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The paper develops two computationally efficient models, namely a detailed equivalent model and an average-value model, with provisions for representation of the critical state of converter blocking, for modular multilevel converters with embedded storage. These models are indispensable in the simulation of dc faults. The developed detailed equivalent model provides accuracy that matches electromagnetic transient (EMT) simulations, with much reduced computational burden; the developed average-value model represents the averaged behavior of the converter by neglecting switching transients. Both models are extensively evaluated in the context of an HVDC system against benchmark results form a detailed switching model developed in PSCAD/EMTDC. The results confirm the validity and accuracy of the models for steady state, transient, and faulted operating conditions including when the converter is blocked in response to a dc fault. [ABSTRACT FROM AUTHOR]

A space vector modulation (SVM) technique of a dual-inverter system for an open-end winding motor drive is described in this paper, where one inverter has a battery power source and the other has an only capacitor across the dc bus. The SVM must be achieved to operate the motor with field-oriented control and simultaneously to control the capacitor voltage at a constant value by using redundant switching states of the dual-inverter system. The control of the capacitor voltage is carried out by selecting a charging or a discharging mode in each redundant switching state, taking the instantaneous motor power factor into account. In addition, it is also required to reduce the error voltage pulses, which are generated in output multilevel voltage waveforms during the dead time. The compensation method of the existing dead-time scheme and the improved SVM sequence to reduce the error voltage vectors are proposed in this paper. The proposed methods are examined through several experimental tests and are confirmed to generate superior output voltage waveforms from the viewpoint of the measured total harmonic distortion and dv/dt. [ABSTRACT FROM AUTHOR]

Most of the two-stage converters for electric bike battery charging comprise of a boost converter for power factor correction (PFC) followed by a dc–dc converter with universal input voltage. These two-stage conversions suffer from poor efficiency and increased component count. In this paper, a single-stage switched inductor Cuk converter based PFC converter is proposed, which offers high step-down gain, low current stress, high efficiency, and reduced component count. The operational analysis and design equations for various components of the proposed converter are carried out in continuous current mode. This paper presents mathematical modeling, analysis, simulation, and experimentation on the proposed converter rated for 500 W, 48 V/10.4 A. The performance investigation of the proposed converter with respect to power quality indices like voltage total harmonic distortion (THD), current THD, and total power factor is carried out with various types of loads such as resistive load and battery load in both constant voltage (CV) and constant current (CC) mode. Furthermore, the dynamic performance of the proposed converter with battery charging is investigated in CV mode and CC mode with respect to the wide range of supply variations. [ABSTRACT FROM AUTHOR]

This paper proposes a current-fed single-phase inverter without constant intermediate DC link. It eliminates electrolytic capacitor from the DC-link and introduces an intermediate pulsating DC bus. The proposed topology is modular with three full-bridges making it scalable for high-power applications. New pulsating-DC-modulation for back-end pulsating DC-link inverter and secondary modulation (SM) for front-end DC-to-pulsating DC converter is proposed. Soft-switching and device voltage clamping of both primary side and secondary side devices of front-end current-fed full-bridge converter is realized. A rotating partial hybrid pulsewidth modulation has been introduced. One leg of inverter is commutated at a low switching frequency, while the other leg is operated at a high switching frequency for partial period of a line frequency cycle. Thus, switching losses of the back-end inverter are considerably reduced. Rotating mechanism is used to equalize the switching losses of four switches of the inverter. This paper presents detailed operation and analysis of the topology with a proposed modulation scheme. Simulation and experimental results validate the effectiveness and accuracy of the proposed modulation scheme as well as soft-switching and performance of the converter. [ABSTRACT FROM PUBLISHER]

DC electric springs (DCES) are emerging technologies for the (i) regulation of mains voltage against the intermittent renewable generations and (ii) harmonic cancellation in dc microgrids. When conventional converter topologies (e.g., half-bridge or full-bridge converter) are adopted as DCES, the battery storage of the DCES has to process both the dc power and the ac harmonic power. The pulsating ac power can severely reduce the lifetime of the battery. To address this issue, a hybrid-DCES (H-DCES) is proposed in this paper to perform (i) and (ii) in a decoupled manner. With a modified topology and control method, the H-DCES can divert the ac current to the ground and retains the function of manipulating noncritical load for dc voltage regulation. The immediate benefits of this H-DCES are the reduction of storage capacity and a prolonged lifetime of the battery. Both the operating principle and the mathematical model of the proposed H-DCES are analyzed in this paper. A prototype of the H-DCES is practically tested in a 48-V dc grid. The experimental results show that the H-DCES can realize the decoupled operation of dc voltage regulation and harmonic cancellation. Simulation studies further demonstrate that the H-DCES requires less storage capacity than its counterparts. [ABSTRACT FROM AUTHOR]

