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The research on noninvasive incipient fault diagnosis of power converters is very critical to avoid strenuous periodic check-ups and costly interruptions. Thermal cycling is one of the main techniques to accelerate the package-related failure progress. In this paper, first, a custom designed accelerated aging platform that can expose multiple discrete power MOSFETs to thermal stress simultaneously is introduced. Based on the collected experimental data, the variation of the on-state resistance is identified as the failure precursor, and an exponential degradation model that fits successfully with the experimental data are developed. The remaining useful lifetime (RUL) of degraded power MOSFETs is estimated through classical least-squares algorithm run on experimental data filtered by Kalman Filter which deals with the measurement noise and model uncertainties. The essential advantage of the proposed method is that it does not require junction temperature information. The RUL estimation with limited field data is demonstrated on a number of experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a novel multiphysics and nonlinear model for electromechanical relays is presented. The electromagnetic dynamics is analyzed by calculating the total reluctance of the magnetic equivalent circuit (MEC), which is composed of a fixed length iron core and an angular air gap. Magnetic saturation and angular dependency of the reluctance are considered in the analysis. Then, an energy balance over the electromagnetic components of the system is used to obtain the torque which drives the movable armature. A planar mechanism of four rigid bodies, including spring-damping torques that restrict the motion and model the contact bounces that occur in the switchings, is proposed to explain the dynamics of the movable components. Experimental tests show the accuracy of the model in both the electromagnetic and the mechanical parts. [ABSTRACT FROM AUTHOR]

Coupled-inductor semi-bridge converters, assembled from magnetically linked pairs of complementary unidirectional phase legs, can achieve a substantially improved harmonic output voltage performance with the same number of silicon devices as traditional converters. However, they must be operated so as to ensure that a continuous common-mode current always flows through each coupled inductor, to ensure each phase leg can always produce the required switched output voltage. This is particularly challenging for a three-phase coupled-inductor bridge controlled by phase disposition (PD) modulation, since there is no direct correlation between the modulator output and the individual phase leg switching device commands. This paper presents a novel strategy to control each phase leg’s common-mode inductor current under PD modulation, by introducing a square wave offset signal into the modulator reference command, and feeding the modulator output through a postprocessing state machine to correctly switch each semi-bridge phase leg to maintain the required dc common-mode current. The strategy has been verified by detailed simulation studies and matching experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, two modulation strategies called Mod-1 and Mod-2 are compared for a three-level diode neutral-point-clamped (NPC) inverter synchronous reluctance machine (SynRM) drive. These modulation strategies do not operate at a fixed switching frequency. A new modulation strategy which operates at a fixed switching frequency is proposed called Mod-3. The SynRM suffers from a poor power factor which makes it harder to archive capacitor voltage balancing for a three-level NPC inverter. These modulation strategies are of the nearest three vector (NTV) family. Mod-1 and Mod-3 choose certain vector states to achieve capacitor voltage balancing, whereas Mod-2 strategy makes use of the inverter vector state’s dwell time. The parameters of interest are the torque ripple, the neutral point (NP) voltage ripple, the inverter efficiency, and the $d$-axis current ripple. Though lower torque ripple and better power quality are registered on Mod-2 strategy. Mod-1 strategy has 14% improvement in inverter efficiency at lower modulation index ($m_i = 0.4$). Mod-2 strategy has 11% more NP voltage ripple at a modulation index of 0.4. One of the disadvantages of Mod-1 strategy is the varying switching frequency. Mod-3 scheme produced higher inverter efficiency, better balancing of the capacitor voltages, and guaranteed fixed inverter switching frequency. The disadvantage with Mod-3 strategy is that it generated higher torque ripple, $d$-axis current ripple, and current total harmonic distortion when compared to Mod-1 and Mod-2 at the same load conditions. [ABSTRACT FROM AUTHOR]

In this paper, a new modulation method is proposed for a Z-source three-level T-type inverter (3\mbox{LT}^2{I}). The Z-source 3\mboxLT^2I combines the merits of the Z-source two-level inverter and the advantages of the Z-source neutral-point-clamped inverter. Although the previous literature has proved that the space vector modulation (SVM) technique for Z-source 3\mboxLT^2I produces the desired voltage transfer gain with minimized switching loss, it cannot deal with the neutral-point (NP) potential balance issue. Therefore, an improved SVM method addressing this problem for Z-source 3\mbox{LT}^2{I} is proposed. The method simplifies the space-vector diagram of a Z-source 3\mbox{LT}^2{I} into that of a Z$-source two-level inverter. In order to obtain NP potential balance, the pattern of the conventional symmetric SVM is changed by properly adding or subtracting a percentage of the minimum gate-on time. The upper and lower shoot-through states can be inserted into the improved symmetric SVM, thus offering av few advantages, including boosting ability, NP potential balance, and low switching loss. The considerate stable NP voltage and the boosting gain have been experimentally proven by results from a prototype inverter. [ABSTRACT FROM AUTHOR]

A digital dead-beat current controller for voltage source converters is presented in this paper. The control structure is specified in a digital hardware description language, synthesized, and deployed on a field-programmable gate array chip. By updating, with negligible computation delay, the duty cycle twice in a switching period, the reference current error is nulled in half a modulation period, so that the controller's small-signal bandwidth is maximized. In addition, due to a simple transient detection circuit, the large-signal response delay is reduced to a small fraction of the modulation period, which is determined by the chosen current signal oversampling rate. The controller can effectively support different voltage-source inverter applications, such as active filters, uninterruptible power supplies, microgrid distributed energy resource controllers, and dc–dc converter applications, including interface converters for renewable energy sources, laboratory battery chargers, and electronic welding machines. [ABSTRACT FROM AUTHOR]

