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This paper proposes an accurate impedance model for line commutated converter (LCC) in the stationary frame. The commutation overlap process caused by the transformer leakage inductance complicates the modeling for LCC. Traditional impedance models are derived in positive sequence and negative sequence frame based on the simplified commutation overlap process, which degrades the modeling accuracy and limits the description of frequency coupling. This paper systematically analyzes the effects of the commutation overlap process on the impedance model, and the impedance model with the accurate commutation overlap process is established in the dq-frame. For clearly revealing the frequency coupling phenomenon of the LCC, the complex space vector is employed to extend the impedance model in the dq-frame to the complex αβ-frame. A closed-loop model on PSCAD/EMTDC is used to verify the proposed impedance model in the time-domain and the frequency-domain. The consistency between the simulation results and theoretical analysis effectively verifies the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

The degradation of the electrical contact in a gas insulated switchgear (GIS) is closely related to overheating at the contact. However, the disconnector contact is one of the hot contacts in GIS. Therefore, in this paper, the finite element method was used to solve the three-dimensional multiphysics coupling temperature rise field and flow field in the Single Phase in One Tank (SPIOT) type GIS disconnector under different operating conditions. From the perspective of temperature rise field and flow field, this paper analyzed the temperature rise characteristics under different working conditions and explored the feasibility of the direct application of air, CO2 and C4F7N/CO2 mixed gas to an electrical device. The disconnector temperature rise experiment platform was then built to verify the simulation. The results showed that the temperature rise field and the flow field distribution were similar in four gas environments. SF6 gas had the smallest temperature rise, followed by C4F7N/CO2 mixed gas, and the temperature rise of CO2 and air was relatively large. Therefore, from the perspective of the temperature rise field and flow field, it was feasible to directly apply C4F7N/CO2 mixed gas to an electrical device in order to meet insulation requirements. [ABSTRACT FROM AUTHOR]

This paper presents a memristive device model capable of accurately matching a wide range of characterization data collected from a tantalum oxide memristor. Memristor models commonly use a set of equations and fitting parameters to match the complex dynamic conductivity pattern observed in these devices. Along with the proposed model, a procedure is also described that can be used to optimize each fitting parameter in the model relative to an I–V curve. Therefore, model parameters are self-updated based on this procedure when a new cyclic I–V sweep is provided for model optimization. This model will automatically provide the best possible match to the characterization data without any additional optimization from the user. In this paper, multiple cyclic I–V characterizations are modeled from ten different tantalum oxide devices (on the same wafer). Additionally, studies were completed to demonstrate the amount of variation present between devices on a wafer, as well as the amount of variation present within a single device. Methods for modeling this variation are then proposed, resulting in an accurate and complete, automated, memristor modeling approach. [ABSTRACT FROM AUTHOR]

This paper presents an optimization method for selective harmonic elimination in a cascaded multilevel inverter using teaching–learning-based optimization (TLBO). The main objective in selective harmonic elimination (SHE) strategy is to eliminate low-order harmonics by solving nonlinear equations and reaching optimal solution, while the fundamental component is satisfied. In this paper, in one side, the influence of optimal dc sources is investigated to reach the SHE goal, and in another side, comparing optimization methods is considered. In this paper, the TLBO as a recently emerged nature-inspired algorithm is presented to provide better results for the SHE in comparison with genetic algorithm, artificial bee colony, imperialistic competitive algorithm, harmony search, ant colony optimization, particle swarm optimization, and differential evolution. For better comparison of those methods and influence of optimal dc sources, 5-, 9-, and 15-level inverters are chosen and MATLAB software is used for optimization. Simulation results show the superiority of TLBO, higher precision and probability of convergence than other mentioned algorithms. Finally, to validate the influence of optimal dc sources and the accuracy of TLBO results, the experimental setup is conducted for a 5-level cascaded H-bridge inverter with optimal dc sources. [ABSTRACT FROM AUTHOR]

This paper presents an FPGA-based Digital Real-Time Simulation (DRTS) environment for the analysis of Electromagnetic Transients (EMTs) of power systems that include multiple Power Electronic Converters (PECs). The main features of the proposed DRTS platform are that it i) employs two-value resistor switch model for PECs and thus avoids inaccuracies of Associate Discrete Circuit (ADC) model and ii) does not require separation of PECs by transmission lines (stub lines) and thus accurately represents PECs in close electrical proximity of each other. These features respectively result in a time-variant and large system admittance matrix which significantly increases the computation burden in each simulation time-step and can render it infeasible for real-time applications. To overcome this problem this paper introduces i) Switching-Network Partitioning (SNP) method which is tailored for PECs representation in FPGA and ii) Reformulated Modified Nodal Analysis (RMNA) method to enable computational parallelism between the solution of network and component models in FPGA. SNP enables solution-level partitioning of the PECs and the rest of the system. The developed DRTS platform enables sub-microsecond simulation time-step and provides a fixed hardware irrespective of the system configuration. Performance of the platform is evaluated for a study system and verified versus off-line simulation studies. [ABSTRACT FROM AUTHOR]

