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This paper presents direct digital technique-generalized discontinuous pulse width modulation (PWM)—a new implementation method for an optimal discontinuous PWM (DPWM) in terms of switching losses of the inverter on an embedded system. At each sampling period, an optimal choice is done in order to clamp one of the three half-bridges. Its advantages compared to classic ones (DPWM) are as follows: needless to know the load power factor, operational under steady-state and dynamic operating conditions, and low computation time. The proposed algorithm is then verified by simulation. Experimental results, based on a resistance–inductance load and a starter-generator application, are provided to show its effectiveness. [ABSTRACT FROM AUTHOR]

The auxiliary railway power supply (ARPS) is needed in order to provide low and medium voltages to the onboard systems from the catenary high voltage. The outputs of the ARPS can be dc (24\ \Vdc \div 100\ \Vdc) or ac (400\ \Vac). In the case of ac voltage generation, the ac output voltage is under very restrictive total harmonic distortion specifications even in the presence of nonlinear loads which draw low-frequency current harmonics. Along the present paper, a new modulation technique is proposed under the name of harmonic cancellation technique. It is based on the proper pre-distortion of the inverter output voltage in order to generate a controlled fundamental harmonic as well as a set of low-frequency harmonics which cancel out the harmonic pollution due to the nonlinear load performance. The theoretical background needed to implement the modulation technique is provided as well as the experimental validation of the proposed modulation technique through a scale-down prototype. [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]

Inductive power transfer (IPT) is commonly used to transmit power from an extended loop (track) to a number of galvanically isolated movable pick-ups. To maximize the power transfer and minimize converter requirements, various compensation circuits have been proposed for both the track (primary) and the pick-up (secondary). This paper investigates the suitability of the LCC series–parallel compensation for IPT primary design. A new compensation-circuit design procedure is proposed that considers high-order current harmonics and results in inverter zero-current switching. The proposed compensation is compared with the classical compensation designed for zero phase angle between the inverter voltage and current fundamental components. Expressions for the bifurcation boundary, voltampere rating of reactive-compensation elements, and the current at the moment of switching are derived and analyzed. Analytical results are verified both via PSpice simulations and experimentally using a 1-hp MOSFET-based prototype. [ABSTRACT FROM PUBLISHER]

A hybrid pulsewidth modulation (PWM), combining the merits of both space-vector PWM (SVPWM) and selective harmonic elimination (SHE) PWM (SHEPWM), is proposed for three-level neutral-point-clamped (NPC) inverter-fed high-power adjustable-speed drives, which uses asynchronous SVPWM at low frequency and SHEPWM at high frequency. For SHEPWM, a novel formula is proposed to obtain the initial values of switching angles, leading to another valid solution that is different from the known ones in the literature. Furthermore, it is shown that, by eliminating the quarter-wave symmetry, unlimited groups of solutions to three-level SHEPWM can be obtained. The characteristics of the multiple solutions in terms of harmonic distribution, pulsewidth, and total harmonic distortion are investigated for the application of SHE in practical drives. Switching between SVPWM and SHEPWM is problematic if no appropriate measure is taken, particularly when the influence of the minimum pulsewidth (MPW) is considerable. A simple but effective method, taking into account the MPW, is proposed in this paper to address this problem. The multiple groups of solutions to SHE are simulated and experimentally verified on a low-voltage three-level NPC inverter prototype. Experimental results obtained from a low-voltage prototype and an industrial 6-kV/1250-kW three-level drive are presented to validate the smooth switching between SVPWM and SHEPWM. [ABSTRACT FROM PUBLISHER]

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]

