Showing papers on "LC circuit published in 2021"

Model Predictive Control of LC -Filtered Voltage Source Inverters With Optimal Switching Sequence

Abstract: Voltage source inverters with output LC filter enable a sinusoidal output voltage with low harmonics, suitable for islanded ac microgrid or uninterruptible power supply applications. Conventional finite-set model predictive voltage control (MPVC) applies only a single switching vector per control period, leading to a variable switching frequency and significant output ripple. This article resolves these issues by proposing an improved MPVC with optimal switching sequence (OSS-MPVC). First, an improved vector switching sequence is defined, aiming to reduce the output-voltage ripple with a constant switching frequency. Then, to tackle the difficulty in extending the OSS to high-order systems due to the coupling effect of the output filter, a generalized “one-step estimation” solution is proposed, which directly associates the control-variable gradients with the vector switching sequence. To further enhance the output-voltage tracking accuracy, intersample dynamics are taken into account in the cost function. The control delay and dead-time compensation are also considered. Simulations and experimental results verify the feasibility of the proposed method.

Size reduction and performance improvement of a microstrip Wilkinson power divider using a hybrid design technique

Abstract: In the design of a microstrip power divider, there are some important factors, including harmonic suppression, insertion loss, and size reduction, which affect the quality of the final product. Thus improving each of these factors contributes to a more efficient design. In this respect, a hybrid technique to reduce the size and improve the performance of a Wilkinson power divider (WPD) is introduced in this paper. The proposed method includes a typical series LC circuit, a miniaturizing inductor, and two transmission lines, which make an LC branch. Accordingly, two quarter-wavelength branches of the conventional WPD are replaced by two proposed LC branches. Not only does this modification lead to a 100% size reduction, an infinite number of harmonics suppression, and highfrequency selectivity theoretically, but it also results in a noticeable performance improvement practically compared to using quarter-wavelength branches in the conventional microstrip power dividers. The main important contributions of this technique are extreme size reduction and harmonic suppression for the implementation of a filtering power divider (FPD). Furthermore, by tuning the LC circuit, the arbitrary numbers of unwanted harmonics are blocked while the operating frequency, the stopband bandwidth, and the operating bandwidth are chosen optionally. The experimental result verifies the theoretical and simulated results of the proposed technique and demonstrates its potential for improving the performance and reducing the size of other similar microstrip components.

An Active Damping Strategy for Input Impedance of Bidirectional Dual Active Bridge DC–DC Converter: Modeling, Shaping, Design, and Experiment

Abstract: The dual-active-bridge (DAB) converter is applied for power transmission and voltage conversion in dc power grid. To improve the quality of input current, an input LC filter is cascaded to DAB converter. However, due to the interaction between LC filter and DAB converter, substantial oscillation and instability occur, leading to the excessive electromagnetic interference, large voltage ripple, and power loss and even operation failure. To solve this issue, an active damping strategy is proposed in this article to reshape the small-signal input impedance by parallel virtual impedance. The input voltage is regarded as a control objective, as well as the output voltage, therefore, a triple-closed-loop control structure is established. Besides, all dynamics of controllers are considered for the input impedance modeling of DAB converter. Moreover, compared with traditional methods, an active damping method for cascaded DAB converter with LC filter is adopted to design the virtual impedance and controller, suppressing resonance of LC filter and achieve a larger bandwidth. Therefore, a more stable and rapid dynamics cascaded system composed of DAB converter and LC filter are achieved. Finally, a prototype is set up and the effectiveness and superiority of proposed strategy are verified by experiments.

Photon-Pressure Strong-Coupling between two Superconducting Circuits

Abstract: The radiation-pressure coupling between two harmonic oscillators has been used in optomechanics for breakthrough experiments in the control and detection of mechanical displacement. Used primarily in optomechanics, there have been few reports of exploiting such a type of interaction in other platforms. Here, we engineer two superconducting LC circuits coupled by a strong photon-pressure interaction, a term we use in analogy to the radiation-pressure interaction between light and mechanical objects. The coupling arises from a change in the resonant frequency of one circuit in response to the current flowing in the second. We observe dynamical backaction between the two circuits, photon-pressure-induced transparency and absorption, and enter the strong coupling regime. Furthermore, we observe parametrically amplified thermal current fluctuations in a radiofrequency circuit close to its quantum ground state. Owing to the high design flexibility of superconducting circuits, our approach will enable new experiments with radiofrequency photons and parameter regimes of photon-pressure coupling that are not accessible in other platforms. Analogous to the radiation-pressure coupling known in optomechanics, photon-pressure interaction between superconducting circuits can reach the strong coupling regime, which allows flexible control of the electromagnetic resonator’s quantum state.

