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This paper proposes a distributed digital control architecture of a modular-based solid-state transformer (SST) using a digital signal processor (DSP) and a field-programmable gate array (FPGA). In particular, the three-stage SST based on a modular structure is the topology of most interest because of its superior controllability. In order to make the modular-based SST, the digital implementation is inevitable to achieve higher performances, improved reliability, and an easy development. In addition, the modular-based SST requires enough capacity for implementing complex control algorithms, multiple interfaces, and a large number of internal variables. In this paper, a digital control platform for the modular-based SST is built using a floating-point DSP and an FPGA that operate cooperatively. As a result, the main control algorithms are performed by the DSP, and the simple logical processes are implemented in the FPGA to synthesize the suitable gating signals and control external devices, respectively. The proposed implementation method enables high-switching-frequency operation, multitasking, and flexible design for the modular-based SST. Experimental results are presented to verify the practical feasibility of the proposed technique for the modular-based SST. [ABSTRACT FROM PUBLISHER]

A bilevel driving approach was proposed in the literature for mitigating the energy wastage associated with driving LEDs at high peak current. The main idea is to introduce two drive parameters, i.e., high/low PWM current levels and duty cycles, that give rise to a 2-D luminosity control capability. The same idea was later generalized to an n-level driving approach for maximizing the electrical-to-light conversion efficiency of LEDs. Although previous uses of the n-level driving approach have been focusing on improving the luminous efficacy of LEDs, it is shown in this paper that its 2-D luminosity control feature can also lead to a significant improvement in color resolution when applied to driving RGB LEDs, hence making it well suited for applications in large-area LED display panels. In comparison to the first prototype driver proposed by the inventor of the driving approach, a more practical implementation of the complex 2-D driving approach with digital microcontroller is demonstrated. The various technical aspects of the driving approach, including luminous efficacy, color resolution, and color stability over dimming, are discussed in this paper with the aid of experimental results. [ABSTRACT FROM PUBLISHER]

This paper deals with the modeling and the robust controller synthesis for nonlinear dc–dc converters. In the first part of this paper, a model for the bilinear dynamics is presented. Such nonlinear dynamics can be included in a convex polytope such that the trajectories of the converter out of the equilibrium are assured to remain inside a guaranteed region of stability despite of the bilinear term. Such a description of the dynamic response of the converter is employed, in the second part of this paper, to propose synthesis algorithms that can guarantee, a priori, the stability and performance requirements of the design. The resulting region of stability can take into account not only the bilinear terms but also the saturation of the control input, which is a topic of major importance in high-performance dc–dc converters. The aim of this paper is to contribute with a robust control framework which allows the designers to deal with the common requirements of regulated dc–dc converters. The correctness of the results has been verified both with numerical simulations and experimental measurements from dc–dc converter prototypes. [ABSTRACT FROM PUBLISHER]

This paper proposes some topologies for developing electronic ballasts, supplying high-intensity discharge lamps fed by a pulsewidth-modulation ac–ac converter, implemented with bidirectional switches. The lamp operates directly from the ac mains; thus, operation with low frequency so as to prevent the occurrence of destructive acoustic resonance is provided. The features of the proposed solution are high efficiency, high power factor, low cost, and the absence of electrolytic capacitors. This paper includes the design of passive elements, the transfer function, and the development of the control strategy. The experimental results qualify the viability of the system feasibility. [ABSTRACT FROM AUTHOR]

This paper deals with the capability of pulse width modulation (PWM) dimming operation added to the high-power factor-integrated buck-flyback converter (IBFC), which was developed in previous works for LED lighting applications. First, the two main dimming techniques will be introduced, namely, analog dimming and PWM dimming. Then, the three main PWM dimming schemes found in the literature, that is, enable dimming, series dimming, and parallel dimming, will be briefly discussed. Afterwards, the IBFC topology will be tested performing both analog and enable dimming. In addition, a new proposal is introduced: the high-frequency series PWM dimming technique, which overcomes all the challenges faced when developing PWM dimming capabilities in low slew-rate constant-current fixed-frequency-controlled converters and offers all the advantages of PWM dimming over analog dimming while maintaining good efficiency. The proposed dimming-technique control loop, as well as the laboratory tests, will be presented, discussed, and compared to analog dimming and PWM dimming, showing satisfactory results in terms of dimming ratio, input current total harmonic distortion (\THDI), and power factor. [ABSTRACT FROM AUTHOR]

