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Recently, inverters with a common ac and dc ground are gaining significant interest due to their zero common-mode voltage that made them particularly attractive for the solar photovoltaic application. However, the dc source current of the existing topologies is discontinuous, and their voltage gains are limited. This article proposes a novel common-ground-type boost inverter that achieves continuous dc source current with significantly enhanced dynamic voltage gain. It consists of one boost inductor, four capacitors, nine power MOSFETs, and two power diodes. Voltage boosting and generation of nine-level ac voltage are achieved concurrently within a single-stage operation. The operation of the proposed CGT-9L-BI inverter is analyzed. Simulation and experimental results are presented for validation.

The emerging switched-capacitor-based multilevel inverters offer interesting merits such as self-balancing of capacitor voltages and boosting of voltage gain. While the switched capacitors (SCs) in these topologies are charged in parallel with the dc source, severe current spikes issue is inevitable, rendering them impractical at high power. This article proposes a novel switched-capacitor-based T-type inverter that mitigates the current spikes by enabling soft charging for its integrated SCs, where both SC in the topological structure charges through a dedicated circuit comprises of an inductor and two switches. The proposed topology is capable of five-level ac voltage generation and when compared to a classical T-type/ANPC (active neutral-point-clamped) inverter, it achieves higher dc-link voltage utilization since its maximum attainable voltage gain is doubled. Theoretical findings of the proposed topology are validated by both the simulation and experimental results.

Switched-capacitor-based multilevel inverters have been gaining increasing attention in recent years in view of their voltage-boosting capability and capacitor self-balancing properties. However, the existing topologies, which comprise frontend switched-capacitor cells and a backend H-bridge, result in longer discharging duration in some of their switched-capacitors. In addition, the adoption of backend H-bridge introduces common-mode voltage and necessitates multiple dc sources for voltage level extension. To resolve these problems, this article proposes a novel topology comprises a T-type inverter and n cascaded switched-capacitor cells. It requires only a single dc source and it manages to mitigate the common-mode voltage by connecting the neutral of ac output to the mid-point of dc link. All switched-capacitors in the proposed topology are ensured to be charged for at least half of the fundamental period to alleviate the capacitor voltage ripples and current spikes. The operation of the proposed topology is analyzed and experimental results are presented for validation.

Voltage source multilevel inverters with reduced leakage current, single-stage voltage step-up feature, compact design, and an efficient performance are a promising technology for high-frequency ac (HFac) microgrids feeding through renewable energy sources. This article proposes a novel single-source common-grounded (CG) step-up nine-level (9L) inverter, which can be applied in HFac microgrid applications. The proposed CG-based boost inverter is comprised of only nine switches (9S) and three self-balanced capacitors. Using the switched-capacitor (SC) technique, a double voltage boosting feature within a single power processing stage is achieved, while the leakage current concern is eliminated due to a CG-based configuration between the input dc source and the null of the grid. With the help of an LC input filter, the input current profile is free from large discontinuous inrush spikes. The working principles of the proposed 9L9S-CGSC inverter are discussed in this article. The modulation and closed-loop control strategy, as well as a comparative study, are presented. Finally, the open and closed-loop grid-tied performances of the proposed topology are evaluated by both simulation and experimental results obtained from a 1.2-kW laboratory-built prototype.

The emerging active-neutral-point-clamped (ANPC) inverters with voltage-boosting capability are attractive for their low dc-link voltage requirement. These low voltage requirements enable a single-stage dc-ac power conversion, which improves the overall efficiency, reliability, and power density of the system. A high voltage gain of 1.5 was demonstrated in recent boost type ANPC topology; however, it was achieved at the expense of high voltage stress on some of its switching devices. This brief proposes an improved topology with reduced voltage stress and a lower number of components while retaining the merits of high voltage gain. The proposed topology is a hybrid of a T-type inverter and an H-bridge, which require only one floating capacitor and one less power switch than the aforementioned topology. One floating capacitor with self-voltage balancing capability is integrated to generate 7 output voltage levels. The proposed topology is analyzed and compared with recent boost ANPC topologies. Experimental results are presented for validation.

Conventional active-neutral-point-clamped (ANPC) inverters exhibit low voltage gain that inherently leads to a high dc-link voltage requirement. An improved ANPC inverter that is capable of generating five voltage levels has recently reduced the dc-link voltage twofold to achieve unity gain. This led to the development of a single-stage dc–ac power converter with no frontend boost dc–dc converter. This article proposes novel ANPC inverters capable of unity or boosted voltage gain while generating higher voltage levels. The first topology can provide a voltage gain of 1.5 and extends the number of levels to seven by incorporating only one additional switch. The topology can also be extended by adding three switches and one floating capacitor to generate nine levels with unity voltage gain, or 11 levels with a voltage gain of 2.5. The proposed ANPC inverters and their operations are comprehensively discussed. Experimental results are provided to validate the feasibility of the proposed ANPC inverters.

