Abstract: This letter describes two improved 13-level inverters based on switched-capacitor. Compared with their original structure, which is published recently, one less high-voltage capacitor is required in the proposed inverters and the blocking voltage of their inverting half-bridge is reduced by half. In addition, the new inverters inherit various advantages of the original structure, such as a high boost factor of 6, self-balanced capacitor voltages, and reduced voltage ripples. Circuit description, operation principle, hybrid PWM modulation, and capacitor voltage ripples are analyzed and the feasibility of the proposed inverters is finally verified by experimental results.

Abstract: Passive electromagnetic interference filters (PEFs) are the most common way to solve electromagnetic interference (EMI) problems in power converters. However, PEFs bring additional volume, weight, and cost for power converters, especially common-mode (CM) inductors in PEFs, and it is a tricky issue for the high-power-density converters that must meet the electromagnetic compatibility specification. In order to design compact PEFs for power converters with pulsewidth modulation (PWM), a volume reduction method of CM inductors with chaotic PWM (CPWM) is proposed in this article. First, the mechanism that CPWM reduces the CM inductance by increasing the corner frequency is analyzed. Second, the relationship between the reduction of EMI spectrum magnitude by CPWM and the decrease of the CM inductance is quantitatively calculated. Third, utilization rate of the magnetic core η is defined to reasonably compare the size of the different inductors under traditional PWM and CPWM. Finally, the proposed design method of CM EMI filters is applied into a dc–dc converter and a dc–ac inverter, respectively, to verify its effectiveness and feasibility. In a dc–dc converter with the switching frequency 100 kHz, 275 W, the volume of the CM inductor and the volume of CM EMI filters are reduced by 63.5% and 48.3%, respectively, by using the proposed compact EMI filter.

Abstract: One of the problems of the selective harmonic elimination pulsewidth modulation (SHE-PWM) method is a limited range of feasible solutions. In many practical applications, the inverter is required to produce a variable output voltage within a wide range (e.g., 0.1 to 1). When the inverter operates in a low modulation index (low output voltage), the output harmonic distortion increases. This article introduces a method to use the SHE-PWM technique for a wide range of modulation indices, which allows achieving a high-quality output waveform in a cascaded H-bridge multilevel inverter. In a five-level case, a dc–dc converter regulates the dc-link voltage of only one bridge. In this way, the extra hardware requirement is reduced, and also a higher number of voltage levels is achieved, which improves the waveform quality. The particle swarm optimization algorithm is used to solve the SHE problem for different output voltage values. Two strategies are proposed to obtain the variable dc-link voltage; one of them is suitable for the lower output voltage values and the other one is more suitable for high values of the output voltage. The proposed strategies have been tested through simulation and experimental studies in different conditions. The results indicate a considerable improvement in the output waveform quality.

Abstract: A multilevel inverter (MLI) with a step-up feature has become significant for connecting a low-voltage PV system with a utility grid. An MLI has been presented in this article with a lower component count. The described structure has achieved nine distinguish voltage levels using 12 switches and a switched capacitor unit having twice voltage boost. A self-balancing of the floating capacitor voltage without any auxiliary circuits and precharging has been obtained. The new topology includes fewer switches, reduced voltage stress, and an inherent reversing polarity without the back-end H-bridge, which has been the additional feature of the proposed circuitry. The topology proposed has been controlled with the nearest level control pulsewidth control technique (NLC-PWM). A comprehensive comparative analysis with several similar topologies has been presented in this article to show the merits of the recommended topology. A number of simulation results using PLECS software have been discussed along with experimental results that have been obtained from a laboratory prototype. The validation of the proposed topology has been carried out using different steady-steady and transient operating conditions.

