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In this paper, a modified selective harmonic mitigation pulse amplitude modulation (SHM-PAM) is presented to be capable of canceling all triplen harmonic orders and suitable for single-phase application of five-level type of voltage source inverters. To this end, a new constraint is established for the two switching angles (α1, α2) to derive the new formula for the harmonics’ amplitude, which results in self-elimination of all triplen harmonics (e.g., 3rd, 9th, 15th, …). The fifth and seventh harmonic orders are mitigated through normal operation of the proposed SHM-PAM technique. It is also shown that the proposed technique is extendable to other multilevel voltage waveforms and a flowchart of self-elimination of all triplen harmonics has been presented. Mathematical analysis supported by experimental investigations show the desired performance of the proposed SHM-PAM algorithm on a two-cell single-phase cascaded H-bridge inverter as a typical five-level configuration in dealing with linear and nonlinear loads. Then, it is demonstrated that the maximum number of harmonic orders would be controlled with the minimum number of available angles in a low switching frequency voltage waveform. [ABSTRACT FROM AUTHOR]

In this paper, a novel space vector modulation (SVM) strategy is proposed and designed for dual three-phase three-level motor drives based on vector space decomposition (VSD), which could be applied for high-power and high-reliability applications. The key of the proposed method is to design two decoupled groups of voltage vector candidates for synthesis on α − β subspace and x − y subspace, respectively. The two decoupled groups of voltage vectors will synthesize respective voltage references on α − β subspace and x − y subspace, while having no impact on each other. The redundant small voltage vectors and zero-sequence voltage vectors are utilized to mitigate voltage oscillation in midpoint of dc link and suppress zero-sequence current component for dual three-phase windings with a common neutral. For comparison, another VSD-SVM strategy is designed based on traditional solution, which cannot offer closed-loop control on x − y subspace. Both simulation and experiments have been given to verify that the proposed decoupled VSD-SVM can suppress harmonic components on x − y subspace besides tracking torque components on α − β subspace. Furthermore, the harmonic performance of the proposed decoupled VSD-SVM has been compared with the traditional VSD-SVM strategy and the carrier disposition based pulsewidth modulation. [ABSTRACT FROM AUTHOR]

Although high-frequency circulating current exists in parallel-operated inverters, it has not attracted as much attention as low-frequency circulating current, and thus has not been analyzed in detail previously. In this paper, a mathematical model and analysis are presented, which reveal the spectrum components and their changing trends of the circulating currents caused by carrier phase differences. The impact of carrier phase difference on high-frequency circulating current is also analyzed and verified. A closed-loop control scheme is proposed to suppress the switching frequency circulating current caused by carrier phase difference. In addition, the deadbeat and closed-loop control are combined to suppress the low- and high-frequency circulating currents simultaneously, to improve the overall performance of circulating current suppression. The effectiveness of the proposed scheme is verified by the simulation and experimental results acquired from a laboratory platform. [ABSTRACT FROM AUTHOR]

Integration of decoupling capacitors into silicon carbide (SiC) metal oxide semiconductor field effect transistor (mosfet) modules is an advanced solution to mitigate the effect of parasitic inductance induced by module assembly interconnects. In this paper, the switching transient behavior is reported for a 1.2-kV SiC mosfet module with embedded dc-link capacitors. It shows faster switching transition and less overshoot voltage compared to a module using an identical package but without capacitors. Active power cycling and passive temperature cycling are carried out for package reliability characterization and comparisons are made with commercial Si and SiC power modules. Scanning acoustic microscopy images and thermal structure functions are presented to quantify the effects of package degradation. The results demonstrate that the SiC modules with embedded capacitors have similar reliability performance to commercial modules and that the reliability is not adversely affected by the presence of the decoupling capacitors. [ABSTRACT FROM AUTHOR]

The five-level nested neutral-point-clamped (5L-NNPC) converter is one of the most promising topologies for medium-voltage (2.3–7.2 kV) high-power applications such as medium-voltage drives, wind energy conversion systems, and grid-connected systems. The 5L-NNPC requires a fewer number of switching devices, freewheeling and clamping diodes, and flying capacitors compared to the existing five-level multilevel converters. In the 5L-NNPC topology, each flying capacitor voltage is regulated at one-fourth of the dc-bus voltage to obtain the five-level operation. Due to the lack of redundant switching states, it is difficult to control the flying capacitor voltages by using the pulse-width-modulation-based classical control methods. This paper proposes a model-predictive current control (MPCC) approach to control the flying capacitor voltages along with the output currents of the 5L-NNPC converter. The discrete-time model of 5L-NNPC is developed to implement the MPCC scheme. The simulation and experimental studies are conducted to verify the dynamic and steady-state performance of 5L-NNPC with the MPCC scheme. The performance of the proposed MPCC approach is compared with the conventional space-vector-modulation-based voltage-balancing approach. Furthermore, the flying capacitor voltage control capability of MPCC is verified at different load power factors. [ABSTRACT FROM AUTHOR]

This paper presents a delta-sigma modulation control scheme for buck converters that features a reconfigurable loop filter with a scalable sampling frequency for effective switching noise reduction and high conversion efficiency. Depending on the load current, the proposed controller changes the sampling frequency along with the delta-sigma modulator (DSM) structure to transform between third- and second-order loop filters. Thus, it maintains a robust noise shaping capability and reduces the power consumption over a wide load range. The loop filters are implemented with a single op-amp resonator to reduce multiple integrators into a single element and enhance controllability of the resonance. More power-efficient operation is obtained by a switching node assisted deadtime controller (SADTC) that regulates the body-diode conduction. The proposed DSM-based buck converter was fabricated on a 180 nm CMOS. A spurious-free output spectrum with a noise floor below −81 dBm was achieved across all sampling frequencies. It operated at a wide range sampling frequencies of 3.75–15 MHz and regulated the output in the range of 1.0–2.4 V with input voltages of 2.5–5.5 V. The output voltage ripples were maintained under 19 mV. The converter showed a conversion efficiency of better than 80% over a load range of 1–1000 mA with a peak efficiency of 95.4% at 125 mA. [ABSTRACT FROM AUTHOR]

