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This paper proposes a new nine-level inverter for medium- and high-power applications. The proposed topology comprises of a three-level (3L) active neutral-point-clamped (ANPC) inverter connected in series with a floating capacitor (FC) fed H-bridge. Besides, two additional switches operating at line frequency are appended across the dc link of the 3L ANPC structure. Compared with conventional hybrid cascaded inverters, the primary advantage of this addition is doubling of the resulting root mean square output voltage. This amelioration is achieved while preserving the standard 3L ANPC and H-bridge structures with minimum topological modification. A simple logic-gate-based voltage balancing scheme is developed to regulate the FC voltage. The proposed voltage balancing method is independent of load power factor, inverter modulation index, and can balance the voltage across FC instantaneously. The step-by-step formulation of logical expressions for the generation of gating pulses is deliberated in detail and can be generalized for any $n$-level inverter. Further, simulation results as well as the experimental measurements obtained from the laboratory prototype are presented to validate the effectiveness and practicability of the proposed configuration. Finally, the notable merits of the proposed inverter over the prior art topologies is established through a comprehensive comparative study. [ABSTRACT FROM PUBLISHER]

Transformer-less grid-connected photovoltaic (PV) systems face the challenge of keeping low leakage current due to their nonisolation configurations. To better attenuate the leakage current in the single-phase systems, a few neutral-point-clamped (NPC) topologies have been proposed. This paper further proposes an active NPC method by only employing one additional switch to connect the midpoint dc link and the freewheeling circuit of traditional single-phase PV inverters. After exploring the operational principles of freewheeling circuits, the construction method and the implementation of active NPC circuits in transformer-less single-phase inverters are elaborated in detail. Since only the leakage current flows through the additional NPC switch, the presented single-phase NPC inverters could still maintain the high operational efficiency with the further attenuated leakage current. The experimental results verified the theoretical findings. [ABSTRACT FROM PUBLISHER]

This paper aims at the design and development of an efficient photovoltaic (PV) array powered switched reluctance motor (SRM) driven pump utilizing a dual supply buck–boost converter. The buck–boost converter, having dual supply, is used as an intermediate dc–dc power conditioning stage between PV array and SRM-pump. To optimize the power of the PV array and to provide soft starting to the SRM drive are the two major concerns of this converter. It also provides voltage balancing of split capacitors, owing to which there is considerable reduction in torque ripple and the required size of it. Moreover, the continuous conduction mode operation of dual supply dc–dc converter minimizes current and voltage stresses on converter indices and reduced electromagnetic interference. The electronic commutation of the SRM drive at fundamental frequency offers reduced switching losses in the midpoint converter and, therefore, considerable enhancement in the efficiency of the proposed system. A dwell angle self-starting control algorithm for a four-phase 8/6 SRM is also implemented in the proposed system. A prototype is developed in the laboratory to validate the performance of the proposed system in different environmental conditions. [ABSTRACT FROM PUBLISHER]

Soft-switching techniques have become very attractive in bidirectional grid-tie dc–ac converters utilizing high-frequency link transformers for galvanic isolation. This paper presents a new pulse-width modulation (PWM) switching technique for controlling a bidirectional isolated dc–ac–ac converter along with its soft-switching method. The proposed PWM technique has the ability to control the input dc current and to inject a sinusoidal three-phase current to the grid at unity power factor. In the first stage, an H-bridge converter is used to convert the dc voltage to a high-frequency square-wave single-phase voltage. In the second stage, a matrix converter is used to convert the high-frequency voltage waveform to conventional three-phase voltage synchronized with the grid. Therefore, a single-phase high-frequency transformer is used to link the H-bridge output voltage to the matrix converter input voltage. The proposed soft-switching technique is achieved by connecting shunt ceramic capacitors across all converter switches. The mathematical model and the circuit operation for soft-switching are presented along with the voltage controllable limits. The effectiveness of the proposed technique has been verified experimentally using a laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper proposes a control method to balance capacitor voltages in a four-switch single-stage two-phase-switched-reluctance motor drive with integrated power factor correction during startup and at low speeds. Initial alignment process is incorporated for switched-reluctance machine before startup. However, the phase currents are unbalanced during that time. This will cause overvoltage on dc capacitors in split-ac configuration leadings to their failure. This problem also exists when the motor speed is very low, as observed in the startup process of compressors. Based on a unified model, an effective control method is proposed to eliminate the voltage difference between the capacitors. This method does not require any additional circuits or components. It also does not affect the performance during normal mode of operation. Experiments are performed to verify the feasibility of the control method. [ABSTRACT FROM PUBLISHER]

