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This article proposes a novel control for the multiple-input, single-inductor, multiple-output dc–dc converters. It is digitally and discretely implemented, which can have an outstanding performance in low-power applications so that at the power of 10 mW, it has an efficiency of 92.5%. Conventionally, in this power range, an attempt is made to take advantage of an analog design that is flexible. Thus, a fully programmable (software designed) converter with digital design using a microcontroller is in great demand. This converter design basis is to deploy the microcontroller's central processing unit (CPU) as little as possible. Also, it only turns on the CPU when necessary to be employed in low-power, portable systems, e.g., energy-harvesting technologies. Therefore, construction costs are significantly reduced. Depending on the energy level of the inputs, they can simultaneously be utilized to charge the outputs. This article uses stability analysis, time-multiplexing control method, and variable-frequency pulsewidth modulation in the proposed control design. Each output can be charged with different frequencies according to its load, and the maximum switching frequency is equal to 10 kHz. Also, the proposed technique for zero-current switching has been digitally implemented; it can be utilized to determine the optimal value of the inductor discharge duty cycle based on the inductor's left-side voltage. Comparative simulations and experimental results reveal the superiority and practicality of the proposed approach. [ABSTRACT FROM AUTHOR]

Zero voltage switching (ZVS) of power semiconductor devices is an effective way to improve the efficiency and power density of the power electronic converters with extremely high switching frequency. This article aims to analyze and realize the true full-range ZVS operation of a totem-pole power factor correction circuit. The available ZVS control strategies are investigated, and the conditions for the realization of full-range ZVS operation are analyzed. It is revealed that the existed control strategies did not consider the influence of the dead-time, resulting in the failure of ZVS operation in some input voltage ranges. To address this issue, two feasible retrofitted control strategies, namely the turn-off current optimization control and the adaptive dead-time control, are proposed. The merits and drawbacks of the two control strategies are carefully analyzed and compared. It is found that the adaptive dead-time control can not only achieve the true full range ZVS but also significantly reduce the loss of the freewheeling diodes. The design consideration of key parameters is discussed. Finally, the feasibility of the proposed control and the correctness of the theoretical analyses are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

This article proposes a new voltage-balancing dual-active-bridge (VB-DAB) converter for the bipolar dc distribution system. The proposed converter comprises the same components as those of the conventional DAB converter, and it integrates functions of a VB without additional components. The proposed converter transmits power using the same principle and control as the conventional DAB converter. Furthermore, it regulates both output voltages equally and redistributes the unbalanced load current. Therefore, the proposed converter neither requires additional components nor results in losses by them. Consequently, it can achieve high efficiency and high power density. The effectiveness of the proposed converter is verified by 3-kW prototypes with a 380-V input and ±190-V outputs conditions. [ABSTRACT FROM AUTHOR]

In switched-capacitor (SC) based multilevel inverters (MLIs), capacitors are usually replenished by a dc voltage source or other capacitors, inrush charging current are found at switching instants. In order to solve this issue, this article presents a new type of step-up MLIs, which is implemented by using a front-side quasi-Z-source unit to feed SC-based multilevel circuits. As a result, the charging current variation of capacitors is effectively limited by the quasi-Z-source impedance. Moreover, the charging voltage can be regulated by controlling the duty ratio of shoot-through states of the quasi-Z-source unit, and the total voltage gain of the new MLI is enhanced as both SC and quasi-Z-source units have boost capability. Structurally, the two units share a common switch network so that the new MLI has simple structure. Topologies for single- and three-phase configurations, operation, and modulation, as well as the parameter design are analyzed in detail. Finally, the feasibility of the new MLI is verified experimentally by a downscale three-phase prototype. [ABSTRACT FROM AUTHOR]

Three-level boost dc–dc converters present several advantages in comparison with conventional boost converters, such as reduced switching losses, lower voltage ratings for the diodes and switches, and smaller size of reactive components. The topology requires three voltage levels at the output, therefore, replacing the output capacitor of the traditional boost converter with two capacitors and a midpoint. However, due to component tolerances and/or current flowing through the midpoint, output capacitors voltages become unbalanced, leading to converter malfunctioning or destruction. To overcome this issue, an exact feedback linearization control strategy is proposed, for which an implementation with minimum sensors is obtained. Analyses of its performance at different input voltages and of its robustness against component variations are included. Simulation results are provided, showing a comparison of the proposal with a conventional control strategy and its steady-state performance with nonlinear loads. The proposed control strategy was implemented in a low-cost microcontroller unit and, experimental verification is included. [ABSTRACT FROM AUTHOR]

Slow load transient performance, potential cross-regulation, and low efficiency are the major drawbacks for pseudocontinuous conduction mode single-inductor dual-output (SIDO) dc–dc converters. To overcome these drawbacks, this article proposes a voltage-ripple (VR)-based dynamic freewheeling (DF) control technique for hybrid conduction mode (HCM) SIDO buck converter. With the employment of VR controller, the proposed control technique improves the load transient performance significantly. As the fast recovery during load transition, the cross-regulation is minimized. Additionally, due to the DF controller, the freewheel current value automatically updates in each switching period, which can improve the efficiency of the HCM SIDO buck converter, especially under the light load conditions. Finally, the proposed converter has been verified through experimental results. The transient response time on 0.5 A load change takes only 1–2 switching periods. No observable cross- regulation is found and maximum efficiency of 92.03% is achieved. Finally, the experimental waveforms are presented to verify the theoretical research. [ABSTRACT FROM AUTHOR]

A dual-transformer-based hybrid dual active bridge (DAB) converter for plug-in electric vehicle charging to cope with wide load voltages is introduced in this article. The control degrees of freedom are extended by splitting the leg and transformer of the conventional DAB converter (CDABC) in two parts. Based on the numerical analysis, the full-domain four-variable closed-form optimal trajectories targeting at the minimum root mean square value of the leakage inductor current is attainted, and the unified-segmental control strategy is proposed to handle the working modes shifting without the current inrush. As a result, the conduction losses and switching losses can be significantly reduced in boost mode compared to CDABC. The discussed converter and control strategy are verified by a 1.0-kW prototype. [ABSTRACT FROM AUTHOR]