On account of complementary control, reduced size, and energy saving, the switched-capacitor (SC) based equalizer becomes promising for the energy management of energy storage system. Traditionally, the number of the bypass capacitor in the SC based equalizer equals to the number of the battery module in series or parallel connections. The amount of bypass capacitors is enormous, thus costly and bulky for electric vehicles (EVs). In this paper, the integrated energy storage is proposed to reduce cost and save space, meanwhile, the equalizations between the batteries and the ultracapacitors (UCs) are achieved by the reutilization of SC network. UCs not only perform as energy storage units, but also work as energy exchange units. Thus, the number of balanced elements can be reduced significantly. The operational principles of the storage system and the analyses of the balancing process are examined in detail. The system simulation is performed for functionality evaluations. Meanwhile, an experimental prototype is also implemented for six cells to demonstrate the balancing process. The accordance of experiment and simulation can further testify the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, an electric vehicle (EV) battery charger with interleaved Landsman converter (ILC) followed by a flyback converter, is designed and evaluated for improved power quality (PQ) charging of battery. A built-in wave-shaping is obtained at the charger front-end due to improved PQ characteristics of ILC. This PFC converter consists of two Landsman converter cells, which are designed in discontinuous conduction mode (DCM) to share the input and output currents. The current sharing at input results into lower input current ripple as well as peak current stress through the switch, is reduced. This, further improves the input current harmonics profile. Moreover, the reduced output voltage ripple gives reduced rms current in the output capacitor. A phase shift PWM scheme (PSPWM) is used for ILC and the duty cycle for the switches is selected below 50%. This allows the ripple cancellation at line and load sides. The interleaving at PFC stage as well as DCM based design ensures a low cost charging solution as compared to the conventional Landsman converter (CLC) based chargers in this power range. However, the flyback converter provides the current control during the charging of the battery in constant current (CC) and constant voltage (CV) regions. The harmonics spectrum of mains current follows the recommended PQ regulations over a range of varying line voltages and loadings. [ABSTRACT FROM AUTHOR]

Load-independent output characteristics of inductive power transfer (IPT) systems are increasingly popular in battery charging. This paper proposes a novel variable-parameter T-circuit (VT) for an IPT system charging a battery with constant current (CC) or constant voltage (CV) output. The VT can transfer a CC/CV input to a CC or CV output by using an ac switch and a passive component (inductor or capacitor). An IPT system with a VT for CC–CV charging can reduce the number of passive components and ac switches. Besides, the proposed VT merits more design freedom of charge current/voltage with the constraints imposed by the loosely coupled transformer parameters compared to that of the traditional one. In addition, there are three kinds of VTs for various IPT charging systems with different requirements. A 400 W laboratory-scale prototype with a 150 mm air gap was built to verify the theoretical analyses. Both electronic load and lead-acid battery are utilized to verify the charging profile of the proposed method. The experimental results of the IPT system indicate that the fluctuation of the charging current in CC mode is less than 2%, and the change rate of charging voltage in CV mode is within 2.9%. The maximum overall efficiency 93.93% of the charging system is achieved from a dc 110 V input to a dc 100 V output. [ABSTRACT FROM AUTHOR]

Analysis and design of a single-switch high step-up coupled-inductor boost converter are presented in this paper. With the aid of the coupled inductor, the proposed converter can achieve high-voltage gain without extreme duty cycle. Also, low switch voltage stress can be achieved, thus low-voltage-rating mosfet is allowed to lower the conduction loss. Moreover, the proposed converter features continuous input current, which is desirable and friendly to the battery, fuel cell, and photovoltaic applications. In addition, the reverse recovery problem of the diodes can be alleviated and leakage energy can be recycled. The operation principles and characteristics of the proposed converter are discussed. Experimental results are provided to verify the theoretical analysis. [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]

A modular quasi-resonant bidirectional dc–dc converter composed of half-bridge gallium nitride modules (HBGM) with reduced switch voltage stress is proposed in this paper. By using an auxiliary capacitor, a resonant circuit is formed to shape the current and voltage so that zero-voltage switching at turn-on instant is achieved. Since the switching loss dominates the power losses in a high-frequency dc–dc converter, the soft-switching performance leads to a noticeable reduction in the total loss; so, the operating temperature will decrease, and consequently, size of the heatsink will be reduced. The proposed circuit takes advantage of enhancement-mode gallium nitride (eGaN) switches regarding their small on-resistance RDS(on), low gate charge, and fast switching speed to improve both efficiency and power density. The main performance issue of adopting GaN switches in a bidirectional dc–dc converter is the high voltage stress of GaN devices, which is handled by connecting the HBGM in the active-clamped stacked configuration, as well as optimizing printed circuit board layout design. Finally, a 1 kW, 600 V laboratory prototype operating at 100 kHz is implemented to validate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper introduces a new zero current switching topology for parallel balancing of serially connected batteries string. The main advantage of the balancing concept in this study is that energy is transferred only when the cells are unbalanced. As a result, the power losses are significantly reduced since no current circulates through the system when balanced. This has been enabled by a modification of an isolated series-resonant converter operating in a discontinuous conduction mode. A single transformer for two cells is used, as opposed to conventional isolated topologies that require a transformer per cell. The realization is simple and sensorless. Experimental results have been obtained by a prototype of two modules balancing four series-connected batteries. [ABSTRACT FROM AUTHOR]

