Integrated magnetics based multi-port bidirectional DC–DC converter topology for discontinuous-mode operation

This paper proposes the simplified pulse width modulation (PWM) strategy in the bidirectional ac/dc single-phase converter with the feed-forward control scheme. In this, the number of switching of the proposed simplified PWM strategy is reduced to one-fourth to that of the unipolar & bipolar PWM. The feed-forward control scheme is used to achieve better performance of the ac/dc converter in both the rectifier & inverter mode as compared with the conventional dual-loop control scheme. The simplified PWM strategy with feed-forward control scheme has higher efficiency than that of the unipolar PWM & bipolar PWM strategies. Also, the total harmonic distortion is less in this PWM strategy. The simulation & experiments are carried out to verify the validity of the proposed PWM strategy & control scheme.

This paper proposes a modified modulating signal-based pulse width modulation (PWM) scheme for a neutral point clamped (NPC) inverter-based induction motor drive (IMD) for enhancing the power quality of solar photovoltaic (PV) fed water-pumping systems. During the previous several decades, the use of sustainable source-based power generation systems has benefited water pumps in household life, irrigation-based activities, and industrial sectors, especially in areas where the electric grid is less available. A critical concern has long been the power quality, speed, and torque of an induction motor used in solar PV-powered water pumping. This paper focuses on the improvement of power quality performance by minimizing total harmonic distortions (THDs), switching losses and conduction losses, and torque ripples in the induction motor driving the PV-fed water pump by using a modified PWM scheme that generates symmetrical and balanced gate driving signals for the NPC inverter employed in the IMD. The IMD with the suggested PWM switching strategy has been tested in all feasible induction motor operating situations. To demonstrate the effectiveness of the suggested PWM scheme, a performance comparison of the proposed PWM scheme with conventional PWM schemes is performed, and also the IMD with the suggested PWM switching strategy is tested in all feasible induction motor operating situations using the MATLAB/Simulink platform. A reduced scale prototype has also been built and tested in laboratory to validate the performance of the proposed PWM technique.

A harmonic elimination pulse width modulation (PWM) strategy is proposed to minimize the switching losses by continuously tracking the load power angle and clamping the switches around the peak current regions for three-phase inverters. The proposed harmonic elimination PWM strategy is a two-phase modulation method, as any desired voltage space vector is contributed by two pairs of switches only with one pair of switches always inactivated. If the peak of the load current can be centered in the clamped area (or the clamped angle) where the switches are inactivated, then switching losses can be minimized. However, during operation, the power angle between the load voltage and current varies with loads. The peak of the load current may not always be centered in the clamped area. By measuring the load power angle on-line, the proposed PWM strategy adjusts the clamped angle so as to center the peak of the load current in the clamped area. To verify the proposed method, a separately excited synchronous motor served as the load, since its current can be arbitrarily controlled to be leading or lagging. Experiments have shown the effectiveness of the proposed approach in tracking the lower power angle variation and in minimizing switching losses.

This paper proposes the simplified pulse widthmodulation (PWM ) strategy in the bidirectionalac/dc single-phase converter with the feed-forwardcontrol scheme. In this, the number of switching ofthe proposed simplified PWM strategy is reduced toone-fourth to that of the unipolar & bipolar PWM.The feed-forward control scheme is used to achievebetter performance of the ac/dc converter in both therectifier & inverter mode as compared with theconventional dual-loop control scheme. Thesimplified PWM strategy with feed-forward controlscheme has higher efficiency than that of the unipolarPWM & bipolar PWM strategies. Also, the totalharmonic distortion is less in this PWM strategy. Thesimulation & experiments are carried out to verify thevalidity of the proposed PWM strategy & controlscheme. The proposed simplified PWM strategy withthe proposed feedforward control scheme has lowertotal harmonic distortion than the bipolar PWM andhigher efficiency than both unipolar and bipolarPWMs. Furthermore, the proposed simplified PWMoperated in the inverter mode also has largeravailable fundamental output voltage VAB than boththe unipolar and bipolar PWMs. A prototype systemis constructed and the control scheme is implementedusing FPGA Spartan-3E XC3S250E. Both simulationand experimental results verify.

