ABSTRACT. In order to reflect the high frequency dynamics into the MMC based MTDC systems, the hybrid TS and EMT hybrid simulation method with the proposed partial correction FDNE model is given in this paper, which high accuracy and efficiency are both guaranteed. The IEEE 39 bus system with four-terminal MMC based MTDC systems validates the effectiveness of the proposed method.

ABSTRACT. This paper presents sequence impedance modeling and analysis of modular multilevel converters in a single-star configuration for STATCOM application. Prior work on impedance modeling of MMC has focused on the double-star configuration for high-voltage dc (HVDC) transmission applications. The differences between the single-star and double-star configuration have important effects on the small-signal (impedance) characteristics of the converter which this paper tries to model. A particular application for the developed models is STATCOM for damping of power system resonances involving renewable energy generation and/or HVDC transmission. Implications of single-star MMC impedance characteristics on STATCOM control design for such application are discussed.

ABSTRACT. This digest shows the measurement of input impedance for power electronics converters based in the time domain and compares this time domain impedance with the impedance obtained in the frequency domain when Fourier transform is applied. Hilbert transform is widely used in signal processing and it is a good tool to understand some phenomena in electrical systems. This brief presents the application of the Hilbert transform to estimate the impedance of a two level power electronics voltage source converter. First an initial example is described. An application to obtain the impedance for a power electronics converter is shown.

ABSTRACT. Small-signal, impedance-based methods in a rotating dq reference frame are being used to analyze power systems. This approach was first used in small systems that needed to be redeveloped every time the configuration is changed. VSC models have also been developed synchronized to a local rotating reference frame. Individual models have to be transformed into a common reference frame before they can be connected together. This work will redevelop VSC models rigorously and show the effects of alignment to a local frame on the impedance as well as compare ways to connect multiple converter to form the network impedance model.

ABSTRACT. An HVDC system based on a Cockcroft-Walton (CW-HVDC) topology is proposed and a novel strategy is proposed to analyze and control the converter. In the connection to the grid the CW-HVDC uses a 3x2 matrix converter. The CW-HVDC voltage state-space vectors are derived and used to guarantee nearly unitary power factor in the connection to the grid. Sliding-mode controllers are designed to control the grid side currents, and a linear controller is designed to control the output DC voltage, setting the reference for the grid side currents. A CW-HVDC with 50 levels is tested through simulations to validate its operation.

ABSTRACT. A nonlinear control strategy for single-stage single-phase grid-connected photovoltaic (PV) inverters in synchronous dq frame is proposed to achieve both maximum power point operation, regardless of the atmospheric conditions, and to manage the active and reactive power. The control scheme forces the d-axis current to track the novel trajectory reference current, obtained online. It provides for energy balance from the input to the output of the system along with mitigating the PV current ripple, which is the major drawback of the single-phase PV inverter. A Lyapunov analysis is developed to prove the stability of the system and boundedness of signals.

ABSTRACT. It is necessary to analyze stability of a grid-connected system. The time domain method using a Poincare map is investigated because it can analyze the system precisely even if it has nonlinear effects. The proposed method is based on simple eigenvalue analysis of a sensitivity matrix between the periodic boundary values. However, generally an inverter is a nonlinear system and its switching timing are dependent on operating conditions. The computation algorithm considering switch timing variations is precisely described. Then application examples of a grid-connected inverter are analyzed, and the results are investigated for validation of the proposed stability analysis method.

ABSTRACT. This paper presents a new DC-AC Interconnected Modular Multilevel Converter (IMMC). The proposed converter produces a sinusoidal output with adjustable voltage and frequency (v/f) suitable for powering ac motor drives. The output voltage/frequency can be varied over a wide range. The proposed converter is a promising candidate for high performance ac motor drives and has the following advantages: no acoustic noise nor EMI; absence of dv/dt related issues due to long motor leads and compact size/volume. The paper details the operating modes, design examples and experimental results using GaN devices.

ABSTRACT. This paper introduces large-signal impedance for the modeling and analysis of sustained resonance in grid-connected converters. The large-signal impedance captures the converter impedance response for different levels of the injected voltage perturbation. Large-signal impedance based calculation of the sustained resonance amplitude is presented for a grid-connected three-phase voltage source converter (VSC). The paper shows that hard nonlinearities, such as PWM saturation, dominate the sensitivity of the impedance response to the perturbation amplitude. The paper also presents modeling of the large-signal impedance for VSC; modeling challenges in the absence of small-signal assumption and their solutions are also discussed.

