Search

Provides instructions and guidelines to prospective authors who wish to submit manuscripts. [ABSTRACT FROM AUTHOR]

Energy harvesting has attracted increased attention recently. Energy sources are present all around us, such as, mechanical vibrations, stress, strain, waste heat, sunlight or room light, electromagnetic rays, and chemical or biological sources. Vibration generators based on piezoelectric elements have been highlighted as low-power sources; however, their output power is very low, around the milliwatt or microwatt level, and thus, improving their performance is necessary to make the generated power usable. This paper investigates the use of passive devices to improve output characteristics of the vibration generators. The proposed circuits are a resonator and a passive rectifier. The proposed resonator consists of a parallel inductor and capacitor for $LC$ resonance. The $LC$ resonance equivalently reduces the internal capacitor of the piezoelectric elements. As a result, the output voltage and power are increased compared with that of conventional circuits. In addition, a boost-type current-improving passive rectifier is applied as the passive rectifier. The validity of the proposed circuit is numerically and experimentally verified. [ABSTRACT FROM AUTHOR]

The main technical challenge of the medium-voltage motor drives with modular multilevel converter (MMC) is the serious low-frequency fluctuation on the capacitor voltages, and the existing suppression methods inevitably inject high-frequency circulating currents in MMC. However, the output currents are evidently distorted by the large injected components, while little research has been done to study and solve this problem. This paper analyzes and proves the essential interactions between the output current distortion and the injected components, and the specific dominant output harmonic groups are derived and summarized, revealing the nature of the problem, and it can be taken as a favorable reference for the controller designing. Based on the derivations, this paper proposes a novel suppression method for the greatly improved harmonic characteristics of the output currents during the low-frequency operation. The output harmonics can be accurately measured by the proposed control and effectively suppressed for much lower current total harmonic distortion, benefiting for the superior output control performances with improved efficiency. The simulation results on PSCAD/EMTDC and experimental verifications on a 2.2 kW MMC-based motor drive prototype prove the validity of the presented harmonic analysis and suppression method. [ABSTRACT FROM AUTHOR]

All electrical power equipment, before putting into service, have to pass through numbers of tests to prove their functional performance. In this context, short-circuit test is one of the vital performance tests. A high power alternator used in short-circuit test laboratory is taken as a study object in this paper. Normally, a motor is used as the prime mover for this type of alternator. In this system, the driving motor is eliminated and a thyristor-based static drive is placed to run the machine. The benefit with the static drive is that the single machine can be operated in dual mode, either as a motor or as an alternator. But the negative side of this system is the generation of voltages in the machine shaft. Machine bearings are susceptible to failure if these unwanted shaft voltages cause a high level of bearing currents and persist for a prolonged period. Very little studies were carried out on the power generators related to shaft voltages with perspective to static power supply. This paper explains the details of the static drives applied on this machine for different operational modes. Various causes of generation of shaft voltages are analyzed in view of this special alternator. The outcome of this paper can also be applicable to other large synchronous machines. [ABSTRACT FROM AUTHOR]

In addition to field-oriented control and direct torque control, the model predictive control (MPC) is another typical control method for permanent-magnet synchronous machine (PMSM) drives. In some critical applications, fault-tolerant controls are usually required. The faults of PMSM drives in this paper are limited as a single-phase open-circuit fault, which may be caused by open circuit or short circuit of one power switch. In the postfault operation, the neutral point of the PMSM is connected to a redundant leg. As is known, MPC is a model-based control method. Since the PMSM has different mathematical models in both normal and postfault operations, two different MPCs (MPC-I and MPC-II) should be, respectively, designed for both normal and postfault operations according to traditional thinking. However, it is first found in this paper that the faulty PMSM drive can be treated as an equivalent healthy PMSM drive, and MPC-I can be shared by both normal and postfault operations without any modification. The major contribution of this paper is to find this fact, and verify it with theoretical analysis and experimental validation. Obviously, this finding will simplify the whole control method of PMSM drives considering single-phase open-circuit fault. [ABSTRACT FROM AUTHOR]

This paper presents a new concept of moduleintegrated converters called PVbalancers for photovoltaic applications. The proposed concept enables independent maximum power point tracking for each module, and dramatically decreases the requirements in terms of electrical rating, size, and manufacturing cost for power converters. The power rating of a PV balancer is less than 20% of its counterparts, and the manufacturing cost is thus significantly reduced. In this paper, two architectures of PV balancers are proposed, analyzed, realized, and verified through simulation and experimental results. It is anticipated that the proposed approach will be a low-cost solution for future photovoltaic power systems. [ABSTRACT FROM AUTHOR]

