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Capacitors usually determine the overall lifetime of power converters since they are mainly responsible for break-downs. Their failure results from the deterioration of their dielectric, the production of gases, and, eventually, their explosion. This process leads to an increase in the capacitor equivalent series resistance (ESR) and a decrease in its capacitance value for both electrolytic and metalized polypropylene film (MPPF) capacitors. In this paper, a novel noninvasive technique for capacitor diagnostic in Boost converters is presented. It can easily be applied online and even in real time, and it is suitable for the operation in both continuous current mode (CCM) and discontinuous current mode (DCM). The technique is based on the double estimations of the ESR and the capacitance, improving the diagnostic reliability. This way, predictive maintenance is provided, and it is possible to alarm for capacitor replacement, avoiding downtime. As the method is intended for railway high-power applications, it has been conceived neither to add any additional hardware in the power stage nor to even slightly modify it. To demonstrate and validate the effectiveness and accuracy of the proposed technique, several simulations and experimental results are discussed in a small prototype. In this prototype, the software for real-time estimation is programmed in a low-cost digital signal processor (DSP). [ABSTRACT FROM AUTHOR]

This paper shows that multirate processing in a cascaded discrete-time ΔΣ modulator allows to reduce the power consumption by up to 35%. Multirate processing is possible in a discrete-time ΔΣ modulator by its adaptibility with the sampling frequency. The power reduction can be achieved by relaxing the sampling speed of the first stage and increasing it appropriately in the second stage. Furthermore, a cascaded ΔΣ modulator enables the power efficient implementation of multiple communication standards. The advantages of multirate cascaded ΔΣ modulators are demonstrated by comparing the performance of single-rate and multirate implementations using behavioral-level and circuit-level simulations. This analysis has been further validated with the design of a multirate cascaded triple-mode discrete-time ΔΣ modulator. A 2-1 multirate low-pass cascade, with a sampling frequency of 80 MHz in the first stage and 320 MHz in the second stage, meets the requirements for UMTS. The first stage alone is suitable for digitizing Bluetooth and GSM with a sampling frequency of 90 and 50 MHz respectively. This multimode ΔΣ modulator is implemented in a 1.2V90 nmCMOStechnology with a core area of 0.076mm². Measurement results show a dynamic range of 66/77/85 dB for UMTS/ Bluetooth/GSM with a power consumption of 6.8/3.7/3.4 mW. This results in an energy per conversion step of 1.2/0.74/2.86 pJ. [ABSTRACT FROM AUTHOR]

This paper presents a real-time thermal model with calculated parameters based on the geometry of the different components of a permanent-magnet synchronous motor. The model in state-space format has been discretized and a model-order reduction has been applied to minimize the complexity. The model has been implemented in a DSP and predicts the temperature of the different parts of the motor accurately in all operating conditions, i.e., steady-state, transient, and stall torque. The results have been compared with real measurements using temperature transducers showing very good performance of the proposed thermal model. [ABSTRACT FROM AUTHOR]

Tightly regulated closed-loop converters are problematic when used as a load since they tend to draw constant power and exhibit negative incremental resistance. This negative resistance causes stability problems for the feeder system, whether it is an input filter or another converter. In multiconverter power electronic systems, which exist in different land, sea, air, and space vehicles, including electric, hybrid, plug-in hybrid, and fuel-cell vehicles, there are many converters loaded by other converters. Therefore, the destabilizing effect of the load converters, which are called constant-power loads, is a major issue. In this paper, a novel nonlinear feedback, which is called loop cancellation, is introduced. This technique is used to cancel the destabilizing effect of the constant-power loads. Theoretically, any amount of constant-power load can be compensated by this technique, and it can identically be implemented on different types of converters. The effectiveness of the proposed technique has been verified by PSpice simulations and experimental results. [ABSTRACT FROM AUTHOR]

A multilevel inverter topology feeding a three-phase open-end winding machine is analyzed in this paper. The scheme is based on the use of two insulated dc supplies, each one feeding a standard two-level three-phase inverter. The three-phase six-wire winding is connected across the output terminals of the two inverters. A new modulation technique that is able to regulate the sharing of the output power between the two dc sources in each switching cycle is presented. The performance of the whole system has been verified by both numerical and experimental tests. [ABSTRACT FROM AUTHOR]

Recently, a new multilevel inverter—Hexagram inverter has been reported for medium-voltage (MV) variable-speed drives (VSDs). This paper will propose a Hexagram rectifier as the active front end for the Hexagram-based MV VSD systems. The control of the Hexagram rectifier is based on one-cycle control-an excellent control scheme for switching power converters. With the proposed control scheme, unity power factor at the source side can be achieved, the six modules will equally share the output power, and the voltage stress of the converter will be reduced six times. A 1-MW simulation model and a 1.2-kW experimental prototype have been built to demonstrate the proposed Hexagram rectifier and its control scheme. [ABSTRACT FROM AUTHOR]