ABSTRACT. This digest identifies stable resonance frequency range for grid-connected inverter with Grid-Voltage Feedforward Regulator (GVFR), and recommends a conservative LCL filter design method to ensure the robustness against grid inductance variation. Beginning with the current loop stability analysis without GVFR, system poles distribution is analytically studied in z-domain, the critical frequency is therefore calculated as well as the control gain limit. Then, this digest reveals the GVFR would change the system stability in the weak power system, two frequency boundaries and three typical resonance frequency ranges are identified and compared.

ABSTRACT. This paper describes a simple control architecture realized using hybrid feedforward control for a power factor correction (PFC) rectifier based on a four-switch non-inverting buck-boost converter. The converter operates in continuous conduction mode, with smooth transitions between the buck and the boost operations across a line-cycle. To implement the PFC functionality, the controller computes the buck and the boost duty cycles based only on the sensed inductor current and output voltage. The hybrid feedforward controller operation and converter design are verified by experiments on a universal-input, 110-V output, 1-kW four-switch buck-boost PFC rectifier prototype.

ABSTRACT. GaN technology, compared to silicon, benefits from remarkable properties: high breakdown field, high thermal conductivity, higher electron density, and wide band gap. These properties allow: higher voltage, higher frequency and higher operating temperature than silicon, which naturally predestines it to power conversion applications. To illustrate these properties a novel topology of LED driver converter is proposed. The conversion is AC-DC type and does not need any rectifier circuit and any storage DC bus capacitor. The topology is described and studied. Experimental results validates an DC LED demonstrator using GaN transistors.

ABSTRACT. Under unbalanced grid condition, the double frequency power oscillation presents major challenges for three-phase grid-connected converters. To address this issue, three novel topologies are proposed to realize active power decoupling, aiming to maintain dc-link voltage constant while ac grid current balanced and sinusoidal under three-phase unbalanced grid condition. The comparative analysis of the proposed three topologies in terms of the performances including DC ripple voltage, grid current quality, DC voltage utilization, control implementations are also presented. The comparative results are quite different with those in single phase systems. Experimental results validate the effectiveness of the three proposed topologies.

ABSTRACT. Conventional capacitors contribute to a considerable scale of system level size, cost and failure, and suffer from one or more issues on energy density, cost, and reliability. A twoterminal active capacitor, which has the same level of convenience as passive capacitors, is proposed recently to overcome the above issues. In this paper, the modeling of the active capacitor is investigated and a voltage feed-forward compensation scheme is proposed for overshoot reduction. Therefore, the impedance, equivalent capacitance, ESR, and ESL can be specified. A case study based on a single-phase rectifier with an active capacitor demonstrates the theoretical analyses.

ABSTRACT. This paper presents a compact RF power inverter implemented with PCB multi-resonant input filter and later the Faraday shield for driving an electrothermal plasma micro-thruster, mini Pocket Rocket 3.0(miniPR 3.0). This miniPR 3.0 and its driving electronics are low volume and are part of an investigation seeking to add propulsion to low cost CubeSats. Specifically, we present an 8 order multi-resonant input fillter design and demonstrate the converter and the filter successfully driving the miniPR.

ABSTRACT. Linac Coherent Light Source (LCLS) at SLAC is driven by eighty klystrons. Each klystron is powered by a modulator with up to 24 kV pulse at 120Hz repetitive rate. The pulse transformer in the klystron tank will transform the voltage pulse to 360kV to drive the klystron. The modulator also includes a DC power supply as a core bias for the pulse transformer. The eighty core bias power supplies run mostly stably. Some core bias power supplies show some unusual performances. In this paper, the unstable symptoms will be presented and qualitative analyses will be presented as well.

ABSTRACT. Implementing higher voltages in vehicles like 48V mild hybrid or full-hybrid enables CO2 reduction and weight savings. The increase in the voltage demands an accurate and robust protection system again potential faults. Series arc is one of the faults which needs to be detected and addressed before the benefits of using higher voltages in vehicle can be fully realized. In this paper, an efficient arc detection algorithm is presented based on advanced machine learning algorithms for 48V vehicle electrical systems. The results demonstrate that the proposed algorithm recognizes the arcs in the signal with accuracy of more than 99% detection.