This paper introduces a novel H-bridge structured ac–ac pulsewidth modulation (PWM) converter topology based on two-level non-differential ac chopper legs, which can work at the non-inverting and inverting modes for the utility voltage compensation. Compared to the traditional bipolar-type H-bridge ac–ac converter, no bidirectional switches are switched in a complementary manner to overcome the commutation problem due to the delayed response of electronic circuits and semiconductor switching devices. The detailed PWM control signals and operational principles are presented to regulate the output voltage in a bipolar manner. Especially the main advantage is that the proposed ac–ac converter has the same buck/boost operation process for non-inverting and inverting modes, which ensures the continuously average current supply to the low-voltage output side without a high-value capacitor to support power. Additionally, due to the common sharing ground of the input and output, the feature that output can reverse or maintain phase angle with input is supported well. Then, the detailed analysis, design conditions, and experimental verification based on a 1 kW experimental prototype are presented. [ABSTRACT FROM AUTHOR]

This paper presents a specific architecture for a low-side/high-side gate driver implementation for power devices running at high switching frequencies and under very high switching speeds. An electromagnetic interference (EMI) optimization is done by modifying the parasitic capacitance of the propagation paths between the power and the control sides, thanks to a specific design of the circuit. Moreover, to reduce the parasitic inductances and to minimize the antenna phenomenon, the paper studies which elements of the drivers’ circuitry must be brought as close as possible to the power parts. This is important when the ambient temperature of the power device becomes critical, for instance, in automotive and aeronautic applications. Simulations and experiments validate the advantages of the proposed architecture on the conducted EMI problem. [ABSTRACT FROM AUTHOR]

This paper presents, initially, a systematic derivation of extended first harmonic approximation (FHA) analysis and, later, a comprehensive time-domain (T-D) analysis to study series–series compensated inductive power transfer (IPT) systems with a diode bridge rectifier. Further, the paper shows that both FHA and T-D methods predict four mutually exclusive and collectively exhaustive modes of operation. Explicit criteria for each operation mode and formulae for mode boundaries are derived and it is concluded that FHA can explain three of four modes. The proposed T-D analysis is capable of describing the quantitative behavior of the system in all four operation modes with closed-form equations for all the mode boundaries. This analysis provides an objective basis to assess the accuracy of FHA predictions under the entire operating conditions. Quantitative comparison of key variables revealed that the FHA results can be unacceptably inaccurate for certain operating points. It is shown that the T-D approach provides a comprehensive design base for series–series compensated IPT without a need to know the load value. The T-D predictions are validated by experiment. A mathematical design calculator tool is also provided to the reader to visualize the mode boundaries, all the waveforms and the numerical results from both methods. [ABSTRACT FROM AUTHOR]

In order to construct a low-impedance loop for common-mode electromagnetic interference (EMI) signals, traditional method is to use Y-capacitors as filtering components. However, in the commonly used isolated ac–dc switching-mode power supplies (SMPS), the Y-capacitors branch also behaves as a terrible leakage current loop. For the safety of human beings, this leakage current is not allowed in commercial used equipment, such as chargers, medical instruments, etc. Therefore, certain works should be done to both acquire good EMI performance and satisfy the strict leakage current limitation. The goal of this paper is try to meet these two demands at the same time. In this paper, a novel non-Y-capacitor EMI design concept for SMPS is proposed for the first time. By getting rid of traditional EMI filtering component—the Y-capacitors, the leakage current can be eliminated entirely. Meanwhile, to face with EMI design challenge, optimized transformer architecture is presented. Analysis of the transformer architecture as well as the auxiliary winding has been carried out. Then, a novel topology suitable for non-Y-capacitors converter is proposed and the design procedure of the proposed topology is discussed in detail. The proposed concept is applied to several popular converter topologies. The experiment results demonstrated the effectiveness and feasibility of the proposed non-Y-capacitor design schemes. [ABSTRACT FROM AUTHOR]

This paper proposes a transformerless bipolar multistring dc–dc converter based on series-connected submodules. It is intended for converting dc voltage and managing power flow for medium-voltage high-power dc networks. This new converter has a flexible structure of multistrings and each string consists of four valves with their middle points crossly connected through two cost-effect dc capacitors to form power balancing channels between valves. Its transformerless solution and single-stage configuration greatly reduce the converter volume, weight, cost, and power loss. In this paper, voltage ratio range and its influence on submodule design are analyzed. Moreover, a control strategy with focus on current sharing control and submodule capacitor voltage control is proposed. A simulation model rated at ±10 kV 2 MW verifies the feasibility of the proposed dc–dc converter. Experimental results obtained from a 100-V 1.5-kW laboratory setup also confirm the validation of the proposal. [ABSTRACT FROM PUBLISHER]

An important issue in the photovoltaic (PV) power generation systems is the massive amount of heat wasted by PV modules/panels. For the first time, this paper provides a new solution to recover a portion of the mentioned waste heat by utilizing a proposed electrochemical heat engine. A thermally regenerative electrochemical cycle (TREC) system has been designed, constructed, and embedded in a PV power generation system including a 200-W PV module to harvest the waste heat of its PV module, so a PV-TREC hybrid system has been organized and built. The hot cell of the TREC system has been positioned in direct contact with the backside of the PV module, and the cold cell is in direct contact with a heat sink located in the shade of the PV module. Experimental verifications demonstrate that the proposed TREC system efficiently converts the waste heat into electric power ranging from 0.1 to 54.5 W. In this manner, up to 6% of the waste heat of the PV module is recovered. It also substantiated that the daily energy efficiency of the PV-TREC hybrid system is improved by 27.5% compared to a usual PV system, and this is the main contribution and novelty of this paper. [ABSTRACT FROM AUTHOR]