Pulsewidth modulation (PWM) strategies and methods for multilevel converters are usually developed for series converters. One of the aims of this paper is to show that they may be applied to parallel converters using interleaving techniques, given that these converters also have multilevel characteristics. PWM methods based on carriers' disposition and on zero sequence injection are studied for parallel multilevel inverters. Analysis show that the best method in terms of load current ripple (phase disposition (PD) centered space vector PWM) has, nevertheless, a bad influence on the current balancing between commutation cells of the same phase. Another objective is to analyze these problems and to propose a solution to cancel current imbalance when using PD strategy. Experimental results validate the analysis presented in this paper as well as the compensation of band transition of the differential mode current observed when PD strategy is used. [ABSTRACT FROM PUBLISHER]

This paper proposes a unified PWM method for matrix converters so as to establish a common platform which can generate various types of PWM methods in real time by adjusting the free parameters in the modulation algorithm. As a foundation for unification, the general form of the modulation functions for matrix converters is derived using geometric transformation approach. All eligible direct modulation matrices are shown to be of indirect form and are expressed in terms of instantaneous phase quantities. This paper also presents a new viewpoint to consider a matrix converter as a generalized three-level inverter and to apply the double-carrier-based dipolar modulation technique of the three-level inverter to the matrix converter. Several concepts of the two-level PWM inverters are then generalized to the matrix converters for better visualization and understanding of the modulation process. [ABSTRACT FROM AUTHOR]

Multiphase (more than three phases) power electronic converters are required mainly for feeding variable-speed multiphase drive systems. This paper presents one such solution by using a direct ac–ac converter that can be used to supply a nine-phase drive system. The input is a fixed-voltage and fixedfrequency three-phase input, and the output is a variable-voltage and variable-frequency nine-phase output. A simple pulsewidthmodulation technique is developed for the proposed ac–ac converter named as a nonsquare three-to-nine-phase matrixconverter configuration. The developed modulation technique is based on the comparison of a high-frequency carrier signal with the duty ratios. Although the carrier-based scheme is widely employed for the control of back-to-back converters, it has recently been used for controlling a three-to-three-phase matrix converter. This concept is extended in this paper for controlling a threeto-nine-phase matrix converter. With the two techniques that are proposed, one outputs 0.75 of the input magnitude and the other outputs reach 0.762 of the input. This is the maximum value of the output voltage in the linear modulation range that can be achieved in this configuration of the matrix converter. The viability of the proposed control techniques is proved analytically through simulation and an experimental approach. [ABSTRACT FROM PUBLISHER]

Literature reports several future portable and distributed power supplies in the watt-to-kilowatt range based on rotating machinery equipped with a variable-speed permanent-magnet generator. In order to generate a constant direct-current output voltage, an ultracompact highly efficient low-power rectifier is required. A suitable concept, i.e., the half-controlled three-phase pulsewidth-modulation boost rectifier (HCBR), is analyzed in this paper. In previous literature, there is only limited information available, particularly concerning current stresses, common-mode characteristics, and operating principles. Therefore, the HCBR topology analysis is completed in this paper. Furthermore, a novel modulation scheme improving the power electronics efficiency is proposed using space-vector analysis. The integration into a compressed-air-to-electric-power system with a generator rotating at 350 000 r/min is presented, and the measurements verify the theoretical results with an efficiency increase of 2% for the novel modulation scheme. [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]

This paper is focused on the analysis of the acoustic noise of the magnetic origin emitted by ac electrical machine variable-speed drives. First, the principle of noise generation is presented as well as the method for taking into account the effects of the current harmonics on noise generated by the pulsewidth modulation supply. The experimental results for noise and vibrations are then presented. Afterward, the elements of the per-phase equivalent circuit for higher harmonic orders are identified. They show that usual assumptions to characterize that circuit are not applicable for high-frequency harmonics. The originality of this paper concerns the rotor design: A practical procedure to diminish the acoustic noise due to the switching is defined from the per-phase equivalent circuit. It is also shown that this design makes it possible to increase the machine efficiency. [ABSTRACT FROM PUBLISHER]

