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In this paper, a single-inductor dual-output (SIDO) dc–dc converter is proposed. The significant feature of the proposed converter is feeding a constant power load in low-voltage side (LVS) port, where even feeding a variable load at LVS does not have any cross regulation to high-voltage side port with the desired approximation. Magnificently, both merits are obtained in open-loop manner, which is an outstanding characteristic in comparison with that of the existed converters. In this paper, soft commutation and soft switching of switches and diodes are investigated along with the aforementioned main novelty. Moreover, detailed theoretical analyses of the proposed SIDO dc–dc converter in continuous conduction mode are presented besides the comparisons with some other structures. Finally, theoretical analyses are verified through a 1500 W experimental prototype results. [ABSTRACT FROM AUTHOR]

Thanks to the favorable advantage of low cost, integrated three-port dc–dc converters with reduced switches have attracted extensive attention. In order to provide more new topologies, this paper aims to propose a programmable topology derivation method, which effectively simplifies the cumbersome process of the conventional combination method. Instead of the manual connection and examination, the proposed alternative can quickly and rigorously derive multiple viable integrated three-port dc–dc topologies from a great number of possible connections with the aid of computer program. Besides, generalized analysis is also accomplished, with which performance characteristics of all derived converters are simultaneously obtained and then a comprehensive comparison can be easily conducted to select a preferred one for the practical application. Finally, an example-specific application with one input and two outputs is given, with topology selection, design, and experimental results demonstrated in detail. [ABSTRACT FROM AUTHOR]

In this paper, performances on two kinds of aggregated flyback microinverters are compared in aspect of harmonic resonances, which are controlled by current feedback control and peak current control. Based on the Norton models of flyback microinverters obtained by a small-signal modeling approach, potential harmonic resonances with the grid are analyzed. Following that, an impedance-based stability criterion is proposed, where the resonance frequency can be calculated and predicted based on the derived Norton models and the system admittance matrix of aggregated microinverters. After comprehensive analysis and comparisons, it is found that the peak-current-control-based flyback microinverters has better performance on damping the harmonic resonances than the current feedback controlled one. Simulations and experiments are carried out for verifying the effectiveness of the presented models and the correctness of the analysis results. [ABSTRACT FROM AUTHOR]

In this paper, the remedial operation of switch faults will be investigated comprehensively for T-type-three-level-inverter-fed dual three-phase motor drives. The open-circuit switch faults in multiple phase legs are discussed at first. The faulty conditions are classified into five categories. Different remedial strategies, namely Type-I to Type-V schemes, are proposed for different faulty conditions. In particular, three kinds of Type-III fault-tolerant control schemes are proposed by using medium-voltage vectors to synthesize small-voltage vectors, in such a way that the mid-point voltage in a dc link can be stabilized well. Then, the short-circuit faults in both clamping switches and half-bridge switches are investigated. By analysis, their operation conditions are equivalent to conditions loss of both P and N voltage levels and open-phase faults, respectively. Thus, the corresponding remedial strategies can be applied accordingly. Particularly, a voltage compensation control method is proposed for conditions, where open-switch faults coexist with open-phase operation induced by short-circuit faults in half-bridge switches. The validity of all of theoretical analysis and the proposed remedial strategies has been verified by experiments. [ABSTRACT FROM PUBLISHER]

In this paper, a single-phase multilevel ac/ac converter with reduced number of power semiconductor devices is proposed. For the simple case of a three-level converter, only three bidirectional switches and two capacitors are required. The proposed converter provides a highly sinusoidal and regulated output voltage with a simple topology. The efficiency is high because in each state of operation only one semiconductor conducts. The converter can be easily extended to any desired levels in the output voltage to even more reduce the output total harmonics distortion. Another advantage of the proposed converter is that by increasing the voltage levels, the stress on the switches will decrease. The proper performance of the proposed converter is confirmed through extensive simulation and experimental tests. [ABSTRACT FROM PUBLISHER]

A new approach for modulation of an 11-level cascade multilevel inverter using selective harmonic elimination is presented in this paper. The dc sources feeding the multilevel inverter are considered to be varying in time, and the switching angles are adapted to the dc source variation. This method uses genetic algorithms to obtain switching angles offline for different dc source values. Then, artificial neural networks are used to determine the switching angles that correspond to the real-time values of the dc sources for each phase. This implies that each one of the dc sources of this topology can have different values at any time, but the output fundamental voltage will stay constant and the harmonic content will still meet the specifications. The modulating switching angles are updated at each cycle of the output fundamental voltage. This paper gives details on the method in addition to simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes an alternative strategy of finite-control-set model-predictive torque control (MPTC) to reduce the computational burden and the torque ripple and decouple the switching frequency from the controller sampling time. An improved discrete space-vector modulation (DSVM) technique is utilized to synthesize a large number of virtual voltage vectors. The deadbeat (DB) technique is used to optimize the voltage vector selection process, avoiding enumerating all the feasible voltage vectors. With this proposed method, only three voltage vectors are tested in each predictive step. Based on the improved DSVM method, the three candidate voltage vectors are calculated by using a novel algebraic way. This new strategy has the benefits of both the MPTC method and the DB method. The effectiveness of the proposed strategy is validated based on a test bench. [ABSTRACT FROM PUBLISHER]

