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Additive manufacturing (AM) has been revolutionizing the manufacturing industry due to its ability to significantly reduce waste and produce components with intricate shapes. Laser Ultrasonics (LU) is a non-contact and couplant free method to generate and detect ultrasound. LU can accommodate complex component shapes; thus, it has the potential to provide a reliable in-process inspection method for AM components. In recent years the development of Laser Induced Phased Arrays (LIPAs) helped overcome the inherently low signal amplitudes of LU at the non-destructive, thermoelastic regime. In this paper, the Full Matrix Capture data acquisition method is used and a LIPA of 68 elements is synthesized in post processing. The Total Focusing Method imaging algorithm is applied for ultrasonic imaging. The technique is demonstrated on a highly scattering titanium alloy Wire Arc Additive Manufactured (WAAM) component producing high quality ultrasonic images, accurately imaging defects at depths up to 10mm below the inspection surface.

We show that a MAPbI 3 film that was encapsulated has survived the space environment on the International Space Station for a total of approximately 10 months on orbit with little to no chemical degradation. This effort is part of our ongoing efforts to determine the feasibility of MAPbI 3 -bearing solar cells for space applications. This sample was part of the thirteenth flight of the Materials International Space Station Experiment (MISSE-13), which flew from mid-March, 2020 until mid-January, 2021. We determined the robustness of the material through the use of transmission spectrophotometry. To our knowledge this report represents the longest known flight in space of a MAPbI 3 film.

In this paper, a set of the most employed machine learning (ML) algorithms were trained and tested to assess which ones present the highest accuracy in predicting the layer geometry of the Ti-6Al-4V processed by plasma transfer arc deposition. Wire and arc additive manufacturing brings about the possibility of manufacturing large and robust components based on metal wires. One of the critical aspects to take into account during the manufacturing process is the layer geometry. Bead geometry depends on several processing parameters, e.g., arc voltage, welding current, travel speed, wire feed speed, and gas flow rate. The algorithms that better adjusted the prediction were multilayer perceptron with five hidden layers, linear support vector regression, and boosting regressors, which combine multiple models to reduce overfitting risk.

In this paper, the simulation and design of power converter suitable for shipboard battery energy storage converter is investigated. The converter can perform high-power charging and controllable discharging for the large-capacity on-board energy magazine. To provide unity generator power interface, a three-level neutral point clamp converter is selected as the active front-end. The bidirectional dual active bridge converter is selected to provide the second stage regulation of charging power of different voltage level. The simulation results demonstrate that the system can regulate power to charge shipboard battery, perform high power factor energy interaction with three-phase-supply; the bidirectional power flow capability of the energy storage converter is also verified through simulation.

Here we present our ongoing and preliminary results into the durability of NH 3 CH 3 PbI 3 (MAPI) films undergoing a high humidity test as outlined in the AIAA-S111 standard for qualification of space solar cells. The samples were encapsulated in a space qualified 2-part silicone (DC-93500) and coverglass lamination as a protectant and select cohorts were also coated with SiO 2 barrier layers and a silane surface modifier. A first study using a 2-part epoxy encapsulant was used to model the diffusion behavior of moisture through an encapsulant to determine feasibility and indicated an approximate border removal area for robustness. The ongoing test utilizes transmission spectra as a proxy for material dissociation. Few samples show significant degradation up to 880 hours, typically the encapsulated samples as produced show the least, the samples with the silane surface modifier show the most. These data are being processed and quantitative statistics will be shown.

This paper presents a strategy for non-contact measurement of the conductivity of Aluminum wires used in wire + arc additive manufacture. A cylindrical electromagnetic sensor consisting of coil pair (an excitation and a receiver coil) is designed and the change in the mutual inductance due to the presence of the wire inside the sensor is measured at multiple frequencies. A novel calibration method is proposed. It was found that the calibrated inductance agrees well with the inductance measured by a commercial instrument. Moreover, the phase of the inductance is linearly related to the conductivity of the wire measured via a contact four-terminal measurement method. This technique can be potentially applied to the real-time in-situ inspection of metal wires by measuring their conductivity variation, which could contribute to the quality control of wire + arc additive manufacture processes.

