Search

Droop control is broadly used in dc power distribution systems, e.g., dc microgrids. Implementing droop control for switch mode power supplies requires the measurement of average current. Synchronous sampling is used in digital control systems to obtain the average of a triangular inductor waveform. However, the dead time, semiconductor turn-on and turn-off delays, and signal conditioning delays shift the sensed waveform and change the effective duty cycle, resulting in a misalignment and measurement error from the average value. This paper proposes a duty cycle weighted averaging method based on double sampling. By sampling twice per switching period and averaging the results using duty cycle as the weighting factor, the error due to waveform misalignment is theoretically eliminated. The result always equals the average value of the triangle. This method does not rely on the knowledge of circuit delays, making it easy to implement and robust to parameter variations. Simulations and experimental measurements validate the superior performance compared with conventional single and double sampling methods. The experiment on a droop-controlled dc–dc converter demonstrates a more accurate droop characteristic. [ABSTRACT FROM AUTHOR]

Pulse-width-modulated (PWM) converters have been widely applied for power processing, and they are typically the stems of other types of converters, such as quasi-resonant, Z-source, and switched-inductor hybrid converters. Development of PWM converters has been spanning over a century, starting from the buck converter. The well-known PWM converters include buck, boost, buck–boost, Ćuk, single ended primary inductive converter (SEPIC), zeta, Z-source, quasi-Z source, etc. Many attempts have been proposed to develop these converters based mostly on canonical cell concepts and by introducing extra LC filters to the cells. This paper presents an enhancement to the layer and graft schemes by introducing the ideas of dc voltage/current offsetting, capacitor/inductor component splitting, diode grafting, and inverse operation of PWM converters. The PWM converters, which can be operated in continuous conduction mode (CCM) or discontinuous conduction mode (DCM), therefore can be synthesized systematically according to decoded transfer gains. Decoding and synthesizing PWM converters uniquely bridge transfer gains to converter topologies and provide readers a comprehensive understanding of PWM-converter evolution from the original converter, the buck converter. Additionally, in this paper, the Ćuk, SEPIC, and zeta converters all with the same transfer gain of $D/(1 - D)$ are proved to be equivalent to the buck–boost converter with an extra LC filter. For further illustrating the proposed approaches, various types of Z-source converters, switched-capacitor/switched-inductor hybrid converters, and a single-stage interleaved converter are reviewed, and new PWM converters are developed. [ABSTRACT FROM AUTHOR]

This paper presents an average current mode buck dimmable light-emitting diode (LED) driver for large-scale single-string LED backlighting applications. The proposed integrated current control technique can provide exact current control signals by using an autozeroed integrator to enhance the accuracy of the average current of LEDs while driving a large number of LEDs. Adoption of discontinuous low-side current sensing leads to power loss reduction. Adoption of a fast-settling technique allows the LED driver to enter into the steady state within three switching cycles after the dimming signal is triggered. Implemented in a 0.35-μm HV CMOS process, the proposed LED driver achieves 1.7% LED current error and 98.16% peak efficiency over an input voltage range of 110 to 200 V while driving 30 to 50 LEDs. [ABSTRACT FROM AUTHOR]

This paper presents an energy-recycling class-D low-side gate driver integrated circuit (IC), which can also perform 5-to-15-V level upconversion using a bidirectional flyback converter topology. The gate driver itself is a mini switching regulator that operates at 5–15 MHz to generate 1-μs transition time gate-switching waveforms. In order to maintain uniform charging/discharging currents during transitions, the embedded flyback converter operates in a pulse-frequency modulation mode while charging and in a pulse width modulation mode while discharging the gate node. The required pulses with digitally programmable frequencies and duty cycles are efficiently generated by a custom-designed IC fabricated in a 0.25-μm HV CMOS technology. Also, the presented analysis guides a way to achieve the desired transition time with the maximum efficiency. The prototype IC demonstrates 37.5% energy recycling while driving a 15-V insulated-gate bipolar transistor power switch with 105-nC gate charge at 20 kHz. [ABSTRACT FROM PUBLISHER]

Semiactive quadrupler rectifiers (SAQRs) are proposed in this paper to serve as the secondary rectification circuits, which make the secondary-side voltages to be controllable and help reduce current stress and conduction losses. An interleaved isolated boost converter is developed based on the proposed SAQRs. By utilizing the pulse-width modulation (PWM) plus phase-shift (PPS) control strategy, the primary- and secondary-side voltages are well matched to reduce the current values and circulating conduction losses. With the proposed SAQRs, the voltage gain is extended and the voltage stresses on power devices and passive components used in rectification circuits are reduced to the half of the high output voltage. Hence, the efficiency is improved by using a transformer with a smaller turns ratio and reduced parasitic parameters, and by employing low-voltage rating devices with better switching and conduction performance. With optimal design, lower voltage, and current stresses on the primary-side switches, minimized input current ripple can be realized. Moreover, the zero-voltage turn on switching of the active switches and the zero-current turn off switching of the diodes can be achieved over a wide load and voltage range by the proposed SAQR-based converter and the control strategy. Meanwhile, the higher voltage gain, the lower voltage, and the current stresses on power devices can be obtained with the proposed SAQR-based converter compared with passive quadrupler rectifier-based converter. The feasibility and effectiveness of the proposed SAQRs and the derived converter are verified by a 380-V output prototype. [ABSTRACT FROM PUBLISHER]

