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This paper presents a voltage-balancing method for stacked multicell converters (SMCs) based on phase disposition pulsewidth modulation. A cost function is evaluated to select the optimum state from a pool of redundant possible ones at each voltage level. It is demonstrated that, if sawtooth carriers are used for modulation instead of standard triangular ones, significant reduction in the switching frequency and the associated power losses of the power devices can be achieved without affecting the voltage-balancing capability. Experimental results from a seven-level SMC laboratory prototype are provided to verify the proposed voltage-balancing method against linear and nonlinear loads, as well as under transient conditions. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) becomes attractive for medium- or high-power applications because of the advantages of high modularity, availability, and power quality. One of the technical challenges associated with an MMC is the balancing of the capacitors' voltages. In this paper, a voltage-balancing control method is proposed for the MMC under phase-shifted carrier-based pulsewidth modulation. The proposed voltage-balancing method uses the linearization method for pulse sorting without arm current measurement, which can control the capacitor charge transfer to balance the capacitor voltage in the MMC. In the proposed method, the voltagebalancing algorithm is implemented in each carrier wave period, which reduces the computational intensity and burden. In addition, the arm current can also be improved with the proposed method. The simulation studies with the professional tool PSCAD/EMTDC are conducted, and a downscale MMC prototype is also tested with the proposed method. The study results show the effectiveness of the proposed voltage-balancing method. [ABSTRACT FROM PUBLISHER]

This paper presents a power factor correction (PFC)-based bridgeless isolated Cuk converter-fed brushless dc (BLDC) motor drive. A variable dc link voltage of the voltage source inverter (VSI) feeding the BLDC motor is used for its speed control. This allows the operation of VSI in fundamental frequency switching to achieve an electronic commutation of the BLDC motor for reduced switching losses. A bridgeless configuration of an isolated Cuk converter is derived for the elimination of the front-end diode bridge rectifier to reduce conduction losses in it. The proposed PFC-based bridgeless isolated Cuk converter is designed to operate in discontinuous inductor current mode to achieve an inherent PFC at the ac mains. The proposed drive is controlled using a single voltage sensor to develop a cost-effective solution. The proposed drive is implemented to achieve a unity power factor at the ac mains for a wide range of speed control and supply voltages. An improved power quality is achieved at ac mains with power quality indices within the limits of the IEC 61000-3-2 standard. [ABSTRACT FROM PUBLISHER]

A hybrid switched-capacitor/interleaved boost converter able to provide a high voltage gain and to cancel the input current ripple at a preselected duty cycle was recently presented in the literature. This paper extends that work by proposing an optimized switching strategy for operating conditions at other values of duty cycle. The switching strategy effect on the converter's voltage gain and input current ripple is quantified and compared against the performance under the conventional switching strategy. The approach is validated in the laboratory through hardware prototyping. [ABSTRACT FROM PUBLISHER]

This paper analyzes the interleaved boost with coupled inductors (IBCI) converter, which is an isolated topology that is suitable for high step-up applications. Two main contributions are given: an exhaustive steady-state analysis and an accurate small-signal model. The former allows for deriving a closed-form noniterative design procedure for the power-stage active and passive components. In addition, it reveals an interesting equivalence with an apparently different converter, i.e., the single active bridge. Subsequently, the IBCI converter dynamic behavior is investigated, deriving a nonlinear average model that, under small-signal approximation, can be linearized around a given operating point and used for feedback controller design. A single photovoltaic module interface converter, rated for 300-W output power, is considered as a case study to validate the analysis outcome and the design procedure. Both are fully validated by measurements taken on the laboratory prototype. [ABSTRACT FROM PUBLISHER]

A photovoltaic (PV)-based stand-alone power system is usually used to manage the energy supplied from several power sources such as PV solar arrays and battery and deliver a continuous power to the users in an appropriate form. Traditionally, three different dc/dc converters would have been used. To reduce the cost and improve the power density of the power system, an integrated solution of PV isolated dc/dc three-port converter (TPC) is proposed in this paper. Zero current switching can be achieved for all main diodes and MOSFETs to improve the efficiency, and a continuous input current of solar array is maintained by adding a magnetic switch derived from a fourth winding of the half-bridge transformer. Based on the energy-balancing part formed by boost, the control methods for the single module to realize maximum power point tracking (MPPT), battery charge control, and main bus regulation are proposed. The power system control method for multimodules in parallel is also derived, and the operation of the TPC power system can be transited between conductance mode and MPPT mode automatically. Finally, the experimental results verify that the proposed TPC, together with the proposed control method, meets the requirements of a high-power-density stand-alone PV-battery power system. [ABSTRACT FROM PUBLISHER]