Modular Multilevel Converter (MMC) performance may be adversely affected by passive component tolerances, such as submodule capacitance and arm inductance variations. Depending on control strategies, the differences in equivalent capacitances and/or inductances of the upper and lower arms of one phase-leg can cause unequal power distribution between upper and lower arms. Assuming passive component tolerances ranging between ±10%, this paper presents a comprehensive assessment of the internal/external coupling effects due to the passive component tolerances within one phase-leg, under the control of common MMC balancing methods. A novel control strategy is proposed to suppress the fundamental component that arises in the dc-link current due to such tolerances, and its effectiveness is demonstrated via simulation and experimentation. The investigation shows that voltage-based common and differential mode balancing control provides effective ac offset suppression while the proposed method offers superior performance in terms of dc-link fundamental current ripple suppression. ACKNOWLEDGMENT This publication was made possible by NPRP grant NPRP (9-092-2-045) from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. Scopus

This paper deals with the power dispatch and direct voltage control in multiterminal high voltage direct current (MT-HVDC) systems. Generalized voltage droop (GVD) control is adopted for voltage source converters (VSC)s of a MT-HVDC system. A mechanism has been designed based on the power ratio within the GVD controlled stations to achieve flexible autonomous coordination control among VSC-HVDC stations, without need for communication. In this paper, several alternatives are considered to guarantee fault ride through of onshore converter stations. The performance of the proposed control strategy is analyzed with time-domain dynamic simulations, in an EMDTC/PSCAD platform, and experimentally validated. Results demonstrate the robust performance and capabilities of the proposed control strategy during changes in the power demand of the ac grids, unexpected change in wind power generation, and eventual permanent VSC-HVDC station disconnection.

High-efficiency power converters have benefits of minimizing energy consumption, reducing costs, and realizing high power densities. The silicon super-junction MOSFET is an attractive device for high-efficiency applications. However, its highly non-linear output capacitance and the reverse recovery properties of its intrinsic diode must be addressed when used in voltage source converters. A dual-mode switching technique operating in conjunction with intrinsic diode deactivation circuitry is proposed in this paper. The technique is demonstrated in an 800-W inverter-leg configuration operating from a 400-V DC voltage rail and switching at 20 kHz. Intended applications include machine drives. The full-load efficiency reaches approximately 98.7% and no forced cooling is needed.

This paper studies a dc-dc converter topology dual to the ac autotransformer for medium and high voltage dc-dc conversion. Operation with trapezoidal modulation is analyzed where the dc autotransformer is built of transition-arm bridges. This structure features less power electronics installation and energy storage capacity as compared to counterparts operating in sinusoidal modulation. It also permits the use of low-loss devices such as thyristors or Insulated Gate Commutated Thyristors (IGCTs), promising high efficiency. The paper investigates this topology in steady state as well as DC fault blocking capability. � 2018 IEEE. Scopus

This paper proposes a hybrid converter for medium-voltage six-phase machine drive systems that mixes the operation of a traditional two-level voltage-source inverter and the modular multilevel converter (MMC) to enable operation over a wide frequency range. Topologically, the proposed converter consists of nine arms resembling two sets of three-phase MMCs with three common arms, yielding a nine-arm MMC with a 25% reduction in the number of employed arms compared to a traditional dual three-phase MMC. The multilevel property of a standard MMC is emulated in the proposed converter, however on a two-level basis, resulting in a stepped two-level output voltage waveform. The proposed converter has a reduced footprint with advantages of small voltage steps, modular structure, and ease of scalability. Further, it is able to drive high-power six-phase machines within low operating frequencies at the rated torque. The operating principle of the converter is elaborated, and its modulation scheme is discussed. The features of the proposed converter are verified through simulations and experimentally. - 2018 IEEE. Scopus