A conventional Flyback converter's controller is based on the primary side of the coupled inductor–requiring isolated coupling for both the output voltage measurement and for any synchronous rectification gate signal. A novel communication approach is proposed here, whereby the need for such signal coupling is eliminated by moving the controller to the secondary side and communicating back to the primary switch through the coupled inductor itself. This simultaneously allows direct access to the output voltage, reduced component count, synchronous rectification, and soft primary switch turn-on without optoisolator propagation delay or additional magnetic coupling. This paper presents a novel drain–source voltage sensing method that provides reliable turn-on signals for the primary switch along with the principles of the secondary-side control. Concept feasibility is proven using a 65 W demonstrator with a simple constant-on-time control scheme. The benefits, limitations, and suggested improvements are presented. [ABSTRACT FROM PUBLISHER]

In order to increase the output voltage levels and reduce the isolated dc sources, a symmetrical hybrid nine-level inverter for high-speed motor drive applications is presented in this paper. Each phase of this inverter is composed of a five-level dc/dc converter cell and an H-bridge cell. The dc/dc converter is operated at high frequency with low-voltage devices and the H-bridge is operated at fundamental frequency with high-voltage devices. The three phases are connected to a common dc-link and each drives an isolated winding of an open-winding motor. The operating principles and modulation method are introduced. A detailed analysis of the average currents through the flying capacitor and neutral point of the dc-link is presented and a capacitor voltage balancing method based on phase-shifted pulse-width modulation is proposed. Simulation and experimental results are presented to demonstrate the feasibility of this topology and control method. [ABSTRACT FROM PUBLISHER]

Reliability stress testing of power semiconductors requires significant development effort for a test apparatus to provide the required functionality. This paper presents a modular test system (MTS) architecture that focuses on flexibility, reusability, and adaptability to future test requirements. Different types of tests for different devices in application circuit configuration can be implemented based on the same MTS concept. Vital parameters of the device under test can be acquired in situ during the running stress test. This enables the collection of drift data of these parameters. The control and data acquisition parts of the test system are clearly separated from the actual test circuit. With this physical separation, the same control part can be used for different types of tests. Experimental results of an already implemented test system are provided. [ABSTRACT FROM PUBLISHER]

This paper presents a single-stage solar photovoltaic (SPV) system utilizing an adaptive control scheme. The SPV system includes SPV array, voltage source converter (VSC), ripple filter, nonlinear loads, and a distribution network. The proposed SPV system feeds the active power to the distribution system, provides an effective use of SPV array and mitigation of load harmonics currents. The SPV system with an incremental conductance based control scheme is used for obtaining the maximum power from the SPV array and an adaptive control scheme to control the switching pulses of the VSC. In addition, it utilizes a SPV feed-forward loop to improve the dynamic response and reduces the burden on the proportional-integral controller by regulating dc bus voltage. Test results are presented to validate the control, design, and response of SPV system with various states. [ABSTRACT FROM PUBLISHER]

Boost-derived hybrid converter (BDHC) is a single-stage converter that produces both dc and ac output voltages. The operation of BDHC under continuous conduction mode is satisfactory. However, the nonzero discontinuous conduction mode (NZ-DCM) and standalone ac operation restrict the stable operation of the converter. To mitigate these limitations, modified BDHC (MBDHC) is proposed in this paper. The main idea behind these changes is to redeem NZ-DCM by forced continuous conduction mode (FCM). The adverse effect of NZ-DCM in a BDHC is analyzed in terms of ac output voltage total harmonic distortion, and dc output voltage ripple. This analysis is further extended for MBDHC to highlight the benefits of FCM. Moreover, for hybrid loads, the efficiency of MBDHC is compared with its counterpart BDHC and cascaded boost inverter. [ABSTRACT FROM PUBLISHER]

The conventional “Delta” connected thyristor-controlled reactor (TCR) bank used for static var compensation and other applications is proposed to be split into two identical “Delta” banks each having kvar capacity half of the total TCR capacity. The study presented shows that such combination of two identical “Delta” connected reactor banks, one with phase switching by thyristors and the other with line switching thyristor arrangement can effectively reduce the harmonic generation of the TCR. Since both the three-phase banks are connected in delta, the zero sequence triplen harmonics generated due to phase control of thyristors remain trapped inside the delta, thus reducing the harmonic injection into the power system. Further, some other major characteristic harmonics are also minimized in the TCR line current. Thus, the proposed TCR yields a low current THD which meets the requisite harmonics standards and it can therefore be used as an economic solution for reactive power control over a reasonable range in high power grid without using any external harmonic filter or special phase shifting transformer. This paper describes in detail the modeling, analysis, and performance assessment of the proposed scheme. Simulation results are furnished to evaluate the output characteristics of the scheme under varying operating conditions. Finally, experimental results are presented, which proves the theoretical proposition. [ABSTRACT FROM PUBLISHER]

This paper presents an original modular plug-in-type assembly approach for a single-phase inverter. The main focus here is, indicatively, on the power range 1–20 kW, but the methodology can be transferred to higher power levels too. At the core of the inverter lies a power-dense double-sided-cooled half-bridge power switch architecture with integrated cooler, which is interconnected to filter elements, gate driver, and control circuitry by means of compact flat connectors. The integration exercise targets, on the one hand, the optimization of the power switch performance and reliability, as well as the reduction of circuit parasitic elements; on the other, the production of a system compatible with maintenance and repairing, featuring minimized impact of single component failure on the system maintenance and repair cost, and, thus, on its availability. Preliminary experimental tests demonstrate the nominal functionality of the inverter. [ABSTRACT FROM PUBLISHER]

