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The three-phase four-leg inverter is very suitable for the high-power uninterruptible power supply application, and the load neutral point voltage (LNPV) should meet the requirement. In this paper, two factors influencing the LNPV were revealed first, which are the switching states and the ratio of the neutral inductance to the phase inductance (k). Then, the 16 switching states can be classified into four groups, and the ones in the first and the second group come to the minimum amplitude of LNPV with a specific ratio k respectively. Third, three methods to mitigate the LNPV were proposed based on the analysis of LNPV. In the first method, switching states in the first group are just utilized, and the LNPV can be eliminated with the ratio k of unity. In the second method, the switching states in the fourth class are avoided, and the LNPV can be reduced. Common mode filter is used in the third method and the LNPV can be mitigated effectively with the ratio k of unity. Furthermore, the power losses in the first and the second method were estimated and were compared with the original situation. Finally, the proposed methods were verified by simulation and experimental results. [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]

Multilevel inverters have been widely accepted for high-power high-voltage applications. Their performance is highly superior to that of conventional two-level inverters due to reduced harmonic distortion, lower electromagnetic interference, and higher dc link voltages. However, it has some disadvantages such as increased number of components, complex pulsewidth modulation control method, and voltage-balancing problem. In this paper, a new topology with a reversing-voltage component is proposed to improve the multilevel performance by compensating the disadvantages mentioned. This topology requires fewer components compared to existing inverters (particularly in higher levels) and requires fewer carrier signals and gate drives. Therefore, the overall cost and complexity are greatly reduced particularly for higher output voltage levels. Finally, a prototype of the seven-level proposed topology is built and tested to show the performance of the inverter by experimental results. [ABSTRACT FROM PUBLISHER]

This paper is devoted to the step-up dc/dc converter family with a cascaded quasi-Z-source network (qZS-network). The cascaded (two-stage) qZS-network could be derived by the adding of one diode, one inductor, and two capacitors to the traditional quasi-Z-source inverter (qZSI). The proposed cascaded qZSI inherits all the advantages of the traditional solution (voltage boost and buck functions in a single stage, continuous input current, and improved reliability). Moreover, as compared to the conventional qZSI, the proposed solution reduces the shoot-through duty cycle by over 30% at the same voltage boost factor. Theoretical analysis of the two-stage qZSI in the shoot-through and non-shoot-through operating modes is described. The proposed and traditional qZS-networks are compared. A prototype of a step-up dc/dc converter with the cascaded qZS-network was built to verify the theoretical assumptions. The experimental results are presented and analyzed. Finally, a further optimization method of the cascaded qZS-network is proposed, and some practical design issues are discussed. [ABSTRACT FROM PUBLISHER]

This paper proposes an adaptive sensorless position control system for a synchronous reluctance motor (SynRM). By using the proposed dual current-slope estimating technique, the rotor position of the SynRM can be precisely obtained. In addition, a comparison which shows that the proposed dual current-slope method has better performance than the traditional single current-slope method is discussed. To improve the transient responses and load disturbance rejection capability, an adaptive controller and a novel online self-tuning-gain state estimator are proposed here. A TMS-320F-28335 digital signal processor is used to execute the rotor position estimation, self-tuning-gain state estimation, adaptive control algorithm, d –q to a–b–c coordinate transformation, and PWM switching strategy. As a result, the hardware circuit is very simple. Experimental results show that the proposed system has satisfactory performance and good robustness. The estimated position error of the proposed dual current-slope estimating method can be reduced to 50% as compared to the traditional single current-slope position estimating method. Several experimental results are provided to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

Multilevel converters can reach medium-voltage operation increasing the efficiency of high-power applications. Among the existing multilevel converter topologies, the modular multilevel converter (MMC) provides the advantages of high modularity, availability, and high power quality. Moreover, the main advantage compared to cascaded multilevel converters is the lack of an input transformer which results in a reduction of cooling requirements, size, and cost. One of the drawbacks of this topology when used as an ac–ac converter is the input and output frequency components in the control loop, resulting in a more complex controller design. In this paper, a single-phase ac–ac MMC predictive control approach is proposed. The controller minimizes the input, output, and circulating current errors and balances the dc voltages. Experimental results show the performance of the proposed predictive control scheme. [ABSTRACT FROM PUBLISHER]

This paper compares two central dimmer system technologies used in street lighting. These dimmers are utilized in adaptive lighting systems based on high-intensity-discharge lamps and magnetic ballasts. The first technology is based on a multiple-tapped autotransformer which is commonly used for these types of installations. The second technology is based on a high-frequency switch converter (more specifically in a single-phase matrix converter topology) and represents a novelty for this type of application. Tests were conducted to determine the main features of both dimmer technologies, and the obtained results are presented. [ABSTRACT FROM AUTHOR]

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]