In this article, a single-switch continuous input current (CIC) buck–boost converter with noninverted output voltage is proposed. The proposed converter utilizes capacitor and inductor along with three diodes in conjunction with a quadratic boost converter to adopt its CIC feature. The features of high voltage gain, single active power switch, less ripple CIC, and noninverted output voltage make the proposed converter suitable for renewable and industrial applications. In addition, it provides a wide operating voltage gain with optimum component count, which is higher than the conventional buck–boost converter. Furthermore, it has low voltage stress across the power switch with comparable converters. To elevate the importance of the proposed converter, a detailed comparison analysis has been carried out considering voltage stress, voltage gain, effectiveness index, and component count. The operating principle and steady-state analysis in continuous conduction mode and discontinuous conduction mode of the proposed converter are discussed in detail. To validate the theoretical analysis and performance of the proposed converter, a prototype has been developed and tested in laboratory. [ABSTRACT FROM AUTHOR]

Hybrid ac/dc off-grid topologies offer the combined advantage of higher energy efficient dc loads, and existing low-cost ac loads. Such budding topologies tender a promising solution for rural electrification when supplied from solar power along with battery backup. The desirable features of such a scheme for catering household appliances are: low semiconductor count, continuous current ports for PV, battery and dc load, low-voltage levels for PV and battery, dc and ac load voltage regulation, maximum power point tracking, battery overcharge and deep-discharge protection, high-voltage boosting sans low-frequency transformer, and reduced power converter stages. The schemes reported in the literature lack one or more of these features. To address this concern, a hybrid ac/dc scheme is proffered. The first stage is formed by a novel three-switch four-port converter, which facilitates most of the aforesaid features required in a hybrid system. The remaining features are obtained using a conventional dc–ac converter, which forms the second stage of the proposed solution. The overall solution is substantiated through comprehensive analysis and experimental demonstrations using a 400 W experimental prototype. [ABSTRACT FROM AUTHOR]

In this article, a power-split-based wireless charging system (WCS) with communication-free coordination control is proposed to combat wide load and coupling variations. By using a magnetic integrated inductor, two power delivery channels are created from a single receiver coil. Large portion of received energy is directly delivered to the load. Small amount of energy is converted by using a low-voltage low-power dc–dc converter to regulate the output voltage or current achieving constant voltage (CV) or constant current (CC) charging operation. This proposal achieves higher power conversion efficiency than the traditional two-stage cascaded converter WCS. Since the dc–dc converter only processes partial power of the WCS system, this proposal reduces the voltage stress of the devices and design difficulty. A communication-free coordination control is applied, which is established by sensing the input current drop caused by the burst operation of the partial-power dc–dc converter. Thus, the CC-CV charging is realized by PWM control at the receiver (Rx) side, and the inverter is regulated with subharmonics control scheme to maintain nearly constant Rx coil current. Simulation results for both high-voltage high-power scenarios and low-voltage low-power (LVLP) scenarios are provided to investigate the operation of the proposed WCS. Finally, experimental results are captured from a 250 W/60–84 V LVLP prototype to validate the feasibility and practicability of proposed concept. [ABSTRACT FROM AUTHOR]

This article presents a current-mode controller for switched-inductor topology to achieve voltage balancing between battery cells or modules in a battery pack while operating at peak efficiency. The presented method yields several advantages and/or eliminates several drawbacks of the existing conventional fixed duty cycle scheme. Among these advantages: 1) the balancing current is well controlled instead of being a function of battery cells’ voltages and system parasitic elements, which might result in exceeding the current ratings of the components, and 2) the balancing current reference is selected such that the balancing circuit operates at its maximum efficiency point and, therefore, yielding lower balancing power losses. This article also presents a battery balancing algorithm for utilization with the presented controller that achieves open circuit voltage balancing, which is a more accurate indicator of state-of-charge compared to terminal voltage. Experimental results obtained from a laboratory prototype of a three-cell battery pack are presented to evaluate the presented current control and balancing method under different modes of operation. [ABSTRACT FROM AUTHOR]

The harmonic suppression performance of active power filter (APF) under model predictive current control is obviously reduced, when the parameter exists a mismatch between the actual value in system and the nominal value adopted in the control. To suppress the influence of parameter mismatching, a model predictive control based on parameter identification with forgetting factor recursive least square (FFRLS) method is proposed for APF. The digital processing procedure of the FFRLS-based APF controller is detailed analyzed and designed. The identification error of inductance between identification value and the actual value is less to 6%, and the total harmonic distortion of grid current is significantly improved, especially a lower value of actual inductance. Simulation and experimental results show that the proposed method can not only effectively eliminate the influence of parameter mismatch on the control, but also result in better steady-state performance while retaining fast dynamic response. [ABSTRACT FROM AUTHOR]

Accurate current sharing is beneficial to realize uniform heat distribution and electrical stresses in multiphase converters. Most of the present current-sharing schemes need many current sensors which increase the cost and decrease the system reliability. To solve this problem, a sensorless current-sharing scheme is proposed to balance the phase currents of multiphase dc–dc boost converters in continuous conduction mode. By converting the inner resistances of inductors and switches to series resistances on the input side, the actual converter model is simplified. Regarding one duty cycle as reference, the relationship between duty cycle and series resistance ratio (SSR) is derived for equal current distribution. After that, two methods are provided to obtain the SSRs. One is based on duty disturbance and the other is based on current measurement. Actually, the phase with largest series resistance is chosen as reference to improve the transient response. Despite phase number, only output and input voltages are measured to achieve output voltage regulation and current balance in the overall control scheme. The validity of proposed scheme is verified on a three-phase dc–dc boost converter. [ABSTRACT FROM AUTHOR]