Open-switch faults in inverter-driven electric drives have recently gained increasing attention in the scientific community. Since these faults may lead to undesired effects, their fast and unambiguous detection is desirable. This paper proposes a detection algorithm for open-switch faults, which is based on the observation of the current control deviation and a subsequent test procedure. This algorithm detects the fault immediately after its occurrence within a few switching periods, even during transient operation. The proposed method is tested via simulations and experiments at different operating points of a surface permanent magnet drive. [ABSTRACT FROM PUBLISHER]

This paper investigates the utilization of two different six-leg configurations of single-phase to three-phase converters. One of the topologies is transformerless and the other is transformer based. The studied converters allow feeding the load voltage with sinusoidal voltages with constant amplitude and frequency, and to operate with sinusoidal grid current with high power factor. The system model and pulse-width modulation techniques for one of the topologies are given. Control strategies for both topologies are provided. The studied topologies are compared with the conventional in terms of dc-link specification, voltages harmonic distortions, semiconductor losses, and other characteristics. Simulation and experimental results are provided to illustrate the operation of the systems. [ABSTRACT FROM PUBLISHER]

A digital predictive current controller for a single-phase grid-side power electronics converter employed in photovoltaic (PV) systems is presented in this paper. A disturbance estimator is employed with the controller in order to minimize its sensitivity to any parameter variation, as well as to reject grid-side disturbances. The design of the controller and the estimator are carried out using the pole placement method. The performance of the developed current controller was tested and verified experimentally using a 5.4-kW grid-connected PV system. These experiments are carried out for different levels of power delivered to the grid under different variation in the system parameters. In addition, other controllers used for interconnected PV systems are also tested to highlight the advantages of the developed current controller. The testing results illustrate the capability of the developed current controller to provide accurate, fast, and robust responses with negligible sensitivity to parameters variations and disturbances on the grid side. [ABSTRACT FROM AUTHOR]

This paper presents an optimized topology for a \text3-\phi three-level inverter with complete elimination of common-mode voltage (CMV). The proposed multilevel inverter (MLI) configuration is realized by modifying a T-structure \text3-\phi inverter. The proposed configuration is an optimized solution with respect to the pulse-width modulation strategy used for CMV elimination. The given three-level inverter structure uses only 16 power semiconductor switches, which is much lower than the existing configurations. A reduced number of power semiconductor devices results in a diminished number of driver circuits, less installation space, and low cost. Further, due to the complete elimination of CMV, the proposed MLI is free from issues such as electromagnetic interference and leakage current with a reduction in filter requirement. The presented topology is also compared with other existing topologies to prove its advantage. It is an optimized solution with respect to the dc bus voltage requirement and the total voltage rating of the devices or the components used in the system. Simulation and experimental results are presented to confirm the capability of the proposed MLI. [ABSTRACT FROM AUTHOR]

Single-phase pulse-width modulation (PWM) rectifier is commonly used in a high-speed railway electric traction system. Occurrence of unexpected failure in the sensors of the detection system may lead to feedback values deviation and system degradation, which can be extremely detrimental to the operation safety of the electric locomotive. This paper presents a fast and reliable fault diagnosis and fault resilient control strategy for catenary current and dc-link voltage sensor faults in the control system for an electric traction single-phase PWM rectifier. Sliding mode observers are designed to produce analytical redundancy. In order to avoid unobservable states and fluctuation introduced by discrete dynamics in observer design, a novel description for switching variables is presented in system modeling. Normalized residuals are generated using measured and observed values. The fault diagnosis unit proposed can detect and isolate three types of sensor faults online by comparing residuals with thresholds. System reconfiguration is realized by substituting the observed values for the information of faulty sensors. Simulation and experimental results are demonstrated to validate the effectiveness of the strategy. [ABSTRACT FROM AUTHOR]

A novel hybrid five-level voltage-source converter for high-efficiency applications is investigated in this paper. Compared with traditional multilevel converters, this hybrid multilevel converter generates desired staircase voltage levels with a reduced number of power devices and isolated drivers at higher voltage levels. It has redundant switching state combinations in hybrid multilevel converter, which makes it easy to balance flying capacitor voltages and realize fault-tolerant operation. A voltage-balancing control strategy based on switching state redundancies is presented for the hybrid multilevel converter to generate desired levels and also keep voltage balance of flying capacitors at the same time. The performance of the hybrid multilevel converter under various operating conditions is investigated in MATLAB/Simulink. The effectiveness of the proposed hybrid multilevel converter is validated by experiment results. [ABSTRACT FROM AUTHOR]