Numerous studies have been carried out to compensate or eliminate the dead-time effect. This paper analyzes the limitations of the previous compensation or elimination schemes. Then, a novel mixed pulsewidth-modulation scheme for dead-time elimination and compensation is proposed for the grid-tied inverter. The proposed scheme implements the dead-time elimination in most of the grid current fundamental period but switches to the conventional dead-time compensation around the zero-crossing point. In this way, a safe and efficient dead-time effect elimination method is achieved. Furthermore, this paper proposes to determine the switching point and the compensation direction by the grid current modulation function. Experimental results are given to demonstrate the validity and features of the proposed method. [ABSTRACT FROM AUTHOR]

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]

In this paper, the circuit design of a resonant inverter for plasma-driven system is studied. Based on the half-bridge inverter structure, the proposed circuit has included the soft-switching techniques so that the investment on heat dissipation can be greatly saved. Moreover, this paper has investigated plasma power control under different conditions. Via the developed control circuit to formulate the relationships between the output power and voltage as a quadratic function, the output power of the system can then be controlled and becomes insensitive to plasma voltage variations. In order to solidify the practicality of this circuit design, mathematical analyses and experimental validations have been thoroughly performed. Test results help confirm the effectiveness of the method, demonstrating its feasibility and practicality for high-frequency-drive industry applications. [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]

This paper introduces an alternative implementation of the traditional LC filter, called hybrid LC filter (HLCF). The construction described in this paper contains two foil windings that integrate inductance and capacitance into one unit. The main aspects of the HLCF design are considered. The experimental data show that the device proposed here can be used, instead of traditional LC filters, as an alternative solution for the mitigation of the adverse effects of the pulse-width modulation (PWM). [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]

In this paper, a particular phenomenon called indirect synchronization is investigated on self-oscillating current controllers. This phenomenon appears in medium frequencies, when the reference signal frequency tends to the switching frequency. In a previous work, it has been shown that the indirect synchronization causes discontinuities on the frequential response of the system, making the various linear or continuous models inefficient. For high-accuracy applications, such as active filtering or high-precision power supply, these discontinuities are a real problem. Thus, it seems important to offer an analytical description of this phenomenon. In this paper, an analytical model of the indirect synchronization phenomenon is proposed and checked by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper intends to develop a more accurate approach for determining the no-load iron losses in pulse width modulation (PWM) inverter fed induction motors. The proposed method is validated by means of a prototype motor with a plastic rotor cage. The iron losses have been computed by the timestepping finite element method, both with sinusoidal and PWM supply. The iron losses have then been estimated by adding up the contribution generated by orthogonal components of the flux density, as if the iron losses generated by these components were independent phenomena. The rotational hysteresis losses, as well as excess ones, have been calculated applying a correction factor based on experimental data. These factors are a function of the peak flux density and ellipticity of the B vector loci. Experimental validations are provided for several frequency and magnetic saturation values. In addition, this paper demonstrates the necessity to consider the harmonics initial phase in order to increase the accuracy in the iron loss prediction. [ABSTRACT FROM AUTHOR]

Voltage-oriented PI control of three-phase grid- connected pulsewidth-modulation rectifiers with LCL filters is addressed. LCL filters require resonance damping. Active resonance damping is state of the art to face the problem, but it is still under investigation because of the manifold solutions. It is often realized using many sensors and/or complex control algorithms. In contrast, pure PI control requires only one set of current sensors, and its implementation and design are rather simple and well known from the L filter control. PI control has already been shown to be a suitable solution also for LCL filters, but there are limitations. These are investigated in this paper. System stability is analyzed with respect to different ratios of LCL filter resonance and control frequencies. The latter are important parameters for system design and control. Both line and converter current control are analyzed. For a certain range of frequency ratios, the voltage.oriented PI control gives stable performance without additional feedback, but for ratios outside this range, stable operation is impossible. Experimental tests validate the theoretical results. In addition, an experimentally determined LCL filter transfer function is shown in this paper, which shows a lower resonance peak as expected from commonly used filter models. [ABSTRACT FROM AUTHOR]

