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This paper discusses a novel methodology to increase the voltage droop compensation range in generalized solid-state bipolar high-voltage Marx modulators with one resonant stage. To maintain the modularity characteristic of bipolar Marx modulators, the imbedding of additional resonant stages is not straightforward. Nevertheless, this paper proposes to add a second resonant stage to the already existing resonant-type voltage droop compensation stage. This second stage increases the voltage droop compensation percentage of a generalized solid-state bipolar Marx generator. The compensation of the bipolar pulse voltage droop is now achieved by adding two auxiliary synchronous compensation resonant voltages, to the output capacitive decaying voltage. Simulation and experimental results are presented for six Marx plus two resonant stages, 16% voltage droop, with 3-kV pulse amplitude, 100- $\mu \text{s}$ pulsewidth, 40-ms relaxation time, and 10-Hz pulse repetition rate. [ABSTRACT FROM AUTHOR]

This paper presents the design and construction of a sample of Marx pulsed generator based on boost converter (BC) pulse-forming networks (BCPFNs). BCPFN is used instead of the conventional Marx floors for constructing this pulsed generator. BCPFN is carried out by connecting inductors and capacitors in series and parallel modes, respectively, by using solid-state switches, and during this procedure the pulsed generator converts to BC temporarily and increases the voltage of capacitors uniformly to a considerable value. This technique causes an increase in the discharging voltage level to the load that is many times more than its dc voltage source by charging the capacitors to a greater level. In order to take advantage of the benefits of Marx generator and PFN, this paper suggests a new circuit with the minimum number of switches. It means, to compose BCPFN and Marx, we have tried to design the circuit with fewer switches and instead of it we have achieved our desired performance with changing the operating mode in the states of BC, PFN, BCPFN, and BCPFN Marx. The results are simulated with MATLAB software. At the end, the experimental results of the construction of the above-mentioned system at low-power levels are presented, and the topology’s accuracy is proved by comparing them to the results of simulation. [ABSTRACT FROM AUTHOR]

Vibration measurement has been adopted in some utilities in Australia, Canada, and several European countries for online condition monitoring of the power transformer's onload tap changer (OLTC). By comparing measured vibration signals at different stages, it might be possible to assess changes of OLTC's condition. However, there are still considerable difficulties in correlating vibration signals to the events of OLTC operation, which may impair the capability of vibration measurement for OLTC condition monitoring. Therefore, arcing measurement is proposed in this paper to complement the vibration measurement. Arcing is provoked when the OLTC switching contact closes at a fixed tap position and can lead to electromagnetic signals flowing through transformer windings, finally reaching earth. The arcing measurement is achieved by using a high-frequency current transducer (HFCT) clamping on the transformer's grounding cable. The joint vibration and arcing measurement can provide a better means for interpreting events involved in OLTC operation and facilitating improved OLTC condition monitoring. Since HFCT measured arcing signals can be coupled with noise, a probabilistic wavelet transform is thus employed in this paper to extract arcing signals from noise. Field measurements on two different types of OLTCs are performed using the joint vibration and arcing measurement system to validate the proposed methodology. [ABSTRACT FROM PUBLISHER]

This paper presents a novel interleaved high-conversion-ratio bidirectional dc–dc converter based on switched capacitors and coupled inductors. Series-connected switched capacitor and inductor cells were used to increase the voltage conversion ratio, reduce voltage stresses on power switches, realize soft-charging/discharging of switched capacitors, and achieve autocurrent-sharing in parallel inductors. The interleaved structure combined with switched capacitors was adopted to reduce current ripple at the side having lower voltage, thus enabling applications that require high power levels. In this paper, we first review the status of high-voltage-ratio bidirectional dc–dc converters. Then, the evolution of the proposed extensible topologies and the steady-state operating principle under the inductor current continuous conduction mode is presented. Finally, the performance and features such as voltage gain, voltage and current stress, and the autocurrent-sharing mechanism that are realized by switched capacitors are verified; the optimal design of coupled-inductors, switched-capacitors, and the chip size of switches are given. A specific design of the driving circuit that facilitates actual applications is described. A 1-kW prototype converter, employing a hybrid configuration of SiC and Si mosfets, was constructed to verify the theoretical analysis, and achieved an optimal compromise between conversion efficiency and low cost. [ABSTRACT FROM AUTHOR]