This paper proposes a new vector-based dead-time compensation method for three-level T-type converters. The origins and effects of the dead-time voltage errors are analyzed in detail for different switching commutations and load conditions. In order to eliminate the dead-time distortion in each phase, a dead-time error voltage vector is introduced to adjust the reference voltage vector depending on load current polarity. The proposed vector-based dead-time compensation scheme has several advantages. First, it can be applied to multilevel converters with any number of voltage levels using any modulation schemes. Second, the pulse loss issue which is common in conventional pulse-based compensation strategies can be eliminated. In addition, the pulse saturation can be mitigated by operating the converters in overmodulation regions. All of these advantages and effectiveness of the proposed vector-based dead-time compensation method are verified through both simulation and experimental studies. [ABSTRACT FROM AUTHOR]

Smart grid technologies are expected to increase system efficiency and reliability using advancement in automation, communication, computation, and optimization. Several control algorithms have been developed or enhanced for operation and control of smart distribution grid. In recent years, volt/var control (VVC) algorithms have been proposed for energy saving in distribution systems due to advancement provided by smart grid automation and control. VVC helps to lower distribution feeder voltage to decrease energy consumption. However, quantification of this impact is hard due to several external factors such as weather and end users' behavior. On the other hand, existing evaluation methods of VVC algorithms are either not suitable for long-term study or intrusive. This paper addresses these issues by proposing a new technique to estimate “distribution system demand without smart grid implementation” utilizing “data measured from system with smart grid implementation.” Interdependence of voltage and load is considered based on estimated load characteristic. Our key contribution is developing a method for quantifying the real-time energy saving of smart grid automation and control focused on VVC and implementing in an electric utility in eastern Washington, USA. The algorithm is developed using both commercial and open-source software. [ABSTRACT FROM AUTHOR]

The arc flash hazard is related to electrical safety in work place and has gained much attention as part of the safety program for many facilities. An effective approach to reducing the arc flash hazard in existing industrial and commercial facilities is proposed in this paper. To illustrate the proposed approach and provide quantified results, computer simulation is conducted for a large oil field facility and a manufacturing facility in a commercial building as two case studies. The simulation results from the two case studies show significant reductions on the incident energy and the fault clearing time, which verifies the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The maximum power point should be continuously tracked in a photovoltaic (PV) inverter. However, the maximum power point could be found at very low dc-link voltages around sunrise or sunset. Then, the overmodulation (OVM) of the inverter has to be considered to keep the power generation even at low dc-link voltages. In this paper, a series of implementation schemes is proposed to keep the current regulation, even if the inverter is under the OVM. These schemes can be helpful to increase the operating time of the PV inverter, which correlates with the daily amount of power generation. After being examined in a small-scale prototype inverter, the proposed method has been tested with a 250-kW PV inverter installed at a proving ground. In a sunset, the operation time of the inverter has been extended by about 12 min, and the generated energy has been increased by 234 Wh, when compared to the normal operation without the proposed methods. [ABSTRACT FROM AUTHOR]

The amount of the electrical energy used for the interior lighting of medium and large buildings is generally considerable. The European Standard EN15193 was devised to establish conventions and procedures for the estimation of energy requirements of lighting in buildings by an energy performance numeric indicator. This methodology is based on the three derating factors that consider the influence of the daylight exploitation, the occupancy behavior and, if present, of a constant illuminance sensor. The factors are evaluated by a statistical approach on the basis of general reference data tabulated by the same Standard, not considering more detailed parameters of the control system that can impact severely in the effective energy savings. The Standard methodology appears extremely useful for a preliminary evaluation. For a more accurate evaluation, this paper suggests an improvement of the procedure that considers the effective operation time and occupancy behavior, the type of control and lamps, the number of control groups, the technique of modulation (dimming or switching), and the delay in turning off. The suggested procedure is compared with the Standard one to highlight the improvements. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a passive anti-islanding method is experimentally tested for three phase (3\phi) cogeneration systems. The tested method is based on determining the wavelet packet transform (WPT) high-frequency subbands present in the d– q-axis components of instantaneous 3\phi, when evaluated at the point of common coupling (PCC). This passive anti-islanding method is founded based on the nature of instantaneous 3\phi apparent powers that have components continuously exchanged between both sides of the PCC. An islanding condition can be considered as a transient disturbance that creates nonperiodic and nonstationary high frequency components in sd and sq. These frequency components can be parameterized by WPT high-frequency subbands, which can provide accurate detection of the islanding condition. The $d$– $q$ WPT-based anti-islanding method is tested for a $3\phi$ cogeneration system under various loading and power delivery conditions. Performance results reveal accurate, fast, and reliable detection and response to the islanding condition. [ABSTRACT FROM AUTHOR]