Interleaving of voltage-source converter (VSC) legs enables higher output currents per phase, effectively increasing the power rating without increasing semiconductor ratings. However, the interleaved operation results in circulating currents between each phase converter legs as well as a zero-sequence circulating current (ZSCC), which become quite prominent when the converters operate with low switching frequencies. This paper demonstrates the interleaved operation of three-level converters under selective harmonic elimination pulsewidth modulation (SHE-PWM). A controller for the circulating current within the legs of each phase is also proposed. The controller is used in combination with optimally selected SHE-PWM patterns to generate the maximum number of voltage levels and minimize the peak value of the circulating current. Simulation and experimental results show the interleaved operation and the effect of SHE-PWM pattern selection in the overall system. [ABSTRACT FROM PUBLISHER]

A zero-voltage switching (ZVS) grid-connected full-bridge inverter and its modulation schemes are investigated. A novel sinusoidal pulse width modulation scheme for the ZVS full-bridge inverter (ZVS SPWM) is proposed in this paper. The ZVS SPWM is evolved from the double-frequency SPWM by adding gate drive to the auxiliary switch. The ZVS condition is analyzed and the circulation loss of the resonant branch is optimized by adjusting the energy storage in the resonant inductor. The reverse recovery of the body-diode of MOSFET is relieved and ZVS is realized for both main and auxiliary switches. The filter inductors are significantly reduced with higher switching frequency. The design guideline of resonant parameters and the implementation of ZVS SPWM in DSP controller are introduced. The ZVS SPWM scheme is verified on a 3-kW inverter prototype. According to the experimental result, peak efficiency as 98.8% is achieved. [ABSTRACT FROM AUTHOR]

This paper proposes a new bidirectional three-phase push–pull converter that has a simple structure and achieves zero-voltage switching turn-on of switches. Also, due to use of a single inductor, an imbalance among phase currents on the low-voltage high-current side is trivial in the proposed converter although no current sharing control is employed. In this paper, a new dual asymmetrical pulse width modulation (PWM) switching method is proposed for bidirectional power flow control with seamless mode change. The proposed switching method offers reduced circulating current and makes the converter easier to implement compared to the PWM plus phase shift-based control method since it is a general PWM method having two independent duty cycle controls on each side. Experimental results from a 3-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM PUBLISHER]

Multilevel current source converters are a smart choice for the high-power applications with low-voltage and high-current requirements. This paper presents the detailed analysis of a current source modular multilevel converter (CSMMC) and its application as a STATCOM. Various properties of CSMMC are compared with the voltage-source modular multilevel converter (VSMMC). The submodule inductance selection method and a sorting-based algorithm for inductor current balancing are proposed for CSMMC. The validity of the inductance selection method and the inductor current balancing algorithm are confirmed by the simulation of a three-phase CSMMC using PSCAD/EMTDC. The carrier phase-shifted sinusoidal pulsewidth modulation is used as the switching technique. The performance of a converter is analyzed with interleaved and noninterleaved carrier signals for the upper and lower arms. Results show that CSMMCs and corresponding VSMMCs have analogous features. Hence, the development on VSMMCs can be used for reference to CSMMCs and vice-versa. Furthermore, the control designs for CSMMC-based STATCOM are presented and verified using simulations. The obtained results of the proposed STATCOM show that the steady-state and transient performance of the system are quite satisfactory. This makes the CSMMC suitable for HVDC and flexible ac transmission systems applications. [ABSTRACT FROM PUBLISHER]

This paper revisits the switched flow graph (SFG) technique. A general and unified equivalent SFG model of a three-terminal switcher encountered in regular and tapped inductor converters operating in the continuous conduction mode is proposed. The model can be applied to most PWM topologies and facilitates construction of a complete flow graph of a given converter. The approach can be helpful in theoretical analysis and derivation of analytical expressions of converter's small-signal transfer functions. The suggested methodology extends the previously proposed SFG analysis technique and alleviates the principal difficulties involved. Furthermore, the approach is straightforward and expeditious. Application guidelines and examples are presented and compared to simulation and earlier theoretical results. [ABSTRACT FROM PUBLISHER]

Carrier-based pulsewidth-modulation (CBPWM) techniques are popular due to their simplicity, and have been widely researched for various three-phase inverter configurations. In this paper, two CBPWM techniques are proposed to reduce the common-mode (CM) voltage generated by the five-phase inverter. The five-phase inverters have more flexibility in reducing the CM voltage than their three-phase counterparts because they have more phase legs, hence finer control over the star-point voltage of the load. Two methods are proposed for the conventional two-level five-phase inverter to reduce the CM voltage; one utilizing adjacent modulating waveforms and the other utilizing nonadjacent modulating waveforms. The coupled inductor inverter (CII) uses coupled inductors to generate multilevel outputs. As the volt-second balance must be maintained across each coupled inductor, direct application of the proposed methods on the CII inverter will result in overcurrents in the coupled inductors. Hence, the proposed methods are further improved to ensure the volt-second integral over each switching period is zero. Moreover, the two proposed methods are designed to reduce switching events and prevent unexpected states occurring during the switching transitions. The performance and the switching strategy of both methods are verified by both simulations and experiments on a prototype of five-phase CII. [ABSTRACT FROM AUTHOR]