Toward Stabilization of Constant Power Loads Using IDA-PBC for Cascaded LC Filter DC/DC Converters

Abstract: This article proposes a modified interconnection and damping assignment passivity-based control (IDA-PBC) for dc/dc converter cascaded with an LC filter. The plant is modeled using the port-controlled Hamiltonian (PCH) form. The main objective is to stabilize the cascaded system in case the system supplies constant power load (CPL). To solve the instability issues caused by tightly controlled cascaded systems, the IDA-PBC based on an overall PCH model, including LC input filter and dc/dc converter, is established. Moreover, to ensure that the proposed IDA-PBC admits one unique solution, an adaptive interconnection matrix is designed to build the internal links in the PCH model. Furthermore, in order to improve the implementation on an onboard dc microgrid application with time-varying CPLs, a modified IDA-PBC algorithm is proposed based on the error between the state vector and the desired operating point, which might be variable. The closed-loop Hamiltonian function is chosen as the Lyapunov candidate function to guarantee that the system operates in a stable manner. The virtual damping assignment technique is addressed to tune the dynamic characteristic of the closed-loop system. Simulation and experimental results are carried out to illustrate the proposed method’s effectiveness.

Finite-Control-Set Model Predictive Control for Three-Level NPC Inverter-Fed PMSM Drives With $LC$ Filter

Abstract: The installment of $LC$ filter between the voltage source inverter and motor terminal can reduce the value of $dv$ / $dt$ considerably, and further mitigate the surge voltage stress on the motor windings during the long-distance transmission. However, the sophisticated controller needs to be designed to solve the additional resonance problems caused by the filter. Conventional active damping (AD) scheme mainly introduce the multiloop feedback based on the analysis in $s$ -domain or $z$ -domain, which is realized with limited bandwidth and high tuning complexity. In this article, the finite-control-set model predictive control (FCS-MPC) is adopted to realize the $q$ -axis current reference tracking for motor and suppress the filter resonance simultaneously. Different from the transfer-function-based AD scheme, the mechanism of resonance generation is revealed in the time-domain, where the cost function of FCS-MPC is designed to directly regulate the multivariable trajectory of the system. Therefore, the proposed FCS-MPC controller expresses the intuitive design principle, a simple structure, and fewer tuning parameters, which could be an alternative to the existing AD scheme. To reduce the number of sensors, the Kalman-filter based state estimation is used by considering the one-step delay of the control input. The cost function is further optimized to a simplified form that suits the implementation of the digital platform, and the lower computational burden is obtained. The experimental results prove that the proposed FCS-MPC scheme can ensure the motor-friendly waveform and overcome the resonance problem effectively. The robustness of the controller to parameter variations of the filter is also verified.

Harmonics Mitigation of Stand-Alone Photovoltaic System Using LC Passive Filter

Abstract: This article investigates modeling and simulation of the off-grid photovoltaic (PV) system, and elimination of harmonic components using an LC passive filter. Pulse width modulation (PWM) inverter is used to convert the direct current to alternating current. It is very important in terms of energy quality that the inverter output current total harmonic distortion (THDI) is below the value given by standards. Harmonic components have negatively effect on off-grid PV power system. THDI should be kept below a certain level in order to prevent damage to the equipment in the off-grid system and to ensure a higher quality energy flow to reduce the total harmonic distortion (THD) of the solar inverter output current; LC passive filter must be connected to the output of the PWM inverter. There are many types of passive filters for solar inverters. One of the most widely used filter types is the LC filter. LC filters are used in off-grid systems. LC filter is smaller in size and lower cost than other filters. But it is more complicated to determine the parameters of the LC filter. Therefore, in order for the system to remain in a steady state, the parameters must be accurately calculated and analyzed. In this study, the output power of the solar inverter, switching frequency, bus voltage etc. values were determined and LC filter parameters were calculated. Since high inductance values are used in LC filters, the voltage drop increases in these filters. To reduce the voltage drop, the DC bus voltage must be increased, which increases the switching losses. LC filter is connected between the inverter and the nonlinear load to filter the harmonic components produced by the DC/DC boost converter, DC/AC inverter and non-linear load. Matlab/Simulink program was used in Simulation and analysis of off-grid solar system. Solar inverter output current THD was measured as 91.55%. After the LC filter is connected to the system, this value has dropped to 2.62%.