This paper presents a hierarchical Markov model to assess the reliability of a double-sided linear switched reluctance generator (DLSRG) system. The proposed reliability model can be applied to find the balance point of reliability assessment accuracy and model complexity. First, the dominant fault modes of the DLSRG system are highlighted to quantitatively obtain the operation states, survival or failure, with a novel failure criterion. Second, a hierarchical Markov model is adopted to build a systematic reliability model of the DLSRG system, wherein a state transition diagram can be built in the detailed description to constitute the graphical Markov reliability model. And then the solving process to get state probability matrix P(t) is intensively investigated. Notably, a reliability block diagram model is also built to compare with the hierarchical Markov model, whose results verify that the Markov model can capture the effect of fault-tolerance capability on system reliability. Moreover, it is expected that the one-level Markov model is the most suitable model for the DLSRG system for its ability of decreasing the model complexity and improving the assessment accuracy. Analytic investigation in conjunction with simulation and experimental measurements demonstrates the feasibility and validity of the proposed model. [ABSTRACT FROM AUTHOR]

Optimal power management of shipboard power system for failure mode (OPMSF) is a significant and challenging problem considering the safety of system and person. Many existing works focused on the transient-time recovery without consideration of the operating cost and the voyage plan. In this paper, the OPMSF problem is formulated considering the mid-time scheduling and the faults at bus and generator. Two-side adjustment methods including the load shedding and the reconfiguration are coordinated for reducing the fault effects. To address the formulated non-convex problem, the travel equality constraint and fractional energy efficiency operation indicator limitation are transformed into the convex forms. Then, considering the infeasibility scenario affected by faults, a further relaxation is adopted to formulate a new problem with feasibility guaranteed. Furthermore, a sufficient condition is derived to ensure that the new problem has the same optimal solution as the original one. Because of the mixed-integer nonlinear feature, an optimal management algorithm based on Benders decomposition (BD) is developed to solve the new one. Due to the slow convergence caused by the time-coupled constraints, a low-complexity near-optimal algorithm based on BD is proposed. The results verify the effectivity of the proposed methods and algorithms. [ABSTRACT FROM AUTHOR]

In this paper, a high-voltage unipolar pulse power generator is introduced for electroporation applications. Operating principle of the proposed structure is based on the buck–boost (BB) converter. The generator is comprised of parallel modules connected to the converter through an SCR and is supplied by a low-voltage dc source. Each module consists of an insulated gate bipolar transistor (IGBT), two diodes, and a capacitor. In fact, the proposed topology is a combination of the Marx generator and BB (MG-BB) converter. In comparison with other modular MG-BB structures, the proposed topology achieves interesting advantages including simpler structure, reduction of IGBTs voltage rating, and reducing number of components (inductors and switches). In order to clarify the features of the proposed structure, it has been compared with other unipolar MGs considering different aspects including the number of circuit components, number of required input supplies, amplitude of the output pulse, and the maximum voltage across switches and diodes. To validate the effectiveness of the structure, simulation and experimental results are presented. The results confirm that the proposed topology is capable of generating unipolar pulses with desirable amplitude and repetition frequency using a low-voltage dc supply. [ABSTRACT FROM AUTHOR]

Individual microgrids have proven their ability to provide uninterrupted power to critical end-use loads during severe events. Building on the performance of individual microgrids during extreme events, there has been an increasing interest in the operations of network microgrids. By networking microgrids during extreme events, it is possible to share resources, increase the duration for which they can operate islanded, improve efficiency, and increase the resiliency of critical end-use loads. While there are benefits to networking the operations of resiliency-based microgrids, the switching operations that they require introduce transients, which can result in a loss of dynamic stability. The issue of dynamic stability is especially acute in microgrids with high penetrations of inverter-connected generation, and correspondingly low system inertia. While the low inertia of these microgrids can be increased by over-sizing the rotating generators, the increased capital and operating costs can become a barrier to deployment. This paper will present a method of augmenting primary frequency controls to support the switching transients necessary for the operation of networked microgrids, without the need to over-size rotating machines. [ABSTRACT FROM AUTHOR]