The advancement in modulation strategies brings emergent solutions to suppress the leakage current in three-phase two-level transformerless grid-connected voltage source inverters (VSIs). However, most of the techniques are analyzed based on reduced common-mode voltage pulsewidth modulation (PWM) in motor drivers but fail to satisfy the specific requirement of grid-connected applications, such as wider power factor operation and lesser current distortion. To overcome such substantial drawbacks, this paper proposes a novel scalar PWM method for transformerless grid-connected VSIs. First, presented through a generalized scalar approach with unified zero-sequence voltage generation, the method is simple to implement and favored in practice. Besides, systematic and comprehensive mathematical analysis is illustrated to exhibit the validity of implemented method in reducing leakage current and shows its advantages over whole power factor range in terms of dc-link current harmonic, output current quality, and switching losses. Finally, simulations and experimental results are carried out to verify the effectiveness and superiority of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes the use of advanced bus clamping switching sequences to reduce the impedance network inductor current ripple of the three-phase Z-source inverter (ZSI). Proposed technique is named as ABC4_MCB. MCB denotes that the maximum constant boost control method is used for the voltage boosting. One of the conventional space vector pulsewidth modulation of ZSI, “ZSVM6,” is termed as ZSVM6_MCB under the maximum constant boost control method. The switching sequences of ABC4_MCB technique are designed in such a way that it offers around 34% reduction in the maximum instantaneous inductor current ripple as compared to the ZSVM6_MCB for the equal average switching frequency. The factor of percentage reduction in the inductor current ripple using the proposed technique is constant over the entire range of shoot through duty ratio (0–0.48). Theoretical findings have been verified using simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a novel fault-tolerant method for active–neutral-point-clamped (ANPC) inverter using a modified carrier-based pulsewidth modulation. At a fault event, the ANPC inverter is divided into subinverters, and the modulating signal is modified to two modulating signals. The modified modulating signals are used to control the subinverters and allow continuous operation of the three-level ANPC inverter during faulty conditions even up to four open-switch faults per phase. This technique provides the fault-tolerant capability of the ANPC inverter without the need to add any additional phase legs or complex control strategies. Furthermore, the proposed technique ensures the voltage balancing of the dc-link capacitors. The performance of the proposed fault-tolerant technique is verified through simulation studies in MATLAB/Simulink under different faulty conditions. The feasibility of the proposed technique is also verified experimentally. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a novel switching control method to improve the efficiency of the basic half-bridge converter for the whole range of the load current. Using multimode control for this purpose, instead of modifying the structure of the converter, is proposed for the first time. Efficiency improvement is achieved by using a digital controller to select and change the control mode to the most efficient one, for each of the load sub-ranges. Control modes are prominent ones, including asymmetric, duty phase shift, pulsewidth modulation, and burst control, and are selected in turn, while the load current varies in its entire range from the full down to the no-load. The three transition points between control modes, being specific values of the load current, are analytically determined based on comparing the half-bridge converter power losses for different control modes. The digital controller compares the load current with the transition points and puts the converter in the control mode with the highest efficiency. The accuracy of the analytically determined transition points and the efficiency improvement of the proposed control method over the previous ones are investigated and approved by the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, an LLC type converter with two interleaved pulsewidth modulation (PWM) rectifiers is proposed. Compared with the conventional LLC converter, it achieves a wide voltage regulation range independent of load. In the proposed structure, each secondary-side PWM rectifier can operate individually. With the interleaving technique and shared primary-side switching network, the circuit secondary-side current stress is halved and the primary-side current stress is largely reduced. Besides, the filter capacitor requirement is reduced. Therefore, the proposed structure is a good option for medium/high power wide output range applications. The symmetrical LLC resonant tanks always operate at the resonant frequency, which marks the optimal operation point of the LLC resonant tank. Therefore, the conduction loss is effectively mitigated. In the proposed converter, zero-voltage turning-on (ZVS) of the primary-side MOSFETs can be ensured and is independent of the load. Moreover, the turning-off currents of the primary-side MOSFETs are small and are also load independent. This brings the benefits of minimized circulating current and negligible turning-off loss and no MOSFET turning-off voltage spike. The secondary-side auxiliary MOSFETs turn-on with ZVS and rectifying diodes turn-off with limited di/dt. Topological analysis and experimental results of a 1.3 kW/100 kHz prototype generating 230–440 V output from 390-V input are presented. The prototype demonstrates 97.31% peak efficiency and good performance over a wide output range. [ABSTRACT FROM AUTHOR]

In this paper, a current-sharing method for an interleaved high-frequency LLC converter with partial energy processing is presented. A small transformer and an auxiliary low-power dc–dc converter are added in each phase, and the current sharing between phases is achieved by controlling the duty cycle of the auxiliary converter. Only partial energy is processed by the auxiliary converter; hence, the power losses of the added auxiliary converters are minimized, and the overall high efficiency is maintained. By transforming the current sharing of the resonant converter into pulsewidth modulation control of a dc–dc converter, the proposed method is simple to implement and easy to extend to multiple phases. The frequency of the auxiliary converter is independent of the main LLC, so the LLC can operate at a fixed switching frequency and duty cycle, and it is suitable for high-frequency applications. The operating principle, design considerations, and the control schemes are presented, and a 1-MHz two-phase interleaved LLC prototype was built to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