DC–DC converters with a wide input voltage range have earned numerous daily applications in the industry. An example is power systems for electric vehicles, where $LLC$ converters with remarkable features have also been deployed to provide isolation. It is, therefore, common to find a front buck converter cascaded to a back $LLC$ converter, where their intermediate bus voltage is set low to accommodate the lowest input voltage to the buck converter. Unfortunately, this causes efficiency to drop at a high input voltage. To avoid the drop, a reconfiguring strategy has been proposed to convert the front buck converter from full bridge to half bridge, as its input voltage rises above a specified threshold. Furthermore, to ensure a smooth and fast reconfiguration, a dynamic control method has been proposed to direct the intermediate bus voltage to track a reference trajectory with a lower current surge. Besides, the method employs pulse-shift modulation to keep a stable output voltage and proper control initialization to prevent oscillation during the transition. These favorable features and an overall higher efficiency have subsequently been verified through experimental testing with a wide input voltage range. [ABSTRACT FROM AUTHOR]

In this article, a quasi-two-stage buck-DAB (QBDAB) converter is proposed for improving the performance of the conventional dual active bridge (DAB) solution under a wide voltage range. For the proposed QBDAB converter, the DAB can always work under voltage matching conditions for wide voltage range applications, and the gain is adjusted through the added front-end circuit. The front-end circuit is similar to a buck converter, while only part of the transmission power flows through the circuit, which could also reduce the burden of achieving ZVS of the front-end circuit. Therefore, compared with the traditional two-stage buck-DAB converter solution, the related loss for the buck circuit can be reduced. The working principle, power transfer characteristics, and full load range ZVS design are analyzed deeply in this article. A detailed comparison of the QBDAB and other related combined buck+DAB topologies is also presented. Finally, the effectiveness of the proposed QBDAB is verified through experimental results from a 1kW prototype. [ABSTRACT FROM AUTHOR]

In this article, a three-phase single-stage bidirectional ac–dc converter with low component count is proposed. The single-stage structure is configured by integrating a three-phase ac–dc converter and a three-phase dual active bridge converter. The power factor correction and bidirectional power control are performed by adjusting the modulation index of sinusoidal pulse width modulation (SPWM) and phase-shift angle between the primary and secondary bridges. The low-frequency components generated by SPWM are absorbed by fundamental blocking capacitors connected in series with transformer windings, resulting in true high-frequency isolation. The proposed converter can achieve soft-switching of all switching devices even in continuous conduction mode. A 110 Vac, 3 kW, 100 kHz prototype is implemented to validate the proposed concept and demonstrated 95.34% peak efficiency. [ABSTRACT FROM AUTHOR]

A new state-observer-based current balancing method for Modular Multilevel Converters with Interleaved half-bridge Sub-Modules (ISM-MMC) is presented in this article. The developed observer allows estimating currents through interleaved half-bridge legs in each submodule of ISM-MMC based only on arm current and submodule's capacitor voltage measurements. Then, the interleaved current balancing control uses the estimated currents to reduce the interleaved currents imbalance caused by upstream control actions. This technique minimizes the number of required current sensors in ISM-MMC, thereby reducing the converter's cost, weight, and volume. Capabilities of the proposed sensorless interleaved currents balancing control have been tested against standard parameter tolerances of the composing passive elements. In addition to that, a novel capacitor voltage balancing strategy for MMCs is developed. The new algorithm contains the main advantages of the classical sorting-based capacitor voltage balancing methods while providing an opportunity to decouple two balancing tasks of ISM-MMC, namely capacitor voltage and interleaved legs current balancing. The feasibility of the proposed methods is verified by extensive simulation and experimental tests on a laboratory prototype by the corresponding system response under the output characteristics variation and interleaved current control perturbation. [ABSTRACT FROM AUTHOR]

Input-independent and output-series (IIOS) modular converters are characterized by high step-up ratio and independent maximum power point tracking and can therefore be used to integrate renewable energy into medium voltage dc grids. However, the associated power mismatch can lead to voltage imbalance of the submodules(SMs). At present, the only solution using no extra active switch involves the insertion of an LC-branch-based power balancing unit (PBU) between every two adjacent SMs (the SM and PBU share the switches). However, the considerable peak current of the shared switches threatens the security of the switches and increases the power loss. Therefore, this article considered the peak-current problem. A dual active bridge (DAB) converter was employed as the SM of the IIOS converter. The basis for the large peak current associated with the shared switches was analyzed and a peak current reducing method using the DAB inner-phase-shift control was proposed. The contribution of this article is that the current stress can be reduced and the power efficiency can be increased. A two-SM and 1000-W down-scaled experimental prototype was developed for verification of the theoretical analysis results. The peak currents and efficiencies with and without the proposed method were compared with experimental results. [ABSTRACT FROM AUTHOR]

Cascaded split-source inverter (CSSI) is a single-stage modular multilevel structure. This article proposes the multidimensional pulsewidth modulation (MD-PWM) for this topology. All multilevel modulations are a particular version of this approach. The principles of this geometrical method are based on selecting the optimal points and determining the switching sequences and time intervals. By considering the operational principles of CSSI, this method is modified to accurately control the voltage of dc links, charge inductors with constant duty cycles, control dc and ac sides of cells independently, and reduce the reverse recovery effects of input diodes. MD-PWM, with a low computational burden, can be implemented for CSSI with any number of voltage levels. The output power can be distributed equally or unequally among cells, and both buck and boost operation modes are realized for each cell. Also, this method is extended for the operation of the converter with unequal input sources. For an asymmetric topology with N cells, harmonics are located at multiples of N times switching frequency. Thus, this strategy eliminates low-frequency distortions from the output voltage of asymmetric CSSI. The simulation and experimental results verify the performance and accuracy of the proposed technique and mathematical relations. [ABSTRACT FROM AUTHOR]