This paper presents a novel microinverter for a single-phase grid-connected photovoltaic (PV) system. The proposed microinverter consists of a step-up dc–dc converter using an active-clamp circuit with a series-resonant voltage doubler and a high-efficiency inverter with single-switch-modulation step-down converters. The active-clamp circuit provides zero-voltage switching (ZVS) turn-on, recycles the energy stored in the leakage inductance of the transformer, and limits switch voltage stress. Moreover, to remove the reverse-recovery problem of the rectifier diodes, a series-resonant voltage doubler is used. Thus, this whole process provides high efficiency. To improve efficiency and reliability in the proposed inverter, only a single switch is modulated at the switching frequency without a shoot-through problem. A modified controller is also adopted to achieve fast output control. Thus, the proposed PV microinverter has the structure to minimize power losses. The experimental results show a maximum efficiency of 96.2% for a 400-W microinverter. [ABSTRACT FROM PUBLISHER]

Automotive embedded electronic systems have been increasing in power and complexity and, therefore, more advanced power electronic converters are necessary in these vehicles. Several dual-voltage (42 V/14 V) bidirectional converter architectures have been proposed for automotive systems in recent years. However, most of them have low efficiency or are based in series and parallel configurations with large number of semiconductors and magnetics devices. Therefore, in this paper, we propose a bidirectional high-efficiency converter with lower number of components. This converter was created by merging a switched-capacitor converter and a conventional bidirectional converter, resulting in a hybrid topology. The voltage across the semiconductors of the proposed converter is equal to half of the highest voltage source value. Furthermore, the topology is composed of only one inductor to control the power flow between the two voltage sources. To verify all the mentioned features, a prototype was implemented experimentally, reaching a maximum efficiency of 97.5%. [ABSTRACT FROM PUBLISHER]

This paper introduces an active method for zero current switching for resonant switched capacitor converters (SCC) with wide dynamic range. The method is demonstrated on a binary SCC that features wide range of conversion ratios. Due to the resultant high efficiency of the converter operating under soft-switching conditions, it is applicable for higher power levels up to the medium power range (100 W). The resonant operation is achieved with a single air core inductor and precise commutation at zero current. The sensing signals of the resonant currents are obtained from the flying capacitors rather than form element in which the current includes a dc component. The zero detection method developed is capable of compensating for both the processing delays (from detection to switching action) and for the large variations of the resonant characteristics (due to transition between subcircuits), and for any other component variations. A 100 W prototype with maximum input voltage of 100 V and up to 19 conversion ratios has been built and tested experimentally. The current sensing has been implemented with a simple, cost-efficient, passive sensor. For proper construction of a higher power experimental prototype with desired target efficiency, a set of design considerations for the selection of the power stage components, based on an expanded equivalent resistance concept for multiple subcircuits converter, has been delineated. In addition, a simple and efficient isolated gate driver circuitry is presented. [ABSTRACT FROM AUTHOR]

In this paper, we review relevant problems in the modeling of dc–dc converters with switched capacitors. We study several approaches that overcome the exposed modeling difficulties, addressing ideal and nonideal cases and using dynamic equations that are valid in a large-signal domain. [ABSTRACT FROM PUBLISHER]

A single-switch nonisolated dc/dc converter for a stand-alone photovoltaic (PV)-battery-powered pump system is proposed in this paper. The converter is formed by combining a buck converter with a buck-boost converter. This integration also resulted in reduced repeated power processing, hence improving the conversion efficiency. With only a single transistor, the converter is able to perform three tasks simultaneously, namely, maximum-power-point tracking (MPPT), battery charging, and driving the pump at constant flow rate. To achieve these control objectives, the two inductors operate in different modes such that variable switching frequency control and duty cycle control can be used to manage MPPT and output voltage regulation, respectively. The battery in the converter provides a more steady dc-link voltage as compared to that of a conventional single-stage converter and hence mitigates the high voltage stress problem. Experimental results of a 14-W laboratory prototype converter with a maximum efficiency of 92% confirmed the performance of the proposed converter when used in a PV-battery pump system. [ABSTRACT FROM PUBLISHER]

Conventional matrix converters (MCs) have limited voltage gain that is less than 0.866, whether for direct MC (DMC) or indirect MC (IMC). Existing Z-source (ZS)/discontinuous quasi-Z-source (qZS) DMCs and ZS IMCs achieved larger than 0.866 voltage gain; however, the former inherited the complex commutation from DMC, and the latter involved a ZS network in dc link and led to non-all-silicon solution. In this paper, ZS and discontinuous qZS networks of existing ZS/qZS DMCs are used for an IMC topology for simplifying commutation and having high voltage gain, but they require extra input filter to reduce current harmonics. A new continuous qZS IMC is proposed, where a qZS network integrates the filtering function of the grid side; hence, additional input filter is avoided in the proposed continuous qZS IMC. Three new IMCs are compared in detail, in terms of voltage gain, current ripple, voltage ripple, inductor current and capacitor voltage stresses, ZS/qZS switch current and voltage stresses, filtering function, input current total harmonic distortion (THD), output voltage THD, and efficiency. Their control and modulation methods are presented to achieve the desired performances. Experimental comparisons verify the theoretical analysis and that the proposed continuous qZS IMC is a promising topology. [ABSTRACT FROM PUBLISHER]