Inverter-Based Distributed Generation (IBDG) units are typically coupled to the grid via three-phase Voltage Source Converters (VSCs). The IBDGs may pollute utility with the injected harmonic currents. In order to meet the standards' requirements, the necessity of grid-integration through passive filters supports a reduction of harmonic currents. This paper presents a performance assessment for the harmonic reduction introduced on the grid-side inductor when using LLCL filter with a single LC-trap, and LLCL filter with a dual LC-trap, named here L-2LC-L filter. Moreover, it can be deduced theoretically, that the higher the number of the LC parallel branches, the lower the grid-side inductor. When connected between the VSC and the grid, these types of filters may introduce resonance. Therefore, a passive or active damping technique may be applied to suppress the resonance. This paper presents also through simulation, analysis, and experiment, an active damping approach for LCL filter as well as for a filter with single trap (LLCL) and for a filter with dual LC trap (L-2LC-L) with grid-interfaced three-phase VSC. Qatar National Research Fund (QNRF) No. NPRP X - 033 - 2 - 007

A modular multilevel converter (MMC) configuration is presented as a medium-voltage high-power drive for variable-speed applications incorporating symmetrical six-phase machines. The topology employs six standard MMC phase-legs feeding two isolated groups of three-phase machine windings, each with 60° spatial phase-displacement. A novel concept of ripple-power decoupling between adjacent sub-modules (SMs) of MMC phase-legs, while feeding machine windings in a spatial phase-opposition fashion, is realized through isolated dc-dc converter modules. This concept offers a significant reduction in SM capacitance, while eliminating the problem of SM capacitor wide voltage fluctuations, especially at low operating frequencies. Furthermore, the proposed configuration can efficiently operate at near zero frequency, therefore a machine speed-range from zero speed up to the rated speed is possible under rated torque operating conditions. The proposed MMC configuration is analyzed in detail, and its performance is validated using both simulation and experimentation. Scopus

When a pole-to-pole dc fault occurs in a multi-terminal HVDC system, it is desirable that the stations and dc solid-state transformers on healthy cables continue contributing to power transfer, rather than blocking. To reduce the fault current of a modular multilevel-converter-based dc solid-state transformer, active fault current control is proposed, where the dc and ac components of fault arm currents are regulated independently. By dynamically regulating the dc offset of the arm voltage rather than being set at half the rated dc voltage, the dc component in the fault current is reduced significantly. Additionally, reduced ac voltage operation of the dc solid-state transformer during the fault is proposed, where the ac voltage of transformer is actively limited in the controllable range of both converters in the transformer to effectively suppress the ac component of the fault current. The fault arm current peak and the energy absorbed by the surge arrester in the dc circuit breakers are reduced by 31.8% and 4.9%, respectively, thereby lowering the capacities of switching devices and circuit breakers. Alternatively, with the same fault current level, the dc-link node inductance can be halved by using the proposed control, yielding lowered cost and volume. The novel active fault current control mechanism and the necessary control strategy are presented and simulation results confirm its feasibility.

This paper presents a controlled transition bridge (CTB) converter that uses a non-trapezoidal amplitude modulation in attempt to reduce filtering requirement in high-voltage direct current (HVDC) transmission systems. To achieved variable output ac voltage (modulation index control) over wide range, as expected during a black-start, cell capacitor voltage balancing of the CTB converter is decoupled from the modulation index and power factor by injecting a 3rd harmonic component into the modulating signal of each phase. This 3rd harmonic extends the region around voltage zeros, where the cell capacitor voltages can be balanced, by ensuring that each limb is alternatively clamped to the positive and negative dc rails, every fundamental period to allow recharge of the cell capacitors from the dc link. The effective of the presented non-trapezoidal modulation method for operation of the CTB converter over full modulation and power factor range is confirmed by simulation, including its scalability to high applications.