2.4-GHz Bluetooth Low Energy Receiver Employing New Quadrature Low-Noise Amplifier for Low-Power Low-Voltage IoT Applications

Abstract: In this article, a 2.4-GHz Bluetooth low-energy (BLE) receiver employing a new quadrature low-noise amplifier (LNA) is presented for low-power low-voltage Internet of Things (IoT) applications. The proposed quadrature LNA consists of a common-source (CS) amplifier with inductive degeneration, an active-type poly-phase filter (PPF), and an LC tank. The proposed active-type PPF between the CS amplifier and the LC tank provides quadrature generation, and the CS amplifier determines and optimizes the overall LNA performance parameters. Moreover, the proposed active-type PPF shares the dc bias current with the CS amplifier, thereby eliminating the necessity for additional current consumption. The implemented BLE receiver is composed of the quadrature LNA, a $G_{m}$ -stage, a double-balanced current-mode passive mixer, a transimpedance amplifier, and an active- RC complex bandpass filter. The proposed design was fabricated in a 65-nm CMOS process and mainly characterized in the BLE operating frequency bands. The receiver achieves a noise figure of 8.2 dB, a conversion gain of 49.5 dB, an image rejection ratio of more than 33 dB, and an IIP3 of −25.75 dBm. The active die area of the implemented receiver is 1.16 mm2, and it draws a bias current of 2.7 mA from a nominal supply voltage of 0.8 V.

IPD-Based Miniaturized Wideband Bandpass Filter With Frequency-Dependent Complex Source and Load

Abstract: In this article, an ultraminiaturized bandpass-filtering matching network based on GaAs substrate integrated passive device (IPD) technology is proposed, which is suitable for frequency-dependent complex source and load. The presented bandpass filter (BPF) is derived from an equal-ripple Chebyshev low-pass filter prototype through frequency transformation and impedance scaling. The susceptance required by the source and load is extracted from the adjacent susceptance blocks, and the final reactance/susceptance block is equivalent to a series/parallel LC circuit at the two edge frequencies. Therefore, the proposed design has both bandpass high-selectivity and impedance matching functions, and simultaneously, the bandwidth can be flexibly controlled. Finally, a wideband BPF example with the center frequency of 3.5 GHz was simulated and fabricated with the IPD process, showing satisfactory performances.

Extensible Multi-Input Synchronous Electronic Charge Extraction Circuit Based on Triple Stack Resonance for Piezoelectric and Thermoelectric Energy Harvesting

Abstract: At present, research on interface circuits for environmental energy harvesting is mainly carried out around a single transducer However, rich ambient energy sources can be harvested with multiple transducers Hence, in this article, extensible multi-input synchronous electronic charge extraction (EMI-SECE) interface circuit based on triple-stack LC resonance for piezoelectric and thermoelectric energy harvesting is proposed proposed EMI-SECE interface circuit can simultaneously extract energy from multiple piezoelectric transducers (PZTs) and thermoelectric generators when the peak open-circuit voltage of the PZTs is detected by the passive peak detectors Theoretical analysis and experiments verify the effectiveness of the circuit The experimental results show that the proposed EMI-SECE circuit can harvest energy from two PZTs with any phase difference (0−2 π ) based on single inductor In addition, the circuit can harvest thermoelectric energy at an open-circuit voltage as low as 20 mV, and the maximum harvesting efficiency can be reached 857% at $V_{{\rm{oc}}}$ = 200 mV

A method for calculating the parameters of the sine filter of the frequency converter, taking into account the criterion of starting current limitation and pulse-width modulation frequency

