Search

Until recently, electrified aircraft propulsion (EAP) technology development has been driven by the dual objectives of reducing greenhouse gas (GHG) emissions and addressing the depletion of fossil fuels. However, the increasing severity of climate change, posing a significant threat to all life forms, has resulted in the global consensus of achieving net-zero GHG emissions by 2050. This major shift has alerted the aviation electrification industry to consider the following: What is the clear path forward for EAP technology development to support the net-zero GHG goals for large commercial transport aviation? The purpose of this paper is to answer this question. After identifying four types of GHG emissions that should be used as metrics to measure the effectiveness of each technology for GHG reduction, the paper presents three significant categories of GHG reduction efforts regarding the engine, evaluates the potential of EAP technologies within each category as well as combinations of technologies among the different categories using the identified metrics, and thus determines the path forward to support the net-zero GHG objective. Specifically, the paper underscores the need for the aviation electrification industry to adapt, adjust, and integrate its EAP technology development into the emerging new engine classes. These innovations and collaborations are crucial to accelerate net-zero GHG efforts effectively. [ABSTRACT FROM AUTHOR]

The deployment of intelligent transportation is still in its early stages and there are many challenges that need to be addressed before it can be widely adopted. Autonomous vehicles are a class of intelligent transportation that is rapidly developing, and they are being deployed in selected cities. A combination of advanced sensors, machine learning algorithms, and artificial intelligence are being used in these vehicles to perceive their environment, navigate, and make the right decisions. These vehicles leverage extensive data sourced from various sensors and computers integrated into the vehicle. Hence, massive computational power is required to process the information from various built-in sensors in milliseconds to make the right decision. The power required by the sensors and the use of additional computational power increases the energy consumption, and, hence, could reduce the range of the autonomous electric vehicle relative to a standard electric car and lead to additional emissions. A number of review papers have highlighted the environmental benefits of autonomous vehicles, focusing on aspects like optimized driving, improved route selection, fewer stops, and platooning. However, these reviews often overlook the significant energy demands of the hardware systems—such as sensors, computers, and cameras—necessary for full autonomy, which can decrease the driving range of electric autonomous vehicles. Additionally, previous studies have not thoroughly examined the data processing requirements in these vehicles. This paper provides a more detailed review of the volume of data and energy usage by various sensors and computers integral to autonomous features in electric vehicles. It also discusses the effects of these factors on vehicle range and emissions. Furthermore, the paper explores advanced technologies currently being developed by various industries to enhance processing speeds and reduce energy consumption in autonomous vehicles. [ABSTRACT FROM AUTHOR]

The current trend in distributed electric aircraft propulsion systems is to utilize the DC bus system at higher voltage levels than conventional aircraft systems. With Boeing and Airbus utilizing the +/−270 V bipolar DC bus system, the research on high-voltage systems is increasing gradually, with voltage levels ranging from 1 to 10 kV systems or +/−0.5 to +/−5 kV DC bus systems. These voltage levels present considerable challenges to the distributed electric aircraft propulsion systems. In addition to partial discharge effects, there are other challenges, particularly the challenge associated with effectively limiting short-circuit fault currents due to the low cable impedance of the distribution system. The cable impedance is a significant factor that determines the fault current during fault conditions. Due to the low impedance, there is a sharp increase in fault current, necessitating an enhanced protection strategy, which ensures that the system is adequately protected. This paper introduces a coordinated protection strategy specifically designed for distributed electric aircraft propulsion systems to mitigate or prevent short-circuit faults. The proposed algorithm utilizes an I2t-based strategy and the current-limiting-based strategy to protect the system from short-circuit faults and overload conditions. Redundant backup protection is also included in the algorithm in case the circuit breaker fails to operate. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) motors are gaining prominence in subsea applications such as drilling, pumping, and boosting for oil and natural gas extraction. These motors are gradually replacing traditional induction motors. However, starting and operating PM motors at low speeds under heavy loads poses significant challenges. This is because of unknown initial rotor positions and resistive voltage drops due to the presence of a sinewave filter, transformer, and long cable. An unknown rotor position may result in temporary reverse speed, which may cause a loss of synchronism; therefore, initial rotor position estimation is preferable. Additionally, addressing the voltage drop issue requires careful voltage compensation to avoid transformer core saturation. In this paper, an enhanced V / H z starting of a PM motor is proposed with initial position detection (IPD) and voltage compensation to start the motor reliably with a heavy load. The proposed control method is verified with controller hardware in the loop (C-HIL) real-time simulation using a Typhoon HIL-604 emulator and a Texas Instruments TMS320F28335 digital signal processor (DSP) control card. [ABSTRACT FROM AUTHOR]