DC-DC converters have been reported as exhibiting a wide range of bifurcations and chaos under certain conditions. This paper analyzes the bifurcations in current-controlled Luo topology operating in continuous conduction mode using continuous-time model. The stability of the system is analyzed by studying the locus of the complex eigenvalues, and the characteristic multipliers locate the onset of Hopf bifurcation. The 1-periodic orbit loses its stability via Hopf bifurcation, and the resulting attractor is a quasi-periodic orbit. This later bifurcates to chaos via border collision bifurcation. A computer simulation using MATLAB/SIMULINK confirms the predicted bifurcations. It has also been inferred from the experimental results that the margin of system stability decreases as the load decreases. [ABSTRACT FROM AUTHOR]

This paper presents a new control scheme for an active front-end rectifier using model-based predictive control. The control strategy minimizes a cost function, which represents the desired behavior of the converter. Future values of currents and power are predicted using a discrete-time model. The active and reactive powers are directly controlled by selecting the optimal switching state. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. The rectifier operates with sinusoidal input currents and unity power factor. Simulation and experimental results are presented to verify the performance of the proposed power control scheme. [ABSTRACT FROM AUTHOR]

Passive current sharing in multiphase converters, where resistive losses are not dominant, is a quite complex goal. In this paper, an averaged model of an active clamp buck converter was obtained. It has been checked that this topology presents high output impedance. This property is used like a lossless passive equalization. The principle of operation, theoretical analysis, simulation, and experimental results are presented, taken from a three-stage laboratory prototype. [ABSTRACT FROM AUTHOR]

In ac-supplied traction systems (e.g., 15 kV, 16.7 Hz), the energy supplied by a conventional transformer results in large volume, high weight, and relatively low efficiency. In this paper, an ac-dc multilevel converter is presented that allows the use of a medium-frequency transformer in the input section of a traction drive. The proposed solution seems particularly well adapted to the different requirements (volume, weight, EMC, losses) of the electric traction domain. The system is studied from a theoretical point of view, starting from the basic module up to the entire converter structure. Simulation results and reduced-scale (10-kVA four-stage converter) experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper presents a new control strategy for islanded (autonomous) operation of an electronically coupled distributed generation (DG) unit and its local load. The DG unit utilizes a voltage-sourced converter (VSC) as the coupling medium. In a grid-connected mode, based on the conventional dq-current control strategy, the VSC controls real- and reactive-power components of the DG unit. Subsequent to an islanding detection and confirmation, the dq-current controller is disabled and the proposed controller is activated. The proposed controller utilizes 1) an internal oscillator for frequency control and 2) a voltage feedback signal to regulate the island voltage. Despite uncertainty of load parameters, the proposed controller guarantees robust stability and prespecified performance criteria (e.g., fast transient response and zero steady-state error). The performance of the proposed controller, based on time-domain simulation studies in the PSCAD/EMTDC software environment, is also presented. [ABSTRACT FROM AUTHOR]

There is a growing need for accurate and time efficient modelling of electrical distribution networks within the aerospace industry, for which power electronic converters are an integral part. Simplifying converter models is necessary to improve simulation execution times, however many existing techniques do not necessarily give accurate results for all types of system level studies. This paper describes an alternative modelling approach to these, which provides accurate results and reduced simulation times for studies of electrical fault analyses. [ABSTRACT FROM AUTHOR]

Three-phase four-leg voltage-source converters by virtue of the fourth leg connected to the neutral points of the wye-connected loads effectively handle the zero-sequence currents and voltages occasioned by connected load impedance imbalances and/or nonlinearity of loads. This paper develops a generalized carrier-based pulsewidth-modulation scheme for this converter which with a natural reference-frame control scheme that directly controls the actual load currents ensures current regulation irrespectively of the nature of the load. The proposed modulation and control schemes are effectively validated by computer simulation and experimental results for the converter operation in the linear and overmodulation regions. [ABSTRACT FROM AUTHOR]