This paper proposes a fault-tolerant control strategy of the open-winding inverter for dc-biased vernier reluctance machines (dc-biased VRMs), aiming to maintain the output capability after the open-circuit fault occurs in the inverter switches. DC-biased VRMs are with integrated winding current for both dc component for field excitation and ac component for torque generation. The torque generation is not associated with the current direction, making the full-bridge inverter be divided into two groups of devices. The proposed fault-tolerant control strategy is based on the regular full-bridge inverter for each open winding and can control the motor in the fault-tolerant mode with one group of devices. When an open-circuit fault of a device appears in the normal mode, the controller will switch to the fault-tolerant mode. After a short transient period, the motor will be able to work. Moreover, in the fault-tolerant mode, a pulsewidth modulation driving method is proposed to reduce the current ripple. The proposed method does not require any additional components, and the reliability of the drive control system with the open-winding inverter is improved. Experimental results verify the validity and feasibility of the proposed fault-tolerant control strategy. [ABSTRACT FROM AUTHOR]

Parallel-form switch-linear hybrid (SLH) envelope tracking (ET) power supply is constituted by a linear amplifier and a switched-mode converter connected in parallel. The switched-mode converter is usually implemented by a buck converter with hysteresis current control. However, the slew rates of the load current and the inductor current of the buck converter cannot match well when the slew rate of the load current has a wide variation range. The unmatched slew rates will lead to a high switching frequency of the buck converter or a large loss of the linear amplifier, which degrades the overall efficiency. In this paper, a multilevel converter is adopted to replace the buck converter in the parallel-form SLH ET power supply, and the hysteresis current control scheme is proposed for the multilevel converter to dynamically adjust its inductor current slew rate to approach that of the load current to improve the overall efficiency. The optimal design for the efficiency-related parameters including the inductor, the current hysteresis, and the number and values of the voltage levels in the multilevel converter is given. A prototype of the parallel-form SLH ET power supply with hysteresis current controlled multilevel converter is fabricated and tested in the lab. The measured overall efficiency is 79.4% when tracking the envelope of wideband code division multiple access signal with 5 MHz bandwidth and outputs 18 W average power, and a 3.8% efficiency improvement is achieved over that with the hysteresis current controlled buck converter. [ABSTRACT FROM AUTHOR]

With the increasing renewable energy injected into the electrical distribution grid, the reliability of the power converter is gaining importance for the power system. In order to address the wear-out caused failure mechanisms of power semiconductors and thereby increasing the reliability, this paper aims at balancing the thermal stress caused during operation between different power converters in a wind park. An active thermal control strategy based on the discontinuous pulsewidth modulation is proposed for reducing the thermal stress of the semiconductors under a fluctuating power profile, while maintaining good power quality. The proposed method is introduced for multiple converters, which are connected to the same grid feeder and its impact on the lifetime of the semiconductors is investigated analytically. Finally, the effectiveness of the proposed method is experimentally validated for a two-level voltage source converter. [ABSTRACT FROM AUTHOR]

In a low-voltage parallel inverter system, the active power, unbalanced power, and harmonic power generally cannot be properly shared among inverters with droop control due to the mismatch of output impedance. To address this issue, this paper proposes a two-stage adaptive virtual resistor (AVR) control scheme. In the first stage, a proportional-integral controller is applied to regulate the active power with the use of a synchronous maximum power bus (SMPB), and the reactive power is adjusted by means of aQ–ωdroop controller. In the second stage, all inverters switch to aP–Edroop control mode by introducing the AVRs at fundamental positive-sequence, negative-sequence, and harmonic frequencies. Not only can this method eliminate the active power, unbalanced power, and harmonic power-sharing errors, it can also reduce the voltage deviation caused by the droop control. Moreover, the synchronization between inverters can be guaranteed as long as the SMPB is present, without using voltage sensors at the point of common coupling. Simulation and experimental results are provided to verify the feasibility of this method. [ABSTRACT FROM AUTHOR]