To achieve high frequency and high efficiency over a wide load range, a monolithic voltage-mode dc–dc buck converter with advanced burst mode (ABM) and pulsewidth modulation (PWM) is presented in this paper. The load current is detected by estimating the currents flowing through the high-side and low-side switches, which maintains a near constant mode changing point. A counter-based scheme is used to achieve seamless and smooth transition between PWM and ABM. Both operating modes share the same control blocks, and no additional zero current detecting circuit is needed. In addition, the output stage switch size can be adjusted to reduce switching loss and improve efficiency under ultra-light load conditions. Experimental results show that the integrated 3 MHz converter achieves high efficiency from 80 to 91%, over a wide load range from 0.001 to 5 A. When the switch size is set to 1/3 of the maximum value, an additional 5% efficiency improvement at under 0.1 A load can be realized. The mode changing point is set at 0.4 A with less than 10% variation when the input voltage changes from 3 to 5 V. The load transient response is also improved significantly. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on finite control set model predictive current control, validated experimentally with a rear axle electrical drive unit used in automotive applications. An improved problem formulation is suggested which lowers the computational turnaround time of the solver with approximately $\text{40}\%$ for an horizon length of $N=4$. Apart from the computational requirement aspects, the assessment focuses on inverter efficiency, phase current total demand distortion, and acoustic performance. The proposed solution is evaluated against a standard double proportional and integrator (PI) field-oriented current controller with pulsewidth modulation. It is shown that the proposed solution is feasible, the associated optimization problem at hand can be solved in real time, while exploiting the attractiveness of the proposed improvements. In summary, it is concluded that the inverter efficiency can be improved without deteriorating neither the phase current harmonics nor the acoustic performance. [ABSTRACT FROM AUTHOR]

This paper studies a multilevel multiphase dc–ac conversion system configured by a neutral-point-clamped converter fed by multiple battery packs connected in series. A virtual-vector modulation is selected and a state-of-charge (SoC) balancing control is designed to be able to employ the full battery bank capacity, even under different battery initial SoC values or different battery nominal capacities. The SoC balancing among battery packs is accomplished through the multilevel converter operation in a lossless manner, by simply distributing the dc-to-ac power flow among the batteries according to their SoC. A simple average system model is also presented, which allows performing very fast system simulations over long periods of time and serves as a convenient tool to tune the compensator parameters. The satisfactory performance of the proposed system configuration and control, which can be applied with any number of levels and phases, has been verified through simulations and experiments in a four-level three-phase dc–ac converter fed by three lithium-ion battery packs. The results prove the feasibility and advantages of the proposed system configuration, which can be used to implement conversion systems with different specifications combining several instances of a standard battery pack and a standard power semiconductor device. [ABSTRACT FROM AUTHOR]

Cascaded multicell converter (CMC) is one of the effective solutions for medium-voltage high-power drives. The inability to regenerate power back to the source is one of the limitations of this converter. The regeneration capability is obtained by using a pulsewidth-modulated active rectifier instead of a conventional three-phase passive rectifier in each cell. However, due to their two-level voltage operation at the input side, an inductor is required for each cell to filter out the switching frequency components from the input current. This paper proposes a new configuration of regenerative CMC based on coupled inductor to achieve multilevel voltage at the transformer secondary terminals. This allows us to operate the rectifier devices at reduced switching frequency. The coupled inductor reduces the total harmonic distortion (THD) of the transformer secondary current and thus the transformer size. The size of the filter inductor and the transformer ratings are compared. The operating principle and the detailed analysis are presented. A technique to bypass a faulty module is proposed. The working of the converter is verified through simulation and experimental studies. [ABSTRACT FROM AUTHOR]