This paper proposes a new family of multilevel inverter topology that is able to generate seven voltage levels by utilizing one or two floating capacitors and 10 power switches. This novel boost switched-capacitor seven-level inverter possesses voltage boosting capability with an achievable maximum voltage level 1.5 times the input direct current (dc) voltage. The generation of higher output voltage does not incur high-voltage stress on any power switch in this topology, as the peak inverse voltages of all power switches do not exceed the input source voltage. In addition, capacitor voltage balancing is not essential since the floating capacitors are effectively balanced during the charging and discharging processes. Furthermore, the proposed topology eliminates the need for multiple isolated dc sources, and a single dc source is sufficient in both its single-phase and three-phase topologies. The operating principle and steady-state analysis of the proposed topology are elaborated. Experimental results from a single-phase prototype are then presented to verify the validity of the proposed topology.

Single-source inverters with integrated switched-boost (SB) module and single-stage energy power conversion architecture have become a popular solution in many power electronics applications. This paper presents a novel topology of such types of inverters, which offers a modular design with a dynamic voltage boosting feature over a wide range of input voltages. The basic configuration of the proposed topology is able to generate three output voltage levels. It is comprised of an integrated SB module and a Quasi-H-Bridge (QHB) cell. The QHB cell consists of a self-balanced floating capacitor and four power switches, and the SB cell consists of a boost inductor and a single power switch. A five-level boosted output voltage can be achieved through the differential connection of two identical QHB cells utilizing a single SB module. The circuit description of the proposed topology, a comparative study, and the simulation and measurement results are given to verify the feasibility of this proposal.

Single-stage inverters with a common ac and de ground are emerging topologies which effectively eliminate the high-frequency common mode voltage. However, most of the existing common-ground-type inverters are based on switched-capacitor (SC) circuits which are inherently subjected to several important issues that lead to many practical limitations. Disadvantages such as high current spikes, high capacitor voltage ripples, and distorted ac output voltage with de offset are some significant challenges in these inverters. A new common-ground-type inverter that discard the use of SCs is therefore proposed in this paper. It consists of a single-inductor and an ac output capacitor that are controlled by 8 power switches. Sinusoidal ac voltage generation in both buck and boost modes can be achieved by controlling the inductor with a sinusoidal duty-cycle. Simulations are presented to verify the operation of the proposed topology.

This paper proposes the method to analyze the performance of wireless charging DC/DC resonant converters in various load conditions including the magnetic coupling effect. The equations for design performance analytical calculations are presented for series-series (SS) and series-parallel (SP) wireless charging DC/DC resonant converters. The equations can be applied in switching frequency sensitivity analysis at different magnetic strength and load resistance conditions to compare the performance of the resonant circuit topologies. The analytical calculation results can be used to size the voltage, current, and power rating of wireless charging resonant circuit components. The accuracy of the analytical calculation is validated by duty cycle control of wireless charging resonant converters in PLECS circuit simulation environment. Experimental results are obtained to support the conclusion drawn from the analytical solutions. The proposed method can be applied to study other wireless charging resonant converter topologies.

Switched-capacitor (SC) based inverter topologies are very attractive for renewable energy applications to step-up low dc voltage to higher ac voltage in single-stage without the need of front-end dc-dc converters, thus improving overall system efficiency, reliability and power density. This paper presents a new modular multilevel inverter based on switched-capacitor technique. Herein, series-parallel conversion technique is utilized to effectively self-balance the switched-capacitor voltages. Compared to other latest SC-based MLIs topology, the proposed structure features several advantages such as: low number of conducting semiconductor devices in load current paths and SC Charging paths. In addition, each capacitor is charged for at least half of the fundamental period that reduces voltage ripple and improves the inverter efficiency. Consequently, the presented inverter is suitable for high levels generation to achieve the rated ac voltage directly from a low voltage dc source. The merits and feasibility of the proposed inverter are verified through simulation for seven levels with sinusoidal PWM at different modulation indices and load conditions.

This paper presents the modelling and simulation of an 80kW AC microgrid network in MATLAB/Simulink environment. The network comprises a 50 kW photovoltaic system, a 10 kW fuel cell system, and a 20 kW battery energy storage system (BESS). The model is simulated under four operating conditions: (i) grid-connected mode, (ii) islanded mode (iii) islanded mode with excess power generation from Distributed Energy Resources (DERs) and (iv) islanded mode with limited power generation from DERs. Simulation results of the microgrid during various operating conditions were observed to investigate the charging and discharging characteristics of the battery and the total harmonic distortion of the power network during grid-connected mode and islanded modes.

In this paper, a novel 5-level inverter with common ac and dc ground is proposed for solar photovoltaic (PV) applications. The newly established common-ground-T-type (CGT-type) inverter is a single-stage topology restructured from the combination of a classical T-type inverter and a front-end three-level boost converter. Its distinctive topological structure can effectively eliminate the common mode voltage issue, prevent leakage currents, and ensure a continuous input current in PV systems. More importantly, it requires only two capacitors to realize an ac voltage which can be significantly boosted from a single dc source. A pulse width modulation (PWM) scheme is also established to undertake the following tasks simultaneously: charging of the boost inductor with a constant duty-cycle, and switching of two capacitors for 5-level ac voltage generation. The operation and feasibility of the proposed CGT-type inverter is analyzed and validated through simulation results.