This paper proposes a control method for a five-level hybrid flying-capacitor (5L-HFC) inverter, of which structure stems from the conventional five-level active neutral-point-clamped (5L-ANPC) topology by dividing the dc-link stage into three series-connected capacitors. In this inverter, the voltage stress on the power switches connected to the dc link is reduced by a half compared with that of the 5L-ANPC topology, thus the lower number of equally voltage-rated power devices can be employed. Also, the power losses in the 5L-HFC inverter are more evenly distributed than in the 5L-ANPC. In order to balance the dc-link capacitor voltages, a third-order harmonic offset injection is applied. When a diode rectifier is used to supply the dc bus voltage, the balancing method is not effective if the modulation index is higher than 0.64. Thus, an auxiliary circuit is needed to support the balancing of the dc-link capacitor voltages. However, the unbalancing problem can be overcome in a full-range operation without the auxiliary circuit if the back-to-back configuration is utilized. Finally, simulation and experiment results have verified the performance of the 5L-HFC inverter with the proposed control method. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the duty ratio variation on the class-EM power amplifier are studied and analyzed, including nonlinear gate-to-drain and drain-to-source parasitic capacitances. The duty ratio is one of the important parameters in class-EM power amplifiers, which has high effects on the switch voltage and current waveforms, output power, efficiency, power loss, and output phase shift. To achieve a better agreement between theoretical and experimental results, the nonlinear gate-to-drain and drain-to-source parasitic capacitances are included in theoretical analysis. To demonstrate the validity of the presented analysis, five class-EM power amplifiers are designed, simulated, fabricated, and tested using IRF510 mosfet with the duty ratio equal to 0.5, 0.6, and 0.7 and IRFZ24N mosfet with the duty ratio equal to 0.5 with and without considering mosfet nonlinear capacitances. It is shown that the amplifier with IRFZ24N mosfet has higher efficiency than that with IRF510 mosfet. This is because of the lower drain-to-source on-state resistance of the IRFZ24N mosfet. The obtained efficiency with IRFZ24N mosfet considering nonlinear capacitances at the operating frequency of 3.5 MHz was 95.7%. The obtained output power for IRF510 and IRFZ24N mosfets at the duty ratio equal to 0.5 was 14.41 and 17.82 W, respectively. Simulation and theoretical results are performed using PSpice and MATLAB, respectively. The theoretical results and PSpice simulations agreed with experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes the new clamping angle control (CAC) pulse width modulation (PWM) method to restore its maximum linear modulation range of voltage source inverters (VSIs) reduced by the duty ratio limitation in hardware implementation, which makes the VSIs to operate nonlinearly in the high modulation range. The deadtime and the bootstrap gate driver circuit mainly cause this duty ratio limitation in practice. In particular, the bootstrap gate driver circuit is used in many industrial applications by avoiding the additional power supply to apply the gate-source voltage of power switches, and therefore making the VSIs to be small size with the low cost. First, the proposed CACPWM method is theoretically analyzed. Then, it is applied in the high modulation range to overcome the limitation of the duty ratio due to the use of the bootstrap gate driver circuit. Thereafter, its practical effectiveness is verified by both simulation and experimental tests. Also, the resulting harmonic distortions are compared with those by the conventional PWM methods. [ABSTRACT FROM AUTHOR]

This paper presents an overview of resonant and hybrid switched-capacitor converters with a particular focus on multimode operation. The multimode approach is discussed as a tool to affect high efficiency and power density across a wide load range, provide variable regulation, and, as a general framework, to conceptualize the advantages and opportunities of the approach compared to more traditional dc–dc converters. A general analysis is provided to quantify the advantage of hybrid and resonant converters that factors in the tradeoffs between size and loss in the magnetic component and voltage stress on the active devices. A broader set of operating modes is presented that spans continuous and discontinuous conduction and includes resonant, quasi-resonant, and more traditional buck- or boost-like operation. A prototype flying-capacitor multilevel converter is presented to demonstrate the variety of operating modes and motivate important considerations such as voltage balance on the flying capacitors. [ABSTRACT FROM AUTHOR]

The trend toward higher switching frequencies and higher power densities in dc–dc conversion led the designers to rediscover resonant topologies. However, the analysis of these converters is often limited to a particular operating mode and/or topology. This paper wants to fill the gap by presenting a state-space-based analysis for a broad class of series-resonant converters including voltage-fed as well as current-fed topologies, either unidirectional or bidirectional. The proposed solution consists of a mathematical framework that solves the trajectory of state variables in the resonant tank, as well as the main characteristic functions such as voltage conversion ratio and transferred power. The matrix approach permits a flexible and compact formulation and easy implementation in computational tools such as MATLAB. The theoretical framework is applied to both voltage-fed and current-fed resonant topologies: the first is used to show the advantages of the proposed model respect to the first harmonic approximation, while a detailed analysis in terms of operating mode boundaries, delivered power, and voltage gain is provided for the second. Simulations and measurements on a 300-W prototype of the current-fed topology are used to validate the correctness of the proposed solution. [ABSTRACT FROM AUTHOR]

