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In this paper, a new class of bidirectional partial-resonance power converters is presented. The proposed family can be configured to interface single- or multi-port dc, single- or multi-phase ac systems at input-side and/or output-side. The proposed family offers a very modular structure, which can lead to cost reduction from a common designed module. In this converter, which accomplishes power conversion in a single stage, a small inductor placed in series with the input and output switch-bridges forms the link. This small link inductor is responsible for transferring power between different ports of the system. The proposed topologies can operate in buck, boost, and buck–boost modes of operation to step up and/or step down the voltage. In buck–boost mode of operation, the converter is controlled such that the power is entirely transferred through the link inductor; whereas, in buck or boost modes of operation only a fraction of the power is transferred through the link inductor, and the remaining power is directly transferred from input phases to the output phases. Galvanic isolation, which is typically a prominent factor contributing to power density of a converter, can be provided by means of a compact and lightweight single-phase high-frequency transformer added to the link. In comparison with earlier generations of partial-resonance inductive-link power converters, in the proposed converter, the level of link peak current and consequently power-loss, as well as voltage and current stress of switches are dramatically decreased. A very small film capacitor can be placed in parallel with the link inductor to facilitate zero-voltage-switching (ZVS) operation for all the switches/diodes. Apart from increasing the overall efficiency, minimized dv/dt stress and improvement in power density are achieved by adding the link capacitor. The proposed converter employs four-quadrant switches, i.e., bidirectional-conducting bidirectional-blocking switches, and charges the link inductor in both positive and negative directions in each cycle. In view of this, better utilization of the link inductor and lower total harmonic distortion (THD) are offered. Furthermore, two distinct switching algorithms are developed for the proposed family of converters. In this paper, the detailed behavior of the proposed family is investigated analytically, and simulation and experimental results are presented to evaluate the performance and effectiveness of the proposed converter. A low-power proof-of-concept prototype with input voltage of 59 V/161 V, load voltage of 178 V/73.5 V, maximum switching frequency of 4.9 kHz/3.65 kHz at 215 W/450 W in a step-up/step-down operation is considered for the experimental verification. [ABSTRACT FROM AUTHOR]

This paper presents a high-gain modular input-parallel output-series dc-dc converter for photovoltaic integration with medium-voltage dc grids. A new full-bridge zero-current-switching (FB-ZCS) converter proposed in this paper is used as a fundamental building block. Existing FB-ZCS converters utilize transformer leakage inductance and a shunt-connected resonant capacitor for achieving smooth resonant current commutation and ZCS. The shunt-connected capacitor requires dedicated charging interval in every switching cycle and stores full-load-rated resonant energy at all load/input conditions, resulting in significant duty-cycle loss. Moreover, it suffers from energy leakage through transformer winding and requires overrating. All these factors adversely impact the operation range of the converter, which is important for achieving a wide maximum power point tracking range. Novel improvements in the proposed converter include minimization of duty-cycle loss and resonant capacitor leakage and the realization of the current-adaptive resonant energy storage mechanism, without using additional switches or auxiliary circuits. Operation of the proposed converter is presented and validated with simulation and experimental results. [ABSTRACT FROM AUTHOR]

In data center and telecommunication power supplies, the front-end dc–dc stage is required to operate with a wide input voltage range to provide hold-up time when ac input fails. Conventional LLC converter serving as the dc–dc stage is not suitable for this requirement, as the normal operation efficiency (at 400 V input) will be penalized once the converter is designed to achieve high peak gain (wide input voltage range). This paper examined the operation of the LCLC converter and revealed that the LCLC converter could be essentially equivalent to a set of LLC converters with different magnetizing inductors that are automatically adjusted for different input voltages. In nominal 400 V input operation, the LCLC converter behaves like an LLC converter with large magnetizing inductor, thus the resonant current is small. In the hold-up period, when the input voltage reduces, the equivalent magnetizing inductor will reduce together with switching frequency reducing, thus the converter achieves high peak gain. In this paper, a new design methodology is also proposed to achieve optimal utilization of the two resonant capacitors for high power application. To verify the effectiveness of the LCLC converter for hold-up operation, comprehensive analysis has been conducted; a detailed step by step design example based on capacitor voltage stress is introduced; an experimental LCLC prototype optimized at 400 V, with input voltage range of 250–400 V and 12 V/500 W as output has been presented. [ABSTRACT FROM AUTHOR]

A single-stage three-phase ac–ac converter benefiting from a high-frequency alternating link voltage is proposed in this paper. In this converter, a very small film capacitor can transfer the energy from the input to the output, owing to the high-frequency alternating voltage of the link. This eliminates the need for large electrolytic capacitors that are typically used in dc-link ac–ac converters. Moreover, a compact high-frequency transformer at the link can replace the bulky low-frequency transformers, in case isolation is required. These features increase the power density as well as reliability of the proposed converter in comparison with the conventional dc-link converters. The number of required switches in the proposed converter is 12, which is less than the number of switches needed in matrix converters, leading to lower switching and conduction losses. Despite being single-stage, the proposed ac–ac converter is capable of both stepping up and stepping down the voltage and also frequency transformation. This eliminates the need for using cascaded power converters. In this paper, the operation principles of the proposed ac–ac converter are investigated, and variable switching frequency and fixed switching frequency control methods for operating this converter are introduced. The performance of the converter is verified through simulation and experiment. [ABSTRACT FROM AUTHOR]