Partial shading condition drastically reduces the maximum power output of photovoltaic array. Partial shading occurs due to several factors, such as flying birds, trees, and passing clouds. Many ways can be mitigated partial shading problems in photovoltaic (PV) array. One among the way is reconfiguration techniques, namely reconfigure the location of PV modules in PV array based on irradiance levels in order to distribute shading effects and increasing maximum power. This paper proposed an optimal SuDoKu reconfiguration pattern for $9\times 9$ total-cross-tied (TCT) PV array to improve maximum power under partial shading conditions. In this approach, the physical location of PV modules in TCT array are rearranged based on optimal SuDoKu style without altering the electrical connections, so that the shading effects can distribute over the array. Further, the performance of proposed pattern investigated with existing SuDoKu pattern under different shading conditions by comparing the global maximum power point, mismatch losses, fill-factor, and efficiency using MATLAB-Simulink. Based on the results of this paper, it concluded that the proposed optimal SuDoKu reconfiguration arrangement is reducing the wiring arrangement and increasing the shading distribution over the array as compared to SuDoKu arrangement. [ABSTRACT FROM AUTHOR]

Solid state transformer (SST) integrated hybrid dc–ac microgrid (HMG) has wide operating capabilities in presence of dc–ac loads, renewable energy resources, and energy storage. This paper proposes control strategies for localized control of zonal hybrid microgrid, enabled by the SST and centralized energy storage devices (ESD) integrated using dual active bridge (DAB) converter. The control of DAB dc–dc converter is modified for zero circulating power flow (ZCPF) operation in both SST and ESD. Power management and coordination control used in this paper ensures the power supply reliability of the zonal HMG integrated through the SST. Microgrid system, along with its proposed controllers, provides a stabilized low-voltage dc and ac network ports, in both grid feeding and forming modes. The performance of the configured HMG system is evaluated under various power management scenarios using the MATLAB software platform. Further, the SST architecture, with its proposed controller, is tested on FPGA-based hardware platform. [ABSTRACT FROM AUTHOR]

In this paper, a new dc–dc high voltage gain converter with low-voltage stresses on switches and diodes is proposed. Even though, in the topology of the proposed converter there are not any coupled inductors and transformer utilized, the voltage conversion ratio of the proposed converter is considerable in comparison to its conventional types. Also, two switches of the proposed converter provide longer charge time for two inductors which make the proposed converter capable of providing high voltage gain without preselecting extremely large duty cycles. In addition, the number of power circuit components of the proposed structure are few and the voltage stresses on semiconductor elements are low. In this paper, theoretical analysis of the proposed converter for each operating mode is presented and the voltage gain, voltage and average current stresses of elements, maximum input current ripple, efficiency and equations of critical inductances are calculated. Moreover, to verify the capability of the proposed converter, it is comprehensively compared with other similar recently presented high voltage gain boost converters. Finally, an approximately 12 V/380 V and 520-W prototype of the proposed converter is implemented in laboratory to demonstrate its practical performance, then, the experimental results reconfirm each other and theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper introduces a novel modeling approach that allows to obtain fast simulations of pulsewidth-modulated dc–dc switched-mode power supplies (SMPS). The proposed methodology combines the use of precise switched models during transient evolutions and averaged models during steady-state or slowly varying conditions. In that way, the resulting mixed modeling approach enables to obtain the detailed switching behavior of SMPS in the context of long-term simulations. The commutation between models is automatically performed in runtime by an algorithm that detects the transient or slowly varying condition according to the evolution of some model variables. When the precise switched model is used, the mentioned algorithm also adjusts the averaged model parameters so that its results are accurate irrespective of the operating point. This paper also describes the implementation of the methodology in the Modelica language and reports simulation experiments showing that the results are as accurate as those obtained using precise switched models, but several times faster. [ABSTRACT FROM AUTHOR]

For Electro-Magnetic-Transient (EMT) simulations of power networks with switches, techniques such as linear interpolation and Critical Damping Adjustment (CDA) are widely used for improving numerical robustness. This paper analyzes the numerical stability of simulations with these techniques. Firstly, it is mathematically shown that the interpolation or CDA step is equivalent to the introduction of additional switching states. Subsequently, Common Quadratic Lyapunov Function (CQLF) theory is used to investigate the numerical stability of the whole simulation considering these new switching states. It is proved that the widely used strategies like linear interpolation and CDA always result a stable simulation if the original switched system is strictly passive in all switching states. Finally, it is shown that the developed approach can be used to determine the stability of other practical interpolation methods. Examples are provided to verify the proposed technique. [ABSTRACT FROM AUTHOR]