Discontinuous conduction mode (DCM) for inverters can lower the size of filter inductors and can realize the soft switching for switches. However, the current stress under the DCM is high. Aiming to solve this problem, this article uses a T-type three-level circuit to construct an LCL-type grid-connected inverter, which introduces the trapezium conduction mode (TPCM) with the zero-voltage switching to lower the current stress when the grid current is large. Both the DCM and the TPCM can work at a fixed switching frequency, but it is difficult to design controllers using the conventional average state model. To address this challenge, this article proposes a charge quantity model (CQM) that is applicable to any inverter topology and conduction mode, where the output charge quantity of the bridge is used as a control variable. The proposed model represents a linear two-order model, which can greatly simplify controller design. Based on the CQM, a direct charge control method working at a fixed switching frequency is developed, which combines a PID regulator and a feedforward controller of the grid voltage. The excellent steady-state and dynamic control performances of the proposed model and control method are verified by simulations and experiments. [ABSTRACT FROM AUTHOR]

In grid-tied photovoltaic (PV) generation systems, intelligent energy management is required to maximize its performance. In this article, a novel three-port energy router with optimized control is proposed for this application. The proposed converter can interface among three ports (PV source, battery, and dc-link) with high integration. The PV panel is connected to the battery through an interleaved boost structure on the primary side. The primary-side PV-battery system and secondary-side dc-link are connected through a dual-active-bridge (DAB) converter. The battery operates as an energy buffer to compensate for the power mismatch due to the intermittent nature of the PV source. According to the daily power profile and intelligent power management between the grid and battery, six operating modes are possible. Optimized control strategies are customized in different operating modes. The maximum-power-point-tracking (MPPT) of the PV panel can be always realized. The zero-voltage-switching (ZVS) condition for all mosfets, reducing circulating current over a wide range, and flexible energy flow among three ports are all taken into considerations in the design. To verify the proposed concept, a 500 W rated prototype is designed. The designed prototype exhibits high efficiency in various operating modes. The experimental results agree well with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Power factor correction (PFC) rectifiers based on the classic boost topology have become widespread owing to their current input features, and can obtain optimal results in terms of power quality. However, several applications require an output dc voltage lower than the ac input voltage. In such cases, two-stage topologies provide lower voltage values at the output, which increases the number of components. Moreover, such topologies tend to incur higher losses and are costly. Therefore, a unidirectional hybrid single-stage single-phase PFC boost rectifier with a switched-capacitor cell and low voltage gain is proposed. Furthermore, the proposed topology has two active switches, and natural balance exists between the voltages of the capacitors. Therefore, an additional control system is not required. The proposed topology was theoretically analyzed and experimentally validated using a 1 kW prototype with two different operational situations: (A) 127 V ac and 100 Vdc; (B) 220 Vac and 200 Vdc, input and output voltages, respectively. The experimental results essentially reveal that the power factor is approximately one, and the total harmonic distortion of the input current is 4.6%. The maximum efficiency achieved was 96.5% in the operational situation (B). [ABSTRACT FROM AUTHOR]

In this article, a detailed analysis, design, and experimental evaluation of a continuous-conduction-mode, pulsewidth modulated, boost-type active soft-switching cell suitable for 1-ph/3-ph universal input voltage power factor correction (PFC) rectifier for on-board charging applications is introduced. The soft-switching cell features zero-voltage switching and simple control. The evaluation of the concept was performed on a 1-ph/3-ph combo 7.2-kW/12.5-kW prototype designed to operate at 230 VRMS 1–ph and 480 VRMS 3-ph line input and deliver 650–750 V output. At full load and 150 kHz switching frequency, the prototype achieves 98.8% efficiency in 3-ph operation and 98% efficiency in 1-ph interleaved operation. The soft-switching PFC concept naturally morphs between an interleaved totem-pole converter for 1-ph ac line voltage and a 3-ph converter for 3-ph ac line voltage. [ABSTRACT FROM AUTHOR]

Interleaved parallel cascaded multilevel technology is an attractive approach for converters to achieve high efficiency, high-power density, and high modularity. In this letter, a novel single-phase interleaved parallel cascaded three-level (IPC-TL) power factor correction (PFC) converter is proposed. It is formed by cascading two interleaved parallel totem-pole PFC cells. The proposed topology exhibits the merits of lower inductance volt-second and inductor current ripples, lower common-mode noise, and lower control cost, compared with the traditional IPC-TL topology. A laboratory-scale experimental prototype is developed to verify the effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

Larger battery packs, an efficient battery management system, highly efficient electromechanical conversion, and fast battery charging are the key factors for extending the drive range of electric vehicles and the expansion of electromobility. We present a novel highly stable modular multilevel powertrain design with a variable dc-bus voltage, active inner battery energy flow control, and reduced filter size. The underlying powertrain design replaces conventional hard-wired batteries by a modular multilevel architecture, thus modularizing the battery pack and increasing the energy efficiency, reducing the output filter size, and providing full control over the output voltage and energy flow of the battery cells. We analyse the large-signal stability of the proposed system and compare it to dc/dc-dc/ac conventional multiconverter powertrains, demonstrating better stability and lower filter requirements. Further, we experimentally evaluate the proposed system structure. In the experimental setup, we achieve stable converter operation with the output filter capacitor reduced by a factor of 24 and the filter inductor reduced by a factor of 17 compared to dc-dc-dc-ac reference system, thereby leading to a significant reduction of system cost, size, and weight. [ABSTRACT FROM AUTHOR]

A voltage balancer remains a good solution of power transfer for bipolar dc grids, which, however, would increase the costs due to its requirement for additional hardware support. In this article, an auxiliary power transfer strategy is proposed by using the inactive motor drives affiliated with the bipolar dc grid. During idle periods of the motor drive, one inverter bridge arm is connected with the bipolar dc grid at their neutral points, allowing bidirectional power transfer between the upper and lower dc-bus sources. The proposed strategy share part of the voltage balancer's power transfer burden without requiring additional hardware and affecting the normal operations of the motor drive. In addition, its effectiveness is verified by experimental results on an interior permanent magnet synchronous motor drive, showing that the power flows among the upper and lower dc-bus power supplies are controlled effectively. Also, the active control of the dc-bus voltages could be achieved by modulation of the phase currents. [ABSTRACT FROM AUTHOR]