In this paper, a family of three-phase direct pulse-width modulated (PWM) ac–ac converters consisting of buck, boost, and buck–boost converters is proposed. The proposed converters have no commutation problem even if all of the switches are turned on or off simultaneously. They do not use lossy snubbers and do not sense the voltage polarity for commutation, and produce high-quality output voltage waveforms. The proposed converters allow the use of power MOSFETs and fast recovery freewheeling diodes independently. The use of power MOSFETs as active switches and freewheeling diodes with extremely fast recovery features lower the switching losses and enable us to reduce the volume of passive components by increasing switching frequency. The input (or output) filter inductor experiences twice of the converter switching frequency and thus can be designed with minimum size. To increase power density of the proposed converters, a three-phase three-limb coupled inductor is proposed. Three-phase coupled inductor integrates three separate coupled inductors of the proposed converters in one three-limb core. In comparison with separate coupled inductors, the three-phase coupled inductor has a smaller size with large current-handling capability. Experimental results obtained for the boost-type converter show the robustness of the proposed three-phase ac–ac converters. [ABSTRACT FROM AUTHOR]

The three-level boost power factor correction (PFC) converter has advantages of lower inductor current ripple and lower switch withstanding voltage compared with the boost PFC converter. Interleaved pulsewidth modulation had been used in the multiphase boost PFC converter. In the literature, interleaved current sensorless control (ICSC) for the multiphase boost PFC converters had been proposed. In this paper, the behavior of the three-level boost PFC converter is first analyzed. The results show that three-level converter has the same average equation as the interleaved boost PFC converter. Then, ICSC is modified for the three-level boost PFC converter with considering the voltage imbalance and the zero-crossing current distortion. The proposed modified ICSC (MICSC) is implemented in a field-programmable gate array board. Simulation results and experimental results are also provided to validate the proposed MICSC. [ABSTRACT FROM PUBLISHER]

In this paper, a generalized switching modification method is proposed to reduce the root-mean-square (rms) current flowing into a dc-link capacitor in a dc–dc–ac structure consisting of a boost converter and a three-phase inverter. To analyze the current flowing into the capacitor, we analyze the currents at the respective converter and inverter sides. Based on this analysis, we derive an analytical method to find the modification time between the converter and inverter pulsewidth modulation (PWM) carriers through a Fourier series and approximation to facilitate real-time implementation. Real-time implementation of the modification time calculated by the derived method is described. To verify the validity of the proposed method, experimental results are presented based on a 1-kVA dc–dc–ac prototype. The proposed method has a better capacitor rms current reduction performance than the conventional method in various inverter power factors and PWM strategies. Especially, it has an excellent performance in mid-power factor level (0.95–0.1). [ABSTRACT FROM AUTHOR]

A switching-capacitor-based buck–boost converter (with common ground) for point of load applications is proposed in this paper. It is capable of operating in stand-alone buck or boost mode in addition to its primary operation of performing the buck–boost conversion. The striking feature of the proposed converter is low source current ripple content irrespective of its mode of operation (buck–boost, buck, or boost). First, feasible pulsewidth modulation schemes for the proposed converter are identified and thereafter the corresponding circuit performance analysis, steady-state analysis, and state-space modelling is established. Through steady-state analysis, voltage gain expressions are formulated and equations defining L-C components are derived in terms of their ripple quantities. The state-space models are used to formulate small-signal analysis and to obtain the relevant transfer functions required in the controller design. A voltage-mode/current-mode controller is designed, with a tradeoff in bandwidth, to control the proposed converter and transit it from buck to boost mode or vice versa seamlessly. A 30–55 W, 100 kHz, prototype point of load converter with 36-V input dc source is built to supply power at constant load voltage of either 48 or 28 V. The proposed converters’ effectiveness is demonstrated experimentally in terms of reduced source current ripple along with seamless transition from buck to boost mode and vice versa. [ABSTRACT FROM AUTHOR]

This paper proposed a novel family of pulsewidth modulation (PWM) strategies for single-phase quasi-switched boost inverter (qSBI). By combining shoot-through (ST) mode in the inverter's switches and the turning-on state of an additional switch, the qSBI produced a high voltage gain without adding any passive components. Compared to the conventional PWM strategy for the same input and output voltage gain, the introduced PWM strategies for qSBI could reduce voltage stress across semiconductors and capacitor with the following additional merits: having smaller high-frequency inductor current and capacitor voltage ripples, using high modulation index with low ST duty cycle, and having higher efficiency. Circuit analysis, operating theories, and simulation results of the single-phase qSBI with the introduced PWM5 strategy are shown. A 500-W laboratory prototype was constructed and the effectiveness of the introduced PWM strategy was validated. The qSBI with the proposed PWM strategies is suitable for applications where the required voltage gain lies between 2 and 3. [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]