The architecture of a mission critical power system has to be designed with structures that allow the simultaneous operation of multiple sources (architecture efficiency). Opportunely organized, the business continuity management will project its program and take actions on the sources. Complete control of the system is necessary for all operating occurrences in an electrical power system. Complexity requires that “safe sets” of operating procedures have to be identified, selected, and authorized, as adopting the Parise program. A Human Competent Reaction has to guarantee the operation efficiency as providing decision-making in emergency statuses. The paper deals with a sample case of a system with multiple sources applying the micro approach of the “flock” logic that consists in managing exclusively the adjacencies of each node. The adoption of mechanical locking tools assists the switching procedures. [ABSTRACT FROM AUTHOR]

This paper proposes a novel 3 $\phi$ stand-alone solar photovoltaic (PV) system configuration that uses high-gain high-efficiency $(\approx\! 96\%)$ dc–dc converters both in the forward power stage and the bidirectional battery interface. The high-voltage-gain converters enable the use of low-voltage PV and battery sources. This results in minimization of partial shading and parasitic capacitance effects on the PV source. Series connection of a large number of battery modules is obviated, preventing the overcharging and deep discharging issues that reduce the battery life. In addition, the proposed configuration facilitates “required power tracking (RPT)” of the PV source as per the load requirements, eliminating the use of expensive and “difficult to manage” dump loads. High-performance inverter operation is achieved through $abc$ to $dq$ reference frame transformation, which helps in generating precise information about the load's active power component for RPT, regulation of ac output voltage, and minimization of control complexity. Inverter output voltage is regulated by controlling the modulation index of sinusoidal pulsewidth modulation, resulting in a stable and reliable system operation. The active power demand is controlled by regulating the dc link voltage. All the analytical, simulation, and experimental results of this work are presented. [ABSTRACT FROM PUBLISHER]

Multilevel converters (MLCs) have emerged as standard power electronic converters for medium-voltage high-power industrial applications. Owing to dominating device switching losses in high-power applications, it is preferable to use low device switching frequency (LDSF) modulation techniques. Then, it is possible to achieve higher device utilization, higher converter efficiency, and reduced cooling requirements. However, there exists a tradeoff between device switching frequency and harmonic distortion of converter output currents. Therefore, the main challenge for LDSF modulation techniques is to minimize the harmonic distortion of the output currents. The goal of this paper is to provide a review of various LDSF modulation techniques proposed in the literature and also discuss in detail about one of the emerging LDSF control techniques known as synchronous optimal pulsewidth modulation. Finally, challenges to LDSF modulation techniques for emerging multilevel topologies and future trends in applications of MLCs are discussed to motivate further research, to enhance the proposed LDSF techniques, and to explore for new alternatives. [ABSTRACT FROM PUBLISHER]

Brushless dc motor drive system employing minimized dc-link capacitor is becoming popular for the reason of compactness and long lifetime. However, once the capacitance is reduced, reversal dc-link current will lead to excessive voltage rise in the dc link when conventional current limit strategy is used. In order to avoid the damage caused by oversize pumping-up voltage, a novel current limit strategy without reversal dc-link current is necessary. In this paper, the traditional all-turn-off current limit logic is replaced by half-turn-off logic. Then, an improved current sampling scheme is presented to replace the cycle-by-cycle mode, which induces failure of current limiting after the elimination of reversal current. Finally, the proposed strategy is verified by simulation and experiment. [ABSTRACT FROM PUBLISHER]

Conventional PI controllers are vulnerable to changes in parameters and are difficult to tune. In this work, an artificial neural network (ANN) based controller is developed for the robust operation of a single-phase modified packed U-cell five-level inverter (MPUC-5) for solar PV application under variable insolation conditions. An MPUC-5 is a converter with a main and an auxiliary dc link of equal magnitude; although five-level operation is also still feasible with different voltages also. The maximum power point (MPP) of a PV array changes with the variation in the solar insolation. This results in a variable voltage at the output of the boost converter while maintaining the load line at the MPP. Consequently, the fundamental value of the output of the MPUC-5 also tends to change. Thus, it is required to produce angles that commit to an ac output voltage with a constant fundamental value and constrained to a minimum total harmonic distortion along with a third-order harmonic mitigation as per the grid codes, irrespective of the change in the dc-link voltages. A genetic algorithm is employed for this purpose. A large dataset is prepared for two-angle and four-angle operation of MPUC-5 under various dc-link voltages and constraints with which an ANN-based controller is trained. A neural network with a hidden layer is trained with the backpropagation technique; and once a correlation is developed, the network can be operated for a wide range of operating conditions. The robustness of the controller is verified through simulation in MATLAB/Simulink environment and validated by experimental emulation in an hardware in loop environment. [ABSTRACT FROM AUTHOR]

A single-phase bridgeless Cuk ac/dc power factor correction (PFC) rectifier with positive output voltage is proposed in this paper. For low output voltage product applications, the rectifier is designed to convert high input voltage to low output voltage. Due to no bridge diodes required and thus decreased input conduction losses, the proposed rectifier efficiency can be improved. The proposed rectifier operates in discontinuous conduction mode, and the current-loop circuit is hence not needed. In addition, only a single switch is used in the rectifier to simplify the control circuit design. A simple translation method to have the positive output voltage in the Cuk converter is presented in the rectifier to reduce the component counts and the cost. The operational principles, steady-state analysis, and design procedure of the proposed rectifier are addressed in detail in this paper. Simulation and experimental results obtained from a 150-W rated prototype circuit with input of 90–130 Vrms, 60 Hz, and output of 48 Vdc have verified the validity of the proposed rectifier. [ABSTRACT FROM PUBLISHER]