This paper presents the development of a switched-reluctance machine (SRM) driven flywheel system, its charging/discharging controls, and performance evaluations. By properly setting and tuning the winding commutation instant, the same SRM can be operated as a motor and a generator in the SRM-driven flywheel system with satisfactory performances. Moreover, the hysteresis current controlled pulsewidth modulation scheme with hard freewheeling and the commutation angle dynamic shift controller are proposed to enhance the flywheel discharging generating performance. For interfacing the flywheel system to the dc microgrid, a half-bridge bidirectional dc–dc interface converter is developed. It is operated in a buck mode under flywheel charging and in a boost mode under flywheel discharging. The dynamic modeling and controller design are conducted to yield well-regulated dc output voltage under varying flywheel-driven switched-reluctance generator (SRG) speed. Finally, the measured results are given to verify the performances of the established flywheel and its interconnected operation to a wind SRG-based dc microgrid. [ABSTRACT FROM AUTHOR]

This paper presents a passivity-based control (PBC) scheme for the switched reluctance generator (SRG) in small-scale wind energy conversion systems for dc microgrid applications. The main objective is to stabilize the output voltage in case the system supplies constant power loads (CPLs) and operates with maximum power point tracking (MPPT). Stability improvement and dc-link ripple reduction in the presence of CPLs is achieved using system-level modeling of SRG-based dc microgrid through the Euler-Lagrange system (ELS) from the viewpoint of the machine physical structure. Compared with other control methods, the proposed MPPT method based on passivity-based speed controller employs the back electromotive force (EMF) in the generation process as a position-dependent voltage source to overcome the major challenge of SRG complicated uncertain dynamic model. To deal with the time-varying inductance and back EMF of SRG, an adaptation mechanism is incorporated in the proposed adaptive PBC and the control design is constructed by using the Lyapunov theorem where the closed-loop stability is ensured. The effectiveness of the proposed method in avoiding instability effects of SRG and CPL with voltage ripple reduction and precise wind turbine speed tracking is investigated with simulation results and validated with experimental by using a four-phase, 8/6 SRG drive system. [ABSTRACT FROM AUTHOR]

Microgrid formation is a potential solution in postdisaster electric grid recovery efforts. Recent works propose a distribution level microgrid formation model that applies to radial distribution systems characterized by directed power flows. However, with high renewable penetration levels in future power systems, the flows are expected to be undirected even in distribution grids. In this paper, we develop a model to deal with the restoration process of future power systems, embedding some of the characteristics these systems are likely to have. More specifically, our formulation can deal with radial and meshed topologies, and it requires little preprocessing of the input data. Additionally, we extend the model to allow for possible mobile and fixed distributed generation technologies and distributed energy resources, and explicitly include demand responsive loads with a minimum satisfiability constraint. Thus, this extended formulation can be used as an operation and a short term planning tool for the DG scenario-based location problem. We compare our extended formulation results to those obtained for the radial cases found in the literature. Also, we apply the proposed approach to other instances of the problem based on the IEEE 37-bus, 30-bus, and 118-bus systems. [ABSTRACT FROM PUBLISHER]

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

This paper presents as a new contribution a proposal to optimize the performance of a switched reluctance generator (SRG) in a variable wind energy conversion system. An approach based on the design of computational experiment is applied to determinate the optimal firing angles and the optimal dc link voltage that guarantee the best system behavior for each rotor speed. A third-order response surface model based on space-filling designs is applied to build a multiobjective function considering efficiency improvement and torque ripple reduction. An interior point method is applied to find the minimum of the surface, optimizing the process. Direct power control is used to obtain the maximum power as a function of the rotor speed, employing the optimal parameters. Hysteresis and single-pulse current control are applied for low- and high-speed operation, respectively. Simulation and experimental results have shown that the proposed approach returned a good compromise between SRG high efficiency and low torque ripple. Moreover, the presented technique reduces computational effort and provides a clear massive data simulation framework. [ABSTRACT FROM AUTHOR]