This paper presents a new control strategy for a modified cascade multilevel inverter used in drivetrain operations. The proposed inverter is a three-phase bridge with its dc link fed by a dc source (battery), and each phase series-connected to an H-bridge fed with a floating dc source (ultracapacitor). To exploit the potentials of the inverter for enhanced drivetrain performance, a sophisticated yet efficient modulation method is proposed to optimize energy transfer between the dc sources and with the load (induction motor) during typical operations, and to minimize switching losses and harmonics distortion. Detailed analysis of the proposed control method is presented, which is supported by experimental verifications. [ABSTRACT FROM AUTHOR]

As a result of dead-time, device on-state voltage drop, dc bus voltage measurement error, etc., volt-second errors degrade precise control of torque and flux linkage, particularly at low speeds. This is true for deadbeat-direct torque and flux control, which directly manipulates the volt-second vector sourced by inverters, as well as for indirect field oriented control drives. This paper introduces a real-time sensing scheme to measure the motor terminal volt-second vectors for each switching period with negligible phase lag. Based on the volt-second sensing, a model reference adaptive system-based approach is developed to decouple the volt-second errors from inverter nonlinearity, and dc bus voltage fluctuation and measurement error. By delivering an accurate volt-second vector for each switching period, torque and flux control accuracy, self-sensing performance, and parameter estimation accuracy are significantly enhanced. [ABSTRACT FROM AUTHOR]

This paper proposes a multilevel shunt active power filter (SAPF) to deal with either harmonic current compensation or reactive power compensation. Such a device can reduce the harmonic distortion at the grid currents provided by nonlinear loads located in stiff systems. The proposed SAPF is based on three-phase bridge converters connected to cascaded single-phase transformers. The transformer arrangement permits the compensator to use a single dc-link unit, which simplifies the control strategy and the number of sensors. The multilevel waveforms are generated by using a suitable pulse-width modulation (PWM) strategy associated with the transformer turns ratio. Modularity and simple maintenance make the proposed SAPF an attractive solution compared with some conventional configurations. The model, the PWM technique, and the control strategy are presented, as well as studies considering harmonic distortion and semiconductor losses estimation. Simulation and experimental results are presented in order to validate theoretical approaches. [ABSTRACT FROM AUTHOR]

In recent years, a three-level T-type inverter has attracted considerable attention due to its advantages, such as simple structure and higher efficiency. However, the reliability of a three-level T-type inverter is particularly important as increased power switches are used. Therefore, a fault-tolerant three-level T-type inverter is proposed in this paper. Fault diagnosis and fault-tolerant control strategies for power switches both in half-bridge and neutral-point bridge are investigated. Under fault-tolerant operation, redundant fourth-leg is used to balance neutral-point voltage and the low-frequency voltage oscillation is eliminated completely. The fault ride-through capability and high-quality output waveforms can be obtained. The effectiveness of the proposed inverter topology and control methods is validated by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical harmonic analysis of phase disposition (PD) and phase-shifted carrier pulse-width modulation strategies for modular multilevel converters (MMCs). It is shown that when these strategies are implemented on a per MMC arm basis, their spectral performances converge because of cancellation of odd carrier sideband groups between each phase leg's arms. An improved PD modulation strategy is then presented that uses a single PD modulator for the entire phase leg, followed by a state machine decoder that evenly distributes switching pulses to all submodules across the phase leg upper and lower arms to balance the distribution of submodule commutation events. The resulting strategy achieves optimum phase leg PD spectral performance and also achieves natural voltage balancing of the MMC submodules. All theoretical findings are supported by simulation and experimental results obtained using a five-level MMC prototype. [ABSTRACT FROM AUTHOR]

This paper proposes an error-voltage-based open-switch fault-diagnosis a strategy for a matrix converter (MC). A finite control set model predictive control method is used to operate the MC. The MC system performances under normal operation and under a single open-switch fault operation are analyzed. A fault-diagnosis strategy has also been implemented in two steps. First, the faulty phase is detected and identified based on a comparison of the reference and estimated output line-to-line voltages. Then, the faulty switch is located by considering the switching states of the faulty phase. The proposed fault-diagnosis method is able to locate the faulty switch accurately and quickly without additional voltage sensors. Simulation and experimental results are presented to demonstrate the feasibility and effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Three-phase inverters in uninterrupted power supply, electric vehicles, and hybrid electric vehicles use an intermediate dc-link electrolytic capacitor, which has reliability issues and is one prominent cause of inverter failure and limited life. The large volume of an electrolytic capacitor increases the size and cost of the system. Recent research on electrolytic capacitorless inverters using six-pulse modulation technique along with high-frequency power conversion has attempted to address this issue. However, closed-loop operation and control has some issues due to capacitorless dc-link. In this paper, closed-loop operation, design, and implementation of an electrolytic capacitorless inverter is presented. A proof-of-concept 1-kW hardware prototype has been built and tested in a laboratory under different loading conditions. In total, 98% rated efficiency of the inverter is obtained with total harmonic distortion within 2%. Transient results during start-up and load change are smooth, demonstrating safe operation of the inverter. [ABSTRACT FROM AUTHOR]