Abstract: An analysis of the method for ensuring the sinusoidality of the output voltage in power generation systems with self-commutated voltage inverters under the requirements of the international standard IEEE-519 is presented. In a number of programs, especially low-power generation systems, a low-cost solution is needed to provide the sinusoidal waveform of the output voltage with the total harmonic distortion of 5 %. This solution is to use two-level voltage inverters with an output sine LC filter. However, the feature of the sine filter with the frequency converter is that the PWM frequency affects the spectrum of higher harmonics of the output voltage. In addition, there is the starting current of the filter capacitor, which can disable the power switches of the voltage inverter. The developed method for calculating the values of the LC filter with the two-level voltage inverter in the PWM mode is presented meeting the requirements of the international standard IEEE-519, taking into account the modulation frequency and limitation of the starting current of the filter capacitor. To confirm the required quality of the output voltage of the two-level voltage inverter with the sine filter, an appropriate simulation model was created in the Matlab/Simulink computer simulation environment. The oscillograms and harmonic analysis of the input and output voltages of the sine filter, which showed the total harmonic distortion of 1.88 %, are presented. A physical prototype of the investigated system was created on the basis of a 5.5 kW OVEN PChV203-5K5-V frequency converter (Ukraine). Using the SIGLENT SDS1104X-E oscilloscope (China), the real waveform and the results of the harmonic analysis of the sine filter output voltage, confirming the implementation of the necessary sinusoidality criteria, were obtained

Temperature and Pressure Composite Measurement System Based on Wireless Passive LC Sensor

Abstract: In this article, we proposed a measurement system that can simultaneously measure temperature and pressure. By analyzing several existing measurement methods of the sensor, we determined that the resonance frequency and $S_{11}$ (reflection coefficient) amplitude of the sensor readout system should be measured when the resonance frequency of the sensor up to a hundred megahertz or even gigahertz and when the sensor works in ultrahigh temperature environment. In addition, we designed a simple and accurate sensor readout circuit and an LC temperature–pressure sensor. By analyzing the resonance frequency and the amplitude of $S_{11}$ , temperature and pressure were measured simultaneously with a single LC circuit. Since the analysis of the whole nonlinear system of sensors is complex, we divide the entire nonlinear system into several linear systems superposition. By analyzing the interference between temperature and pressure, we further optimized the measurement method. The relative errors of the temperature measurements in the range of 25 °C–300 °C and 300 °C–1000 °C were only 2.89% and 1.25%, respectively. From 25 °C to 300 °C and 300 °C to 1000 °C, the average relative errors of pressure measurement were only 4.07% and 4.74%, respectively. Besides, the proposed method can also be widely used in the measurement of LC multiparameter sensors.

Modeling of Interconnected Voltage and Current Controlled Converters With Coupled LC – LCL Filters

Abstract: Nowadays, more and more converters under voltage control mode with LC filter and current control mode with L / LCL filter are interconnected, forming a more complicated impedance network and resulting in coupled control behaviors. This type of interconnected converter system can be commonly seen in a stand-alone microgrid and some advanced testing benches for power electronics converters. In this article, a system consisting of a voltage-controlled converter with LC filter and a current-controlled converter with LCL filter have been studied. A detailed mathematical model is proposed to describe the stability and coupling characteristics of such system. It is found that the stability problem in this type of configuration may arise in an uncommon way, which is different from the typical resonance in a grid-connected converter system and can be triggered in higher frequency band. Meanwhile, the voltage and current behaviors of interconnected converters are strongly coupled through the complicated filter impedances and control loops in low-frequency band and mid-frequency band.

Large-Signal Stabilization of Power Converters Cascaded Input Filter Using Adaptive Energy Shaping Control

Abstract: Series connection of input filters with static converters might lead to instability. However, the input filter has rarely taken into account in the stable design of power converters. Indeed, an input LC filter cascaded with a converter can become unstable even if the converter is regulated by a tight controller ensuring its stability alone. This fact is due to the interactions between the filter and the converter. To tackle the instability potential, an adaptive energy shaping control (AESC), which is based on the interconnection and damping assignment passivity-based control (IDA-PBC), is addressed in this article to regulate the cascaded system and achieve the following attractive features: 1) the input filter’s dynamics are considered in the control law, so the interactions between the filter and the converter are taken into account during the controller design and 2) the influence between several subsystems, put in cascade, is considered by the proposed method, and the new large-signal stability proof is given accordingly. Simulation and experimental results from a 3.5-kW, 270–200-V buck converter cascaded with an input filter under different load conditions, i.e., constant impedance load (CIL), constant current load (CCL), and constant power load (CPL), are presented to demonstrate the proposed approach.