Three-level neutral point clamped (NPC) voltage source converters have recently emerged as important alternatives to conventional two-level converter topologies in high-power medium-voltage energy conversion applications, particularly in high performance ac motor drive systems. An all-inclusive modulation strategy for NPC converters should have the capability of extending the operating range of the converter into the overmodulation region with a smooth and linear transition characteristic. An overmodulation switching strategy based on the space vector classification technique for three-level NPC converters is introduced in this paper. The proposed overmodulation modes, make possible continuous control of the output voltage up to the maximum possible with a smooth linear transition characteristic, and minimum distortions. A theoretical basis for the vector classification space vector modulation technique in the overmodulation region is presented, and the proposed overmodulation schemes are validated by analysis, simulation and experimentation on a 2-KVA three-level NPC converter laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper presents a carrier-based modulation method for a matrix converter. By using the offset voltage and changing the slope of carrier, it is possible to synthesize the sinusoidal input currents with the unity power factor and desired output voltages. The proposed method is equivalent to the so called space vector pulsewidth modulation method. The proposed method uses a new point of view to understand the matrix converter modulation method such as the voltage source inverter (VSI) modulation method. Using the proposed method, this paper presents the two-phase/three-phase modulation method and dynamic/steady-state over-modulation method for the matrix converter. These methods are well developed in the study of a VSI. By the proposed steady-state overmodulation method, it is possible to synthesize the fundamental component of output voltage to be equal to that of input voltage at the cost of some distortion of input current. The feasibility of the proposed modulation method has been verified by a computer simulation and experimental results. These results show that the proposed carrier-based modulation method can be implemented easily without any tables. It can be used for the application where a higher voltage transfer ratio is essential. [ABSTRACT FROM AUTHOR]

In this paper, a new controller for single-phase PWM converter without the ac voltage sensor is described. The proposed controller requires only the dc voltage sensor and the ac current sensor to compensate the power factor and harmonics. Detail simulation model including power circuit and controller was developed to verify the operation of proposed controller. The ape plication feasibility of the proposed controller was verified through experimental works with a prototype. The proposed controller has a simple structure in the point of hardware implementation, and shows excellent performance in normal operation as well as in sudden load change. [ABSTRACT FROM AUTHOR]

This paper presents a quadratic boost converter using a single quasi-resonant network to reach soft commutation. A resonant inductor, a resonant capacitor, and an auxiliary switch form the resonant network and the main switch operates in a zero-current-switching way. A complete analysis of this converter is presented. According to the simulation and experimental results, this quadratic boost converter provides a larger conversion ratio than that provided by the conventional boost converter (for a given duty ratio D), and presents optimum performance, which operates with soft-switch commutation using a single resonant network. [ABSTRACT FROM AUTHOR]

High-power dc–dc converter is the essential component for connecting the renewable energy sources to medium-voltage dc (MVDC) grids. In this paper, a novel zero-voltage zero-current switching converter with two full-bridge cells sharing a bridge leg and connecting the secondary windings of two transformers in series is proposed for MVDC applications. One big feature of the proposed converter is that the required inductance used for energy transmission is reduced remarkably and even can be embedded in the transformer in some cases. Special but simple control strategy adopted by the converter makes it work in discontinuous current mode, which can realize zero-current switching for the main switches and rectifier diodes in the whole load range. Meanwhile, the auxiliary switches with small current rating can realize zero-voltage switching naturally. Hence, the switching loss is reduced, which is very important for high-power applications. The effects of the turns ratio of auxiliary transformer on the total loss and needed inductance are comprehensively analyzed and proved. With a detailed parameters design procedure, a simulation model is established in the software PLECS and the operation principle of the converter is verified. A 120 V–1200 V/1 kW prototype was built to validate the operation principle of the proposed converter. [ABSTRACT FROM AUTHOR]

The stacked polyphase bridges (SPB) converter consists of several submodules that all are connected in series to a voltage source. The total dc-link voltage should split in a balanced way among the submodules. This does not always occur inherently. This paper presents an analysis of the capacitor voltage stability for the SPB converter. From the analysis, criteria for stability are derived and three alternatives of a suitable balancing controller are designed. The proposed controller alternatives and their associated stability properties are verified on an experimental setup and by simulation. [ABSTRACT FROM PUBLISHER]

This paper describes a novel modeling approach for self-oscillating resonant power converters operating under a control method based on the variable structure of the system (VSS). Using a fundamental harmonic approximation, the link between control and switching frequency in steady state is found to be accurately described by an affine function that depends on the load. Besides, this link has been extended in order to characterize the control-to-switching frequency dynamics, resulting in a novel small-signal continuous-time model. The resulting control-to-switching frequency transfer function can be appended to the well-known models for frequency modulation, in order to obtain a complete control-to-output system. The new model exposes that the dynamics of the converter under the VSS-based control approach presents advantages with respect to the conventional methods as frequency modulation: 1) reduced dc gain variation for uncertain loads and 2) improved phase margin at high frequencies. The dynamic modeling is complemented with the design of a controller for regulating the output voltage of a parallel resonant converter, whose performance and robustness are compared with the standard frequency modulation. Numerical simulations and experimental results confirm and verify the analytical derivations. [ABSTRACT FROM AUTHOR]