In this paper, a resonant current-mode receiver is studied to charge low-voltage batteries wirelessly for supplying medical implantable systems. To increase efficiency, the root-mean-square (rms) current in the LC tank of the receiver (RX) is reduced by using a voltage-boosted current-mode (VBCM) receiver. This receiver combines the conventional current-mode receiver with a switched-capacitor converter to boost the voltage instantaneously at the switching node ($V_{X}$) of coil. Owing to the suggested technique, the receiver directly charges a low-voltage battery while maintaining a small rms current without using a complex voltage regulator. The receiver achieves an efficiency as high as 84.7% with a 1.1 V battery while operating at the resonant frequency ($f_{{\text{reso}}}$) of 6.78 MHz. The power delivered to the output ($P_{O}$) is in the range from 1.5 to 50 mW. The VBCM receiver was fabricated by 180 nm CMOS technology with a total active area of 0.22 mm2. [ABSTRACT FROM AUTHOR]

An improved bridgeless (BL) Cuk converter-based electric vehicle (EV) battery charger with high power factor and increased efficiency is designed and developed in this paper. It provides low cost and high-power-density-based charging solution for the EV. This charger incorporates less number of devices operating over one switching cycle, which reduces the additional conduction loss incurred by a diode bridge rectifier of the conventional charger. Hence, it improves the charger's efficiency. The added advantage of the proposed topology is that the unwanted capacitive coupling loop is removed, as well as the unwanted conduction through the body diode of the inactive switch in the previously developed BL Cuk converter is avoided. This significantly improves the charger's efficiency. For the constant current and constant voltage charging, the commands are synchronized by a flyback converter. The proposed charger draws a sinusoidal current from ac mains and the total harmonic distortion in the supply current is reduced to the limits specified by the IEC 61000-3-2 guidelines. The improved efficiency and power quality indices of the proposed charger are investigated to demonstrate its satisfactory charging operation at all operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a highly efficient 3.3-kW single-stage on-board charger (OBC). The proposed OBC consists of two interleaved cells sharing a full-bridge diode rectifier. Each cell is composed of an active clamp circuit and a series resonant circuit. The proposed OBC provides zero-voltage switching of all switches and reduces the reverse-recovery problem by zero-current switching of the output diodes. The interleaved technique maintains the proper power level with high efficiency. The proposed control algorithm enables power factor correction by the OBC without any auxiliary circuit and balances the input current between the two cells. In addition, the proposed converter requires no electrolytic dc-link capacitor, ensuring compact size and a long lifetime. Owing to these features, the proposed OBC efficiently outputs a high power factor over a wide power range and achieves reliability with a simply structured, single-power processing step. Therefore, the proposed OBC is potentially feasible for automotive applications. Finally, the theoretical analysis is confirmed in a 3.3-kW prototype and validated in experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a novel single-switch dc/dc converter for the future renewable electric energy delivery and management system to implement the distributed renewable energy resources (DRER). The DRER is responsible for the maximum power point tracking of the photovoltaic panel (PV) module and also for the control of central energy storage device. Due to the characteristics of the PV module and the dc-bus, the single power stage must provide low current ripple in the input and output terminals, must operate with output current and voltage regulation, and present a high-voltage conversion ratio. To achieve such features, this paper proposes a novel integrated Boost–Zeta converter. To avoid a complex modeling and control, we propose a disaggregation concept for this. Experimental results are presented for the purpose of operating the converter and also for the operation of the system. [ABSTRACT FROM PUBLISHER]

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]

This paper presents a novel interleaved high-conversion-ratio bidirectional dc–dc converter based on switched capacitors and coupled inductors. Series-connected switched capacitor and inductor cells were used to increase the voltage conversion ratio, reduce voltage stresses on power switches, realize soft-charging/discharging of switched capacitors, and achieve autocurrent-sharing in parallel inductors. The interleaved structure combined with switched capacitors was adopted to reduce current ripple at the side having lower voltage, thus enabling applications that require high power levels. In this paper, we first review the status of high-voltage-ratio bidirectional dc–dc converters. Then, the evolution of the proposed extensible topologies and the steady-state operating principle under the inductor current continuous conduction mode is presented. Finally, the performance and features such as voltage gain, voltage and current stress, and the autocurrent-sharing mechanism that are realized by switched capacitors are verified; the optimal design of coupled-inductors, switched-capacitors, and the chip size of switches are given. A specific design of the driving circuit that facilitates actual applications is described. A 1-kW prototype converter, employing a hybrid configuration of SiC and Si mosfets, was constructed to verify the theoretical analysis, and achieved an optimal compromise between conversion efficiency and low cost. [ABSTRACT FROM AUTHOR]

This paper presents a modular multilevel series/parallel converter (MMSPC) with intermodule switched-inductor power transfer. The switched-inductor voltage conversion feature allows controllable and efficient transfer of energy between modules with nonnegligible voltage difference, providing both step-down and step-up functionalities. Thus, this converter can accurately control and rapidly adjust the voltage of each module to generate an ac output voltage waveform with a controllable number of levels, increasing the quality of the output. Moreover, the intrinsic dc–dc conversion feature can generate a dc controllable output voltage and enable new applications. In this text, we specifically demonstrate how the flexibility of obtaining both ac and dc output with the same setup renders the topology promising for battery energy storage systems and dc microgrid applications. Experimental results validate the topology and concept of an MMSPC with intrinsic switched-inductor conversion. [ABSTRACT FROM AUTHOR]