High-voltage (HV) pulses are used in electroporation to subject pulsed electric field (PEF) onto a sample under treatment. Pulse-waveform shape, voltage magnitude, pulse duration, and pulse repetition rate are the basic controllable variables required for particular PEF application. In practice, a custom-made pulse generator is dedicated for each PEF application with limited flexibility in changing these variables. In this paper, a universal pulse-waveform generator (UPG) is proposed, where the controller software algorithm can manipulate a basic generated multilevel pulse waveform to emulate many different PEF pulse waveforms. The commonly used PEF HV pulse waveforms can be generated as bipolar or monopolar with controllable pulse durations, repetition times, and voltage magnitudes. The UPG has the ability to generate multilevel pulses that have controllable $dv/dt$, which allows reduction of the electromagnetic interference generated by the converter. The UPG topology is based on half-bridge modular multilevel converter (HB-MMC) cells forming two transition arms in conjunction with two bistate arms, together creating an H-bridge. The HB-MMC cell capacitors provide a controllable energy source which charge from the dc input supply and discharge across the load, while the two bistate arms allow charging the HB-MMC cell capacitors. Hence, the UPG topology offers modularity, redundancy, and scalability. The HB-MMC individual cell capacitance is low and the cell voltages are balanced by employing the sorting and rotating algorithm used in conventional HB-MMC topologies for HV dc transmission applications. The viability of the proposed UPG converter is validated by MATLAB/Simulink simulation and scaled-down experimentation. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel automatic mode transition control strategy for multiple inverters to operate in grid-connected and standalone modes. When grid is available, these inverters feed power the grid by operating in current control mode. Upon grid failure, all inverters automatically shift to droop control mode for achieving proportional power sharing and shift back to current control mode when the grid becomes available. The synthesis of dual structure control algorithms of various inverters is achieved using novel state machines. These state machines are designed to facilitate smooth mode transition of the inverters. In this way, the control signals for mode transition are generated by state machines specific to each inverter. Unlike existing control methods, the proposed method neither requires communication-based supervisory control of inverters nor it requires dedicated storage facility for achieving smooth mode transition. The proposed control strategy is tested on a simulation model as well as an experimental prototype multi-inverter system. [ABSTRACT FROM PUBLISHER]

This paper describes a high-frequency pulsed-power generator for various industrial applications such as water treatment, food and medical apparatus for sterilization, or polluted gas treatment. The system is made of silicon-controlled rectifier as a main trigger switch, capacitors, two-stage magnetic pulse compression stages, and a linear transformer to generate a maximum of 120-kV, 5-kA pulse. The parameters obtained through the development are: output voltage: 120 kV (maximum), pulse repetition ration: 300 pulse per second, pulsewidth: 0.25~\mu \texts , and mean power: 30 kW. The designed pulsed-power generator is confirmed to be used effectively for many high-voltage pulsed-power applications related to environmental industry by simulation and experiments. [ABSTRACT FROM AUTHOR]

High-voltage (HV) pulses are used in pulsed electric field (PEF) applications to provide an effective electroporation process, a process in which harmful microorganisms are disinfected when subjected to a PEF. Depending on the PEF application, different HV pulse specifications are required such as the pulse-waveform shape, the voltage magnitude, the pulse duration, and the pulse repetition rate. In this paper, a generic pulse-waveform generator (GPG) is proposed, and the GPG topology is based on half-bridge modular multilevel converter (HB-MMC) cells. The GPG topology is formed of four identical arms of series-connected HB-MMC cells forming an H-bridge. Unlike the conventional HB-MMC-based converters in HVdc transmission, the GPG load power flow is not continuous which leads to smaller size cell capacitors utilization; hence, smaller footprint of the GPG is achieved. The GPG topology flexibility allows the controller software to generate a basic multilevel waveform which can be manipulated to generate the commonly used PEF pulse waveforms. Therefore, the proposed topology offers modularity, redundancy, and scalability. The viability of the proposed GPG converter is validated by MATLAB/Simulink simulation and experimentation. [ABSTRACT FROM PUBLISHER]

In this paper, a novel ac/dc converter is proposed for low-voltage and low-power ac rectification applications. The proposed converter manages the energy harvested from microscale electromagnetic generators (MEGs). It integrates the conventional boost and buck–boost topologies with a shared inductor, a bidirectional switch, and two split filtering capacitors. The boost and the buck–boost topologies function in the positive and negative half input cycles, respectively. The inductor is energized by being shorted with the input source through the mosfet channel without using the diodes. This enables active rectification of low-amplitude (below 0.7 V) ac voltages. Theoretical analysis, design considerations, and control method are detailed. A 40-mW circuit prototype, which converts a 0.4-V peak, 100-Hz ac voltage source to 3.3-V dc, is designed and tested to verify the proof of concept. [ABSTRACT FROM AUTHOR]