In this paper, a new cascade switch-ladder multilevel inverter topology is presented which can generate a large number of output voltage levels. First, a fundamental switch-ladder multilevel inverter structure is described. Then, the structure of recommended cascade topology based on series connection of fundamental switch-ladder topologies is presented. To generate maximum number of levels with minimum number of switching elements, dc sources, and voltage on switches, the proposed cascade topology is optimized. Comparison results prove that the presented cascade topology requires fewer numbers of components. Also, the value of voltage rating on switches is less than other structures. Experimental results for two topologies are analyzed to verify the performance of the proposed topology. [ABSTRACT FROM PUBLISHER]

This paper proposes a new space-vector pulsewidth modulation (SV-PWM) strategy for a three-level neutral point clamped inverter. The presented SV-PWM strategy makes it possible to control the neutral point voltage by optimum choice of switch sequence for any position and length of output voltage vector. The proposed solution takes into consideration the unbalance of the dc-link voltages. It also analyzes the influence of vector sequences on the predicted unbalance of the dc-link voltage. The solution allows selecting optimum vectors and their on-time durations in order to reduce quickly the dc-link voltage unbalance. The calculation of the space vector area proposed in this paper takes into consideration voltage unbalance and its influence on the length and position of vectors. The proposed approach assures properly generating the voltage output vectors, even in the case of the existing large voltage unbalance in the dc-link. The results of the experimental investigation of the proposed modulation strategy are presented in this paper. [ABSTRACT FROM PUBLISHER]

Multilevel power electronic converters have gained popularity in high-power applications due to their lower switch voltage stress and modularity. Cascaded H-bridge converters are a promising breed of multilevel converters which generally require several separate dc voltage sources. By utilizing the redundant switching states, it is possible to replace the separate dc voltage sources with capacitors and keep only the one with the highest voltage level. Redundancy in the charge and discharge modes of the capacitors is assumed to be adequate for their voltage regulation. However, the effects of the output current of the converter as well as the time duration of the redundant switching states have been neglected. In this paper, the impacts of the connected load to the cascaded H-bridge converter as well as the switching angles on the voltage regulation of the capacitors are studied. This paper proves that voltage regulation is only attainable in a much limited operating conditions that it was originally reported. In addition, based on the analysis of the converter, a simplified formula is found which can be used to find those modulation indices that regulate the voltage of the capacitor. This formula can be used in harmonic minimization problems while capacitor voltage regulation is ensured. Simulation and laboratory results are provided to confirm the analysis. [ABSTRACT FROM PUBLISHER]

This paper presents a novel topology for a direct ac–ac power converter, called as the “three-to- k” phase matrix converter. The input to the proposed matrix converter configuration is a three-phase fixed voltage and a fixed frequency supply from the grid. The output is a variable voltage and variable frequency ac supply of any number of phases (k phase). However, the discussion is limited here for a k that is equal to odd number of phases. As an example, a “three-to-five” phase matrix converter is utilized for discussion and analysis. This paper also proposes two pulsewidth modulation (PWM) control techniques for the general topology of the “three-to- k” phase matrix converter. This is based on the so-called direct duty ratio PWM (DPWM). In one presented technique, the output voltage is limited to one half of the input voltage. For the other proposed scheme, the output voltage is enhanced to 78.86% of the input voltage. The proposed control algorithm is validated using simulation and an experimental approach. [ABSTRACT FROM AUTHOR]

This paper presents a current soft-commutation pulsewidth modulation (PWM) scheme for three-phase current source converter. With the presented PWM scheme, the incoming switch has a positive collector-to-emitter voltage while the outgoing switch has a negative collector-to-emitter voltage during current commutations. Therefore, natural soft commutations for switching transitions are achieved, while current-commutating durations are also lessened. Moreover, some particular advantages can also be obtained such as reduced switching frequency, high dc current utilization ratio, and in-phase transfer between line currents and their references. For more efficient control, this paper then designs logic equations for mapping out the assignments from references to gating signals, allowing a simple implementation using a digital signal processor or a programmable logic device. The theoretical analysis is verified by experimental results. [ABSTRACT FROM AUTHOR]