This paper targets photovoltaic microinverters (MIVs) with integrated battery storage. The dual-active-bridge (DAB) topology provides bidirectional power flow; however, it generally suffers from poor efficiency and limited regulation accuracy at low power. It is shown that by modifying one switch, the DAB converter can operate as a two-transistor flyback to resolve these two issues. In addition, the dc-link voltage in the two-stage MIV can be dynamically adjusted for optimal performance in DAB mode. The proposed dual-mode control scheme is demonstrated experimentally on a 100-W prototype, with up to 8% increase in converter efficiency at low power. [ABSTRACT FROM PUBLISHER]

Wide-bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are promising materials for next-generation power devices. We have fabricated a normally on GaN-based high-electron-mobility transistor (GaN HEMT) for power electronic converters. In this paper, the current collapse phenomena, which are distinctive characteristics of GaN devices, are evaluated in detail for several voltages with two switching frequencies. We also evaluate a gate drive circuit that we previously proposed for the normally on GaN HEMT with a single positive voltage source. We construct and test prototype circuits for a boost-type dc–dc converter and a single-phase full-bridge inverter with a gate drive circuit. The problems to be solved for the normally on GaN HEMT, which has a (static) voltage rating of over 600 V, are clarified on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a novel bidirectional inverter, named series ac-link inverter. This three-phase inverter belongs to a new class of partial resonant ac-link converters in which the link is formed by a series ac inductor/capacitor (LC) pair having low reactive ratings. The input and output of this converter can be either dc, ac, single-phase, or multiphase. Therefore, they can appear as dc–dc, dc–ac, ac–dc, and ac–ac configurations. In all of these configurations, the ac capacitor is the main energy-storage element, and the inductor is merely added to facilitate the zero-current turnoff of the switches and their soft turn-on. Due to the zero-current turnoff of the switches in the proposed converter, the use of SCRs with natural commutation is possible as well. Since the current and voltage of the link are both alternating, no bulky dc-electrolytic capacitors are required in this converter. This paper mainly focuses on bidirectional dc to three-phase ac conversion. This single-stage inverter can step up or step down the voltage in a wide range. If galvanic isolation is required a single-phase high-frequency transformer can be added to the link. In the proposed inverter, the power can flow in both directions, and therefore, it is an excellent candidate for battery-utility interface and electric vehicle applications. In this paper, the principles of the operation of the proposed inverter, along with its design and analysis, are studied. Moreover, the performance of the proposed configuration is evaluated in this paper. Both simulation and experimental results are included. [ABSTRACT FROM AUTHOR]

This paper describes a high-speed protection circuit for insulated-gate bipolar transistors (IGBTs) subjected to hard-switching faults (HSFs). The reverse transfer capacitance depends on the collector–emitter voltage, and it produces a significant effect on the switching behavior not only under normal conditions but also under HSF conditions. A gate charge characteristic under HSF conditions differs from that under normal turn-on conditions. Hence, an HSF can be detected by monitoring both the gate–emitter voltage and the amount of gate charge during the turn-on transient period. IGBTs can be rapidly protected from destruction by using this method because a blanking time is unnecessary. Simulation and experiment verify the validity of the proposed high-speed protection circuit. [ABSTRACT FROM PUBLISHER]

This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time offset to the three-phase turn-on times. The proper time offset is simply calculated considering the phase currents and dwell time of small- and medium-voltage vectors. However, if the power factor is lower, there is a limitation to eliminate neutral-point oscillations. In this case, the proposed method can be improved by changing the switching sequence properly. Additionally, a method for neutral-point voltage balancing is also proposed. The change in switching frequency by the proposed method and its effects on the outputs are negligible. Simulation and experimental results verify the validity and feasibility of the proposed strategy. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel modulation technique and a new balancing control strategy for a single-phase five-level flying-capacitor (FC)-based active-neutral-point-clamped (ANPC) converter. The proposed modulator can control the FC voltage to follow the requested reference value and simultaneously generate the required ac output voltage regardless of the values of the dc capacitor voltages of the converter. By implementing this method, smaller values of the dc-link capacitor and FC can be used even in applications that could experience ripple or transient in the capacitor voltage. In a single-phase five-level ANPC converter applications, where the capacitors can experience pulsation power and dc-link balancing issues, such as grid-connected photovoltaic system, the selection of the reference voltage value for the FC can play an important role to balance the average values of the dc-link capacitor voltage. The proposed new control strategy uses a new reference voltage for the FC to be applied by the new modulator to have an average balanced dc-link voltages as well as an ac output voltage with good power quality. Simulation studies and experimental results demonstrate the effectiveness of the proposed modulation technique and control strategy even with relatively small dc capacitors to produce high-quality output voltage and current waveforms while maintaining an average balanced dc-link voltages. [ABSTRACT FROM PUBLISHER]

Model predictive control (MPC) has a number of desirable attributes which are difficult to achieve with classical converter control techniques. Unfortunately, the nature of power electronics imposes restriction to the method, as a result of the limited number of available converter states. This, combined with the spread spectrum nature of harmonics inherent with the strategy, complicates further design. This paper presents a method for removing this characteristic without compromising the desirable functionality of predictive control. The method, named modulated MPC, is applied to a two-level three-phase converter and compared with a number of similar approaches. Experimental results are used to support theoretical analysis and simulation studies. [ABSTRACT FROM PUBLISHER]