This paper presents analysis and control of D converter, which has continuous input and output current to obtain maximum power transfer from a photovoltaic (PV) system. Examining the maximum power involves optimization and control techniques that ensure maximum power extraction enhancement. Traditional converters have rather high input ripple current that originates considerable loss of power extraction when linked to photovoltaic panels. Operating with zero input ripple current enlarges the power obtained from the PV panel without employing electrolytic capacitor. Experiment and simulation of the converter performance support and extol the system concept and establish a balanced view among several types of used controllers as well.

The concept of HVDC taps drawing small amount of power from HVDC lines to the rural places has been considered for several decades. Most of the earlier tap converters were limited by its loss, cost, reliability, and control difficulties. However, in this paper, the emerging modular multilevel converter (MMC) is adopted as the series HVDC tap, which reveals significantly improved performance and feasibility. Circuit structure and operating principle of this tap are presented, and the control considerations are also discussed. Simulations are given to demonstrate effectiveness of the MMC tap and the proposed control strategies. This tap topology is very promising to find practical use in future HVDC tapping applications.

Voltage balancing between sub-module (SM) capacitors is essential for reliable operation of the modular multilevel converter (MMC). To facilitate design and understanding of the balancing controllers, this study presents an energy transfer analysis for MMC, which explains how the energy can be independently transmitted from/to one phase, between the upper and lower arms, and among the SMs, of an MMC. Using this analysis, the variables which can be utilized to achieve capacitor voltage balancing are identified. Validity of this study has been verified by experimental results based on a three-phase MMC prototype.

A hybrid MMC with reduced three-level (TL) cells is proposed. As well as the dc fault blocking capability, the proposed hybrid MMC provides the benefits of: lower conduction losses; fewer diode and switching devices, and; fewer shoot-through modes. Guidelines are developed to determine the required number of three-level cells to block a dc-side fault. It is also demonstrated that a further reduction in the number a three-level cells is possible if a rise in cell current and voltage is acceptable. This reduction is investigated. A lower number of three-level cells reduces losses and capital cost further. The hybrid MMC with the reduced number of three-level cells proves to be the most attractive approach compared with other MMCs and hybrid MMCs. The semiconductor count and conduction loss are 92.1% and 90.3% respectively of that of the MMC based entirely on full-bridge cells, without exposing the semiconductors to significant fault currents and over-voltages. The simulation results demonstrate the feasibility of the proposed hybrid converter.

This paper proposes a ring dc node configuration for more reliable multi-terminal dc grid fault protection. The proposed ring node is tolerant to the loss of one dc circuit breaker. It results in reduced steady state current flow in node branches relative to a conventional star node connection. This reduces on-state losses of solid-state circuit breakers, as well as any dc-dc converters to be used to administer dc fault blocking in addition to voltage matching. The short circuit breaking capacity of each utilized circuit breaker is also reduced since current stresses are distributed among dc breakers within the ring node. The proposed node configurations are of importance for medium and high voltage dc grids interfacing renewable sources (for example, offshore wind) to the onshore ac grid.

This paper proposes a new configuration for static synchronous compensator (STATCOM) based on the ac-side voltage doubling voltage source converter (ACVD-VSC), which has twice of the dc-link voltage utilization as two-level VSC, hence improved power density per unit dc-link voltage. This means its dc voltage limit for reactive power generation is higher than that using conventional two-level VSC. Therefore, extended reactive power control range is resulted for the proposed solution. Also the ACVD converter has zero dc common mode voltage between the ac neutral point and the dc-link negative terminal, reducing the insulation level for the interfacing transformer when the negative dc bus is grounded. The basic operation principles of ACVD-VSC are reviewed. Then, it is used to perform voltage or power flow control as shunt compensators.

This paper discusses the impact of fill factor on the input current ripple of the photovoltaic module and the loss effect on power extracted. Photovoltaic module's P-V curve produces exponential curve. The curvature of this curve indicates the fill factor of the particular cell; hence, by increasing the fill factor, the available extracted power increases. Yet, this paper states that losses due to photovoltaic current increases by increasing the fill factor.