In this paper, a new structure for a nonisolated boost dc–dc converter is proposed. The proposed converter generates higher voltage gain than some conventional nonisolated boost dc–dc converters. In this paper, the voltage and current equations of the elements and voltage gain in continuous conduction mode and discontinuous conduction mode are extracted. Then, the critical inductance converter is extracted and the current stresses in the switches are calculated. To achieve high voltage gain, a generalized structure based on the proposed structure generates for dc–dc converters. Meanwhile, the root mean square current relations of devices are obtained for an extended structure. Finally, the results of PSCAD/EMTDC software and laboratory prototype are used to reconfirm theoretical concept. [ABSTRACT FROM AUTHOR]

In this paper, a high step-up quasi-Z Source (QZS) dc–dc converter is proposed. This converter uses a hybrid switched-capacitors switched-inductor method in order to achieve high voltage gains. The proposed converter have resolved the voltage gain limitation of the basic QZS dc–dc converter while keeping its main advantages, such as continuous input current and low voltage stress on capacitors. Compared to the basic converter, the duty cycle is not limited, and the voltage stress on the diodes and switch is not increased. In addition to these features, the proposed converter has a flexible structure, and extra stages could be added to it in order to achieve even higher voltage gains without increasing the voltage stress on devices or limiting the duty cycle. The operation principle of the converter and related relationships and waveforms are presented in the paper. Also, a comprehensive comparison between the proposed and other QZS based dc–dc converters is provided which confirms the superiority of the proposed converter. Simulations are done in power systems computer aided design (PSCAD) in order to investigate the maximum power point tracking (MPPT) capability of the converter. In addition, the valid performance and practicality of the converter are studied through the results obtained from the laboratory built prototype. [ABSTRACT FROM AUTHOR]

This paper introduces a non-isolated high step-up dc–dc converter with dual coupled inductors suitable for distributed generation applications. By implementing an input parallel connection, the proposed dc–dc structure inherits shared input current with low ripple, which also requires small capacitive filter at its input. Moreover, this topology can reach high voltage gain by using dual coupled inductors in series connection at the output stage. The proposed converter uses active clamp circuits with a shared clamp capacitor for the main switches. In addition to the active clamp circuit, the leakage energy is recycled to the output by using an integrated regenerative snubber. Indeed, these circuits allow soft-switching conditions, i.e., zero voltage switching and zero current switching for active and passive switching devices, respectively. The mentioned features along with a common ground connection of the input and output make the proposed topology a proper candidate for transformer-less grid-connected photovoltaic systems. The operating performance, analysis and mathematical derivations of the proposed dc–dc converter have been demonstrated in the paper. Moreover, the main features of the proposed converter have been verified through experimental results of a 1-kW laboratory prototype. [ABSTRACT FROM PUBLISHER]

An extended-duty-ratio (EDR) boost converter is studied extensively in this paper for high voltage gain applications with a wide input (and/or output) voltage range. The EDR is a unique combination of an interleaved, multiphase boost converter and switched capacitor configuration that achieves high voltage gain with significantly lower switch voltage stress and switching losses compared to conventional high-gain solutions. Most of the switches in the multiphase EDR experience only a fixed fraction of the output voltage ($1/M, 2/M$ , etc., where $M$ is the number of phases). Through extensive analysis over a wide operating range, it is shown here that the EDR boost converter has inherent current sharing among the phases only in a limited range of duty ratio— $(M-1)/M \leq D \leq 1$. As the duty ratio reduces beyond this range as required in wide input voltage applications, inherent current sharing property is lost. In this paper, techniques to ensure current sharing under all operating zones without requiring current sensors are presented. Instead of having equal duty ratio for each phase, it is adjusted for each phase according to the operating region of the converter. Extensive analysis is presented to derive the required duty ratio changes for the different phases. The proposed concept is validated with experimental results from a 250 W, 3-phase EDR boost, and GaN-based hardware prototype. [ABSTRACT FROM AUTHOR]

This paper proposes a family of soft-switching bidirectional converters. In many applications, the bidirectional converters operate over a wide range of duty cycle and load variations. In the proposed converters, in order to extend the zero-voltage switching operation range, two supplemental voltage sources utilizing passive components are implemented in the auxiliary circuit. By using this method, the soft-switching features are ensured for an extensive range of the converter duty cycles. This is achieved independent of the output power value or the converter operation mode, and so, soft switching is ensured within the entire converter operating region. In these converters, all semiconductors components are soft switched, and the auxiliary circuit does not contribute to the complexity of the control circuit. Also, no extra voltage stress exists on the main switches and the voltage stress on the auxiliary switches is lower than the main switches voltage stress. In this paper, the proposed bidirectional buck/boost converter is analyzed and to confirm the feasibility of the proposed method, experimental results of a 150-W prototype converter are presented. [ABSTRACT FROM PUBLISHER]

A new static synchronous compensator (STATCOM) based on the diode-clamped modular multilevel converter (DCM2 C) is proposed in this paper. In this converter topology, the capacitor voltage is clamped by using a low power rating diode in each submodule. The quantity of voltage sensors is significantly reduced and is free from the number of voltage levels. Furthermore, the voltage balancing control method becomes very simple and the capacitor voltage balance speed is fast. Based on the structure of modular multilevel converter, the DCM2C-STATCOM has the capability of Var compensation and negative-sequence current compensation. The topology characteristics and compensation control method of DCM2C-STATCOM are investigated in this paper. Experimental results obtained from a laboratory prototype validate that the capacitor voltage of the proposed DCM2C-STATCOM can be well balanced and the Var and negative-sequence current compensations are effective. [ABSTRACT FROM AUTHOR]