An open-end winding induction-motor drive with two two-level inverters achieves three-level inversion. The draw- back of this configuration is the presence of a high zero-sequence current, stressing the semiconductor switching devices and the motor. To avoid this, two isolated dc power supplies are needed to feed individual inverters. In this paper, it is shown that it is possible to operate this drive with a single dc power supply, with reasonable engineering compromises. The new decoupled space-vector-based pulsewidth modulation (PWM) strategy proposed in this paper achieves this objective. This PWM strategy exploits the dependence of the zero-sequence voltage on the placement of the zero-vector of individual inverters. It is shown that the zero-sequence voltage of the dual-inverter system is suppressed by forcing the zero-sequence voltage of the individual inverters to a value of zero, in the average sense, in each sampling-time interval. This strategy, therefore, achieves a dynamic balancing of the zero-sequence current. It is also shown that this PWM scheme achieves the center spacing of effective-time period for the dual-inverter drive and its associated advantages. In addition, the effect of the placement of the zero-vector for individual inverters on the dual-inverter drive is investigated, and the experimental results are presented. [ABSTRACT FROM AUTHOR]

A performance analysis of three-phase and dual three-phase (DTP) induction pulsewidth modulation (PWM) inverter-fed motor drives is conducted in this paper. The focus is on the efficiency performance of high-frequency DTP machines compared to their three-phase counterparts in low/medium power applications. For this purpose, a DTP machine, having two sets of stator three-phase windings spatially shifted by 30 electrical degrees (asymmetrical six-phase winding configuration), was tested for both six-phase and three-phase winding configurations under the same magnetic conditions. Simulation and experimental results are presented to evaluate the efficiency performance of three-phase and dual-three induction motor drives employing PWM voltage source inverters. [ABSTRACT FROM AUTHOR]

In the last few years, interest in multiphase converter technology has increased due to the benefits of using more than three phases in drive applications. Besides, multilevel converter technology permits the achievement of high power ratings with voltage limited devices. Multilevel multiphase technology combines the benefits of both technologies, but new modulation techniques must be developed in order to take advantage of multilevel multiphase converters. In this paper, a novel space vector pulsewidth modulation (SVPWM) algorithm for multilevel multiphase voltage source converters is presented. This algorithm is the result of the two main contributions of this paper: the demonstration that a multilevel multiphase modulator can be realized from a two-level multiphase modulator, and the development of a new two-level multiphase SVPWM algorithm. The multiphase SVPWM algorithm presented in this paper can be applied to most multilevel topologies; it has low computational complexity and it is suitable for hardware implementations. Finally, the algorithm was implemented in a low-cost field-programmable gate array and it was tested in a laboratory with a real prototype using a five-level five-phase inverter. [ABSTRACT FROM AUTHOR]

A multilevel drive can be realized by using an open-ended machine, fed from dual two-level inverters. The topology supplied from isolated dc sources is suitable for transportation electrification. In vehicular systems, it is essential that the isolated dc sources, comprising of battery packs, should discharge uniformly and maintain balanced dc voltage at the dc-link terminal. A simple carrier-based pulsewidth modulation (PWM) technique is presented in this paper, which can effectively regulate the power drawn between the two two-level inverters while maintaining the multilevel operation of the drive. The modulation technique can balance the instantaneous state of charge of independent battery packs and dynamically equalize the power flow from the two inverters, based on drive requirement. This will enhance the reliability of the propulsion system in electric vehicles. The operation of the proposed PWM technique has been validated through detailed simulation and experimental tests. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of the input dc-link voltage ripple in multilevel inverter based on H-bridge and level doubling network (LDN). The LDN is basically a half-bridge fed by a floating capacitor, with voltage self-balancing capability, recalling the concept of a flying capacitor configuration. The amplitude of the LDN voltage ripple is analytically determined considering both the low-order and the switching harmonic components. In particular, peak-to-peak distributions of voltage ripples over the fundamental period are analytically determined, making possible the design of dc-link capacitor relying only on the dc-voltage ripple requirements. The case study makes reference to negligible switching ripple in the output current. It well represents either grid connection or passive load having almost sinusoidal currents. Numerical simulations carried out by MATLAB/Simulink and a complete set of experimental verifications are given to confirm the theoretical developments. [ABSTRACT FROM AUTHOR]