Analysis and Design of Series LC Resonance-Pulse Based Zero-Current-Switching Current-Fed Half-Bridge DC–DC Converter

Abstract: This article investigates upon partial resonance in current-fed converter using series LC resonant circuit to attain zero-current-switching (ZCS) of the semiconductor devices. A resonance pulse appears during overlap conduction time of the semiconductor devices causing natural current reduction in an outgoing device to zero before the gating signal is forced- off achieving ZCS commutation of the devices. Soft device turn- off eliminates the turn- off switching losses and more importantly, avoids the traditional requirement of additional snubber to clamp the voltage across the semiconductor devices in current-fed converters. Partial resonance reduces the circulating current and so rms current through the devices limiting the conduction losses. The proposed idea is analyzed and implemented on current-fed half-bridge isolated voltage doubler topology. It has been experimentally demonstrated to achieve wide range ZCS operation along with high efficiency.

Sympathetic cooling of a radio-frequency LC circuit to its ground state in an optoelectromechanical system

Abstract: We present a complete theory for laser cooling of a macroscopic radio-frequency $\mathit{LC}$ electrical circuit by means of an optoelectromechanical system, consisting of an optical cavity dispersively coupled to a nanomechanical oscillator, which is in turn capacitively coupled to the $\mathit{LC}$ circuit of interest. The driven optical cavity cools the mechanical resonator, which in turn sympathetically cools the $\mathit{LC}$ circuit. We determine the optimal parameter regime where the $\mathit{LC}$ resonator can be cooled down to its quantum ground state, which requires a large optomechanical cooperativity, and a larger electromechanical cooperativity. Moreover, comparable optomechanical and electromechanical coupling rates are preferable for reaching the quantum ground state.

A multi-input, multi-stage step-up DC-DC converter for PV applications

Abstract: The paper introduces a step-up multiple-input multi-stage dc-dc converter with a soft-switching for Photovoltaic (PV) applications. The proposed topology is constructed from series connection of switched capacitor circuits to minimize the effects of partial shading and mismatch between PV modules. A soft switching is achieved for the entire switches in the converter with no need for additional components. The applied technique utilizes the stray inductance of PCB traces to create a LC circuit so that the zero current switching is achieved for all switches. Moreover, the converter will take advantage of the superior features of Wideband gap devices in order to operate at high switching frequency. As a result, bulky capacitors in switched-capacitor circuits are significantly reduced, hence, small size multilayers ceramic capacitors with high temperature capability will be employed. Furthermore, with the lower losses and the higher temperature capability of Wideband gap devices, the thermal requirements will be reduced and with fast reverse recovery time, the snubber circuit are not required. Simulation results are presented, laboratory prototype is constructed, and experimental results are given at rated power to validate the feasibility of proposed dc-dc converter under soft switching operation.

A Compact 196 GHz FSK Transmitter for Point-to-Point Wireless Communication with Novel Direct Modulation Technique

Abstract: A compact, fully-integrated 196GHz FSK transmitter for point-to-point wireless communication is prototyped with a 55nm SiGe BiCMOS process, demonstrating a single-channel data rate of 10Gb/s with a chip area of 0.68mm2. The achieved single-channel data rate is around 5x higher compared with all other FSK wireless transmitters and the chip area is around 4x smaller compared with other state-of-the-art sub-THz wireless transmitters. Unlike conventional FSK transmitters which encode data with two oscillators at different frequencies or with the control voltage of varactors in the LC tank, the proposed FSK transmitter performs data modulation by varying the phase shift of tunable phase shifting couplers in a coupled oscillator loop, resolving the issues of extra power consumption and long frequency settling time. In theory, frequency shift based on this mechanism is instantaneous without overshoot/undershoot issues.