With increasing penetration of solar PV, some distribution feeders are experiencing highly variable net-load flows and even reverse flows. To optimize distribution systems under such conditions, the scheduling of mechanical devices, such as OLTCs and capacitor banks, needs to take into account forecasted solar PV and actual grid conditions. However, these legacy switching assets are operated on a daily or hourly timescale, due to the wear and tear associated with mechanical switching, which makes them unsuitable for real-time control. Therefore, there is a natural timescale-separation between these slower mechanical assets and the responsive nature of inverter-based resources. In this paper, we present a network admissible convex formulation for holistically scheduling controllable grid assets to position voltage optimally against solar PV. An optimal hourly schedule is presented that utilizes mechanical resources to position the predicted voltages close to nominal values, while minimizing the use of inverter-based resources (i.e., DERs), making them available for control at a faster time-scale (after the uncertainty reveals itself). A convex, inner approximation of the OPF problem is adapted to a mixed-integer linear program that minimizes voltage deviations from nominal (i.e., maximizes voltage margins). The resulting OPF solution respects all the network constraints and is, hence, robust against modeling simplifications.Simulation based analysis on IEEE distribution feeders validates the approach. [ABSTRACT FROM AUTHOR]

DC transformer is an essential equipment for formation of multi-voltage-level DC grid. This paper proposes a novel non-isolated Boost-type alternate arm DC transformer (Boost-AADCT) for medium- and high-voltage level DC grid application. The Boost-AADCT is comprised of three submodule-cascaded arms, two thyristor-cascaded director switches, and two buffer capacitors. Bidirectional power transmission is achieved by alternatively charging and discharging of the intermediate arm following the Boost principle, while the pulsating power component caused by intermittent transmission is actively smoothened by grid-side buffer subcircuits formed by the buffer capacitors and grid-side arms. The active power buffering method increases the tolerance range of voltage ripple of the buffer capacitor, and the required energy storage capacity is resultantly reduced. Circuit configuration, operation principle, and mathematical model are first introduced. Then, the control strategy is proposed, the main circuit parameters are designed, and bidirectional fault-blocking capability is analyzed. Comparison with other DC-DC converters shows that the Boost-AADCT significantly reduces the requirement of semiconductors and has relatively lower synthetic cost. At last, performance of the Boost-AADCT and the proposed control strategies are evaluated by simulation tests conducted in MATLAB/Simulink environment. [ABSTRACT FROM AUTHOR]

When a superconductor is exposed to an AC magnetic field whilst carrying a constant DC transport current, a DC electrical resistance can be observed, commonly referred to as “dynamic resistance”. This dissipative effect can play a critical role in many potential high-temperature superconducting (HTS) applications, especially for the AC-field-actuated HTS switch, which is the key component in the HTS transformer-rectifier flux pump (TRFP). The characteristics of the HTS switch determine the performance and reliability of TRFP. In this paper, we report a numerical study of a new HTS switch design made of series-connected YBCO stacks. This study aims to obtain insights into the characteristics of dynamic resistance and power loss, including their relationships with the amplitude and the frequency of the AC magnetic field. The energy conversion efficiency of the HTS switch is also investigated. This work will help design a high-performance AC-field-actuated HTS switch. [ABSTRACT FROM AUTHOR]

This paper tackles key industry needs in the scope of the AC Security-Constrained Optimal Power Flow (SCOPF) framework, specifically two major challenging requirements regarding generators’ post-contingency behavior: the (droop-based) frequency response and the voltage control mechanism (including PV/PQ switching). To this end, and to obtain a sufficiently accurate solution with a reasonable computational burden, we propose an approximation approach to SCOPF which extends significantly an existing algorithm with novel modelling elements: a continuous formulation to model generators’ post-contingency responses based on successive approximations, a technique to evaluate the viability of contingencies with respect to the base case set-points, and the complexity reduction of all post-contingency states through network compression and power flow piecewise linearization. All new features are validated both separately and in unison, to monitor the improvement of the solution time and the potential degradation of the solution's quality. The proposed approach is successfully applied to three power system network models, the largest of which consists of 2,000 buses and more than 3,000 contingencies. Finally, the trade-off between the limitations in terms of solution quality and the benefits in terms of computational effort are assessed for all proposed approximations. [ABSTRACT FROM AUTHOR]