Affected by the equivalent series resistance (ESR) of the devices in the circuit, the voltage-conversion ratio of traditional boost converter is limited. Various topologies have been developed to provide a high step-up voltage gain. An inherent high voltage gain can be achieved in a dual-switch converter with the advantages of low voltage and current stress on the switches. However, this converter has a strict requirement of the parameters' consistency. This paper discusses the steady-state operation principle of the converter in detail under the condition that the parameters are inconsistent and then illustrates the solutions to balance the voltage on the switches and suppress the resonance with passive lossless clamping. Finally, a prototype has been established in the laboratory, and simulation and experimental results have been given to verify the analysis and the effectiveness of clamping method. [ABSTRACT FROM PUBLISHER]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

In this paper, a passive ripple canceling circuit (PRCC) is proposed to eliminate the output power reduction effect of photovoltaic (PV) systems caused by the current ripple of the PV converters. Special features of the proposed PRCC include having low-cost simple modular structure and being independent of the duty ratio control of the main power circuit. Hence, it can be easily integrated to the main power circuit to achieve zero input current ripple, yielding less filter size, loss, and fast response. Meanwhile, the linear line maximum power point tracking (MPPT) control is also integrated with the proposed module integrated converter (MIC) to achieve instantaneous tracking response. Finally, a 90-W laboratory prototype is constructed to verify the effectiveness of the proposed principle. It is seen that the resulting peak-to-peak input current ripple is reduced to about 2% of the original dc converter input ripple. In other words, the input current ripple is almost zero. As a result, the harvested power of the proposed MIC can be increased by 7% as compared with that of the MIC without the proposed PRCC. [ABSTRACT FROM AUTHOR]

Natural balancing of the cell voltages is observed in many multilevel converters, however, this was not previously described for the modular multilevel converter (MMC). This paper introduces a method whereby the self-balancing behavior of the MMC can be described and analyzed. A novel equivalent circuit of the two cell single phase MMC is introduced whereby the unbalance in the system is clearly stated. Using this equivalent circuit a method, using the frequency domain as basis for analysis, is proposed whereby the self-balancing properties of the converter can be described. The method is verified through comparison with simulation results. [ABSTRACT FROM AUTHOR]

This paper presents a modulation strategy for symmetrical cascaded multilevel converters that simultaneously balances the individual DC voltages and reduces switching losses by eliminating redundant or unnecessary commutations. The voltage regulation is based on a 1-bit digital signal indicating whether the DC link voltage of each H-bridge is above or below the set point. The system command identifies commutations that can be suppressed without causing output voltage distortion, thus reducing converter losses. The voltage balancing is reached by postponing each switching commutation for a short lapse of time. Simulation and experimental results for an active filter application validate the proposed methods. [ABSTRACT FROM PUBLISHER]

An energy regenerative passive snubber for transformer isolated converters is proposed. The snubber is implemented on the transformer's primary and secondary windings. The proposed snubber significantly reduces the voltage spike across the switch caused by the transformer's primary inductance upon switch turn-off and facilitates the fast ramping up of the transformer secondary current. In addition, the proposed snubber provides lossless zero voltage turn off and zero current turn on conditions for the power switch. Experimental example of a flyback converter has shown measured efficiency exceeding 90%. This paper describes the principle of operation and presents approximate theoretical analysis and design guidelines of the proposed snubber. Simulation and experimental results are also reported. The proposed energy regenerating snubber is best suited for flyback and SEPIC converters and can also be adapted to other transformer isolated topologies. [ABSTRACT FROM AUTHOR]

This paper presents a boost converter with a proposed tapped inductor ripple cancellation network. Based on the conventional boost converter (CBC), a small capacitor and a small inductor are added as the ripple cancellation network (RCN) in the proposed converter. Meanwhile, the tapped inductor can be easily realized by adding an extra tap in the main inductor of the CBC. Since the capacitor and inductor in the RCN do not need to handle the main power as the conventional LC input filter, the size and weight of the proposed converter are relatively small comparing the CBC with the LC input filter. The small signal and dynamic characteristics analyses show that the proposed converter has the same static and dynamic responses as the CBC, and the input current ripple cancellation can be achieved in all power ranges without significantly increasing the losses. Finally, three 36–50-V, 500-W prototypes operating at 100 kHz are implemented to verify the expected performance. The simulation and experimental results show that the proposed converters can achieve input current ripple cancellation with efficiency higher than 97.4% in all power ranges. [ABSTRACT FROM PUBLISHER]

In this paper, novel topologies for symmetric, asymmetric, and cascade switched-diode multilevel converter are proposed, which can produce many levels with minimum number of power electronic switches, gate driver circuits, power diodes, and dc voltage sources. The number of required power electronic switches against required voltage levels is a very important factor in designing of multilevel converter, because switches define the reliability, circuit size, cost, installation area, and control complexity. For asymmetric and cascade converter, new algorithms for determination of dc voltage sources values are presented. To produce maximum number of levels at the output voltage, the proposed cascade topology is optimized for different goals, such as the minimization of the number of power electronic switches, gate driver circuits, power diodes, dc voltage sources, and blocking voltage on switches. Comparison of the results of various multilevel converters will be investigated to reflect the merits of the presented topologies. The operations of the proposed multilevel converters have been analyzed with the experimental and simulation results for different topologies. Verification of the analytical results is done using MATLAB simulation. [ABSTRACT FROM PUBLISHER]