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

According to different clamping methods, nine modes (C_MODE1-9) of the traditional discontinuous pulsewidth modulation (DPWM) for neutral-point-clamped three-level converter have been revealed. Since traditional DPWM cannot balance neutral point (NP) voltage under the full range of modulation index (MI) and power factor (PF), two extended modes (E _MODEs) are proposed in this paper, which can balance NP voltage. The proposed extended discontinuous pulsewidth modulation (EDPWM) is characterized by using C_MODEs and E_MODEs alternately.Therefore, EDPWM can balance NP voltage under the full range of MI and PF. Since the switching numbers under C_MODE and E_MODE in one switching cycle are two and three, respectively, the switching loss under EDPWM is lower than that under other pulsewidth modulation (PWM) strategies. The performance of EDPWM is analyzed and compared with traditional DPWM, space vector PWM (SVPWM) and virtual SVPWM (VSVPWM) in terms of switching loss, waveform quality, and the ability of NP voltage control. Finally, the feasibility and superiority of the proposed method are verified by experiments. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to controlling and optimizing a single-stage boost-integrated full-bridge dc–dc converter for a stand-alone photovoltaic-battery-powered dc motor system by combining pulse-frequency modulation (PFM), pulsewidth modulation (PWM), and phase angle shift (PAS). Unlike most of the existing multiport dc–dc converters, which aim at regulating the output voltage (first- or second-quadrant operation), the dc motor load requires both voltage and current reversals (four-quadrant operation). The converter is able to perform three tasks simultaneously: maximum power point tracking (MPPT), battery charging/discharging, and driving the dc motor at variable speeds including bidirectional and stall motions. To achieve these control objectives, the boost inductor and the motor inductance operate in different modes such that PFM and PWM can be used to achieve MPPT and a wide motor voltage range, respectively. By properly adjusting the PAS of the duty cycles, the capacitor and battery rms current value can be reduced, while the operation of the converter remains unchanged, hence improving the conversion efficiency. Experimental results of a 26-W laboratory prototype converter confirmed the proposed design and operation and the efficiency improvement by 2–6%. [ABSTRACT FROM AUTHOR]

The phenomenon of dc-capacitor-voltage drift is the main technical drawback of a passive front-end multilevel diode-clamped converter (DCC). This paper formulates and analyzes the dc-capacitor-voltage-drift phenomenon of a passive front-end five-level DCC, which operates based on a sinusoidal pulsewidth-modulation (SPWM) switching strategy. The analysis shows dependence of the voltage drift on the modulation index and the ac-side power factor of the DCC. The analysis concludes that an SPWM strategy, without the use of auxiliary power circuitry, is not able to prevent the voltage-drift phenomenon of a five-level DCC. This paper also proposes a space-vector-modulation (SVM)-based switching strategy that takes advantage of redundant switching vectors of the SVM method to counteract the voltage-drift phenomenon. The limit to the range of operation of a five-level DCC, which is based on the proposed SVM strategy, is also presented. The salient feature of the proposed strategy is that it enables voltage balancing of the dc capacitors with no requirements for additional controls or auxiliary-power circuitry, within the specified range of operation. Theperformance of a DCC under various operating conditions, based on time-domain simulation studies in the MATLAB/SIMULINK environment, is evaluated. This paper demonstrates capability of the proposed SVM strategy to control and maintain voltage balance of dc capacitors. [ABSTRACT FROM AUTHOR]

A pulsewidth-modulated (PWM) voltage applied to a squirrel-cage induction motor (SQIM) can cause high bearing currents, heating of rotor shaft, voltage spike across the motor terminals, etc. Filtering of this PWM voltage to obtain a sinusoidal output voltage can be a solution to this problem. However, a passive L-C filter makes the dynamic performance of the drive poor for high-performance control application. In this paper, a feed-forward control strategy for the L-C filter is proposed to have a good bandwidth for the filter output voltage. This filter control strategy is introduced along with a sensorless vector control strategy for the, SQIM drive. This complete strategy retains the high dynamic performance of the drive even with the L-C filter. In this paper, a three-level converter is used as a voltage source inverter for the drive to have a less filter-size requirement. The control strategy is verified on a 7.5-hp SQIM drive with a three-level insulated-gate bipolar-transistor inverter and L-C filter. Experimental results validate the high dynamic performance of the drive with filter. [ABSTRACT FROM AUTHOR]

This paper presents a new switching strategy for pulse width modulation (PWM) power converters. Since the proposed strategy uses independent on/off switching action of the upper or lower arm according to the polarity of the current, the dead time is not needed except instant of current polarity change. Therefore, it is not necessary to compensate the dead time effect and the possibility of arm short is strongly eliminated. The current control of PWM power converters can easily adopt the proposed switching strategy by using the polarity information of the reference current instead of the real current, thus eliminating the problems that commonly arise from real current detection. In order to confirm the usefulness of the proposed switching strategy, experimental tests were done using a single-phase inverter with passive loads, a three-phase inverter for induction motor drives, a three-phase ac/dc PWM converter, a three-phase active power filter, and a class-D amplifier, the results of which are presented in this paper. [ABSTRACT FROM AUTHOR]