The output voltage of matrix converter (MC) is related to the frequency of input, output, and carrier signals, and these three frequencies are independent of each other. This makes it difficult to give a precise description of the harmonic spectrum with the commonly used methods such as fast Fourier transform (FFT) and the double Fourier analysis. Based on triple Fourier series, this paper proposes an analytical method to determine harmonic components of MC under space vector modulation (SVM). First, combined with the SVM strategy of MC, the expressions of output voltage harmonics are derived. Then the analytical solutions are obtained on the basis of the calculated expressions. From the analytical solutions, the harmonic amplitudes can be determined precisely, and the values of index variables k , p, and q of harmonic frequency ${kf}_{\rm c} \;\pm\; pf_{{\rm{out}}}\pm qf_{{\rm{in}}}$ are confirmed. According to the results, the harmonic distribution characteristics as well as main harmonic components are analyzed. Finally, the feasibility and accuracy of the proposed analysis method is verified by comparative analysis against the FFT results of measured output voltage waveform. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic power flow management system for a solar photovoltaic (PV) system employing a single-stage single-inductor-based dual-input/output dc–dc converter feeding standalone dc loads backed up by a rechargeable battery. A time-sharing voltage-mode control scheme has been proposed for power flow management between solar PV, a battery, and a standalone dc load, and it also maintains a constant dc load voltage and performs maximum power point tracking operation of solar PV. The implementation of the control scheme has been described in detail. The steady-state performance of the single-stage converter has been explained with the relevant analytical expressions derived along with the characteristics. A state-space average model was developed for simulating the transient behavior and validating the working of the system for step changes in the input solar PV power and the dc loads. A hardware prototype of the proposed system has been fabricated, and the proposed controller has been implemented using the dSPACE DS1103 real-time interface board. The working of the proposed scheme for different levels of input solar insolation and dc load power demand has been satisfactorily demonstrated, and the corresponding results are also provided. [ABSTRACT FROM AUTHOR]

Parallel inverters are commonly adopted in high-power applications, for instance wind energy systems, smart transformers, and power conditioners. Meanwhile, interleaved pulse width modulation is usually considered as an optimal approach to reduce the current ripple and harmonics of the parallel inverters. However, in the case of a common dc link, the problem of circulating current emerges and leads to performance degradation. This paper aims at investigating the influence of different modulation techniques on the circulating current of two neutral-point-clamped (NPC) inverters under interleaved operation. Two modulation techniques, phase disposition (PD) and alternative phase opposite disposition (APOD), have been studied and compared in terms of current ripple, spectrum quality, and circulating current. Though the PD modulation was regarded as the optimum solution in most of the single-NPC cases, it offers worse performance in the two parallel NPC applications due to higher circulating current. Simulation and experimental validations are provided and show that the APOD leads to much lower circulating current and similar current ripple as well as spectrum quality compared to the PD. [ABSTRACT FROM AUTHOR]

With the development of silicon carbide (SiC) power devices, the circuit structure of power converter for high-voltage applications would be simpler and more compact because the two-level-based topologies become applicable. This paper proposes a full-bridge (FB) T-type isolated dc/dc converter for the applications with high input voltage and wide input voltage range. The proposed converter is composed of four main power switches with high voltage stress (SiC mosfet) and four auxiliary power switches with low voltage stress (Si mosfet). Comparing with the conventional diode clamped FB three-level isolated dc/dc converters, the proposed FB T-type converter has simpler circuit structure and higher efficiency. A corresponding control strategy including two working patterns is proposed, which can not only realize the zero-voltage switching for the main and auxiliary power switches but also satisfy the wide input voltage range. More importantly, the proposed corresponding control strategy has the ability of balancing the currents among the power switches, which would balance the power losses, thermal stresses among the power switches, and thus improve the reliability of the converter. The characteristics and performances of the proposed converter with the corresponding control strategy are analyzed in detail and verified by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a novel buck–boost dc–dc converter with continuous input current is proposed. The voltage gain of the presented converter is higher than conventional converters, such as buck–boost, single-ended primary-inductance converter, Cuk, and Zeta converters. This converter works only by one switch and voltage stress across the switch is low. Input current of the proposed converter is continuous so a large filter at the input is not needed. Furthermore, continuous input current has made this converter suitable for renewable energy and fuel cell applications. In this converter, noninverting output voltage is obtained and high gain of voltage is achieved as well. So it can operate at wide output voltage range only by changing the duty cycle of the power switch pulse. The presented converter can easily controlled in continuous conduction mode operation, because of using only one power switch. In the following, the principle of operation and the mathematical analyses of the proposed converter are explained, finally, validity of the proposed dc–dc converter is verified by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a half-bridge (HB) converter, additionally employing a diode compared with the conventional modified duty-cycle-shifted (MDCS) HB converter, is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Since the proposed converter has symmetrical operation, it maintains the advantages such as no transformer dc-offset current, and identical and low-voltage stresses on the secondary diodes. Moreover, due to one additional switch connected in series, the zero-voltage-switching capability of the upper switch is improved. As a result, small resonant inductances are required, which reduces the duty cycle loss, thus the primary conduction losses decrease. In addition, since additional clamping diodes separate external resonant inductor from the resonance path, additional voltage stresses on the secondary diodes can be decreased. Therefore, its snubber loss can be reduced, and it can achieve higher efficiency than that of the MDCS HB converter. To confirm the operation, features, and validity of the proposed converter, a 310–400 V input and 50-V/250-W output laboratory prototype is built and tested. [ABSTRACT FROM AUTHOR]

This paper presents an improved compact model for a discrete silicon-carbide (SiC) MOSFET. This compact model based on the previous model features a new behavioral model of output characteristics and new nonlinear models of internal capacitors. Simulation with the improved compact model is in better agreement with measurement than that with the previous compact model, as well as transient behavior of the drain–source voltage, the drain current, and the leakage current out of a heatsink. Furthermore, the improved model is useful for constructing the accurate compact model that can reproduce the high-frequency characteristics of the transient waveforms of SiC-MOSFET s. This successful validation indicates that the improved compact model would be a promising tool for a full-simulation-based design system of the power converters using SiC-MOSFETs. [ABSTRACT FROM AUTHOR]