Charge equalization for a series-connected battery string is necessary to enhance usage life and performance of cells. In this paper, an isolated bidirectional dc–dc converter with quasi-resonant zero-voltage switching (ZVS) is proposed for centralized charge equalization system. Through the quasi-resonant operation, the proposed converter can achieve ZVS operations in both boost and buck modes, which decreases switching losses and improves the efficiency. The energy in leakage inductance is released to output side in the boost mode and recycled to the input side in the buck mode, which eliminates the voltage spike. Moreover, the proposed converter has fewer components than existing converters used in the centralized charge equalization system. The operating principle and theoretical derivation of the proposed converter are presented. The ZVS implementations and conditions are analyzed and illustrated in detail. Finally, the experiments using a 7.2 Ah battery string of 13 cells are conducted. The results verify the validity of the proposed converter and show that the equalizer achieves good performance in terms of equalizing speed and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid switched-capacitor/switched-quasi-Z-source bidirectional dc–dc converter is proposed for electric vehicles (EVs) with hybrid energy sources, which has a wide voltage gain range in the bidirectional energy flows. Compared with the traditional quasi-Z-source bidirectional dc–dc converter, the proposed converter only changes the position of the main power switch and employs a switched-capacitor cell at the output of the high-voltage side. Therefore, the advantages of the wide voltage gain range and the lower voltage stresses across the power switches can be achieved. The operating principle, the voltage and current stresses across the power switches, and the comparisons with other converters are analyzed in detail. Furthermore, the parameter design of the main components, the dynamic modeling analysis, and the voltage control scheme are also presented. Finally, the experimental results obtained from a 400 W prototype validate the characteristics and the theoretical analysis of the proposed converter. [ABSTRACT FROM AUTHOR]

The renewable generations (RGs) are conventionally interfaced with the utility grid through battery energy storage systems (BESS). In this cascaded configuration of the grid-connected inverter, battery, and RG, the power of the battery is passively governed by the power difference between the RG and the grid. This compromises the state-of-charge (SoC) control of the battery and increases the storage capacity. To address this issue, a hybrid electric spring (HES), which is integrated with the RG and noncritical load (NCL), is proposed in this paper for the grid-tied power control and reduction of battery storage capacity in ac microgrids. Such an integrated configuration enables a flexible control of the power flow among battery, NCL, and grid. On top of that, the proposed HES can achieve an extended operating region of grid-tied power control compared with the conventional BESS and the existing electric springs. The operating principle, steady-state analysis, and control design of the HES are discussed. The functions of the grid-tied power control and battery SoC control are verified experimentally and through simulations. [ABSTRACT FROM AUTHOR]

A simple buck–boost LED driver suitable for battery operated applications with limited input voltage level is presented in this paper. Soft switching performance is provided for the main switch via a resonant circuit to improve the converter efficiency. The incorporated auxiliary switch also performs under zero voltage switching condition. Both power switches can be driven with a simple gate drive circuit, so, the additional switch does not add any driving complexity. In addition, only one magnetic element is utilized in the proposed LED driver which contributes to circuit simplicity and lower weight and size. Also, all diodes turn off at zero current switching which eliminates the reverse recovery losses and improves efficiency. A laboratory prototype converting 12 V input voltage to 32 V output operating at 26 W output power is implemented and tested to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

Voltages of series-connected batteries gradually become imbalanced due to nonuniformity in terms of not only battery characteristics but also self-discharge rate that is significantly dependent on temperature. In large-scale energy storage systems, a large temperature gradient is very likely because of its huge geometry, and therefore, equalizers capable of relatively large equalization currents would be necessary to eliminate voltage imbalance originating from uneven temperature distribution. A two-switch string-to-battery voltage equalizer using a half-bridge converter with multistacked current doublers (MSCDs) is proposed for series-connected batteries in this paper. The proposed equalizer is capable of providing relatively large equalization currents without increasing ripple currents thanks to the interleaved operation of the MSCDs. Fundamental operational analysis for a discontinuous conduction mode, in which currents in the equalizer can be limited to desired levels without feedback control, is performed. The experimental results of equalization tests performed for four supercapacitor modules and lithium-ion batteries connected in series demonstrated the equalization performance of the proposed equalizer. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems containing a rechargeable battery as an energy buffer require multiple dc–dc converters for PV panel control and battery regulation, and hence, they are prone to be complex and costly. To simplify the system by reducing the number of converters, this paper proposes the nonisolated switched capacitor converter (SCC)-based multiport converter (SC-MPC) for standalone PV systems. The proposed SC-MPC can be derived by integrating a bidirectional pulsewidth modulation (PWM) converter, series-resonant converter (SRC), and an SCC with sharing switches. PWM and pulse frequency modulation (PFM) controls are employed for the PWM converter and SRC, respectively, to regulate either a battery voltage, output voltage, or input power from a PV panel, depending on power balance among the input, battery, and load. The 150-W prototype was built for an experimental verification, and the results demonstrated the output voltage could be regulated independently on the battery voltage or input port of PV panels. [ABSTRACT FROM AUTHOR]