Four-switch buck-boost (FSBB) converter features positive output voltage and low voltage stress of power switches. In this article, a pulsewidth modulation plus phase-shift control scheme is proposed to achieve zero-voltage-switching for all the power switches in full input voltage and load range and minimize the inductor current ripple and root mean square (RMS) value. The implementation of the proposed control scheme is given. A prototype of a 500-W FSBB converter is built and tested in the lab, and the experimental results verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In this article, a novel nonisolated multiple input dc-dc converter (MIC) is proposed for all-electric hybrid energy storage systems. The proposed MIC is capable of bidirectional operation in noninverting buck–boost configuration and can accommodate the simultaneous energy transfer from multiple sources of different voltage levels to the dc bus. As compared to counterparts, the proposed MIC utilizes a smaller number of inductors and requires only one bidirectional switch to integrate any extra energy storage. Within the framework, a novel voltage transformation, operation modes, and control method are presented in detail. The performance and key features of operation with varying voltage levels and duty cycles of the proposed MIC are numerically verified through a high-fidelity hardware-in-the-loop platform and experimentally validated on an in-house test rig. [ABSTRACT FROM AUTHOR]

This article presents a multiport dc–dc converter (MPC) with four ports suitable for renewable energy applications. The converter is composed of two boost converters and a switched capacitor. The converter includes a bidirectional buck–boost converter to charge/discharge an energy storage. In the design procedure of the converter, existence of a common ground between the load and input ports, high voltage gain and continuous current of the ports are introduced, which make the converter appropriate for more applications. The converter boosts voltage with high gain in all of its operation modes. In addition, it operates in unbalanced conditions such as different powers and voltage levels of the input sources. According to the used switching strategy, controlling input power of the sources and output voltage is possible. Furthermore, the converter switches between charging and discharging modes automatically. To validate the feasibility and effectiveness of the proposed MPC, a prototype with 250 W nominal power is prepared. The converter boosts 20–400 V in all of the experimented modes. [ABSTRACT FROM AUTHOR]

The instantaneous output power of the two-stage single-phase inverter pulsates at double-line frequency, generating a large amount of second harmonic current (SHC) in the front-end dc-dc converter and input dc source. The SHC is harmful to the system performance. To address the issue, a control strategy based on port-impedance editing, where inductor current feedforward (ICFF) and bus voltage feedforward paths are employed, is proposed to reduce the low frequency ripple in the article. Due to only bandpass filter employed in each feedforward path, the proposed control scheme is relatively easy to be implemented. Under the control strategy, the dc-bus port-impedance of dc-dc converter is increased rapidly at double-line frequency, while staying low impedance for other frequencies. What is more, different ICFF paths are taken into insight to obtain optimized path. Meanwhile, the small signal model of front-end dc-dc converter is established and the design principle of key parameters is provided for the derived control strategy. Furthermore, the dynamic response with bandwidth limitation is also discussed in this article. Finally, a two-stage single-phase inverter prototype was fabricated and tested. The experimental results verify the performance of the proposed strategy with SHC reduction. [ABSTRACT FROM AUTHOR]

The article proposes a new vector analysis based model predictive control (VAMPC) method for multilevel converters with four different switch configurations. It is based on track of an error vector using fundamental state vectors, and can achieve deadbeat control of four switching states multilevel converters with multiple control objectives. Compared with conventional finite control set model predictive control (FCS-MPC) method, VAMPC can achieve excellent spectrum characteristics in the case of a slight increase in computational burden. The VAMPC method is experimentally validated on a 100-kHz GaN-based three-level flying capacitor (FC) converter. Compared with the FCS-MPC, VAMPC leads to significant reduction in steady-state control errors. For example, the inductor current total harmonic distortion of the FC converter is now reduced by more than 60%. [ABSTRACT FROM AUTHOR]

Negative-sequence current is required to be intentionally injected to support the power grid or compensate the imbalanced load in asymmetrical faults utilizing STATCOM. However, the extreme compensation range of negative-sequence current injection becomes complicated when grid voltage becomes asymmetrical. This article presents a novel off-line strategy for negative-sequence current compensation under two typical kinds of asymmetrical grid faults — single-phase voltage drop and double-phase voltage drop, with the following two benefits simultaneously: maximizing negative current compensation capacity; avoiding iterations and reducing computation burdens. In this paper, the mechanism of DC voltage balancing among three phases in STATCOM is analyzed and a new identification method of negative-sequence current compensation range is explored out. To simplify the calculation, this paper takes the ratio of negative-sequence reactive (Iq-) and active (Id-) current as a variable (s). In this way, the relationship between the extreme compensation range, asymmetrical voltage sag depth of power grid h is drawn with MATLAB. Different from the previous iterative method, the off-line identification method is applied to avoid huge iterations. By fitting the curve, the precise ranges of negative-sequence current compensation under different asymmetrical grid faults are approximated as simple polynomials, thus significantly reducing the computation burdens. Simulation and experimental results verify the practicability of the proposed compensation method. [ABSTRACT FROM AUTHOR]

Discontinuous conduction mode is often used in boost power factor correction converter. This article proposes a unified control method to achieve both pulsewidth modulation control and pulse frequency modulation control, which is based on the virtual impedance principle. The control modes can easily be changed by only adjusting one control parameter. Consequently, by comprehensively considering current ripple, switching frequency, and efficiency, the converter can operate flexibly in the situation of variable loads. This article first introduces the operation principle of the proposed unified control method. Then, the operation condition for each control mode is discussed. Besides, the current ripple, the switching frequency, and the power loss are analyzed. Finally, the experimental results of steady-state test and load switching test are presented. And the efficiency of the converter is more than 95% in the range from half load to full load. These experimental results fully verify the effectiveness of the proposed control. [ABSTRACT FROM AUTHOR]