Multiple coupled inductors are used in power electronics to improve the dynamic cross regulation and to reduce mass and volume, mainly in high performance application, such as space or defense, where manufacturing cost is not the main driver. These elements can be modeled with its inductance matrix which is a symmetric and positive semidefinite matrix. The inductance matrix eases circuit analysis, many known circuital models are directly related to it and it can be used in SPICE simulation via its coupling coefficient component, which can be identified as the normalized matrix of the inductance matrix. Therefore, a precise and correct measurement technique of the inductance matrix or coupling coefficient matrix is needed. This paper analyzes different measuring techniques described in the technical literature and proposes a new method to measure the coupling coefficient or inductance matrix of tight coupled or dissimilar turns’ number windings, where other methods fail. A discussion follows, to know the influence of parasitic elements in the accuracy of the new proposed method called resonance (RE) method. The paper adds three experimental examples to verify the theoretical study and concludes that the RE method provides correct values of the coupling coefficient $k$ of tight coupled or dissimilar turns’ number windings compared to other measurement techniques. [ABSTRACT FROM AUTHOR]

This paper addresses a bidirectional dc-dc converter suitable for an energy storage system with an additional function of galvanic isolation. An energy storage device such as an electric double layer capacitor is directly connected to a dc side of the dc-dc converter without any chopper circuit. Nevertheless, the dc-dc con- verter can continue operating when the voltage across the energy storage device drops along with its discharge. Theoretical calculation and experimental measurement reveal that power loss and peak current impose limitations on a permissible dc-voltage range. This information may be useful in design of the dc-dc converter. Experimental results verify proper charging and discharging operation obtained from a 200-V, 2.6-kJ laboratory model of the energy storage system. Moreover, the dc-dc converter can charge the capacitor bank from zero to the rated voltage without any external precharging circuit. [ABSTRACT FROM AUTHOR]

This paper investigates the experimental implementation and detection of rotor faults in permanent magnet synchronous machines. Methods are shown how to experimentally introduce static and dynamic eccentricities and broken magnet cases. A new magnet flux estimation that does not require the measurement of the rotor position or speed is developed. The detection of these and other rotor faults by measuring only the stator currents and voltages are shown experimentally. The paper concludes by contributing a description of a condition-monitoring scheme for detection rotor faults. [ABSTRACT FROM AUTHOR]

Stability analysis of average value models (AVMs) of vector-controlled modular multilevel converters (MMCs) is the subject matter of this paper. Stability analysis of fundamental frequency phasor-based AVMs of MMCs can be conducted in a traditional linear time-invariant framework through eigenvalue computation. This class of models does not consider circulating current control loop and hence fails to capture system instability that occurs in a certain range of gains of the circulating current controller. We propose stability analysis in a linear time-periodic (LTP) framework to solve this issue. To that end, a nonlinear AVM is presented that considers the submodule capacitor insertion dynamics and takes into account the output and the circulating current control schemes in the vector control approach. Upon linearization, an LTP model is derived from this averaged model. It is shown that the Poincar \acutee multipliers are indicative of system instability corresponding to a certain range of gains of the circulating current controller. [ABSTRACT FROM AUTHOR]

This paper demonstrates the functionality of a power-electronics-based energy management system (EMS). The EMS includes batteries and a digitally controlled single-phase voltage source inverter (VSI), which can be controlled as a current source or a voltage source depending on the status of the ac grid and the user's preference. The EMS guarantees that the critical loads are powered when the ac grid fails; in which case, the VSI is controlled as a voltage source. It also accomplishes peak power control by supplying battery power to the local loads while they are powered by the ac grid if the loads get large. The electricity cost savings accomplished by peak shaving are estimated. The EMS functionality is demonstrated by experimental measurements on a laboratory prototype. The control architecture and logic embedded in the EMS are discussed in detail. [ABSTRACT FROM AUTHOR]

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

This paper analyzes the small-signal impedance of three-phase grid-tied inverters with feedback control and phase-locked loop (PLL) in the synchronous reference (d-q) frame. The result unveils an interesting and important feature of three-phase grid-tied inverters – namely, that its q–q channel impedance behaves as a negative incremental resistor. Moreover, this paper shows that this behavior is a consequence of grid synchronization, where the bandwidth of the PLL determines the frequency range of the resistor behavior, and the power rating of the inverter determines the magnitude of the resistor. Advanced PLL, current, and power control strategies do not change this feature. An example shows that under weak grid conditions, a change of the PLL bandwidth could lead the inverter system to unstable conditions as a result of this behavior. Harmonic resonance and instability issues can be analyzed using the proposed impedance model. Simulation and experimental measurements verify the analysis. [ABSTRACT FROM PUBLISHER]

This paper describes the design of a robust high-voltage solid-state pulsed power modulator (SSPPM), which requires reliable series stacking and driving of a number of semiconductor switches. For voltage balancing against overvoltage during both at transient and at steady-state, the power-cell-based modular stacking structure consists of an energy storage capacitor, bypass diode, and switching device (such as an insulated-gate bipolar transistor or a metal-oxide-semiconductor field-effect transistor (MOSFET)). In addition to the reliable voltage balancing of each switching device, the modular power cell stacking structure provides a fault-tolerant design by allowing individual protection circuit for each switching device. In this paper, the inclusion of a compensating third winding is proposed. This compensating third winding solves the voltage unbalance issue, which results from difference of leakage inductance of separate located transformer core, using magnetic flux compensation. A protection method using this compensating winding is also suggested to detect abnormal occurrences in each power cell under operating conditions. Additionally, an arc current protection circuit to ensure continuous operation of the SSPPM is designed. Through simulation and experimental results of tests on the SSPPM with the structure outlined earlier, it is verified that the proposed design can be used effectively, as it exhibits both robustness and reliability. [ABSTRACT FROM AUTHOR]

