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Superjunction MOSFETs in cascode configuration with low-voltage silicon MOSFETs are evaluated in this paper. The proposed structure combines the good switching performance provided by the cascode configuration with the benefits of the silicon technology such as its robustness, maturity, and low cost. This paper aims to explain and to demonstrate the reduction of switching losses of superjunction MOSFETs in cascode configuration with respect to their standalone counterparts (directly driven). A detailed simulation analysis of power loss contributions is carried out under hard-switching operation. Moreover, experimental evidence is provided using a boost converter (100–400 V) operating in continuous conduction mode for different switching frequencies (100–400 kHz) and output power levels (180–500 W). [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate how latency insertion method (LIM) can be used for real-time simulation of high switching frequency power electronics systems and how this approach can be implemented for scalable Field Programmable Gate Array (FPGA) execution. We first present a summary of the LIM and how this method can be developed into a solver for high-performance FPGA execution. We then present how common power electronics topologies—buck and boost—can be modeled using the LIM approach, followed by how the LIM model of a three-phase dc/ac converter is created. Afterward, we demonstrate the accuracy of the developed FPGA solver through a set of power electronic system examples, with each example compared with near ideal results of same example provided by a traditional electromagnetic transient type solver. We complete the paper analyzing the scalability of the proposed approach on FPGA devices, both in terms of achievable time step as well as of resource usage. [ABSTRACT FROM AUTHOR]

In several electrical dc–ac power conversions, the ac output voltage is higher than the input voltage. If a voltage-source inverter (VSI) is used, then an additional dc–dc boosting stage is required to overcome the step-down VSI limitations. Recently, several impedance source converters are gaining higher attentions [1], [2], as they are able to provide buck-boost capability in a single conversion stage. This paper proposes the merging of the boost stage and the VSI stage in a single stage dc–ac power conversion, denoted as split-source inverter (SSI). The proposed topology requires the same number of active switches of the VSI, three additional diodes, and the same eight states of a conventional space-vector modulation. It also shows some merits compared to Z-source inverters, especially in terms of reduced switch voltage stress for voltage gains higher than 1.15. This paper presents the analysis of the SSI and compares different modulation schemes. Moreover, it presents a modified modulation scheme to eliminate the low frequency ripple in the input current and the voltage across the inverter bridge. The proposed analysis has been verified by simulation and experimental results on a 2.0-kW prototype. [ABSTRACT FROM PUBLISHER]

The main objective of this work is to provide an overview and evaluation of discrete model-predictive control (MPC)-based maximum power point tracking (MPPT) for photovoltaic systems. A large number of MPC-based MPPT methods have been recently introduced in the literature with very promising performance; however, an in-depth investigation and comparison of these methods has not been carried out yet. Therefore, this paper has set out to provide an in-depth analysis and evaluation of MPC-based MPPT methods applied to various common power converter topologies. The performance of MPC-based MPPT is directly linked with the converter topology, and it is also affected by the accurate determination of the converter parameters; sensitivity to converter parameter variations is also investigated. The static and dynamic performance of the trackers is assessed according to the EN 50530 standard, using detailed simulation models, and validated by experimental tests. The analysis in this work aims to present useful insight for practicing engineers and academic researchers when selecting the maximum power point tracker for their application. [ABSTRACT FROM AUTHOR]