A novel control technique that guarantees a ripple-free output current and voltage of a dc–dc multiphase staked interleaved converter is proposed. The conventional multiphase interleaved converters have been extensively used in various applications. However, ripple cancellation in these converters solely depends on the number of phases and can only be achieved at specific duty cycles. On the other hand, wide-range and ripple-free output are important paramount features for many modern applications. Therefore, the presented converter aims to combine the advantages of both the multiphase interleaved and the stacked converters into a single-unit converter suitable for high-power applications. Ripple-free output current/voltage is always guaranteed regardless of the number of phases and duty cycle values. This feature is accomplished by adding a fractionally-rated phase-leg to the conventional multiphase interleaved converter and modulating it with the proposed control approach. The configurable logic block, a state-of-the-art tool developed by Texas Instruments, is utilized to reduce the hardware size of the entire conversion system while increasing its speed and flexibility. Extensive simulation studies are carried out to confirm the functionality of the proposed control scheme. A laboratory porotype is developed to validate the effectiveness of the proposed control method experimentally. With only a few more components, significant reductions in output ripples are achieved. [ABSTRACT FROM AUTHOR]

With the continuous development of microprocessors, more stringent voltage regulation requirements have been put forward for the voltage regulators (VR) in the transient process. This letter proposes a driving control method for gallium nitride (GaN) devices to improve the transient response of the VR. When the GaN device conducts reverse, its source-drain voltage can be controlled by its gate voltage. During load step-down transient, the reverse conduction voltage of the GaN device is naturally applied across the inductor, which can be utilized to speed up the change rate of the inductor current. As a result, the overshoot of the output voltage can be reduced during load step-down transient. The proposed method does not need to modify the power circuit, and is easy to implement. Finally, the effectiveness of the proposed method is verified by experiments. The results show that the output voltage overshoot is reduced by 55%, and the transition time is shortened by 80% using the proposed method. The results also show that with the same overvoltage, using the proposed method can reduce the output capacitance by 57% and the transition time by 77%, thereby increasing the power density of the VR circuit and saving costs. [ABSTRACT FROM AUTHOR]

The three-phase dual active bridge (3ph-DAB) converter is a promising topology attracting increasing attention. However, because it is limited to symmetrical three-phase bridge control, the conventional single-phase-shift control method (SPS) remains the most common method for 3ph-DAB converter. The obvious shortcomings of SPS control include the soft-switching failure, massive circulating energy, and high root-mean-square (rms) current value at the light load, particularly with large voltage variation-ratio conditions. To overcome these drawbacks, this article proposes a novel asymmetrical phase shift (APS) control strategy. Unlike other optimized modulation schemes, this optimized strategy breaks the symmetrical control rules of three-phase bridges by introducing variable phase-shift angles among three-phase legs. The novel APS control strategy can substantially reduce the current's rms value and extend the soft-switching operation range due to these additional phase-shift angles. Further, the analytical solutions for the optimal phase-shift angles are derived by solving the global optimal condition equations. Analytical solutions, compared with complex numerical solutions derived by other optimized schemes, can be easily adopted in digital implementation and perform well under changing parameter conditions. Finally, experimental results verify the outstanding performance of the proposed modulation strategy. [ABSTRACT FROM AUTHOR]

This article presents a hybrid hysteretic reconfigurable 3-level buck converter for improving load transient response. A reconfigurable 3-level mode operation is proposed to improve the load transient response without the voltage rating issue. The RC feedback network of the hybrid hysteretic control can be adjusted for the optimized transient response. Furthermore, a hysteresis-based quasi-self-balancing scheme, keeping the voltage across the flying capacitor at half the input voltage, is proposed to guarantee stable operation of the proposed converter. Implemented in a 55 nm CMOS, the proposed converter achieves maximum efficiency of 95.1% at an input voltage of 4.2 V, an output voltage of 3.3 V, and a load current of 200 mA. For a load current step of 750 mA, the under/overshoot voltage and settling times are 62/60 mV and 2.48/2.32 μs, respectively. Compared to the conventional 3-level mode operation, the proposed technique improves the under/overshoot voltage and settling time by 2.21/2.22 and 1.78/1.69 times, respectively. [ABSTRACT FROM AUTHOR]

A triple-mode dc-dc converter with wide ranges of input and load for energy harvesting in Internet-of-Things edge nodes is reported. The proposed energy harvester is designed and fabricated in a 0.18- $\mu \text{m}$ CMOS process. It demonstrates MPPT, automatic buck-boost operation, stable operation in proper energy-distribution path based on the changes of load and input source, and efficient energy conversion control with peak efficiency up to 88.7%, with load transient response time of $ < 450~\mu \text{s}$ , a wide input range of 1.2 – 4 V and an output range of 1 – 4 V, as well as a maximum load up to 50 mA. [ABSTRACT FROM AUTHOR]

This article presents an energy-harvesting (EH) interface chip system for triboelectric nanogenerators (TENGs). Despite TENG’s numerous advantages, its high open-circuit voltage and large parasitic capacitance ($C_{T}$) give a considerable burden to design TENG-EH integrated circuits (ICs). In this work, a scalable multi-chip-stacked bias-flip (MCS-BF) technique is proposed to harvest TENG energy with ultra-high extraction voltage, exceeding an LDMOS transistor’s voltage-rating limit (~70 V). Even in multi-chip-stacked structures, the MCS-BF utilizing a series inductor cancels the energy loss caused by $C_{T}$. Furthermore, a practical solution to synchronize chip-to-chip control signals without over-voltage stress is also presented, even when many chips are daisy-chained together. The proposed TENG-EH chips were fabricated in a 0.18- $\mu \text{m}$ BCD process. In experiments with a real wind-TENG, an extremely high extraction voltage of 130 V (195 V) was successfully demonstrated with two (three) MCS-BF chips. Also, a harvested power per TENG area was measured to be $96.4 \mu \text{W}$ /cm2 with a two-chip solution, which is $4\times $ higher than previous state-of-the-art TENG-EH chips. The conversion from rectified input to regulated (battery voltage) output attained a measured peak efficiency of 70.7%. The proposed TENG-EH multi-chip system offers a $3.14\times $ power extraction gain (figure of merit). [ABSTRACT FROM AUTHOR]