Multilevel inverters introduce harmonics to the network besides their remarkable advantages. Total harmonic distortion (THD) is one of the most important indexes to evaluate the harmonic contents of waveforms. The conventional method of line-voltage THD calculation gives approximate answers, because high-order harmonics are ignored. In this paper, an analytical algebraic method based on formulating the line-voltage THD of multilevel inverters with unequal dc sources is presented. This method, which is general and applicable to each number of switching angles, is implemented to a five-level inverter with staircase waveform as a case study. The implementing process of this method can be easily repeated for each number of levels. The accuracy of the proposed method is illustrated in comparison with the approximate method. Some advantages of the extracted formulas of line-voltage THD are simplicity and rapidity in calculations, considering all harmonics and the possibility of finding optimal switching angles analytically. Experimental results are presented to validate the theory. [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 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 operation of switch-mode converters results in electromagnetic noise propagating throughout the power electronic system. Pulsewidth modulation (PWM) strategies with fixed switching frequency generate harmonics in the spectra of converter voltages and currents. Random PWM techniques allow the elimination of the harmonics, resulting in a continuous spectrum of noise, i.e., a spectrum retaining all frequency components. As a next step in advanced spectral shaping, a method presented in this paper produces spectral nulls at selected frequencies. This allows the carving of communication channels in the noise and the removal of spectral power at frequencies potentially harmful for the system. The theoretical analysis, computer simulations, implementation details, and experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper proposes a modified LLC resonant load configuration of a full-bridge inverter for induction-heating applications. The LLC load configuration is a combination of a series inductor, a matching transformer, and an inductor and a capacitor connected in parallel. The output power is controlled using the asymmetrical voltage-cancellation technique. With the use of a phase-locked loop control, the operating frequency is automatically adjusted to maintain a small constant lagging phase angle under load-parameter variation during the heating process. The proposed configuration has the benefit of smaller inductance and inherent short-circuit protection capability in case a short circuit occurs at the induction coil or from transformer saturation. The validity of the proposed method is verified through computer simulation and hardware experiment at an operating frequency range of 108.7–110.6 kHz. [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 provides the comprehensive development procedures and mathematical model of an adjustable speed drive (ASD) for steady-state solutions, transient trajectories, and local stability based on a Floquet multiplier theory. A complete representation of the ASD is employed, which includes the dynamic equation of the dc link capacitor and the detailed models of the diode rectifier and of the pulse width modulated inverter. The power electronic switches are efficiently represented through smooth functions that allow a larger integration step to be used without the loss of precision in the solution. An efficient technique in the time domain for the computation of the periodic steady-state solution of electric systems, including ASDs based on a discrete-exponential-expansion matrix and the Poincaré map, is used. The obtained results are validated against the solutions obtained with an implementation using the Power System Blockset of Simulink and against the response obtained by the measurements from a 1.5-kVA ASD experimental setup system. [ABSTRACT FROM AUTHOR]

Switching devices based on wide bandgap materials such as silicon carbide (SiC) offer a significant performance improvement on the switch level (specific on resistance, etc.) compared with Si devices. Well-known examples are SiC diodes employed, for example, in inverter drives with high switching frequencies. In this paper, the impact on the system-level performance, i.e., efficiency, power density, etc., of industrial inverter drives and of dc–dc converter resulting from the new SiC devices is evaluated based on analytical optimization procedures and prototype systems. There, normally on JFETs by SiCED and normally off JFETs by SemiSouth are considered. [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]

This paper proposes a single-phase seven-level inverter for grid-connected photovoltaic systems, with a novel pulsewidth-modulated (PWM) control scheme. Three reference signals that are identical to each other with an offset that is equivalent to the amplitude of the triangular carrier signal were used to generate the PWM signals. The inverter is capable of producing seven levels of output-voltage levels (Vdc, 2Vdc/3, Vdc/3, 0, -Vdc, -2Vdc/3, -Vdc/3) from the dc supply voltage. A digital proportional–integral current-control algorithm was implemented in a TMS320F2812 DSP to keep the current injected into the grid sinusoidal. The proposed system was verified through simulation and implemented in a prototype. [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]