This paper proposes a closed-loop maximum power point tracker (MPPT) for subwatt photovoltaic (PV) panels used in wireless sensor networks. Both high power efficiency and low circuit complexity are achieved. A microcontroller ( \mu\C) driven by a fast clock was used to implement an MPPT algorithm with a low processing time. This leads to a maximum central-processing-unit duty cycle of 6% and frees the \mu\C to be used in the remaining tasks of the autonomous sensor, such as sensing, processing, and transmitting data. In order to reduce power consumption, dynamic power management techniques were applied, which implied the use of predictive algorithms. In addition, the measurement and acquisition of the output current and voltage of the PV panel, which increase circuit complexity, was avoided. Experimental measurements showed power consumptions of the MPPT controller as low as 52 \mu\W for a 2.7-mW PV power and up to 388 \mu\W for a 94.4-mW PV power. Tracking efficiency was higher than 99.4%. The overall efficiency was higher than 90% for a PV panel power higher than 20 mW. Field measurements showed an energy gain 15.7% higher than that of a direct-coupled solution. [ABSTRACT FROM PUBLISHER]

In this paper, a novel Zeta-mode three-level ac direct converter is proposed. The converter realizes three-level voltage waveforms before the output filter, which can get a better harmonic spectrum and reduce the bulk of the filter. Compared with two-level ac choppers, voltage stresses of the converter can be lowered. Compared with ac–dc–ac converters with no isolation and low- or middle-frequency isolation, the converter has single power stage and bidirectional power flow. Moreover, compared with buck-mode three-level ac choppers, it can realize buck and boost output voltage. The converter has four operation states in one period of input voltage and three different operation modes in one switching period. To ensure that the converter operates reliably, the noncomplementary control strategy is presented, which can make the converter switch smoothly between different modes in bidirectional power flow. Therefore, the converter is suitable to different kinds of loads. Principle analysis and experiment results of the prototype well verify the advantages of the proposed converter. [ABSTRACT FROM PUBLISHER]

Electronic load (E-load) is commonly used to test power supplies. In order to test computer power supplies, the E-load must possess an ideal controlled current source property which draws a desired load current even in the case of a very low terminal voltage of the source under test (SUT). It also needs to have superior dynamic performance to simulate high-slew-rate load transients. This paper proposes the design of a switching-converter-based E-load with very large operational bandwidth. The overall architecture of the E-load consists of a low-bandwidth converter, which functions under steady state, and a high-bandwidth auxiliary circuit that is only active during transient state. The converter circuit is realized using a novel switched-boost topology, and the auxiliary circuit is realized using a MOSFET operating at the edge of saturation and linear region. The proposed topology is capable of sinking a specific amount of load current even with a very low SUT terminal voltage. Simulation and experimental validations are provided to verify the proposed concepts. A prototype has been built to test the proposed architecture. The operational input voltage (SUT voltage) ranges of the prototype are between 0.5 and 6 V. The load current range is between 0.75 and 7 A. The results validate the excellent dynamic characteristics of the proposed architecture. [ABSTRACT FROM PUBLISHER]

A simple current sharing control technique for the switching power supply is presented herein, whose basic concept is that the control effort created from the voltage loop is finely tuned by the control effort created from the current sharing loop based on the proposed phase link so as not only to obtain the desired output voltage but also to make the load current distributed among phases as evenly as possible. Such a control method is not only without any current sharing bus as compared with the traditional current sharing methods, but also suitable for multiple phases under the condition that any one phase among multiple phases fails. Moreover, based on phase link, there is no divider used, as compared with the traditional average current method, and hence, the number of logic elements in the field-programmable gate array (FPGA) can be reduced. In this paper, the detailed basic operating principles, together with new mathematical deductions based on the superposition concept, are firstly described, and secondly some experimental results, based on the FPGA to realize the fully digitalized control of the overall system using one-comparator counter-based sampling without any analog-to-digital converter (ADC), are provided to verify the effectiveness of proposed control strategy. [ABSTRACT FROM PUBLISHER]

In this paper, a new family of zero-voltage-transition bidirectional converters using coupled inductors is introduced. By applying two auxiliary switches and coupled inductors, soft-switching condition is achieved for all semiconductor elements regardless of the power flow direction. Moreover, the presence of coupled inductors provides significant reduction in the converter volume, since all the converter inductors are implemented on a single core. Also, all semiconductor elements benefit from soft-switching condition in full duty cycle range, and thus, high efficiency is achieved for full line voltage range. No extra voltage and current stresses on the main switches and the ease of control are the other properties of the proposed converters. The proposed bidirectional buck and boost converter is fully analyzed for both buck and boost operating modes. The validity of the theoretical analysis is justified using the experimental results of a 240-W 50–100-V prototype converter. [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]

This paper presents a control strategy for a doubly fed induction generator (DFIG) using an indirect matrix converter, which consists of an input side matrix converter and an output side voltage source converter (VSC). The capability of the input converter to generate different “virtual dc link” voltage levels is exploited. The commutation of the VSI with reduced voltage is illustrated for operating points where the output voltage demand is low without any deterioration of the current control performance. The proposed method leads to a reduction in the commutation losses in the output converter and reduced common-mode voltage. For the input converter, soft switching commutation is obtained by synchronizing the input and output converter pulsewidth-modulation patterns. This modulation strategy is particularly applicable in DFIG applications because the required rotor voltage decreases when the DFIG speed is close to the synchronous speed. The complete control strategy is experimentally validated using a 2-kW rig. [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]