This article presents a fully integrated multi-phase (MP) buck converter for on-chip power management units. A peak-and-valley differential sensing (PVDS) scheme based on a flying capacitor is proposed to evenly balance the multiple inductor currents without significant power overhead even under mismatches in inductances, parasitic series resistances, and control-signal skews among phases. In addition, dynamic re-allocation of on-chip capacitors enables an even more optimal frequency response and output ripple based on the number of activated phases. It also improves the chip area efficiency, resulting in a higher power density. The proposed DLL-based MP clock generation provides high granularity in the phase-shedding control to achieve high efficiency over a wide load range. The proposed fully integrated buck converter using six bond-wire inductors (1 nH) was fabricated in a 28-nm CMOS process. The chip running at a frequency of 400 MHz/phase can finely adjust the number of active phases by an integer step ranging from 1 to 6 through sensing a load current. A maximum power density of 1.23 W/mm2 and a peak efficiency of 83.7% were measured. This work achieved an ultra-fast dynamic voltage scaling (DVS) rate of 75 mV/ns. [ABSTRACT FROM AUTHOR]

This article investigates the functional link neural network assisted deadbeat predictive current control for an onboard charger (OBC) of an e-rickshaw with multistep charging capability. This control algorithm is presented for wide load operation of OBC since a multistep charging scheme is introduced to reduce the electricity consumption by OBC in the course of the peak load hours. The presented grid-connected OBC topology has two stages interconnected with the dc link capacitor. The first stage is a front-end converter to regulate the voltage at the dc link capacitor. Moreover, it regulates the power quality within the IEEE-519 standard. Furthermore, a dc–dc converter to regulate the charging current is the second stage of the OBC. Keeping this in view, a bidirectional interleaved isolated single ended primary inductor converter (SEPIC) converter topology is utilized. To analyze the performance of the OBC under distinct operating conditions such as grid voltage variations, an experimental prototype of the bidirectional OBC, is developed. Furthermore, the efficacy of the bidirectional operation of the designed system is analyzed through the vehicle to grid operation. [ABSTRACT FROM AUTHOR]

Unlike VSIs, the single-stage inverters (SSIs) from the family of Z-converters are capable of boosting input dc to a desired ac voltage. The Z-network of these converters consists of a symmetric X-shaped network or a combination of inductors and capacitors. The basic Z-source converter (ZSC), connected in X-shaped fashion is modeled as a fourth-order system. This can be further modeled as a second-order system to reduce the sensor count but this may lead to an unstable system if there is an asymmetry in network parameters. Also, the source current of SSIs contains second-order ripple current (SRC) component, which oscillates at twice the supply frequency and has detrimental effects on sources. To alleviate the above problems, a parametric uncertainty compensation and ripple mitigation (PUCRM) control methodology is proposed. PUCRM control can be used to maintain stability and achieve desired performance during parametric uncertainties in the dc–dc stage and to reduce SRC propagating to the sources while feeding ac loads. PUCRM consists of a nominal dual-loop PI controller, which regulates the SSIs to achieve desired performance and a nonlinear integral sliding mode component that mitigates the uncertainties and ripple component. The proposed method is verified using simulation and experimentation. [ABSTRACT FROM AUTHOR]

Coupled inductor single-input–dual-output (CI-SIDO) converters are promising converters used in the applications that demand multiple voltage supplies due to their high efficiency and small volume. However, this class of converters suffers from poor cross-coupling and cross-regulation issues, which affects the dynamic performance and stability. These issues can be suppressed with peak current mode control because of its faster dynamic response. To design the controller and study dynamic performance, a small-signal model of the system is essential, which consists of a converter model and current modulator model. However, developing the current modulator model for PCM controlled CI-SIDO converters is challenging because it consists of two reference current for two inductor currents each consisting of three slopes. No literature is available that derives a unified model of PCM controlled CI-SIDO converters. Therefore, this article proposes a unified small-signal model for PCM controlled CI-SIDO converters. The proposed model is applicable to three topologies of CI-SIDO converters, i.e., CI-SIDO buck, CI-SIDO boost, CI-SIDO boost and buck converter. The proposed unified model is a useful tool to study the dynamic performances, stability, and design outer controllers. Finally, the accuracy of the proposed unified model is verified by performing simulation and experiment of PCM controlled CI-SIDO converters considering inner-loops closed. [ABSTRACT FROM AUTHOR]

This article introduces a new coupled inductor based dual-input ultra-high step-up dc–dc converter with a high voltage conversion ratio, low voltage stress across semiconductor components, and high efficiency features. The coupled inductor and voltage multiplier circuit (VMC) techniques have been utilized to enhance the voltage gain. The blocking voltages of power switches are clamped by VMC at low values and can be controlled via the turn ratio of the coupled inductors that decreases the voltage rate of power switches and converter's cost. The presented dual-input structure can transfer power to the load from two independent voltage sources. Besides, the inputs and output ports are common ground, which can reduce the electromagnetic interference influences. Operation modes delineation, steady-state analysis, and comparison section are provided for describing the proposed structure performance. Finally, to confirm the effectiveness of the presented topology, experimental waveforms with a 200 W output power at 50 kHz switching frequency are presented. [ABSTRACT FROM AUTHOR]