Various kinds of differential power processing converters and voltage equalizers have been proposed for series-connected photovoltaic (PV) modules to prevent negative influences of partial shading, such as significant reduction in power generation and the occurrence of multiple maximum power points (MPPs), including local and global MPPs, that hinders and confuses MPP tracking algorithms to operate properly. However, since conventional topologies are based on multiple individual dc–dc converters, the required switch count increases proportionally to the number of modules connected in series, increasing the complexity. A two-switch voltage equalizer using an LLC resonant inverter and voltage multiplier is proposed in this paper. The circuitry can be dramatically simplified compared with conventional topologies due to the two-switch configuration. Detailed operation analyses for the LLC resonant inverter and voltage multiplier are separately performed. Experimental equalization tests emulating partially shaded conditions were performed for four PV modules connected in series. With the proposed voltage equalizer, local MPPs successfully disappeared, and extractable maximum power increased compared with those without equalization, demonstrating the effectiveness and performance of the proposed voltage equalizer. [ABSTRACT FROM PUBLISHER]

This paper presents a dual-loop current regulation strategy for coupled-inductor multilevel converters. The basis of the strategy is to recognize that the current in the coupled inductor can be decoupled into independent dc bias and ac load currents, which can be then regulated using separate feedback processes. This allows the system to enforce continuous conduction operation of the inverter phase legs by dynamically varying the dc bias current to track the ac load current. Design principles are presented to account for the different common- and differential-mode load dynamics and to maximize the closed-loop bandwidths of both feedback loops. This ensures that the dc bias current can follow rapid load transient events. Matching simulation and experimental results obtained for a five-level flying-capacitor coupled-inductor inverter are presented to validate the proposed control strategy. [ABSTRACT FROM PUBLISHER]

An application-oriented integration concept for a half-bridge switch assembly has been developed based on the latest generation 70- \mu\m-thin insulated gate bipolar transistors and diodes, which are rated at 600 V/200 A. This paper addresses the design and reliability of the assembly, with a fully bondwireless approach using cylindrical copper bumps. Advanced numerical structural simulation techniques are also applied to assess the influence of interconnect characteristics (material, size, and shape) and try to determine an optimum solution for reducing the stress and creep strain development in the solder joint. Preliminary experimental tests of the power module are also carried out at different switching frequency and loads to prove the validity of the proposed solution in terms of electromagnetic performance. [ABSTRACT FROM AUTHOR]

This paper presents a novel dc–dc converter configuration, which successfully integrates two technologies, including a switched capacitor and a switched coupled inductor, into one converter. By adopting a coupled inductor to charge a switched capacitor, the voltage gain can be effectively increased, and the turns ratio of the coupled inductor can be also reduced. Not only lower conduction losses but also higher power conversion efficiency is benefited from a lower part count and lower turns ratios. The proposed converter is simply composed of six components, which can be further derived to varied converters for different purposes, such as a bidirectional converter. The operating principle and steady-state analysis are discussed in this paper. A 250-W laboratory hardware prototype is completed and verified. The voltage gain is up to 11. The highest efficiency is 97.2%, and the full-load efficiency is kept at 93.6%. [ABSTRACT FROM AUTHOR]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

This paper proposes a space vector modulation (SVM) strategy for asymmetrical cascaded multilevel converters operating under fault conditions on the power cells. During each switching interval, one voltage vector is chosen to be implemented by the high voltage cells. It is then subtracted from the reference, resulting in a new reference for the low voltage cells. However, under fault conditions, if the high voltage vectors are not properly chosen, the converter may saturate. This paper presents a comparison between the choice of the high voltage vector as the nearest one to the reference, and as the one whose domain encompasses it. It is shown that the second choice is better, as it avoids saturation of the converter as much as possible. The proposed SVM is performed in the output line-to-line voltages coordinate system, in which the converter voltage vectors have only integer entries. The algorithm is presented considering as an example a converter with two cells per phase: one of 1 pu that switches with PWM, and one of 2 pu, switching at the fundamental frequency, respectively called low-voltage-high-frequency and high-voltage-low-frequency cells. Finally, experimental results are given to demonstrate and validate the good performance of the proposed SVM. [ABSTRACT FROM AUTHOR]

This paper proposes a novel single-stage electronic ballast with high power factor (HPF) for supplying fluorescent lamps. The presented electronic ballast integrates a dual boost converter with coupled inductors and a half-bridge series-resonant parallel-loaded inverter into a single-stage power conversion topology. The features of the ballast are cost-effectiveness, HPF (\PF > 0.98), high circuit efficiency ( $ > $90%), low input current total harmonic distortion (\THD < 7\%), low level of crest factor (\CF < 1.4), and zero-voltage switching obtained on both two power switches. Operational principles, design equations, and experimental results of one T5-type fluorescent lamp with a rated power of 21 W operating at 50 kHz switching frequency with 110 V-RMS line input voltage are presented. Satisfactory results demonstrate the feasibilities of the proposed ballast. [ABSTRACT FROM PUBLISHER]

Natural balancing of the cell voltages is observed in many multilevel converters, however, this was not previously described for the modular multilevel converter (MMC). This paper introduces a method whereby the self-balancing behavior of the MMC can be described and analyzed. A novel equivalent circuit of the two cell single phase MMC is introduced whereby the unbalance in the system is clearly stated. Using this equivalent circuit a method, using the frequency domain as basis for analysis, is proposed whereby the self-balancing properties of the converter can be described. The method is verified through comparison with simulation results. [ABSTRACT FROM AUTHOR]