This paper presents an attractive control scheme that decouples cell capacitor voltage regulation of the FB-MMC from the dc link voltage regulation. This is achieved by manipulating both ac and dc components of modulation functions. The dc component of modulation function is used to regulate the cell capacitor voltages independent of the dc link voltage, while the magnitude and phase of modulation function ac component are manipulated to control active and reactive powers FB-MMC exchanges with the ac grid. The significance of this control scheme is that it permits the FB-MMC to operate with variable dc link voltage, including negative dc link voltage and zero, while full control over the power FB-MMC exchanges with ac grid is retained. Additionally, this paper provides comprehensive discussion of MMC fundamental theory, including logical and mathematical derivations of the basic relationships that governed its operation and modulation. The validity of the presented control scheme is confirmed using simulations.

Offshore wind farms provide benefits over onshore farms in terms of the amount of generated energy and environmental impact. Cost efficient energy transmission is one of the challenges of such installations. In this context, direct connection of DC wind turbines to the transmission line is a promising solution. This paper proposes a novel energy conversion scheme for the direct connection of the DC wind turbines to the transmission line. In addition, a brief comparison between two DC-DC converters is presented to establish the most suitable topology for the modular DC-DC converter required by the proposed energy conversion scheme.

The operation state of photovoltaic Module Integrated Converter (MIC) is subjected to change due to different source and load conditions, while state-swap is usually implemented with flow chart based sequential controller in the past research. In this paper, the signatures for different operational states are evaluated and investigated, which lead to an effective control integrated finite state machine (CIFSM), providing real-time state-swap as fast as the local control loop. The proposed CIFSM is implemented digitally for a boost type MIC prototype and tested under a variety of load and source conditions. The test results prove the effectiveness of the proposed CIFSM design.

This paper proposes dc current offset compensation technique of grid connected inverters which may applicable to medium-scale solar farms, or any group of grid connected inverters confined within a relatively small area. DC current injection into ac grid severely affects distribution system components such as isolation transformers, measurement units and protective relays. The proposed dc current offset compensation technique exploits a simple proportional-resonance (PR) controller that aims to suppress dc offsets to zero in the output currents of grid-connected inverters before entering the main 50/60Hz interfacing transformer. By employing this technique, the capital cost of a medium-scale solar farm is reduced since it enables transformerless operation of all inverters within the farm, and uses only one power transformer at point of common coupling. Additionally, this technique does not rely on high-precision current measurement devices nor uses any form of complex transformer. Simulation and experimentation are used to demonstrate the practicability of the proposed system.

Wireless power transmission technology is gaining more and more attentions in city transportation applications due to its commensurate power level and efficiency with conductive power transfer means. In this paper, an inductively coupled wireless charging system for 48V light electric vehicle is proposed. The power stages of the system is evaluated and designed, including the high frequency inverter, the resonant network, full bridge rectifier, and the load matching converter. Small signal modeling and linear control technology is applied to the load matching converter for input voltage control, which effectively controls the wireless power flow. The prototype is built with a dsPIC digital signal controller; the experiments are carried out, and the results reveal nature performances of a series-series resonant inductive power charger in terms of frequency, air-gap length, power flow control, and efficiency issues.

This paper presents a generalized switching function model of the modular multilevel converter (MMC) that can be used instead of MMC electromagnetic transient simulation model for full-scale simulations of high-voltage dc (HVDC) and flexible ac transmission systems (FACTS). The proposed method is computationally more efficient and numerically stable than its electromagnetic transient simulation counterpart, and it is applicable for wide range of studies, including ac and dc network faults. The proposed switching function model is packaged in a graphical form to suit various simulation platforms such as Simulink and PSCAD. The validity of the presented model is confirmed using simulation and its scalability has been demonstrated on MMC with 301 cells per arm, considering power reversal during normal operation and dc short circuit fault.