SUMMARYUp to 30% of thyroid nodules cannot be accurately classified as benign or malignant by cytopathology. Diagnostic accuracy can be improved by nucleic acid-based testing, yet a sizeable number of diagnostic thyroidectomies remains unavoidable. In order to develop a protein classifier for thyroid nodules, we analyzed the quantitative proteomes of 1,725 retrospective thyroid tissue samples from 578 patients using pressure-cycling technology and data-independent acquisition mass spectrometry. With artificial neural networks, a classifier of 14 proteins achieved over 93% accuracy in classifying malignant thyroid nodules. This classifier was validated in retrospective samples of 271 patients (91% accuracy), and prospective samples of 62 patients (88% accuracy) from four independent centers. These rapidly acquired proteotypes and artificial neural networks supported the establishment of an effective protein classifier for classifying thyroid nodules.

To answer the increasing need for detecting and validating protein biomarkers in clinical specimens, proteomic techniques are required that support the fast, reproducible and quantitative analysis of large clinical sample cohorts. Targeted mass spectrometry techniques, specifically SRM, PRM and the massively parallel SWATH/DIA technique have emerged as a powerful method for biomarker research. For optimal performance, they require prior knowledge about the fragment ion spectra of targeted peptides. In this report, we describe a mass spectrometric (MS) pipeline and spectral resource to support data-independent acquisition (DIA) and parallel reaction monitoring (PRM) based biomarker studies. To build the spectral resource we integrated common open-source MS computational tools to assemble an open source computational workflow based on Docker. It was then applied to generate a comprehensive DIA pan-human library (DPHL) from 1,096 data dependent acquisition (DDA) MS raw files, and it comprises 242,476 unique peptide sequences from 14,782 protein groups and 10,943 SwissProt-annotated proteins expressed in 16 types of cancer samples. In particular, tissue specimens from patients with prostate cancer, cervical cancer, colorectal cancer, hepatocellular carcinoma, gastric cancer, lung adenocarcinoma, squamous cell lung carcinoma, diseased thyroid, glioblastoma multiforme, sarcoma and diffuse large B-cell lymphoma (DLBCL), as well as plasma samples from a range of hematologic malignancies were collected from multiple clinics in China, the Netherlands and Singapore and included in the resource. This extensive spectral resource was then applied to a prostate cancer cohort of 17 patients, consisting of 8 patients with prostate cancer (PCa) and 9 with benign prostate hyperplasia (BPH), respectively. Data analysis of DIA data from these samples identified differential expressions of FASN, TPP1 and SPON2 in prostate tumors. Thereafter, PRM validation was applied to a larger PCa cohort of 57 patients and the differential expressions of FASN, TPP1 and SPON2 in prostate tumors were validated. As a second application, the DPHL spectral resource was applied to a patient cohort consisting of samples from 19 DLBCL patients and 18 healthy individuals. Differential expressions of CRP, CD44 and SAA1 between DLBCL cases and healthy controls were detected by DIA-MS and confirmed by PRM. These data demonstrate that the DPHL supported that DIA-PRM MS pipeline enables robust protein biomarker discoveries.

Genetically modified FVIII‐expressing autologous bone marrow‐derived mesenchymal stromal cells (BMSCs) could cure haemophilia A. However, culture‐expanded BMSCs engraft poorly in extramedullary sites. Here, we compared the intramedullary cavity, skeletal muscle, subcutaneous tissue and systemic circulation as tissue microenvironments that could support durable engraftment of FVIII‐secreting BMSC in vivo. A zinc finger nuclease integrated human FVIII transgene into PPP1R12C (intron 1) of culture‐expanded primary canine BMSCs. FVIII‐secretory capacity of implanted BMSCs in each dog was expressed as an individualized therapy index (number of viable BMSCs implanted × FVIII activity secreted/million BMSCs/24 hours). Plasma samples before and after implantation were assayed for transgenic FVIII protein using an anti‐human FVIII antibody having negligible cross‐reactivity with canine FVIII. Plasma transgenic FVIII persisted for at least 48 weeks after implantation in the intramedullary cavity. Transgenic FVIII protein levels were low after intramuscular implantation and undetectable after both intravenous infusion and subcutaneous implantation. All plasma samples were negative for anti‐human FVIII antibodies. Plasma concentrations and durability of transgenic FVIII secretion showed no correlation with the therapy index. Thus, the implantation site microenvironment is crucial. The intramedullary microenvironment, but not extramedullary tissues, supported durable engraftment of genetically modified autologous FVIII‐secreting BMSCs.

This letter proposes an improved symmetrical 4-level submodule as a basic cell for generating multiple dc voltage levels. A hybrid cascaded multilevel inverter (HCMLI) topology is formed by the combination of n submodules and a full-bridge. A comparative analysis against the recent multilevel inverters reveals that the proposed topology requires less number of switches and dc sources. In addition, the proposed submodule reduces the number of conducting switch and gate driver requirements compared to the widely used half-bridge submodule. To validate the operation of the proposed HCMLI topology, experimental results of a 9-level single-phase inverter controlled by selective harmonic elimination pulse-width-modulation is presented.