Abstract: An increased electricity demand and dynamic load changes are creating a huge burden on the modern utility grid, thereby affecting supply reliability and quality. It is thus crucial for modern power system researchers to focus on these aspects to reduce grid outages. High-quality power is always desired to run various businesses smoothly, but power-electronic-converter-based renewable energy integrated into the utility grid is the major source of power quality issues. Many solutions are constantly being invented, yet a continuous effort and new optimized solutions are encouraged to address these issues by adhering to various global standards (IEC, IEEE, EN, etc.). This paper therefore proposes a concept of establishing a renewable-energy-based microgrid cluster by integrating various buildings located in an urban community. This enhances power supply reliability by managing the available energy in the cluster without depending on the utility grid. Further, a “fuzzy space vector pulse width modulation” (FSV-PWM) technique is proposed to control the inverter, which improves the power supply quality. This work uniquely optimized the dq reference currents using fuzzy logic theory, which were used to plot the space vectors with effective sector selection to generate accurate PWM signals for inverter control. The modeling/simulation of the microgrid cluster involving the FSV-PWM-based inverter was carried out using MATLAB/Simulink®. The efficacy of the proposed FSV-PWM over the conventional ST-PWM was verified by plotting voltage, frequency, real/reactive power, and harmonic distortion characteristics. Various power quality indices were calculated under different disturbance conditions. The results showed that the use of the proposed FSV-PWM-based inverter adhered to all the key standard requirements, while the conventional system failed in most of the indices.

Abstract: In this paper, a brief review of the multilevel inverter (MLI) topologies is presented. The two-level Voltage Source Inverter (VSI) requires a suitable filter to produce sinusoidal output waveforms. The high-frequency switching and the PWM method are used to create output waveforms with the least amount of ripples. Due to the switching losses, the traditional two-level inverter has some restrictions when running at high frequencies. For addressing this problem, multilevel inverters (MLI) with lower switching frequencies and reduced total harmonic distortion (THD) are employed, eliminating the requirement for filters and bulky transformers. Furthermore, improved performance at the high switching frequency, higher power quality (near to pure sinusoidal), and fewer switching losses are just a few of the benefits of MLI inverters. However, each switch has to have its own gate driver for implementing MLI, which adds to the system's complexity. Therefore, reducing the number of switches of MLI is necessary. This paper presents a review of some of the different current topologies using a lower number of switches. Doi: 10.28991/ESJ-2022-06-01-014 Full Text: PDF

Abstract: This article presents the design, development, and optimization of pulsewidth modulation (PWM) scheme of an isolated bidirectional triple-active-bridge (TAB) dc–dc converter composed of three full-bridge modules and a high-frequency planar transformer. This article aims at improving the efficiency of the TAB converter by means of conduction loss minimization. The approach utilizes multiple control variables as degrees of freedom for the converter modulation. The optimization is based on the minimization of the true rms current, formulated using generalized harmonic approximation technique. The approach constitutes of two steps: the modulation pattern with least algorithmic complexity for efficiency maximization is first found depending on the operating load and gain condition, and, subsequently, the optimum control variables are calculated using the gradient descent algorithm applied on the identified modulation pattern. An 800-W TAB converter proof-of-concept is built to verify all theoretical considerations and model-oriented analysis. While the converter has an input dc bus voltage of 160 V, the two output ports of the converter can deliver 400 W each at voltage levels of 110–130 V and 18–27 V, respectively. With the implementation of the proposed optimal phase-duty control, the experimental results show a nonunity gain light load efficiency increment up to 6.1% compared with the conventional modulation technique.

Abstract: This article presents a finite-set model predictive control (FS-MPC) applied to the shunt active power filters (SAPF) based on three-phase inverters connected in parallel sharing the same dc-link. The discrete-time model of the system is used to predict the future value of the grid, circulation, and offset currents. The presence of circulation and offset currents occurs due to the connection of the two inverters in parallel sharing the same dc-link. There are 64 switching state vectors for SAPF and, in order to reduce the burden of calculation, only 30 switching states are chosen and applied, however keeping the advantages of the FS-MPC algorithm. The control strategy ensures the sinusoidal shape of the grid current, high power factor, and circulating and offset currents suppression. The FS-MPC has its performance compared to the pulsewidth modulation (PWM) strategy considering the SAPF with two parallel inverters, the conventional SAPF and the neutral-point-clamped SAPF. These comparisons include harmonic distortion, power semiconductor losses, and analysis of dc-link capacitor losses. As a multilevel topology, the SAPF with two parallel inverters using FS-MPC present competitive efficiency and can be applied with a good performance in industrial and residential applications. Simulation results and a laboratory-scale experimental platform is used for corroborating the proposal.