ABSTRACT. This paper proposes the minimum switching space vector modulation (MSSVM) scheme for the Z-source inverter, which uses nonconstant modulation depth and boost factor to reduce the average V-A stress on the passives in the Z-network and the number of switching events, thus significantly reducing the converter loss compared to existing constant boost modulation schemes. The average V-A stress on the passives is analyzed. The validity of the MSSVM algorithms and the efficiency improvement are verified by experiment. 

ABSTRACT. This paper proposes a high-efficiency single-phase three-level bidirectional inverter. The proposed inverter has a three-level power switching circuit. It can reduce switch voltage stresses with low harmonic components. It has common-mode capacitors at the ac-filter to suppress the ground leakage current for high power quality. Its circuit operation and control strategy are described. Its common-mode circuit model is discussed. A 1.0 kW prototype has been designed and experimentally tested to verify the performance of the proposed inverter.

ABSTRACT. A novel control strategy to control grid current with only one closed control loop is proposed for grid-connected boost inverters, where identical control structure is employed for its two DC/DC boost converters. The harmonic components of two capacitor voltages could be controlled into almost the same, which will lead to a low distortion of grid current. DC input current ripple is suppressed by introducing the common harmonic compensation components. Moreover, input inductor voltage is predicted and introduced to improve the stability of control system. Comprehensive experimental results are presented to show the effectiveness of the proposed control strategy.

ABSTRACT. An internal paralleled active neutral point clamped converter (IP-ANPC) is presented in this paper. Advantages of the IP-ANPC converter include modularity, reliability and efficiency improvement, capability of interleaving, and better utilization of wide band-gap (WBG) devices. To simplify the operation of the IP-ANPC converter and provide an easy interleaving solution, a logic-based flying capacitor voltage balancing scheme is proposed. The method is efficient and adaptive to all kinds of PWM strategies. Simulation results are presented to validate the proposed topology and balancing scheme.

ABSTRACT. With Direct model predictive control (MPDxC), the width of bounds is observed to regulate THD of a current when MPDxC is used for controlling the current. This paper describes mathematically the linear relationship in between THD and width of the current bounds and, therefore, evaluates THD without running detailed and time consuming simulations. This mathematical function is valid over a range of bound widths for which the current ripple is approximated to be a piecewise linear function. The feasibility of the function is demonstrated through simulations and experimental results of a single phase system.

ABSTRACT. Single phase power converters are commonly employed to integrate renewable sources, such as solar PV or fuel cells. However, they typically require large and limited lifetime electrolytic capacitors to filter large dc side ripple components. Active filtering methods can be used to lower dc capacitor requirements and enable the use of durable and smaller film capacitors. This paper proposes an active filtering topology and simple control scheme that increases component utilization, and decreases ac harmonic content. The final paper will also cover harmonic impact, component sizing, and elaborate upon the controller and plant model of the converter.

ABSTRACT. A zero voltage switching single-phase grid-connected inverter and its zero voltage switching modulation scheme (ZVS SPWM) have been proposed to increase efficiency and power density. An auxiliary resonant circuit is introduced to resonate with the inverter. All the switching devices are zero-voltage switching turned on with ZVS SPWM and the switching frequency is increased to 100kHz. The bridge voltage model of ZVS single-phase inverter is deduced and the influence of resonant process and dead time on the low-order harmonics is evaluated. An improved ZVS control stratage is proposed and verified on a 3kW prototype.

ABSTRACT. Next-generation power networks will contain large numbers of inverters. Inverter models typically have large number of dynamic states, and it is impractical to analyze systems with the full dynamics. We derive a reduced-order model for parallel-connected inverters. Each inverter has an LCL output filter, current and power controllers, and a phase-locked loop for grid synchronization. We outline a structure-preserving reduced-order model for the setting where the inverters have filter components and controller gains that scale linearly with power rating. We model the parallel system as one aggregated inverter with the same number of dynamical states as any individual inverter.