This paper proposes a dc/ac converter topology where each phase leg comprises a conventional series switch valve in one arm and a series connection of half-bridge chopper cells in the other arm. Operation with trapezoidal modulation is analyzed where the half-bridge modules have a reduced footprint and silicon area compared to standard modular multilevel converter modules. Furthermore, no arm inductance is required. The utilization of the proposed converter topology in medium and high voltage front-to-front dc-dc converter topologies is analyzed. Simulations investigate key features of the converter in comparison to other published topologies.

Φ Abstract - This paper investigates the adverse effects of unbalanced phase voltage on the steady-state performance of a five-phase induction motor with three different stator winding connections, namely; star, pentagon, and pentacle. Imbalance may occur due to current interruption of one-phase, two adjacent phases, or two non-adjacent phases. Steady-state models based on symmetrical components theory are derived for the three connections. Voltage unbalance factors are calculated using the IEC standard definition for a three-phase induction motor, which is the negative to positive sequence ratio.

This paper addresses the issues of dc voltage matching and dc fault protection in potential super-grids. An approach for high power dc-dc conversion is proposed and analyzed. A front-to-front connection of modular-multilevel converters (MMC) forms a dual active bridge (DAB)-like structure. Near two-level operation is achieved by sequential switching of half-bridge chopper cells. This alleviates dv/dt stress exercised by two-level DAB configurations on the ac stage. The operating mode, switching patterns necessary are distinct from conventional MMC. Furthermore, common-mode currents, cell capacitance size, arm inductances are significantly reduced. The considered structure is shown to be useful for high power applications due to the low switching frequency, modularity, reliability and dc fault isolation capability. Various operation aspects are illustrated using simulations. A reduced-scale test rig provides an experimental proof of the concept.

This paper uses a scaled down version of the mixed cells modular multilevel converter (MMC) to discuss its modulation and capacitor voltage balancing method, and investigates its AC and DC fault ride-through capability. It has been found that the mixed MMC is resilient to both AC and DC network faults, which are necessary for next generations of highly meshed multi-terminal HVDC grids. The power losses comparison conducted in this paper has shown that the mixed cells MMC and three-level cells MMC achieve DC fault reverse blocking capability at reduced on-state losses than full-bridge MMC and alternative arm MMC.

The mammalian brain is a highly complex system with levels of organization that extend from nucleotides to large networks that generate adaptive behavior. To test our understanding of brain function we need to assemble and model interactions across levels. We are doing this for a genetically diverse family of BXD strains. This family has been densely genotyped and phenotyped for thousands of brain-related behavioral, cellular, and molecular traits making this population particularly amenable to multi-scale analysis. Here we provide an example of this type of analysis starting with a well defined trait-cholinergic interneuron number in the dorsal striatum. We show strong associations between cholinergic neuron numbers and alcohol and drug response phenotypes among the BXD population and map part of the variation in coexpression to chromosomes1 and 12. Polymorphisms in Lrfn5 may be responsible for trait variation that maps to the chromosome 12 locus.

Control techniques, applied to single-phase two-stage grid-connected photovoltaic (PV) systems, mainly achieve functions of maximum power point tracking (MPPT), voltage adjustment at inverter DC-link, and grid current control. Conventional control techniques require measurements of PV voltage and current, DC-link voltage, and grid voltage and current. Commonly, sensorless techniques are proposed to simplify system implementation and decrease its entire size and cost. However, most focus on eliminating PV voltage and/or current sensors. In this paper, a sensorless technique is proposed which keeps PV sensors, but eliminates the expensive high DC-link voltage sensor by mitigating the inverter DC-link voltage control loop. Alternatively, voltage regulation at inverter DC-link is achieved through power balance guarantee at this link. Hence, control complexity is minimized and system stability is enhanced. Moreover, the entire system implementation is simplified and its dynamic response is improved during sudden irradiance changes. Simulation work is carried out to verify the effectiveness of the proposed technique when compared to the conventional one regarding their transient and steady-state performance under varying irradiance conditions.