Abstract: Simulation studies of three synchronous reluctance motor (SynRM) control strategies are presented: field-oriented control (FOC), direct torque control (DTC), and finite-set model-predictive control (FS-MPC). FOC uses linear controllers and pulse-width modulation to control the fundamental components of the load voltages vectors. In contrast, DTC and FS-MPC are nonlinear strategies wherein the voltage vectors are directly generated in the absence of a modulator. Theoretical operating principles and control structures of these control strategies are presented. Moreover, a comparative analysis of the static and dynamic performance of the control strategies is conducted using Matlab/Simulink to identify their advantages and limitations. It is confirmed that each of the control strategies has merits and that all three of them satisfy the requirements of modern high-performance drives.

Abstract: In multiphase induction motor drives, lowering the common-mode voltage (CMV) reduces motor insulation degradation and the existence of destructive bearing current. For this investigation, a five-phase two-level voltage source inverter (FPTL-VSI) fed five-phase induction motor (FPIM) drive is used. FPTL-VSI produces increased CMV, which cannot be totally removed. Moreover, CMV can be reduced by 80% in contrast to its peak-to-peak value with suitable selection of small and large voltage vectors in a space vector pulsewidth modulation (SVPWM) scheme. Direct torque control (DTC) combined with the SVPWM scheme can accomplish such reduced CMV performance at constant switching frequency. To provide better speed and torque control, two virtual vector (VV) based SVPWM-DTC (DTC1 and DTC2) methods are proposed in this study. Over a wide range of modulation index, the influence of each voltage VV on motor drive speed and torque response is investigated. The proposed DTC1 and DTC2 schemes are validated under steady-state and dynamic conditions over a wide range of speed fluctuations using a high-power laboratory prototype of $3.8\,\text{{k}W}$ FPIM drive. The efficacy of the proposed DTC1 and DTC2 is compared to the current literature by evaluating the effectiveness of CMV and the switching frequency.

Abstract: Partial discharge (PD) is a phenomenon often occurring in insulation system defects (cavities), which can significantly affect life and reliability. While broad knowledge on PD phenomenology of high-frequency transformers (HFT) has been achieved under ac sinusoidal voltage, much less work has been done to infer PD behavior under emerging high frequency pulsewidth modulation (PWM) operation conditions. An impediment has been the limited appropriate test equipment. A recently developed novel ±5 kV GaN-based high-frequency PWM supply with controllable dV/dt, voltage level and frequency has been developed. This article explores the application of these measurements to the testing of materials in this electrical environment. Two commonly used windings for HFT were tested under different applied voltage magnitudes, frequencies, and slew rates. According to the test results, at high frequency (up to 50 kHz) the electric field generated by space charge deposited by PD occurring during previous PWM pulses plays an important role in PD behavior. The frequency dependent permittivity of the insulation material can also affect PD measurement results.

Abstract: Due to the increasing performance and decreasing price of microcontrollers in recent years, applying a high sampling frequency has become more feasible in modern control that is known as multisampling technology. The first motivation to use multisampling is emulating the analog control, thereby reducing the control delay and improving the stability of power electronics controllers. On the other hand, more information can be acquired from the multisampled current/voltage, which helps to save the cost and improve the reliability. In this article, a review of the multisampling application in power electronics converters is provided. Starting from the control delay analysis in single/double-sampling control, the modeling, implementation, and related control strategies are given when using multisampling pulsewidth modulation. Then, based on the multisampled data, the applications in condition monitoring and parameter estimation are discussed. Finally, perspectives on challenges and future trends are discussed.

Abstract: Discrete space vector modulation (DSVM) is employed to synthesize large number of voltage vectors (VVs) to improve the steady-state performance of predictive torque control (PTC). However, enumerating all the VVs in the prediction process increases the computation load of the motor drive. To address this issue, this article proposes a unidirectional VV preselection (UVVP) method for optimizing the performance of DSVM-based PTC of ac motors. The proposed UVVP method divides both voltage space vector diagram (VSVD) and flux space trajectory into twelve 30° based sectors to reduce the impact of candidate VVs with negative effects. At each flux position, the UVVP strategy can restrict the nearest candidate VVs in the 30° based VSVD region within the circular flux trajectory. This is achieved by using the speed direction to avoid the candidate VVs, which are in the same flux sector for reverse flux rotation, hence resulting in significant flux and torque ripple reduction. The main benefit of the proposed method is its simplicity since it only requires the flux sector and speed information as well as it can generate the VV enumerations online while ensuring the reduction of computation burden.

