ABSTRACT. The flying capacitor multilevel (FCML) converter has shown promise for high step-up/down conversion ratios due to its relatively low switch stress and small inductor volume. For higher level-count (N>2) variations of this topology, there is limited research on resonant mode operation, despite its promise to yield considerable performance benefits. Using resonant mode operation, magnetic volume may be further reduced, transient response increased, and zero-voltage/zero-current switching (ZCS/ZVS) enabled at the cost of fixed conversion ratio operation. This work presents and analyzes a clocking scheme required to operate an N:1 FCML converter both at-resonance and above-resonance, while maintaining minimum current ripple for reduced losses. A complete derivation is presented, enabling the calculation of precise phase durations as a function of switching frequency. Moreover, a 5:1 FCML hardware prototype is demonstrated, verifying intended operation both at and above resonance, in addition to highlighting the achievable loss reduction with the proposed switching scheme.

ABSTRACT. The digest proposes a digital estimator-based time-optimal control method to achieve ultra-fast transient response under large-signal output voltage reference transients. The proposed method mitigates the effects of various circuit delays in a practical hardware implementation, and is particularly effective when the desired response times are shorter or comparable to the delays. The approach is verified on an eight-level digitally controlled GaN-based FCML prototype. Experimental results are shown for step reference transients from 25 V to 180 V and back at vin = 200 V and R = 100 Ω, with measured response times in the range of 500 − 600 ns

ABSTRACT. Ensuring that the flying capacitor voltages are balanced is critical to the operation of flying capacitor multilevel (FCML) converters. This paper systematically explores the voltage balancing limits of coupled inductors in FCML converters. By applying superposition, the steady-state voltage balancing is predicted for a generic balancing and unbalancing mechanism acting on the flying capacitors. It is shown that coupled inductors can provide strong and robust voltage balancing for flying capacitors coupled in multiple phases. The theoretical predictions are verified using simulations and experimental results with a four-phase, three-level FCML converter.

ABSTRACT. This work presents a practical method for estimating the flying capacitor voltages in flying capacitor multilevel (FCML) converters in real-time via direct measurements of only the input voltage and switched node voltage. The proposed technique greatly simplifies the circuitry required to sense flying capacitor voltages. The estimation procedure is designed to be compatible with arbitrary FCML modulation strategies, making it highly suitable for feedback control of the flying capacitor voltages. We analyze the observability of the flying capacitor voltages under practical sampling constraints, and present a real-time implementation on a commercial digital signal processor.

ABSTRACT. This work explores analysis and optimization of multi-winding current-ballasting in high-frequency coupled magnetic structures that can be used with direct-conversion resonant switched-capacitor (ReSC) DC-DC converters. To achieve high-efficiency and high power density as frequencies approach 10s to 100s MHz, current ballasting can play a key role in mitigating AC conduction losses. We develop an intuitive model based on second order system dynamics which is verified using more rigorous state-space analysis. We determine per-winding optimal current density profiles which achieve lowest loss based on load conditions and prove that arbitrary ballasting can be achieved by presenting a unique (flying) capacitance to each winding in a multi-phase ReSC architecture. A hardware prototype with different planar air-core structures is proposed for validation.

ABSTRACT. The phase-locked loop (PLL) may behave as a negative resistance within its bandwidth, which may lead to system instability, especially in weak grids. This undesirable property of the PLL may be offset by so-called active damping. Nevertheless, the physical insight of how the active damping offsets the adverse PLL impact is not fully understood. To this end, the properties of different active-damping methods are analyzed, with the focus on the q-to-q coupling of the input admittance. The influence of the active damping is illustrated through equivalent-circuit modeling.

ABSTRACT. Second Order Generalized Integrator (SOGI) cells are used for notch filtering due to their simplicity and their harmonic rejection capability. SOGI and Dual SOGI (DSOGI) filter cells, combined with Frequency Locked Loops (FLL) to adjust the notch frequency, are commonly used in both 1phi and 3phi grid following (GFL) power converters for synchronization, i.e. SOGI-FLL and DSOGI-FLL. The FLL relies on a gradient descent method to minimize a cost function built up around one inner SOGI cell variable, e.g. the in-quadrature voltage estimation, and one outer variable, i.e. the error signal due to the SOGI filter cell. As a result, the FLL manages relatively large DC offsets and harmonic distortion passing through the outer SOGI cell variable, which deteriorates the frequency estimation and, then, the SOGI-FLL performance. To attenuate such issues, the method proposed in this digest only uses inner SOGI cell variables. It minimizes deviations among the estimated grid frequency and the frequency of the signal across the SOGI cell, which is detected through the Teager Energy Operator (TEO). The proposal is validated in simulation and experimentally.