In this paper, eight ultrahigh-voltage gain dc–dc converters are proposed. These sets of converters are derived by the association of boost cells, coupled inductor, voltage multiplier, switched capacitors, and LC filter cells. The nonpulsating input and output converters are evaluated in terms of: principle of operation, voltage gain, voltage and current stress, estimated power losses, and efficiency. Following full analysis prototypes built in the laboratory show experimental results verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes the design of gray wolf optimizer (GWO) algorithm-based fractional order proportional integral (FOPI) controller for power factor correction (PFC) using interleaved dc–dc single ended primary inductance converter converter with improved performance characteristics such as speed, accuracy, and stability. The detailed analysis and modeling of the proposed converter are presented. The optimal parameters of FOPI controller are obtained using GWO algorithm to improve the speed of response of the system. FOPI controller provides better performance in terms of robustness and stability since it has one more adjustable parameter than the conventional proportional integral (PI) controller. The cascade control strategy is implemented for the proposed converter with GWO-based FOPI controller as inner current and outer voltage controllers for PFC and load voltage regulation. The performance characteristics of the proposed system are analyzed and compared with conventional and other optimization techniques using MATLAB/Simulink software. A prototype of the proposed converter controlled by TMS320C2000 microcontroller for an output power of 200 W is tested and validated with the simulation results. The proposed system is used for powering devices like robots in critical applications such as military, space craft, etc., where stability, speed, and accuracy are major concerns. [ABSTRACT FROM AUTHOR]

This paper presents a new highly integrable hybrid step-down converter that merges switched-inductor and switched-capacitor operations and significantly reduces onboard loss by using the input cable's parasitic inductance as its main inductor. This converter has the inductor placed at the input with a smaller voltage swing, leading to possible use of a smaller inductor and low-voltage rating switches that generally translate to reduced conduction losses. Analyses of converter operation and losses to reveal its original characteristics and design guidelines are presented to facilitate the components optimization. The converter architecture is verified by a proof-of-concept 15-W inductor-less lithium-ion battery charger prototype that uses a 1-m USB 3.0 cable as inductor. The converter, switched at 2 MHz from a 5-V input, experimentally achieves 89.7% peak efficiency and 6% higher efficiency at full load than a Buck converter counterpart. This high efficiency and zero onboard inductor yield a relative 45.7% onboard loss reduction at full load, promising excellent integration feasibility and superior system thermal management. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems having rechargeable batteries are prone to be complex and costly because multiple converters are necessary to individually regulate a load, PV panel, and battery. This paper proposes novel nonisolated multiport converters (MPCs) integrating a bidirectional pulsewidth modulation (PWM) converter and phase-shift-switched capacitor converter (PS-SCC) for standalone PV systems. A PWM converter and PS-SCC are integrated by reducing the total switch count, realizing the simplified system and circuit. In the proposed MPCs, two control freedoms of duty cycle and phase shift angle are manipulated to individually regulate the load, PV panel, and/or battery. The detailed operation analysis was performed to mathematically derive gain characteristics and zero voltage switching operation boundaries. For the battery discharging mode, in which the PV panel is not available and the MPC behaves as a single-input–single-output converter with two control freedoms available, the optimized control scheme achieving the lowest rms current is also proposed to maximize power conversion efficiencies. Various kinds of experimental verification tests using a 200-W prototype were performed to verify the theoretical analysis and to demonstrate the performance of the proposed MPC. [ABSTRACT FROM AUTHOR]

This paper presents a new configuration of high gain (HG) single ended primary inductor converter (SEPIC) with a ripple-free input current to maximize the efficiency of the PV panel for standalone water pumping system (WPS). The ripple eliminating circuit combined with the HG SEPIC converter to achieve reduced ripples in photovoltaic (PV) current is independent to the duty cycle control and hence, it can be easily integrated to the main power circuit of configuration. This circuit does not need any active switches, control, or drive circuit for its execution. The ripple eliminating circuit yields a complete removal of the electrolytic capacitor connected across the PV array and significantly reduces the inductance of the HG SEPIC converter. It also improves the response and power density of the dc–dc converter. The large gain of dc–dc converter enables the use of low-voltage PV panel and minimizes the partial shading and parasitic capacitance effects on PV array source. Due to the substantial compatibility between natural characteristics of switched reluctance motor (SRM) drive and WPS, a four-phase SRM drive is utilized in the proposed scheme. In addition, a single current sensor based maximum power point tracking technique is utilized in the proposed system, which helps to reduce the cost and improve the accuracy of the overall system. Analytical, simulated, and experimental results of the developed system are presented to demonstrate the performance of the system. [ABSTRACT FROM AUTHOR]

A novel high step-down dc–dc converter with voltage demultiplier cell is proposed in this paper, which is widely used in the high step-down applications such as electric vehicle and digital circuits. The combination of switched-capacitor and coupled-inductor is employed to build extended voltage demultiplier in the proposed converter, which makes a quite higher voltage conversion ratio than that of the existing counterparts. Thus, the proposed converter can achieve extremely low output voltage with an appropriate duty ratio, and the extreme duty cycle is avoided. Accordingly, voltage stress on power switches is greatly reduced. Then, mosfets with low conduction resistance could be utilized to reduce conduction loss. Importantly, zero-voltage switching could be achieved for the main switch, which promotes the conversion efficiency further. In addition, the coupled inductor operates not only as a filter inductor, but also as a transformer when the main switch is in the off state, which reduces the volume of the magnetic core and improves the power density of the converter. The operation principle, performance analysis, design considerations of the proposed converter and performance comparison with recent counterparts are discussed in detail, and finally, an experimental prototype is built to verify the theoretical analysis and performance of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, the Z-source converter is introduced to power factor correction (PFC) applications. The concept is demonstrated through a wireless power transfer (WPT) system for electric vehicle battery charging, namely Z-source resonant converter (ZSRC). Due to the Z-source network (ZSN), the ZSRC inherently performs PFC and regulate the system output voltage simultaneously, without adding extra semiconductor devices and control circuitry to the conventional WPT system such as conventional PFC converters do. In other words, the ZSN can be categorized as a family of the single-stage PFC converters. In addition, the ZSN is suitable for high-power applications since it is immune to shoot-through states, which increases reliability and adds a boost feature to the system. The ZSRC-based WPT system operating principle is described and analyzed in this paper. Simulations and experimental results based on a 1-kW prototype with 20-cm air gap between the system primary and secondary sides are presented to validate the analysis and demonstrate the effectiveness of the ZSN in the PFC of the WPT system. [ABSTRACT FROM PUBLISHER]