This paper proposes an individual phase current control (IPCC) method based on optimal zero-sequence current separation for star-connected cascade STATCOMs under unbalanced grid voltage. The IPCC is adopted to get better adaptation to unbalanced conditions. Each cluster of the cascade STATCOM has its own phase current control loop and dc-voltage feedback loop, and it can generate the necessary negative-sequence current automatically to rebalance power. However, the zero-sequence current which is unnecessary and harmful in star configuration is introduced in the process. An optimal zero-sequence current separation is presented to remove the zero-sequence current by reconstructing the reactive current command. This improved IPCC enables star-connected STATCOMs adapt to unbalanced conditions without the need for any power balancing algorithms. Also, the operation range of the proposed control method is analyzed. Simulation research studies are performed to verify the operation range analysis, and the experimental operation is tested on a 25-level ±10 Mvar/10-kV STATCOM product installed at a wind farm. [ABSTRACT FROM PUBLISHER]

Switched-capacitor (SC) converters are gaining popularity due to their high power density and suitability for on-chip integration. Soft-charging and resonant techniques can be used to eliminate the current transient during the switching instances, and improve the power density and efficiency of SC converters. In this paper, we propose a split-phase control scheme that enables the Dickson converter to achieve complete soft-charging (or resonant) operation, which is not possible using the conventional two-phase control. An analytical method is extended to help in the analysis and design of split-phase controlled Dickson converters. The proposed technique and analysis are verified by both simulation and experimental results. An 8-to-1 step-down Dickson converter with an input voltage of 150 V and rated power of 36 W is built using GaN FETs. The converter prototype demonstrated a five fold reduction in the output impedance (which corresponds to conduction power loss) compared to a conventional Dickson converter, as a result of the split-phase controlled soft-charging operation. [ABSTRACT FROM AUTHOR]

This paper studies a regenerative cascaded multilevel converter that substitutes active front ends for the diode-based front ends only in part of cells, and proposes a power tracking control strategy that does not need any motor parameters. During the induction motor's deceleration, by controlling the two kinds of cells' output voltages according to the motor's power factor angle, the converter makes the motor-generated energy wholly collected by regenerative cells; thus, other cells' dc-link voltages remain stable. Regeneration limitation is analyzed. The simulation results of a 6-kV six-cell cascaded converter and experiments on a laboratory cascaded converter verify that the converter can transfer the motor power back to the grid and allows the motor to decelerate more quickly. Moreover, the control strategy is suitable for the drive systems whose regenerated power cannot be estimated or is varying. [ABSTRACT FROM PUBLISHER]

This paper investigates the different control objectives, such as loss reduction, neutral point (NP) balance and noise reduction of the space vector modulation (SVM), for the three-level neutral point clamped (NPC) converter. A detailed loss model and simulation model is built for quantitative loss and NP voltage ripple analysis. An improved SVM method is proposed to reduce NP imbalance and switching loss/noise simultaneously. The coordinately selected small vectors consider both the NP charge and the pulse sequence so that the minimized NP ripple and switching events are guaranteed in one switching cycle. In addition, the switching events between switching cycles are also considered to reduce the total switching loss. This method ensures an evenly distributed device loss in each phase leg and also a constant system efficiency under different power factors. The control result for NP balance and loss reduction is verified by using both a simulation model and an experimental prototype on a 200-kVA three-level NPC converter hardware. [ABSTRACT FROM AUTHOR]

In this paper, a generalized switching technique for cascaded H -bridge (CHB) converters is proposed. To take advantage of both low- and high-frequency modulation techniques, a hybrid modulation method is utilized. The proposed technique employs the low-frequency switching for voltage balancing of the dc-link capacitors, and the high-frequency sinusoidal pulse-width modulation switching for shaping the input ac current. Using the proposed technique, the stable operating region of CHB converters is extended. The proposed technique is capable of maintaining the dc voltages balanced even under critical operating conditions in which the load of one H-bridge cell is removed. The validity and effectiveness of the proposed method is confirmed by several simulation and experimental tests on a seven-level CHB rectifier. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is a newly introduced switch-mode converter topology with the potential for high-voltage and high-power applications. This paper focuses on the design and control methods for fault-tolerant operation using redundant submodules (SMs), which is one of the most important features in the MMC topology. By comparing three design schemes of redundant SMs, the most economic and reliable scheme is identified. In addition, a mathematical model of the MMC with arms containing different numbers of SMs is developed. Based on the identified scheme and mathematical model, an energy-balancing control strategy is proposed to keep the MMC operating normally under SM fault conditions. Finally, time-domain simulations of a 61-level MMC system are performed, using the PSCAD/EMTDC software, while experiments are carried out on a 41-level MMC prototype. The simulation and experimental results validate the design scheme, mathematical model, and proposed energy-balancing control strategy. [ABSTRACT FROM AUTHOR]