Most variable-speed ac generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix converters (MCs) are a good alternative to back-to-back converters because they have several advantages in terms of size and weight. Therefore, MCs can be advantageously used in any variable-speed generation system where high efficiency, reliability, small size, and low weight are considered important factors. Nevertheless, to interface an MC-based generation system to an unbalanced 3\phi stand-alone load, a four-leg MC is required to provide a path for the zero-sequence load current. Space-vector-modulation (SVM) algorithms for the operation of four-leg MCs have been proposed in the literature. However, these modulation methods have high computational burdens, and they are difficult to implement, even in fast DSP-based control platforms. Therefore, only simulation results have been reported in these publications. In this paper, an SVM algorithm is optimized and experimentally tested. Moreover, the harmonics produced in the input current when a four-leg MC is feeding an unbalanced or nonlinear load are also mathematically analyzed in this paper, with experimental verification being provided. [ABSTRACT FROM AUTHOR]

In this paper, a new post-fault modulation strategy is proposed to operate the direct matrix converter as close as possible to its desired normal operation under an open-switch fault condition. The proposed strategy determines appropriate switching states associated with eight, out of the nine, remaining healthy switches of the converter, to synthesize the reference voltages. The corresponding duty cycles of the determined switching states are calculated by formulating a nonlinear optimization problem that aims at minimization of the error between the desired reference voltages and the voltages generated by the switching states. The solution to the nonlinear optimization problem is obtained based on the Karush–Kuhn–Tucker conditions. The performance of the proposed modulation strategy is evaluated based on time-domain simulation studies in the MATLAB/Simulink software environment and also experimentally verified. [ABSTRACT FROM PUBLISHER]

In this paper, a high-conversion-ratio bidirectional dc–dc converter with coupled inductor is proposed. In the boost mode, two capacitors are parallel charged and series discharged by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stress on the main switch is reduced by a passive clamp circuit. Therefore, the low resistance R{DS(ON)} of the main switch can be adopted to reduce conduction loss. In the buck mode, two capacitors are series charged and parallel discharged by the coupled inductor. The bidirectional converter can have high step-down gain. Aside from that, all of the switches achieve zero voltage-switching turn-on, and the switching loss can be improved. Due to two active clamp circuits, the energy of the leakage inductor of the coupled inductor is recycled. The efficiency can be further improved. The operating principle and the steady-state analyses of the voltage gain are discussed. Finally, a 24-V-input-voltage, 400-V-output-voltage, and 200-W-output-power prototype circuit is implemented in the laboratory to verify the performance. [ABSTRACT FROM PUBLISHER]

A lot of large-scale industrial critical loads suffer from voltage interruptions and sags which can cause a significant financial loss. The thyristor-based solid-state transfer switch (STS) and mechanical-based automatic transfer switch (ATS) are used to protect loads against these power quality problems. However, the STS has a great deal of loss consumption because of the forward voltage drop of the thyristors, and ATS can hardly satisfy the voltage-sensitive load due to the long transfer time. This paper proposes a 400 V/1000 kVA hybrid ATS (thyristor switch in parallel with mechanical switch) (HATS) to realize low power consumption under normal situation and transfer fast when required. The proposed HATS has four transfer strategies which can be chosen according to different applications, it realizes the overlapping transfer of the neutral wire, and it can make a decision to transfer or not according to the different fault locations (transfer on the source side and not transfer on the load side). The design details of the prototype are presented, and laboratory tests and field experiments show the prototype good performance. [ABSTRACT FROM PUBLISHER]

Multilevel converters have received increased interest recently as a result of their ability to generate high quality output waveforms with a low switching frequency. This makes them very attractive for high-power applications. A cascaded H-bridge converter (CHB) is a multilevel topology which is formed from the series connection of H-bridge cells. Optimized pulse width modulation techniques such as selective harmonic elimination or selective harmonic mitigation (SHM-PWM) are capable of preprogramming the harmonic profile of the output waveform over a range of modulation indices. Such modulation methods may, however, not perform optimally if the dc links of the CHB are not balanced. This paper presents a new SHM-PWM control strategy which is capable of meeting grid codes even under nonequal dc link voltages. The method is based on the interpolation of different sets of angles obtained for specific situations of imbalance. Both simulation and experimental results are presented to validate the proposed control method. [ABSTRACT FROM PUBLISHER]

Improved pulse regulation (IPR) control, a novel control technique for switching dc–dc converters, is proposed and studied in this paper. According to the output voltage and load current of the switching dc–dc converter, IPR control technique achieves output voltage regulation by generating control pulse train made up of some preset control pulses with different duty ratios. IPR control needs only comparators, triggers, and some simple logic devices, without error amplifier and the corresponding compensation circuit of pulse width modulation control scheme, thus IPR control scheme is easy to realize, benefits with excellent transient performance and stability. The principle and operation of IPR control scheme are introduced and illustrated with buck converter operating in discontinuous conduction mode as an example. Simulation and experimental results are presented to show that IPR-controlled converter has much lower output voltage ripple and more accurate output voltage regulation than PR converter. [ABSTRACT FROM PUBLISHER]