The cascaded H-bridge multilevel inverter (MLI) requires separate isolated dc sources to generate more than three voltage levels and to generate higher output voltage. This paper proposes a new MLI topology that requires only one dc source and is capable of generating seven voltage levels with triple voltage boosting gain. Three H-bridges are interconnected through two bidirectional voltage blocking switches to enable the integration of two switched-capacitors. Unlike the existing two-stage structure switched-capacitor-based MLI, the proposed MLI is a single-stage topology. It alleviates the voltage stress across switches such that low voltage stress of not more than the dc source voltage is ensured on all switches. In addition, capacitors voltage balancing is achieved automatically during operation. The operation of the proposed MLI is analyzed followed by verification through simulation and experimental test of a low power/voltage prototype.

This paper focuses on a tuning-less model predictive control (MPC) strategy with unbalanced fault-ride-through capability for a three-phase modular multilevel converter (MMC). Three individual control stages are designed to cater for the multiple control objectives in MMC without the need for any weighting factor tuning. A conceptually simple power regulation approach which requires neither synchronous coordinate transformation nor grid-voltage phase angle detection is introduced into the proposed MPC. Meanwhile, two alternatives are proposed to the power regulation stage to adapt to the special needs under unbalanced grid fault. Neither of the alternatives involves any tuning work. In addition, a modified sorting algorithm is presented to resolve the problem of unnecessary switching transitions, which is inherent in conventional sorting algorithm. The proposed tuning-less MPC is capable of direct active and reactive power control, circulating current minimization, submodule capacitor voltage balancing, switching frequency reduction, and great resilience under balanced and unbalanced grid conditions. The presented simulation results confirm the effectiveness and feasibility of the proposed control method.

The grid connected renewable sources with their inherent intermittent behavior are inevitably imposing significant challenge to the controller design of the voltage source converters. Majority of the control approaches have ambiguous statements in relation to their performances under non ideal grid voltage conditions which is prevalent in renewable energy integrated weak micro-grid system. On that account, this paper provides a comprehensive overview of the existing table-based direct power control (DPC) schemes and review of their performance on the basis of power tracking and total harmonic distortion (THD) of the grid current under various grid conditions. In order to mitigate the drawback of the existing table-based DPC which result in high current THD under unbalanced or distorted voltage supply, this paper also proposed a novel concept of table-based DPC which adapted the extension pq theory into the virtual flux-based DPC. The feasibility of the proposed resilient virtual flux-based DPC (RVF-DPC) is verified by using MATLAB/Simulink and a comparative study is conducted to evaluate the superiority of the proposed controller with another three representative table-based DPC schemes. Simulation results have shown that, for an increased degree of unbalance and distortion of grid voltages, the proposed RVF-DPC is able to maintain the total harmonic distortions of the grid currents to a certain extent while keeping the constant power tracking performance.

This paper proposes a novel voltage level-based predictive direct power control (PDPC) strategy integrated with voltage sorting algorithm for a three phase grid-connected modular multilevel converter (MMC). The main advantage of the proposed control strategy, compared with the predictive current controllers, is that it does not need angular information of grid parameters. Therefore, it is simpler and able to get rid of rotary transformation and inner current loop. Contrary to the phase-by-phase control in predictive current controllers, the proposed control scheme advocates three-phase control. As a result, it achieves significant improvement in terms of smaller power ripples, more accurate tracking of power references, and less current harmonics. Further study reveals that the proposed voltage level-based PDPC exhibits less switching frequency irrespective of the magnitude of power references and power angles. Meanwhile, the capability of capacitor voltage balancing control and circulating current control in the proposed PDPC is as good as in the predictive current controllers. Some in-depth simulation comparisons with one of the existing predictive current controllers are given to validate the effectiveness of the proposed strategy.

A single-stage topology of a three-phase boost inverter known as split-source inverter (SSI) has recently been introduced in the literature. This topology suffers from high frequency current commutations across two diodes and complicated analysis since the inductor is charged with variable duty cycle. This paper presents a single-phase version of SSI with improvements in inverter topology as well as the pulse width modulation (PWM) technique. An inductor is connected to two MOSFETs operating at fundamental frequency to boost the voltage from input source to dc-link voltage. In the proposed hybrid quasi-sinusoidal and constant PWM, one of the full-bridge legs undergoes constant duty cycle switching while the other one undergoes sinusoidally varying duty cycle switching, with the former is accountable for charging and discharging of inductor while the latter is accountable for producing ac output. Therefore, the proposed topology with hybrid quasi-sinusoidal and constant PWM exhibits the merit of simplicity since the control of dc-link voltage and ac output is detached within the single-stage topology. It is not liable to the undesired high frequency current commutation. In addition, a wide range of ac output voltage is achievable in either buck or boost operation. Theoretical analysis is presented and verified through simulation and experimental results.