This paper details the design and implementation of an efficient 4-kW bidirectional converter with a wide load range, based on a three-phase LCC resonant converter operated in a continuous conduction model, which has a number of advantages pertaining to a bidirectional power supply. The voltage boost-up function yields a high voltage gain without increasing the transformer turn ratio. The high switching frequency, which is achievable by using the soft-switching condition and multiphase operation, decreases the output ripple and helps minimize the size of the output filter, as the requirement for a filter changes after the power flow. Moreover, this reduction in the size of the filters yields economic advantages. In addition, because of the synchronous rectifier operation employed during switching, the conduction loss in the rectifier diode of the proposed converter is low. The direction of the output power can be changed easily, using phase control. The implemented power converter is connected to a 320-V rated generator on one side and 28-V lead-acid batteries on the other side. The functionality of the proposed converter is verified in experiments. We confirmed the high performance of the developed converter in terms of efficiency (92.2%), operable load range (0–12.5 A in step-up, and 0–142 A in step-down), and voltage ripple (0.05%). [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]

A dual active bridge (DAB) converter promises high power density. The highest power transfer can be achieved by phase shift modulation inside the zero-voltage switching boundaries. This paper analyzes the transients of DAB commutation. Although commutation has been previously analyzed for DAB with the linear turn-off snubbers, in today's industries, the output capacitors of the switches are utilized as the snubberless approach. The presence of these time-variant capacitors leads to nonlinear equations. This paper applies a piecewise linear model for analyzing the commutation of the ac-link current into the switches. The study is inspired by practical experiments, and the results are experimentally verified. [ABSTRACT FROM PUBLISHER]

This paper presents the analysis and design of a novel technique that allows the conventional series resonant dc/dc converter (SRC) to work as a step-up and step-down converter. This is useful in bidirectional dc/dc converters where one port is attached to a fixed voltage dc line, e.g., a 360-V dc line, and the other port is attached to an energy storage device such as a bank of supercapacitors or batteries. Every converter that works in this scenario requires step-up and step-down modes to transfer energy from one port to the other. The paper presents the SRC as an alternative to the well-known dual active bridge (DAB). The dc analysis is detailed to demonstrate the step-up capability. In addition, the ac analysis is presented. Experimental results from a 6-kW prototype validate the theoretical analysis. The results indicate that this technique achieves better efficiency compared to the phase-shift DAB in a wide power range, from heavy to light loads. The main reason for this is that the converter works with smaller currents than the DAB at light loads. [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]

Among various active cell balancing circuits, a switched capacitor circuit is promising because it can be implemented with low cost and small size. However, when the switched capacitor is applied in the lithium-ion battery, cell balancing speed is generally slow when the number of batteries is high. Therefore, this paper proposes the chain structure of the switched capacitor to increase balancing speed, particularly among outer cells. In this paper, the cell balancing principle of the conventional switched capacitor is explained, and the reason why slow cell balancing of the switched capacitor is shown in the lithium-ion battery is analyzed. To improve cell balancing speed, two circuits with chain structure are proposed. The balancing performance of the proposed circuits is confirmed by computer simulation, and a comparison between conventional and proposed circuits is presented. The theoretical analysis on the cell balancing speed of conventional structures and the proposed chain structure is also shown in this paper. Experimental tests were carried out to verify the validity of the proposed structures, and the experimental results show an improved balancing performance of the proposed circuit. [ABSTRACT FROM PUBLISHER]

The battery energy-stored quasi-Z-source (BES-qZS)-based photovoltaic (PV) power generation system combines advantages of the qZS inverter and the battery energy storage system. However, the second-harmonic ( \text2\omega ) power ripple degrades the system's performance and affects the system's design. An accurate model to analyze the \text2\omega ripple is very important. The existing models did not consider the battery, or assumed a symmetric qZS network with $L_{{1}}= L_{{2}}$ and $C_{{1}}= C_{{2}}$, which limits the design freedom and causes oversized impedance parameters. This paper proposes a comprehensive model for the single-phase BES-qZS-PV inverter system, where the battery is considered and there is no restriction of $L_{{1}}= L_{{2}}$ and $C_{{1}}= C_{{2}}$ . Based on the built model, a BES-qZS impedance design method is proposed to mitigate the \text2\omega ripple with asymmetric qZS network. Simulation and experimental results verify the proposed \text2\omega ripple model and impedance design method. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid bidirectional dc–dc converter is presented, which is a combination of a switched-capacitor converter and an inductor-based converter with low component counts. The input current ripple and peak charging current are small with the help of the inductor. The proposed converter is applicable in the battery charge/discharge systems, such as the distributed renewable energy systems, battery equalizer, auxiliary power supplies, traction drive system, and dual-voltage automotive systems based in new electrical architecture concept, where common ground is not required and within the voltage-gain range of 2–6. A comprehensive analysis of the steady-state operation, small-signal model, and component stress is given. The comparison with an alternative topology shows the advantages of low component counts, low total capacitor voltage stress, low inductor current, and low total active switch stress for the 42/14 V voltage level. A 42/14 V prototype rated at 20–120 W with a peak efficiency of 97.8% in boost mode and 97.62% in buck mode was built to verify the analysis. [ABSTRACT FROM AUTHOR]