The design and characterization in high-voltage (HV)-CMOS technology of an innovative intelligent power switch (IPS) for harsh automotive applications is proposed in this paper. To safely handle the ordinary and extraordinary automotive electrical and environmental conditions, a systematic design flow is followed: several design solutions are presented at the architectural and circuital level, integrating on-chip self-diagnostic capabilities and full protection against the high voltage and reverse polarity, the effects of wiring parasitics, and the over-current and over-temperature phenomena. Moreover, the current slope and soft start integrated techniques ensure a low electromagnetic interference, and the IPS is also configurable to efficiently drive different interchangeable loads. The innovative IPS has been implemented in a 0.35-\mu\m HV-CMOS technology and has been embedded in mechatronic third generation brush-holder regulator system-on-chip for an automotive alternator. The electrical simulations and experimental characterization and the testing at component and on-board system levels prove that the proposed design allows a compact and smart power switch realization facing the harshest automotive conditions. [ABSTRACT FROM AUTHOR]

A simple current-sharing control technique for the switching power supply is presented herein, which is based on the concept of the differential-mode transformer and which makes the load current evenly shared well among phases all over the line voltage and load current ranges. This current-sharing structure is very simple, and it makes the efficiency relatively high at light load, which is quite suitable for industrial applications with standby power considered. In this circuit, a synchronously rectified switch is used to further upgrade the efficiency, and the coupling output inductors in copolarity are utilized to decrease the phase current ripples. In this paper, the detailed basic operating principles, together with mathematical deductions, are first described, and second, some simulated and experimental results are provided to demonstrate the proposed control strategy. [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]

In this paper, a modified direct torque control (DTC) for permanent-magnet synchronous machines, which enables important torque- and flux-ripple reduction by using voltage vectors with variable amplitude and angle, is proposed. In the proposed DTC, the amplitudes of torque and flux errors are differentiated and employed to regulate the amplitude and angle of the output voltage vectors online, which are finally synthesized by space-vector modulation (SVM). Two simple formulas are developed to derive the amplitude and angle of the commanding voltage vectors from the errors of torque and flux only. The conventional switching table and hysteresis controllers are eliminated, and a fixed switching frequency is obtained with the help of SVM. Stator flux is estimated from an improved voltage model, which is based on a low-pass filter with compensations of the amplitude and phase. The proposed DTC is comparatively investigated with the existing SVM-DTC from the aspects of theory analysis, computer simulation, and experimental validation. The simulation and experimental results prove that the proposed DTC is very simple and provides excellent steady-state response, quick dynamic performance, and strong robustness against external disturbance and control-parameter variations. [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]

In this paper, a novel current control approach called model predictive direct current control (MPDCC) is presented. The controller takes into account the discrete states of the voltage source inverter (VSI), and the current errors are predicted for each sampling period. Voltage vectors are selected by a graph algorithm, whereby the most appropriate vector is chosen based on an optimization criterion. However, this depends on whether the state of the system is transient or steady. In the first case, the current error should be minimized as fast as possible in order to obtain fast dynamics. In the latter one, the VSI switching behavior is optimized since the switching losses account for a large amount of the total converter losses in high-power drive systems. MPDCC has been developed for a general neutral-point isolated resistive–inductive load with an internal voltage source. For demonstration, the presented control strategy has been implemented on a small-scale permanent-magnet synchronous machine drive system with a two-level VSI. This new approach has several advantages. The most important one is that the switching frequency is reduced up to 70% compared to linear control combined with pulsewidth modulation. Second, MPDCC obtains fast dynamic responses, which are already known from, e.g., direct torque control. [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]

In this paper, a novel three-phase soft-switching inverter is presented. The inverter-switch turn on and turn off are performed under zero-voltage switching condition. This inverter has only one auxiliary switch, which is also soft switched. Having one auxiliary switch simplifies the control circuit considerably. The proposed inverter is analyzed, and its operating modes are explained in details. The design considerations of the proposed inverter are presented. The experimental results of the prototype inverter confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

Motivated by the method to analyze the impact of dead time in hard-switching converters, this paper, for the first time, analyzes the impact of zero-voltage notches on the outputs of soft-switching pulsewidth modulation (PWM) converters. It proves that the output distortion of soft-switching converters due to their deviation voltage is independent of the direction of their output current. Hence, their compensation strategies require no sensor to detect the current's direction, which is required by dead-time compensation methods in hard-switching converters. A simple yet effective compensation algorithm is presented for soft-switching converters. The analysis result and effectiveness of the proposed algorithm are experimentally verified via a three-phase inverter that represents an important class of converters. [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]