In this article, an optimal virtual flux predictive direct power control (VF-PDPC) is proposed for three-phase grid connected voltage source inverter (VSI) operating under unbalanced and distorted grid supply voltage. The concept of virtual flux and extension pq theory is introduced in the conventional PDPC, where the former enhances its resilience toward distorted supply voltage while the latter enhances its resilience toward unbalanced supply voltage. The inherent advantages of the conventional PDPC scheme, such as simple implementation, fast dynamic responses, and no demand of modulators are retained. Getting rid of the complicated positive and negative sequence extraction of grid components, power compensation, or any tuning work, the proposed optimal VF-PDPC achieves excellent power tracking capability, and sinusoidal grid currents with low harmonics under various grid voltage conditions. Simulation results are presented to verify the effectiveness of the proposed control scheme when compared to the conventional PDPC, conventional VF-PDPC, and optimal PDPC.

This paper deals with the design and simulation of Dual Active Bridge Multilevel Inverter (DABMI) based Model Predictive Direct Current Control (MPDCC) for grid connected application. To achieve multilevel output voltage waveforms, the second inverter will be supply with half of the dc-link voltage. Model predictive direct current control used to control the grid current component in order to achieve minimum grid current error. Modulation is unnecessary in this system because the switching pattern is produce by the possible switching that determined by the proposed MPDCC. The voltage vector which minimizes the cost function will be selected and applied to track the reference current. The performance of the proposed MPDCC is observe and implement by MATLAB/Simulink Software.

This paper presents a new transformerless inverter topology which is termed as a single-stage common-ground boost inverter (S2CGBI) for single-phase solar photovoltaic (PV) systems. The proposed topology provides a common-ground for both the dc source and ac output to eliminate the leakage current induced by the parasitic capacitance of PV cells. Voltage-boosting is made possible with the incorporation of only one inductor, which renders the realization of single-stage power conversion. The proposed pulse width modulation (PWM) technique is capable of charging the inductor with a constant duty-cycle while guaranteeing ac output generation. The operation of the proposed S2CGBI is analyzed. Simulation and experimental results are provided to validate the effectiveness of the proposed topology and modulation scheme.

This paper presents a model predictive control (MPC) for off-board plug-in electric vehicle (PEV) chargers with photovoltaic (PV) integration using two-level four-leg inverter topology. The PEV charger is controlled by a unified controller that incorporates direct power and current MPC to dynamically control decoupled active-reactive power flow in a smart grid environment as well as to control PEV battery charging and discharging reliably. PV power generation with maximum power tracking is seamlessly integrated with the power flow control to provide additional power generation. Fast dynamic response and good steady-state performance under all power flow modes and various environmental conditions are evaluated and analyzed. From the results obtained, the charger demonstrates less than 1.5% total harmonic distortion as well as low active and reactive power ripple of less than 7% and 8% respectively on the grid for all power flow modes. The PEV battery also experiences a low charging and discharging current ripple of less than 2.5%. Therefore, the results indicate the successful implementation of the proposed charger and its control for PV integrated off-board PEV chargers.

This work investigates a linear model predictive control (MPC) in conjunction with a voltage source inverter with a grid-interfacing passive filter. In an ideal grid, standard linear MPC demonstrates fast transient and excellent steady-state performance while respecting the imposed constraints. Nevertheless, its direct application onto the grid-connected converters operating with a distorted grid (e.g. islanded microgrid and marine vessel grid) or with applications that require harmonic current injection would encounter steady-state tracking error [1, 2], leading to unfulfilled application objectives. This shortfall is first demonstrated here using simulation, and then a solution based on plug-in repetitive control (RC) is proposed and investigated. With some assumptions simplifying this investigation, the resulted linear MPC with RC plug-in successfully mitigates the steady-state tracking errors while preserving the applicability of the multi-parametric quadratic-programming — the explicit implementation method that makes the linear MPC feasible in fast sampling applications. It is worth noting here that the notable features of MPC such as simple tuning, fast current response close to the physical limits of the system, and constraints consideration are retained and this makes the proposed control method a powerful alternative to the established grid-converter control techniques.

Cell therapy could potentially meet the need for pancreas and islet transplantations in diabetes mellitus that far exceeds the number of available donors. Bone marrow stromal cells are widely used in clinical trials mainly for their immunomodulatory effects with a record of safety. However, less focus has been paid to developing these cells for insulin secretion by transfection. Although murine models of diabetes have been extensively used in gene and cell therapy research, few studies have shown efficacy in large preclinical animal models. Here we report optimized conditions for ex vivo expansion and characterization of porcine bone marrow stromal cells and their permissive expression of a transfected insulin gene. Our data show that these cells resemble human bone marrow stromal cells in surface antigen expression, are homogeneous, and can be reproducibly isolated from outbred Yorkshire–Landrace pigs. Porcine bone marrow stromal cells were efficiently expanded in vitro to >1010 cells from 20 ml of bone marrow and remained karyotypically normal during expansion. These cells were electroporated with an insulin expression plasmid vector with high efficiency and viability, and secreted human insulin and C-peptide indicating appropriate processing of proinsulin. We showed that autologous insulin-secreting bone marrow stromal cells implanted and engrafted in the liver of a streptozotocin-diabetic pig that modeled type 1 diabetes resulted in partial, but significant, improvement in hyperglycemia that could not be ascribed to regeneration of endogenous β-cells. Glucose-stimulated insulin secretion in vivo from implanted cells in the treated pig was documented by a rise in serum human C-peptide levels during intravenous glucose tolerance tests. Compared to a sham-treated control pig, this resulted in significantly reduced fasting hyperglycemia, a slower rise in serum fructosamine, and prevented weight loss. Taken together, this study suggests that bone marrow stromal cells merit further development as autologous cell therapy for diabetes.