ABSTRACT. In this paper, a Space Vector Modulation for the Three-Level Simplified Neutral Point Clamped (3L-SNPC) inverter is introduced. Models for the DC link dynamics and the 3L-SNPC inverter topology are developed. Different switching sequences are analyzed and compared. The neutral point balancing capability of the inverter is compared with conventional 3L-NPC inverter topologies. Simulation and experimental results prove the performance of the concept.

ABSTRACT. This work presents an analytical model for integrated DCDC converters at high currents. A loss model is construct using parameters extracted from simple simulations or already available parameters in the process manual and are scaled with the size of the device. Thus a target converter for a given power loss or efficiency can be designed choosing the device's size. A Buck and a 3-Level Buck are compared using this analytical model and then implemented in a CMOS process. Validation of the constructed loss model is done through hardware measurements.

ABSTRACT. This Digest presents a modified active neutral point clamped CMOS half-bridge converter, accompanied by a suitable dead time control scheme, that allows for soft-switching of the main switches, voltage balancing among the devices, and achieves a reduction of the maximum transistor voltages that appear during switching transients. The entire power stage or parts of it can be completely turned off which makes the circuit suitable for multi-phase systems and low load operation. Simulation results show that the proposed circuit favorably combines the advantageous aspects of both initially considered HB converters with stacked transistors, i.e., with and without clamping switches.

ABSTRACT. This paper introduces a new hardware efficient fully digital auto tuning ACM controller. The procedure determines the required ACM controller parameters to regulate the output voltage, while maintaining user-specified stability margins and closed-loop bandwidth of the feedback control system. By using system perturbations in the inductor current during converter soft-start and measurements of the state variables, the converter dynamics are identified without the direct extraction of the passive elements. The effectiveness of the digital auto-tuner controller demonstrated on an experimental 500kHz, 12V-to-1.2V digitally controlled synchronous buck converter. The converter soft-start operation takes 2ms, the tuning procedure lasts less than 0.6ms

ABSTRACT. This digest presents an approach towards modeling a dual switch converter operating in discontinuous conduction mode (DCM) using state space averaging. To verify the accuracy of the developed model, a cascaded buck boost converter is used. However, the developed modeling approach is generic for various dual stage converters. The developed state space averaged model allows the application of modern control techniques (e.g. state feedback and linear quadratic regulator control techniques) on dual stage converters operating in DCM. The duty ratio constraint and the correction terms used are driven to accurately predict the high frequency behavior of the system.

ABSTRACT. This digest introduces a high-power-density low-profile dc-dc converter for cellphone battery charging applications. Three alternative topologies – a ZVS-QSW buck, a three-level buck and a resonant switched capacitor converter with customized planar magnetics are compared in terms of efficiency and power density. A prototype 40-W ZVS-QSW buck converter with a PCB area of 79.6 mm2 and component height of 1 mm designed for 5 V – 20 V input voltage range and 3 V – 4.2 V output voltage range is built and tested. The prototype converter achieves a peak efficiency of 96.7% and a power density of 3230 W/in3.

ABSTRACT. As desired in mobile applications, S-Hybrid converter, merging switched-inductor and switched-capacitor operations, can significantly relieve on-board thermal issues by distributing heat over input cable used as inductor and allowing zero on-board inductor. This paper provides detailed small-signal analysis of S-Hybrid converter that considers non-idealities of circuit components. State space averaging is utilized to fully analyze impacts of parasitic components on the converter dynamics. Simplified transfer functions to provide controller design insight are derived and verified in comparison with full modeling and simulation. A controller for a 15W prototype converter is designed to verify the analyses and demonstrate improved transient response.

ABSTRACT. This paper presents a current controller for an automotive LED driver based on a ZVS Cuk converter. It is found that the low-frequency gain of the duty-cycle-to-output-inductor-current transfer function exhibits weak dependence on the output voltage. As a result, wide-bandwidth control of the output current can be achieved using a simple integral controller for any number of LEDs. PWM dimming, which is based on turning the converter on and off, does not require any additional circuitry. Closed-loop current regulation performance and PWM dimming are verified by simulation (including a Spice model of the planar integrated magnetics structure) and by experiments.