ABSTRACT. MMCs have emerged as an excellent option for medium/high voltage DC/AC or AC/DC applications due to their modularity and scalability. Despite this, DC/DC MMC operation isn’t common. Even when DC/DC MMC operation is achieved, the submodule (SM) capacitor sizing challenge is enormous. Recently proposed switching-cycle-control (SCC) solves this challenge, enabling MMC DC/DC operation with small SM capacitors. Despite its advantages, SCC has scope for improvement, especially if converter operating region is defined. This paper develops a new MMC topology for DC/DC operation while also proposing two SCC-derived control techniques. Concept is verified using simulations and 18kV experimental test-bench is presented.

ABSTRACT. The paper focuses on the galvanically isolated series-resonant dc-dc converter (SRC) operating at low values of the quality factor of the resonant tank. This topology is considered as a bidirectional step-up front-end dc-dc converter with buck-boost functionality for integration of renewable energy sources or battery energy storage in dc microgrids. The main aim of the study is to develop a universal dc-dc converter, which can operate with different input voltage sources such as PV modules or batteries. The paper presents an input source identification method capable of distinguishing between a PV module or a battery energy storage connected to the input. The developed algorithm is based on the I-V curve scanning of an input source. Experimental results show the performance of the developed algorithm in the identification of a PV module under different partial shading conditions and a battery with subsequent charging or discharging.

ABSTRACT. The Dual-Active-Half-Bridge (DAHB) converter is being explored as a candidate for applications requiring low cost, reliable and power-dense power conversion. This paper describes the discrete modelling of a DAHB converter, working in single-phase shift mode (SPS). A discrete model allows a very accurate description of high-frequency effects, phenomena that cannot be effectively predicted with averaged methods in some cases. This is especially useful if the half-bridge capacitance is small and the resonant frequency is comparable to the switching frequency. The modelling approach generates an accurate dynamic model, as well as a steady-state model predicting very precisely the current and voltage wave-forms, which in turn allows making an optimal design based on numerical methods. The model has been validated with time-domain simulations, both in dynamic and static operations. .

ABSTRACT. Flyback converter is well-known topology in many applications that requires galvanic isolation or a high ratio conversion rate. This paper presents a new topology of an isolated switch mode power-converter. The quasi-resonant fixed-frequency converter is based in flyback family operating in discontinues current mode (DCM). The converter uses zero-voltage-switching (ZVS) techniques to improve the converter efficiency. The converter comprises coupled inductor, two switches, and a diode on the primary side. At the secondary side, there is a diode, coupled inductor, and output capacitor. The new topology enables to run the converter at constant switching frequency while preforming a quasi-resonance behavior. In this paper, the innovative topology is presented. First, the circuit operation steps are described, then the analytical equations are developed. To validate the proposed theory a case study was made; the circuit was modeled by PSIM simulation tool. The results are acknowledged that the innovative topology can decrease the circuit losses dramatically throughout all operating points.

ABSTRACT. High-performance hard-switched converters suffer from significant voltage overshoot and ringing upon switching transitions. This increases switch stress and electromagnetic interference, while also reducing reliability. Attempts to mitigate these drawbacks with increased gate resistance, or a slower switching device, yield reduced efficiency. Large bulk capacitors are typically required to meet voltage ripple constraints under load. As such, their package inductance is considerable and they may be placed far from the power path. A smaller decoupling capacitor is often placed near the switching devices in order to reduce overshoot. In this work, a simple circuit model is developed to describe converter operation during the switching transition, and an optimal decoupling capacitor size is proposed. The analyses are validated via experimental measurement of double pulse tests on a variety of hardware prototypes.