In this paper, two reduced switch count topologies are introduced for independently supplying two single-phase ac loads with one inverter. Using a new three-switch leg structure recently introduced and implemented in three-phase converters, two types of dual-leg and single-leg topologies are developed which respectively are functionally comparable to two full-bridge and half-bridge inverters working independently though with a less number of semiconductor switches and hence control and gate drive circuit components. The proposed six-switch and three-switch topologies are introduced; two modes of equal frequency and different frequency operation each of its own distinctive characteristics are considered for them and their pulse width modulation schemes are elaborated. Comprehensive analyses of power loss profile and output waveform properties are conducted via simulation for the proposed inverters, and the results are compared with full-bridge and half-bridge inverters. To assess the performance of the proposed inverter topologies, working prototypes are built, and the experimental results are provided. [ABSTRACT FROM PUBLISHER]

In this paper, an energy-based Lyapunov function control technique is developed for a three-phase shunt hybrid active filter (SH-AF) to compensate harmonics generated by nonlinear loads and is applied for balanced operation. The method provides compensation for harmonic load current components. The strategy determines the control law that makes the derivative of the Lyapunov function always negative for all values of the states. The dc bus voltage of the SH-AF is maintained to 50 V, which is significantly lower than that of the conventional hybrid active filter. The rating of the active filter in the SH-AF system is much smaller than the one used in the conventional shunt active power filter because the passive filter takes care of the major burden of compensation. The SH-AF performances, during both nominal and severe operating conditions, are then evaluated using a dSPACE DS1104 controller board, supported by a Matlab/Simulink Real-Time Workshop environment. A significantly high correlation between the experimental results and the theoretical model, implemented with Simulink/Matlab, is obtained. [ABSTRACT FROM PUBLISHER]

In this paper, two space-vector-based pulsewidth modulation (PWM) (SVPWM) strategies named equal- and proportional-duty SVPWMs are described, which are used to synthesize a four-level waveform from an open-end winding configuration of an induction motor. Two isolated dc-link voltages, which are in the ratio of 2 : 1, are employed to achieve this objective. Both of these PWM strategies achieve the avoidance of overcharging of the dc-link capacitor of an inverter operating with lower dc-link voltage by its counterpart with higher dc-link voltage. Implementation of these PWM strategies requires only the instantaneous three-phase reference voltages, eliminating the need of sector identification or lookup tables. The numbers of samples per cycle for individual inverters are selected in such a way that the quarter-wave, half-wave, and three-phase symmetries are achieved for the dual-inverter drive despite unequal dc-link voltages for the constituent inverters. It is also shown that one of the two PWM techniques, called the proportional-duty SVPWM, results in a better spectral performance and lower switching power loss in the overall dual-inverter system compared to the equal-duty SVPWM. [ABSTRACT FROM PUBLISHER]

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes. [ABSTRACT FROM AUTHOR]

An active-clamp forward (ACF) converter, which is popular in low-to-medium power applications, suffers from the high-voltage stress on switches, i.e., the sum of input voltage and reset capacitor voltage. To relieve this problem, a two-switch (2-SW) ACF converter, where the voltage stresses on the main switches are clamped to either the input voltage or the reset capacitor voltage by simply employing one clamping diode and a delayed turnoff gate signal, is proposed in this paper. Therefore, in view of utilizing high-performance low-voltage switches, the proposed 2-SW ACF converter can be promising for high-input-voltage applications. [ABSTRACT FROM AUTHOR]

A five-level flying-capacitor (FC)-based active-neutral-point-clamped (ANPC) converter is an arrangement of a three-level ANPC converter and a two-level cell. In this paper, a control strategy is proposed to regulate the voltage across the FCs at their respective reference voltage levels by swapping the switching patterns of the switches based on the polarity of the output current, the polarity of the FC voltage, and the polarity of the fundamental line-to-neutral voltage under selective harmonic elimination pulsewidth modulation. The voltage across the FCs and the dc-link capacitors are simultaneously controlled at their reference voltage levels. The proposed control strategy is applied using power system computer aided design/electromagnetic transients including dc on a static synchronous compensator operating under a power-factor-correction mode to verify its performance. Experimental results are also presented for low and high number of angles per quarter period using a low-power laboratory prototype. [ABSTRACT FROM AUTHOR]

In this paper, a new three-level (3L) converter is presented. It is called 3L Vienna neutral-point-clamped (3L-VNPC) converter and consists of two stacked high-frequency (HF) commutation cells working with a shared power device. The HF cells are connected to a single-phase switched bridge controlled at low frequency. The 3L-VNPC topology is extended to 3L active VNPC (3L-AVNPC) concept, which is generalized for five levels (5L) and N odd voltage levels (N \L). The proposed multilevel converters can be seen as two cascaded voltage stages. The high-voltage stage is specific to the single-phase switched bridge, while the low-voltage (LV) stage corresponds to the stacked HF cells with shared power devices. The new concept AVNPC is a useful and suitable solution for medium-voltage applications, where small modulation index (M) is as crucial as large M. The analyses of the new converters are verified by simulations both for 3L and for 5L topologies, and their features are generalized for N\L. Experimental results for single-phase 3L-AVNPC converter on an LV test bench are also provided to validate the proper operation of the new concept. [ABSTRACT FROM AUTHOR]