This paper introduces a hybrid modular multilevel converter (MMC) with the full-bridge submodules (FBSMs) inserted in the ac side. It is intended for redistributing arm powers of the MMC system to reduce the submodule (SM) capacitor voltage fluctuation by injecting high-frequency powers in upper and lower arms without disturbing the output voltage. New power distribution of the hybrid MMC system can be realized by controlling the SMs and FBSMs working under the high-frequency powers. The proposed FBSMs in the hybrid MMC system also perform as the harmonic power generator to eliminate the common-mode voltages in the ac side. Since the FBSMs locate in the ac side of the hybrid MMC system, the traditional MMC control method can be directly applied in arm control of the hybrid MMC system. Meanwhile, relationship between the arm powers and SM capacitor voltage has been analyzed in detail to reduce the SM capacitor voltage ripples by redistributing the frequency spectrum of arm powers. Simulation and experimental results have also verified the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents an alternative approach to address the control and modulation problem of single-phase three-level converters applied in the high-speed railway electrical traction drive system. Following the principle of deadbeat predictive direct torque control of ac motors, this paper discusses an improved direct power control (DPC) method based on a deadbeat active and reactive power prediction technique. Comparing with the conventional PI-based DPC scheme, the proposed deadbeat predictive DPC scheme can provide these advantageous features: lower current harmonics and THD index, lower active and reactive power ripples, and fewer adjusted parameters. Moreover, compared with PI-based DPC with the PI parameters optimization, this approach can also easily obtain fast dynamic response but without the main voltage orientation. A single-phase three-level space vector pulse width modulation (SVPWM) with inherent neutral-point voltage balancing capability is adopted, which can be combined with DPC scheme as an overall control and modulation system. A series of simulation and experimental tests have been conducted to demonstrate an excellent performance of the deadbeat predictive DPC. In addition, the neutral-point-voltage balancing ability of the adopted SVPWM method has been verified. [ABSTRACT FROM PUBLISHER]

An asymmetric three-level neutral point diode clamped converter for switched reluctance motor drives is proposed in this paper. The modulation method, the dc-link voltage balancing algorithm, and the current control scheme of this converter are presented. The proposed three-level converter is compared with the conventional two-level asymmetric half-bridge converter in terms of cost, current ripple, noise, and power losses. Compared to the conventional two-level converter, the proposed three-level converter has much lower current ripple, lower noise, and higher efficiency. The effectiveness of the proposed converter is verified by both simulation and experimental results. [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]

A recently reported modeling methods for a switched capacitor converter either assume output as “firm” voltage or a resistor to facilitate calculation. When the size of output filter capacitor is moderate, accompanied by noticeable output ripple, previous modeling results may not provide accurate prediction and design guidelines. In this paper, a new modeling technique taking into account the output capacitor effect is proposed for simple dual-phase switched capacitor converters without complex coupling loops. The proposed model employs transient calculation, takes charge redistribution phase into account, and includes the duty cycle, switching frequency as well as output capacitor simultaneously in the final output impedance formula, which enhances accuracy of the model. It is suitable for interleaved and noninterleaved switched capacitor converters. The simulation and experimental results for the unity gain SC converter are provided to verify the proposed theory. [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 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]

This paper presents two single-phase to three-phase conversion systems for a three-phase load application. The load is connected to a single-phase grid through an ac–dc–ac single-phase to three-phase converter. The single-phase rectifier is composed of two parallel single-phase half-bridge rectifiers. The first proposed topology is composed of a full-bridge three-phase inverter, i.e., three-leg inverter, while the other topology is composed of a two-leg inverter. Suitable modeling, including the circulation current, and control strategy are presented. A pulsewidth modulation (PWM) technique using a single or double carriers PWM implementation is presented. Proposed topologies permit to improve the harmonic distortion. In addition, the P5L converter can reduce the converter power losses. Finally, simulation and experimental results are presented for validation purposes. [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]

Multilevel cascaded H-bridge converters are promising candidates for large-scale photovoltaic power plants. They allow direct connection to medium-voltage distribution networks without the presence of bulky line frequency power transformers. Owing to the stochastically variable nature of irradiance level, ambient temperature, and other factors, power levels in the three phases are expected to be unequal. The power imbalance condition creates unexpected problems with this topology, which was initially designed to operate under balanced power conditions. To deal with this issue, the paper proposes three novel zero-sequence injection methods as an expansion to the conventional zero-sequence injection method. Results obtained from simulations and a 430-V 8-kW three-phase seven-level cascaded H-bridge prototype are presented to verify the effectiveness and feasibility of the proposed methods. [ABSTRACT FROM AUTHOR]

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]

Voltage source back-to-back power converters are widely used in grid-tied applications. This paper presents a quasi-centralized direct model predictive control (QC-DMPC) scheme for back-to-back converter control without a dc-link outer-loop controller. Furthermore, the QC-DMPC is experimentally compared with a conventional proportional-integration (PI) dc-link controller-based DMPC (PI-DMPC) scheme. For the QC-DMPC scheme, the dc-link voltage is directly controlled by a grid-side predictive controller using a dynamic reference generation concept and load-side power estimation. For the PI-DMPC scheme, the dc-link voltage is controlled by an external PI controller. Both schemes are implemented on a field programmable gate array (FPGA)-based platform. Effectiveness of the proposed QC-DMPC is verified by both simulation and experimental data. Moreover, FPGA implementation issues (resource usage and timing information), dc-link control performance, and robustness to parameter variation of the two DMPC schemes are compared in detail. The results emphasize that the QC-DMPC may outperform the PI-DMPC scheme in normal operation but with a slightly higher usage of FPGA resources. However, PI-DMPC scheme is more robust when parameter variations are considered. [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]