ABSTRACT. In this paper we study the modeling and control of an interleaved DC-DC multilevel topology that exhibits a highvoltage gain and a minimum ripple point design. In this configuration, the current ripple cancelation point can be arbitrarily defined according to a desired specification, which represents an advantage with respect to classical topologies whose minimum ripple point is constrained (e.g. by a duty cycle equal to 0.5). We present a generalized model for the converter that is valid for any number of levels and useful for control purposes. Experimental results of the ripple

ABSTRACT. This paper explains a non-isolated DC-DC converter, which is able to change its mode among buck, boost and buck-boost by controlling gate signal. The proposed converter has fewer conducting components and switching components then conventional TSBB(two switch buck-boost) converter. Therefore it reduces power loss than the conventional TSBB. Moreover, the MOSFETs’ source terminals of the proposed converter are directly connected to ground. This topology has an advantage in selecting gate driver ICs.

ABSTRACT. A direct drive of a buck converter is proposed in this paper. It is achieved by delta-sigma modulation at 13.56-MHz sampling without digital PWM. The high-speed gate driver, which is based on GaN-HEMTs push-pull configuration, is employed to drive a SiC power MOSFET at high switching frequency. By delta-sigma modulation at 13.56-MHz sampling, the output voltage of buck converter is directly controlled in the wide range.

ABSTRACT. Due to their switching behavior, DC-DC converters are inherently variable structure systems. Control laws based on sliding mode theory are therefore widely used. Although offering good performance, the downsides of sliding mode control are the requirement of full state information and a variable switching frequency. This paper presents a digital sliding mode controller for a two-phase buck converter. Rather than a direct current measurement, a sliding mode observer is proposed to digitally reconstruct the inductor currents. Moreover, a constant switching frequency is achieved. Simulation results are provided to demonstrate the functionality and performance of the proposed control scheme and observer.

ABSTRACT. A filter-based control scheme is developed for buck-type converters. This approach relies only on a single output voltage measurement to reduce the system cost as well as measurement noise and disturbance injected by output current and/or inductor current measurements. A Lyapunov stability analysis is utilized to demonstrate system stability. Experimental results demonstrate excellent voltage regulation and insensitivity to the load variations.

ABSTRACT. synthesizing the switched-capacitor (SC) converter to perform certain voltage conversions is considered a challenge in SC converter design. This paper presents a systematic approach to synthesize an optimal SC converter for multiple voltage-gain-ratio applications. The optimization methodology is based on the minimum components count. This approach exploits the Makowski canonical model which ensures that the converter is using the minimum number of capacitors based on the Fibonacci fundamental limit. Moreover, using the method presented in this paper, the controller circuit of the designed SC converter is simplified. Case studies are presented to show how different SC converters can be synthesized.

ABSTRACT. Resonant switched capacitor dc-dc converter designs are commonly optimized based on flying capacitance constraints. However, for an actual circuit design, the total available capacitance is further constrained by the need for bypass capacitance at the input and output nodes. This work finds expressions for the voltage ripple and develops a method to optimize the allocation of bypass capacitance so that a circuit designer can make an informed decision about the various trade-offs involving the allocation of capacitance. It will introduce a framework to effectively analyze input and output ripple and then apply this method to different converter topologies.

ABSTRACT. This work examines the cross-coupling over in two-level VSC. This phenomenon has been reported experimentally and preliminary modeling work has been done with simplified converter models. This paper will expand on the existing work by providing complete models of the VSC at both the perturbation frequency and the cross-coupled frequency with DC bus voltage regulation, PLL and current controller. The purpose of this work is to present a comprehensive analysis of possible coupling over frequency in small-signal responses of two-level VSC. Special cases will be studied to obtain insight into the cross-coupled response.

ABSTRACT. Identification of frequency response based on digital controllers can be affected by different noise sources. One of them is the quantization noise produced by the A/D converter, that can increase the perturbation level to achieve a good performance. This can result in excessive disturbance in the electrical quantities of the converter during the identifications process. In this paper the influence of the quantization noise is studied in a controlled simulation environment.

ABSTRACT. The objective of this paper is to develop discrete-time models for grid-connected converters in synchronous reference frame. As the current controllers are generally implemented in microprocessors, some problems that arise in the discrete-time domain are addressed. The time delay of the digital implementation is modeled and its effect on the synchronous transformation is discussed in this paper.