This paper presents a single-phase transformerless grid-connected photovoltaic converter based on two cascaded full bridges with different dc-link voltages. The converter can synthesize up to nine voltage levels with a single dc bus, since one of the full bridges is supplied by a flying capacitor. The multilevel output reduces harmonic distortion and electromagnetic interference. A suitable switching strategy is employed to regulate the flying-capacitor voltage, improve the efficiency (most devices switch at the grid frequency), and minimize the common-mode leakage current with the help of a novel dedicated circuit (transient circuit). Simulations and experiments confirm the feasibility and good performance of the proposed converter. [ABSTRACT FROM PUBLISHER]

A family of dual-phase-combined resonant switched-capacitor (SC) converters with a similar structure is presented in this paper. Comparing with their conventional single-phase version, each of the proposed dual-phase converters is more than just a switched capacitor but also provides the service of two phases operated in the fully complementary manner. This design provides a more stable output voltage with low ripple and significantly reduces the quantity of switches. These converters therefore have the common features of smaller size, lower cost, and higher power density than the conventional multiphase SC converters. With the zero-current switching technique, the proposed converters also possess high-power conversion efficiency. The detailed analysis of the circuit operation and voltage ripples is presented. Experimental results are also provided to confirm the performance of the new family of converters. [ABSTRACT FROM AUTHOR]

In this paper, the built-in transformer voltage multiplier cell is inserted into each phase of the conventional interleaved boost converter to provide additional control freedom for the voltage gain extension without extreme duty cycle. The voltage multiplier cell is only composed of the built-in transformer windings, diodes and small capacitors. And additional active switches are not required to simplify the circuit configuration. Furthermore, the switch voltage stress and the diode peak current are also minimized due to the built-in transformer voltage multiplier cells to improve the conversion efficiency. Moreover, there is no reverse-recovery problem for the clamp diodes and the reverse-recovery current for the regenerative and output diodes are controlled by the leakage inductance of the built-in transformer to reduce the relative losses. In addition, the switch turn-off voltage spikes are suppressed effectively by the ingenious and inherent passive clamp scheme and zero current switch (ZCS) turn-on is realized for the switches, which can enhance the power device reliability. Finally, a 40 V-input 380 V-output 1 kW prototype is built to demonstrate the clear advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, a single-phase high step-up converter is proposed, designed not only to boost the relatively low photovoltaic (PV) voltage to a high bus voltage with high efficiency, but also to offer a neutral point terminal for the half-bridge-based inverters. First and foremost, two symmetrical high step-up converters are combined and integrated to derive an improved converter with neutral point terminal, which is strongly expected for the half-bridge-based inverters. Secondly, the voltage gain of the converter is extended and the narrow turn-off period is avoided by using the coupled inductor multiplier. Furthermore, the coupled inductor multiplier reduces the voltage stress of all the power devices. As a result, the low voltage-rated power devices can be employed to minimize the conduction losses. More importantly, all the active switches work in the zero-voltage-switching condition, which reduces the switching losses effectively. All these factors improve the circuit performance in the high step-up applications, especially for the half-bridge based PV inverter systems. Finally, the experimental results from a 500 W, 48 -760 V prototype at 100 kHz switching frequency are provided to verify the effectiveness of the proposed converter. The highest efficiency of the prototype is 96.5% and the efficiency is over 94% in a wide load range. [ABSTRACT FROM AUTHOR]

The interleaving technique is necessary for LLC resonant converters to achieve high power level. The advantages include expanded power capacity, lower output ripple current, and higher light-load efficiency by using phase shedding. However, conventional frequency-controlled LLC converters will lose regulation in individual phases if all the phases are operating at the same switching frequency, causing load sharing problem. Existing load sharing solutions for interleaved LLC converters all have limitations. In this paper, a switch-controlled capacitor (SCC) modulated LLC converter (SCC-LLC) is presented to solve the load-sharing problem. With constant switching frequency, interleaving and phase shedding can be achieved. A 600-W, two-phase interleaved constant frequency SCC-LLC prototype is built to verify the feasibility and demonstrate the advantages. [ABSTRACT FROM AUTHOR]

Electrostatic actuators are being widely investigated to convert electrical energy into mechanical deformation in a broad variety of microrobotic applications. Both electrostatic gap closing and comb drive actuators require high excitation voltages for high performance operation. In the majority of applications, external bulky and heavy power supplies are used to provide such high voltages, which inevitably bring limitations on autonomous operation. One of the major challenges toward enabling operation of these systems without a bulky external power source is the development of ultralight and high power density power electronic interfaces (PEIs) with large step-up gains. In this paper, a special circuit topology, controlled by a pulse frequency modulation scheme, is introduced to meet stringent electrical and drive voltage requirements of electrostatic actuators. An ultracompact 63 mg (excluding PCB mass), 31.5 mm 2, and 500 mW PEI has been designed and fabricated. Experimental validations have been carried out to verify the circuit's ability to drive an 110-V-input electrostatic inchworm motor at 1-kHz actuating frequency. [ABSTRACT FROM AUTHOR]