Multifunctional grid-tied inverters (MFGTIs) have been paid much attention to handle the commonly concerned power quality issues of the microgrids. An MFGTI can not only interface the renewable energy resource into the utility grid, but also can compensate the harmonic and reactive current in the microgrid as an auxiliary service. However, the apparent capacity of an MFGTI for power quality compensation is limited. Therefore, how to enhance the power quality of the microgrid by optimal utilization of the limited and valuable capacity becomes a technical challenge. In this paper, two optimal control objectives of MFGTIs are presented based on a comprehensive power quality evaluation algorithm by means of analytic hierarchy process theory. One objective aims to obtain the expected power quality using minimal apparent capacity of the MFGTI. Another objective focuses on enhancing the power quality as well as possible in the given available apparent capacity condition. The two proposed strategies are compared in performance, and the paper also discusses how to use them in practice for the best performance. Experimental results performed on a microgrid in the laboratory confirm the validation and feasibility of the proposed optimal control strategies. [ABSTRACT FROM AUTHOR]

In this paper, a three-phase boost-inverter topology is used to condition a typical low output voltage fuel cell (FC) as a stand-alone power supply. The key benefits of the proposed power supply include ability to deliver both the boosting and inversion functions in a single stage, compactness, and low cost. Additionally, the power supply incorporates a battery storage unit through a bidirectional converter to support the slow dynamics of the FC and simultaneously protect the FC as it acts as a filter for the low-frequency harmonics. The three-phase output voltage of the boost-inverter is voltage-mode controlled and the battery unit is current-mode controlled. Analysis, simulation, and experimental results taken from a 1-kW laboratory prototype three-phase boost-inverter operating at 20 kHz and bidirectional converter with two 12 V-24 Ah lead acid batteries are presented to confirm the operational performance of the proposed power supply. [ABSTRACT FROM AUTHOR]

This paper proposes a supercapacitor-based energy recovery system (ERS) with improved power control and energy management (PC&EM) capability for elevator applications. The ERS is connected to the dc link of the elevator motor drive through a bidirectional dc–dc converter for storing and then recovering the braking energy. The proposed PC&EM technique provides improved cost effectiveness and exploitation of the ERS capability, by adjusting the elevator power requirements with the ERS power capability through cabin speed regulation within predefined limits. The proposed control system can be easily installed without requiring modifications in the elevator motor drive, and thus, it can be easily applied to any existing elevator applications. Also, an experimental procedure is proposed in order to online determine and periodically fine-tune the parameters of the suggested PC&EM controller. In this paper, the proposed control technique has been applied in an ERS with a nonisolated dc–dc converter; however, it can as well be used in the isolated counterpart. Selective experimental results are presented in order to verify the effectiveness of the proposed control technique and demonstrate the resulting operational improvements. [ABSTRACT FROM PUBLISHER]

In this paper, a cost-effective architecture based on Flyback topology is proposed for both constant current (CC) output for LED drive and constant voltage (CV) output for auxiliary (AUX) supply. A novel nonlinear ramp-based control scheme is proposed to decouple the main CC power train from the CV AUX supply and avoid LED output flickering. Small signal modeling is presented to highlight the advantages of this control scheme over conventional peak current mode control. This scheme has been implemented successfully for a 40-W dimmable LED driver with a 12-V 3-W AUX supply. [ABSTRACT FROM AUTHOR]

The three-phase synchronous reference frame phase-locked loop (3\phi-SRF-PLL) is widely used in three-phase power electronics and power system applications thanks to its desirable performance and its simple yet robust structure. Inspired from the 3\phi-SRF-PLL and due to the increasing interest in single-phase applications, multiple single-phase SRF-PLL (1\phi-SRF-PLL) versions have also been proposed in the recent years. This paper presents a unifying approach to the understanding and analysis of the 1 \phi-SRF-PLLs. This paper integrates several 1 \phi-SRF-PLLs having apparently different structures into a single structure. The approach is much useful in understanding various PLLs and also in facilitating further developments in this field. [ABSTRACT FROM AUTHOR]

Induction heating (IH) has become the technology of choice in many industrial, domestic, and medical applications due to its high efficiency and performance. This paper proposes an interleaved resonant boost inverter featuring SiC three-phase module to achieve high efficiency and performance IH power supply. The proposed converter achieves high efficiency by reducing the current through the devices, while the use of an interleaved full-bridge configuration reduces input current ripple and provides additional control degrees. The proposed converter has been designed, implemented, and tested experimentally, proving the feasibility of this proposal. [ABSTRACT FROM PUBLISHER]