ABSTRACT. This paper presents a simple method to improve dynamic characteristics of on-shelf commercial PFC controllers, in particular reducing the DC link voltage undershoot (response to a step-like load power increase (US)) with an additional reduction of total harmonic distortion (THD). It is well known that a wide voltage loop bandwidth leads to decrease in voltage undershoot, but may affect AC-side current quality. However, adding a notch filter in series with the existing voltage loop regulator prevents THD degradation. Guidelines to achieve the desired values of the two mentioned performance merits are provided for a commercial PFC rectifier board.

ABSTRACT. This paper discusses a different auxiliary source circuit topologies and the introduction of control strategies used for auxiliary source circuit, in favor of bulky electrolytic capacitor replacement in capacitor-supported power electronic systems. DC-BUS capacitor is widely used in grid-tied power converters for power balance, voltage ripple limitation, and short-term energy storage. Auxiliary source circuits are key components to improve the reliability of the dc-links qualitatively, making a great effort to divert the instantaneous pulsating power into extra reliable storage components. Topologies and control strategies of an auxiliary source circuit are comprehensively reviewed in this paper. Additionally, detailed explanation, comparison, and discussion on the auxiliary source circuit are achieved.

ABSTRACT. Implementation of Burst Control based on Sigma-Delta Modulation in Low-Cost Microcontroller.

ABSTRACT. This paper presents a new method for controlling variable frequency multiphase buck converters within a switching-synchronized sampled-state space (5S) framework. Cycle-by-cycle digital control of both current and voltage at the MHz switching frequency range for each phase within this framework not only results in fast transient response to load and disturbances, but also fast settling. A new method for cycle-by-cycle averaging is introduced that is more robust to fast disturbances and switching transients, which become problematic as the number phases or the switching frequency increases. Very fast phase locking after a transient is ensured using a new 5S phase lock loop. Additional benefits include ease of design and implementation. Theory and modeling are presented, and results are demonstrated in hardware and simulation.

ABSTRACT. Analysis of complex transfer functions poles (CTFP) is formulated in this paper to complete the application of complex transfer function (CTF) in 3-phase current control analysis. It serves as a straightforward tool to directly compare and analyze the transient responses of various current control strategies implemented on different reference frames, which conventional pole analysis of real transfer functions (RTFs) or bode diagram fail to capture.

ABSTRACT. A modular three-phase Boost-Buck dc/ac Inverter (BBI) is presented. The BBI has the advantages of voltage step-up/step-down capability, high-quality/low-harmonic output voltage/current waveform and high efficiency. Extensive comparative evaluations are made between the BBI and the conventional two-level voltage source inverter with a boost dc/dc stage (B-VSI). It is shown that, compared to the B-VSI topology, the BBI topology has (a) much lower THD of the output current, (b) much lower CM voltage and hence CM current, (c) much lower switch device voltage stress and losses and (d) much lower rms current ripple in the dc link capacitor.

ABSTRACT. The stringent performance requirements for power-electronic converters in electric vehicles necessitate advanced cooling techniques and device structures. This paper presents a thermal-management solution for automotive power-electronic converters that leverages top-side-cooled GaN devices and liquid-based jet-impingement cooling for enhanced thermal performance. Stereolithographic 3D printing allows the nozzle structure to be customized according to PCB geometry, minimizing volume overhead. Deposited boron nitride is used to create a thermal interface material (TIM) with high thermal conductivity and electrical isolation to separate the GaN devices from the coolant, minimizing the impact of the TIM. Experimental results using 1 L/min fluid flow show thermal resistances as low as 1 degree C/W with a heat flux of approximately 250 W/cm^2, demonstrating the effectiveness of the proposed solution.

ABSTRACT. This paper presents a novel approach to power converter design and optimization, where the optimal component characteristics for a DC-DC converter architecture are selected given a specified objective function and various design constraints. Extensive amounts of component data available on commercial distributor sites are used to train supervised regression Machine Learning (ML) models used throughout an optimization algorithm. Using ML-based techniques allows the data-based optimization task to become tractable over a large design space. The developed tool can be used to compare performance measures across converter topologies or component technologies and to predict performance contributions of individual components. As an example, optimized designs of 48-to-12V, 20A buck converters based on GaN and Si MOSFETs are compared in terms of losses, size and cost.