This paper describes a boundary-mode forward-flyback converter (BMFFC) with zero-voltage switching that is able to process power efficiently. The theoretical analysis and operating principle of the BMFFC are presented in detail. A nondissipative LC snubber that recycles energy to the input source is employed in order to suppress the voltage spike caused by the leakage inductance of the transformer. The relatively large snubber capacitor also significantly reduces turn-off loss. Following a detailed design procedure, a 200 W prototype with a 25-50 V dc input and 230 V dc output was constructed and tested in order to evaluate the performance of the BMFFC. [ABSTRACT FROM AUTHOR]

The voltage gain of traditional boost converter is limited due to the high current ripple, high voltage stress across active switch and diode, and low efficiency associated with large duty ratio operation. High voltage gain is required in applications, such as the renewable energy power systems with low input voltage. A high step-up voltage gain active-network converter with switched-capacitor technique is proposed in this paper. The proposed converter can achieve high voltage gain without extremely high duty ratio. In addition, the voltage stress of the active switches and output diodes is low. Therefore, low voltage components can be adopted to reduce the conduction loss and cost. The operating principle and steady-state analysis are discussed in detail. A prototype with 20-40-V input voltage, 200-V output voltage, and 200-W output power has been established in the laboratory. Experimental results are given to verify the analysis and advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, the charging precision of a 40-kW 3-kV soft-switching boost converter for capacitor charging is investigated. At the beginning, an overview on the topology and the control of the converter is given. Then, two different feedback controllers are presented and compared analytically to determine their sensitivity on noisy input variables. An algorithm to investigate the charging precision is illustrated. This algorithm considers the signal-to-noise ratio (SNR) of all measured signals, the controller output limitations, quantization related errors, the finite resolution in the digital domain, and the switching signal jitter to calculate the charging precision. All effects mentioned before are analyzed separately. This analysis shows that the output voltage measurement SNR is the key parameter for the charging precision. Then, measurements are performed to verify the model used to calculate the precision. These measurements show that the measured precision is only 6% higher than the precision predicted by the model for the used setup. Finally, the charging precision of the presented converter is analyzed including all considered effects. The repetition accuracy of the converter is determined to be 8.3 ppm at an output voltage of 3 kV, neglecting the load connection and the input voltage variation during one switching cycle. [ABSTRACT FROM PUBLISHER]

In this paper, a new fifth-order boost point of load converter is proposed, and then, a digital controller is designed using a Tchebyshev polynomial approach. The proposed converter has a reduced source ripple current together with a better boosting capability at lower duty ratios. Discrete-time models of the converter are formulated and then used in the identification of the direct digital controller stabilizing region. These discrete-time transfer functions are transformed into a Tchebyshev representation, consisting of converter control-to-output and controller transfer functions, which are then used to ascertain the existence of a stabilizing controller, and if stabilization is possible, then the entire set of gains is constructively determined. Using this method, the controller gain range is obtained as a set of inequalities in two variables for a fixed third variable. By sweeping the third variable over its entire range, the complete stabilizing sets are obtained. Within these ranges, the optimal digital controller parameters are obtained through a constrained optimization problem using a genetic algorithm. An integral time absolute error performance index is used in the optimization. A 30-W, 12- to 28-V, and 100-kHz laboratory prototype closed-loop converter has been developed and then tested, both as a simulation and experimentally, for its voltage regulation capability against source and load perturbations. Both the simulated and experimental results confirm the effectiveness of the proposed design. [ABSTRACT FROM PUBLISHER]

This paper presents a novel direct current-fed interleaved phase-modulated single-phase unfolding inverter for fuel-cell applications. Two active-clamped zero-voltage switching current-fed half-bridge isolated converters are interleaved in parallel input and series output configuration. Phase modulation is proposed to control these two converter cells, which generate a rectified sinusoidal pattern at the dc link. A simple H-bridge unfolding dc–ac inversion is used to produce single-phase sine voltage at line frequency switching using square-wave control. This not only simplifies the inversion stage in terms of modulation but also reduces the switching losses. Direct front-end current-fed based unfolding inverter is not reported in literature yet. Detailed analysis and design of the proposed direct current-fed single-phase unfolding inverter has been presented. Simulation waveforms using PSIM 9.0.4 are given to verify the presented analysis and design. Experimental results on a laboratory prototype rated at 200 W are demonstrated to support the investigation, to validate the accuracy of the proposed analysis and design, and to test the performance. [ABSTRACT FROM PUBLISHER]

This paper unifies the underlying concepts of all basic single-switch, two-state, dc-to-dc voltage-sourced converters, by duality, as generic related current and voltage-sourced converters. By using ac and dc circuit theory, the three basic converters can be transformed to yield all known transfer functions and realizes a proliferation of 33 topologies, three being previously unidentified topologies with unique characteristics. The circuit based systematic unifying approach offers new insight and an alternative interpretation to the origin of the 33 topologies including the Zeta, Cuk, \pmLuo, CSC, Landsman, and Sepic converters. Converter time-domain simulations and corresponding practical results of the three new topologies extol and culminate the concepts and analysis presented. [ABSTRACT FROM PUBLISHER]