In this paper, a new multi-input multi-output (MIMO) dc–dc converter with high step-up capability is proposed for wide power ranges. Also, in order to increase each output voltage, diode–capacitor voltage multiplier (VM) stages are utilized in the proposed converter. The number of input stages, output stages, and VM stages are arbitrary and dependent on design conditions. At first, the general structure of proposed MIMO converter is presented. Then, in order to explain the converter operation, we walk through the design of a 1-kW four-input two-output example, including loss and efficiency calculations. We validate the design with a prototype that matches efficiency calculations. [ABSTRACT FROM AUTHOR]

The interleaved bidirectional buck–boost converter dual active half-bridge (IBBC-DAHB) dc–dc converter consists of two converters IBBC and DAHB and a coupled inductor. The IBBC-DAHB converter has significant features such as low ripple current at the low-voltage side, low current stress on the input inductors, voltage stress across the switches less than the high-voltage side, high voltage gain, and zero-voltage soft switching. The converter offers high efficiency using phase-shift modulation when it operates at a nominal design operating point. However, the efficiency decreases due to high circulating current, high current stress, and limited soft-switching range when the source and load voltages deviate from their nominal values. This paper employs both duty cycle and phase-shift modulation methods to improve the above mentioned shortcomings using voltage matching for the DAHB converter. The proposed converter is analyzed and a 500-W experimental prototype with 40–60 V input voltage and 400 V output voltage under 100 kHz switching frequency is implemented to verify the theoretical results. The maximum efficiency of 97.15% is achieved at 60 V and 400 W. A flat efficiency characteristic for the converter is derived by the proposed control method, where the efficiency at 20% of nominal load is 91% and much higher than the phase-shift control, which is 70.8%. [ABSTRACT FROM AUTHOR]

In this paper, an input-series flyback converter with the coupled-inductor-based passive snubber is proposed, where the input-series converter is based on transformer integration, and the passive snubber is composed of inductors, capacitors, and diodes. The inductors of the snubber in various series modules are made on a common magnetic core, and the coupled-inductor scheme is adopted. With the help of the coupled inductor, active input voltage sharing of the input-series converter can also be achieved after the switches are turned off, and voltage sharing of the switch in each series module can be ensured, which overcome the shortcomings of the existing input-series flyback converter. Active voltage sharing processes caused by the coupled inductor are analyzed in detail. Furthermore, the design guideline of the passive snubber is discussed. Finally, the experimental study has been done on a 1500 Vdc/60 W laboratory-made prototype composed of three flyback series modules, and the feasibility of the proposed method and the theoretical analysis is verified by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an expandable single-input three-output high step-up dc–dc boost converter is proposed. The voltage conversion ratio of the output ports of the converter can be increased by inductor-diode-capacitor and diode-capacitor cells. The proposed converter can be applied in renewable energy conversion systems, such as in photovoltaic and fuel cells. Also, due to the three output ports of the converter, it can be utilized in portable devices which require high voltage conversions. The main advantage of the proposed converter is supplying loads with different voltages and current ranges due to the expandable structure of the converter. Besides, the proposed converter has the merit of achieving high voltage gains at high frequencies without preselecting wide duty cycles. Furthermore, the proposed converter is able to achieve higher voltage ranges without having any transformer or coupled inductors in its structure; consequently, the related drawbacks are avoided. The switching pattern of the converter is simple and both switches are on and off simultaneously. In this study, a single switching period of the proposed converter, the voltage conversion ratios of the output ports and the expanded form of the structure are analyzed theoretically. Finally, to verify the theoretical results, the experimental results for 40-V input/200-V, 100-V and 360-V outputs with total 600-W output power are extracted and compared with each other. [ABSTRACT FROM AUTHOR]

In a power electronics system, an electrolytic capacitor (E-Cap) is widely used, whose performance degradation can be reflected by the change of capacitance (C) and equivalent series resistance (ESR). This paper proposes a new online C and ESR monitoring scheme for the output electrolytic capacitor in a discontinuous conduction mode (DCM) flyback converter. The mathematical relationship between the instantaneous capacitor voltage and other parameters is analyzed and then the scheme of undetermined coefficients based on the multiple-spot sampling and least square method is further proposed. In addition, considering the particularity of high ripple current and the resultant voltage ripple variation range, especially with the temperature, an inverse ripple voltage isolation amplifier with variable amplification factor and negative voltage elimination is put forward so as to make digital signal processor identify the temperature change easily. The proposed scheme is noninvasive as only voltage signals need to be sampled and no current sensor is necessary. A prototype is built and the experiments are made to verify the effectiveness of the proposed method, from which the data are in accordance with the results measured by an LCR meter. [ABSTRACT FROM AUTHOR]