This paper depicts an accident that happened in 2010 in a Brazilian chemical plant. A combination of different events, installations, and commissioning errors coupled with equipment failures involving the primary substation resulted in catastrophic failure. A single-phase failure of a 138-kV disconnect switch, during closing, initiated events and phenomena that resulted in a complete plant shutdown. This paper will walk the reader through the events, forensics analysis, and power system analysis that allowed the authors to identify what happened, how it happened, and what to do to prevent it from happening again. This paper will show how the anatomy of the problem, involving equipment failure, single-phase arcing, switching transients, overvoltage, capacitive coupling, transferred surge voltages, ungrounded system, transient overvoltage due to an arcing ground fault on an ungrounded system, insulation coordination, flashover, and lack of adequate surge protection, all of which resulted in a catastrophic failure of an arc resistant switchgear and a potentially serious arc flash incident. The research followed some steps that will be commented on here as well as the lessons learned. [ABSTRACT FROM AUTHOR]

This paper presents a novel approach to achieve both tight dc voltage regulation and direct power factor control by applying general direct space vector modulation (G-SVM) of matrix converter theory to a three-phase ac–dc matrix rectifier. The reduced form of G-SVM and the derivation of the three-phase ac–dc matrix rectifier from a three-phase ac–ac matrix converter are described and theoretically justified. The proposed matrix converter features intrinsic buck conversion, tight output voltage regulation via modulation, inherent capability of four-quadrant operation, elimination of the bulky storage component on the dc bus, and sinusoidal input current. Moreover, the reduced G-SVM-controlled three-phase ac–dc matrix rectifier can achieve leading, lagging, or unity input power factor by simple and direct control of the input current displacement angle. This significantly benefits the potential application of the reduced G-SVM-controlled three-phase matrix rectifier to automotive, aircraft, ship, and other three-phase standby dc supplies. In these applications, the unity power factor control is indispensable when the dc load widely changes. Simulated and experimental verification for this strategy has been presented and discussed in this paper. [ABSTRACT FROM PUBLISHER]

A method for the seamless transition of three-phase inverters switched between grid-tied and stand-alone modes of operation is presented in this paper. In this method, only the inverter current and voltage sensors are utilized, and no control over the grid-side static transfer switch is needed. The presented method contains two strategies for grid-tied-to-stand-alone and stand-alone-to-grid-tied transitions. In the stand-alone-to-grid-tied transition strategy, a novel algorithm is presented for estimating the grid angle nearly instantaneously, which allows the three-phase inverter to respond very quickly if the grid and point-of-common-coupling voltages are out of phase. This fast response allows the inverter to effectively eliminate the transient overcurrent that would normally occur if it was connected to the grid without first being synchronized. The fast response also allows the inverter to return to normal operation very quickly after such an event. The strategy for the seamless transition from grid-tied to stand-alone mode is also presented. These strategies have been verified through experiments, and the results are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper deals with the dimensioning of the capacitors in modular multilevel converters based on analytical equations. Considered design parameters are the (periodic) energy fluctuation, the admissible ripple voltage, and the demand in control reserve. Design examples complete this paper. [ABSTRACT FROM PUBLISHER]

This paper discusses a new circuit configuration and a new control method for a single-phase ac–dc converter with power factor (P.F.) correction and a power pulsation decoupling function. The proposed converter can achieve low total harmonic distortion (THD) on the input current and the power pulsation decoupling function between the input and output sides, which allows low output voltage ripple even on a small output energy buffer at the same time using an active buffer. Therefore, the proposed converter does not require large smoothing capacitors or large smoothing inductors. The buffering energy is stored by a small capacitor, which controls the variation of the capacitor voltage through the active buffer. In this paper, the fundamental operations of the proposed converter are investigated experimentally. The experimental results reveal that the input current THD is 1.44%, the rate of the output voltage ripple is 6.33%, and the input P.F. is over 99%. In addition, a maximum efficiency of over 96% is obtained for a 750-W prototype converter. [ABSTRACT FROM PUBLISHER]

The stacked switched capacitor (SSC) energy buffer is a recently proposed architecture for buffering energy between single-phase alternating and direct current. When used with film capacitors, it can increase the life of grid-interfaced power converters by eliminating limited-life electrolytic capacitors while maintaining comparable energy density. This paper introduces an enhanced version of the bipolar SSC energy buffer that achieves higher effective energy density and round-trip efficiency while maintaining the same bus voltage ripple ratio as the original design. Furthermore, the enhanced buffer uses fewer capacitors and switches than the original design. The enhancement in performance is achieved by modifying the control and switching patterns of the buffer switches. A prototype enhanced SSC energy buffer, designed for a 320-V bus and a 135-W load, has been built and tested. The design methodology and experimental results for the enhanced SSC energy buffer are presented and compared with the original design. This paper also presents a comparison of unipolar and bipolar SSC energy buffers. It is shown that, although bipolar designs are superior in terms of effective energy density at low ripple ratios, unipolar designs can outperform bipolar designs at high ripple ratios. [ABSTRACT FROM PUBLISHER]