In this paper, the pulsewidth modulation switch method was used to investigate the effect of the transformer leakage inductance on the small-signal model in isolated full-bridge converter. A galvanic isolated hard-switching full-bridge converter that operates in constant-current mode is analyzed, confirming that leakage inductance significantly affects the small-signal model, and the influence of leakage inductance can be equivalent to a resistance in series with the converter's output LC filter just as that in phase-shifted full-bridge converter. However, the same leakage inductance in these both converters will lead to different equivalent resistance due to different operating principles. Results of the modified model, simulations, and the experiments are compared to verify the correctness of the model. Moreover, this paper also shows that the Norton equivalent circuit of the charger operates in constant current mode, which can be used to estimate the dynamic behavior of the system. [ABSTRACT FROM AUTHOR]

The availability of reliable analytical models is essential to the optimal design of energy harvesters and for the prediction of the system behavior. In this paper, we consider a low-input nonlinear system based on a flexible buckled beam forced in a bistable configuration. The harvester has been demonstrated to generate power in the excess of $400~\mu \text{W}$ with the optimal resistive load of 15 $\text{k}\Omega $ and a monotonic input with root-mean-square accelerations of 13.35 m/s2. The power generated is suitable for powering low-power measurement systems or sensor nodes. This paper focuses on a methodology for the modeling of the mechanical dynamical behavior of the device subject to a periodic impulsive signal. A measurement protocol for the evaluation of system’s hidden quantities, the beam’s restoring force, and the beam’s displacement between its stable states is introduced. A second-order behavioral model with a nonlinear term representing the beam’s restoring force has been used. In order to model the nonlinearity, two different potential energy functions have been compared by fitting the models to the experimental data with different constrains, through a performance index evaluating the fitting error. [ABSTRACT FROM AUTHOR]

Ferroelectric and negative-capacitance field-effect transistors (FeFETs and NCFETs) have recently garnered great attention as devices for applications in memory and low-power logic, respectively. As these technologies are pursued, it is critical to have a variety of measurement approaches, including methods familiar to the electron-device and microwave communities that can aid in fully understanding the behavior of ferroelectrics in FeFETs and NCFETs. In this paper, we propose and show the viability of using frequency-domain electrical measurement techniques employing the well-known microwave S-parameters, and their large-signal generalization and X-parameters. Our methods provide the means to trace the intrinsic polarization versus electric-field curve of the ferroelectric, i.e., with the parasitics de-embedded, thereby showing the innate ferroelectric response, which cannot be done using conventional techniques. These methods also enable extraction of all the parameters of the Landau–Khalatnikov equation, which is commonly used to model ferroelectric behavior in FeFETs and NCFETs. This paper hence takes a useful step toward methods familiar to the electron-device community that can help to better understand and optimize FeFET and NCFET technologies. [ABSTRACT FROM AUTHOR]

In the paper by Patra et al., a single-inductor multiple-output switcher was presented to produce buck, boost, and inverted outputs simultaneously. Unfortunately, this study showed some unexpected mistakes, especially in state-space equations and in the calculation of output voltages. The objective of this note was to provide correct analysis and rectify the errors in this paper. Some tables and equations have been modified that were present in the initial draft of this paper. The obtained parameters in this work could be an effective supplement and extension for the original work in the paper by Patra et al. [ABSTRACT FROM AUTHOR]

The paper deals with some new results on the averaging theory approach for the analysis of feedback controlled pulsewidth modulation power electronic converters. It develops some considerations regarding the averaging approximation of time-variant differential systems proving an analytical relationship between the accuracy with which the solution of the averaged model converges to the solution of the original time-variant model (i.e., the switched model) and the switching frequency of the converters. This relation is valid both for stable and unstable systems. Moreover, this paper confirms, as corollary, that under suitable conditions (verified during the standard operations of the power electronic converters) the averaged model uniformly converges to the switched model. [ABSTRACT FROM AUTHOR]

This paper presents a study of the losses in the integrated buck–flyback converter (IBFC) used as high-power-factor LED driver. The aim of the study is to investigate the possibilities of increasing the efficiency of the IBFC converter. The procedure of the improvement is done by obtaining the equations of the current through each component in terms of converter parameters. The current is found in an average value or rms value, depending on the type of the parasitic component, whether it is modeled by a parasitic forward voltage source or by a parasitic resistance, respectively. Using these equations and the parasitic model, the losses of each element of the converter are estimated. This paper proposes a technique to increase the efficiency of the IBFC by redesigning the converter parameters. Furthermore, this paper presents a case of study with a step-by-step efficiency enhancement process of an existing driver. The driver is operating under universal input conditions, and 38 V output, supplying an LED luminary of 26.5 W. The new design shows an improvement of the efficiency from 82% in the old design to 89% in the proposed one. Moreover, the new design shows an improvement in the power factor and the THD and a 50% reduction in the output current ripple. Furthermore, a reduction in the number of components has been achieved, as it is found by the analysis that by adjusting the converter parameters, one diode can be removed. Finally, the presented methodology is explained in detail so that it can easily be applied to other dc–dc converters. [ABSTRACT FROM AUTHOR]