A high-performance impedance-source converter utilizing switched inductor is proposed in this paper, which can be adopted in the applications demanding high-voltage conversion. The proposed converter not only retains the advantage of quasi-Z-source of sharing common ground between the input and output but also possesses the superiorities of enhanced boost ability and lower stresses as well as higher efficiency. Mathematical analysis of the converter and its performance comparison with other converters are presented in detail. Finally, a 100 W prototype is built and the experimental results are provided to verify the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

The ultra-high voltage gain dc–dc converters are extremely required because of the low voltage level of many nonpolluting power resources. This paper proposes an ultra-high voltage gain converter based on an interleave technique and using three-winding coupled inductor and voltage multiplier cell. The interleave technique is useful for reducing the size of the filter components. In the proposed converter, high voltage gain is achieved without extreme duty cycle of solid-state switches. The voltage stress across the semiconductor devices can be reduced by increasing the turn ratio of the secondary of the coupled inductors. In addition, because of the implementation of the interleave structure, peak-to-peak variation of the main input current and switching losses are substantially reduced. The steady-state principles of the proposed converter in continuous conduction mode operation are given. Also, design equations are presented. Validity and performance of the proposed converter are surveyed by simulation and experimental results of a 120 W prototype. [ABSTRACT FROM AUTHOR]

An enhanced DC–DC converter is proposed in this paper, based on the combination of the Cuk and SEPIC converters, which is well-suited for solar photovoltaic (PV) applications. The converter uses only one switch (which is ground-referenced, so simple gate drive circuitry may be used), yet provides dual outputs in the form of a bipolar DC bus. The bipolar output from the DC–DC converter is able to send power to the grid via any inverter with a unipolar or bipolar DC input, and leakage currents can be eliminated if the latter type is used without using lossy DC capacitors in the load current loop. The proposed converter uses integrated magnetics cores to couple the input and output inductors, which significantly reduces the input current ripple and hence greatly improves the power extracted from the solar PV system. The design methodology along with simulation, experimental waveforms, and efficiency measurements of a 4-kW DC–DC converter are presented to prove the concept of the proposed converter. Furthermore, a 1-kW inverter is also developed to demonstrate the converter's grid-connection potential. [ABSTRACT FROM AUTHOR]

A high step-up DC–DC converter with active switched LC-network is proposed in this paper, which can be used in the photovoltaic system as the front-end stage to generate the required DC bus voltage. Based on the transformerless DC–DC converter with an active switched inductor (ASL) network, this proposed converter introduces an active switched capacitor (ASC) network, where only one capacitor and one diode are added, while the voltage gain is efficiently increased by a compound of ASL and ASC networks. The structure of the proposed converter is simple and voltage stresses on the additional diode and capacitor are low. In addition, unlike other voltage-boosting structures that utilized switched capacitor, the proposed converter avoids the extreme instantaneous currents of capacitor. The detailed analysis of the proposed converter and performance comparison with recently published ASL network-based converters are presented. Finally, a 100 W, 20/200 V prototype circuit is operated to verify its performance. [ABSTRACT FROM AUTHOR]

A dual-input high step-up DC/DC converter with zero voltage turn-off (ZVT) auxiliary circuit is presented in this paper. The cost of whole photovoltaic (PV) power could be decreased significantly by the proposed converter because it allows two PV panels to be connected at the same time. ZVT auxiliary circuit provides soft switching in a wide range of load variations with six passive components. Turn-off switching losses could be decreased and the efficiency of the whole converter could be improved. In , the operation principle and performance characteristics of the proposed converter have been analyzed and an 800 W experimental prototype has been built to validate the analytical results in. In , a dual-input maximum power point tracking (DMPPT) control algorithm has been designed for the proposed converter. Experimental results show that two PV panels can achieve the maximum power output state separately by the proposed DMPPT control algorithm. [ABSTRACT FROM AUTHOR]

The non-inverting buck-boost converter has emerged as one of the most promising topologies for distributed maximum power point tracking applications. Pressure to reduce cost and volume of photovoltaic module integrated converters often compels bootstrap capacitor type gate drivers. The bootstrap technique is a simple and economical solution to create a floating power supply for high-side gate drivers. However, it comes with a major challenge, as the low-side switch must be periodically turned on, to recharge the high-side bootstrap capacitor. In the buck and the boost mode, one of the switching legs of the converter must be held with the high-side switch on, which eventually discharges the high-side capacitor. When the non-inverting buck-boost input voltage is regulated by means of a single voltage loop, recharging the bootstrap capacitor causes an undesired ripple in the PV module voltage, degrading the regulation quality. In order to mitigate this problem, this paper proposes a cascaded control technique, entailing regulation of the PV module voltage and inductor current. The cascaded controller dramatically improves the rejection of the disturbance induced by the periodic recharge of the bootstrap capacitor, thanks to the fast action of the current loop, regulating the average value of the inductor current. Converter transfer functions and controller design are derived and validated. Experimental results clearly show that the cascaded control scheme outperforms the traditional voltage control scheme, resulting in a better regulation of the PV module voltage. This main advantage comes at the cost of an additional measurement of the average inductor current. [ABSTRACT FROM AUTHOR]

In this paper, analysis and design of a three-phase-isolated Cuk-based power factor correction (PFC) converter have been proposed. The proposed converter is operated in discontinuous output inductor current mode to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the sensing of current. This makes the system more reliable and robust. The converter requires only one simple voltage control loop for output voltage regulation, and all the power switches are driven by the same gate signal which simplifies the gate driver circuit. The detailed operation of the converter and design calculations are presented. And also a small-signal model of the converter by using current injected equivalent circuit approach is presented to aid the controller design. The experimental results from a 2-kW laboratory prototype with 208-V line-to-line input voltage, 400-V output voltage are presented to confirm the operation of the proposed converter. An input power factor of 0.999, an input current total harmonic distortion of as low as 4.06%, and a high conversion efficiency of 95.1% are achieved from laboratory prototype. [ABSTRACT FROM AUTHOR]