Energy harvesting has become a popular source for low-power electronic systems such as wireless sensors and biomedical implants. Energy can be extracted from a number of ambient conditions such as vibration, solar, and thermal gradient. Just like renewable sources, the associated switching power converters can be controlled to harvest maximum power from these miniature systems. However, conventional schemes, such as a conventional maximum power point tracking (MPPT) controller for solar cells, are complex and cannot be utilized in low-power energy systems due to their cost and power requirements. In this paper, a novel optimum energy harvesting scheme is proposed, which controls the duty cycle of the converter to maximize the output power of the system. The control system employs only simple mixed-signal components and can be applied to low-power systems. The proposed scheme does not depend on the characteristics of a specific source and is applicable for different energy systems. In this paper, it is utilized to achieve optimized energy harvesting for two completely different fixed excitation systems, namely, a low-voltage vibration-based electromagnetic microgenerator and a miniature solar cell array. Both simulation and experimental results are provided to validate the proposed scheme. [ABSTRACT FROM PUBLISHER]

In this paper, the recently introduced model predictive pulse pattern control (\MP^3\C) strategy is adapted to the ACS 2000 medium-voltage (MV) drive of ABB. The drive system consists of a five-level active neutral-point-clamped (ANPC-5L) rectifier, an inverter, and an induction machine (IM). The inverter is fed with offline-computed optimized pulse patterns (OPPs) that produce minimum harmonic distortion in the stator windings of the ac machine. An optimal stator flux trajectory is calculated from these OPPs, and a trajectory controller tracks it in real time. In the proposed approach, trajectory tracking is based on model predictive control: a constrained optimal control problem is formulated and solved in real time in a computationally efficient manner. An event-based prediction horizon is employed in order to ensure fast tracking of the stator flux trajectory. The advantages of the proposed method are optimal steady-state behavior in terms of harmonic distortion and fast torque response. The method was tested on an MV ANPC-5L inverter coupled to a general-purpose 1.21-MW IM. Experimental results were obtained from this industrial setup, and they are presented in this paper to demonstrate the high performance of \MP^3\C. [ABSTRACT FROM PUBLISHER]

Temporary voltage sags in the side of network supply voltage are the main cause of untimely stops of automated systems that use adjustable speed drives (ASDs). In this context, this paper presents an analysis of a new hybrid three-phase rectifier which was designed to correct the power factor and to promote voltage-sag ride-through capability to ASDs. In order to prove the effectiveness of the proposed solution, this paper shows experimental results for three case studies, evaluating the performance of the proposed hybrid rectifier under voltage-sag conditions. In all analyzed cases, it was proved that the proposed solution is efficient and can be very attractive for high-power applications. [ABSTRACT FROM PUBLISHER]

Natural daylight in interiors has two main characteristics: It is extremely pleasant to humans, and it is a free energy. The electric lighting system has to be able to combine the daylight contribution with consequent savings on the energy bill. The application of sensors, control systems, and information technologies can reduce significantly the need for human work. Controlling the electric lighting in such a way that the daylighting penetration matches the lighting level to the actual need allows saving on the energy costs and improving the human comfort and efficiency. This paper highlights that lighting controls work with effectiveness if the lighting system is well structured both in luminaire arrangement and control group subdivision, according with a comprehensive approach that considers working zones and daylight contributions. At this aim, this paper suggests an adaptive criterion and a rule of thumb to evaluate the daylight availability and its internal penetration since the preliminary design. [ABSTRACT FROM PUBLISHER]

This paper proposes an electronic driver for public lighting systems. The input stage is based on the integration of two flyback converters with different polarities, in order to avoid the use of the input diode bridge rectifying stage. The output stage is a boost converter with an output current control. The proposed circuit is introduced and analyzed, and a design example for a 50-W light-emitting diode lamp is presented. The most relevant simulation and experimental results are also shown, in order to validate the idea. A comparison in terms of efficiency for the input stage is carried out between the proposed topology and the conventional flyback converter, showing an efficiency enhancement in the proposed converter. However, the most important advantage of the proposed converter is outlined in the final part of this paper. This advantage comes from the avoidance of the input diode bridge, thus enabling the bidirectional power flow at the input stage. Therefore, the topology can be used to deliver energy into the power grid. In recent lighting applications, the use of micro renewable generators in lighting points has made the use of special electronics to handle the energy flows in the ballast necessary. The present topology is an alternative to standard bidirectional input stages. [ABSTRACT FROM AUTHOR]

Pulsewidth modulation (PWM) ac drives generate high line–line motor voltage, up to twice dc bus voltage, due to the reflected-wave phenomenon. Under certain conditions, motor voltage greater than twice the dc bus voltage can occur, resulting in winding insulation failure. It is well known that by suitably adjusting the PWM pulse pattern, the occurrence of voltages greater than twice the dc bus voltage can be avoided, up to a certain maximum cable length; beyond which, output filters are typically used to limit peak motor voltage. It will be shown in this paper that when the inverter operates in the pulse dropping region, voltages greater than twice the dc bus voltage will occur, with existing methods for pulse pattern compensation. A method to adjust the PWM pulse pattern in the pulse dropping region to ensure the same reflected-wave performance as the linear PWM region is presented in this paper. Experimental results are provided to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