Abstract: In this work, a new direct power synergetic-sliding mode (DPSSM) technique based pulse width modulation (PWM) strategy for doubly-fed induction generator (DFIG) integrated to variable speed dual-rotor wind power (DRWP) systems is designed. The designed strategies produce voltage pulse width locations identical to those of a classical two-level inverter. In this novel control a synergetic-sliding mode (SSM) command and PWM technique to replace the hysteresis comparators and the switching table, for generating the reference voltage using PWM strategies for a classical inverter. Compared with traditional direct active and reactive powers control (DARPC), in this novel strategy, the switching frequency is maintained constant, and the undulations of the reactive power, current, torque, and active power are minimized remarkably. Simulation results verify the validity of the designed strategy.

Abstract: This article analyzes the propagation of feedback noise in multisampled dc–dc power converters. The analytical calculations for noise attenuation, strictly valid for linear time-invariant systems, are found to offer good predictions for power converters, after suppressing the decimation effects of the digital pulsewidth modulator (DPWM). For control systems that employ a proportional-integral controller, without any digital low-pass filters, the nonlinearity caused by the DPWM decimation is found to saturate the noise attenuation properties, as the multisampling factor $N$ is increased. Strong noise attenuation is enabled using antialiasing digital filters, with a small impact on the dynamic response. For control systems that employ a proportional-integral-derivative controller, increase of the multisampling factor, without any digital filters, causes the amplification of the noise power. Therefore, a greater attenuation of high-frequency components is required to provide a significant noise reduction in the control bandwidth. Even with these antialiasing digital filters, the dynamic response of multisampled control systems is improved compared to double-update. This is proven by the analytical and experimental comparison of various multisampled control strategies in terms of dynamic response and noise attenuation capabilities. The experimental results, from a buck-type converter, match well with simulations and analytical calculations.

Abstract: This paper presents an ADC-free compute-in-memory (CIM) RRAM-based macro, exploiting the fully analog intra-/inter-array computation. The main contributions include: 1) a lightweight input-encoding scheme based on pulse-width modulation (PWM), which improves the compute throughput by ~7 times; 2) a fully analog data processing manner between sub-arrays without explicit ADCs, which does not introduce quantization loss and saves the power by a factor of 11.6. The 40nm prototype chip with TSMC RRAM achieves energy efficiency of 421.53 TOPS/W and compute efficiency of 360 GOPS/mm2 (normalized to binary operation) at 100MHz.

Abstract: The process of electric multiple units (EMUs) passing long downhill sections is inevitable in the construction of mountain railways. Moreover, huge regenerative braking energy (RBE) will be sent back to the traction network, threatening voltage safety. Due to the lack of accurate vehicle-grid integrated models considering slope parameters in studying the RBE, this article proposes a modeling scheme, taking China railway high-speed 3 (CRH3) EMUs as an example. First, based on the extended dual pulsewidth modulation (PWM) mathematical model, the quantitative formula for calculating the motor braking power of the CRH3 EMUs is established. Moreover, the slope parameters are introduced into the vehicle-grid model via force analysis and regenerative braking power calculation. Then, by substituting the calculated results into the extended dual PWM mathematical model, the target instruction parameters are solved. Next, the accurate electrical characteristics, including catenary voltage, electromagnetic torque, and converter voltage, are simulated to evaluate the voltage safety. Finally, by comparing the simulation and semi-physical experiment results with the experimental data from the Chengdu to Chongqing railway line, the feasibility, validity, and accuracy of the model are verified.