The lack of uniform production of panels in photovoltaic (PV) systems and snowball effects in fuel cell (FC) systems led us to use a separate dc–dc converter. In addition, in the PV and FC systems, the output voltage is low. Hence, dc–dc boost converters are commonly used in a series connection. Each small unit of a PV or FC operates independently. Therefore, another problem arises in the system that uses the series connection of the converter's output. Owing to the unequal electricity production of the cells, a voltage imbalance occurs at the output terminals. To create voltage balance, a modular structure grounded on a three-level boost converter was investigated. The main objective of this article is to design the control of a modular topology, allowing perfect control of the dc-bus voltage, even with mismatched input powers. The proposed control strategy ensures dynamical properties independent of the operating point, voltage balance, and robust control of the dc output voltage with respect to load perturbations. To ensure the balance of voltages and the control of currents, a sliding mode controller based on indirect synthesis was used. To control the dc–bus voltage, an energy controller is proposed that ensures dynamical performance independent of the operating conditions. The performance in terms of tracking and regulation, as well as its effect on the voltage balance of the output capacitors, was validated through simulations and experimental results. A comparison with a classical proportional integral (PI) approach for controlling the dc-bus voltage was performed. [ABSTRACT FROM AUTHOR]

This article proposes a high-gain transformerless three-port converter (TPC) for standalone photovoltaic (PV) systems. The TPC is designed and developed based on a dual-inductor high-gain two-port converter by utilizing one of the buffer capacitors to derive the third part for PV input. A hybrid pulse-frequency modulation scheme unified with a pulsewidth modulation control strategy is adopted, which realizes the maximum power point tracking control, load voltage regulation, and bidirectional energy flow at the battery port. The proposed TPC offers the unique advantages of high voltage gain, continuous battery port current, reduced power semiconductors, lower voltage stresses, common ground shared by all the ports, low-cost gate driver, and small size of the rear-end inductor. The working principle, steady-state characteristics, small-signal models, and the control method, including design conditions, are comprehensively analyzed. The correctness of the theoretical analysis is verified by developing a 300-W experimental prototype, which shows that the maximum efficiency is 97.7%. [ABSTRACT FROM AUTHOR]

This letter proposes a switched capacitor (SC)-based continuously adjustable modular bidirectional dc–dc converter. The structure of the proposed converter consists of three types of modules, series–parallel SC converter module, regulating module, and resonant SC converters module. A basic configuration of three modules working in buck operating mode is analyzed in detail. The boost mode operation is symmetrical to the buck mode. The regulation module provides all regulation capability, and the other two modules operate at fixed duty cycle and provide the main conversion ratio. A prototype of the basic configuration was built to verify the theory. The peak efficiency of the prototype is 97.15%. [ABSTRACT FROM AUTHOR]

For single-phase three-level inverters, the neutral-point (NP) voltage balance problem must be solved to ensure normal operation. This brief proposes a robust voltage balance control method based on the model predictive control. The relative tracking errors of the grid current are used to judge which split capacitor voltage is larger. Then, the larger (smaller) split capacitor voltage will be used as the small vector when releasing power to the grid (absorbing power from the grid). Consequently, there is no need sampling the split capacitor voltages and the voltage sensors can be reduced. Besides, the NP voltage balance is well achieved even when the parameter drift happens to the grid inductor, which enhances the robustness. Finally, a T-type single-phase three-level grid-tied inverter platform is built to verify the effectiveness of the proposed control method. [ABSTRACT FROM AUTHOR]

In this work, we present a thin-profile, efficient power delivery approach, including a voltage regulator with in-package power inductor and backside power delivery network (PDN). To meet 1- $\mathrm {W}/{\mathrm {mm}}^{2}$ power-density target for high-performance computing (HPC) systems, a 25-high- $Q$ -factor (300 MHz), 150- $\mu \text{m}$ -thick, in-molding power inductor is provided for high-efficiency point-of-load (PoL) voltage regulation. Meanwhile, a novel analytical model for backside power delivery is developed for computer-aided-design (CAD) procedure to optimize the system efficiency. For the power flowing from bumps (57- $\mu \text{m} V_{\mathrm {DD}}$ -bump pitch) and backside PDN to active devices, the area resistances contributed by backside PDN and the buried power rail (BPR) are 23% and 77%, respectively, if a 10- $\mu \text{m}$ -horizontal-pitch nano- through-silicon via ($n$ TSV) is available. The resulting impact on power dissipation is within 1% so negligible. A higher ratio (0.5) buck converter with maintained efficiency is combined to better benefit the external interconnect. The overall power delivery efficiency $\eta \,\,=83$ % can be obtained for 1- $\mathrm {W}/{\mathrm {mm}}^{2}$ power-density target. The power losses contributed by an air-core inductor, power switches, and PDN/BPR/redistribution layer (RDL) are 26%, 66%, and 8%, respectively. [ABSTRACT FROM AUTHOR]

A variable-frequency critical-soft-switching (VF-CSS) model predictive control method is developed combining with a modified nonisolated inverter to improve the efficiency. A two-level control structure is developed, including 1) the central-level grid-side inductor current control and zero-sequence voltage control; and 2) the local-level per-phase power module control of VF-CSS model predictive controller with state estimator. Two VF-CSS controllers are proposed, including variable-continuous-frequency critical-soft-switching controller and variable-discrete-frequency critical-soft-switching, to achieve critical soft-switching operation for high efficiency. The combination of MPC and VF-CSS guarantees a complete critical soft-switching operation at full period range of varying frequency and especially during transient. The state estimator provides sampling noise rejection and accurate switch-side inductor current estimations for MPC and VF-CSS. Also, with the help of state estimator, the current sensor cost is reduced by 50%. Meanwhile, the estimator contributes to a more accurate switch-side inductor current reading for MPC implementation with variable continuous frequency controller, especially when the critical soft switching requires huge inductor current ripple. With the proposed control strategies and topology, medium-frequency ($>$ 200 kHz, 45 $\mu$ H) and high-frequency ($>$ 1 MHz, 4.5 $\mu$ H) test benches are validated experimentally. The efficiency is above 99% at a rated power of 15 kW. A power density of more than 10.4 kW/L is achieved. [ABSTRACT FROM AUTHOR]