High-brightness light-emitting diodes (HB-LEDs) are becoming omnipresent across all aspects of illumination products, due to their incredible characteristics such as efficiency, reliability, long lifetime, controllability, etc. This paper proposes power conversion topologies to drive medium to high power HB-LEDs in three-phase power grids when these connections are available. For that reason, an evaluation of several drivers for medium to high power HB-LEDs in three-phase power grids is done. Moreover, a new topology is proposed, which complies with IEC 1000-3-2 Class C requirements, achieves high power factor, low total harmonic distortion, and the capability to have a flicker free behavior while disposing of the bulk capacitor and having galvanic isolation. The HB-LED driver is based on a modular approach with several cells working together with their inputs connected to the three-phase network and their outputs connected in parallel generating a dc output. Each one of these cells is a dc–dc converter operating as a loss free resistor. In order to validate the concept, a prototype has been built by the use of flyback converters operating in discontinuous conduction mode. Furthermore, it operates in the full range of the European three-phase line voltage, which varies between 380 and 420 V, and it supplies an output voltage of 48 V with maximum power of 90 W. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study with experimental validation of a circulating-current suppression method for parallel operation of three-phase voltage-source inverters (VSI), which may be suitable for modular parallel uninterruptible power supply systems or hybrid ac/dc microgrid applications. The basic concept of the proposed circulating-current suppression method is to modify the original current references by using the current difference among the parallel inverters. In the proposed approach, both cross circulating current and zero-sequence circulating current are considered, and are added into the conventional droop plus virtual impedance control. In the control architecture, the reference voltages of the inverters are generated by the primary control loop, which consists of a droop control and a virtual impedance. The secondary control is used to compensate the voltage drop on the virtual impedance. Furthermore, a circulating-current control loop is added to improve the average current-sharing performance among parallel VSIs. Experimental results are presented to show the effectiveness of the proposed control method to suppress both cross and zero-sequence circulating currents. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a new power electronics circuit topology for wireless inductive power transfer application using current-fed half-bridge converter with CCL-LC resonant network. The major focus is analysis and implementation of a new current-fed resonant topology with current-sharing and voltage doubling features. Generally, inductive power transfer circuits with current fed converter use parallel CL resonant tank to transfer power effectively through air gap. However, in medium power application, this topology suffers from a major limitation of high voltage stress across the inverter semiconductor devices owing to high reactive power consumed by loosely coupled coil. In proposed topology, this is mitigated by adding a capacitor in series with the coil developing series-parallel CCL tank. The power flow is controlled through variable frequency modulation. Soft-switching of the devices is obtained irrespective of the load current. For grid-to-vehicle or solar-to-vehicle, the converter is analyzed and detailed design procedure is illustrated. Experimental results are presented to verify the analysis and demonstrate the performance. [ABSTRACT FROM AUTHOR]

Silicone carbide (SiC) power devices have been optimized in performance over the past decade. However, wide industry adoption of SiC technology still faces challenges from system design perspective. This paper demonstrates an integrated air-cooled three-phase SiC power block for industry applications. The key design aspects, such as high performance gate driver, low parasitic layout, optimized thermal management, as well as flexible control platform are addressed. Experimental results are provided to demonstrate the superior performance of the design. [ABSTRACT FROM AUTHOR]

Computational burden is a major hurdle for practical implementation of finite-state predictive torque control (FS-PTC) of motor drive fed by a multilevel inverter. One of the reasons of computational complexity is that all voltage vectors are evaluated for prediction and actuation. This paper proposes a reduced number of voltage vectors for the prediction and actuation, which are called prediction vectors in FS-PTC. The performance is investigated for a three-level neutral-point clamped inverter fed motor drive in terms of torque and flux response, stator current total harmonic distortion, robustness, average switching frequency, and neutral-point voltage variation. The number of prediction vectors is reduced based on the position of stator flux and the deviation in stator flux from its reference. Experimental results confirm that the computational burden could be reduced by 38%, while the dynamic performance is comparable with the conventional all voltage vectors based FS-PTC. [ABSTRACT FROM AUTHOR]

The performance of a novel three-phase four-leg fault-tolerant T-type inverter topology is introduced in this paper. This inverter topology provides a fault-tolerant solution to any open-circuit and certain short-circuit switching faults in the power devices. During any of the fault-tolerant operation modes for these device faults, there is no derating required in the inverter output voltage or output power. In addition, overload capability is increased in this new T-type inverter compared to that in the conventional three-level T-type inverter. Such increase in inverter overload capability is due to the utilization of the redundant leg for overload current sharing with other main phase legs under healthy condition. Moreover, if the redundant phase leg is composed of silicon carbide metal-oxide-semiconductor field-effect transistors, quasi-zero-voltage switching, and zero-current switching of the silicon insulated-gate bipolar transistors (IGBTs) in the conventional main phase legs can be achieved at certain switching states, which can significantly relieve the thermal stress on the outer IGBTs and improve the whole inverter efficiency. Simulation and experimental results are given to verify the efficacy and merits of this high-performance fault-tolerant T-type inverter topology. [ABSTRACT FROM PUBLISHER]