With regard to a five-level inverter comprising flying-capacitor asymmetric H-bridge, the impact on the capacitor voltage under conventional modulation approach is analyzed. Since it is sensitive to the fundamental period and the load current, it may introduce undesired low-order harmonics into the output voltage and may even break down the power switches due to the considerable fluctuation of the flying-capacitor voltage. Thus, this paper proposes a novel pulsewidth-modulation scheme with the positive and negative cross carriers, which controls the flying-capacitor voltage by utilizing the redundant switching states of the output voltages. Three modes of precharging the flying capacitor without extra equipments are presented. Moreover, the capacitance of the flying capacitor and the switching frequency of the power switches can be chosen according to the allowable fluctuation of the flying-capacitor voltage and the load current. In order to remove the overlapping of the level layers, the optimization of the line-to-line voltage waveform is proposed to synthesize the reference vector with the “nearest three-vector” approach. The theory is supported by the experimental results from the prototype. [ABSTRACT FROM AUTHOR]

In this paper, a novel high step-up dc–dc converter with coupled-inductor and voltage-doubler circuits is proposed. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switches. Also, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output. The operating principles and the steady-state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit of the proposed converter is implemented in the laboratory to verify the performance of the proposed converter. [ABSTRACT FROM AUTHOR]

A novel pseudo-continuous conduction mode (PCCM) boost power-factor-correction (PFC) converter and its corresponding control strategy are proposed in this paper. Connecting a power switch in parallel with the inductor makes the boost converter operate in PCCM, which provides an additional degree of control freedom to realize PFC control. Therefore, a simple and fast voltage control loop of the PCCM boost PFC converter can be designed to realize output-voltage regulation. The additional degree of control freedom introduced by inductor current freewheeling operation of the PCCM boost PFC converter has been exploited through the dead-zone control technique, which can be dynamically adjusted in accordance with the output-voltage ripple. Compared with continuous conduction mode (CCM) boost PFC converter, the controller of the proposed PCCM boost PFC converter is much simpler. Moreover, the PCCM boost PFC converter benefits with reduced inductor-current ripple and improved power factor compared with boost PFC converter operating in discontinuous conduction mode (DCM). Analysis, simulation, and a 400-W prototype of the PCCM boost PFC converter have been presented and compared with those of boost PFC converters operating in conventional CCM and DCM. The results show that the dynamic response of the PCCM boost PFC converter is significantly faster than the existing boost PFC converter. [ABSTRACT FROM AUTHOR]

This paper presents the analysis, development, and implementation of a wavelet modulation (WM) technique for three-phase voltage-source (VS) six-pulse inverters. The WM technique is based on sampling three continuous-time (CT) sinusoidal reference modulating signals in a nonuniform recurrent manner using three sets of scale-based linearly combined wavelet basis functions. These CT signals are recovered from their samples by a three-phase VS six-pulse inverter, which is activated by three sets of synthesis scale-based linearly combined wavelet basis functions. Each set of synthesis basis functions is generated for activating one leg of the three-phase inverter in order to recover one CT reference modulating signal. The WM technique is implemented for both simulation and experimental performance testing. The performances of the WM technique are compared with those obtained using the space vector modulation, random pulsewidth modulation, and hysteresis band current control techniques under the same loading conditions. Simulation and experimental test results show that the proposed WM technique is able to switch a three-phase VS six-pulse inverter to produce outputs with significantly improved fundamental components and low harmonic contents. [ABSTRACT FROM PUBLISHER]

This paper proposes an energy regeneration circuit for three-phase voltage-fed inverters using a modified Undeland snubber. The proposed system uses a quasi-square-wave zero voltage switching dc–dc auxiliary converter to regenerate the energy from snubber capacitor to the dc bus. The regenerative circuit uses a single active switch, and it operates independently of the three-phase inverter. Operation stages, theoretical waveforms, and a design methodology are presented. Experimental results based on a 4.5-kVA three-phase inverter prototype are included to validate the proposed topology. [ABSTRACT FROM PUBLISHER]

A dynamic overmodulation strategy for fast dynamic torque control in direct torque control (DTC)-hysteresis-based induction machine is proposed. The fastest dynamic torque response with a six-step mode can be achieved in the proposed method by switching only the most optimized voltage vector that produces the largest tangential component to the circular flux locus. This paper also discusses the performance of dynamic torque control in basic DTC in order to justify on how the proposed selected voltage vector results in excellent dynamic torque performance. The main benefit of the proposed method is its simplicity, since it only requires a minor modification to the conventional DTC-hysteresis-based structure and does not require a space vector modulator. To verify the feasibility of the proposed dynamic overmodulation strategy, simulation and experimentation, as well as comparison with the conventional DTC scheme, are carried out. Results showed a significant improvement in the dynamic torque response when compared to the conventional DTC-hysteresis-based method. [ABSTRACT FROM PUBLISHER]