To develop thermoelectric power conditioning systems that are highly efficient over a wide range of input voltages and support medium-rated power, this paper introduces a hybrid resonant dc/dc converter using an active voltage-doubler rectifier. When the input voltage is higher than the preset nominal input voltage, the converter operates in the phase-shift full-bridge series-resonant converter mode, in which it achieves high efficiency by softly switching the primary-side switches and reducing the conduction loss. When the input voltage is lower than the nominal one, it operates in the resonant boost mode that boosts the resonant inductor current. By using the active voltage-doubler rectifier on the secondary side of the converter, we can build the converter with less number of active components. As a result, the proposed converter achieves, at low cost, high boost-ratio and high efficiency over a wide range of input voltages. A detailed analysis of the converter operation is presented along with the design procedure. At 35–55 V, a 600-W/360-V prototype of the proposed converter has been built and tested to demonstrate its effectiveness. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) for battery charging applications has significant advantages over the traditional plug-in system. Since misalignment between the primary and secondary windings is inevitable, it is of significance to improve the misalignment tolerance of IPT systems with constant-current (CC) and constant-voltage (CV) outputs for battery charging. In this paper, the load-independent output characteristic of the hybrid topology and the function switching between CC and CV of the reconfigurable topology are analyzed. Besides, a hybrid and reconfigurable IPT system with 3-D misalignment tolerance for CC and CV outputs is proposed, simplifying or even canceling control schemes. Moreover, a novel parametric design method is given for the IPT system, which can suppress the fluctuation of the output voltage/current within a certain range of misalignment. In order to validate the performance of the proposed topology, a 1-kW prototype is built, and the corresponding experiments are carried out. In the CC/CV mode, the system can operate with the longitudinal misalignment to 50% when the load varies from 36 to 480 Ω, and the fluctuation of the output current/voltage is within 5%. Similarly, the misalignment in Y- and Z-axis is 12.5% and 33.3%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a novel three-phase DC-link multilevel inverter topology with reduced number of input DC power supplies. The proposed inverter consists of series-connected half-bridge modules to generate the multilevel waveform and a simple H-bridge module, acting as a polarity generator. The inverter output voltage is transferred to the load through a three-phase transformer, which facilitates a galvanic isolation between the inverter and the load. The proposed topology features many advantages when compared with the conventional multilevel inverters proposed in the literatures. These features include scalability, simple control, reduced number of DC voltage sources, and less devices count. A simple sinusoidal pulse-width modulation technique is employed to control the proposed inverter. The performance of the inverter is evaluated under different loading conditions and a comparison with some existing topologies is also presented. The feasibility and effectiveness of the proposed inverter are confirmed through simulation and experimental studies using a scaled down low-voltage laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper presents a new predictive power-factor-correction (PFC) controller for series-interleaved three-level boost (TLB) converters. Compared to the state-of-the-art TLB PFC controllers, where a two-cycle prediction and a detection of an operating region are necessary, the proposed controller achieves a low total harmonic distortion of the input current by using a single equation to predict the input current in all operating regions of the converter, in just one operating cycle. The average current control is achieved by sampling at the peak of the triangular carrier. The proposed PFC controller significantly reduces the distortion of the input ac current near the zero-crossing points, resulting in a low total harmonic distortion of the input current. The operation of the proposed controller was evaluated, and its stability and robustness to parameter changes was confirmed analytically. The controller operating principles were verified in simulations and validated by experiments on a medium-voltage 50-kW converter prototype. [ABSTRACT FROM AUTHOR]

The neutral-point potential fluctuation in single-phase three-level rectifiers leads to coupling between the line current regulation and dc-link capacitor voltage balancing, deteriorating waveform quality of the line current. For addressing this issue, this paper proposes a low-complexity model predictive current control (MPCC) with constant switching frequency, which achieves a decoupling control of the line current and the neutral-point potential under the unbalanced load condition. The switching frequency is fixed by combining the MPCC scheme with predefined switching sequences. The boundary of the durations for voltage vectors in switching sequences is presented to balance the capacitor voltage without worsening the line current quality. The optimal switching sequence and the corresponding optimal durations of voltage vectors in the switching sequence are readily derived without the assessment of the cost function, which dramatically simplifies the complexity of the MPCC scheme. Finally, simulations and experimental results are conducted to verify the effectiveness of the proposed MPCC scheme. [ABSTRACT FROM AUTHOR]

A family of dimmable ac light-emitting-diode (LED) drivers fed from dc voltages, is presented in this paper based on zero-current-switching quasi-resonant converters. The proposed family of drivers is based on replacing the diode in the conventional converter topologies (i.e., buck, boost, or buck–boost) by a string of high-brightness LEDs (HB-LEDs). Hence, the HB-LED string will be working as the rectifier diode and the load, switching at the same frequency of the main switch. In this case, the output current, which is experimentally validated, shows a negative current peak due to the reverse-recovery effect of the HB-LEDs. In order to reduce the reverse-recovery effect on the HB-LEDs, the main switch of the proposed topologies is replaced with a full-wave resonant switch, which makes possible to reduce the di/dt during the turn-off of the HB-LED string, therefore the reverse-recovery effect is eliminated. Moreover, the dimming of the HB-LEDs is done by means of changing the switching frequency of the converter by varying the turn-off, while keeping a constant turn-on time. The proposed converters are suggested to be used in a postregulator stage of an ac–dc converter or as the interface between the low-voltage bus and the HB-LED string in a dc nanogrid. In order to validate the analysis, the proposed topologies have been experimentally tested on a constructed prototype with an output power of 7.5 W, that is able to achieve an electrical efficiency of 94.5% and a luminous efficacy of 110 lm/W at full load. Moreover, the analysis has been extended to a comparison in terms of reliability with the conventional topologies on a 700-h test. [ABSTRACT FROM AUTHOR]

High-frequency (HF) switching and ac-side unbalanced loads challenge smart transformer (ST)-fed hybrid grids (both ac and dc), causing common-mode (CM) voltage variations and dc-link oscillation. The HF switching introduces an HF CM voltage and the ac grid unbalanced loads introduce a fundamental frequency CM voltage in hybrid grids. The CM voltage in ST-fed distributed grids degrades the power quality, threatens the safety of the connected devices, and potentially constitutes a health risk for the operators of such devices. Therefore, this paper systematically analyzes the root causes of the ST CM voltage variations and the impacts on hybrid grids. Based on the two typical configurations (three- and four-leg converters), the performance and requirements of CM inductor filter and bypass CM filter on HF CM voltage suppression are studied in detail. By considering the CM voltage suppression and dc capacitor lifetime, a four-leg converter with improved modulation strategy and small dc bypass film capacitor is proposed. The simulation and experimental results clearly verify the feasibility and correctness of the proposed strategies. [ABSTRACT FROM AUTHOR]