ABSTRACT. Previous work has shown that real-time electromagnetic models can be used to enable an augmented reality-based visualisation of the magnetic field around a single wire over a ground plane. However, as model complexity is increased, the memory usage and simulation times increase considerably, to the point that it would be impossible to use in a real-time visualisation. In this paper, previous efforts are substantially improved by incorporating the Fast Multipole formulation of the Partial Element Equivalent Circuit method alongside the PRIMA model order reduction algorithm. A significantly larger model with 11156 ODEs has been simulated in real-time for smooth augmented reality visualisations. Experimental measurements are used to validate the accuracy of the simulation models used.

ABSTRACT. Incorporation of a microcrystalline diamond layers in silicon chip substrates of 65 nm based LDMOS switches presents a heat spreading effect that reduces hotspot temperatures. The extreme heat conductivity of diamond, 1500 W/(m*K) , four time higher than copper and 10 times higher than silicon, reduces the thermal flux and hence the junction temperatures. The introduction of diamond layers displays a thermal short that drastically reduces temperature variations across the chip. Comparative characterization of LDMOS devices displays a 20 degree reduction in junction temperature when operated in saturation. A tripling in energy to destruction of a device in UIS switching mode is observed in a device where a microcrystalline diamond layer is integrated.

ABSTRACT. Communication inside a power converter could be beneficial in a variety of ways. It naturally gives hardware abstraction, meaning that the behavior of power stage terminals is independent of hardware design. Flexibility is another important communication benefit, since different data could be exchanged between a controller, the gate drivers, and sensors. Since modern gate drivers are equipped with different sensors for protection purposes, in conjunction with communication, data sampled from gate driver sensors could be sent to the controller and reused for control purposes. Therefore, fewer sensors would be needed for the system, and controller hardware could be simplified. And finally, communication between different levels and nodes in the power electronics systems allows for the implementation of distributed control. This paper gives an example of a power converter architecture that uses communication between nodes (gate drivers and the sensors) to achieve flexible and distributed control.

ABSTRACT. This paper presents the control of a modular and scalable three-phase AC-to-AC converter that features small arm inductance and DC cell capacitance. While the phase-leg output inductor current is controlled by its average value controller, the arm inductor currents are under the peak-current mode control so that the arm inductance can be selected to be very small and voltages of cell capacitor banks within the phase-leg can be balanced within one switching cycle. An interleaving between the pulse width modulation carrier signals of three phases are implemented to reduce the common-mode noise generated by switching the 1.7 kV SiC MOSFETS. One main controller and six phase-leg controllers are utilized to enable the scalability of the control system. Experimental tests validated the proposed control system for the converter.

ABSTRACT. This paper presents a rapid current discharge circuit for single and multi-stage high current coilgun. The circuit eliminates an undesired braking force, which is developed due to a residual current, when the projectile passes the center point of an energized coil. This is done by rerouting the coil current towards an alternative, quick discharge path, where it is damped to zero. Utilization of the discharge circuit is especially advantageous in multi-stage coilgun systems, as the design of the discharge circuit is done once for the “worst case scenario” and applied to all the coils. It guarantees a safe operation of all the switches, with minor effect on the system performance. The discharge circuit operation has been validated by an experimental prototype rated for 450V, demonstrating rapid coil current discharge for braking force mitigation.

ABSTRACT. The Hardware-In-the-Loop (HIL) approach is widely interpreted as a valuable prototype tool for a grid-connected converter (GCC) development and validation of the converter as well as the power grid at all levels. The paper is based on the controller hardware-in-the-loop (C-HIL) approach that demonstrates the Typhoon HIL control center which provides remarkable efforts to test and optimize the GCC control loops. It performs the test and optimization of the converter harmonic performance, optimization of the grid filter, injection of active and reactive power into the grid and comparison of the model with and without implementing Particle Swarm Optimization (PSO) technique.

ABSTRACT. Connecting multiple power converters in series and/or parallel has significant benefits: increased reliability/reparability, reduced individual device stress, and higher operating frequency. Modular systems require a control scheme to ensure equal sharing of power, which may be centralized, distributed, or decentralized (no communication between modules at all). Decentralized control has a clear advantage as it is the most scalable and robust to single-module failure. In this paper, we analyze a nonlinear decentralized control scheme which has been shown to be suitable for modular power sharing. The non-linear control law cannot be analyzed using the common and powerful tools for linear systems.  Here we use describing function analysis and phase-plane analysis to prove the non-existence of limit cycles for a single module and to examine its transient response. Further, we verify the behaviour of the controller by experimentally demonstrating the performance of the controller for a variety of control-parameters. Finally, we present experimental validation of power sharing.