Abstract: In this letter, two new improved pulsewidth modulation (PWM) techniques are proposed for single-phase cascaded H-bridge inverter. Compared with the conventional modulation methods, including phase-shifted PWM (PS-PWM), level-shifted PWM (LS-PWM), discontinuous modulation (D-PWM), only PS-PWM can ensure the output quality and maintain the power balance between each module. That is why it is widely used. However, the switch with PS-PWM always operates in a high-frequency mode, resulting in the high switching losses and low efficiency. In order to solve the problem, two improved cascaded H-bridge multilevel PWM methods are proposed in this letter. With the proposed PWM methods, the power can be evenly distributed among modules, the utilization rate of switching devices is the same, while the switching times are reduced, which improves the system efficiency. Finally, the experimental tests are carried out on a digital-control single-phase cascaded H-bridge seven-level inverter. And the experimental results verify the effectiveness of the proposed solution.

Abstract: This article investigates the capability of multi-sampled pulsewidth modulator (MS-PWM) control to improve the input admittance properties of voltage source converters (VSCs). Due to delays found in digital control systems, the VSC admittance features a negative real part above a certain frequency, which may result in lowly damped or even unstable grid dynamics. To prevent the occurrence of harmonic instability, recent standards require the admittance of every grid-connected VSC to behave as a passive network. In this article, it is shown that the MS-PWM control significantly improves passivity measures by reducing the overall system delay. The passive behavior is achieved effortlessly, using a single-stage control loop. This avoids the need for passive or active damping techniques, which are associated with increased losses and number of sensors, sensitivity to noisy measurements, ambiguity of damping filter design, and overall system complexity. The experimental verification, performed on a two-level single-phase VSC, shows a very good match between admittance measurements and analytic modeling even above the switching frequency. Grid-connected operation is tested to demonstrate the improvement of resonance damping obtained with MS-PWM control.

Abstract: In this letter, a quasi-resonant extended state observer-based predictive current control (QRESO-based PCC) strategy is proposed for three-phase pulse width modulation (PWM) rectifier. Specifically, the QRESO is utilized to estimate the predictive value of system total disturbance and grid current at time instant k+1 in the stationary αβ frame, and the required control input at time instant k+1 is then calculated based on the principle of deadbeat predictive control. The proposed control scheme can achieve robust control against to the electrical parameter variation, accommodate the measurement noise, and also assure the satisfactory steady-state and dynamic performance for the PWM rectifier. Besides, the stability analysis of QRESO and the whole current close-loop control system with the consideration of QRESO in the discrete-time domain are presented. Finally, several hardware-in-the-loop test results of the proposed control strategy are provided and compared with the model free predictive current control based on linear extended state observer and the generalized integrator-extended state observer-based PCC strategy, which validate the effectiveness and superiority of proposed QRESO-based PCC strategy.

Abstract: Three-level neutral-point-clamped (NPC) inverter is used in many industrial applications due to its attractive advantages in terms of harmonics content, achieved power level, and electromagnetic interference reduction. However, the main concern in this topology is the imbalance of the neutral point (NP) voltage in the dc side of the inverter. Indeed, the NP voltage distorts the output voltage of the inverter and increases voltage stress on its switching devices. In this article, a new NP voltage balancing control based on modified three-level space vector pulse width modulation (SVPWM) is proposed. The core idea of this method consists in adjusting the application times of redundant vectors in such a way that the NP voltage is kept balanced. In this method, the appropriate adjustment direction is determined by measuring only the capacitor voltages and the output currents of the inverter. The performances of the proposed method are validated and compared through various experimental tests, and the obtained results show an excellent NP voltage balancing regardless of the modulation index values.

Abstract: Finite control set model predictive control (FCS-MPC) is a control strategy with fast response and a simple and flexible structure. However, when the control plant is complicated such as a multiphase electric machine, the application of FCS-MPC faces clear challenges. This article for the first time investigates the FCS-MPC for a nine-phase open-end winding (OW) permanent magnet synchronous machine, which is powered by nine H-bridge inverters with a common dc bus. First, in order to solve the challenge of substantial iterations in the conventional FCS-MPC, the number of control sets is simplified by reconfiguring the high level in switching states. Then, to eliminate the zero-sequence current caused by the common dc bus, the zero common-mode voltage (CMV) vector is selected. Subsequently, duty-ratio optimization is used to further reduce the available vectors. By the abovementioned measures, the number of iterations is reduced from 19 171 to 18. In order to suppress the harmonic current, the virtual voltage vectors (VVs) are designed. Each VV is synthesized by two zero CMV vectors, which can eliminate all the third and fifth harmonics in the output voltage. In addition, to achieve symmetrical pulsewidth modulation pulse sequences, a general pulse generation method for OW drive systems is proposed. Finally, the control performance of different control sets and harmonic weighting factors are evaluated and compared, and the experimental results have verified the effectiveness of the proposed methods.