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]

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]

Low system voltage in traction networks, mainly caused by active power absorption of locomotives, adversely affects the performance of the locomotives and also the power transmission capability of the catenary line. This paper introduces a voltage support scheme to compensate for the adverse effects of low system voltage. The proposed method is based on the injection of reactive power through the current-controlled line-side converter of locomotives. Comparing the catenary voltage with its reference value, the error is fed to a high-order controller. The controller generates the quadrature (q)-axis reference value of a current control strategy, which is responsible for the reactive power injection. To design the high-order controller, adopting the nonparametric models of the system at various locations, an optimization-based loop-shaping approach is used. The loop shaping guarantees the stability and the acceptable performance of the closed-loop system for various locomotive positions in the network. The performance of the proposed control strategy is evaluated based on simulation results in MATLAB/PLECS environment. Moreover, implementing a scaled-down laboratory setup, the performance of the proposed scheme is experimentally evaluated. [ABSTRACT FROM AUTHOR]

In this paper, three dc/dc ladder multilevel converters are compared. The first one is the classical ladder topology and the two other topologies presented are based on the classical one. A mathematical calculation of the output resistance and the gain of the converter as a function of the number of levels is carried out for the three topologies in order to estimate the voltage drop due to the output current. These calculations are validated with simulations and experimental results. Finally, the behavior of the three topologies is compared through experimental tests. Results show higher performance for the presented converters compared to the classical ladder. [ABSTRACT FROM AUTHOR]

One of the newest methods for desalinating water is capacitive deionization (CDI). This technology is based on carbon electrodes capable of adsorbing ionic components from water. The aim of this paper is to present the power electronic stage required in a water desalination system that permits recovery of part of the energy involved in the process and its reuse in a high efficient manner. First, the CDI process and the energy recovery are described. Second, a buck-boost converter is designed that allows energy to be recovered while taking into account the large voltage variations at its input and output. The converter is modeled using a mathematical algorithm to study its behavior with large input and output capacitor values. Simulation results are provided as well as experimental data agreeing with them. [ABSTRACT FROM AUTHOR]

Performance of a carrier-based pulsewidth modulation (CB-PWM) strategy can be improved by the inclusion of a zero-sequence voltage in the modulation-reference signal. This paper proposes a new CB-PWM strategy for a three-level neutral-point-clamped (NPC) converter, which is based on a zero-sequence voltage injection. By inclusion of the zero-sequence voltage, the sinusoidal-modulation reference is modified to 1) carry out the voltage-balancing task of the dc-link capacitors, with no additional control effort, 2) reduce the switching losses, and 3) reduce the low-frequency voltage oscillations of the neutral point. The proposed strategy is an alternative approach to the nearest three-vector (NTV) space-vector modulation (SVM) strategy and is obtained by the analysis of the NTV-SVM strategy and establishing a correlation between the NTV-SVM and the CB-PWM strategies. The salient features of the proposed scheme, as compared with the NTV-SVM strategy, are: 1) its reduced computational processing time which is attractive for digital implementation and 2) its reduced switching losses. Compared with the existing CB-PWM strategies, the proposed strategy offers 1) capability to balance the capacitor voltages and reduce the NP voltage oscillations and 2) reduced switching losses. Performance of the proposed CB-PWM strategy for a three-level NPC converter based on time-domain simulation studies in the MATLAB/SIMULINK environment is evaluated and also experimentally verified. [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 analyses the natural voltage-balancing characteristic of a three-phase flying capacitor multilevel converter when it is operated under the spectrally optimal Phase Disposition (PD) pulsewidth modulation (PWM) strategy. Using this analysis, it is shown that PD PWM has superior balancing characteristics compared to the phase-shifted carrier PWM strategy, because it places more spectral energy into the differential-mode sideband harmonics that drive the voltage-balancing process. From this understanding, an alternative balance booster filter network connection is proposed that significantly improves the natural balancing response of a flying capacitor converter for either PWM strategy. The analysis is confirmed by extensive simulation and experimental studies. [ABSTRACT FROM AUTHOR]