This paper presents nonlinear optimization-based position and speed estimation scheme for IPMSM drives with arbitrary signal injection generated by inherent switching ripples associated with finite control set model predictive control (FCSMPC). The existing standard sensorless techniques are not suitable for FCSMPC which applies voltage vectors directly to an electrical machine without a modulator. The proposed method optimizes the nonlinear cost function derived from the standard IPMSM model with respect to position and speed at every sampling interval. This method can be applied to any type of signal injection and, hence, an ideal candidate for sensorless FCSMPC. In this method, the signal injection is needed only to generate persistent excitation to maintain the observability at low speeds. A strong persistent excitation is always present with FCSMPC except at standstill where the control applies null vector when the reference currents are zero. This situation is overcome in this paper by introducing a small negative $d$ -axis current at standstill. Thus, the proposed method can estimate the position and speed over a wide speed range starting from standstill to the rated speed without a changeover or additional signal injection. This paper also presents detailed convergence analysis and proposes a compensator for standstill operation that prevents converging to saddle and symmetrical solutions, and therefore, also eliminates the well-known ambiguity of $\pi$ rad in position estimation. The performance of the proposed sensorless scheme is experimentally verified for a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents two novel measurement methods to characterize silicon carbide (SiC) MOSFET devices. The resulting data are utilized to significantly improve the extraction of a custom device model that can now accurately reproduce device switching behavior. First, we consider the $I_{\text{d}}- V_{\text{ds}}$ output characteristics of power devices such as SiC transistors. These are typically measured using traditional curve tracers, but the characterization of the high-voltage and high-current (HVHC) region is very challenging because of device power compliance and self-heating. In this paper, we introduce a measurement technique that overcomes self-heating and derives the HVHC region from switching waveforms. The switching transient characteristics of devices are used to determine drain current $(I_{\text{d}})$ as a function of drain–source voltage $(V_{\text{ds}})$ in the HVHC range. Second, we consider another challenging characterization area: measurement of nonlinear capacitances when device is turned on. These capacitance characteristics of on-state devices are important for correcting disagreements between simulations and measurements in turn-off switching transient waveforms and cannot be measured using a conventional capacitance-voltage meter. We introduce S-parameter measurements as an effective method to obtain the capacitance characteristics of both off-state devices and on-state devices. These novel measurement techniques have been applied to the modeling of a SiC device. The extracted device model, a modified version of the popular Angelov−GaN high-electron-mobility transistor model, shows significant improvement in terms of the accuracy of switching waveforms of devices over a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

With the increasing penetration of renewable energies in modern power grids, large amounts of voltage source converters (VSCs) have been installed, resulting in many new transient issues. Electromagnetic transient (EMT) simulation plays an essential role in investigating and solving the issues. However, simulation efficiency plunges when object grids contain multiple VSCs, because each switching event incurs modification or re-decomposition of the network matrix in traditional EMT programs, which is very time-consuming. Thus, this paper proposes a VSC model represented by pulse voltage-current source pairs. Accordingly, a unidirectional loosely-coupled solving algorithm is designed. Synthetically, the authors propose a novel EMT simulation approach adaptive to systems with multiple VSCs. The proposed approach keeps the computational network invariable while sufficiently considers detailed switching events, thereby significantly improving the simulation efficiency of the EMTP program without precision loss. [ABSTRACT FROM AUTHOR]

The hard switching operation of the insulated gate bipolar transistor (IGBT)-based multilevel converters (MLCs) in the transformer less direct integration of renewable power plants produces a considerable amount of switching and conduction power loss. This eventually causes higher junction temperature and lower thermal stability. The symmetrically designed MLC using third harmonic sixty-degree bus-clamped pulse width modulation (BCPWM) technique demonstrates reduced switching losses and better harmonic spectra. However, the development of analytical power loss model is a complex and challenging issue due to the discontinuous switching mode of IGBTs for the BCPWM in MLC. In this regard, an analytical model for calculating the average and the rms currents for the hard switching operation of IGBTs and antiparallel diodes (APDs) with BCPWM is proposed. Furthermore, to calculate the device turn-on and turn-off losses, a discrete form of equation is presented to evaluate the transition times of switching more precisely. The numerical power loss values of IGBTs and APDs found from the derived analytical equations for MLC are compared with the simulation and experimental results. The numerical results agree well with the simulated and the experimental outcomes, which validate the proposed analytical loss model. Moreover, an advanced three dimensional thermal impedance model with chip-wise interdependent multilayer thermal coupling effect is also considered in this paper to realize the critical thermal loading condition of the switching devices. [ABSTRACT FROM AUTHOR]