—This article proposes a novel zero-current switching series resonant inverter-fed voltage multiplier based high-voltage DC-DC converter. The series resonant inverter in the proposed topology has two power switches (insulated-gate bipolar transistors), two resonant capacitors, and only one high-voltage transformer with center-tapped primary windings. The power switches are connected in the form of a half-bridge network. The leakage inductances of the transformer's primary windings together with resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating power switches with an interleaved half-switching cycle. The secondary winding of the high-voltage transformer is connected to a voltage multiplier circuit to rectify and boost the voltage. The converter operates in discontinuous conduction mode, and its output voltage is regulated by pulse-frequency modulation. Therefore, all the power switches turn ON and OFF at the zero-current switching c...

This paper presents a new technique to minimize the torque ripples inherited in DTC of induction motor. The typical discrete-based DTC imposes delay time which frequently allows the torque to overshoot beyond hysteresis bands. This triggers the selection of reverse voltage vectors which, in turn, cause large torque decrements. The torque ripples become of great significance at low speeds where torque overshoot is most likely to occur due to steep positive torque slope. A multi-level DC link voltage is proposed to vary the DC voltage of Voltage Source Inverter (VSI) according to motor's speed. By varying the DC link voltage, the torque slopes can be controlled and, hence, the torque overshoots can mostly be avoided. Therefore, the torque ripples are significantly minimized. The viability of proposed technique has been validated using MATLAB/Simulink software. Results show the proposed technique yielded over 50% reduction in the RMS torque ripples while maintaining a low switching frequency.

Renewable energy demand increases due to environmentally friendly. Power electronics development enhance the power quality produced. Standalone application multilevel inverter can help in improve rural area which is no electrified. For a multilevel inverter, the output required low total harmonics distortion and voltage boosting character. However, the conventional multilevel inverter are high distortion with high switching frequency. This paper is presenting multilevel inverter with selective harmonics elimination on reduce total harmonics distortion (THD) apply in standalone concept. 9-level cascaded H-bridge multilevel inverter is applied with optimize harmonics stepped waveform (OSHW) to compare performance with sinusoidal pulse width modulation (SPWM). In OSHW, selective harmonics elimination is used to reduce the low harmonics component which is 3rd, 5th and 7th harmonics. Genetic algorithm are applied to solve the non-linear equation on solving the best switching angle. The result show OHSW have lower THD then SPWM. Meanwhile OHSW eliminated low harmonics component by the aid of genetic algorithm which exist due to the low switching frequency.

The nine-switch converter topology with 2 three-phase ac terminals has recently been utilized in the literature for ac to ac power conversion. Nonetheless, the existing control techniques essentially involve complicated linear controller design with special modulation schemes. This paper presents a simple yet high performance controller based on finite control set model predictive control (FCS-MPC) for ac/dc/ac power conversion using nine-switch topology. FCS-MPC algorithm is designed to control two ac terminals independently by making use of 27 combinations of voltage vectors. The first ac terminal which features an active front end rectifier with unity power factor is connected to power grid, while the second ac terminal is used to control three-phase load. Achievement of multiple control objectives within the same converter topology is made feasible by the use of cost function in FCS-MPC algorithm. Simulation results are presented to verify the functionality of the system.

This paper presents a new control scheme that permits arbitrary power sharing between parallel inverters connected to a microgrid operating in island mode. The scheme processes the active and reactive output power information from all the inverters in a central controller that calculates the set-points for each inverter, based on the desired ratios of their output powers. This necessitates adjustment of the inverters' terminal voltages (phase and magnitude) relative to the voltage at the common ac bus. The power-sharing scheme is validated using MATLAB/Simulink simulation from three three-phase parallel inverters connected to a number of passive loads.

This paper presents a boost-multilevel inverter design with integrated battery energy storage system for standalone application. The inverter consists of modular switched-battery cells and a full-bridge. It is multifunctional and has two modes of operation: 1) the charging mode, which charges the battery bank and 2) the inverter mode, which supplies ac power to the load. This inverter topology requires significantly less power switches compared to conventional topology such as cascaded H-bridge multilevel inverter, leading to reduced size/cost and improved reliability. To selectively eliminate low-order harmonics and control the desired fundamental component, nonlinear system equations are represented in fitness function through the manipulation of modulation index and the genetic algorithm (GA) is employed to find the optimum switching angles. A seven-level inverter prototype is implemented and experimental results are provided to verify the feasibility of the proposed inverter design.