Approaches to Area Efficient High-Performance Voltage-Controlled Oscillators in Nanoscale CMOS

Abstract: By optimizing the design of the inductor of a voltage-controlled oscillator for performance without the area constraint and fully filling the area underneath the inductor with other necessary components, the voltage-controlled oscillator performance, including area efficiency, can be simultaneously optimized. In addition to varactors and cross-coupled transistor pairs, a current source, VCO buffers, frequency dividers, and MOS bypass capacitors can be placed underneath an inductor of a VCO. Exploiting this, a 4.3–5.6-GHz VCO with an area of $14~400~\mu \text{m}^{2}$ and FOMA and FOMTA of −202 and −210 dBc/Hz, respectively, have been demonstrated in a 65-nm CMOS process. The VCO performance is further improved by using nMOS–pMOS cross-coupled pairs and operating at 16–19 GHz, which are near the frequency at which the LC tank $Q$ is near the maximum for the process. The output is frequency divided by four to generate signals at 4–4.8 GHz. These reduce the circuit area by ~3X. The circuit including all the components including a frequency divide-by-four circuit achieves FOMA and FOMTA of −209 and −214 dBc/Hz, respectively.

A High-Linearity and Low-EMI Multilevel Class-D Amplifier

Abstract: This article presents a Class-D audio amplifier for automotive applications. Low electromagnetic interference (EMI) and, hence, smaller LC filter size are obtained by employing a fully differential multilevel output stage switching at 4.2 MHz. A modulation scheme with minimal switching activity at zero input reduces idle power, which is further assisted by a gate-charge reuse scheme. It also achieves high linearity due to the high loop gain realized by a third-order feedback loop with a bandwidth of 800 kHz. The prototype, fabricated in a 180-nm high-voltage BCD process, achieves a minimum THD+N of −107.8 dB/−102 dB and a peak efficiency of 91%/87% with 8- and 4- $\Omega $ loads, respectively, while drawing 7-mA quiescent current from a 14.4-V supply. The prototype meets the CISPR 25 Class 5 EMI standard with a 5.7-dB margin using an LC filter with a cutoff frequency of 580 kHz.

Cascaded Control of Back-to-Back Converter DC Link Voltage Robust to Grid Parameters Variation

Abstract: The article elaborates on the mathematical modeling and control structure design of a grid-connected back-to-back voltage source inverter with a complex dc link and an LC filter for the current harmonics reduction. A cascaded, three-loop control structure is designed for controlling the converter current, the grid current, and the dc link voltage. The derived control structure, utilizing two sets of current sensors and a dc link voltage measurement, is based on proportional-integral controllers and a Truxal–Guillemin model-based controller for the dc link voltage control. The chosen control structure provides consistent results for great variations of the grid impedance. Robustness is tested for various scenarios of variations in grid filter parameters, controller parameters, chosen operating point for linearization, and grid impedance. Results are validated by simulations and experiments on a 7.5 kW converter and show highly robust performance for $\pm$ 20% parameter change and a large span of grid impedance variation.

Design and Verification of a 6.25 GHz LC -Tank VCO Integrated in 65 nm CMOS Technology Operating up to 1 Grad TID

Abstract: This article presents the design of an LC -Tank voltage-controlled oscillator (VCO) for space and high-energy physics (HEP) applications. The main goal of this work is to design a radiation-hard oscillator to be integrated into a phase-locked loop (PLL), compliant with (but not limited to) SpaceFibre protocol requirements, which is able to support the 6.25 GHz frequency. The full custom schematic and layout of the LC -VCO are reported in this work. The LC -VCO is implemented in a commercial 65 nm CMOS technology, and its electrical characterization highlights a tuning range (TR) from 5.4 to 6.8 GHz. An experimental chip was fabricated and irradiated with X-rays up to 1 Grad (SiO2) total ionizing dose (TID) level at CERN facility. The TID experiment and measurement results are analyzed and discussed. The LC -VCO shows a frequency degradation of 2.54% and a 3.34% increment in phase noise at 1 Grad TID. The results achieved are of interest for both space and HEP applications.