Cascaded multilevel inverter (CMI) is one of the most popular multilevel inverter topologies. This topology is synthesized with some series-connected identical H-bridge cells. CMI requires several isolated dc sources which brings about some difficulties when dealing with this type of inverter. This paper addresses the problem by proposing a switched-capacitor (SC)-based CMI. The proposed topology, which is referred to as switched-capacitor single-source CMI (SCSS-CMI), makes use of some capacitors instead of the dc sources. Hence, it requires only one dc source to charge the employed capacitors. Usually, the capacitor charging process in a SC cell is companied by some current spikes which extremely harm the charging switch and the capacitor. The capacitors in SCSS-CMI are charged through a simple auxiliary circuit which eradicates the mentioned current spikes and provides zero-current switching condition for the charging switch. A computer-aid simulated model along with a laboratory-built prototype is adopted to assess the performances of SCSS-CMI, under different conditions. [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]

A novel high step-up converter, which is suitable for a renewable energy system, is proposed in this paper. The proposed converter is composed of the dual switches structure, three-winding coupled inductor, and two voltage multiplier cells in order to achieve the high step-up voltage gain. The dual switches structure is beneficial to reduce the voltage stress and current stress of the switch. In addition, two multiplier capacitors are, respectively, charged during the switch-on period and switch-off period, which increases the voltage conversion gain. Meanwhile, the energy stored in the leakage inductor is recycled with the use of clamped capacitors. Thus, two main power switches with low on-resistance and low current stress are available. As the leakage inductor, diode reverse-recovery problem is also alleviated. Therefore, the efficiency is improved. This paper illustrates the operation principle of the proposed converter; discusses the effect of the leakage inductor; analyzes the influence of parasitic parameters on the voltage gain and efficiency, the voltage stresses and current stresses of power devices are shown; and a comparison between the performance of the proposed converter and the previous high step-up converters is performed. Finally, the prototype circuit with input voltage 20 V, output voltage 200 V, and rated power 200 W is operated to verify its performance. [ABSTRACT FROM AUTHOR]

In order to balance the light-emitting-diode (LED) current in each channel, many active and passive methods have been investigated. Among the various methods, the passive method using the LLC converter with a blocking capacitor or flyback converter with a current-sharing transformer (CST) in the secondary side is one of the simplest methods because it does not use any active component. However, the LLC driver requires two main switches and external resonant inductor to obtain a wide output voltage range. Also, flyback with a CST requires an additional magnetic component for CST and high-voltage rated diodes, resulting in the limitation of the cost and system volume. In this paper, a single-switch forward-flyback driver for a two-channel LED is proposed. The most powerful advantage of the proposed driver is the cost effectiveness, since it eliminates additional magnetic component. Furthermore, due to the reduced-voltage stress on rectifier diodes compared to the flyback driver, the proposed driver achieves a higher efficiency. The prototype of the 150–100-V/0.3-A two-channel LED verifies the effectiveness of this paper. [ABSTRACT FROM PUBLISHER]

This paper introduces a SEPIC-derived converter suited for alternative energy generation applications. The proposed converter utilizes tapped inductor and charge pump techniques to achieve high step-up gain and a passive regenerative snubber to attain high efficiency. Compared with earlier counterparts, the proposed converter has the advantage of continuous input current, which can be helpful in attaining accurate tracking of maximum power point of solar panels. The paper presents principle of operation, theoretical analysis, and design guidelines. Theoretical expectations were confirmed by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes an interleaved buck converter (IBC) with continuous input current, extremely low output current ripple, low switching losses, and improved step-down conversion ratio. Unlike the conventional IBC, the proposed converter has a continuous input current, and its output current ripple is extremely low. The proposed converter has a lower voltage stress in comparison to the conventional IBC and can also provide a high step-down ratio, which makes it a proper choice for high-power applications where a nonisolated step-down converter with low output current ripple and continuous input current is required. Also, the proposed converter can provide current sharing between two interleaved modules without using additional current-sharing control method. All of these benefits are obtained without any additional stress on the circuit components. A prototype converter with 200-V input and 24-V–10-A output is implemented to verify the theoretical analysis. Operational principles and experimental results are presented in this paper. [ABSTRACT FROM PUBLISHER]

A single-phase bridgeless Cuk ac/dc power factor correction (PFC) rectifier with positive output voltage is proposed in this paper. For low output voltage product applications, the rectifier is designed to convert high input voltage to low output voltage. Due to no bridge diodes required and thus decreased input conduction losses, the proposed rectifier efficiency can be improved. The proposed rectifier operates in discontinuous conduction mode, and the current-loop circuit is hence not needed. In addition, only a single switch is used in the rectifier to simplify the control circuit design. A simple translation method to have the positive output voltage in the Cuk converter is presented in the rectifier to reduce the component counts and the cost. The operational principles, steady-state analysis, and design procedure of the proposed rectifier are addressed in detail in this paper. Simulation and experimental results obtained from a 150-W rated prototype circuit with input of 90–130 Vrms, 60 Hz, and output of 48 Vdc have verified the validity of the proposed rectifier. [ABSTRACT FROM PUBLISHER]