To overcome the problem that the balancing performance of existing switched-capacitor (SC) cell balancing systems drops along with the increase in the number of series-connected battery cells, a novel SC cell balancing circuit is presented in this paper. The same as other SC balancing systems, only a pair of complementary square-wave signals is required to control the proposed circuit. With resonant SC design, all switches employed in the proposed balancing circuit operate under zero-current switching. The equivalent model is derived to reveal the balancing performance of the proposed balancing circuit. The system feasibility and theoretical analysis are verified by both of simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a multistage nonisolated high voltage conversion ratio (VCR) bidirectional dc–dc converter is proposed. The VCR is n times of the conventional buck/boost converter using only n+ \text2 switches. All the switches can achieve full-range zero voltage switching (ZVS) despite the power flow direction. The operating principle, ZVS condition, and design considerations of a four-stage topology are analyzed in detail. In addition, an improved dynamic switching frequency modulation is proposed to reduce the power loss. Analyses and comparisons between the conventional constant frequency and variable frequency control are made to show the effectiveness. A 500-W experimental prototype interfacing 20–30 V with 270 V is fabricated to verify the performance of the proposed converter and control strategy. [ABSTRACT FROM AUTHOR]

A new zero-voltage switching full-bridge dc–dc converter for battery charging is proposed in this paper. The proposed isolated dc–dc converter is used for the dc–dc conversion stage of the electric vehicle charger. The primary switches in dc–dc converter turn-on at zero voltage over the battery-charging range with the help of passive auxiliary circuit. The diode clamping circuit on the primary side minimizes the severity of voltage spikes across the secondary rectifier diodes, which are commonly present in conventional full-bridge dc–dc converters. The main switches are controlled with an asymmetrical pulse-width modulation (APWM) technique resulting in higher efficiency. APWM reduces the current stress of the main switches and the circulating losses compared with the conventional phase-shift modulation method by controlling the auxiliary inductor current over the entire operating range of the proposed converter. The steady-state analysis of auxiliary circuit and its design considerations are discussed in detail. A 100-kHz 1.2-kW full-bridge dc–dc converter prototype is developed. The experimental results are presented to validate the analysis and efficiency of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper presents a multiobjective real-time controller for a modular multilevel converter capable of parallel module connectivity, the so-called modular multilevel series parallel converter (MMSPC). The MMSPC topology allows the batteries to be dynamically rewired in various series–parallel configurations, generating a wide range of output voltage levels. The novel control method parallelizes the modules to balance their voltages without the need for individual module voltage monitoring. Additionally, the controller optimizes across the large number of feasible system configurations to minimize switching and conduction losses. Finally, the controller efficiently encodes the system configuration with module interconnection states rather than the module switch states, which substantially simplifies control. Furthermore, this work experimentally validates the MMSPC topology and concept. In the prototype, the parallel mode reduced the system losses at 5 kW output power by 18% and 24% for load power factors of 1.0 and 0.8, respectively. Sensorless balancing via parallelization maintained well-matched module voltages (standard deviation = 0.045 V) over a 5-h battery discharge with highly variable load current. The reduced conduction losses and simple balancing capability of the MMSPC can enable new applications at medium and low voltages that benefit from its high-quality output, elimination of filtering magnetics, fast response, and modularity. [ABSTRACT FROM AUTHOR]

In this paper, a bidirectional battery charger is proposed for grid-to-vehicle, vehicle-to-grid, and vehicle-to-home operations of electric vehicles. The proposed charger adopts sinusoidal charging to eliminate the use of electrolytic capacitors. A nonregulating series resonant converter is employed for isolation, thereby minimizing the ratings of the components and achieving zero-current switching turn on and off of switches. Meanwhile, an ac–dc converter is employed to control each mode and their mode changes, making the whole control scheme simple and the mode changes seamless. A 3.3-kW prototype was built in the laboratory to validate the proposed concept. Our experimental results demonstrate that the proposed charger has high efficiency and can seamlessly switch between the three operation modes. [ABSTRACT FROM AUTHOR]

A series of switched-capacitor (SC) cell balancing circuits is proposed for rechargeable energy storage devices like battery and supercapacitor strings in this paper. Taking a basic SC-based cell balancing unit as an equivalent resistor, the behavioral models of the proposed cell balancing circuits are developed to evaluate their balancing performance. Comparing with existing SC-based cell balancing circuits, the main advantage of the proposed circuits is that their balancing speed is independent of both of the number of battery cells and initial mismatch distribution of cell voltages. In order to improve the operation performance of SC-based cell balancing circuits in the respect of minimizing the equivalent resistance, optimizing methodologies of circuit parameters are introduced by referring the concepts of slow switching limit and fast switching limit as well as inductive switching limit of SC power converters. Simulation and experimental results are provided to verify the feasibility of the proposed cell balancing circuits. [ABSTRACT FROM AUTHOR]