Abstract: Abstract Objective. This article presents a novel transcranial magnetic stimulation (TMS) pulse generator with a wide range of pulse shape, amplitude, and width. Approach. Based on a modular multilevel TMS (MM-TMS) topology we had proposed previously, we realized the first such device operating at full TMS energy levels. It consists of ten cascaded H-bridge modules, each implemented with insulated-gate bipolar transistors, enabling both novel high-amplitude ultrabrief pulses as well as pulses with conventional amplitude and duration. The MM-TMS device can output pulses including up to 21 voltage levels with a step size of up to 1100 V, allowing relatively flexible generation of various pulse waveforms and sequences. The circuit further allows charging the energy storage capacitor on each of the ten cascaded modules with a conventional TMS power supply. Main results . The MM-TMS device can output peak coil voltages and currents of 11 kV and 10 kA, respectively, enabling suprathreshold ultrabrief pulses (>8.25 μ s active electric field phase). Further, the MM-TMS device can generate a wide range of near-rectangular monophasic and biphasic pulses, as well as more complex staircase-approximated sinusoidal, polyphasic, and amplitude-modulated pulses. At matched estimated stimulation strength, briefer pulses emit less sound, which could enable quieter TMS. Finally, the MM-TMS device can instantaneously increase or decrease the amplitude from one pulse to the next in discrete steps by adding or removing modules in series, which enables rapid pulse sequences and paired-pulse protocols with variable pulse shapes and amplitudes. Significance. The MM-TMS device allows unprecedented control of the pulse characteristics which could enable novel protocols and quieter pulses.

Abstract: The current climatic scenario requires the use of innovative solutions to increase the production of electricity from renewable energy sources. Multilevel Power Inverters are a promising solution to improve the penetration of renewable energy sources into the electrical grid. Moreover, the performance of MPIs is a function of the modulation strategy employed and of its features (modulation index and switching frequency). This paper presents an extended and experimental analysis of three-phase five-level Cascaded H-Bridges Multilevel Inverter performance in terms of efficiency and harmonic content considering several MC PWM modulation strategies. In detail, the CHBMI performance is analyzed by varying the modulation index and the switching frequency. For control purposes, the NI System On Module sbRIO-9651 control board, a dedicated FPGA-based control board for power electronics and drive applications programmable in the LabVIEW environment, is used. The paper describes the modulation strategies implementation, the test bench set-up, and the experimental investigations carried out. The results obtained in terms of Total Harmonic Distorsion (THD) and efficiency are analyzed, compared, and discussed.

Abstract: The challenges faced in an isolated wind energy conversion system (WECS) are larger transient times, high steady-state error, and larger harmonic content. To overcome these issues, an adaptive voltage controller (AVC) along with the load current observer (LCO) could be the better proposition. However, the AVC and LCO, in conjunction with the conventional space vector pulse width modulation (SVPWM) technique to operate the three-phase inverter of WECS, would not be able to further improve these parameters. This paper proposes the use of the unified voltage SVPWM (UVSVPWM) technique along with the AVC and LCO, which could improve the transient behavior by about 30% as well as reduce the harmonic content of the load voltage and current by about 70% and 2%, respectively. This paper considers an isolated WECS connected to the linear load, which is operated under balanced as well as unbalanced load conditions. The proposed control technique is verified for both the balanced and unbalanced cases using MATLAB/Simulink.