Predictive control techniques have recently been applied with success to conventional and multiphase electrical drives. The additional degrees of freedom in multiphase drives make the real-time implementation of optimal solutions difficult due to the increased number of iterations. This paper proposes a predictive control technique that reduces the available voltage source inverter switching states according to predefined constraints. The introduced method, called as restrained search predictive control, favors on-line implementation and improves the current tracking performance. Simulation and experimental results are provided to test the viability of the presented technique. [ABSTRACT FROM PUBLISHER]

This paper presents a flyback switch-mode rectifier (SMR) with spread harmonic spectrum. The SMR switching control is conducted by a charge-regulated pulsewidth modulation (PWM) scheme with constant turn-on period. The inherently stable discontinuous conduction mode operation is preserved to yield good line drawn power quality. In voltage loop, a quantitatively designed PI feedback controller is augmented with a robust error cancellation control scheme. Further improved dc output voltage regulation and input power quality performances are achieved under varied operating conditions. In spread harmonic spectrum control, the harmonic spectral properties of the developed flyback SMR are first analyzed. Then, the dedicated random switching scheme is developed to let its switch current harmonic spectrum be dispersedly distributed. In the proposed random switching scheme, the PWM turn-off period is modulated using 1-b binary sequence, pseudo random binary sequence, and 4-b binary sequences. Under randomized harmonic spectrum, the SMR control performances are not sacrificed. [ABSTRACT FROM PUBLISHER]

This paper presents an optimal control scheme for a multilevel inverter working for audio power amplification. The proposed control scheme comprises two loops of feedback around a sliding-mode quantizer. The double-loop feedback generates a continuous equivalent control signal, while the quantizer that operates in the sliding mode converts the equivalent control signal into a staircase voltage waveform used to drive a loudspeaker through an LC filter for audio signal tracking. The control scheme is optimized to reduce the frequency weighted tracking error and the equivalent control signal simultaneously, compromising between a satisfactory performance and a wide stable input range. With the proposed design, a nine-level class-D audio amplifier is built and tested, which exhibits high-robustness and high-quality audio reproduction. [ABSTRACT FROM AUTHOR]

A high step-up conversion-ratio converter with soft switching is presented in this paper. By using both coupled inductors and isolated transformer, high voltage gain can be easily achieved without extremely high duty ratio. To deal with switching losses, the active clamping circuit is adopted to achieve the zero-voltage-switching turn-on feature for power switches and to absorb the energy stored in the leakage inductor. Moreover, the series-resonant tanks composed by leakage inductors of the transformer and resonant capacitors are used to achieve the zero-current-switching turn-off feature for rectifier diodes at the output side. Therefore, the turn-on switching loss of power switches and the reverse-recovery problem of rectifier diodes can be eliminated. The operational principles and design consideration are discussed in detail. Finally, experimental results taken from a 400-W prototype are presented to confirm the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper suggests an isolated dc/dc converter using an unregulated LLC converter for fuel cell applications. The LLC converter operates as an isolated voltage amplifier with a constant voltage gain, and a nonisolated converter installed in the input stage regulates the output voltage under a wide variation of fuel cell stack voltage. By separating the functions, the unregulated LLC converter can be operated at an optimal switching condition, and the high-frequency operation of 300 kHz can be accomplished without introducing an excessive switching loss. The prototype converter with a 1-kW design (Vin = 24 \sim 48\ \V/Vo = 400\ \V) shows an efficiency of above 90.2% under a 24-V input and full load conditions. [ABSTRACT FROM AUTHOR]

This paper describes a novel switching signal generator for three-phase voltage source inverters. Unlike conventional space-vector pulsewidth modulation (SVPWM) which achieves three-phase input voltage by a combination of the basic space vectors, the proposed scheme produces optimal switching commands to minimize the filtered measure of quantization error. Under specific selections of the filter matrix and the quantization scheme, it is shown that the proposed modulator is equivalent to SVPWM. An experimental platform is built to verify the effectiveness of the proposed scheme. It is shown that the switching number of the proposed method is reduced without sacrificing the harmonic distortion within the input frequency band under various reference signals. [ABSTRACT FROM AUTHOR]

A dual resonant converter with two transformers is presented in this paper. Dual resonant tanks are composed of leakage inductors and resonant capacitors to achieve zero-current-switching turnoff for rectifier diodes at the secondary side of the transformer. Hence, the reverse-recovery problem of the rectifier diodes can be eliminated. Moreover, the active-clamp circuit does not only absorb the energy stored in the leakage inductor but also clamp the voltage stress of power switches. Compared to the conventional dual resonant converter, the zero-voltage switching operation of the proposed converter is easily achieved by using two transformers. The operation principles, design considerations, and realization are discussed in detail. Finally, experimental results from a 400-W laboratory prototype are presented to confirm the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