Although the maximum collector–emitter voltage of a high-voltage insulated-gate bipolar transistor (HV-IGBT) reaches 3300 V or higher, it still cannot satisfy the requirements of some high-voltage high-power converters. Applying power semiconductor devices in series connection can effectively improve the voltage rating and power rating of a power electronic converter. The key issue of device series connection is voltage balancing in static switching state and dynamic switching state. In this paper, a three-level converter based on series-connected HV-IGBTs is presented, its voltage-balancing subcircuits are analyzed, and the parameter design method for the converter is proposed. During the design process, key performance indexes of the series connection circuit, such as the voltage-balancing effect, loss of the voltage-balancing circuit, switching loss, and switching time, are comprehensively considered. Moreover, component parameters of the three-level converter are calculated considering the influence of the voltage-balancing circuit. The proposed parameter design method is applied in the development of a three-level HV-IGBT (4500 V/600 A) series connection test platform with 10 000-V rated dc-link voltage. Experimental results verify the validity of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a switched capacitor-based converter to drive high-power light-emitting diodes (LEDs). In contrast to conventional constant current dc drivers, the current pulse is provided by a switched capacitor. The proposed approach differs from the traditional switched-capacitor-based one, because it uses a small inductor to improve the switching behavior of the converter. Based on the charge control analysis, the effects of switching devices on the proposed converter are evidenced and evaluated. A 6 W, 24 V laboratory prototype has been implemented, while experimental results are presented and discussed to demonstrate the technical feasibility of the proposed converter applied as LED driver. [ABSTRACT FROM PUBLISHER]

Three optimized pulse-width modulated (PWM) techniques for the overmodulation region of two-level inverter-fed ac drives are introduced and investigated from the harmonic loss minimization point of view. The optimization is elaborated for the lowest loss-factor, which is proportional to the square of the root mean square value of current harmonics. The loss-factors are computed for different switching numbers as the function of the motor fundamental voltage. It is shown that, with respect to the motor heating and torque ripples, the acceptable drive condition can be guaranteed by a relatively low value of an inverter switching frequency up to 96%–97% of maximal possible motor voltage. Furthermore, it is shown that the so-called three-vector methods have considerably better performance in the lower part of the overmodulation region than the so-called two-vector method for the same number of switching. The performance of the techniques is compared with other existing PWM techniques. This paper discusses the implementation details of the proposed optimal PWM techniques. The theoretical results are verified by experimental and simulation tests. [ABSTRACT FROM AUTHOR]

A novel constant current injection-based characterization scheme for the switched reluctance machine (SRM) is proposed here. Unlike conventional characterization methods where the rotor is locked at a fixed position, the current injection-based method maintains the phase current constant while the machine runs at constant speed. A novel current controller, required for the proposed constant current injection scheme, is also proposed in this paper. The predictive control-based current controller works without the machine model being available. The proposed current controller is validated experimentally and is then used to characterize a 4 kW, 1500 r/min 8/6 pole SRM. The characteristics obtained are found to be in good agreement with those obtained using conventional locked rotor tests. [ABSTRACT FROM AUTHOR]

This paper presents a high-power-density high-power-factor GaN-based two-stage electrolytic-free offline LED driver. The LED driver achieves high power density through the use of a hybrid film–ceramic stacked switched capacitor (SSC) energy buffer, and a comprehensive optimization methodology that evaluates various converter topologies and designs and minimizes overall system volume while maintaining high efficiency. Based on this optimization approach, a totem-pole bridgeless boost power factor correction (PFC) converter is selected for the first stage, while a stacked-input isolated LLC dc–dc converter is selected for the second stage. The optimization procedure also minimizes the passive volume of the SSC energy buffer incorporating the volumetric energy density of commercially available capacitors. The optimized SSC energy buffer utilized in the proposed LED driver has 50% less passive volume than a capacitor-only solution. A 600-W prototype LED driver designed using the proposed approach for universal input voltage ${{(90}}-{ 305 \ \text{V}}_{{\text{rms}}})$ and 24-V output voltage is built and tested. The PFC stage achieves a peak efficiency of 98% while the LLC stage achieves a peak efficiency of 95%. The prototyped LED driver achieves a power density of 28 W/in3. [ABSTRACT FROM AUTHOR]

Space vector modulation (SVM) of a Z-source ultrasparse matrix converter (ZSUSMC) can be realized by either using or not using a zero state in the space vector rectification. In this paper, these two modulation schemes are investigated for a cascaded ZSUSMC. It is demonstrated that the input current under the modulation scheme without a zero state is nonsinusoidal, and its harmonics content depends on the output and impedance network inductor currents. In addition, restrictions on operation of the ZSUSMC with low voltage gains are unveiled. Next, aiming at improving the input current quality and suppressing the harmonics content to an acceptable level, an approach for design of the cascaded Z-source network is proposed. Furthermore, an optimal switching pattern, which results in minimum possible number of changes in the switching states of the ZSUSMC, is developed. Using the developed switching pattern, an approach for digital implementation of the SVM schemes on a single conventional digital signal processor (DSP) without employing an additional field programmable gate array is proposed. Hardware-in-the-loop studies of the ZSUSMC modulated under the proposed SVM schemes are carried out to verify their digital implementation feasibility on a conventional single DSP, as well as effectiveness in producing high-quality input/output currents. [ABSTRACT FROM AUTHOR]