Owing to low cost, small size, and low weight, transformerless inverters became prominent in single-phase grid connected photovoltaic (PV) systems. Key issues pertaining to these inverters include suppression of common mode (CM) leakage current and improvement of conversion efficiency. Achieving higher efficiency in single-phase grid-connected photovoltaic systems depends on the number of stages involved in feeding power to the grid, predominantly, if the PV array voltage is less than the peak value of the grid voltage. In this paper, an integrated dc–dc converter based grid-connected transformerless PV inverter is proposed which is aimed at maintaining high efficiency, even if the PV array voltage falls below the peak value of grid voltage (efficient operation at an extended input voltage range). A modulation strategy is discussed in order to minimize the flow of CM leakage current. Further, the efficiencies of certain transformerless inverter topologies are analyzed and compared with that of the proposed topology. Detailed simulation studies are carried out in MATLAB/Simulink environment to verify the analysis. Experimental results for a scaled down laboratory prototype are included as a proof-of-concept to validate the claims. [ABSTRACT FROM AUTHOR]

In this paper, a modular control approach has been proposed for a single- and three-phase differential-mode Ćuk inverter (DMCI) operating with a recently proposed discontinuous-modulation scheme that offers tangible performance benefits over conventional continuous modulation scheme. The modular control scheme uses a combination of a transformation and adaptive control law to meet tracking requirements in the presence of converter nonlinearity. Experimental results for the single- and three-phase DMCI are provided for startup, steady state, load transition, and total harmonic distortion using different types of loads, which validate the efficacy of the implemented modular tracking controller. Further, detailed stability of the closed-loop DMCI module is provided. [ABSTRACT FROM AUTHOR]

This paper has focused on the novel space vector pulse-width modulation (SVPWM) strategy for the two-level three-phase inverter, which could eliminate the harmonics nearby pulse width modulation (PWM) frequency. Ear-piercing high-frequency electromagnetic noise from motor is common due to PWM technique. The proposed SVPWM is able to remove the high-frequency harmonics located nearby the PWM frequency and other odd multiples by changing the original switching states. The unpleasant acoustic noise could be removed with the novel strategy whose PWM frequency is selected near 10 kHz. By comparison, it is near 20 kHz for conventional SVPWM to achieve the similar performance. Therefore, the switching losses are significantly reduced using the novel method. Furthermore, the proposed technique neither changes the characteristics of the fundamental wave nor employs the additional circuits in the drive. At last, the effectiveness of proposed strategy is verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This paper presents a control method that can prevent audible noise generation in an LLC resonant half-bridge dc–dc converter under a light-load condition, while achieving the same input voltage range and power-conversion efficiency ηe as the burst-control method that generates an audible noise. The proposed method reduces switching and conduction losses at light load by skipping several pairs of switch-control pulses, while varying the switching frequency less than the normal-control method does. This skip-control method enables the LLC resonant converter to have a large magnetizing inductance, and to have high ηe over a wide range of load variation. At an input voltage of 385 V, an output voltage of 24 V, and a resonant frequency of 180 kHz, the proposed method achieved η e ≥ 85.46% for an output power range of 7.2–360 W; the highest ηe was 96.08% at $P_o$ = 336 W. [ABSTRACT FROM AUTHOR]

The powder-core-based inductor has a wide inductance variation due to the soft-saturation nature when subjected to varying load current. Under such a condition, the current ripple is influenced, and the conventional inductor design principle may be inaccurate. Besides, the voltage of the inductor is distorted. Also, the bandwidth of the controller is hard to determine. In this paper, the current ripple under the condition of wide inductance variation is analyzed, and its change rule is revealed; then, a new inductance design principle is proposed. The harmonic components for the three-phase converter with the powder core inductor are investigated, and the harmonic characteristic of the input current is analyzed. According to the current harmonic characteristic, the resonance controllers are introduced to eliminate harmonics, and the quality of the current is improved. Besides, the bandwidth of the controller is found to vary with the output power. Then, a compensation method is proposed to eliminate the influence of inductance variation on the bandwidth. The experimental results verify the analysis. [ABSTRACT FROM AUTHOR]

A family of high-voltage-gain dc–dc converters derived from a generalized structure with two stages is introduced in this paper. On the input side, a two-phase interleaved boost stage boosts the dc input voltage to output a modified square-wave voltage that feeds the second stage. This output of the interleaved boost stage is rectified and further boosted using a voltage multiplier stage. As a result, a high voltage gain is achieved using the proposed converters. The two-phase interleaved boost stage on the input side makes it possible for the converters to be operated using a single source or two independent sources. If a single source is used, the input current drawn is continuous with a very small ripple. Owing to its generalized structure, the proposed family of converters includes both nonisolated and isolated converters with high voltage gains. The high voltage gain and low-ripple continuous input current make these converters appealing in applications like the integration of renewable sources such as solar, fuel cells, etc., on to a 400-V dc bus. [ABSTRACT FROM AUTHOR]

Electrical and electromagnetic methods have long played an important role in mineral exploration. For example, in active source prospecting methods, when measuring the values of many electrical parameters, the signal-to-noise ratio can be improved by increasing the transmitting power. In this paper, we present a multifunction borehole ground electromagnetic transmitting system that transmits rectangular waves at a frequency of 0.01–10 kHz with a frequency error less than 10−8 Hz @ 1 Hz (depending on the high-precision temperature compensation crystal) and the initial synchronization error between the transmitter and receiver is less than $ \pm \text{0.1}\,\mu {\text{s}}$. During operation, either the maximum transmitting voltage output can reach 950 V or the maximum transmitting current can exceed 90 A, but both cannot be achieved simultaneously. We tested the transmitting system at its maximum power output continuously for over 8 h and the power output was more than 48 kW at a current above 60 A. The energy was delivered above ground or underground using existing drill casings to produce the high-power transmissions. The field experiments show that the system meets the demands of the controlled-source audio-frequency magnetotelluric and induced polarization methods used in mineral exploration. [ABSTRACT FROM AUTHOR]