ABSTRACT. This paper presents a new numerical method for circuit simulation with idealized power electronic switches. The method combines the existing numerical integration method TR-BDF2 with a new interpolation technique for the localization of switch events. The interpolation method has an improved accuracy during discontinuous conduction mode. Next to preserving second-order accuracy after interpolation, the method also preserves the capability to suppress numerical oscillations caused by small on-resistances and off-conductances. The performance of the proposed method is compared with the methods used in the existing tools PSCAD and PSIM.

ABSTRACT. An asymmetric current control scheme is proposed to alleviate the PLL effect on stability of the grid-inverter system. The proposed control scheme is simple and practical in the sense that it is derived using the existing current controller. An inverter admittance model including the PLL effect and asymmetric current controller is constructed to evaluate the stability of the inverter-grid system. The relationship between the control parameter and PLL bandwidth is established to ensure the stability. Experimental results demonstrate that the proposed asymmetric controller achieves the stability without sacrificing the PLL bandwidth.

ABSTRACT. Phase-locked loops are used for the synchronization of grid connected power converters. However, the standard PLLs are not able to reject grid disturbances such as voltage harmonics, unbalances or presence of dc components in the measured voltage. Since the response of the power converters depends on the grid phase tracking, it is necessary to ensure an accurate synchronization even under distorted conditions. This paper proposes an enhanced PLL structure, which is able to perform fast synchronization even under weak grid conditions and frequency variations. Due to its low computational burden, the proposed PLL allows its implementation on low cost processors.

ABSTRACT. This paper discusses major aspects to be addressed for reliable determination of the transfer function of a frequency controlled converter through square wave perturbation. The square wave as a multi frequency perturbation allows to determine the transfer function with fewer simulations than classical methods. However, special care has to be taken in order to obtain valid frequency responses. Especially, matching pairs of distortion frequency and amplitude need to be derived. Furthermore accuracy of steady state determination and influence of aliasing effects must be considered. The simulation results are verified through measurements using a setup with the same perturbation principle.

ABSTRACT. In power electronic applications, the most imported design points are efficiency and size. One approach is to increase the switching frequency of the semiconductors to reduce the size of passive components. But smaller passive components increase the dynamics of the system and the control system also has to handle these higher dynamics. This paper presents the control of a phase shifted resonance full-bridge high-dynamic DC-DC converter and shows that an FPGA-based control is a feasible option, not only to control this converter  but also for future wide-bandgap applications, where the switching frequency can be dramatically increased. The control results are compared between an FPGA and an industrial microcontroller with the same control structure

ABSTRACT. This paper proposes to use statistical model checking (SMC) for performance evaluation of finite control set model predictive control algorithm applied to power electronics converters. SMC is simple to implement, intuitive and it requires only an operational model of the system that can be simulated and checked against properties. Device under test for control algorithm application in this paper is a standard 2-level voltage source converter (VSC). The performance of control algorithm is verified using UPPAAL SMC toolbox and the behavior is compared to simulation results obtained from equivalent Simulink model and measurements from the experimental set-up.

ABSTRACT. This paper provides a tutorial on how to program Texas Instruments™ (TI) TMS320F28335 Digital Signal Processor (DSP) through Code Composer Studio (CCS) version 6 and MATLAB Simulink Embedded Coder. First it shows how to setup Simulink and Embedded Coder and produce code to program TMS320F28335 and variant of TI’s C2000 DSPs. It describes how to interact between MATLAB 2015b and CCS V6 and provides an explanation of the vital steps and settings needed to program the DSP. Basic functions such as PWM, ADC, and proportional-integral controllers are explained. Finally, closed loop control model for a micro-inverter topology is developed.

ABSTRACT. Power-hardware-in-the-loop (PHIL) is a simulation tool that supports electrical systems engineers in the development and validation of novel, advanced control schemes that ensure the robustness and resiliency of microgrids that have high penetrations of low-inertia variable renewable resources. This paper addresses issues related to the development of a PHIL interface that allows testing hardware devices at actual scale. With PHIL, the impact of the device under test on a generation or distribution system can be analyzed using a real-time simulator (RTS). PHIL allows for the interconnection of the RTS with a 7 MVA power amplifier at National Wind Technology Center.