This paper presents voltage regulation and current tracking control strategies for three phase two-level grid-connected power converters. By using power-invariant Park’s transformation, an averaged mathematical model of power converters is obtained in dq synchronous reference frame. Then a novel control strategy using adaptive control and ${H}_{\infty }$ technique is proposed to regulate the dc-link output voltage as well as track a desired current reference for three-phase power rectifiers. More specifically, an efficient adaptive controller is established in the external loop for regulating dc-link output voltage in the presence of external disturbances. A set of ${H}_{\infty }$ controllers are designed in the internal loop to force the input currents track their desired values. Finally, simulation results obtained from the proposed control method are presented, analyzed, and compared with that of sliding mode control, and the superiority of the proposed control laws is verified. [ABSTRACT FROM AUTHOR]

Supply chain systems are network systems with several subchains each of which consists of facilities and distribution entities (suppliers, manufacturers, distributors, and retailers), and thus such systems can be viewed as multiagent systems. Consensus or coordination of multiple subchains is crucial for a stable market supply, especially in the case of some subchains suffering from production interruption, or losing connection with others, which become isolated subchains in some time period due to irresistible reasons. Once some unspecified isolated subchains appear, the topology structure of the system will be changed, and thus the multiagent-based supply chain system can be modeled as a switched system. This paper aims to investigate the problem of ${H_\infty }$ consensus for multiagent-based supply chain systems under switching topology and uncertain demands. To achieve the consensus of the system, switching controller is designed in which both production rate and distributed consensus protocol are considered. Sufficient conditions are given such that the whole system reaches consensus and desirable attenuation of bullwhip effect with an average dwell time approach, which allows some subchains to be isolated in some time periods. Finally, a simulation example is presented to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This article proposes a novel high-performance predictive control with long prediction horizons to improve the control performance of the multilevel inverters. The finite control set model predictive control (FCS-MPC) has obtained a lot of attention for power converters due to its advantages of high dynamic performance, multi objective capability, no need for PI regulators and PWM modulators. However, the MPC method requires a high number of computations especially for higher-level power converter topologies due to the existence of a huge amount of switching combinations and redundancies. Real-time searching for the optimal switching state among a large candidate pool at a high sampling rate is sometimes impossible with the standard commercial processors. This limitation also prevents real-time implementation of an MPC for multilevel converters with step prediction more than one. To solve the aforementioned issues, this paper presents a novel high-performance FCS-MPC scheme. The proposed FCS-MPC is reformulated mathematically MPC approach to an l 2 norm optimization problem, which can be solved on-line through matrix theory. Compared with the existing MPC optimization algorithms, the proposed MPC formulation has the advantage of a substantial reduction in computational burden, no need for the weighting factors or cost functions, and thus can operate at long horizon prediction length. The proposed method is verified experimentally on a seven-level CHB inverter prototype with a three-step prediction length to demonstrate the ability and performance of the proposed method for multilevel inverters. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage nonisolated switched capacitor ac–dc converter for power-factor correction (PFC). This converter features reduced passive components, single switch, transformerless high voltage gain, and improves the power factor, reduces total harmonic distortion, and voltage stress across the switch. The peak current mode with a dynamic resonant perturbation scheme compensates the subharmonics that exist at zero crossing of the source current is implemented for PFC. In this paper, the principle of operation, large signal modeling of the circuit, and control method for the proposed PFC converter are provided. [ABSTRACT FROM PUBLISHER]

The neutral-point voltage-balancing control is a critical issue of a neutral-point-clamped converter. The conventional control strategy is to inject the specific zero-sequence voltage to regulate the redundant vector, but it is unacceptable to the three-phase four-wire system. This paper provides a neutral-point voltage-balancing control by the dipolar modulation, and the control freedom of the zero-sequence voltage is flexible. Therefore, the proposed method is suitable for both three-phase three-wire and three-phase four-wire systems. Besides, the proposed method improves the control dynamic in a reactive power system. The proposed neutral-point voltage-balancing control is verified by the mathematical analysis and experimental results. The control dynamic, power loss estimation, and the output current performance are analyzed in this paper. [ABSTRACT FROM PUBLISHER]

The three phases of brushless dc motor (BLDCM) are involved in energy conversion during the commutation interval. A novel commutation analysis method of the BLDCM based on coordinate transformation theory is proposed in this paper, though this coordinate transformation theory is popular in the control of three-phase sinusoidal motors, such as induction motors and permanent magnet synchronous motors. The method is intuitive and easy to understand compared with the method based on circuit solving. Combined with the voltage vector diagram of the inverter, commutation control to reduce commutation torque ripple under low speed (LS_RCTR) and high speed (HS_RCTR) is deduced. However, under a heavy load and high-speed condition, long commutation time may result in commutation failure if these commutation controls to RCTR is adopted. To avoid that, commutation time must be controlled. Then, commutation control to reduce commutation time under low-speed (LS_RCT) and high-speed (two cases, named HS_RCT1 and HS_RCT2) are proposed. The improved control of BLDCM presented in this paper can coordinate commutation torque ripple and commutation time in full speed range. Finally, the feasibility and effectiveness of these methods are verified by experiment. [ABSTRACT FROM PUBLISHER]