Different faulty states of a doubly fed induction generator (DFIG) connected to a microgrid are investigated in this paper. First, the simulation model consisting of two DFIGs connected to IEEE 34-bus test feeder for two vector control based was set up to investigate the transient performance of the microgrid. Then, different types of faults of the DFIGs, including partial loss of excitation (PLOE), complete loss of excitation (CLOE), and interturn short circuit (ISC) were analyzed through the simulation model using vector control strategy. The experimental results indicate that the active power will increase during the PLOE, and the average increase of the amplitude is about 26%, which will decrease the electromagnetic torque by 8% and increase the voltage at the neighbor node, the stability of the microgrid will be broken eventually. For the CLOE, the active power decreases about 80%, and node voltage decreases by 9.4% due to the inverse absorption of the reactive power. When the ISC occurs, the average node voltage and the active power decrease together. Finally, the suggestion for the detection of the DFIG faults is presented, which could be helpful to protect the DFIG from fault accident. [ABSTRACT FROM AUTHOR]

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]

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]

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]

This paper deals with an innovating pulsewidth modulation (PWM) strategy allowing reduction of the dc input current ripples in classical operating area of adjustable-speed drives, and also maintaining a good quality of ac current waveforms and limited switching losses in the inverter. Thus, such a strategy is an interesting solution within embedded systems. Theoretical principles of the proposed method are introduced. Then, simulation results highlight the benefits of this algorithm compared to classical PWM control. Finally, a DSP-base implementation has been performed, and effectiveness of this strategy is confirmed by experiments for a starter-generator application. [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]

In this paper, a new strategy for voltage balancing of distinct dc buses in cascaded H-bridge rectifiers is presented. This method ensures that the dc bus capacitor voltages converge to the reference value, even when the loads attached to them are extracting different amounts of power. The proposed method can be used for an arbitrary number of series H-bridges, different voltage levels, and different power levels in unidirectional or bidirectional rectifiers. To reduce the current harmonics and distortion, the input current is programmed to be sinusoidal and in phase with the input voltage; however, it is possible to adjust the input power factor to control both the active and reactive powers. In the proposed approach, both the low frequency (stepped modulation) and high frequency [pulse-width modulation (PWM)] switching methods are utilized to improve the performance of the rectifier. Using theoretical analysis, the acceptable load power limits for a rectifier with N-H-bridge cells are derived. The validity of the proposed method is verified by simulation and experimental results. [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]

This paper presents a new pulse width modulator capable of adjusting the conversion duty ratio so that the necessary output filter charge will reach its steady-state value in only one switching period, when any disturbance of the input voltage, output current or output voltage occurs. The proposed modulator is based on the calculation of the variation of the electric charge required to restore the steady-state operation in only one switching period, and therefore is designated by one cycle charge control (O3C). The synthesis of the proposed modulator is presented in detail. It will be also shown, theoretically, by simulation and experimentally, that the use of this modulator in a buck converter presents as a major advantage, the fact that the output voltage gain is not limited by the cutoff frequency of the output filter. As a consequence, very low output ripple can be achieved without compromising the dynamic response of the converter. Comparative simulation results considering the presented modulator and the conventional one cycle control, both applied to a buck converter in the same conditions, are also presented. [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]

In this paper a voltage modulation method based on a triangular carrier wave for the three-phase four-leg voltage source converter is described. The four-leg converter can produce three output voltages independently with one additional leg. The proposed modulation method for the four-leg converter can be implemented with a single carrier by a simple but useful "offset voltage" concept. The method is equivalent to the so called three-dimensional space vector PWM method, but its implementation is much easier. The maximum magnitude of the balanced three-phase voltage and the maximum magnitude of zero sequence voltage, which can be synthesized simultaneously, are derived. The feasibility of the proposed modulation technique is verified by computer simulation and experimental results. These results show that a proposed carrier-based pulse width modulation (PWM) technique can be easily implemented without conventional computational burden. [ABSTRACT FROM AUTHOR]