This paper presents a topology for bidirectional solid-state transformers with a minimal device count. The topology, referenced as dynamic-current or Dyna-C, has two current-source inverter stages with a high-frequency galvanic isolation, requiring 12 switches for four-quadrant three-phase ac/ac power conversion. The topology has voltage step-up/down capability, and the input and output can have arbitrary power factors and frequencies. Further, the Dyna-C can be configured as isolated power converters for single- or multiterminal dc, and single- or multiphase ac systems. The modular nature of the Dyna-C lends itself to be connected in series and/or parallel for high-voltage high-power applications. The proposed converter topology can find a broad range of applications such as isolated battery chargers, uninterruptible power supplies, renewable energy integration, smart grid, and power conversion for space-critical applications including aviation, locomotives, and ships. This paper outlines various configurations of the Dyna-C, as well as the relative operation and controls. The converter functionality is validated through simulations and experimental measurements of a 50-kVA prototype. [ABSTRACT FROM PUBLISHER]

This paper presents power and frequency tuning loops based on fundamental harmonic operation (FHO) and third harmonic operation (THO) for inductive power transfer (IPT) systems. THO is an effective solution for applications requiring high-frequency power supply with low voltage gains, e.g., low-voltage contactless battery chargers. Moreover, it can reduce the switching losses and increase the net efficiency of IPT systems in light-load conditions. Compared to conventional methods, such as phase-locked-loop (PLL) circuits, the proposed methods are less affected by misalignments and instantly track the resonant frequency. Hence, they can be utilized in self-switched capacitor and variable coupling applications. In addition, the new tuning systems can switch between THO and FHO modes for different loadings, voltage gains, and couplings conditions, e.g., dynamic powering of different moving pickups. To show the performance of the new tuning loops, laboratory prototypes with switching frequency of 20–50 kHz are implemented based on half-bridge and full-bridge inverters. [ABSTRACT FROM AUTHOR]

A synchronous rectification buck converter in parallel with a Class AB linear amplifier is presented in this paper to construct an envelope-tracking (ET) power supply. To eliminate the influences of the output voltage on the linear amplifier output current, a full feedforward of the output-voltage scheme with two feedforward terms is proposed in this paper, which can counteract all the two load admittances of the linear amplifier, respectively, consequently decreasing the linear amplifier output current substantially. An ET power supply prototype with 100-kHz sine-wave tracking, 5-15 V output voltage, and 75-W-peak output power is fabricated and tested in the lab. The experimental results are well in agreement with the theoretical analyses, and the system efficiency is improved significantly. [ABSTRACT FROM AUTHOR]

The layout of power modules is one of the key points in power module design, especially for high power densities, where couplings are increased. In this paper, along with the design example, automatic design processes by using a genetic algorithm are presented. Some practical considerations and implementations are introduced in the optimization of module layout design. [ABSTRACT FROM AUTHOR]

The two-switch cascade converter is the most appropriate solution for efficient high-power applications among the existing converter topologies. However, the cascade structure and the nonlinear dc gain of boost circuit are more likely to cause severe oscillations if the criterion for the selection of the operation mode is chosen improperly during step-up/step-down transition. A novel high-power input-parallel output-series buck-half-bridge (IPOSBHB) converter is proposed in this paper. The circuit structure, operating principles, and basic relations are analyzed. Comparisons between IPOSBHB and two-switch cascade converter are also elaborated on with respect to voltage and current stress, total volume of magnetic components, and efficiency. In addition, the inconformity of the transfer functions, the discontinuity caused by the switching time delay, and the disturbance of input voltage are analyzed. Methods for compensation are also proposed. The proposed converter can achieve satisfactory comprehensive performance when the step-up ratio is low. The combinational control strategy and the compensation methods proposed in this paper are easy to carry out in order to achieve effective control at steady state, smooth transition at mode change, and reduction of the adverse effect caused by the disturbance of input voltage. A 15-kW prototype is used to validate the proposed theory. [ABSTRACT FROM AUTHOR]

A new analytical switching loss model for power MOSFETs driven by the current source driver (CSD) is presented in this paper. The gate current diversion problem, which commonly exists in existing CSDs, is analyzed mathematically. In addition, a new accurate switching loss model considering every switching interval piecewisely is proposed. Based on the proposed loss model, the optimal design of the CSD inductor is achieved to minimize the total power loss for the buck converter. The experimental result verifies the proposed switching loss model and optimal design. The measured loss matches the calculated loss very well; the error between the calculated loss and measured one is less than 10% from 5 A load to 30 A load with 12 V input and 1.3 V output. As compared with the previous study, the efficiency with the optimal CSD inductor is improved from 86.1% to 87.6% at 12 V input and 1.3 V/20 A output and from 82.4% to 84.0% at 12 V input and 1.3 V/30 A output at 1 MHz switching frequency. As compared with the commercial driver-MOSFETs from Renesas and International Rectifier, the buck converter with the optimal CSD still shows better performance. [ABSTRACT FROM AUTHOR]