This paper proposes a novel modified LLC converter with two split resonant branches for wide input-range applications. It can operate in low-gain (LG) mode or medium-gain (MG) mode. The voltage gain of MG mode is 1.5 times that of LG mode, while they have same range of voltage gain $M_{{\rm{tank\_range}}}$ , i.e., the ratio of maximum voltage gain to minimum one. Therefore, the input voltage can be regulated in a wide range by operating the converter in different modes. To achieve the transition between modes, the required $M_{{\rm{tank\_range}}}$ of the proposed converter is as low as 1.5, resulting in lower magnetizing current and higher efficiency within the entire operation range. Smooth transition can be achieved by adjusting the duty cycles of switches gradually. The proposed LLC converter with primary dual-bridge is analyzed in detail as an example. To verify the theoretical analysis and performance of proposed solution, a 1-kW 400-V output prototype with input voltage ranging from 80 to 200 V is built, tested, and compared with two existing full-bridge LLC converters. Analysis and experimental results indicate that smaller volume of transformers, reduced rectifying diodes, and higher overall efficiency are achieved with the proposed converter. [ABSTRACT FROM AUTHOR]

This paper presents a model-based method to diagnose single- and multiple-transistor open-circuit (OC) faults in grid-tied three-phase voltage-source inverters (VSIs). The method is based on calculated average bridge arm pole-to-pole (PTP) voltages and error-adaptive thresholds. Only existing signals for closed-loop control are needed; thus, this method can be easily embedded in the system without extra sampling and circuits. Average PTP voltage deviations are chosen as diagnosis variables, which show considerable distinction quickly after fault. Consequently, fast fault diagnosis speed can be achieved. The fault diagnosis time for single fault can be as short as two switching periods. Besides, diagnosis variables show the same faulty characteristics in inverter mode and rectifier mode; thus, this method is effective in both modes. Moreover, for the first time, the variation of inductance caused by conducted current is considered to obtain a more accurate variable-inductance model, and the thresholds are updated according to mathematically estimated diagnosis variable calculation errors from sampling error, inductance error, dead time, and delay time, which maintains high robustness as well as fast speed. Finally, the effectiveness of the proposed method is validated with experiments. [ABSTRACT FROM AUTHOR]

In this paper, a new single-stage half-bridge (HB) resonant $LLC$ converter additionally employing one resonant capacitor and two relays with one package is proposed, compared with a single-stage HB $LLC$ converter. Moreover, a center-tapped transformer is replaced with a coupled transformer. Since the proposed converter changes the turns ratio of the coupled transformer using a relay according to low- or high-input-voltage range, it can decrease the range of its needed voltage gain. It means that the proposed converter can be designed with large transformer magnetizing inductance compared with the conventional single-stage HB $LLC$ converter. As a result, the primary conduction and turn-off losses are reduced. Moreover, in low input voltage range, it has smaller total primary wire resistance of the transformer due to parallel connection of the coupled transformer, which decreases its conduction loss. In addition, additionally employed small-sized components can be inserted to the conventional system. To confirm the operation, features, and validity of the proposed converter, universal input with low line and high line and 16.5 V/60 W output laboratory prototype targeting laptop adapters with wide-input-voltage range is built and tested. [ABSTRACT FROM AUTHOR]

In this paper, a current-mode Class-DE (CMCDE) power amplifier is presented. The CMCDE with linear shunt capacitance under zero-current switching (ZCS) and zero current-derivative switching (ZCDS) conditions at any active time is analyzed, simulated, and fabricated. An analytical theory along with the design simulation and verification by experimental results at active time \tau d= \pi / 2 are given. It was shown that the peak switch voltage can be adjusted with active time \tau d. The proposed amplifier offers several desirable features, such as simple structure and possibility to include the parasitic inductance and shunt capacitance of the mosfet into a load network, so that ZCS condition is maintained. The results show that the switch voltage and current obtained in CMCDE amplifier are inversed in comparison to the voltage-mode Class-DE (VMCDE) amplifier by using a simple output matching network and series inductance. Also, we could control the harmonics in one resonator in comparison to multiple resonators used in some high-efficiency power amplifiers. The measured maximum drain efficiency of 88% and power gain of 22 dB at 42-dBm output power was obtained at 4 MHz for CMCDE amplifier at active time \tau d= \pi / 2. [ABSTRACT FROM AUTHOR]

This paper proposes a circuit structure that can improve the power-conversion efficiency \eta e of an AC–DC boost converter. The circuit uses a 1:1 transformer and a voltage boost circuit composed of an inductor, a capacitor, and a diode. The transformer forces the converter to operate in continuous conduction mode for input current, and thereby reduces input ripple. The voltage boost circuit enables the switch to operate in critical conduction mode, so the power loss due to turn-on of switch and reverse recovery of diode is minimized. The proposed converter has high \eta e over a wide range of AC input voltage $V_{{\rm{ac}}}:\,\eta _{e}= 92.9\% $ at $V_{{\rm{ac}}}= {\text{85}}\,{\text{V}} and \eta e= 97.4\% at V{\rm{ac}}= {\text{265}}\,{\text{V}}, when the converter was operated at DC output voltage of 400 V and output power of 500 W. The temperature of the switch stabilized at ∼84 °C for $V_{{\rm{ac}}}= {\text{85}}\,{\text{V}}$ , at ∼70 °C for $V_{{\rm{ac}}}= {\text{110}}\,{\text{V}}$, and at ∼42 °C for $V_{{\rm{ac}}}= {\text{220}}\,{\text{V}}$, whereas that in other AC–DC converters either failed or stabilized at much higher levels. The proposed converter is well suited to systems that require an input voltage range of 85–265 V in root-mean-square value. [ABSTRACT FROM AUTHOR]