As projects to expand the processing capacity of a gas plant located in west Texas were pursued, engineering staff observed that the planned incoming medium-voltage power feeder possessed many of the risk factors that have led to increasingly common control-power transformer (CPT) and voltage transformer (VT) failures in industry due to switching. Such failures could involve significant damage and down time. To address these concerns, a computer simulation study was undertaken. As part of initial data gathering, sweep frequency response analysis (SFRA) measurements were performed in an atypical context to establish resonant characteristics of these instrument transformers. When the remote source breaker was modeled to open, connected VTs/CPTs went into severe sub-power-frequency ferro-resonance with probable catastrophic failure. This was verified by Electromagnetic Transients Program (EMTP) simulations as well as by field measurements. The focus of this paper will be on the determination of this unique form of ferro-resonance, identification of risk factors, novel cost-effective solutions, implementation, and field measurement verification of the proposed mitigation solutions. Field measurements have shown high correlations with the EMTP simulations and have verified the effectiveness of the proposed novel mitigation solutions. [ABSTRACT FROM AUTHOR]

An observer-based control (OBC) strategy for dual-active-bridge converters is proposed in this paper. The target is not only to handle the active power transferring between two terminals, but also to regulate the phase difference between the primary voltage and current around specific minimum value. The value is chosen to reduce the conduction loss in the system. A reduced-order observer is developed to estimate the direct and quadrature components of the transmission current for use in a decoupled current control system. Since the dc terminal current is the only input of the observer, a low sampling frequency is enough to ensure an acceptable precision. Experiment results show that the proposed OBC strategy can help improve the dynamic performance compared with that when using a single loop voltage mode system. Furthermore, at the high power range, the efficiency obtained when employing the OBC method is improved by up to 7.2%. [ABSTRACT FROM AUTHOR]

Power conversion systems based on double-delta sourced winding (DDSW) had an optimization issue in terms of pulsewidth modulation (PWM). This issue was about inefficient employments of voltage levels during PWM and had to be considered for minimizing voltage stresses and current ripples on DDSW. In this paper, a novel method has been proposed to improve the performance of PWM in DDSW-based systems. The proposed method can be simply implemented as a carrier-based PWM and its principles are neatly summarized with equations. Finally, the effectiveness of the proposed method is demonstrated with experimental results, which were obtained by using a transformer and an induction machine. [ABSTRACT FROM PUBLISHER]

Neutral-point-clamped (NPC) multilevel inverter fed high power drives operating at low switching frequency are prone to low-order torque pulsations. For a case of N switching angles per quarter, apart from maintaining the fundamental component, (N-1) voltage harmonics can be eliminated. Consequently, \fracN-12 or lower number of torque harmonics could be eliminated. This paper proposes an optimal pulse-width modulation (PWM), which minimizes the combined root mean square (RMS) value (\tau RMS ) of torque harmonics of order lower than $6N$ at any modulation index (M$) for an induction motor drive fed from an NPC three-level inverter. This paper considers cases of two, three, and four switching angles per quarter cycle of the pole voltage. Compared with synchronized sine-triangle PWM and selective harmonic elimination (SHE) PWM, the proposed PWM reduces the first (N-1$ ) torque harmonics (i.e., \tau _6 ) over a wide speed range. Simulation and experimental results are presented on a 3.7-kW open-loop constant volts-per-Hertz induction motor drive. [ABSTRACT FROM PUBLISHER]

This paper proposes a dual-mode model predictive direct current control (MP-DCC) of a permanent magnet synchronous generator (PMSG). The proposed algorithm is capable of minimizing switching losses in a two-level synchronous generator side converter (SGSC). A new prediction model that takes the converter dead time into consideration when choosing the optimal switching state is introduced. The proposed prediction model provides a more accurate state prediction, ensuring that the states of the system stay inside the control invariant set in the steady state, even in the case of a significant converter dead time. To guarantee recursive feasibility and closed-loop stability, a flexible control Lyapunov function (CLF) is employed as an optimization problem constraint, which enables the minimization of switching losses both during transients and in the steady state. The influence of the converter dead time on the performance of the proposed algorithm is considered, and accordingly, a control invariant set is determined. Simulation results show that stator currents are kept within the control invariant set if dead time is taken into account in the prediction model. Furthermore, the proposed algorithm is implemented in a digital control system and experimentally verified on a 375 kW interior PMSG. Experimental results verify that the proposed control algorithm provides a successful flying start of the PMSG and show that the application of the flexible CLF results in a lower switching frequency, but also in higher current ripple. By adjusting the upper bound of the control invariant set, a desired tradeoff between the low stator current ripple and the minimization of switching losses can be achieved. [ABSTRACT FROM PUBLISHER]

Accurate characterization of power semiconductors over wide operating ranges is a necessity to accomplish better electrical and thermal designs of power converters. Especially, switching losses of power devices are rarely given sufficiently detailed in their datasheets, since they also depend strongly on the driving circuitry and design of the power converter itself. A means to extract the switching losses are double pulse measurements where the desired operating points can be freely chosen. This paper introduces a temperature conditioning unit that allows the adjustment of the junction temperature between −40 °C and 200 °C using thermoelectric coolers (TECs). The unit is for an automated double pulse test bench with dc-link voltages of up to 1 kV and switching currents of up to 1 kA. Up to 1 kW of electrical power is required to power the TECs. The design of the power converter is shown as well as the control scheme. An algorithm, which automatically extracts the switching losses of the measured double pulse waveforms is presented. An exemplary characterization of an Infineon EconoDual power module is conducted and the results are presented. [ABSTRACT FROM PUBLISHER]