In this paper, new half-bridge and full-bridge topologies for a switched-boost inverter are proposed. These topologies have a high boost factor in comparison with conventional types. In addition, the proposed topologies have continuous input current and can generate zero-voltage level in output. In this paper, the operation of the proposed inverters in different operating modes is analyzed. Then, the values of inductors and capacitors are designed. Moreover, the used switching pattern and its logical diagram are introduced. A comprehensive comparison between the proposed and conventional topologies in terms of the boost factor, the number of elements, and the efficiency shows the good features of the proposed inverters. Finally, to verify correct operation of the proposed topologies and derived equations, simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

The nine-switch converter is a multiport converter having two three-phase terminals and a dc-link, just like a 12-switch back-to-back (BTB) converter, but with 25% reduction of active switch count. However, the reduction from 12-switch to 9-switch may not always be an efficient choice considering losses in the switches. Only the load–source combination for the ac–ac common frequency mode and the source–source combination for the ac–dc different frequency (ac–dc DF) mode have been reported, so far, to yield relatively lower loss for the nine-switch converter. This paper shows that the nine-switch converter can have relatively lower loss even with a load–source combination, instead of only source–source combination in its ac–dc DF mode—when the upper terminal is connected to a dc load and the lower terminal is connected to an ac source. Mathematical proof is presented with derivation of the particular operating parameters for which the nine-switch converter will have comparatively lower losses. The analysis is validated with simulation and experimental results of a 1-kW system. Finally, the benchmark of the application criteria of the nine-switch converter for having lower conduction loss than the BTB converter is updated in this paper. [ABSTRACT FROM AUTHOR]

Fast and detailed calculations of harmonics, generated by three-phase uncontrolled rectifiers with finite dc smoothing, can be performed by using detailed analytical procedures (DAPs). Several DAPs are developed for continuous- and discontinuous-conduction modes (CCM and DCM) when balanced operation of the system is assumed. The authors of this paper have recently proposed a new DAP (model 1a) in which nonideal conditions, such as unbalances and even harmonic voltages on the ac side, are taken into account. However, only CCM is assumed in model 1a. The main objective of this paper is to overcome this limitation of model 1a so that a new DAP (model 1b) for DCM is presented, which is capable of considering unbalanced operation. Moreover, the boundary of the DCM is also estimated for model 1b under nonideal conditions. [ABSTRACT FROM PUBLISHER]

This paper proposes a current sensorless control strategy for the dual active bridge (DAB) converter with nonlinear disturbance observer (NDO)-based load current feedforward. The proposed method can regulate both the dc-bus voltage and the current of the DAB converter without current sensors. Several performance indexes are established for the parameter design and a detailed design method is presented in this paper. When a single-phase H-bridge inverter is connected, the double-frequency oscillation from the feedback path is suppressed by proper parameter design, while the transient response of dc-bus voltage can be further improved by the NDO-based load current feedforward with a notch filter in the feedforward path. The performance of the proposed control method and the effectiveness of the parameter design are verified in a prototype by experimental results. [ABSTRACT FROM PUBLISHER]

Objective: Tumorigenesis is due to uncontrolled cell division arising from mutations and alterations in the proliferative controls of the cell population. The fight against tumor growth and development has often relied on combination therapy that has been acclaimed as one of the main standards of care in cancer therapeutics and prevention of drug-related resistances. The toxicity of the combinatorial drugs raises a significant concern whenever patients take two or more drugs concurrently at the maximum tolerated dose. A promising solution in tumor treatment involves the administration of the drugs in an alternating or sequential fashion rather than a simultaneous manner. In this paper, we investigate how feasible such an approach is from a mathematical perspective and propose a switched hybrid control systems framework. Methods: We explore the response of tumor cells dynamics to sequential drugs administration with the aid of a time-dependent switching strategy. A transit compartmentalized model is employed to describe the tumor cells progression to death. Results: The design of the time-based drug switching logic ensures the proliferating tumor cells are repressed. Conclusions: Simulation results are provided using the tumor growth dynamics with sequential drugs intake to demonstrate the effectiveness of the proposed method in reducing the tumor size. Significance: This paper is the first attempt to provide a switched hybrid control systems framework on sequential drug administration to biomedical researchers and clinicians. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to study the dynamics of a permanent magnet direct current (PMDC) brushed motor while two crucial space-domain effects, namely, slotting effect and commutation phenomenon are taken into account. Semi-analytical dynamic time-domain PMDC brushed motor model inclusive of these space-domain effects is used to analyze and investigate the dynamics. Pulse width modulation operated discontinuous current PMDC brushed motor drive with steady duty cycle is employed to acquire the bifurcation patterns. The chaotic nature due to slotting effect and commutation is identified from the bifurcation patterns and reported. It also has to be admired that such nonlinear dynamical behavior with the same set of parameters at similar operating condition has not been observed when a conventional PMDC brushed motor dynamic model is considered. These space-domain effects, namely, slotting effect and commutation also have a prominent impact to make some time-domain states of a PMDC brushed motor drive chaotic. The role of slotting effect and commutation phenomenon to analyze the chaos over time-domain state variables of the PMDC brushed motor drive is investigated and validated experimentally in this paper. [ABSTRACT FROM PUBLISHER]