This paper presents the design, implementation, and experimental validation of a method for fault prognosis for power electronics systems using an adaptive parameter identification approach. The adaptive parameter identifier uses a generalized gradient descent algorithm to compute real-time estimates of system parameters (e.g., capacitance, inductance, parasitic resistance) in arbitrary switching power electronics systems. These estimates can be used to monitor the overall health of a power electronics system and to predict when faults are more likely to occur. Moreover, the estimates can be used to tune control loops that rely on the system parameter values. The parameter identification algorithm is general in that it can be applied to a broad class of systems based on switching power converters. We present a real-time experimental validation of the proposed fault prognosis method on a 3 kW solar photovoltaic interleaved boost dc-dc converter system for tracking changes in passive component values. The proposed fault prognosis method enables a flexible and scalable solution for condition monitoring and fault prediction in power electronics systems. [ABSTRACT FROM PUBLISHER]

On-line condition monitoring is of paramount importance for multilevel power converters used in safety-critical applications. A novel on-line nonintrusive diagnostic method for detecting open-circuit switch faults in silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs)-based T-type multilevel converters is introduced in this paper. The principle of this method is based on monitoring the abnormal variations of the dc-bus neutral-point current in combination with the existing information on instantaneous switching states and phase currents. Advantages of this method include faster detection speed and simpler implementation compared to other existing diagnostic methods in the literature. Moreover, this diagnostic method is immune to the disturbances of inverter's dc-bus voltage unbalance and load unbalance. In this method, only one additional current sensor is required for measuring the dc-bus neutral-point current; therefore, the implementation cost is low. Simulation and experimental results based on a lab-scale 20 kVA adjustable speed drive with a three-level SiC T-type inverter validate the effectiveness and robustness of this novel diagnostic method. [ABSTRACT FROM PUBLISHER]

This paper identifies possible topological reconfigurability of a T-type inverter for direct torque controlled (DTC) induction motor drives when an open-switch fault occurs. In open-switch fault, inverter current path is different than normal path. This causes undesirable inverter switching states. Since DTC is based on a voltage vector selection criterion, open-switch fault causes ambiguous torque control. Analysis of DTC drive under two different inverter open-switch fault conditions viz. half-bridge and neutral-point switch fault are presented. The operation of the inverter in DTC mode against faults is achieved by simple topological reconfiguration. [ABSTRACT FROM PUBLISHER]

Short-circuit detection is a fundamental function of most inverters. In this paper, two new fast and easily implementable short-circuit detection approaches are presented. The first one offers a significantly accelerated desaturation detection. The second one allows a full inverter to be protected by only one short-circuit detection circuit. Both approaches are verified by simulations and hardware tests. [ABSTRACT FROM PUBLISHER]

In this paper, a sinusoidal excited four-phase switched reluctance machine (SRM) with modified dc-assisted windings is presented. The proposed four-phase SRM configuration with modified dc windings has a reduced number of controllable phases and power converter devices. The dc winding configuration is modified from its traditional form by taking advantage of the machine's inherent 90° phase shift between adjacent phases to achieve the desired simplification in the drive. Different power electronic converters for the proposed winding configuration have also been investigated. The proposed concepts are then verified through finite element analysis and an experimental prototype. [ABSTRACT FROM PUBLISHER]

This paper investigates the use of a model-predictive control strategy to control a direct matrix converter. The proposed control method combines the features of the classical model-predictive control and the space vector modulation technique into a modulated model-predictive control. This new solution maintains all the characteristics of model-predictive control (such as fast transient response, multiobjective control using only one feedback loop, easy inclusion of nonlinearities and constraints of the system, and the flexibility to include other system requirements in the controller), adding the advantages of working at fixed switching frequency and improving the quality of the controlled waveforms. Simulation and experimental results employing the control method to a direct matrix converter are presented. [ABSTRACT FROM PUBLISHER]

This paper investigates two power generation systems that utilize a rectifier with small number of controlled switches associated to a two-phase permanent magnet synchronous machine. The proposed topologies have as a main purpose converting wind energy into electrical energy for low-power applications, giving them large potential to be employed in urban and rural areas. Each configuration is commanded by only two controlled switches and has natural protection against short circuit on the dc link. Compared with two three-phase generation systems that use a reduced number of controlled switches, the proposed topologies permit obtaining sinusoidal machine currents, with low harmonic distortion, using a smaller number of controlled switches. At last, to investigate the proposed system and control strategy, simulation and experimental results are presented. [ABSTRACT FROM PUBLISHER]