In the integrated reconfigurable converter (IRC) topology for high-voltage series-connected battery module systems, the converter can be reconfigured into a range of operating modes: “feeding a load” mode, “battery modules balancing” mode, “regenerative” mode, “charging” mode, and “backup” mode. In most battery applications, a battery-balancing system operates while another converter is used as a controllable power interface between the battery system and a load. However, during the conventional IRC operation, the “battery modules balancing” and “feeding a load” modes cannot be operated simultaneously. In this paper, a new balancing scheme is proposed that allows balancing the battery modules while they are powering the load. The proposed balancing strategy is able to distribute different amount of load between the battery modules based on their state of charge (SOC). When the load is disconnected, the battery modules can be still balanced using the conventional “battery modules balancing” mode. A scaled down prototype of the IRC is implemented with three series-connected battery modules. Experimental results are provided to verify the viability of the proposed balancing method. [ABSTRACT FROM AUTHOR]

This paper evaluates the performance of modular multilevel converters with integrated battery cells when used as traction drives for battery electric vehicles. In this topology, individual battery cells are connected to the dc link of the converter submodules, allowing the highest flexibility for the discharge and recharge. The traditional battery management system of battery electric vehicles is replaced by the control of the converter, which individually balances all the cells. The performance of the converter as a traction drive is assessed in terms of torque–speed characteristic and power loss for the full frequency range, including field weakening. Conduction and switching losses for the modular multilevel converter are calculated using a simplified model, based on the datasheet of power devices. The performance of the modular multilevel converter is then compared with a traditional two-level converter. The loss model of the modular multilevel converter is finally validated by experimental tests on a small-scale prototype of traction drive. [ABSTRACT FROM PUBLISHER]

In LLC-based onboard battery charging architectures used in plug-in electric vehicles (PEV), the dc link voltage can be actively regulated to follow the battery pack voltage so that the LLC converter can operate in proximity of resonant frequency and achieve high efficiencies over the wide range of battery pack voltage. However, conventional boost-type power factor correction (PFC) converters are unable to provide ultrawide dc link voltages since their output voltages should always be larger than their input voltages. This paper proposes a Silicon Carbide (SiC)-based onboard PEV charger using single-ended primary-inductor converter (SEPIC) PFC converter followed by an isolated LLC resonant converter. With the proposed charger architecture, the SEPIC PFC converter is able to provide an ultrawide range for dc link voltage, and consequently enhance the efficiency of the LLC stage by ensuring operation in proximity of resonant frequency. A 1-kW SiC-based prototype is designed to validate the proposed idea. The experimental result shows that the SEPIC PFC converter achieves unity power factor, 2.72% total harmonic distortion, and 95.3% peak conversion efficiency. The LLC converter achieves 97.1% peak efficiency and always demonstrates a very high efficiency across the ultrawide dc-link voltage range. The overall efficiency of the charger is 88.5% to 93.5% from 20% of the rated load to full load. [ABSTRACT FROM AUTHOR]

In conventional parallel hybrid energy storage systems (HESSs), there are usually two cascaded converters active when transferring energy between its energy storage systems (ESSs) that result in the overall efficiency drop. Moreover, the dc-link capacitor has to be oversized to limit the voltage ripple during simultaneous energy exchange between the ESSs and load feeding. The integrated reconfigurable configuration for HESSs proposed in this paper allows direct energy transfer between the ESSs by using only a single converter and bypassing the dc link. This reduces the stress on the dc link, reduces the dc-link capacitor size, and improves the efficiency. The proposed configuration can be reconfigured to operate in different operating modes: “feeding a load” mode, “regenerative” mode, “energy exchange” mode, “energy exchange and feeding a load” mode, “balancing” mode, “charging” mode, and “backup” mode. To control the proposed HESS, a battery peak power limiting method is used to allocate the power components between the ESSs. The operating principle of the proposed configuration and its different modes are explained and experimentally verified. [ABSTRACT FROM PUBLISHER]

Multiterminal converters eliminate using several single-input-single-output converters and simplify their topologies and reduce their cost. In this paper, a new family of multi-input converters based on three switches leg is introduced. Inputs of the proposed converters are similar and they are topologically interchangeable and have boost or buck operation modes. The proposed converter has one output that operates as an inverter. Here, all operating modes of the proposed converters and their effects on each other are investigated, in details. Also, an appropriate switching technique for the converters is given. A detailed comparison between conventional and proposed two-input converters is also presented. A two-input, one-output prototype converter has been implemented to validate the given analyses and to verify the proposed converter's performance. The experimental results are in good agreement with the theoretical and simulated analyses. [ABSTRACT FROM AUTHOR]

High-voltage-gain and wide-input-range dc–dc converters are widely used in various electronics and industrial products such as portable devices, telecommunication, automotive, and aerospace systems. The two-stage converter is a widely adopted architecture for such applications, and it is proven to have a higher efficiency as compared with that of the single-stage converter. This paper presents a modular-cell-based morphing switched-capacitor (SC) converter for application as a front-end converter of the two-stage converter. The conversion ratio of this converter is flexible and variable and can be freely extended by increasing more SC modules. The varying conversion ratio is achieved through the morphing of the converter's structure corresponding to the amplitude of the input voltage. This converter is light and compact, and is highly efficient over a very wide range of input voltage and load conditions. Experimental work on a 25-W, 6–30-V input, 3.5–8.5-V output prototype, is performed. For a single SC module, the efficiency over the entire input voltage range is higher than 98%. Applied into the two-stage converter, the overall efficiency achievable over the entire operating range is 80% including the driver's loss. [ABSTRACT FROM AUTHOR]