In this paper, a simple fault diagnosis scheme for brushless direct-current motor drives is proposed to maintain control performance under an open-circuit fault. The proposed scheme consists of a simple algorithm using the measured phase current information and detects open-circuit faults based on the operating characteristic of motors. It requires no additional sensors or electrical devices to detect open-circuit faults and can be embedded into the existing drive software as a subroutine without excessive computation effort. The feasibility of the proposed fault diagnosis algorithm is proven by simulation and experimental results. [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]

This paper proposes a reversible six-phase machine drive system. It is composed of two parallel three-phase to three-phase dc-link converters without isolation transformers. The proposed topology permits one to reduce the harmonic distortion in the input converter and decreases the power processed by converter switches. Furthermore, the proposed configuration can guarantee the feasibility of the system when high-power applications are considered. The model and the control strategy have been developed. The simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

The aim of this paper is to propose a high-power-factor (HPF) single-stage inductor-capacitor-capacitor (LCC) resonant inverter for liquid crystal display (LCD) backlight. A half-bridge LCC resonant inverter shares switches with a power-factor-correction circuit to form single stage. The proposed single-stage LCC resonant inverter can achieve almost unity power factor and ripple-free input current by using a coupled inductor, and can also realize zero-voltage-switching by operating the switches above the resonant frequency. Thus, the proposed single-stage inverter not only provides HPF to the utility line, but also achieves circuit simplicity, low cost, and high reliability. Experimental results on a 32-in LCD backlight are obtained to show the performance of the proposed inverter. [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]

There is a strong trend in the photovoltaic inverter technology to use transformerless topologies in order to acquire higher efficiencies combining with very low ground leakage current. In this paper, a new topology, based on the H-bridge with a new ac bypass circuit consisting of a diode rectifier and a switch with clamping to the dc midpoint, is proposed. The topology is simulated and experimentally validated, and a comparison with other existing topologies is performed. High conversion efficiency and low leakage current are demonstrated. [ABSTRACT FROM AUTHOR]

Half-cycle symmetry selective-harmonic-elimination pulsewidth-modulation (SHE-PWM) problems may have a large number of valid solutions, which are beneficial to the optimization design. This paper proposes a novel generalized formulation of half-cycle symmetry SHE-PWM problems for multilevel inverters. The advantages of the proposed formulation include simplicity in format, flexibility in PWMwaveforms, and a broad solution space. A method to obtain initial values for the SHE-PWM equations according to the reference modulation index M and the initial phase angle of output fundamental voltage is proposed and investigated thoroughly. Take a five-level inverter with M = 0.75 as an example; six sets of solutions for two typical initial phase angles of 0°? and 90°? are presented. Simulations and experiments are carried out. It is demonstrated that the experimental results agree well with simulated ones, which proves the validity and practicability of the new method proposed. [ABSTRACT FROM AUTHOR]

The classical discontinuous pulsewidth modulations (DPWMs) cannot be efficiently applied in active power filters (APFs) because it is difficult to predict the peak values of the inverter current. Consequently, it is difficult to calculate the optimal position of the clamped interval to minimize the switching losses in any operating point. This paper proposes a new DPWM strategy for shunt APFs. The proposed modulation strategy detects the current vector position relative to the inverter voltage reference and determines the optimum clamped duration for each phase, in terms of switching power losses. It achieves a clamped voltage pattern, with variable lengths depending on the magnitude of the inverter current. This property reduces the current stress and minimizes the inverter switching losses. The proposed modulation strategy is described, analyzed, and validated on a three-phase voltage source inverter, rated at 3 kVA, 400 V, controlled as an APF. [ABSTRACT FROM AUTHOR]

When control schemes based on finite control set model predictive control are experimentally implemented, a large amount of calculations is required, introducing a considerable time delay in the actuation. This delay can deteriorate the performance of the system if not considered in the design of the controller. In this paper, the problem is described, and the solution to this issue is clearly explained using a three-phase inverter as an example. Experimental results to validate this solution are shown. [ABSTRACT FROM PUBLISHER]