Conventional pulse-frequency-modulated (PFM) zero-current switching series resonant (SR) inverter-fed voltage-multiplier-based high-voltage dc power supplies have nearly zero switching loss. However, they have limitations of poor controllability at light load and large output voltage ripple at low switching frequencies. To address these problems, this letter proposes a new control scheme that is based on digitally tuning tank capacitance and slightly varying pulse frequency of SR inverter. For the realization of the proposed control approach, the tank circuit of the resonant inverter is made up of several tank capacitors that are switched into or out of the tank circuit by electromechanical switches. By digitally modulating the tank capacitance, the output voltage changes in steps. The regulation of output voltage between two adjacent steps is achieved by slightly varying the pulse frequency. The proposed control scheme has several features, namely, a wide range of output voltage controllability even at light loads, less output voltage ripple, and less current stress on the inverter's power switches at light loads. Therefore, the proposed control approach alleviates most of the problems associated with conventional PFM. Experimental results obtained from a scaled-down laboratory prototype are presented to verify the effectiveness of the proposed system.

This paper deals with controlling a grid-connected dual-active bridge multilevel inverter for renewable energy integration. The concept of direct power control is integrated with model predictive control algorithm, which is termed as predictive direct power control, to control the real and reactive power injected into the power grid. The proposed multilevel inverter allows more options of feasible voltage vectors for switching vector selections in order to generate multilevel outputs, and thereby obtaining high power quality in the power grid. By using the predictive direct power control, simulation results show that the proposed multilevel inverter produces lower power ripple and manage to achieve currents with low total harmonic distortion which are well within the IEEE standard. The modeling and simulation of the system are implemented and validated by MATLAB Simulink software.

This paper presents a three-phase switched-battery multilevel (SBM) inverter for solar photovoltaic (PV) applications. The proposed inverter requires less number of power MOSFETs and gate drivers, and therefore, it is expected to be more compact and reliable than the conventional cascaded H-bridge multilevel (CHBM) inverter. For example, sixty units of power MOSFETs are required to construct a three-phase 11-level CHBM inverter, whilst a SBM inverter with the same number of levels needs only 27 units. The switching losses of the SBM inverter are expected to be lower than that in conventional PWM-controlled inverters because the power MOSFETs in the SBM inverter are switched at a much lower frequency. In addition, the proposed inverter has an integrated charge mode operation which is very suitable for solar PV applications. The performance of an 11-level SBM inverter has been evaluated using PSIM software and the simulation results confirm that the proposed inverter is capable of producing low total harmonic distortion (THD) AC voltages without the need of bulky filters.

This paper presents a new topology based on the series resonant converter (SRC) for high-voltage application. The proposed topology consists of two series resonant tanks. Each series resonant tank is built up by connecting a tank capacitor in series to a high-voltage transformer with the leakage inductance of the high-voltage transformer is absorbed as resonant inductor. Therefore, two high-voltage transformers are used in this topology with their primary windings are connected in series and secondary output are rectified and mixed before supply to load. The series resonant tanks are energized alternately by controlling two IGBT switches with pulse frequency modulation (PFM). This topology is operating in discontinuous conduction mode (DCM) with all IGBT switches are operating in zero current switching (ZCS) condition and hence no switching loss occurs. Moreover, this topology has low conduction loss as it requires only half number of IGBT switches compared to conventional full-bridge inverter based SRC. The effectiveness of the proposed topology is verified by simulation using OrCAD PSpice and the simulation results are presented.

This paper presents a novel topology based on the zero current switching series resonant (ZCS-SR) converter for high-voltage application. The proposed topology consists of two series resonant tanks. Each series resonant tank is built up by connecting a tank capacitor in series to a high-voltage transformer with the leakage inductance of the high-voltage transformer is absorbed as resonant inductor. Therefore, two high-voltage transformers are used in this topology with their primary windings are connected in series. The secondary output of both transformers are boosted by half-wave voltage multiplier and mixed before supply to load. The series resonant tanks are energized alternately by controlling two IGBT switches with pulse frequency modulation (PFM). This topology is operating in discontinuous conduction mode (DCM) with all IGBT switches are operating in zero current switching (ZCS) condition and hence no switching loss occurs. Moreover, this topology has low conduction loss as it requires only half number of IGBT switches compared to conventional full-bridge inverter based SRC. The effectiveness of the proposed topology is verified by simulation using OrCAD PSpice and the simulation results will be presented.

Nine-switch converter has been recently known for its higher compactness with reduced switch count as compared to the back-to-back converter. The readily available dc-link capacitor made it an appropriate alternative for ac/dc/ac conversion in microgrids. Regardless of the complicated Pulse Width Modulation control scheme, this paper proposes a novel predictive power control for the nine-switch converter which is simple and allows concurrent control of real and reactive power flow between two islanded microgrids. The proposed control scheme adopts the virtual flux vectors and a newly defined reactive power to improve the power quality under the existence of grid voltage disturbances, i.e., voltage unbalance and voltage distortion. Simulation results of the proposed predictive power control guarantee decoupled active and reactive power controls, fast response, accurate power and dc-link voltage tracking, and sinusoidal current waveforms with low harmonic distortions under the various grid conditions.