This paper introduces a novel power management architecture (PMA) and its on-chip implementation, designed for battery-powered portable applications. Compared to the conventional two-stage PMA, consisting of a front-end inductive converter followed by a set of point-of-load buck converters, the presented PMA has drastically improved power density. The new architecture, named multioutput switched-capacitor convertor–differential-input buck (MSC–DB) convertor, is based on a novel hybrid converter topology that combines a fixed ratio MSC and a set of DB converters, to achieve low volume and high power processing efficiency. The front-end switched-capacitor stage has a higher power density than the conventionally used inductive converters. The downstream DB converters enable tight output voltage regulation, and allow for up to four times reduction of output filter inductors without the need for increasing switching frequency, hence limiting switching losses and improving the efficiency of the system. Furthermore, the new PMA is able to balance the state-of-charge of the input battery cells, a feature not existing in conventional systems. The PMA architecture is implemented both as a discrete prototype and as an application-specific integrated circuit (IC) module. The on-chip implemented architecture is fabricated in a standard 0.13-μm CMOS process and operates at 9.3-MHz switching frequency. Experimental comparisons with a conventional two-cell battery input architecture, providing 15 W of total power in three different voltage outputs, demonstrate up to two times reduction in the inductances of the downstream converter stages and more than two times reduction in losses, equivalent to the improvement of the power processing efficiency of a 12%. Moreover, the fabricated IC module is copackaged with low-profile thin-film inductors to demonstrate the effectiveness of the introduced architecture in reducing the volume of PMAs for portable applications. [ABSTRACT FROM AUTHOR]

This paper presents a novel integrated magnetic three-port converter (IMTPC) with high power density and all three ports’ current ripple cancellation. The proposed IMTPC can interface one PV port, one bidirectional battery port, and one load port of the PV-battery dc power system. Only two high power magnetic devices are needed in an IMTPC for realizing power conversion, ripple cancellation, and switch driver simultaneously. Three extra capacitors were added to achieve three ports’ current ripple cancellation. Therefore, the port of the IMTPC will always in continuous-conduction mode with “zero current ripple,” thus, size of passive filter can be reduced and accuracy of maximum power point tracking can be improved. Meanwhile, simple driving of the high-side switch can be realized by integrated magnetic winding, which is responsible for MOSFET driver's voltage level shift. The using of the integrated magnetic technique not only performs aforementioned advantages but also shows great potential for reducing the weight and volume of the dc–dc converter. Finally, experimental verifications are given to illustrate the feasibility and effectiveness of the proposed topology and control method. [ABSTRACT FROM PUBLISHER]

With the increasing popularity of electric vehicles, there is an urgent demand to shorten the charging time, so the development of high-power charging stations with fast chargers is necessary to alleviate range anxiety for drivers. The charging station based on the neutral-point-clamped (NPC) converter can bring many merits, but it has unbalanced power problems in the bipolar dc bus. To solve this issue, comprehensive dc power balance management (PBM) in conjunction with high-power three-level dc–dc converter based fast charger is proposed in this paper. The active dc power balance management (APBM) is proposed to assist the central NPC converter in balancing power so that the additional balancing circuit is eliminated; while the passive dc power balance management (PPBM) is proposed to eliminate the fluctuating neutral-point currents and to ensure the balanced operation of fast chargers. The principles of APBM and PPBM are researched, the efficient integration between them is studied, and the overall control scheme for the fast charger is proposed. The power balance limits of APBM are explored, while the circulating currents of PPBM are analyzed. Simulation and experimental results are presented to verify the effectiveness of the proposed fast charger with PBM functions. [ABSTRACT FROM PUBLISHER]

Manufacturers want high power density for the on-board battery chargers of plug-in hybrid electric vehicles. Wide bandgap devices can be used to shrink other passive components by increasing the switching frequency, but the bulk dc link capacitor of the ac–dc power factor correction stage, becomes one of the major barriers to higher power density, because its volume depends on the ripple power at the double line frequency in a dc current charging system. However, if this double line frequency ripple flows into the battery, the dc link capacitance can be significantly reduced. This charging scheme, named as sinusoidal charging in this paper, is analyzed and implemented based on a two-stage battery charging system, which is comprised of one full bridge ac–dc stage and one dual active bridge dc–dc stage. We further find that converter loss causes ripple power imbalance and bigger dc link capacitance. Therefore, the impact of converter loss on the ripple power balance is analyzed, and a feedback control on the dc link voltage ripple is proposed based on this analysis in order to further reduce the dc link capacitance. The effectiveness of the proposed solutions is verified in both Si-based and GaN-based charging systems. [ABSTRACT FROM AUTHOR]