This paper presents a novel technique for the voltage droop compensation of long pulses in solid-state bipolar high-voltage Marx generators. Considering the modularity of Marx generators the compensation consists in adding one extra stage to perform as a pulsewidth modulation circuit. This stage voltage is added to the output positive or negative pulses, and an output LfCf filter is included to smooth the voltage pulse waveform. A five-stage laboratory prototype of this circuit has been assembled using 1200-V Insulated Gate Bipolar Transistors and diodes with 1000-V dc input voltage. The circuit was operated at 50-Hz bipolar pulse rate, giving 4-kV bipolar pulses, into a resistive load, with 100- \mu \texts pulsewidth and 9.5-ms relaxation time. The circuit was able to compensate 10% of bipolar pulse voltage droop. [ABSTRACT FROM PUBLISHER]

This paper proposes a switching angle controller (SAC) and an automatic generation controller (AGC) for the doubly-fed induction generator (DFIG) to control the frequency of DFIG-based wind power penetrated power systems. The concept of virtual rotor angle of the DFIG is defined. The virtual rotor angle is controlled by the SAC in a bang-bang manner such that the active power of the DFIG is regulated to provide frequency support to the external power grids. The output of the SAC is also used for the control of pitch angle to offer a short-term regulation of the mechanical power input to the DFIG, and the long-term control of the mechanical power input is achieved with the AGC. Small-signal analysis is undertaken to verify the effectiveness of the SAC and the AGC. Simulation studies are carried out in a two-machine power system and a modified Kundur four-machine two-area power system, respectively. The frequency support performance of DFIGs having different control configurations is investigated. Modal analysis is undertaken to evaluate the effect of the SAC and the AGC in providing additional damping to the rotor oscillation modes of the modified Kundur four-machine two-area power system. [ABSTRACT FROM AUTHOR]

The semicontrolled open-winding PMSG system has been widely investigated due to its simplified topology and easy control implementation. Nevertheless, compared with the conventional controllable converter structure, the current zero crossing phenomenon will last a longer time in the semicontrolled configuration, which is determined by the phase displacement between voltage and current. Since a long current zero crossing duration will lead to voltage pulse disturbance, serious electromagnetic interference, and output power fluctuation, it is necessary to reduce the zero crossing duration to improve the open-winding PMSG performance. This paper gives a detailed analysis on the zero crossing phenomenon of the semicontrolled open-winding PMSG system in the 3-D space vector modulation perspective. Meanwhile, a third harmonic injection method is suggested to reduce the zero crossing duration. It is also demonstrated that the torque and power pulsation are effectively improved, while the zero-sequence current amplitude does not increase. A proportional resonant controller is used to regulate the desired zero-sequence current. The proposed method is validated in a 1-kW semicontrolled open-winding PMSG experimental system with id = 0 control method. [ABSTRACT FROM AUTHOR]

A bipolar pulse has been proved to be more advanced in the treatment of tumor because of the elimination of muscle contractions and the effect for ablating nonuniform tissue. In this paper, a new type of modular bipolar pulsed-power generator based on Marx generator with double power charging is proposed. The concept of this generator is charging the two series of capacitors in parallel by two power sources, respectively, and then connecting the capacitors in series through solid-state switches with different control strategies. Utilizing a number of fast solid-state switches, the capacitors can be connected in series with different polarities, so that a positive or negative polarity pulse will be delivered to the load. The simulated models of this generator have been investigated in a PSPICE platform, and a laboratory prototype has been implemented in a laboratory. The simulation and test results verify the operation of the proposed topology in different switching modes. The development of this pulse generator can provide the hardware foundation for the research on biological effect without muscle contraction when the tumors are applied with bipolar pulse electric field. [ABSTRACT FROM AUTHOR]

In this paper, a class-D audio amplifier which combines the advantages of the phase-shifted carrier pulsewidth modulation (PWM) and the multiple-level carrier PWM is proposed with a dual-level dual-phase carrier (DLDPC) PWM. The proposed closed-loop amplifier includes a second-order integrator and a DLDPC triangular wave generator. Two sets of 180° out-of-phase triangular waves are used as carriers, and each set has its respective offset voltage level with nonoverlapping amplitude. By performing the double Fourier analysis, it can be found that the linearity can be enhanced and the distortion can be reduced with the proposed modulation. Experimental results show that the proposed fully differential DLDPC PWM class-D audio amplifier features a total harmonic distortion lower than 0.01% with an output voltage swing of $\pm$5 V. [ABSTRACT FROM PUBLISHER]