Due to the high integration of renewable energy, the power systems may become more susceptible to unbalanced grid voltages, grid frequency disturbances, harmonic resonances and others. Therefore, several works have pointed out that the ancillary services provided by the energy storage systems can minimize these issues. The combination of energy storage and static synchronous compensators (ES-STATCOM) has been proposed to reduce the cost. Modular multilevel converters (MMC) are featured as a good solution for ES-STATCOM realization, due to their high efficiency, modularity and inherent fault-tolerant structure. However, the study of the integration of the MMC based ES-STATCOM in a complex power system composed of power electronic converters, transmission system, renewable plants, transformers, etc, leads to a high computational burden. Therefore, this work presents a detailed design and implementation of three efficient simulation models of the MMC ES-STATCOM. The performance of these models compared during a grid frequency support case study by a 100 MVA/33 kV ES-STATCOM. In addition, the performance of these models is evaluated during a battery charging process and a grid symmetrical fault. The models are compared through the following aspects: processing time, normalized integral of absolute error, state-of-charge estimation and active and reactive power dynamic response. [ABSTRACT FROM AUTHOR]

For flyback converter applications, an accurate model of the transformer is necessary for simulation studies, as well as a basis for model-based controller design. In general, transformer modeling has either focused on the winding model, using frequency-domain methods, or on the nonlinear core model, using time-domain methods. Nonlinear modeling is confined to the time domain and certain difficulties have precluded the use of time-domain methods for winding model estimation, resulting in the lack of integrated modeling approaches. This paper focuses on identifying a complete nonlinear dynamic model of a 3-winding transformer using time-domain system identification approaches. Our study demonstrates a possible way to handle the difficulties of working in the time domain and provides a model at least as accurate as that obtained with the frequency response data. In addition to the parameters of the Jiles-Atherton model, which is used to describe the nonlinear core behavior, the air-gap length is also computed from the experimental data to enhance the core model accuracy. The obtained transformer winding model, core model, and full model are experimentally verified. [ABSTRACT FROM AUTHOR]

In this paper, an autoconnected-transformer-based 20-pulse ac–dc converter is proposed for harmonic current reduction in switched-mode power supplies (SMPSs) of moderate rating (10–15 kW). The proposed ac–dc converter is realized with a fractional magnetic rating of the load. The supply current is nearly sinusoidal with low total harmonic distortion, and the power factor is close to unity. A set of power quality indices at three-phase utility for an SMPS is presented for both 20- and 6-pulse converters to compare their performances. It is determined that the power quality indices at ac mains with a 20-pulse converter meet IEEE Standard 519 even at varying loads. A laboratory prototype of an autoconnected-transformer-based 20-pulse ac–dc converter has been designed and developed to validate the findings from simulation. Various tests have been conducted on it, and the test results conform to the simulation results. [ABSTRACT FROM PUBLISHER]

Modular multilevel converters (MMC) are considered a top converter alternative for voltage-source converter (VSC) high-voltage, direct current (HVDC) applications. Main circuit design and converter performance evaluation are always important issues to consider before installing a VSC-HVDC system. Investigation into a steady-state analysis method for an MMC-based VSC-HVDC system is necessary. This paper finds a circular interaction among the electrical quantities in an MMC. Through this circular interaction, a key equation can be established to solve the unknown circulating current. A new steady-state model is developed to simply and accurately describe the explicit analytical expressions for various voltage and current quantities in an MMC. The accuracy of the expressions is improved by the consideration of the circulating current when deriving all the analytical expressions. The model's simplicity is demonstrated by having only one key equation to solve. Based on the analytical expressions for the arm voltages, the equivalent circuits for MMC are proposed to improve the current understanding of the operation of MMC. The feasibility and accuracy of the proposed method are verified by comparing its results with the simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency solar array simulator (SAS) implemented by an LLC resonant dc–dc converter is proposed to save the cost and energy of photovoltaic (PV) system testing. The proposed converter has zero-voltage switching (ZVS) operation of the primary switches and zero-current switching (ZCS) operation of the rectifier diodes. By frequency modulation control, the output impedance of an LLC resonant converter can be regulated from zero to infinite without shunt or serial resistors. Therefore, the efficiency of the proposed SAS can be significantly increased. The circuit operations are analyzed in detail to derive the theoretical equations. Circuit parameters are designed based on the practical considerations. Finally, an illustrative example is implemented to demonstrate the feasibility of the proposed SAS. [ABSTRACT FROM AUTHOR]

