moreover, the three small ac inductors are used to reduce the current ripple from the switching frequency of the buck converter. These ac inductors cause the commutation overlap in the diode rectifier, and the control system would be unstable because of the resonant frequency between the ac inductors and the dc-link capacitor. Hence, this paper presents the analysis and the control technique performance of the system based on estimated power of the rectifier without detecting ac current of the rectifier. A 4.5-kW experimental setup was used to verify the control methods. As a result, the proposed techniques can control the grid current as a sinusoidal waveform with a THD i and an efficiency of 4.68% and 97.8%, respectively.

Nowadays, the three-level T-type inverters are extensively applied for photovoltaic (PV) generation systems. The neutral-point voltage of the T-type inverter may is subjected to low-frequency oscillation which causes output current distortion and disrupts the maximum power point tracking (MPPT) process of PV panels. In this paper, a new hybrid modulation is proposed to suppress the neutral-point voltage oscillation and control the average neutral-point voltage simultaneously. Consequently, the dc-side capacitors of the inverter are selected smaller and film capacitors can be replaced with electrolytic capacitors to increase the lifetime of the inverter. Moreover, the average neutral-point voltage is controlled to interact with the MPPT process. The experimental tests have been accomplished to prove the effectiveness of proposed modulation.

An Activity Smoothen Circuit with bidirectional Buck-Boost Converter (AS-BBC) was approached to smoothen the output power of a power factor correction (PFC) converter, which is an AC/DC converter, without using any electrolytic capacitors in this paper. In order to smoothen the output pulsation current of the PFC converter, electrolytic capacitors have been used generally, since electrolytic capacitors have a large magnitude capacity. However, there is a lifespan to electrolytic capacitors. On the other hand, film capacitors have a semi-permanent lifespan with so much less magnitude capacity than electrolytic capacitors. A way of using the AS-BBC to make a small capacitor work like a large capacitor as a smoothing capacitor to handle the output power is presented in this paper. Approximately 47% of the pulsation output is suppressed with a $4.4\mu \mathrm{F}$ film capacitor with the AS-BBC. Since there is no electrolytic capacitor adapted, a semi-permanent lifespan PFC converter is achieved successfully.

EMI (electromagnetic interference) filters are widely used in electronic devices and systems. They have considerable effects on the Electromagnetic Compatibility (EMC) performance of circuits. However, after long-term operation, the filters can exhibit severe degradation due to the intrinsic ageing mechanism and external thermal and electrical stresses. To be specific, the performance of the internal capacitors, typically represented by their capacitance value and equivalent series resistance, will largely deviate. These issues weaken the filters’ functionality, the service life as well as their EMC compliance. However, other parasitic parameters, like parasitic inductance, dielectrics insulation which are necessary for evaluating the performance, are usually neglected. In this study, the deviations of the EMI filters cause by the ageing of the capacitors are analyzed based on complex impedance analysis. The ageing characteristics of the filters with respect to the capacitor’s deviations, where nearly all parasitic parameters were taken into account, are identified by conducting an electrical overstress accelerated ageing test.