This paper introduces a novel hybrid seven-level converter that is based on the upgrade of the five-level active neutral-point-clamped converter concept and is suitable for high-power applications. The paper provides a comprehensive analysis for the operation of the converter. Based on the analysis, a space vector modulation (SVM)-based switching strategy that takes advantage of redundant switching vectors of the SVM strategy to counteract the voltage drift phenomenon of the proposed converter is proposed. The limit to the range of operation of the seven-level converter based on the proposed SVM strategy is also presented. It is shown that the ability to stabilize the dc-link capacitor voltages and the per-phase flying capacitors is a function of the converter operating indices, i.e., the load power factor and modulation index. The salient feature of the proposed SVM-based control strategy is that it enables proper operation of the converter with no requirements for additional controls or auxiliary power circuitry, within the specified range of operation. Performance of a converter under various operating conditions, based on the proposed SVM strategy, in the MATLAB/Simulink environment, is evaluated and experimentally demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for the optimal allocation and economic analysis of energy storage system (ESS) in microgrids (MGs) on the basis of net present value (NPV). As the performance of an MG strongly depends on the allocation and arrangement of its ESS, optimal allocation methods and economic operation strategies of the ESS devices are required for the MG. To optimize the operation strategies and capacities of ESS in MGs, the financial benefit and dynamic models of ESS are discussed. And then, a matrix real-coded genetic algorithm is applied to find maximal NPV, in which each GA chromosome consists of a 2-D real number matrix representing the generation schedule of ESS and distributed generation sources. This paper is to suggest, among those available ESS, the optimal sizes and types of them and their optimal arrangement, such that the total NPV achieved during the system operational lifetime period is maximized. Finally, some computational simulation results are presented to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper introduces a new concept of optimal utilization of a unified power quality conditioner (UPQC). The series inverter of UPQC is controlled to perform simultaneous 1) voltage sag/swell compensation and 2) load reactive power sharing with the shunt inverter. The active power control approach is used to compensate voltage sag/swell and is integrated with theory of power angle control (PAC) of UPQC to coordinate the load reactive power between the two inverters. Since the series inverter simultaneously delivers active and reactive powers, this concept is named as UPQC-S (S for complex power). A detailed mathematical analysis, to extend the PAC approach for UPQC-S, is presented in this paper. MATLAB/SIMULINK-based simulation results are discussed to support the developed concept. Finally, the proposed concept is validated with a digital signal processor-based experimental study. [ABSTRACT FROM AUTHOR]

In this paper, an oscillation compensation technique is proposed to improve the stability margin of an electrical system constituted by a dc power supply, an LC filter, and a constant power load. This is realized here by an actuator (inverter-permanentmagnet synchronous motor). To design the compensator, input impedance of the constant power load and output impedance of the filter are required and derived in this paper. To develop the load input impedance expression, small signal approximation is employed and all dynamics are taken into account except by the inverter ones only, which can often be neglected in practical applications. Then, the control structure of the whole system is slightly modified to implement the oscillation compensation block that increases the stabilitymargin, and thus, permits to reduce the dc-link capacitance value. In this paper, the proposed method is applied to an actuator designed for aerospace applications. The influence of the actuator control parameters and the input filter parameters on the stability of the dc-link voltage is discussed. Simulations and experimentations confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents an original implementation of a technique in ac-to-ac power converters to power the gate drivers of power transistors. AC to ac converters are well known for the complexity of their implementation due to the large number of power transistors required, many of which have different potential references. This requires a consequent number of insulated gate drivers and corresponding power supplies. Besides, MOS-MOS switching transitions (characterized by switching transitions among transistors without the introduction of freewheeling diode conduction time), typical of these converters, are complex to manage and often lead to voltage or current overshoots. The gate driver powering technique presented in this paper simplifies the global implementation of the converter as well as the management of MOS-MOS switching transitions. The proposed technique harvests energy from the power side, when this energy is available, in order to redistribute this energy to the transistor drivers. This original self-powering technique significantly simplifies the implementation of the transistor since it can be integrated within the power switch to be controlled. The immediate benefit is a reduced number of elements to be implemented, thus providing a costeffective solution. As an additional benefit, the proposed technique simplifies the management of high-stress switching transitions. Indeed, the gate driver power supplies are designed to be sensitive to positive dv/dt, a feature that allows self-powering during the dead time of switching transitions. This leads to a reduction in both dead time duration and voltage overshoots, as validated by a practical implementation. [ABSTRACT FROM AUTHOR]