This paper focuses on the common-mode voltage reduction and the power quality of matrix converters for a low-voltage transfer ratio of less than 0.5 by the direct space vector modulation (DSVM) method. The principles of selecting suitable switching configurations based on new space vector sectors are described, and an entire switching table for the new control strategy is developed. The matrix converter with the proposed method reduces peak-to-peak common-mode voltage remarkably. The new DSVM method has advantages over the conventional DSVM method, such as lower total harmonic distortion of line-to-line output voltage and a reduction in switching loss by a minimum number of switching commutations. The proposed DSVM method can be easily implemented in software. Simulation and experimental results are shown to verify the effectiveness of the proposed DSVM method. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dual-input matrix converter (DIMC) to integrate two three-phase ac type energy resources to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six-switch voltage source converter replaced by a nine-switch configuration. With the additional three switches, the proposed DIMC can provide six input terminals, which make it possible to integrate two independent ac sources into a single grid-tied power electronics interface. The proposed converter has input-to-output voltage boost capability since power flows from the converter's voltage source side to its current source side. Commanded currents can be extracted from the two input sources to the grid. The proposed control and modulation schemes guarantee sinusoidal input and output waveforms as well as unity input power factors. The simulation and experimental results using a laboratory prototype are provided to validate the effectiveness of the proposed control and modulation schemes for the proposed converter. [ABSTRACT FROM PUBLISHER]

The matrix converter is a single-stage ac–ac power conversion device without dc-link energy storage elements. Any disturbance in the input voltages will be immediately reflected to the output voltages. In this paper, a modified space vector modulation strategy for matrix converter has been presented under the abnormal input-voltage conditions, in terms of unbalance, nonsinusoid, and surge (sudden rising or sudden dropping). By using the instantaneous magnitude and phase of input-voltage vector to calculate the voltage modulation index and input-current phase angle, this modified modulation strategy can eliminate the influence of the abnormal input voltages on output side without an additional control circuit, and three-phase sinusoidal symmetrical voltages or currents can be obtained under normal and abnormal input-voltage conditions. The performance of the input currents is analyzed when the matrix converter uses different modulation strategies. Some numerical simulations are presented to confirm the analytical results. Tests are carried out on a 5.5-kW matrix converter prototype. Experimental results verify the validity of the proposed strategy. [ABSTRACT FROM AUTHOR]

Common-mode voltage (CMV) is responsible for overvoltage stress to the winding insulation and bearing damage of an ac motor. High dv/dt of CMV raises leakage currents, which can cause serious problems such as motor damage and electromagnetic noise to the equipment installed near the converter. This paper proposes two modulation strategies for indirect matrix converters that substantially eliminate CMV. The first method is developed by using the suitable couple of nonzero space vectors instead of zero space vectors in the inverter stage. The maximum voltage transfer ratio of this method is unaffected and remains 0.866. The second one, which is useful for low-voltage operation, is approached by choosing the medium and the lowest positive line-to-line input voltages in the rectifier stage to generate the dc-link voltage and by placing suitable zero space vectors in the inverter stage. In the second method, the maximum voltage transfer ratio is 0.5. Both methods can mitigate the peak value to 42%. In addition, while the first method provides the same performance to the conventional method, the second method can reduce significantly the harmonic components of line-to-line output voltage. Simulation and experimental results are shown to verify the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Multilevel voltage-source converter topologies are widely used today in high-power applications such as medium-voltage drives. On the other hand, studies on matrix converters (MCs) have been mainly limited to the low power range. With the intention to combine benefits from both multilevel structure and direct power conversion, this paper investigates the topologies and operating principles of multimodular MCs (MMMCs). Composed of three-phase-to-single-phase MC (3 \times 2 MC) modules, two versions of MMMCs are presented and studied. Modulation schemes to synthesize sinusoidal waveforms on both input and output sides of the converters are elaborated. Having features such as modular design, relatively low switching frequency, and capability of using low-voltage power semiconductor devices, the presented MMMCs are intended for possible use in higher power applications where four-quadrant operation and fast dynamic response are expected. Simulation and experimental results are provided to verify the validity of the study. [ABSTRACT FROM AUTHOR]