This paper presents two circuits that allow us to accurately detect either the inductor current zero crossing, or the continuous/discontinous conduction modes boundary in the switched-mode dc-dc converters. Achieved detection accuracy allows us to improve the control and efficiency of the integrated high-output current converters, i.e., converters with low-resistance power switches. Detection is based on the voltage zero-cross detector, which provides ideally zero input-referred offset and very fast results. The concept of voltage polarity detector is based on the association of a dynamic current mirror and a simple autozero comparator. This paper describes the main concept of both circuits, aspects of the design allowing us to achieve high accuracy, and presents obtained results. Circuits' performances are demonstrated on the integrated step-down dc-dc converter with IOUT = 2.5 A 30-mΩ NMOS power stage. Measured accuracy of the detection is in order of <;15 mA. [ABSTRACT FROM AUTHOR]

Among the various cell balancing circuits for series-connected batteries, the bidirectional cell-to-cell balancing structure using two switches per cell shows good balancing ability. However, an increase in the number of switches leads to an increase in both cost and size. To reduce the number of switches, this paper proposes a new cell-to-cell balancing circuit with a center-cell concentration structure. The proposed circuit collects the charges of an overcharged cell into the center cell, and then the collected charges are redistributed to the other cells. The proposed circuit has a unidirectional balancing structure with single switch per cell. However, it can achieve competitive balancing ability when compared with the bidirectional structure. In this paper, the operational principles of the proposed circuit are analyzed, and a comparison between the conventional and proposed circuits is shown. To verify the validity of the proposed circuit, experiments with 15.5-Ah batteries are carried out, and the experimental results demonstrate the improved cell balancing ability although a single switch is used per cell. [ABSTRACT FROM AUTHOR]

Due to the relatively low output voltage of photovoltaic (PV) source, a high step-up converter with high efficiency is needed when the PV source is connected to the power grid. A novel high step-up converter based on two switched capacitors and a coupled inductor is proposed in this paper. The operating principle is analyzed and the voltage gain is derived. A 100-W prototype is fabricated in the laboratory to verify the theoretical analysis, and the highest efficiency is 96.4%. [ABSTRACT FROM PUBLISHER]

This paper presents an isolated bidirectional interleaved converter with minimum active switches to achieve high conversion ratio. The proposed converter has symmetric structure for easy control, and incorporates two coupled inductors for galvanic isolation and high voltage ratio achievement. A dual-inductor-capacitor-diode (LCD) snubber with common resonant inductor at low-voltage side is in charge of leakage energy recycling for efficiency improvement. In addition, the converter can obtain interleaved terminal current at low-voltage side for lowering current ripples, no matter in boost mode or buck mode. Finally, a 400-W prototype is built for validation, where the experimental results indicate that the highest efficiencies in boost and buck modes are 95.5% and 95.4%, respectively. [ABSTRACT FROM PUBLISHER]

In this paper, a new negative output (N/O) buck–boost converter, which can be applied for applications that need wide range of inverse voltage, is proposed. The steady-state, small-signal model and power losses of the proposed converter operating in a continuous conduction mode are analyzed. Comparisons among the traditional buck–boost converter, N/O hybrid buck–boost converter and N/O self-lift Luo converter are presented, and it is found that the proposed converter possesses a widest voltage conversion ratio in these four converters. Finally, a prototype is built, and the simulated waveforms from the PSIM software and the experimental results are presented for validation. [ABSTRACT FROM AUTHOR]

Boost-derived hybrid converter (BDHC) is a single-stage converter that produces both dc and ac output voltages. The operation of BDHC under continuous conduction mode is satisfactory. However, the nonzero discontinuous conduction mode (NZ-DCM) and standalone ac operation restrict the stable operation of the converter. To mitigate these limitations, modified BDHC (MBDHC) is proposed in this paper. The main idea behind these changes is to redeem NZ-DCM by forced continuous conduction mode (FCM). The adverse effect of NZ-DCM in a BDHC is analyzed in terms of ac output voltage total harmonic distortion, and dc output voltage ripple. This analysis is further extended for MBDHC to highlight the benefits of FCM. Moreover, for hybrid loads, the efficiency of MBDHC is compared with its counterpart BDHC and cascaded boost inverter. [ABSTRACT FROM PUBLISHER]

Power systems for exploration rovers tend to be complex as three separate converters are necessary; in addition to a main dc–dc converter and cell equalizer for rechargeable energy storage cells, an equalizer for photovoltaic (PV) modules is desirably equipped in order to preclude negative impacts of partial shading. This paper proposes the pulse width modulation (PWM) converter integrating voltage equalizers for PV modules and energy storage cells. The proposed integrated converter comprises a switched capacitor converter, PWM buck converter, and series-resonant voltage multiplier that perform PV equalization, power conversion from the PV modules to the load, and cell equalization, respectively. Three converters can be integrated into a single unit with reducing the total switch counts, achieving not only system-level but also circuit-level simplifications. The derivation procedure of the integrated converter is explained, followed by the operation analysis. Experimental tests were performed using series-connected supercapacitor (SC) modules and solar array simulators to emulate a partial shading condition. With the integrated converter, the extractable maximum power from the PV modules significantly increased while voltage imbalance of SC modules was adequately eliminated, demonstrating the integrated performance of the proposed converter. [ABSTRACT FROM AUTHOR]