This paper presents a reverse mapping based space vector pulse-width modulation strategy for five- and seven-level diode-clamped multilevel inverters. In this method, the space vector is expressed as a sum of a contender vector and an error vector. Here, the actual sector, which contains the tip of the reference space vector, needs not to be found. The vector nearest to the reference space vector is the contender vector. By calculating the vector difference of the contender vector from the reference vector, the error vector is determined. Using translation method, the error vector is translated to the origin of space vector diagram. There will be (n–1) steps in space vector diagram for an n-level inverter. As the error vector amplitude will be less than one step of the space vector diagram, the two-level space vector method can be applied. To obtain a vector that is very close to the reference vector, the determined switching states can be added to the contender vector. This technique can be extended to any n-level multilevel inverter. The performance of five-level and seven-level diode-clamped multilevel inverters is presented using MATLAB/Simulink. The performance of inverters is evaluated by using induction motor load. The experimental results using field programmable gate array are presented for seven-level diode-clamped multilevel inverter. [ABSTRACT FROM PUBLISHER]

Space vector modulation (SVM) is a widely used method for multilevel inverters. Most of the SVM methods are nearest three vector (N3V) based schemes. Therefore, several researchers have proposed advanced implementation algorithms with reduced complexity for N3V methods. However, topologies like neutral point (NP) clamped inverter (NPCI) require some distinctive methods (called as non-N3V methods) to balance NP voltage for high modulation index and low power factor operations. Currently, the existing non-N3V methods exercise highly complex algorithms for duty ratio calculation and subtriangle identification. This paper presents a new approach, suitable for both N3V and non-N3V methods, with reduced implementation complexity. The proposed algorithm is based on an equivalent two-level space vector diagram and does not require any trigonometry, coordinate transformation, or volt-second balance solution. Unlike other carrier-based methods, it can change the switching sequence as well as the duration of redundant vectors. Moreover, the proposed approach does not require extra steps for implementing hybrid modulation and it can also be extended to multilevel topologies. One N3V, two non-N3V, and hybrid methods are developed using the proposed modulation algorithm, and are compared in detail. Simulation and experimentation on a three-level NPCI verify the validity of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

This paper presents the concept of three-phase module-integrated converters (MICs) incorporated in grid-tied large-scale photovoltaic (PV) systems. The current-source converter with dc voltage boost capability, namely the single-stage power conversion system, is proposed for the three-phase PV MIC system. A model predictive scheme with low switching frequency is designed to control the proposed topology in such a way that provides a certain amount of active and reactive power in steady-state operation and also provides a proper ratio of reactive power under transient conditions to meet the low-voltage ride through regulations. To predict the future behavior of current control values and switching states, a discrete-time model of the MIC is developed in the synchronous reference frame. It is demonstrated that the injected active and reactive power can be controlled by minimizing the cost function introduced in the predictive switching algorithm. The proposed structure is simulated in MATLAB/SIMULINK software. An experimental verification is provided to justify the performance of the proposed control method through a 300-VA laboratory prototype. The results verify the desired performance of the proposed control scheme for exchanging both active and reactive powers between the PV MIC and the grid within different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage light-emitting diode (LED) driver based on a bridgeless power factor correction (PFC) converter and a half-bridge CLCL resonant converter for street lighting applications. The proposed single-stage topology integrates the PFC converter and the CLCL resonant converter by sharing active power switches. The bridgeless PFC converter adopts two buck–boost circuits operating in discontinuous-conduction mode to achieve input-current shaping. It uses two diodes instead of a rectifier bridge to reduce the power loss caused by the diodes. Owing to its superior soft-switching characteristics, the CLCL resonant converter is used. The proposed LED driver has superior features, such as high efficiency, near unity power factor, low total harmonic distortion, and relatively few diodes. A 100-W lab prototype is successfully implemented, and the experimental results verify the effectiveness and feasibility of the proposed LED driver. [ABSTRACT FROM AUTHOR]

A self-tuning controller for power transfer regulation in inductive power transfer (IPT) systems is proposed in this paper. The controller enables power transfer regulation around a user-defined reference power level. The converter's efficiency is improved by constantly tuning the switching operations to the resonant current, thereby achieving the soft-switching operations reducing electromagnetic interference in the power converters. The self-tuning capability makes it ideal for dynamic IPT systems with uncertain loads and fluctuating resonance frequency. High operating frequencies can be achieved using the simplified digital circuit design for the controller, proposed in this paper, which delivers a low total propagation delay. Bidirectional power transfer can be enabled by using the proposed controller on both transmitter and receiver sides. In the reverse power flow mode, the primary converter operates as a rectifier and the power transfer is controlled through the secondary converter using the proposed controller. The performance of the proposed controller is analyzed using MATLAB/Simulink and the results are presented. Finally, the proposed controller is implemented experimentally and its performance is evaluated as a case study on an IPT system. The experimental and simulation results conform to each other, and show that the proposed converter can effectively regulate the power transfer with an improved efficiency. [ABSTRACT FROM AUTHOR]