Abstract: A class of single-stage multi-input Buck type high-frequency link's inverters with series and simultaneous power supply are proposed in this article, and the key technologies such as circuit structures and topological family, energy management control strategy (EMCS), power supply modes, steady-state principle characteristics are studied in depth, from which some important conclusions are obtained. The circuit structure is composed of a multi-input-single-output high-frequency inverter, high-frequency transformer, cycloconverter, and output filter in sequence. The EMCS is to generate bipolar tri-state multilevel sinusoidal pulse width modulation (SPWM) waves by phase shifting between right and left arms of the high-frequency inverting bridge, and the cycloconverter demodulates it into a unipolar tristate multilevel SPWM wave and performs commutation when the unipolar tristate multilevel SPWM wave is zero. In addition, the EMCS realizes the, smooth switching of different power supply modes and the stability of output voltage. 1 kVA multi-input inverter prototype is designed and developed, which has the advantages of single-stage power conversion, high-frequency electrical isolation, small volume and weight, wide duty cycle regulation range, high conversion efficiency, high output voltage waveform quality and strong load adaptability. It provides a kind of effective method for a variety of new energy joint power supply.

Abstract: This article explores a single-source UXE-type asymmetrical multilevel inverter for its operation on 13-, 11-, and 9-levels with boosted output voltage. The 13- and 11-level operations require a single voltage sensor to maintain the auxiliary dc link at $V_{\text{dc}}/2$ and produce 1.5 and 1.25 boosting using redundant states and exhibit lower capacitor inrush currents. For the 9-level operation, the topology exhibits self-balancing of the dc-link at $V_{\text{dc}}$ and a boosting of 2. With a conventional pulsewidth modulation (PWM) for the 13-level operation, the inverter can drive a predominantly inductive load of 0.35 lagging at unity modulation index. For the 11-level operation, the levels cease to maintain beyond the modulation of 0.95. Thus, a hybrid PWM is proposed to fully utilize the redundant states for the charging of the switched-capacitors and enhance the inverter active load capability in the 13-level mode by 21% at unity modulation index ( $m_a$ ) and address a 0.8 power factor load at the $m_a$ of 0.9. For the 11-level operation, the levels are maintained at any $m_a$ with the hybrid PWM. The operation of the inverter is also verified for nonlinear load. Further, the 9-level operation with twice boosting and self-balancing is presented. The results are verified on MATLAB/Simulink and validated experimentally.

Abstract: A robust and improved control scheme of a variable speed multi-rotor wind turbine (MRWT) system with a doubly fed asynchronous generator (DFAG) is displayed in this work. In order to improve the performances and effectiveness of the traditional direct power control (DPC) strategy of the DFAG, a new kind of sliding mode controller (SMC) called modified SMC (MSMC) is proposed. The most important advantage of the DPC-MSMC strategy is to reduce the power ripples and improve the quality of the currents provided to the grid. In addition, to control the rotor inverter, a pulse width modulation (PWM) technique is used. The proposed DPC-MSMC strategy was modeled and simulated using MATLAB/Simulink software. The simulation results showed that the ripples in stator currents, active and reactive powers and torque were considerably reduced for the proposed DPC-MSMC strategy compared to the traditional DPC. Additionally, the proposed DPC-MSMC method works excellently to reduce the total harmonic distortion (THD) of the stator current in the case of variable wind speed. On the other hand, a robustness test against parametric variations showed and confirmed the robustness of the proposed technique compared to the classical method.

Abstract: Triple active bridge (TAB) as an isolated multiport dc–dc converter is a promising solution for integrated energy management systems to maintain an efficient power flow between the ports. This article presents the design, modeling, and switching loss optimized phase-duty-controlled PWM modulation scheme of a TAB converter composed of three full-bridge modules and a high-frequency planar transformer. The work aims at the derivation and analysis of the zero-voltage switching (ZVS) conditions for a TAB, where the turn-on switching loss is mitigated along with attaining an improved EMI performance, comprising of reduced noise peaks. Moreover, an optimized five-variable control-based TAB PWM modulation technique is proposed in this article in order to achieve minimized switching loss and the overall system loss for a wide voltage gain and load range. The instantaneous switching currents, responsible for the switching losses at the devices, are derived from the transformer winding current expressions, formulated employing the generalized harmonic approximation (GHA) technique. The various loss minimization techniques and the theoretically obtained criteria for ZVS are experimentally verified using a laboratory-developed prototype of an 800-W TAB converter. With the implementation of the proposed optimal phase-duty control, the experimental results show a nonunity gain light-load efficiency increment up to 10% compared to the conventional phase-shift modulation alone.