Dynamic voltage restorer (DVR) technology has become a mature power quality product. In high-power applications, DVR using a multilevel converter is commonly used. However, DVR using a multilevel direct pulse width modulation (PWM) ac–ac converter has not been well studied. This paper presents a new DVR topology using a cascaded multilevel direct PWM ac–ac converter. In the proposed scheme, the unit cell of the multilevel converter consists of a single-phase PWM ac-ac converter using switching cell structure with coupled inductors. Therefore, the multilevel converter can be short- and open-circuited without damaging the switching devices. Neither lossy RC snubber nor a dedicated soft commutation strategy is required in the proposed DVR. This improves the reliability of the DVR system. The output voltage levels of the multilevel converter increase with the number of cascaded unit cells, and a high ac output voltage is obtained by using low-voltage-rating switching devices. Furthermore, a phase-shifted PWM technique is applied to significantly reduce the size of the output filter inductor. A 1-kW prototype of single-phase DVR is developed, and its performance is experimentally verified. Finally, the simulation results are shown for a three-phase DVR system. [ABSTRACT FROM AUTHOR]

Traditional load regulation methods for a resonant converter mainly rely on frequency modulation. It is always a tradeoff between the design of the resonant network and the range of load. Especially for wireless power transfer (WPT) systems, the resonant network usually has a high quality factor. Small variation on frequency leads to huge drop in gain and efficiency. Due to this problem, many WPT systems are unregulated and they need one or two more front-end stages to regulate the dc bus voltage and perform power factor correction (PFC). In order to lower the cost and complexity of two- or three-stages structure, a single-stage solution with a silicon carbide (SiC) based Z-source resonant converter (ZSRC) was recently proposed. The Z-source network provides high reliability as being immune to shoot-through problems. Additionally, a ZSRC can boost the dc bus voltage while the traditional voltage-source inverter can only produce a lower voltage. However, the load regulation of this new topology has not been addressed. Two effective load regulation methods with constant frequency are presented for this SiC-based ZSRC specifically. Operation principle of the two load regulation methods are described in this paper. Experimental results based on a 200-W scale-down prototype with a full-bridge series resonant dc–dc converter are presented to illustrate the mechanism of these two methods. [ABSTRACT FROM AUTHOR]

A new soft-switching pulse-width-modulated (PWM) full-bridge converter is proposed in this paper. The proposed converter has zero voltage switching (ZVS) in all its switches with fewer conduction losses than other ZVS-PWM full-bridge converters, due to a novel auxiliary circuit scheme. In this paper, the operation of the new converter is explained and analyzed, a design procedure is presented and demonstrated with an example, and experimental results that confirm the feasibility of the converter are also presented. [ABSTRACT FROM AUTHOR]

This paper discusses a new circuit configuration and a new control method for a single-phase ac–dc converter with power factor (P.F.) correction and a power pulsation decoupling function. The proposed converter can achieve low total harmonic distortion (THD) on the input current and the power pulsation decoupling function between the input and output sides, which allows low output voltage ripple even on a small output energy buffer at the same time using an active buffer. Therefore, the proposed converter does not require large smoothing capacitors or large smoothing inductors. The buffering energy is stored by a small capacitor, which controls the variation of the capacitor voltage through the active buffer. In this paper, the fundamental operations of the proposed converter are investigated experimentally. The experimental results reveal that the input current THD is 1.44%, the rate of the output voltage ripple is 6.33%, and the input P.F. is over 99%. In addition, a maximum efficiency of over 96% is obtained for a 750-W prototype converter. [ABSTRACT FROM PUBLISHER]

The boost converter with a voltage multiplier cell allows the static gain extension by means of the switching capacitor technique, reducing the duty cycle needed to achieve the same voltage gain when compared to the conventional boost converter. However, the modeling of this converter is complex and requires the use of advanced techniques due to the resonant inductor. Thus, this paper aims to present a reduced-order model of this converter without the resonant energy exchange between the capacitors, so that the state-space averaging technique can be applied assuming small ripple in the state variables. In addition, this paper presents the design of a control system for the boost converter with a voltage multiplier cell. The adopted strategy employs an inner loop to control the input current and an outer loop for the output voltage regulation. Extensive analysis based on simulations and an experimental prototype demonstrate that the proposed modeling, although simplified, is sufficient for an adequate control system design, ensuring good voltage regulation, and fast transient responses. [ABSTRACT FROM PUBLISHER]

A new three-phase single-stage rectifier is proposed in this paper. The outstanding features of the proposed rectifier are that it can produce input currents that do not have deadband regions and an output current that can be continuous when the converter is operating from maximum load to at least half of the load. In this paper, the operation of the new converter is explained, its features and design are discussed in results, and its operation is confirmed with experimental results obtained from a prototype. [ABSTRACT FROM PUBLISHER]

Interleaving is a technique that is commonly used due to its inherent reduction of current ripple and filter capacitance size. However, optimal interleaving is only achieved when the switching cells are identical. Variations of the filter inductance, which are caused by the manufacturing process or magnetic material properties, may lead to the total current ripple of all phases significantly larger than that of the ideal case in steady state, and slow down the energy transfer speed during the transient response. Consequently, in order to meet the voltage ripple and dynamic response requirements of multiphase converters, the calculation of the output capacitor under inductance mismatches has to be reconsidered, which has been rarely mentioned previously. This paper proposes a method to estimate the effect of inductance mismatches on output capacitance selection from two aspects including steady state and transient state. The proposed methodology enables mathematical expressions that allow us to calculate the maximum value of the capacitor considering nonidealities. Monte Carlo simulation is also used during the analysis by varying all of the inductors’ values with respect to tolerance and distribution type to identify the worst case values in real applications, according to this approach, the principle of when the worst condition happens is summarized. Simulated and experimental results of a four-phase buck converter are presented in this study. Good agreement between the estimates and the measured values is demonstrated. [ABSTRACT FROM AUTHOR]