ABSTRACT. This paper presents a new passive filter for gridconnected converters, named the LCPSL filter, which utilizes both the parallel and series LC trap branches to suppress the harmonics at switching frequency and its multiples. Particularly, the LCPSL filter can provide more attenuation and quality factor at the selected frequencies, and inherit the merits of the traditional LCL filter with -60dB/dec attenuation rate in high-frequency band. The basic parameter selection criteria and the parameter design procedure of the LCPSL filter are introduced. Besides, considering the simplicity of the single-current loop control, the stability regions of the resonance frequencies are derived for the filter design. Finally, the superiority and effectiveness of the proposed filter are proved by simulation results.
 

ABSTRACT. A grid-connected inverter is equipped with an LCL filter after its output. This filter has resonant characteristics which have to be suppressed. There is inevitable control time delay which degrades stabilities and damping effects of the inverter. This paper proposes a simple and effective compensation of the delay to improve the damping effects. It is based on an estimation method of future state values advanced by the delay time. The proposed method is applied to the grid-connected inverter control and its effectiveness is investigated and validated through transfer functions of the regulated current errors by experiment.

ABSTRACT. Solenoids are widely used in industries as a competitive replacement for mechanical actuators. However, their coil inductance and electromagnetic force vary non-linearly with position and controlling them can be a significant challenge. This work aims at developing a servo control scheme for the solenoid using Augmented Feedback Linearization (AFL). The AFL controller includes classical current regulation, reduced-order feedback linearization and error integration. The control scheme is formulated and a multi-rate state feedback motion controller is designed to achieve closed loop position regulation. The control algorithm is verified using experimental results and shows superior performance over classical control techniques.

ABSTRACT. This digest presents the analysis and design of an adaptive parameter estimator for power electronics circuits. Adaptive parameter estimation has been demonstrated to be a useful technique for enabling novel control and monitoring techniques for power electronics systems. We present an analysis of factors that affect the performance, stability, and feasibility of a gradient-type parameter estimation, along with simulation and experimental results that validate the analysis. Moreover, we derive and demonstrate design techniques to improve the convergence speed and robustness of the parameter estimation.

ABSTRACT. This paper presents thermal characteristics of rotor-side converter (RSC) in DFIG wind turbines (WTs). A numerical thermal model is developed to obtain instantaneous junction temperature of power devices for a wide operating range of RSCs. Thermal performance of four RSC candidates, including Si IGBT based 2L/ 3L-NPC/ 3LANPC RSCs and SiC MOSFET based 2L RSC, are analyzed and evaluated. The results show that Si 3L-ANPC RSC and SiC 2L RSC achieve superior thermal performance compared to traditional Si 2L/ 3L-NPC RSCs, thus leading to higher power density, lifetime and reliability of RSC in DFIG WTs.

ABSTRACT. This paper explores new methods to optimize and compare a variety of switched-capacitor (SC) DC-DC topologies that can be operated in a resonant mode. A figure of merit is developed that is a proxy for minimum achievable power loss, based on conduction and frequency-dependent losses in the active semiconductor components. Similar to past work on pure SC converters, the method leverages a charge-multiplier approach and is used to show the impact of energy or area constraints on passive components. An analysis and detailed breakdown is provided for several common and emerging resonant-SC architectures.

ABSTRACT. This paper proposes a hybrid electronic and magnetic structure that enables transformers with "fractional" and reconfigurable turns ratios (e.g. 12:0.5, 12:1, 12:2). This functionality is valuable in converters with wide operating voltage ranges and high step-up/down, as it offers a means to reduce copper loss within the transformer while also facilitating voltage doubling and quadrupling. We introduce the principle of operation of the structure and present models for its magnetic and electrical behaviour. An experimental prototype capable of accommodating a widely varying input (120-380 Vdc) and output (5, 9, 12V) validates the operating principle and modelling of the proposed structure and achieves conversion efficiencies between 93.4% and 95.7% at 25-36 W.

ABSTRACT.   This paper presents a comprehensive analysis of step-down multi-level flying capacitor converters in discontinuous conduction modes of operation. In addition to that, a novel controller architecture is introduced for the operation of the converter under light load conditions for a wide range of conversion ratios. The effectiveness of the introduced controller is demonstrated with a wide range input voltage 6V < V_IN < 12V, and the maximum output current of 3A practical prototype, operating with variable switching frequency 20 KHz <fsmax < 500 KHz

ABSTRACT. This work investigates the origins of the capacitor voltage imbalance in practical implementations of flying capacitor multi-level converters. It is shown that the source impedance and input capacitor can have a drastic impact on the capacitor voltages. An FCML converter with an even number of levels (compared to odd) has significantly better immunity to this disturbance. In addition, the gate signal mismatch from half-bridge gate drivers will lead to capacitor imbalance and an alternative gate drive power supply circuit is designed to address this problem. Lastly, variations of switches’ on-resistance are found to have a small impact on the balancing.