ABSTRACT. Power factor correction (PFC) circuits are used for many electronic circuits fed from the electrical grid. Today, the most popular PFC is based on a Boost converter, which provides a high voltage at its output. Since many loads require a lower voltage than the grid voltage, the BOOST PFC compels an additional level of conversion between the PFC and the load. This paper proposes an innovative topology of a PFC rectifier, a descendant of Buckboost topology, that supplies three levels of output voltage. The t-type Buckboost PFC rectifier (TBPR) is a unique duo to its ability to be step-down \ up the mains voltage in a single stage. The operation principles of the rectifier on continuous conduction mode (CCM) are presented, and the proposed theory is validated by simulations for closed-loop operation.

ABSTRACT. Abstract – A non-isolated high conversion ratio boost extending method is presented. The extender approach hinges on the stacking of series capacitors, to achieve high voltage gain, along with high efficiency. The series capacitor stacking method, facilitates a high efficiency single cycle energy conversion that eliminates the need in multiple consecutive conversions typical for high gain non-isolated converters. In addition, the topology and stacking approach features low voltage stress across the diodes and stacked capacitors. An analysis of the voltage gain and component stresses for the general case is carried out, and experimental prototype of 125W is developed and built in the laboratory. The converter attains maximum efficiency of 95.5% at input voltage of 20V and output voltage of 210V. The experimental results are in a good agreement with theoretical predictions.

ABSTRACT. In this work, key aspects of the insulation coordination in a 6-kV, 1-MW power electronics building block (PEBB) is presented. Each PEBB can be stacked in various series-parallel configurations as part of a modular multilevel converter (MMC) sustaining at least 30-kV common mode. Ansys and COMSOL Multiphysics was used for electric field (E-field) analysis to aid in the design of component- and system-level insulation. Design and analysis of a PCB-based bus with capacitor daughtercards and high voltage considerations for the cooling system are presented. Insulation key systems were verified to be partial discharge (PD) free at their maximum voltage rating.

ABSTRACT. The decreasing system inertia of power systems, due to the increasing amount of power-electronic interfaced units, can lead to frequency stability issues. Usually, when it comes to frequency-supporting control algorithms, only power-electronic generation units are considered. However, in this paper a load control for a solid state transformer is introduced, which provides frequency support to the grid. Moreover, the German grid will be modeled using the common turbine-governor-generator model and an estimated system inertia will be used. Lastly, the solid state transformer control will be tested and compared to the conventional control using the derived grid model within a Simulink/PLECS simulation environment.

ABSTRACT. Highly dynamic Power Hardware-in-the-loop (PHIL) systems are nowadays important in the development process of grid-connected converters or motor drives. The results of such systems are highly influenced by the chosen Interface Algorithm (IA). In this paper, the characteristics of the most common IA are discussed and their typical applications are outlined. Afterwards, suitable IA for grid emulation with highly dynamic PHIL systems are analyzed more closely. To validate the stability of the PHIL testbench, the transfer func-tions of all included parts are derived and the Nyquist stability criterion is proved. Additionally, the accuracy of the different IA is considered. Moreover, the developed emulator based on a new topology, the Series Hy-brid Converter, is introduced and measurement results for high bandwidth grid emulation with suitable IA are shown and the results evaluated.

ABSTRACT. Simulating electrical grid with switching devices poses a challenge requiring a detailed Electro-Magnetic Transient (EMT) simulation in time step significantly smaller than a switching cycle, yet the grid side cannot be simplified below a certain level posing a simulation complexity challenge. Typhoon HIL SW is used to simulate grid behavior for Synchronverter inertial response evaluation. Utilizing the interface for C code integration within the environment, the development of control algorithm is done in a rapid prototyping approach, while the exact same code to be deployed in a real device is used to control RT simulated inverter on the level of switching topology.