High step-down voltage conversion is necessary to bridge the voltage gap between main power converters and low-voltage auxiliary electronics in power conversion systems. Switched capacitor converters (SCCs) are an attractive candidate as a high step-down converter, but their poor voltage regulation capability may limit their applications. Pulsewidth modulation (PWM) SCCs with adjustable high step-down voltage conversion are proposed in this paper. The proposed PWM SCCs can be derived from traditional SCCs by replacing an energy transfer capacitor with a switched-capacitor-inductor (SCL) cell that comprises inductors, capacitors, and diodes to realize PWM-controllable voltage conversion. The voltage step-down ratio of the proposed PWM SCCs is not only PWM controllable but also adjustable with structures of SCCs and SCL cells. Two representative PWM SCCs were taken as examples to perform the operational analysis. The prototypes of both representative PWM SCCs were built and tested to demonstrate the proposed concept. [ABSTRACT FROM AUTHOR]

A division–summation (D-\mathbf\Sigma) digital control for three-phase inverters to achieve active and reactive power injection has been presented. It can overcome the limitation of abc to dq frame transformation. However, the D-\mathbf\Sigma control requires four sets of control laws to cover four quadrant operations, namely, grid connection (power factor (PF) 1 $\sim\pm$0.866), rectification with PF correction, PF leading (0 \sim$ 0.866), and PF lagging (0 \sim$ −0.866). Moreover, the switching sequences for the four modes are also different from each other, increasing complexity of firmware programming. In this paper, improvement of the control law derivation and region selection for the (D), which can obtain the control law directly. Measured results from a 10-kVA 3 $\phi$ bidirectional inverter have been presented to confirm the improvement. [ABSTRACT FROM PUBLISHER]

This paper presents novel single-phase pulse width modulation (PWM) ac-ac converters that can solve the commutation problem in single-phase direct PWM ac-ac converters without sensing the input voltage polarity. By using a basic switching cell structure and coupled inductors, the proposed ac-ac converters can be short- and open-circuited without damaging the switching devices. Neither lossy RC snubber nor dedicated soft commutation strategy is required in the proposed converter. By replacing the conventional phase-leg of the PWM ac-ac converters with the switching cell structure and the coupled inductor, three novel buck, boost, and buck-boost type PWM ac-ac converters are developed. Although two coupled inductors are required for the proposed converter, the input inductor of the proposed converter can be much smaller than that of the conventional PWM ac-ac converters. The volume of the magnetic components can be further reduced by increasing switching frequency of the converter because very fast recovery diodes can be selected externally. In order to verify performance and robustness of the proposed converter, a 200-W boost type prototype converter was built and tested with both mismatched gate signals and highly distorted input voltage. [ABSTRACT FROM AUTHOR]

Although the operation of a three-phase current source rectifier (CSR) for ac-to-dc conversion using phase control or low-frequency pulse control is well established in a wide variety of applications, CSR realization using high-frequency pulsewidth-modulation control has been recently studied as a potentially competitive alternative to a voltage source rectifier. In the CSR, reverse blocking gate turn-off switches are realized using series-connected diodes, which prevent any reversal of the dc-link current. A significant consequence of this limitation occurs at light load conditions. The dc-link inductor current enters the discontinuous mode of operation and leads to the loss of the control of the output voltage and a highly distorted input current, which compromise the potential advantages of the approach. This paper characterizes the CSR while operating in the discontinuous conduction mode and proposes a modulation strategy that restores the control of the output voltage and ensures a nearly sinusoidal current at light loads. Simulation and hardware results are provided for a 3-kW laboratory-scale prototype system. [ABSTRACT FROM AUTHOR]

The propagation delay of a comparator and dead time causes the duty-discontinuity region near the boundary of the step-down and step-up regions in a non-inverting buck–boost (NIBB) converter. The duty-discontinuity region leads to an unstable output voltage and an unpredictable output voltage ripple, which might cause the entire power system to shut down. In this paper, a mode-transition technique called duty-lock control is proposed for a digitally controlled NIBB converter. It locks the duty cycle and eliminates the error between the output voltage and the reference signal by using a proposed fixed reference scheme that ensures the stability of the digital controller and output voltage. The experimental results that were applied to a field-programmable gate array-based platform revealed that the output voltage of the NIBB converter is stable throughout the entire transition region, without any efficiency tradeoffs. The input voltage of the converter that was provided by a Li-ion battery was 2.7–4.2 V, and the output voltage was 1.0–3.6 V, which is suitable for radio-frequency power amplifiers. The switching frequency was 500 kHz, and the maximum load current was 450 mA. [ABSTRACT FROM PUBLISHER]