ABSTRACT. In this study, a controller for switched-resonator converters operating in the 10MHz range is presented with self-tuning capabilities. The control scheme provides a fast and accurate two-stage lock-in procedure to ensure zero-current switching at high frequencies, maintaining low control workload. The various modules of the controller are detailed, including the self-tuner based on a digital delay-locked loop, and a Rogowski-type on-board zero-current detector. Simulation and experiments were conducted to verify the design of the controller using a gyrator resonant switched-capacitor converter as the switched-resonator power stage.

ABSTRACT. High-frequency power conversion is useful for miniaturization of power electronics, but requires low loss passive components to achieve high power densities without thermal issues. This paper investigates the lowest achievable ESR of a resonant tank using an air-core inductor with a single-layer foil winding and commercially available capacitors. A loss model is presented and online catalogs of multilayer ceramic capacitors are searched for components that can provide a low ESR when combined with an optimally designed inductor for various resonance frequencies. The resulting resonator has a measured sub-m$\Omega$ ESR and high efficiency with 250 V dc rating in a 1 $cm^3$ volume. The resonant tank, when used in a resonant switched-capacitor converter, can theoretically handle up to 12 kW with only 2 W loss, and the power converter itself will be limited by the power density of switches and interconnects rather than by passive components.

ABSTRACT. Under wide-range variations in output current and voltage, dual-active-bridge (DAB) converter can operate with increased conduction and switching loss. A variable frequency-based power modulation scheme for an LC-type series resonant DAB converter is presented to achieve minimum-tank-current operation along with full-range soft switching. The proposed minimum-tank-current operation establishes an in-phase relationship between tank current and secondary-side voltage (low voltage and high current), which allows the switching devices of DAB converter to operate in soft-switching region. Resonant transitions of parasitic capacitances within the dead-time interval of switching devices are considered to avoid incomplete soft switching. Simulation and experimental results show the effectiveness of the proposed method with a maximum efficiency of 96.8 %

ABSTRACT. Wireless power transfer is emerging as the pre-eminent way to charge electric vehicles, but there appears to be no fair way to measure power transfer. In this paper, transfer-power measurement (TPM) is introduced. TPM employs non-contact sensing elements to measure magnetic field from wireless power transfer and calculate the real power propagating through space. TPM provides fair metering because individual losses from the transmitter and receiver are disaggregated. Signal and data processing as well as a calibration method are discussed. Experimental results demonstrate a fair method of metering the real transfer power with low estimation error.  Fair metering incentivizes businesses and individuals to make choices that conserve energy and advance technology by providing more information and by properly assigning the financial loss.

ABSTRACT. Zero voltage switching (ZVS) assistance required for a series resonant converter (SRC) operating with constant current input is analyzed in this digest. Passive ZVS assistance circuit becomes impractical to ensure ZVS for the entire load range. Active ZVS assistance is essential for achieving ZVS over wide load range. Design and control of an active ZVS assistance circuit are presented here. Limitations of such active assistance circuit with mitigation method are also discussed in this digest. Finally, hardware results are presented for an SRC operating from 1A current source with 0.33A regulated output current, for a load range of 100W-1kW.

ABSTRACT. A multi-objective optimization methodology is presented for capacitive wireless power transfer (WPT) systems for electric vehicles. By quantifying the tradeoff between power transfer density and efficiency, this multi-objective optimization can inform engineering decisions. The capacitive WPT system utilizes L-section matching networks with air-core inductors and capacitors realized using the system’s parasitic capacitances. The optimization methodology incorporates fringing field safety considerations and constraints on matching network capacitances and inductances. The proposed models are validated using a 589-W 6.78-MHz 12-cm air-gap capacitive WPT prototype, which achieves 19.6 kW/m2 power transfer density and 88.2% efficiency.