This paper presents the active capacitor voltage-balancing (ACVB) methods based on the dynamic model for a five-level nested neutral-point piloted (NNPP) converter using hybrid carrier modulation. The traditional hybrid carrier modulation provides natural voltage balancing of floating capacitors and dc-link capacitors. First, the natural voltage-balancing ability under steady-state and ideal conditions is theoretically proved. However, there are accumulated errors and deviations of capacitor voltages in practical applications, especially under dynamic conditions. In order to address the accumulated errors and deviations of capacitor voltages, the dynamic models of floating-capacitor voltages and neutral-point voltage are established. Moreover, the ACVB method based on the dynamic model of the neutral-point voltage is proposed by injecting the zero-sequence voltage. And the ACVB method based on the dynamic model of floating-capacitor voltages is proposed by introducing the adjustment variables. The proposed ACVB methods have the advantages of simple formula, definite physical meaning, and high accuracy. Furthermore, the output voltage quality and current quality are evaluated in term of total harmonic distortion and the effect of model parameter mismatch on the proposed ACVB methods is presented. Finally, the comparative simulation and experimental results verify the correctness of the proposed ACVB methods based on the dynamic model under different conditions. [ABSTRACT FROM AUTHOR]

In this paper, a novel platform for the single phase switched-capacitor multilevel inverters (SCMLIs) is presented. It has several advantages over the classical topologies, such as an appropriate boosting property, higher efficiency, lower number of required dc voltage sources, and other accompanying components with less complexity and lower cost. The basic structure of the proposed converter is capable of making nine-level of the output voltage under different kinds of loading conditions. Hereby, by using the same two capacitors paralleled to a single dc source, a switched-capacitor (SC) cell is made that contributes to boosting the value of the input voltage. In this case, the balanced voltage of the capacitors can be precisely provided on the basis of the series–parallel technique and the redundant switching states. Afterward, to reach the higher number of output voltage levels, two suggested SC cells are connected to each other with a new extended configuration. Therefore, by the use of a reasonable number of required power electronic devices, and also by utilizing only two isolated dc voltage sources, which their magnitudes can be designed based on either symmetric or asymmetric types, a 17- and 49-level of the output voltage are obtained. Based on the proposed extended configuration, a new generalized version of SCMLIs is also derived. To confirm the precise performance of the proposed topologies, apart from the theoretical analysis and a complete comparison, several simulation and experimental results are also given. [ABSTRACT FROM AUTHOR]

This paper proposes a practical solution of high-frequency-link dc transformer based on switched capacitor (SCDCT) for medium-voltage dc (MVDC) power distribution application. Compared to the traditional dc transformer scheme, the proposed SCDCT can disconnect from MVDC distribution grid effectively as a dc breaker when a short fault occurs in the distribution, can enhance power transfer capacity, and always ensures high-frequency-link voltage match to improve current impact and efficiency performances, and the redundancy design can be achieved when some submodules fail to improve the reliability. In the paper, the topology, voltage and power characterization, control strategy, startup, and fault solution of SCDCT are presented and analyzed comprehensively. At last, an SCDCT prototype is built and the experimental results verify the correctness and effectively of the proposed solution. [ABSTRACT FROM AUTHOR]

This paper presents a new application of power and voltage balance control schemes for the cascaded H-bridge multilevel inverter (CHMI)-based solid-state transformer (SST) topology. To reduce load on the controller and simplify modulation algorithm, a master–slave control (MSC) strategy is designed for the dual active bridge (DAB) stage. The master controller executes all control and modulation calculations, and the slave controllers manage only device switching and protection. Due to the inherent power and dc-link voltage unbalance in cascaded H-bridge-based SST, this paper presents a compensation strategy based on three-phase dq decoupled current controller. An optimum zero-sequence component is injected in the modulation scheme so that the three-phase grid currents are balanced. Furthermore, to tightly regulate the output voltage of all the DAB modules to target value, a dynamic reference voltage method is also implemented. With this proposed control method, the three-phase grid currents and dc-link voltage in each module can be simultaneously balanced. Finally, simulation and experimental results are presented to validate the performance of the controller and its application to microgrid SST. [ABSTRACT FROM PUBLISHER]

A virtual space vector modulation technique reducing both magnitude and third-order harmonic component of the common-mode voltage (CMV) in a two-level voltage-source inverter (VSI) is proposed in this paper. The presented method employs a set of virtual space vectors constructed from original stationary space vectors to conduct modulation. Since the created virtual vectors have the lowest instantaneous and zero average CMVs, both the magnitude and third-order harmonic component of the generated CMV are reduced, contributing to better overall CMV performance and common-mode filter design in VSI applications. Three variants of the proposed modulation method using different virtual space vector combinations are presented. The concept of the virtual space vector modulation technique demonstrated with two-level inverter in this paper can also be extended to multilevel inverters. Simulation and experimental results, as well as comparisons with existing methods are provided to verify the proposed technique. [ABSTRACT FROM AUTHOR]

In this paper, we introduced an improved transformer-based parallel-resonant converter, suitable for high voltage, high power dc loads. The resonant capacitors are connected in parallel with diodes of the high voltage rectifier, thus restraining dv/dt stress in high voltage circuits. The LC tank resonant frequency is well beyond the switching frequency, reducing in this way the VA rating of LC components. With rated load, the output current of the IGBT bridge is equal to zero at switching instants, and the switching losses are very low. Proposed subresonant circuit requires lower primary current for the given output power and it has reduced IGBT losses. Experimental setup delivers 79 kW with an efficiency of 96.78%. The paper explains the switching states of the devised topology, and provides the guidelines for designing the power transformer, the LC tank and controls. Analytical prediction of the performance curves is verified both in laboratory and by the field tests with an electrostatic precipitator plant. [ABSTRACT FROM AUTHOR]

Analog circuitry-based photovoltaic (PV) maximum power point (MPP) tracking (MPPT) technique is attractive due to its low cost and capability of easy integration with normal dc–dc switching converters. However, realization of classical digital MPPT algorithms using analog circuitries is a challenging task. It necessarily requires to store the information of module voltage/current and power in order to find the desired MPP. While at the same time, improper design of digital MPPT controllers may cause poor tracking performances or limit cycle oscillations to manifest, which are generally seen as being undesirable. This paper proposes a fast and robust analog PV MPP tracker without imposing any external control or perturbation. The fast dynamic performances with absolute robustness are ensured here by integrating the concepts of Utkin's equivalent sliding mode control law and fast-scale stability analysis of actual switched converter systems. Moreover, the superiority of the proposed MPP tracker (in terms of high-tracking performances) over classical ones, and its impact in series-connected converters configuration are analytically demonstrated through the procedure developed in this paper. Finally, the analytical results have been validated by means of simulations and experiments. [ABSTRACT FROM AUTHOR]