In recent years, there has been a growing interest in incorporating microgrids in electrical power networks. This is due to various advantages they present, particularly the possibility of working in either autonomous mode or grid connected, which makes them highly versatile structures for incorporating intermittent generation and energy storage. However, they pose safety issues in being able to support a local island in case of utility disconnection. Thus, in the event of an unintentional island situation, they should be able to detect the loss of mains and disconnect for self-protection and safety reasons. Most of the anti-islanding schemes are implemented within control of single generation devices, such as dc-ac inverters used with solar electric systems being incompatible with the concept of microgrids due to the variety and multiplicity of sources within the microgrid. In this paper, a passive islanding detection method based on the change of the 5th harmonic voltage magnitude at the point of common coupling between grid-connected and islanded modes of operation is presented. Hardware test results from the application of this approach to a laboratory scale microgrid are shown. The experimental results demonstrate the validity of the proposed method, in meeting the requirements of IEEE 1547 standards. [ABSTRACT FROM PUBLISHER]

This paper proposes an improved half-bridge inverter with wide-input-voltage capability for ozone-driven circuits. The study is motivated because the limited regulation of input voltage often affects the operation flexibility of ozone-driven circuits. Therefore, a modification of a half-bridge inverter along with a multiwinding coil design is proposed in this study, anticipating an increase in the range of input voltage and benefiting the industry applications. To confirm the practicality of this method, a hardware circuit was made with extensive validation. Experimental outcomes support the feasibility of this proposed method for ozone generators, exhibiting a potential of the method extending to other voltage-source applications. [ABSTRACT FROM PUBLISHER]

Reliability evaluation relates to the impact of faults on customer outage frequency and time. Thus, studying the process of fault isolation and supply restoration is critical in reliability evaluation. In distribution systems, distributed generators (DGs), especially renewable DGs, are increasingly integrated into the network. New issues emerge after DG integration: 1) DG reliability model; 2) change of protection strategy and supply restoration process; and 3) islanding operation. In this paper, an analytical method is proposed to assess the distribution system reliability level considering these issues. The reliability model for DG and load are developed using scenarios reduction techniques based on historical data. The correlation between renewable resources and load is also formulated in the model. When a fault occurs in a distribution system, parts of the distribution system can be operated as islands. The reliability indices of the load point in the microgrid vary according to the power adequacy assessment in the island and supply restoration process. To improve calculation efficiency, the analysis of fault isolation and supply restoration process and reliability evaluation is based on segments instead of single components. Then, the overall reliability evaluation framework is proposed. In the end, a detailed case study is presented. [ABSTRACT FROM AUTHOR]

A self-excited induction generator (SEIG) can be a candidate for isolated applications because it does not require any external exciting power but can independently generate electricity. It is also a good candidate for auxiliary brakes in heavy vehicles for several reasons. First, the power efficiency in a brake system is not important as compared with motors or generators. Second, an SEIG can be controlled by a simple electrical circuit. Third, it can be used for regenerative braking. Finally, it is very robust. In this paper, an auxiliary brake for heavy vehicles is proposed by adapting an SEIG and its analog control circuit. The brake structure is the same as that in conventional eddy current brakes but operates as an SEIG. The suggested control circuit does not adopt an electric controller unit but only consists of simple electric devices. A miniature model was designed and manufactured, and the experimental results using the prototype verify that the proposed brake system, including the controller, is very useful. [ABSTRACT FROM PUBLISHER]