This paper deals with the modeling and nonlinear control of modular multilevel converters. Two nonlinear coordinate transformations are introduced, which lead to a compact and clear representation of the differential equations. Two candidate outputs are discussed, which lead to an internal dynamics of second or third order, respectively. Only the second candidate output is analyzed further. For the corresponding internal dynamics, the conditions which ensure boundedness are examined. A quasi-static feedback leads to a linear input–output behavior. Simulations show the usefulness of the results. [ABSTRACT FROM PUBLISHER]

Single-inductor multiple-output (SIMO) dc–dc switching regulators are potentially very good replacement to multiple parallel converters in today's power management units for portable applications where multiple supplies are required. The outputs in these converters being coupled, cross-regulation among the outputs plays a major role in deciding the performance of the system. This paper proposes a control scheme that ensures good load and line regulation and stable system dynamics and reduces cross-regulation effect significantly. In designing a control scheme, proper analysis of the system is an important factor, and SIMO class of converters being driven by a ripple in the inductor current, conventional modeling does not hold good. Consequently, a ripple-based modeling approach that accurately judges the system performance is adopted. A cross-derivative state feedback control methodology has been proposed so as to completely decouple the outputs. Finally, a single-inductor dual-output SIMO converter has been built on a printed circuit board using discrete components, and the test results presented validate the modeling technique proposed. The simulation and experimental results show that the proposed control scheme significantly reduces cross-regulation at the outputs. [ABSTRACT FROM PUBLISHER]

A method for extending the duty cycle range of series-input interleaved forward converter (SII-FC) is proposed in this paper. A family of novel SII-FC topologies is derived by integrating two switching legs, which belong to two forward cells, into one switching leg shared by both the two forward cells in the SII-FC. By employing the proposed method, the derived topologies have the advantages of extended duty cycle, reduced components, and conduction losses, which help to achieve high power density and high efficiency. These advantages make the SII-FC topologies suitable for such applications with wide input voltage range. A series-input interleaved two-switch forward converter (SII-TS-FC) is analyzed in detail, which is a typical SII-FC topology developed by the proposed method. It is composed of two low-voltage switching legs and a high-voltage switching leg. Detailed analysis indicates that the maximum duty cycle of the SII-TS-FC can reach 2/3, which is 1.33 times of that of the two-switch forward converter. The switches of the high-voltage leg can be soft-switched when duty cycle is less than 0.5, while the switches of the low-voltage legs can be soft-switched when duty cycle is larger than 0.5. As a result, high efficiency is achieved over a wide voltage range. In addition, the output filter can be reduced due to the interleaving operation of the two forward cells. The operational principles, characteristics, and design considerations for the proposed SII-FC are presented. Experimental results on the SII-TS-FC prototype with 200–400 V input 48 V/12 A output verify the proposed method and analysis. [ABSTRACT FROM PUBLISHER]

This paper presents the hybrid seven-level cascaded active neutral-point-clamped (ANPC)-based multilevel converter. The converter topology is the cascaded connection of a three-level ANPC converter and an H-bridge per phase. The voltage of the H-bridge is actively maintained to the required level through selection of the switching states of the converter. The topology is operated under selective harmonic elimination pulsewidth modulation (SHE-PWM), maintaining the switching frequency of the converter to a minimum. The operating principles, voltage balancing methods, and limitations of the converter are analyzed together with extensive simulation results of the topology. Experimental results from a low-power laboratory prototype are presented that verify the operation of the hybrid converter under SHE-PWM. [ABSTRACT FROM PUBLISHER]

This paper proposes a zero-voltage switching (ZVS) pulsewidth modulation (PWM) dc/dc converter with current double rectifiers to achieve ZVS for all switches under a wide range of load conditions and input voltages. Two three-level PWM circuits sharing the same power switches are adopted in the proposed converter to reduce the voltage stress of each MOSFET at Vin/2 and achieve load current sharing. Thus, the current stress and power rating at the secondary-side components are reduced. The current double rectifiers are used at the secondary side to partially cancel the output ripple current. Thus, the sizes of the magnetic components and output filter capacitance are reduced. Due to the resonant behavior by the resonant inductance and resonant capacitance at the transition interval, all switches are turned on at ZVS. The experimental results based on a 1-kW prototype are provided to verify the operation principle of the proposed converter. [ABSTRACT FROM PUBLISHER]

A new scheme for nine-level voltage space-vector generation for medium-voltage induction motor (IM) drives with open-end stator winding is presented in this paper. The proposed nine-level power converter topology consists of two conventional three-phase two-level voltage source inverters powered by isolated dc sources and six floating-capacitor-connected H-bridges. The H-bridge capacitor voltages are effectively maintained at the required asymmetrical levels by employing a space vector modulation (SVPWM) based control strategy. An interesting feature of this topology is its ability to function in five- or three-level mode, in the entire modulation range, at full-power rating, in the event of any failure in the H -bridges. This feature significantly improves the reliability of the proposed drive system. Each leg of the three-phase two-level inverters used in this topology switches only for a half cycle of the reference voltage waveform. Hence, the effective switching frequency is reduced by half, resulting in switching loss reduction in high-voltage devices. The transient as well as the steady-state performance of the proposed nine-level inverter-fed IM drive system is experimentally verified in the entire modulation range including the overmodulation region. [ABSTRACT FROM PUBLISHER]