The matrix converter (MC) is arousing considerable attention as an alternative for conventional ac/ac converters due to the advantages it offers. However, the control and modulation of this converter is complex. This, together with the fact that the MC usually operates at high modulation frequencies, makes the computational load of the platform to be simulated excessively high. All this makes the simulation time of models including the MC excessively long, even more so when both the transient and steady state of the system must be analyzed. This paper presents a new MC simulation technique called Switching State Matrix Averaging (SSMA). Although this is a fixed-step technique, a long simulation step can be used without forfeiting the accuracy of an ideal variable-step simulation. Likewise, the SSMA drastically speeds up the simulation, reducing the amount of required resources and the tuning time of the complex platforms in which the MC is used. A series of simulations has been performed in order to verify the proposed method. Moreover, a comparison between experimental and simulation results has been made, demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a new topology of a cascaded multilevel converter is proposed. The proposed topology is based on a cascaded connection of single-phase submultilevel converter units and full-bridge converters. Compared to the conventional multilevel converter, the number of dc voltage sources, switches, installation area, and converter cost is significantly reduced as the number of voltage steps increases. In order to calculate the magnitudes of the required dc voltage sources, three methods are proposed. Then, the structure of the proposed topology is optimized in order to utilize a minimum number of switches and dc voltage sources, and produce a high number of output voltage steps. The operation and performance of the proposed multilevel converter is verified by simulation results and compared with experimental results of a single-phase 49-level converter, too. [ABSTRACT FROM AUTHOR]

This paper presents a nanotechnology-based high-power-density and low-power-loss on-chip power inductor for dc–dc switching power converters. This power inductor utilizes a composite of bundled multiwalled (concentric) carbon nanotubes (BMWCNTs) and Fe (iron) in order to achieve high performance in a small size. Titanium (Ti) is then added as a coating material on the BMWCNT-based power inductor. The BMWCNT-based power inductor with a single layer and three turns occupies an area of \200\ \mu\m \times \200\ \mu\m. It exhibits an inductance of 206 nH, a quality factor of 427 at 20 MHz, and a dc rated current of 100 mA. The power inductor size and the performance characteristics are competitive with state-of-the-art power inductors. The design, analysis, modeling, and simulation results of the BMWCNT-based power inductor are presented and compared with state-of-the-art conventional power inductors from the literature. [ABSTRACT FROM AUTHOR]

This paper presents a pulsewidth modulation (PWM) algorithm for a three-phase ac–dc rectifier, where the third and fifth harmonics are indicated in the input phase voltages. A mathematical analysis, which includes this voltage harmonic's components, shows that the unity input displacement factor (IDF) can be reached by appropriate evaluation of duty-cycle functions. A PWM algorithm is proposed based on this developed theoretical achievement. This approach enables current sensorless unity IDF rectification. The PWM algorithm is investigated theoretically and verified by simulations and experiment. [ABSTRACT FROM PUBLISHER]

This paper proposes a new topology for bidirectional multiinput direct dc–ac converter for clean-power-generation system, therefore, at the input port, a boost converter is used to meet the requirement of many distributed generation systems, such as photovoltaic, and fuel cell systems. The boost converter can increase the dc input voltage. This point results in a turn ratio reduction of high-frequency isolating link transformer. Furthermore, the boost inductor reduces the input current ripple, therefore, the saturation of the transformer can be avoided for higher output currents. The count of used devices has been reduced in the proposed converter. As a result, the cost, size, and the volume of the converter can be reduced. The reduced conversion steps increase the efficiency of the converter. The converter is analyzed step by step to show the principles of the operation in providing energy management based on duty-cycle variations. The system capability in different operation conditions has been simulated, and the simulation results have been compared with measurement results. Dynamic analysis and control design of the bidirectional dc–ac converter is presented based on nonlinear control by input–output feedback linearization. [ABSTRACT FROM AUTHOR]

In this paper, a cascade controller is designed and analyzed for a boost converter. The fast inner current loop uses sliding-mode control. The slow outer voltage loop uses the proportional–integral (PI) control. Stability analysis and selection of PI gains are based on the nonlinear closed-loop error dynamics. It is proven that the closed-loop system has a nonminimum phase behavior. The voltage transients and reference voltage are predictable. The current ripple and system sensitivity are studied. The controller is validated by a simulation circuit with nonideal circuit parameters, different circuit parameters, and various maximum switching frequencies. The simulation results show that the reference output voltage is well tracked under parametric changes, system uncertainties, or external disturbances with fast dynamic transients, confirming the validity of the proposed controller. [ABSTRACT FROM AUTHOR]

The Z-source inverter has gained popularity as a single-stage buck–boost inverter topology among many researchers. However, its boosting capability could be limited, and therefore, it may not be suitable for some applications requiring very high boost demand of cascading other dc–dc boost converters. This could lose the efficiency and demand more sensing for controlling the added new stages. This paper is proposing a new family of extended-boost quasi Z-source inverter (ZSI) to fill the research gap left in the development of ZSI. These new topologies can be operated with same modulation methods that were developed for original ZSI. Also, they have the same number of active switches as original ZSI preserving the single-stage nature of ZSI. Proposed topologies are analyzed in the steady state and their performances are validated using simulated results obtained in MATLAB/Simulink. Furthermore, they are experimentally validated with results obtained from a prototype developed in the laboratory. [ABSTRACT FROM PUBLISHER]