Two Level AC-DC-AC Converter Design with a New Approach to Implement Finite Control Set Model Predictive Control

Abstract: Due to various applications of variable frequency drives in industry, design procedure and control methods of these converters have attracted many researchers from both industry and academia. In this paper, a high power density AC-DC-AC converter design is presented alongside finite control set model predictive control method. Using model predictive control for the LC filter at the load side enables load voltage control which is an important issue in variable frequency drive applications. Also, input, output, and DC link filters’ design methods are presented and the results are compared to the designed filters in the literature. The comparison shows significant filter size decrease by using presented approach. Applying the proposed control method to the AC-DC-AC converter brings benefits such as simple implementation, robustness to the load changes, and fast dynamic response compared to conventional control methods. Finally, to demonstrate the effectiveness of the proposed design and control method, the designed variable frequency drive has been simulated and the results are presented.

State Plane Analysis of an LLC DC-DC Converter Operating above the Resonant Frequency

Abstract: A theoretical study of an LLC DC-DC converter operating above the resonant frequency was conducted. On the basis of a state plane analysis, expressions are derived to calculate the initial conditions for the differential equations describing the processes in the tank circuit. It is shown that all quantities depend on only one variable.

Novel Series LC Resonance-Pulse-Based ZCS Current-Fed Full-Bridge DC–DC Converter: Analysis, Design, and Experimental Results

Abstract: A current-fed full-bridge converter availing series resonance pulse to enable zero-current switching (ZCS) and voltage clamping of the semiconductor devices is proposed. Overlap in switching states of the devices enforces a short resonance pulse, due to series tank which naturally reduces the current to zero in the outgoing semiconductor devices. It causes zero-current commutation of the devices eliminating voltage spike across the semiconductor devices. Essentially, pulse-resonance offers reduced circulating current resulting in lower conduction losses and not demanding over-rated components. The proposed converter enables ZCS for wide variation in source voltage by implementing variable frequency fixed duty modulation eliminating the traditional requirement for additional clamping circuitry in conventional current-fed converters. Detailed experimental results on proof-of-concept hardware prototype rated at 500 W are demonstrated to verify the proposed claims and converter performance. With all other merits, proposed converter maintains high efficiency.

Phase-dependent microwave response of a graphene Josephson junction

Abstract: Gate-tunable Josephson junctions embedded in a microwave environment provide a promising platform to in-situ engineer and optimize novel superconducting quantum circuits. The key quantity for the circuit design is the phase-dependent complex admittance of the junction, which can be probed by sensing an rf SQUID with a tank circuit. Here, we investigate a graphene-based Josephson junction as a prototype gate-tunable element enclosed in a SQUID loop that is inductively coupled to a superconducting resonator operating at 3 GHz. With a concise circuit model that describes the dispersive and dissipative response of the coupled system, we extract the phase-dependent junction admittance corrected for self-screening of the SQUID loop. We decompose the admittance into the current-phase relation and the phase-dependent loss and as these quantities are dictated by the spectrum and population dynamics of the supercurrent-carrying Andreev bound states, we gain insight to the underlying microscopic transport mechanisms in the junction. We theoretically reproduce the experimental results by considering a short, diffusive junction model that takes into account the interaction between the Andreev spectrum and the electromagnetic environment, from which we deduce a lifetime of ~17 ps for non-equilibrium populations.

VSI LC filter optimized by a genetic algorithm from connected to island microgrid operation

Abstract: In microgrids (MG) with a high penetration of renewable energy sources (RES) power converters are used to regulate the produced energy to a single voltage and frequency reference value across the MG. Adequate incorporation of an LC filter at the output of power electronic devices allows the attenuation of harmful harmonics that can be introduced to the MGs energy bus. By traditional methods, LC filter values can be calculated by means of the power rating, switching frequency, cutoff frequency, and using the bode frequency domain. Nonetheless, in the transition from a connected to an autonomous MG operation, the calculated LC filter can lead to high harmonic injection. As a result, a tuning methodology capable of obtaining the right set of parameters for the LC filter for a transition event can improve the performance of the MG. This work optimizes the LC output parameters with respect to the size of the filter components, the IEEE Std 519-2014, and bandwidth of the filter, within a bounded region of values subjected to performance conditions such as voltage output, and the produced total harmonic distortion (THD) measurements during the transition from a connected to an autonomous operation. In a case study, genetic algorithm optimization is used to obtain the LC filter parameters and compared to a conventional arithmetic methodology to obtain the values of the filter. The optimization results in a set of values that lead to a higher harmonic attenuation after the transition rather than a conventional method using the switching frequency as the main design factor.