In this paper, a novel direct ac–ac converter based on the coupled inductor Z-source networks is proposed that offers a wide range of buck–boost operation. A total of two Z-source networks, called the coupled switched inductor and the modified switched coupled inductor, are employed that enable the ac–ac converter to deliver a wide voltage range. The proposed converter with both networks provides free-wheeling current paths for the inductors currents during the state transitions, which results in solving the commutation problems and the need for snubber circuits. A simple switching strategy is then proposed that helps to share a common magnetic core between the coupled inductors. For any particular voltage gain, the proposed structures require a smaller duty cycle compared to the conventional ones; therefore, a smaller inductance is required. Simulation and experimental results are provided to confirm the theoretical achievements. [ABSTRACT FROM AUTHOR]

Recent power systems, such as renewable energy systems consisting of solar panels and rechargeable batteries, contain multiple power sources and need multiple converters in proportion to the number of power sources, resulting in increased system complexity and cost. This paper proposes a multiport converter (MPC) integrating a bidirectional PWM converter and series-resonant converter. Not only is the switch count halved with the proposed MPC, but also magnetic components can be integrated, reducing the circuit complexity and volume. A 150-W prototype of the proposed MPC was built for the experimental verification. The measured voltage conversion characteristics and transient responses demonstrated that the proposed MPC could control load and battery voltages independently by pulse width modulation and pulse frequency modulation controls, respectively. [ABSTRACT FROM AUTHOR]

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

This paper proposes the pulsewidth modulation (PWM) strategy of Z-source inverters (ZSIs) with minimum inductor current ripple. In existing PWM strategy with single-phase shoot-through, the shoot-through time interval is divided into six equal parts, therefore the three phase legs bear the equal shoot-through time interval. In this manner, the allotment and arrangement of the shoot-through state is easy to realize, but the inductor current ripple is not optimized. This causes to use relatively large inductors. In the proposed PWM strategy, the shoot-through time intervals of three phase legs are calculated and rearranged according to the active state and zero state time intervals to achieve the minimum current ripple across the Z-source inductor, while maintaining the same total shoot-through time interval. The principle of the proposed PWM strategy is analyzed in detail, and the comparison of current ripple under the traditional and proposed PWM strategy is given. Simulation and experimental results on the series ZSI are shown to verify the analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a new modeling and control technique for a three-phase boost converter is presented for efficient transfer of energy from an irregular input power source to a battery storage device or a dc link. First, a circuit model for a three-phase boost converter is developed using the method of averaging, followed by a derivation of the conditions under which the pulse width modulated switching circuit exhibits a resistive behavior from the input. Based on the circuit model obtained, a new model-based feedback control scheme is presented to regulate the phase-to-phase input resistances of the circuit to desired values. The circuit can provide purely active power conversion of a band-limited input voltage source to a dc link, which is of interest in boost converters for certain energy conversion systems. Simulation and experimental results are presented that illustrate performance of the proposed modeling, feedback control, and switching scheme for a low-power application. [ABSTRACT FROM PUBLISHER]

Radio-frequency identification (RFID) technology has been widely used in passive RFID localization application due to its flexible deployment and low cost. However, current passive RFID localization systems cannot achieve both highly accurate and precise moving object localization task owing to tag collisions and variation of the behavior of tags. Most researchers increase the density of tag distribution to improve localization accuracy and then consider using either anti-collision process embedded in the hardware of the RFID reader or advanced localization algorithms to enhance localization precision. However, advanced anti-collision processes for RFID devices are challenged by the physical constraint characteristics of radio frequency; and improved localization algorithm cannot fundamentally reduce the impacts of tag collision on localization precision. This research work attempts to improve localization precision of a passive RFID localization system by using sparsely distributed RFID tags. This paper first defines a measure for accuracy and precision in a passive RFID localization system with regard to RFID tag distribution. An exponential-based function is then derived from experimental measurements, which reflects the relationship between RFID tag distribution and localization precision. This function shows that localization precision is mainly determined by tag density of RFID tag distribution. Based on the experimental findings, a sparse RFID tag distribution approach is proposed. The results show that in comparison with the conventional RFID tag distribution, passive RFID localization system with sparse RFID tag distribution can deliver a higher localization precision for the required accuracy. [ABSTRACT FROM PUBLISHER]

In this paper, a three-level quasi-switched boost T-type inverter (3L qSBT2I) is proposed. A new pulse-width modulated (PWM) control method is presented to reduce the inductor current ripple of the qSBT2 I. In the introduced PWM technique, the shoot-through duty cycle is maintained constant to keep the modulation index as high as possible. Then, the only control parameters of the qSBT2I are the duty cycles of the two additional switches. By controlling the duty cycles of the two additional switches, the voltage gain of the proposed qSBT2 I can be improved to a value larger than that of the conventional 3L impedance source inverters. The steady-state analysis, operating principles, and comparisons with the impedance source-based 3L inverters are presented. A 1-kW prototype is constructed to verify the operating principle of the 3L qSBT2I. An indirect dc-link voltage regulator and a capacitor voltage-balance controller are applied to the proposed qSBT2I. Simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper investigates a multilevel inverter composed of series/parallel-connected H-bridges. The presented structure can be used for applications in which the use of semiconductor switches with low-voltage and low-current ratings is intended. A comprehensive system model, an overall control strategy to adjust the output voltage with constant magnitude and frequency, and a level-shifted PWM (LS-PWM) strategy based on a voltage vectors unidimensional analysis and a plane analysis are presented. The LS-PWM is capable of mitigating the low-frequency circulating current, thus generating multilevel voltage signals with low harmonic distortion, maximum number of levels, and low dv/dt. In addition, considering a wide range of values of voltages and currents and various power levels, the total converter losses are reduced compared with the conventional multilevel converters. Two multilevel conventional inverters with the same number of semiconductor switches are used for comparison. Simulation and experimental results demonstrate the feasibility of the studied converter. [ABSTRACT FROM AUTHOR]