Summary High switching loss remains a predominant issue in conventional finite control set model predictive control (FCS-MPC) for voltage source inverter, aside from the uneven distributed loss between upper switches and lower switches. While maintaining the inherent simplicity and effective reference tracking capability of conventional FCS-MPC, a new FCS-MPC is proposed to acquire substantial improvement in switching loss reduction by choosing the optimal zero vector and two active vectors. Selection of the two active vectors is performed by considering two legs that have maximum and minimum output voltage at particular sampling instant, while the selection of the optimal zero vector is based on the switching states of the previous sampling instant. The proposed method also ensures uniformly distributed loss in each phase as well as between upper switches and lower switches. Further switching loss reduction by selecting the appropriate weighting factor in the cost function is investigated for both the conventional and proposed methods as well. A loss model is constructed in MATLAB/SIMULINK for analyzing quantitative switching loss, conduction loss, total harmonic distortion, and number of switching. The proposed method ensured its superior performance under different load angles and sampling periods, and all the results are verified through simulation.

This paper proposes the adoption of a multilevel dc link converter for a grid connected battery energy storage system in low voltage applications. The multilevel dc link converter is the simple upgrade of a typical two level voltage source converter with the incorporation of some cascaded modular chopper cells which constitute a switched-battery circuit. With the additional chopper cells, more candidates of voltage vectors are available for switching vector selection in power control. Compared to two level voltage source converter using a look-up-table direct power control or finite control set model predictive direct power control, the multilevel dc link converter which employed the latter power control tracks the reference power with much lower power ripple, as well as results in much lower total harmonic distortion in grid current. Therefore, the power quality can be improved significantly. Simulation results are presented to verify that a 3 level dc link converter is more effective than a two level voltage source converter for the grid-connected battery energy storage systems in both generating mode and charging mode.

This paper proposes a multi-output ZCS-SR inverter fed voltage multiplier based high voltage dc-dc converter to achieve wide range of controllability. The SR-inverter in the proposed system has four outputs that are connected to a single transformer linked load via four resonant capacitors each of which have distinct capacitance. Due to distinct values of resonant capacitors, the impedance of tank circuit and hence the power transfer rate is different for four outputs. Thus all the four inverter outputs are fed to load in parallel when maximum load power is desired and a single output that has highest tank circuit impedance is fed to load when lowest load power is required and vice versa. For the four inverter outputs there are sixteen possible combinations to feed them to load in parallel, thus the load power increase from its lowest value to highest in sixteen steps. Switching frequency is adjusted within in its narrow limits to adjust the voltage between two nearest steps. Proposed high voltage converter have several features such as wide range of control, less voltage ripple and low current stress on power switches. The proposed converter is simulated using PSPICE software and results confirm its better performance.

This paper presents the use of a digitally tuned resonant capacitance control with narrow range frequency modulation to regulate the output voltage of a zero current switching series resonant (ZCS-SR) inverter-fed transformer-linked DC-DC converter for X-ray power supply application. In this control scheme, the series resonant inverter consists of several capacitors which are switched into and out of resonant tank circuit by relays. The capacitance of the resonant tank is modulated digitally by controlling the closure of relays which causes the output voltage to increase or decrease in steps. The output voltage in between any two adjacent steps is adjusted by varying the switching frequency in a narrow range. By modulating both resonant tank capacitance and switching frequency, it is able to regulate the output voltage over a wide range. Furthermore, the switching losses of the proposed system are eliminated with all switches operating under soft switching conditions over the entire range of output voltage. Verification of the proposed system is done by computer simulation using Orcad PSPICE.

In this paper, a novel double series resonant high-voltage dc-dc converter with dual-mode pulse frequency modulation (PFM) control scheme is proposed. The proposed topology consists of two series resonant tanks and hence two resonant currents flow in each switching period. Moreover, it consists of two high-voltage transformer with the leakage inductances are absorbed as resonant inductor in the series resonant tanks. The secondary output of both transformers are rectified and mixed before supplying to load. In the resonant mode operation, the series resonant tanks are energized alternately by controlling two Insulated Gate Bipolar Transistor (IGBT) switches with pulse frequency modulation (PFM). This topology operates in discontinuous conduction mode (DCM) with all IGBT switches operating in zero current switching (ZCS) condition and hence no switching loss occurs. To achieve fast rise in output voltage, a dual-mode PFM control during start-up of the converter is proposed. In this operation, the inverter is started at a high switching frequency and as the output voltage reaches 90% of the target value, the switching frequency is reduced to a value which corresponds to the target output voltage. This can effectively reduce the rise time of the output voltage and prevent overshoot. Experimental results collected from a 100-W laboratory prototype are presented to verify the effectiveness of the proposed system.

Conventional pulse frequency modulated (PFM) zero current switching (ZCS) series resonant (SR) inverter fed high voltage dc power supplies have nearly zero switching loss. However, they have limitations of poor controllability at light loads and large output voltage ripple at low switching frequencies. To address these problems, this paper proposes a combined resonant tank capacitance and pulse frequency modulation based control approach. For the realization of the proposed control approach, the tank circuit of the resonant inverter is made up of several resonant capacitors that are switched into or out of the tank circuit by electromechanical switches. The output voltage of the converter is regulated by digitally modulating the resonant tank capacitance and narrowly varying the switching frequency. The proposed control scheme has several features, namely a wide range of controllability even at light loads, less output voltage ripple, and less current stress on the inverter's power switches at light loads. Therefore, the proposed control approach alleviates most of the problems associated with conventional PFM. Experimental results obtained from a scaled down laboratory prototype are presented to verify the effectiveness of the proposed system.