Based on the Z-source inverter, this paper proposed a novel approach to zero-crossing point (ZCP) detections during the shoot-through vectors for sensorless brushless dc motor (BLDCM). The proposed approach separates the ZCP detections from speed adjustment, and makes the shoot-through vector not influence the motor speed-adjustment directly, while the zero-vectors and active-vectors are used exclusively to adjust the speed of BLDCM. With the proposed approach, the sensorless BLDCM can operate in a wide speed range without switching the detection points and the reference levels, and it is unnecessary to change the reference levels according to the PWM technique. The terminal voltages limited by diode can be directly compared with the reference zero level during the shoot-through vectors, so as to reduce the detection error caused by attenuation. Moreover, Z-source inverter not only provides boost voltage for sensorless BLDCM drive system, but also improves the utilization rate of dc source voltage and the safety of the drive system. In addition, this paper analyzed the terminal voltages of the floating phase during each vector. The experimental results verified the correctness of above theories and proved the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Pulse width modulation (PWM) converters generate switching common-mode voltages (CMVs) across the load terminals. These voltages cause common-mode currents, leading to bearing failure in motor loads and electromagnetic interference problems. This paper presents a generalized carrier-based PWM technique for open-end winding motor drives that completely eliminates switching CMV. The proposed method is applicable to both dual two-level voltage source inverter and dual matrix converter-based open-end winding drives. Detailed analysis shows that the carrier-based method requires significantly less computation compared to the corresponding space vector implementation. This paper also outlines the relationship between the two implementations. The carrier-based method is shown to achieve superior performance in terms of resource requirements and execution time when implemented on a field-programmable gate array-based real-time control platform. Simulation and experimental results have been presented to validate the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents nonisolated single-switch high step-up converters with low voltage stress. Based on the conventional flyback converter, one single-switch high step-up converter is derived. The voltage stresses on the switch and diodes are limited by using a clamping diode and voltage doubler structure. Also, to further reduce the voltage stresses of them, another single-switch high step-up converter is proposed simply by using one additional capacitor and rearranging the components. Thus, lower voltage-rated switch and diodes can be used, which results in higher efficiency. The operational principle, analysis and design considerations of each converter are presented in this paper. The validity of this study is confirmed by the experimental results from 24 V input and 250 V/125 W output prototype. [ABSTRACT FROM AUTHOR]

This paper presents a merged-two-stage circuit topology suitable for either wide-range dc input voltage or ac line voltage at low-to-moderate power levels (e.g., up to 30 W). This two-stage topology is based on a soft-charged switched-capacitor preregulator/transformation stage and a high-frequency magnetic regulator stage. Soft charging of the switched capacitor circuit, zero voltage switching of the high-frequency regulator circuit, and time-based indirect current control are used to maintain high efficiency, high power density, and high power factor. The proposed architecture is applied to an LED driver circuit, and two implementations are demonstrated: a wide input voltage range dc-dc converter and a line interfaced ac-dc converter. The dc-dc converter shows 88%-96% efficiency at 30-W power across 25-200-V input voltage range, and the ac-dc converter achieves 88% efficiency with 0.93 power factor at 8.4-W average power. Contributions of this paper include: 1) demonstrating the value of a merged two-stage architecture to provide substantial design benefits in high-input voltage, low-power step down conversion applications, including both wide-range-input dc-dc and line-input ac-dc systems; 2) introduction of a multimode soft-charged SC stage for the merged architecture that enables compression of an 8:1 input voltage range into a 2:1 intermediate range, along with its implementation, loss considerations, and driving methods; and 3) merging of this topology with an resonant transition discontinuous-mode inverted buck stage and pseudocurrent control to enable step-down power conversion (e.g., for LED lighting) operating at greatly increased frequencies and reduced magnetics size than with more conventional approaches. [ABSTRACT FROM AUTHOR]

Many publications have been presented on the modulation and control of the modular multilevel converter, some of which are based on phase-shifted carrier modulation. This paper presents an analysis of how the switching frequency affects the capacitor voltages, circulating currents, and alternating voltages using phase-shifted carrier modulation. It is found that switching frequencies that are integer multiples of the fundamental frequency should be avoided as they can cause the capacitor voltages to diverge. Suitable switching frequencies are derived for which the arm and line quantities will be periodic with symmetric operating conditions in the upper and lower arms. Thus, the practical outcome of this paper is a detailed description of how the switching frequency should be chosen in order to achieve advantageous operating conditions. The theoretical results from the analysis are validated by both simulations and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a new multilevel selective harmonic elimination pulse-width modulation (MSHE-PWM) technique for transformerless static synchronous compensator (STATCOM) system employing cascaded H-bridge inverter (CHI) configuration. The proposed MSHE-PWM method optimizes both the dc-voltage levels and the switching angles, enabling more harmonics to be eliminated without affecting the structure of the inverter circuit. The method provides constant switching angles and linear pattern of dc-voltage levels over the modulation index range. This in turns eliminates the tedious steps required for manipulating the offline calculated switching angles and therefore, easing the implementation of the MSHE-PWM for dynamic systems. Although the method relies on the availability of the variable dc-voltage levels which can be obtained by various topologies, however, the rapid growth and development in the field of power semiconductor devices led to produce high-efficiency dc-dc converters with a relatively high-voltage capacity and for simplicity, a buck dc-dc converter is considered in this paper. Current and voltage closed loop controllers are implemented for both the STATCOM and the buck converter to meet the reactive power demand at different loading conditions. The technique is further compared with an equivalent conventional carrier-based pulse-width modulation to illustrate its enhanced characteristics. The effectiveness and the theoretical analysis of the proposed approach are verified through both simulation and experimental studies. [ABSTRACT FROM AUTHOR]