Soft switching pulse-width modulation (PWM) dc–dc full-bridge converter with controlled rectifier on the secondary side of the high-frequency power transformer is presented in this paper. An active secondary switch, including new nondissipative passive energy recovery turn-off snubber on the secondary side and modified PWM control algorithm, provide conditions for zero-voltage and zero-current turn-on and zero-current turn-off of IGBT transistors on the primary side of the high-frequency dc–dc converter. The simple passive energy recovery snubber ensures also zero-voltage turn-off of the transistor on the secondary side of the power transformer. The principle of operation is explained and analyzed and consequently verified on a 2 kW, 50 kHz laboratory model of the converter. [ABSTRACT FROM PUBLISHER]

Interleaved converter legs are typically modulated with individual carriers per leg and phase-shifted pulse width modulation (PS-PWM) as it facilitates current balancing amongst the legs. Phase-disposition PWM (PD-PWM), despite the better harmonic performance, cannot be directly used due to the resulting current imbalance that may damage the converter. This paper addresses the current sharing issue and proposes a sorting algorithm implementation that enables single-carrier PD-PWM technique for interleaved two-level converter legs. An extension of the proposed algorithm through a switching state feedback loop, limiting the average switching frequency, is also developed. In both cases, the output current is of high quality and shared amongst the phase-legs, while the deviation between the phase-leg currents is well regulated. Simulation results demonstrate the general function of method for multiple interleaved legs as well as its current sharing capabilities for high-power applications. Experimental results from a low-power laboratory prototype validate the operation of the proposed approach. [ABSTRACT FROM PUBLISHER]

This paper extends the trans-Z-source concept to ac–ac power conversion and proposes a novel single-phase trans-Z-source ac–ac converter. The proposed converter retains the advantages of its existing Z-source/quasi-Z-source counterparts in which the output voltage can be boosted and in-phase with the input voltage or bucked/boosted and out-of-phase with the input voltage. Meanwhile, a coupled inductor is introduced into the proposed converter, and the turns ratio of the coupled inductor become another control variable beside the duty cycle to obtain extreme voltage gain. Importantly, the input voltage and output voltage share the same ground, and the input current could be continuous, which is a benefit for reducing input current harmonics. Most important of all, the safe-commutation strategy for the proposed converter is deep developed, and analytic expression between the switches state and loop circuit voltage/current condition is derived out. Hence, the current/voltage ripple can be avoided without a loss snubber circuit, which benefits a reduced cost and enhanced reliability. The performance analysis is discussed in consideration of parasitic resistance, and system parameter design is optimized based on theoretic calculation. A laboratory prototype is fabricated, and experiments are performed to verify the validation of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper proposes a pulse width modulation plus phase-shift (PPS) control for nonisolated high gain soft-switching bidirectional dc–dc converter (HSBDC). The phase-shift angle is used to control the direction and amount of power flow of the bidirectional dc–dc converter, while the duty cycle is used to balance the voltage between two high voltage side (HVS) capacitors. The HSBDC with PPS control has the advantages of simple control structure and symmetrical switching patterns, ensured soft-switching in both forward and backward modes at all load under wide voltage range, and reduced voltage ratings of the HVS capacitors and switches. The operation principle of the HSBDC with PPS control is analyzed in detail. Based on the analysis the passive component is designed to achieve higher efficiency. A 3-kW prototype is implemented and tested to verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, dual-buck structured single-stage buck–boost inverters that use power MOSFETs to achieve high efficiency are presented. The proposed inverters require fewer switches, and half of the switches have reduced current stresses. They have no shoot-through problem; therefore, high system reliability can be obtained. The dead-time in PWM signals can be minimized or eliminated, which improving the quality of the output ac voltages and increasing the efficiency. In the proposed inverters, MOSFETs can be used without reverse-recovery issues of their body diodes to boost the efficiency and increase the switching frequency. To further improve the efficiency and stability of the proposed single-phase inverter, PWM strategies combining high- and low-frequency modulation are presented. A hardware prototype of the single-phase inverter was built and tested using resistive, inductive, and nonlinear loads. Experimental results for a 300-W prototype inverter show a 97.4% peak efficiency with a 25 kHz switching frequency. [ABSTRACT FROM AUTHOR]