This paper presents a new three-level topology based on the neutral-point (NP)-clamped converter. An additional leg is added to the basic topology. The main purpose of this leg is to provide the converter with fault-tolerant capabilities. In addition, during normal operation mode, the fourth leg can be used to balance the NP voltage. In this way, the low-frequency voltage oscillations that appear in the NP under some operating conditions are cancelled out effectively. As a result, the modulation strategy of the three main legs of the converter does not have to take care of the voltage balance and can focus on other aspects such as, for instance, minimizing the switching losses of the converter. However, the inclusion of the fourth leg produces some additional losses. A resonant topology is proposed to minimize the switching losses of this leg. Three different fault-tolerant solutions based on the fourth-leg topology are presented. A comparison of these topologies showing their respective advantages and drawbacks is made. Experimental results are presented to show the viability of this approach. [ABSTRACT FROM AUTHOR]

This paper proposes a twin-buck converter with zero-voltage transition (ZVT). The converter comprises two identical buck conversion units employing power MOSFETs as the active power switches with an interleaved inductor. The ZVT is accomplished by resonating the currents between the interleaved inductor and the parasitic capacitances of the power MOSFETs. The detailed circuit operations and analysis are provided. A laboratory circuit rated at 300 W is designed and tested. Experimental results show that the switching losses can be effectively reduced by ZVT of the active power switches, accompanied by the reduced reverse recovery loss of freewheeling diodes. [ABSTRACT FROM AUTHOR]

Unipolar sinusoidal pulsewidth modulation (SPWM) full-bridge inverter brings high-frequency common-mode voltage, which restricts its application in transformerless photovoltaic grid-connected inverters. In order to solve this problem, an optimized full-bridge structure with two additional switches and a capacitor divider is proposed in this paper, which guarantees that a freewheeling path is clamped to half input voltage in the freewheeling period. Sequentially, the high-frequency common-mode voltage has been avoided in the unipolar SPWM full-bridge inverter, and the output current flows through only three switches in the power processing period. In addition, a clamping branch makes the voltage stress of the added switches be equal to half input voltage. The operation and clamping modes are analyzed, and the total losses of power device of several existing topologies and proposed topology are fairly calculated. Finally, the common-mode performance of these topologies is compared by a universal prototype inverter rated at 1 kW. [ABSTRACT FROM AUTHOR]

A novel zero-voltage-transition high-efficiency bridgeless power-factor-correction (PFC) circuit with a zero-current-switching auxiliary switch was proposed, analyzed, and experimentally verified. An assist circuit, consisting of a resonant inductor, two blocking diodes, a clamping circuit, an autotransformer, and an auxiliary MOSFET switch, was used to reduce the turn-on switching loss of the two main switches of the bridgeless PFC circuit and the turn-off switching loss of the auxiliary switch. The soft commutation of the main switches is achieved without imposing an additional voltage stress on the main switches. Feedback gate-drive signals can be obtained by using an existing converter IC controller modified to fit the purpose. In this paper, a detailed description of the circuit operation will be given. Based on the analysis, the guidelines for the component selection are presented. A prototype of 100-kHz 600-W universal-line PFC bridgeless circuit was built to verify the proposed scheme. In addition, based on the same concept, a family of bridgeless PFC configuration was proposed. [ABSTRACT FROM AUTHOR]

A novel three-phase diode boost rectifier is proposed in this paper. The core of the proposed topology is a power conversion device [the loss-free transformer (LFT)] with two terminals; one input and one output. The input is parallel-connected with the dc bus capacitor, while the output is connected between the rectifier plus rail and the dc bus plus rail. The LFT is controlled in such a way to control the rectifier current and boost the dc bus voltage. In contrast to the ordinary boost rectifiers, the switches of the new boost rectifier are rated on a fraction of the dc bus voltage and a fraction of the input current. It makes this topology very compact and efficient. Power rating, size, and losses depend strongly on the ratio of the dc bus voltage to rectifier voltage (boosting factor). For example, if the boosting factor is low, below 1.5, the power converter efficiency could be 98–99%. The proposed boost rectifier has been analyzed and experimentally verified on a 5.5-kW prototype. The results are presented and discussed. [ABSTRACT FROM AUTHOR]