Two improved torque-sharing functions for implementing torque ripple minimization (TRM) control are presented in this paper. The proposed torque-sharing functions are dependent on the turn-on angle, overlap angle, and the expected torque. This study shows that for a given torque the turn-on angle and the overlap angle have significant effects upon speed range, maximum speed, copper loss, and efficiency. Hence, genetic algorithm is used to optimize the turn-on angle and the overlap angle at various expected torque demands operating under the proposed TRM control in order to maximize the speed range and minimize the copper loss. Furthermore, four torque-sharing functions are used to derive the optimized results. At the same time, a fast and accurate online approach to compute the optimal turn-on and overlap angles is proposed. Therefore, this paper provides a valuable method to improve the performances of switched reluctance motor drives operating under TRM control. [ABSTRACT FROM AUTHOR]

Voltage sags are the leading cause of unscheduled downtime in industrial plants with high levels of automation. Zero-energy sag correctors (ZESCs) that utilize energy from those phases that have sufficient remaining voltage on them promise levels of protection that are comparable with conventional energy storage based sag correctors, but in a more compact package. This paper presents a ZESC topology with reduced device count using readily available device packages that can realize similar performance as the original ZESC circuit. The proposed ZESC behaves like a "thin ac converter," and can be integrated with existing assets such as transformers and switchgears. This paper presents details of the operation, design, and experimental results for such a ZESC circuit. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose a general approach for developing multi-input converters (MICs). The derived MICs can deliver power from all of the input sources to the load either individually or simultaneously. By analyzing the topologies of the six basic pulsewidth modulation (PWM) converters, the method for synthesizing an MIC is inspired by adding an extra pulsating voltage or current source to a PWM converter with appropriate connection. As a result, the pulsating voltage source cells (PVSCs) and the pulsating current source cells (PCSCs) are proposed for deriving MICs. According to the presented synthesizing rules, two families of MICs, including quasi-MICs and duplicated MICs, are generated by introducing the PVSCs and the PCSCs into the six basic PWM converters. [ABSTRACT FROM AUTHOR]

This paper presents a cascaded H-bridge multilevel inverter that can be implemented using only a single dc power source and capacitors. Standard cascaded multilevel inverters require n dc sources for 2n + 1 levels. Without requiring transformers, the scheme proposed here allows the use of a single dc power source (e.g., a battery or a fuel cell stack) with the remaining n - 1 dc sources being capacitors, which is referred to as hybrid cascaded H-bridge multilevel inverter (HCMLI) in this paper. It is shown that the inverter can simultaneously maintain the dc voltage level of the capacitors and choose a fundamental frequency switching pattern to produce a nearly sinusoidal output. HCMLI using only a single dc source for each phase is promising for high-power motor drive applications as it significantly decreases the number of required dc power supplies, provides high-quality output power due to its high number of output levels, and results in high conversion efficiency and low thermal stress as it uses a fundamental frequency switching scheme. This paper mainly discusses control of seven-level HCMLI with fundamental frequency switching control and how its modulation index range can be extended using triplen harmonic compensation. [ABSTRACT FROM AUTHOR]

This paper sets forth and demonstrates an approach to the design of power electronics based power systems using evolutionary computing techniques. Key features of the paper are the use of evolutionary computing in the context of classical control design, construction of appropriate multievent based performance metrics, and the use of multiobjective evolutionary computing in the selection of control parameters based on system performance versus control effort. The proposed approach is demonstrated in a power electronics based power distribution system similar to those being designed for next generation warships. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis and simulation of the static series compensator (SSSC) for subsynchronous resonance (SSR) mitigation. The purpose of the paper is to derive and analyze a novel control strategy for SSSC dedicated for SSR mitigation. Objective of the proposed controller is to increase the network damping only at those frequencies that are critical for the turbine-generator shaft. By using frequency scanning analysis, the effectiveness of the proposed method for mitigation of SSR due to torsional interaction effect is presented and compared with the existing control strategy. Finally, simulation results show the performance of the proposed method in mitigating SSR due to torque amplification effect. [ABSTRACT FROM AUTHOR]

The dynamic voltage restorer (DVR) as a means of series compensation for mitigating the effect of voltage sags has become established as a preferred approach for improving power quality at sensitive load locations. Meanwhile, the cascaded multilevel type of power converter topology has also become a workhorse topology in high power applications. This paper presents the detailed design of a closed loop regulator to maintain the load voltage within acceptable levels in a DVR using transformer coupled H-bridge converters. The paper presents system operation and controller design approaches, verified using computer simulations, and a laboratory scale experimental prototype. [ABSTRACT FROM AUTHOR]

An accurate analytical model is proposed in this paper to calculate the power loss of a metal-oxide semiconductor field-effect transistor. The nonlinearity of the capacitors of the devices and the parasitic inductance in the circuit, such as the source inductor shared by the power stage and driver loop, the drain inductor, etc., are considered in the model. In addition, the ringing is always observed in the switching power supply, which is ignored in the traditional loss model. In this paper, the ringing loss is analyzed in a simple way with a clear physical meaning. Based on this model, the circuit power loss could be accurately predicted. Experimental results are provided to verify the model. The simulation results match the experimental results very well, even at 2-MHz switching frequency. [ABSTRACT FROM AUTHOR]