ABSTRACT. This digest introduces impedance control network (ICN)-based high frequency inverters for capacitive wireless power transfer (WPT) systems suitable for electric vehicle (EV) charging. The ICN helps to combine the power from two out-phased inverters, thereby increasing the power transfer capability of the capacitive WPT system. A comprehensive design methodology to design an ICN-based capacitive WPT system is presented. Furthermore, an auxiliary ZVS circuit to achieve zero voltage switching (ZVS) operation of all the inverters’ transistors is also designed. Compared to the existing approach of achieving ZVS in ICN based converters, the auxiliary ZVS circuit-based approach reduces the circulating currents in the system and ensures equal power processing by both the inverters. For experimental validation, a 6.78-MHz 12-cm air-gap kilowatt-scale ICN based capacitive WPT prototype system is designed, built and tested. The experimental results are in good agreement with theoretical predictions.

ABSTRACT. In the modern world the demand for wireless power delivery systems increases rapidly. With increased demand for transmitted power and variety of applications, maximum efficiency operation methods are required. There exist various applications and numerous methods to achieve maximum efficiency. However, some applications prohibit communication between transmitting and receiving sides, and information regarding system’s geometries does not exist. We propose a simple and robust method to meet maximum efficiency operation for this family of applications. By adding a third winding, maximum efficiency is achieved. A novel method of efficiency maximization for wireless power delivery systems is presented in this article.

ABSTRACT. Capacitive-based wireless Power Transfer (CPT) has been proven as a reliable and efficient technology for many applications ranging from small appliances such as biomedical implants to high power electric vehicles. The energy in CPT systems is being transferred by means of an electric field, which implies that the system must comply with safety regulations regarding human exposure to EMF emission. This study introduces a methodology of applying a multistep simulation for estimating electric fields, generated by CPT systems. No prior knowledge of the voltages on the capacitive coupler is required. Due to the sequential nature of the proposed workflow, it can be executed either manually or as a part of an automated procedure. The proposed approach is demonstrated in this study on a wireless charger for a toddler’s rechargeable car.

ABSTRACT. This digest presents a power control of a high-frequency power inverter system for plasma generation. Plasma generation requires a high-frequency inverter to rapidly adjust the output power in step changes within a few microseconds such as the pulsed plasma in semiconductor processing. The parallel connection of resonant inverters such as class $\Phi_2$ inverters enlarges the output power but additional power combining networks are needed, which causes additional losses and complexity. To overcome these issues, we propose a new designing method for a class Phi2 inverter by selecting the ratio of reactance to the resistance in the load tank network to maintain high efficiency over the designed operation range and keep the linearity of the output power to some extent. The proposed inverter operating at 13.56 MHz with output power from 300 W to 1121 W was real-time controlled with step changes by an FPGA board. The step-change transition lasts less than 0.5 microseconds. The efficiencies are over 90%. A heat sink will be implemented to operate the system in a continuous way in the full paper. Also, the specific design and implementation details of the proposed inverter system will be presented.

ABSTRACT. This paper presents a machine learning-based characterization of the quality (Q) factor in spiral coil designs for wireless power transfer systems operating at MHz frequencies.Due to skin and proximity effects, at such frequencies, it is challenging to estimate the Q factor of the coupling coils, which is a critical parameter to determine the system's efficiency. A three-dimensional (3D) electromagnetic (EM) simulator allows us to precisely analyze the performance of different coil structures. However, the long processing time in the simulator is a bottleneck for quickly optimizing the coil design. To overcome this issue, we here propose a design method with a feed-forward neural network (FNN) to predict the parameters of the spiral coil. The FNN leverages the data set collected via the 3D quasi-static EM field simulator to train a predictor using the stochastic gradient descent algorithm. After optimization, the FNN model estimates the Q factor of the spiral coil without any delay. The proposed algorithm shows an accuracy larger than 96% under an arbitrary structure. Moreover, the proposed coil design method significantly reduces the computation time and hence, the analysis complexity. 

ABSTRACT. Peak and Valley Current Control (PVCC), is a control technique that uses double compensation ramps, that allows control bandwidths that exceed half the switching frequency of the converter and is able to reach higher bandwidth than classical control methods at a given phase margin. The present paper focus in an in-depth analysis and discrete modelling of the PVCC control scheme for a buck type converter and presents experimental results that demonstrate the PVCC capabilities