Many static synchronous compensators (STATCOMs) utilize multilevel converters due to the following: 1) lower harmonic injection into the power system; 2) decreased stress on the electronic components due to decreased voltages; and 3) lower switching losses. One disadvantage, however, is the increased likelihood of a switch failure due to the increased number of switches in a multilevel converter. A single switch failure, however, does not necessarily force an (2n + 1)-level STATCOM offline. Even with a reduced number of switches, a STATCOM can still provide a significant range of control by removing the module of the faulted switch and continuing with (2n - 1) levels. This paper introduces an approach to detect the existence of the faulted switch, identify which switch is faulty, and reconfigure the STATCOM. This approach is illustrated on an eleven-level STATCOM and the effect on the dynamic performance and the total harmonic distortion (THD) is analyzed. [ABSTRACT FROM AUTHOR]

A newly designed zero-voltage-switching (ZVS) multi-input converter is proposed in this paper. The converter can boost the different voltages of two power sources to a stable output voltage. An auxiliary circuit is employed for achieving turn-on ZVS of all switches in the proposed converter. According to various situations, the operational states of the proposed converter can be divided into two states, including a single-power-supply and a dual-power-supply state. In the dual-power-supply state, the input circuits connected in series together with the designed pulsewidth modulation can greatly reduce the conduction loss of the switches. In addition, the effectiveness of the designed circuit topology and the ZVS properties are verified by experimental results, and the goal of high-efficiency conversion can be obtained. [ABSTRACT FROM AUTHOR]

Multilevel cascaded H-bridge converters have found industrial application in the medium-voltage high-power range. In this paper, a generalized modulation technique for this type of converter based on a multidimensional control region is presented. Using the multidimensional control region, it is shown that all previous modulation techniques are particularized versions of the proposed method. Several possible solutions to develop a specific implementation of the modulation method are addressed in order to show the potential possibilities and the flexibility of the proposed technique. In addition, a feedforward version of this technique is also introduced to determine the switching sequence and the switching times, avoiding low harmonic distortion with unbalanced dc voltages. Experimental results are shown in order to validate the proposed concepts. [ABSTRACT FROM AUTHOR]

A multilevel multiphase space vector pulsewidth modulation (SVPWM) algorithm has been introduced recently, in which the reference is separated into an integer part and a fractional part. The fractional part is, in essence, a two-level multiphase space vector algorithm. This paper shows that, with appropriate adaptations, the fractional part of the general space vector multilevel multiphase PWM can be applied as a stand-alone PWM method in conjunction with two-level voltage-source converters with any number of phases. Simulation results of the five- and six-phase cases are shown, and the new algorithm is compared with another recent multifrequency SVPWM algorithm, which follows the standard approach of selecting the switching vectors and calculating their application times using dq planes. The experimental verification is provided using a five-phase two-motor series-connected induction motor drive, supplied from a custom-designed five-phase voltage-source inverter. [ABSTRACT FROM AUTHOR]

This paper proposes a novel single-stage high-power-factor ac/dc converter with symmetrical topology. The circuit topology is derived from the integration of two buck–boost power-factor-correction (PFC) converters and a full-bridge series resonant dc/dc converter. The switch-utilization factor is improved by using two active switches to serve in the PFC circuits. A high power factor at the input line is assured by operating the buck–boost converters at discontinuous conduction mode. With symmetrical operation and elaborately designed circuit parameters, zero-voltage switching on all the active power switches of the converter can be retained to achieve high circuit efficiency. The operation modes, design equations, and design steps for the circuit parameters are proposed. A prototype circuit designed for a 200-W dc output was built and tested to verify the analytical predictions. Satisfactory performances are obtained from the experimental results. [ABSTRACT FROM AUTHOR]

The focus of this paper is the study of direct alternating-current (ac)–ac converters, beginning by buck, half-bridge, full-bridge, and push–pull converters. From the basic converters, we apply a simple methodology to make the use of switches in commercial configurations possible. Following that, eight voltage restorers supplied either on the line side or on the load side are proposed. A comparative evaluation of these topologies concerning implementation, complexity, and component effort is presented. It is notable that some of the studied topologies are known in the literature and others are new. For one of the presented topologies, the design of a 3-kVA voltage restorer is developed, and experimental results are shown, certifying the correct operation of the drive strategy used. [ABSTRACT FROM AUTHOR]

An input filter is necessary for a matrix converter (MC) system to improve the input current quality with low harmonic components, as well as to reduce the input voltage distortion supplied to the MC. However, the input filter's characteristics make the input power factor (IPF) obtained at unity only in the presence of high output loads, and the IPF degrades significantly under light-load conditions. In this paper, we propose a new direct space vector modulation (DSVM) method to achieve the required displacement angle between the input voltage and input current of the MC. A new switching strategy is introduced based on the maximum compensated angle. Then, power factor compensation algorithms using the new DSVM method to achieve the maximum IPF are presented, in which compensation algorithm I is based on using the input filter and power supply parameters to estimate the optimal compensated angle. Compensation algorithm II is subsequently proposed using a proportional–integral controller to overcome drawbacks presented in compensation algorithm I. Simulation and experimental results are shown to validate the effectiveness of the proposed compensation algorithms. [ABSTRACT FROM AUTHOR]