This paper presents a comparative evaluation of eight high-voltage step-up converters based on different associations of boost and zeta standard dc–dc pulse width modulation (PWM) cells. These eight converters present different characteristics such as cascaded and stacked PWM cell associations, as well as isolated winding coupled inductors, tapped winding coupled inductors, and noncoupled inductors. In order to explore the advantages and address the limitations of each topology, several comparative evaluations concerning static voltage gain, power losses, current and voltage stresses, component stress factors, power density, relative cost, and efficiency were carried out. From the theoretical analysis and experimental results, the association named stacked boost–zeta with autotransformer yielded the highest efficiency and power density and resulted in the most attractive converter for the case study. [ABSTRACT FROM PUBLISHER]

ZSVM1, ZSVM2, and ZSVM6 are three traditional space vector modulation (SVM) strategies for three-phase Z-source inverter. The shoot-through times of ZSVM1, ZSVM2, and ZSVM6 are divided into two equal parts, four equal parts, and six equal parts, respectively. Although these control strategies are easy to be implemented in program, their inductor current ripples are not optimized, causing large current ripple. This paper proposes new SVM strategies, named ZSVMD6 and ZSVMD1, for reducing inductor current ripples of Z-source inverter. The principle of volt–second balance is used in the proposed strategies to divide shoot-through times in real time. So every divided shoot-through time is not equal, and changing in real time. The divided shoot-through time can ensure that the sum of the inductor charging current ripple and discharging current ripple is zero at each time, therefore reducing the inductor current ripples. The derivation details of the proposed strategies are given. The inductor current ripples of the proposed strategies and traditional ones are compared and analyzed. Simulation and experiment results show that the inductor current ripples of the proposed strategies are much lower than that of the traditional ones, verifying the effectiveness of the proposed strategies. [ABSTRACT FROM PUBLISHER]

This paper proposes a new bidirectional direct pulse width modulation (PWM) three-phase buck-boost ac–ac converter. It requires six switches and three inductors and can provide wide range buck-boost voltage operation. It has high reliability due to no short-circuit and open-circuit risks in the converter. Therefore, it solves the commutation problem without using lossy snubber circuits, soft commutation strategies, and coupled inductors. It can be designed with metal–oxide–semiconductor field-effect transistors (MOSFETs) without their body diodes conducting, which eliminate reverse recovery issues and losses of body diodes. In addition, to reduce the ripples in input and output voltages and currents, the proposed converter can be operated with a PWM strategy-II. The PWM strategy-II is a type of interleaved PWM strategy with dead- and overlap-times operating modes. To validate the effectiveness of the proposed converter extensive analysis followed by detailed experimental results are provided. [ABSTRACT FROM PUBLISHER]

The parallel three-phase grid-connected converters sharing dc and ac bus can increase the system power level effectively. However, the circulating current will occur inevitably. The existing studies primarily focus on dc, fundamental, and low-frequency circulating current. The high-frequency circulating current (HFCC) caused by asynchronous carriers is studied emphatically in this paper, which is based on the analysis of the change of circulating current in one control cycle. A novel method to suppress HFCC caused by asynchronous carriers of modules is proposed. In this method, the carrier period of slave module is adjustable and the carrier period of the master module is constant. When a large phase shift between modules occurs, an adjusting cycle is inserted to carrier of slave module to realize resynchronizing with master module. It is noted that there is no other commutation between the two modules (expect the dq current reference), such as the carrier information. Finally, the feasibility and effectiveness of the proposed method are verified by experiments. [ABSTRACT FROM PUBLISHER]

To prevent partial-shading issues in photovoltaic (PV) systems, various kinds of voltage equalizers that virtually unify characteristics of shaded and unshaded modules have been proposed. Although PV string utilization can be dramatically improved, PV systems tend to be complex and costly because, in addition to the main converter for string control, voltage equalizers are separately necessary. This paper proposes the single-switch single-magnetic pulse width modulation (PWM) converter integrating the voltage equalizer using the series-resonant voltage multiplier (SRVM) for standalone PV systems. By utilizing a square wave voltage generated across a filter inductor in a PWM buck converter for driving the SRVM, the main PWM converter and voltage equalizer can be integrated into a single unit with reducing the total switch and magnetic component counts, achieving not only system-level but also circuit-level simplifications. The experimental test using the prototype for three PV modules connected in series was performed emulating a partial-shading condition. The integrated converter effectively precluded the partial-shading issues and significantly improved the power available at a load, demonstrating its efficacy. [ABSTRACT FROM AUTHOR]

In this paper, a new zero-voltage switching and resonant core reset pulse width modulation forward converter with a simple auxiliary circuit is introduced. The proposed auxiliary circuit can be applied to both single-switch and two-switch forward converters. The main and the auxiliary mosfets of the proposed converters operate under soft switching condition independent of line and load variation. Also, due to the capability of operating at duty cycles higher than 0.5, the proposed converters can be used for wide input voltage applications. In comparison to the existing zero-voltage transition (ZVT) forward converters, this auxiliary circuit has low number of components and also does not require any additional magnetic element which has improved the power density. The proposed converter is compared with exiting ZVT forward converters in details. The converter steady-state operation is analyzed and various operating modes are explained. Also, in addition to a design example, a comprehensive design procedure is presented. The experimental results of a laboratory prototype of the converter with 85–180 V input voltage and 24 V output voltage at 150 W are provided which verify the theoretical analysis and confirm the converter operation. The overall efficiency of 93.5% is achieved for the proposed converter at full load. [ABSTRACT FROM PUBLISHER]