In this paper, a soft-switched dc–dc converter using voltage multiplier cells is proposed for high-step up application. The proposed converter has the following advantages: 1) doubled voltage conversion ratio of the basic configuration (N = 1) compared to the conventional boost converter; 2) zero voltage switching turn ON of switches and zero current switching turn OFF of diodes; 3) low input current ripple, reduced size of the passive component and current stresses of switches due to interleaved structure, and 4) increased flexibility in device selection by adjusting the number of voltage multiplier cells. The proposed converter is compared to some high step-up converters. Experimental results from a 1-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM PUBLISHER]

The photovoltaic (PV) technology has a small impact on the environment and is suitable for a wide range of applications. The main barrier for a more extensive implementation has been the reliability, mainly related to the power converters. According to this consideration, this paper presents an open-circuit fault diagnosis and fault-tolerant scheme for a three-level boost converter in a PV power system using batteries as storage devices. The fault diagnostic method takes advantage only of the control variables used for maximum power point tracking and output dc-link capacitor voltage balance. The fault-tolerant strategy requires only a few components added to the original three-level boost converter, so that, under an open-circuit power switch fault, it can be partly reconfigured into a two-level boost converter ensuring battery energy supply. Experimental results verify the proposed fault diagnostic method and reconfiguration for fault-tolerant operation. [ABSTRACT FROM AUTHOR]

An auxiliary capacitor-based balancing approach is adopted in this paper to equalize the dc-link capacitor voltages of a diode-clamped multilevel converter (DCMC). Four balancing circuits, including the generalized, one-level-capacitor, one-capacitor, and simplified one-capacitor-based configurations are discussed for a five-level DCMC system. These configurations are different in connection of the auxiliary circuits and numbers of the capacitors and switches, but they work on the same principle called ping-pong operation by utilizing the auxiliary capacitor as an equalizer between the capacitors of different voltages. The unbalance phenomenon, ping-pong principle, circuit configurations, and their switching schemes are analyzed, respectively. The superiorities of the proposed approach include balancing operation regardless of load power factor and modulation index, control simplicity, and independence from main circuits when compared to the traditional approaches. Simulations and experimental results verified the performances using the proposed balancing circuits and control strategies. [ABSTRACT FROM AUTHOR]

Voltage balance issue of dc-link capacitors is very important for applications of a cascade multilevel converter or a modular multilevel converter. In this paper, a novel diode-clamped modular multilevel converter (DCM2C) topology is proposed and a power feedback control method is developed. With the developed control strategy, the proposed diode-clamped circuit becomes a controllable closed loop which enables the capacitor voltages to be clamped by low power rating clamping diodes. The proposed topology and control strategy has quicker response and requires much fewer voltage sensors than the normally used traditional method; therefore, the system performance improvement and cost reduction are expected. Based on the proposed DCM2C, a novel N +1-level cascade multilevel topology is proposed for a cascade active power filter (CS-APF). The simulation and experimental results from the CS-APF have demonstrated and verified the effectiveness of the proposed novel topology and control method. [ABSTRACT FROM AUTHOR]

Recently, current source drivers (CSDs) have been proposed to reduce the switching loss and gate drive loss in megahertz (MHz) dc-dc converters, in which the duty cycle normally has a steady-state value. However, different from dc-dc converters, the duty cycle of the power factor correction (PFC) converters is modulated fast and has a wide operation range during a half-line period in ac-dc applications. In this paper, an adaptive full-bridge CSD is proposed for the boost PFC converters. The proposed CSD can build adaptive drive current inherently depending on the drain current of the main power MOSFET. Compared to the CSDs with the constant drive current, the advantage of the adaptive drive current is able to reduce the switching loss further when the MOSFET is with a higher switching current, while minimize the drive circuit loss when the MOSFET is with a lower switching current. Therefore, the adaptive CSD is able to realize better design tradeoff between the switching loss and drive circuit loss so that the efficiency can be optimized in a wide operation range. Furthermore, no additional auxiliary circuit and control are needed to realize the adaptive current by the proposed CSD. The experimental results verified the functionality and advantages. For a 1-MHz/300-W boost PFC converter, the proposed CSD improves the efficiency from 89% using a conventional voltage driver to 92.2% (an improvement of 3.2%) with 110 Vac input, 380 V output, and full-load condition. [ABSTRACT FROM AUTHOR]