This paper gives the detailed study and analysis of the terminal voltage and the common mode voltage (CMV) for the photovoltaic fed cascaded half-bridge (CHB) multilevel inverter (MLI). The expression for the terminal voltage and CMV are also derived using switching function. The analytical waveforms obtained using the expression of the terminal voltage and CMV clearly indicate that the terminal voltage and CMV are not constant simultaneously. Thus, two pulsewidth modulation (PWM) schemes are proposed using redundant states concept for CHB nine-level MLI without the addition of any extra circuit element. The first PWM scheme reduces the high-frequency transitions in the terminal voltage and, thus, minimizes the leakage current. The other PWM scheme is designed to reduce the common mode current by maintaining CMV constant. Furthermore, the proposed PWM schemes are compared with the conventional PWM schemes. The effect of each PWM schemes on the terminal voltage and CMV is analyzed using the given switching function analysis. The given switching function analysis is also supported with the help of simulation and experimental results. The simulation and experimental results of the proposed PWM schemes are further compared with the conventional SPWM technique.

Continuous and discrete-time averaged models are available for pulse width modulated (PWM) converters operating in the continuous conduction mode (CCM). A new discrete-time model for PWM converters operating in the discontinuous conduction mode (DCM) is proposed that leads to the exact discrete-time mathematical representation of the averaged values of the output signal.This model can also provide the averaged values of other internal signals with little increase in simulation time. This model is also used to simulate PWM converters operating in both DCM and CCM when combined with the averaged CCM model in [1]. It is compared to other models with respect to accuracy and simulation speed through a numerical example of boost converter. This method gives the exact values of the one-cycle-average (OCA) values of signals at switching instants. Numerical simulations show the accuracy and speed of the proposed method as well as its advantage in simulating PWM converters operating in both CCM and DCM.

This work consists of design and experimental validation of Pulse Width Modulation (PWM) scheme for a cold gas thruster system which is driven by on/off type of actuators. PWM scheme designed according to the characteristics of the on/off type of actuators obtained by the developed solenoid valve model and the experimentation. Angular position of the single axis rotational platform is controlled by the PWM scheme and the state feedback angular position controller. The PWM scheme and the angular position controller are experimentally tested and the results are presented in this paper.

The interleaving of the carrier signals of the parallel voltage-source converters can reduce the harmonic content in the resultant switched output voltages. As a result, the size of the line filter inductor can be reduced. However, in addition to the line filter, an inductive filter is often required to suppress the circulating current. The size of the system can be reduced by integrating these two inductors in a single magnetic component. An integrated inductor, which combines the functionality of both the line filter inductor and the circulating current filter inductor, is presented. The pulsewidth modulation (PWM) schemes to reduce the flux in some parts of the integrated inductor are also analyzed. The flux reduction achieved by using these schemes is demonstrated by comparing these schemes with the conventional space vector modulation and the 60° clamped discontinuous PWM scheme. The impact of these PWM schemes on the harmonic performance is also discussed. Simulation and experimental results are presented to validate the analysis.

Rotor eddy current loss reduction, which may largely depend on the pulse-width modulation (PWM) strategies, is a key issue for high-speed permanent magnet synchronous motors (PMSM). In this paper, five PWM strategies are applied to a surface-mounted PMSM, respectively, and the rotor eddy current losses are investigated with FEM. Influence of the PWM strategies and their average switching frequency on the rotor eddy current loss is figured out, so that conclusions of reducing rotor eddy current loss in the high-speed PMSMs can be drawn.

In the previous literature, the introduction of the virtual space vector concept for the three-level three-leg neutral-point-clamped converter has led to the definition of pulsewidth modulation (PWM) strategies guaranteeing the dc-link capacitor voltage balance under any type of load, with the only requirement being that the addition of the three phase currents equals zero. This paper presents the definition of the virtual space vectors for the general case of an n-level converter, suggests guidelines for designing virtual-space-vector PWM strategies, and provides the expressions of the phase duty-ratio waveforms corresponding to this family of PWMs. Modulations defined upon these vectors enable the use of diode-clamped topologies with passive front-ends. The performance of these converters operated with the proposed PWMs is compared to the performance of alternative designs through analysis, simulation and experiments.

A single phase cascaded inverter consisting of two full bridges creates a five-level AC output voltage. Due to switch combination redundancies, there are certain degrees of freedom to generate the five-level AC output voltage. This paper presents the different types of unipolar pulse width modulation (PWM) strategies for the chosen inverter. The effectiveness of the developed strategies are demonstrated by simulation and experimentation. The results indicate that the multilevel inverter triggered by the developed unipolar PWM strategies exhibits reduced harmonics and higher DC bus utilisation. PWM strategies developed are implemented in real time using dSPACE/real time interface (RTI). The simulation and experimental results closely match with each other validating the strategies presented.