In this paper, the operation and the features of a new three-level converter are presented. The proposed topology was named three-level active-stacked neutral point clamped (3L-ASNPC). It is a derivative of the 3L-SNPC structure, having two additional active switches connected antiparallel with the clamp diodes. The main advantage of 3L-ASNPC converter is the reduction of the average switching frequency for all power devices. In the same time, the apparent switching frequency of the output voltage is doubled. Experimental and simulation results are shown in order to validate the proposed structure and the analysis of the switching states. [ABSTRACT FROM AUTHOR]

In this paper, a novel control method of grid-connected voltage-source converters (VSCs) is proposed. The method can be generally applied for all grid-connected VSCs but may be of most importance in high-voltage dc (HVDC) applications. Different from the previous control methods, the proposed method utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine. By using this type of power-synchronization control, the VSC avoids the instability caused by a standard phase-locked loop in a weak ac-system connection. Moreover, a VSC terminal can give the weak ac system strong voltage support, just like a normal synchronous machine does. The control method is verified by both analytical models and time simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of appropriate load sharing in an autonomous microgrid. High gain angle droop control ensures proper load sharing, especially under weak system conditions. However, it has a negative impact on overall stability. Frequency-domain modeling, eigenvalue analysis, and time-domain simulations are used to demonstrate this conflict. A supplementary loop is proposed around a conventional droop control of each DG converter to stabilize the system while using high angle droop gains. Control loops are based on local power measurement and modulation of the d-axis voltage reference of each converter. Coordinated design of supplementary control loops for each DG is formulated as a parameter optimization problem and solved using an evolutionary technique. The supplementary droop control loop is shown to stabilize the system for a range of operating conditions while ensuring satisfactory load sharing. [ABSTRACT FROM AUTHOR]

This paper presents a single-phase multifunctional inverter for photovoltaic (PV) systems application. The converter provides active power to local loads and injects reactive power into the grid providing voltage support at fundamental frequency. The proposed topology is controlled by means of the droopcontrol technique. Hence, it allows the obtaining of voltage-sagcompensation capability, endowing voltage ride-through to the system. A model and analysis of the whole system is given to properly choose the control parameters. Simulation and experimental results validate the proposed control using a 5-kVA PV converter. [ABSTRACT FROM AUTHOR]

This paper proposes an isolated cascaded multilevel inverter employing low-frequency three-phase transformers and a single dc input power source. The proposed circuit configuration can reduce a number of transformers compared with traditional three-phase multilevel inverters using single-phase transformers. It controls switching phase angles to obtain an optimal switching pattern identified with the fundamental frequency of the output voltage. Owing to this control strategy, harmonic components of the output voltage and switching losses can be diminished considerably. To verify the performance of the proposed approach, we implemented computer-aided simulations and experiments using a prototype. [ABSTRACT FROM AUTHOR]

Abstract-Multipulse converters are suitable for high-power application with the merits of low switching frequency and perfect harmonic performance. But less controllability and poor regulation lead the restriction on its application. A bidirectional pulsewidth modulation (PWM) converter based on multipulse structure is proposed in this paper, which has the same perfect harmonic performance with very low switching frequency. A special sequential sampling space vector modulation technique, which has the sampling sequence from the lagging module to the leading module, is proposed to make the converter controllable like conventional PWM converters. The harmonic performance and linear regulation capability are analyzed theoretically. The converter is modeled in detail, and an instantaneous feedback control strategy with phase delay compensation and decoupling control is also proposed. The controller parameters are optimized to get high dynamic performance with adequate phase margin and gain margin. A 3-kVA prototype is built, and the simulation and experiment results validate that the proposed converter is quite suitable for high-power conversion. [ABSTRACT FROM AUTHOR]

Abstract-Asymmetric multilevel converters can optimize the number of levels by using H-bridges scaled in the power of three. The shortcoming of this topology is that the H-bridges are not interchangeable, and then, under certain faulty conditions, the converter cannot operate. A reconfiguration system based on bidirectional electronic valves has been designed for three-phase cascaded H-bridge inverters. Once a fault is detected in any of the insulated gate bipolar transistors of any H-bridge, the control is capable to reconfigure the hardware keeping the higher power bridges in operation. In this way, the faulty phase can continue working at the same voltage level by adjusting its gating signals. Some simulations and experiments with a 27-level inverter, to show the operation of the system under a faulty condition, are displayed. [ABSTRACT FROM AUTHOR]