A number of high-power applications require a transportable high-energy, high-current GW generator to drive a pulsed power system at the output. A first prototype, based on exploding wire technology and using an H-bridge circuit configuration, was developed at Loughborough University a few years ago and has been previously reported. The present stage of the work has necessitated the development of a more powerful and energetic source, and this is now based on inductive storage technology. A 400 kJ capacitor bank is connected by a high-Coulomb explosively driven closing switch with an air-cored 0.6 MV transformer, an exploding wire array, and a high-power diode based on a polarity-dependent spark-gap completing the arrangement. The GW generator, including the command and control module, is accommodated in two ISO containers. The various components of the generator are described in this paper, together with results obtained from full-scale tests. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel coordination control scheme for effectively controlling an ac-to-dc converter and a switched excitation capacitor bank of an autonomous self-excited induction generator (SEIG) using a digital signal processor. The aim of the proposed control scheme is to maintain the dc voltage at the output terminals of the ac-to-dc converter under various operating conditions. A three-phase system model is established to simulate the dynamic performance of the studied system. The experimental results based on a laboratory 2.2-kW induction generator driven by a brushless dc motor are also carried out. It can be concluded from the simulated and experimental results that the proposed coordination control scheme can be applied to various SEIG-based renewable-energy systems based by maintaining the output dc voltage of the ac-to-dc converter under different operating conditions. [ABSTRACT FROM AUTHOR]

This paper proposes the design of a novel dc excitation control for a wound-rotor induction generator (WRIG) under autonomous-generation mode using a microcontroller based on a reduced instruction set chip (RISC). The source of the dc excitation control for the studied WRIG is obtained from its generated ac voltage through a step-down transformer, a bridge rectifier, and a dc-to-dc buck converter. In order to effectively modulate the desired dc voltage for controlling the generated voltage of the WRIG, a fuzzy controller embedded in the RISC-based microcontroller is properly designed and implemented using the PIC 8-bit microcontroller under voltage variations. The calculation results are sent to the pulsewidth-modulation ports to drive the power MOSFET switch of the dc-to-dc buck converter. The proposed WRIG system with its dc excitation control is practically implemented in a laboratory wound-rotor induction machine driven by a dc motor. From both experimental measurements and computer simulations, it can be concluded that the proposed isolated WRIG with its dc excitation controlled by the microcontroller can provide better voltage profile than a self-excited induction generator containing only excitation capacitors under various loading and switching conditions. [ABSTRACT FROM AUTHOR]

This paper presents an algorithm that enables single-sensor operation of vector-controlled three-phase permanent-magnet-synchronous-motor voltage source inverter (VSI)-based drive systems. The closed-loop operation is performed through measuring only the VSI dc-link current. The measured VSI dc-link current is fed to a space-vector-based lookup table, which reconstructs the motor line currents. Three Luenberger-style observers are used to filter out the reconstructed motor line currents and estimate the rotor position and speed. The effect of observer bandwidth on the accuracy of the motor's estimated parameters is also investigated. The drive system's physical dynamic stiffness is used as a key metric to compare the drive system performance in single-sensor mode and fully sensored mode, in order to find the lowest steady-state speed limit for the single-sensor drive system operation. [ABSTRACT FROM AUTHOR]

This paper proposes a simple but very effective method to achieve the predictive direct power control (PDPC) for doubly fed induction generator (DFIG)-based wind energy conversion systems. The novel approach is able to operate at low switching frequency and provides excellent steady-state and dynamic performances, which are useful for high-power wind energy applications. Three vectors are selected and applied during one control period to reduce both active and reactive power ripples. Compared to prior three-vectors-based art using two switching tables, the novel approach only needs one unified switching table to obtain the three vectors. Furthermore, the duration of each vector is obtained in a much simpler and straightforward way. The switching frequency can be significantly reduced by appropriately arranging the switching sequence of the three vectors. The influence of one step delay caused by digital implementation is also investigated. The possibility of operating the proposed PDPC under unbalanced grid voltage is also briefly discussed. The novel PDPC is compared with prior three-vectors-based art and its effectiveness is confirmed by the simulation results from a 2-MW-DFIG system and the experimental results from a scaled-down laboratory setup. [ABSTRACT FROM AUTHOR]

In this paper, a bidirectional dc-dc converter is proposed for the automotive engine/battery hybrid power generators. The two-stage bidirectional converter employing a fixed-frequency series loaded resonant converter is designed to be capable of operating under zero-current-switching turn-on and turn-off regardless of voltage and load variation, and hence its magnetic components and EMI filters can be optimized. Also, a new autonomous and seamless bidirectional voltage control method that combines two individual controllers for low-voltage side control and high-voltage side control by introducing a variable current limiter is proposed to provide uninterrupted power to critical ac loads and reduce the size of the dc bus capacitor and the transition time. Experimental results from a 5-kW prototype are provided to validate the proposed concept. [ABSTRACT FROM AUTHOR]