Pulse adjustment, a fixed frequency control approach, is employed to control DC/DC converters loaded by constant power loads (CPLs) in this paper. Pulse adjustment achieves output voltage regulation by choosing high and low power pulses instead of using conventional pulse width modulation (PWM) scheme. It is simple, cost effective, and enjoys a fast dynamic response. A model to analyze buck-boost converters controlled by pulse adjustment approach in discontinuous conduction mode has been driven. Stability of the buck-boost converter driving constant power loads is analyzed using introduced model. Comprehensive sensitivity analyses of applying pulse adjustment method to control DC/DC converters loaded by CPLs are done in this paper. This paper gives design considerations to assess performance and stability robustness of the pulse adjustment method to control DC/DC converters loaded by CPLs

The pulse width modulation (PWM) strategy employed in the voltage source inverter (VSI) not only control the magnitude of the output voltage but also the quality. Performance evaluations of such strategies are done in terms of fundamental voltage, total harmonic distortion (THD), switching losses etc. (primary indices) and also in terms of acoustic noise, electromagnetic interference (EMI), harmonic spread factor, distribution of harmonic power etc. (secondary indices). Multilevel inverter (MLI) has become unanimous choice in medium and high power applications due to their superior performance compared to three level inverters. The conventional Sub-Harmonic PWM (SHPWM) scheme and its variations offer the output voltage spectrum with high intensity harmonic components around the switching frequency; it will end with cluster harmonic with high acoustic noise. The first objective of this paper is to investigate harmonic spreading effects of existing multilevel inverter (MLI) strategies. Secondly the developing innovative PWM strategies for MLIs based on modified reference and carrier functions, which were proved for superior the primary indices at three-level VSI. Thorough simulation study of Pulse width modulation strategies such as SHPWM, inverted sine carrier PWM, MWM PWM, third harmonic injection PWM, triplen harmonic injection PWM, analog space vector PWM, trapezoidal PWM and discontinuous PWM for a cascaded multilevel inverter, are presented with results of primary and secondary indices. Hence, the PWM strategies of MLI are evaluated for harmonic spreading effect first time and a guide line for a beginner to select the PWM scheme for MLI fed drive systems is stenciled.

The control complexity of modular multilevel converter (MMC) increases with the number of submodules per arm. In particular, the implementation of a pulsewidth modulation (PWM) scheme and a voltage balancing approach for MMC is a major challenge. This paper proposes a generalized low-cost less computational decoupled sampled average PWM scheme for MMC. In this approach, the reference output voltage is generated by averaging the two nearest voltage levels from the top and bottom arms in each sampling interval. In addition, a simplified voltage balancing approach is proposed for MMC. The proposed approach does not require a sorting technique to select the submodules. Instead, the relative comparison logic is presented. The effectiveness of the proposed modulation scheme and voltage balancing approach is evaluated on a single-phase MMC system with three-level flying capacitor submodules. The proposed approach is extended to a three-phase system, which results in dynamic balancing of the zero-sequence voltage. Hence, the zero-sequence current is minimized. The performance of the proposed three-phase approach is compared with that of the conventional phase-shifted carrier PWM scheme. The simulation and experimental studies show successful voltage balancing among submodule capacitor voltage, low harmonic distortion, and less ripple in output current.

This paper studies the relations of space-vector modulation (SVM) and carrier-based pulse-width modulation (PWM) for multilevel inverter. The PWMs' generation of SVM can be achieved by carrier-based PWM scheme, but the modulated wave of SVM is acquired by vectors' calculations and switching-states' selection. Based on different selection of redundant switching-states, there are many types of SVM modulated waves, some of which can function equivalently through proper selection of common-mode injections in the case of carrier-based PWM, the others have more freedoms in switching-states' selection than carrier-based PWM. Selection of more switching-states in SVM is propitious to optimize the output voltage, balance the dc power and so on. Then an improved PWM scheme is proposed based on the modulation waves of three-level SVM, which reserves the main advantages of SVM, and can be achieved easily. Finally, a five-level test circuit is built to verify this PWM scheme.