Most issues carried out about building integrated photovoltaic (PV) system performance show average losses of about 20%-25% in electricity production. The causes are varied, e.g., mismatching losses, partial shadows, variations in current- voltage (I-V) characteristics of PV modules due to manufacturing processes, differences in the orientations and inclinations of solar surfaces, and temperature effects. These losses can be decreased by means of suitable electronics. This paper presents the intelligent PV module concept, a low-cost high-efficiency dc-dc converter with maximum power point tracking (MPPT) functions, control, and power line communications (PLC). In addition, this paper analyses the alternatives for the architecture of grid- connected PV systems: centralized, string, and modular topologies. The proposed system, i.e., the intelligent PV module, fits within this last group. Its principles of operation, as well as the topology of boost dc-dc converter, are analyzed. Besides, a comparison of MPPT methods is performed, which shows the best results for the incremental conductance method. Regarding communications, PLC in every PV module and its feasibility for grid-connected PV plants are considered and analyzed in this paper. After developing an intelligent PV module (with dc-dc converter) prototype, its optimal performance has been experimentally confirmed by means of the PV system test platform. This paper describes this powerful tool especially designed to evaluate all kinds of PV systems. [ABSTRACT FROM AUTHOR]

This paper presents analytical techniques for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse-width modulation schemes for two-level, three-phase voltage source inverters. The proposed modulation schemes are applicable to inverters generating balanced or unbalanced phase voltages. Some results presented in this paper analytically generalize the several expressions for the modulation signals already reported in the literature and new ones are set forth for generating unbalanced three-phase voltages. Confirmatory experimental and simulation results are provided to illustrate the analyses. [ABSTRACT FROM AUTHOR]

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

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

This paper presents an MHz LLC resonant converter with load-regulating capability. Unlike the two-stage solution, most of input power is delivered to the load directly by the main transformer in the proposed topology. Moreover, only small portion of input power is converted by two stages: 1) auxiliary transformer and 2) a cascaded PWM dc–dc converter. Therefore, the sacrifice of the efficiency caused by the two-stage conversion is minimized. The operating principle of the proposed converter is analyzed, and a 1-MHz prototype based on the proposed converter is built-up to verify the high-frequency, high-efficiency, and output-regulating capability. [ABSTRACT FROM PUBLISHER]

The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel method of interturn fault detection based on measurement of pulsewidth modulation (PWM) ripple current. The method uses the ripple current generated by the switching inverter as a means to detect interturn fault. High-frequency (HF) impedance behavior of healthy and faulted windings is analyzed and modeled, and ripple current signature due to interturn faults is quantified. A simple analog circuit is designed to extract the PWM ripple current via a bandpass (BP) filter and a root-mean-square (RMS) detector for fault detection. In addition, this method can also identify the faulted phase, which can be used for fault mitigation strategies. The method is tested experimentally on a five-phase permanent-magnet (PM) machine drive. [ABSTRACT FROM PUBLISHER]

This paper presents a highly efficient asymmetrical pulse-width modulated (APWM) full-bridge converter for renewable energy sources. The proposed converter adopts full-bridge topology and asymmetric control scheme to achieve the zero-voltage switching (ZVS) turn-on of the power switches of the primary side and to reduce the circulating current loss. Moreover, the resonant circuit composed of the leakage inductance of the transformer and the blocking capacitor provides the zero-current switching (ZCS) turn-off for the output diode without the help of any auxiliary circuits. Thus, the reverse recovery problem of the output diode is eliminated. In addition, voltage stresses of the power switches are clamped to the input voltage. Due to these characteristics, the proposed converter has the structure to minimize power losses. It is especially beneficial to the renewable energy conversion systems. To confirm the theoretical analysis and validity of the proposed converter, a 400 W prototype is implemented with the input voltage range from 40 to 80 V. [ABSTRACT FROM PUBLISHER]

By taking into account technical and economic features, a brief review is presented for the basic topologies and methods of self-excited induction generators (SEIGs). Three novel solutions are described in more detail; two of them are based on resonant circuit application, the third one applies a switched condenser topology using a novel control method based on space vector (SV) theory. In these solutions, the theoretical considerations are confirmed by computer simulations and laboratory test results. [ABSTRACT FROM AUTHOR]