Two key problems in meshed high-voltage direct current (HVDC) transmission grids are managing line power flows and protection against dc faults. Current flow controllers (CFCs) will be required to balance cable currents in meshed dc grids, in order to prevent individual line power capacity limits restricting overall power flow in the grid. Direct current circuit breakers (DCCBs) will be also required to protect HVDC grids from dc faults. This paper demonstrates that the current flow controller functionality can be added into a hybrid CB's design. This paper proposes integrating an interline CFC into the load commutation switch (LCS) of a hybrid DCCB. The integrated design LCS/CFC is analyzed and a state-space model is derived. The control of the CFC is designed and the performance of the LCS/CFC during normal operation is verified by means of MATLAB Simulink and PSCAD simulations. A comparison of the integrated LCS/CFC and the separate design is given. The case studies show a reduction in total power losses, and improved protection operation times can be achieved. [ABSTRACT FROM PUBLISHER]

The performance of modular multilevel converters (MMCs) in medium-voltage applications, where the number of required submodules is not high, can be improved utilizing low switching frequency modulations such as (2N+1) selective harmonic elimination-pulse width modulation (SHE-PWM), which provides tight control of lower order harmonics and low switching losses. This paper proposes a calculation method, which is based on a novel formulation, to solve the SHE-PWM problem. In particular, MMCs with (2N+1) phase output voltage levels are considered, obtaining a (2N+1) SHE-PWM waveform. This method utilizes a unique system of equations that is valid for any possible waveform. Therefore, it is able to calculate simultaneously, without predefined waveforms, both the switching patterns and the associated firing angles that solve the (2N+1) SHE-PWM problem. Consequently, the search process is simplified and optimized. Furthermore, this paper also proposes a circulating current control technique, which can be applied along with (2N+1) SHE-PWM without disturbing the phase output voltage. Simulation results and experimental tests obtained with a single-phase laboratory prototype prove the validity of the novel (2N+1) SHE-PWM implementation method and the proposed circulating current control technique. [ABSTRACT FROM PUBLISHER]

The reduced chip size and unipolar current conduction mechanism make silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) suitable for high-frequency power electronics applications. Modeling the switching process of the SiC power MOSFET with parasitic components is important for achieving higher efficiency and power density system design. Therefore, this paper proposes a new concise yet accurate switching loss model for SiC power MOSFETs. Addressing the limitations in experimental measurements, numerical simulations are conducted to validate the proposed model taking the output capacitance Coss discharge and charge into consideration. The role of the parasitic components in the second-order model is discussed in depth for switching losses. Furthermore, this paper also provides guidelines in designing the gate driver for ultrafast SiC power MOSFETs. [ABSTRACT FROM PUBLISHER]

For the purpose of improving the performances of T-type neutral point clamped (T-NPC) photovoltaic (PV) grid-connected inverter under large grid, a passivity-based decoupling control scheme is proposed in this paper. First, the Euler–Lagrange (EL) mathematical model of a T-NPC PV grid-connected inverter with an LC filter is built based on the power circuit and operating principles. Second, with this EL mathematical model and passivity of the inverter, the passivity-based controller is designed by the damping injecting method. Third, by adopting a proportional integral regulator to directly control direct current (dc) voltage, together with passivity-based indirect control, better performances of the dc voltage control can be further obtained. With the proposed passivity-based controller, the PV grid-connected inverter can achieve both dynamic current decoupling under the synchronous rotating dq coordinate and dc side voltage dynamic decoupling, which can improve the quality of the current connected into the power grid. The passivity-based PV grid-connected inverter is with strong robustness against parameters perturbations of resistors and attenuating the influence of delay in the inverter. Moreover, the passivity-based decoupling control scheme proposed in this paper for the T-NPC PV grid-connected inverter has a simple structure, and is easily debugged and realized in engineering. Experimental results under 10-kW prototype show that the proposed control scheme is effective. [ABSTRACT FROM PUBLISHER]