Power passive filters are a standard solution for gridcurrent harmonics attenuation. However, these types of filters may cause a resonance between the inverter and the grid. Passive and active damping techniques are employed for resonance ttenuation. Efficiency concerns have set active damping techniques as promising solution for the resonance problem compared to the passive damping techniques. In this paper, the characteristics, performance, and effect of different active damping schemes applied to an LLCL passive power filter interfacing a three-phase voltage source inverter (VSI) to the grid is investigated. Stablity analysis is conducted for the LLCL-based grid-connected VSI. The presented concept has been elucidated by simulation results using Matlab/Simulink platform. NPRP grant [4-250-2-080] from the Qatar National Research Fund (a member of Qatar Foundation). Scopus

Among various photovoltaic (PV) maximum power point tracking (MPPT) techniques, variable-step incremental conductance (Inc.Cond.) method is widely employed with the merits of high tracking accuracy and fast convergence speed. Yet, mathematical division computations are mandatory for the algorithm's structure which in turn adds more complexity to its implementation. Moreover, conventional variable step, depending on the change of the array power with respect to the array voltage, encounters steady-state oscillations and dynamic problems especially under sudden irradiance changes. This paper proposes a modified variable-step Inc.Cond. MPPT technique featuring division-free algorithm, simplified implementation, and enhanced transient performance with minimal steady-state power oscillations around the MPP. Simulation and experimental results are presented for concept realization and performance evaluation.

This paper presents the effect of the input current ripple on the photovoltaic source efficiency. The input and output current can be either continuous or discrete, with or without ripple, giving either continuous or discrete energy flow hence affecting the input source efficiency or the output load application. This paper considers the influences of the converter input current ripple on the photovoltaic module and the loss of power extracted, in conjunction with converter efficiency, thus losses in the overall system efficiency. With input current (or voltage) ripple, there is no maximum power point; instead, there is maximum power track or locus curve. When the input current ripple reduces to zero, the maximum power curve becomes a point, specifically the DC maximum power point.

Besides research on reliability, efficiency and grid impact challenges imposed by the wind energy industry, research on compact design of multi-modular interfacing DC/DC converters is growing rapidly. This paper addresses the application of multi-modular resonant-type DC/DC converters for offshore wind high power HVDC transmission systems. The attractive feature about resonant converters is their soft switching characteristics which enables higher frequency operation and hereby reduced converter footprint. The paper focuses on one important aspect leading to increased power density; the output filter design. New analytical expressions are derived for filter ripple content in DC/DC resonant converters. This has not been investigated previously. Further mathematical relations are derived for multi-module interleaved operation of DC/DC resonant converters with both series and parallel connections of output filter. Results are demonstrated to validate the derived design equations highlighting the advantage of interleaving with multi-modular structures in achieving highly compact designs.

Although maximum power point tracking (MPPT) is crucial in the design of a wind power generation system, the necessary control strategies should also be considered for conditions that require a power reduction, called de-loading in this paper. A coordinated control scheme for a proposed current source converter (CSC) based DC wind energy conversion system is presented in this paper. This scheme combines coordinated control of the pitch angle, a DC load dumping chopper and the DC/DC converter, to quickly achieve wind farm de-loading. MATLAB/Simulink simulations and experiments are used to validate the purpose and effectiveness of the control scheme, both at the same power level.

A novel algorithm is presented based on linear equation solution space theory to calculate the classic three-phase to three-phase matrix converter PWM duty cycles. It algebraically reveals an intrinsic two useful degrees of freedom in modulating the duty cycles; also discloses a general method of how to deal with distortion in the input voltage or output current whose form and harmonics quantity are not obvious. Derivation of the algorithm, its control techniques and potential are given; comparisons to the Venturini algorithm and the space vector modulation method are given, simulation and experimental results confirm the algorithm.