This paper first starts with reviewing several commonly practiced PWM schemes for the three-phase isolated buck matrix-type rectifier. Then, an optimal six-segment PWM scheme (“Type A”) is proposed. The analysis shows “Type A” PWM scheme has lower duty-cycle loss, maximum output inductor current ripple, and minimum switching loss comparing with other PWM schemes when the mosfet devices are employed. In addition, a low input current total harmonic distortion (THD) can be achieved with duty-cycle compensation. Finally, the steady-state analysis of duty-cycle loss, inductor current ripple, and THD are all compared and verified by the experimental results for “Type A” PWM and eight-segment PWM (“Type E”). [ABSTRACT FROM PUBLISHER]

DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques. [ABSTRACT FROM AUTHOR]

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

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

This letter proposes a boost dc–dc converter topology with the novel capability of canceling the input current ripple at an arbitrarily preselected duty cycle. This is accomplished without increasing the count of the number of components in contrast to other solutions available in the literature. In addition, the converter features a high voltage gain without utilizing extreme values of duty cycle or boosting transformers. These features make the converter ideal to process electric power coming from low-voltage power-generating sources, such as renewables. This paper provides details on the principle of operation via topological considerations and a mathematical model. The key factor of reactive component sizing is also discussed in detail. The converter was validated in the laboratory through the construction of a hardware prototype. [ABSTRACT FROM PUBLISHER]

Considering the tradeoff between efficiency and output ripple over a wide load range, a monolithic dc–dc buck converter with switch-on-demand modulation (SODM) and switch size control (SSC) is presented in this paper. SODM achieves a hybrid mode of pulse skip and pulse width modulation (PWM) without mode detection circuit. The converter's on time is adaptively adjusted with the load demand, achieving low output voltage ripple. Detecting the output of the error amplifier by a comparator, the SSC circuit can select appropriate switch size according to load current for reducing switching loss in a light load. The threshold level of the comparator varies with respect to the amount of slope compensation, which maintains a substantially constant switch size changing point. Experimental results show that the fabricated converter with the proposed scheme achieves high efficiency from 83% to 96% over a wide load range from 10 mA to 5 A. The switch size is 1/4 of the maximum value when load current is below 1 A with 0.5-A hysteresis. Also, the measured maximum output ripple is less than 10 mV. [ABSTRACT FROM PUBLISHER]

A new 2-D random-switching pulsewidth modulation (PWM) technique is proposed to reduce the dominant harmonic clusters while retaining constant average inductor current and constant sampling frequency. The special feature of constant average inductor current can reduce the output voltage ripple. Moreover, the controller parameters of a digitally controlled power converter are not required to change, which is quite essential to digitally controlled systems. Current random PWM methods are discussed and compared with the proposed method in this paper. It will be shown that the merits of the presented method include random-switching frequency, constant sampling frequency, and constant average inductor current. An field-programmable-gate-array-based digitally controlled buck converter experimental system has been set up. The specifications of the converter include input\ voltage = 5\ \V, output\ voltage = 1.5\ \V, and switching\ frequency = 200\ \kHz. The proposed random-switching pattern is implemented by software. Experimental results demonstrate the effectiveness of the proposed random-switching pattern. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel nonisolated flyback switching capacitor voltage regulator. The converter is a combination of a switching capacitor converter and a pulsewidth modulation voltage regulator, and it has the following advantages: 1) the switches achieve zero voltage switching (ZVS); 2) the self-driven method of the synchronous rectifier (SR) is applied to save the drive loss and the body diode conduction loss; 3) the transformer leakage inductor is utilized to realize the soft switching of the switches; and 4) single-phase option makes it more flexible. Its derivation, operation principle, and self-driven method are presented. A single-phase 700 kHz 1.2 V/35 A output point-of-load prototype was built to verify the analysis. [ABSTRACT FROM AUTHOR]

This paper presents a soft-switching pulsewidth modulation (PWM) nonisolated boost dc–dc converter embedding an edge-resonant switched capacitor (ER-SWC) cell and its interleaved circuit topology. The conceptual boost dc–dc converter treated herein can achieve high-frequency zero-current soft-switching turn-on and zero-voltage soft-switching turn-off operations in the active switches and minimization of a reverse recovering current in the freewheeling diode under discontinuous conduction mode partially including critical conduction mode in the input current. Those advantageous properties enable a wide range of soft-switching operations together with a high-voltage step-up conversion ratio with a reduced current stress. Circuit design guideline based on the soft-switching range is introduced; then, a theoretical analysis is carried out for investigating the step-up voltage conversion ratio. For demonstrating the effectiveness of the ER-SWC soft-switching PWM boost dc–dc converter and its newly developed interleaved topology, laboratory prototypes are evaluated in experiments; then, their performances are discussed from a practical point of view. [ABSTRACT FROM PUBLISHER]