This paper describes the design of a nonlinear controller with power sharing control capabilities of a double input buckboost-buckboost converter. First, this converter is introduced, and its principles of operation and the equations describing the converter circuit are reviewed. Next, the nonlinear model of the buckboost-buckboost converter is found by averaging the state equations. Then, a Lyapunov-based nonlinear controller, which is adaptive against input voltage and load disturbances (to provide line regulation and load regulation) is proposed. Finally, several simulation and experimental results from a prototype buckboost-buckboost converter operating under the proposed controller are reported to verify the operation of the designed controller. [ABSTRACT FROM AUTHOR]

Effective photovoltaic power conditioning requires efficient power conversion and accurate maximum power point tracking to counteract the effects of panel mismatch, shading, and general variance in power output during a daily cycle. In this paper, the authors propose an integrated boost resonant converter with low component count, galvanic isolation, simple control, as well as high efficiency across a wide input and load range. Provided is a discussion of the converter synthesis, key operational features, converter design procedure, and loss analysis, as well as experimental verification by way of a 250-W prototype with a California Energy Commission efficiency of 96.8%. [ABSTRACT FROM AUTHOR]

This paper discusses the theory and implementation of a class of distributed power converters for photovoltaic (PV) energy optimization. Resonant switched-capacitor converters are configured in parallel with strings of PV cells at the sub-module level to improve energy capture in the event of shading or mismatch. The converters operate in a parallel-ladder architecture, enforcing voltage ratios among strings of cells at terminals normally connected to bypass diodes. The balancing function extends from the sub-module level to the entire series string through a dual-core cable and connector. The parallel configuration allows converters to handle only mismatch power and turn off if there is no mismatch in the array. Measurement results demonstrate insertion loss below 0.1% and effective conversion efficiency above 99% for short-circuit current mismatch gradients up to 40%. The circuit implementation eliminates large power magnetic components, achieving a vertical footprint less than 6 mm. The merits of a resonant topology are compared to a switched-capacitor topology. [ABSTRACT FROM AUTHOR]

Induction heating (IH) technology is nowadays widely present in domestic appliances because of its cleanness, high efficiency, and faster heating process. All of these advantages are due to its heating process, where the pot is directly heated by the induced currents generated with a varying magnetic field. As a result, the glass where the pot is supported is not directly heated and, consequently, efficiency and heating times are improved. IH systems are based on dc-link inverters to generate the required alternating current to feed the inductor. Usually, resonant converters are used to achieve higher efficiencies and power densities. In such systems, the maximum output power and efficiency are achieved at the resonant frequency, and the switching frequency is increased to reduce the output power. As a consequence, in these converters, the efficiency is also reduced in the low-medium output power range. This paper proposes the use of the half-bridge inverter in two operating modes to achieve higher efficiency in a wide output power range. The power converter topology can be reconfigured by changing the resonant capacitors through electromechanical relays. As a consequence, the entire efficiency of the cooking process is improved with a cost-effective procedure. [ABSTRACT FROM AUTHOR]

In this paper, the concept of built-in transformer voltage doubler cell is derived to generate an improved interleaved high step-up converter for distributed photovoltaic generation applications. The proposed built-in transformer voltage doubler cell is composed of three transformer windings, two voltage doubler diodes, and two voltage doubler capacitors. The voltage doubler capacitors are charged and discharged alternatively to double the voltage gain. The switch duty cycle and the transformer turns ratio can be employed as two controllable freedoms to lift the voltage ratio flexibly. The power device voltage stress can also be reduced to improve the circuit performance. Furthermore, the active clamp scheme is adopted to recycle the leakage energy, absorb the switch turn-off voltage spikes, and achieve zero-voltage switching (ZVS) operation for all active switches. Meanwhile, the diode reverse-recovery problem is alleviated by the leakage inductance of the built-in transformer. All these factors benefit the circuit performance improvements in the high step-up and large current applications. Finally, a 1-kW prototype with 40-380 V conversion is built and tested to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

The LLC resonant converter has drawn much attention for high efficiency. However, its light-load efficiency still cannot meet the ever increasing requirements. This paper proposes a novel burst-mode control for the LLC resonant converter to improve the light-load efficiency. Based on the state-plane trajectory analysis, during the burst-on time, a three-pulse switching pattern is implemented. By optimizing the first pulse width, the state variables are settled to the steady state of the highest efficiency load in the minimal time, and then, the next two pulse operation follows this steady-state trajectory to achieve high burst efficiency. Moreover, when the load changes, the burst-on time with the optimal three-pulse switching pattern is maintained, but the burst-off time is modulated. As a result, the output-voltage low-frequency ripple minimally keeps constant, and no additional filter is needed. Experimental results validate the proposed techniques. [ABSTRACT FROM AUTHOR]

This paper presents a new standby structure where a forward converter is integrated with a dc-dc phase-shift full-bridge (PSFB) converter for server power supplies. While a typical standby structure consists of an independent flyback converter, the proposed standby structure is integrated with one leg of the dc-dc PSFB converter. Its main advantages are that the voltage across a standby switch is clamped at the link voltage across the link capacitor and that the standby switch achieves zero-voltage switching over entire load range. The validity of the proposed standby structure is confirmed by the experimental results from 12 V/58 A for the dc-dc output prototype and 11.5 V/1.5 A for the standby output prototype. [ABSTRACT FROM AUTHOR]