This paper presents a new three-phase dc-ac inverter based on the basic Cuk converter. The main feature of the proposed topology is the fact that the energy storage elements as inductors and capacitors values can be reduced in order to improve the reliability, reduce the size, and the total cost. Moreover, the bucking-boosting inherent nature of the Cuk converter, depending on the time-varying duty ratios, provides more flexibility for stand-alone and grid connected applications when the required output AC voltage is lower or greater than the DC side voltage. This property is not found in the conventional current source inverter (CSI) when the DC input current is always greater than the ac output one or in the conventional voltage source inverter (VSI) as the output ac voltage is always lower than the dc input one. Averaged large and small signal models are used to study the Cuk nonlinear operation. Basic structure, control design, and MATLAB/SIMULINK results are presented in this paper. The new three-phase DC-AC inverter is very convenient for PV applications where continuous average input currents are required for appropriate Maximum power Point Tracking (MPPT) operations.

These keynote speeches discuss the following: Advances (Innovations) in Neurotechnology; Implantable Microsystems for the Management of Trauma; Emerging trends for decentralized e-health services in smart cities; Wellness, Disease and Public Health Informatics: Multidimensional Global Threats with Local Impact; An Overview of M-Health Medical Video Communication Systems; Somatosensory Brain Machine Interfaces; Brain on a Chip: From Patterns to Circuits with Information Transfer; Systems Genetics: Experimental and Computational Challenges; Challenges and Opportunities in Cardiovascular Health Informatics.

The steady-state and dynamic performances of a new high-power variable speed wind-energy conversion system (WECS) that uses a six-phase permanent magnet synchronous generator (PMSG) with twelve-pulse back-to-back pulse width modulated current source converters is assessed. The proposed WECS inherently has all the features of existing systems based on voltage source converters, such as voltage control and fault ride-through capability, but with increased reliability and improved ac side waveform quality, benefiting from the three-winding phase shifting transformer for further attenuation of the low-order harmonics. PSCAD/EMTDC simulation is used to assess the steady-state and dynamic behaviours of the proposed system under different operating conditions. Experimental results, obtained using a prototype grid side dual current source inverter (CSI), are presented to validate the proposed technique.

This paper summarises an investigation into two modulation strategies that enable a hybrid cascaded multilevel converter to reduce on-state losses and extend the modulation index linear range independent of load power factor, and without capacitor voltage balancing problems. The first modulation strategy exploits unconventional triplen harmonics in combination with a hybrid modulation strategy to optimally reduce the number H-bridge cells required to minimize semiconductor losses, and improve capacitor voltage balancing of the H-bridge cells. The second modulation strategy is based on level-shifted multilevel carriers and exploits 3rd harmonic subtraction to modify the modulating signals in order to extend the regions around zero voltage crossing where cell capacitor voltage balancing can be achieved, with a minimum number of cells. It is shown that both modulation strategies overcome the traditional limitations of hybrid cascaded converter such as dependency of the capacitor voltage balancing on modulation index and load power factor. Also they extend the modulation linear range virtually up to 1.27 in real power applications. Simulation and experimental results at several operating points are used to substantiate the strategies presented in this paper.

Summary form only given. A prototype two-stage Linear Transformer Driver (LTD) system based on power MOSFETs has been designed and tested for single shot and multi-pulse burst mode operation. Each adder stage consists of two custom designed MOSFET driver boards with four parallel connected MOSFETs and two high voltage MKP capacitors per board. The two boards are connected on either side of the toroid core. The custom current source gate driver was designed to drive four parallel connected MOSFETs synchronously at switching speeds of less than 10ns. The induction core is made of Nanoperm and is 60mm wide and 20mm high. It is fully enclosed in an aluminium cavity. The overall width of the system is 200 mm. A compact LTD system is established with a high power density and ultra-fast switching. Experimental results demonstrate pulse widths of 100ns at a peak voltage of 1.5 kV and a peak current of 300 A with switching times of less than 12 ns.