In electric vehicle fast charging systems, it is important to minimize the effect of fast charging on the grid and it is also important to operate the charging system at high efficiencies. In order to achieve these objectives, in this paper, a sinusoidal half-wave DC current charging protocol and a sinusoidal half-wave pulsed current charging protocol are proposed for the fast charging of Li-ion batteries. A detailed procedure is presented for implementing the following proposed methods: (a) a pre-defined half-sine wave current function and (b) a pulsed half-sine wave current method. Unlike the conventional full-wave sinusoidal ripple current charging protocols, the proposed study does not utilize any sinusoidal full-wave ripple. The performance of these new charging methods on Ni-Co-Al-type Li-cells is studied and compared with the existing constant current and positive pulsed current charging protocols, which have been discussed in the existing literature. In addition, the changes in the electrochemical impedance spectrograph of each cell are examined to study the effects of the applied charging methods on the internal resistance of the Li cell. Finally, the test results are presented for 250 life cycles of charging at 2C (C: charging rate) and the degradation in cell capacities are compared among the four different methods for the Ni-Co-Al-type Li cell. [ABSTRACT FROM AUTHOR]

Subsea oil and gas (O&G) exploration demands significantly high power to supply the electrical loads for extraction and pumping of the oil and gas. The energy demand is usually met by fossil fuel combustion-based platform generation, which releases a substantial volume of greenhouse gases including carbon dioxide (CO2) and methane into the atmosphere. The severity of the resulting adverse environmental impact has increased the focus on more sustainable and environment-friendly power processing for deepwater O&G production. The most feasible way toward sustainable power processing lies in the complete electrification of subsea systems. This paper aims to dive deep into the technology trends that enable an all-electric subsea grid and the real-world challenges that hinder the proliferation of these technologies. Two main enabling technologies are the transmission of electrical power from the onshore electrical grid to the subsea petroleum installations or the integration of offshore renewable energy sources to form a microgrid to power the platform-based and subsea loads. This paper reviews the feasible power generation sources for interconnection with subsea oil installations. Next, this interconnection's possible power transmission and distribution architectures are presented, including auxiliary power processing systems like subsea electric heating. As the electrical fault is one of the major challenges for DC systems, the fault protection topologies for the subsea HVDC architectures are also reviewed. A brief discussion and comparison of the reviewed technologies are presented. Finally, the critical findings are summarized in the conclusion section. [ABSTRACT FROM AUTHOR]

In this paper, an H‐type electric/hybrid electric aircraft propulsion architecture is proposed to address the issues associated with the radial electric propulsion architecture. In a radial architecture, a fault on the main bus or failure of the generator leads to shut down of all the propulsion motors in that channel, thus increasing the burden on the remaining motors to maintain the power required by the aeroplane. As a result, it is necessary to oversize the motors for the purpose of compensating for the loss of other motors. To mitigate these issues, a new H‐type architecture is introduced to isolate the particular faulty section while still maintaining power flow to the remaining healthy motors. The proposed architecture minimises the oversizing of various components in the system as compared to radial propulsion architecture. The sizing of components and the amount of overall mass reduction is discussed by using the proposed architecture. Typhoon Hardware in the Loop platform is used to validate the performance of both the architectures for faults at different locations, and the results are presented. [ABSTRACT FROM AUTHOR]

PAPER 3: An H-TYPE ARCHITECTURE FOR ELECTRIC/HYBRID-ELECTRIC AIRCRAFT PROPULSION SYSTEMS In this study a novel H-type hybrid-electric aircraft propulsion architecture is proposed to address the issues associated with the radial electric propulsion architecture. Public and political pressures for environmental improvements are driving a wave of current interest in all-electric and hybrid-electric aircraft. These emerging new aircraft propulsion systems bring with them the promise of net-zero emissions and greatly reduced noise profiles. [Extracted from the article]

In this work, a multilevel 42-sided polygonal space vector structure for suppression of lower order harmonics for open-end induction motor (OEIM) drive applications is proposed. The proposed power circuit topology consists of two inverters feeding an OEIM from either side. The main inverter fed with a single dc-link providing active power for motoring operation is switched at low switching frequency. The secondary inverter fed with a capacitive supply is switched at high frequency to suppress lower order harmonics upto 39th order, up to the base speed of operation allowing maximum utilization of the dc-link. The advantages of lower order harmonic suppression in motor phase voltage, for polygonal space vector structures, are combined with multilevel inverter topology. This offers various advantages like multilevel operation with low inverter switching for the main power delivery inverter and harmonic suppression throughout the modulation range. The low switching frequency primary inverter generates harmonics of the order $6*k \pm 1$ , where $k = 1, 2, 3,{\ldots }$. The harmonics are suppressed by the capacitor-fed secondary inverter, which supplies only reactive power for suppression of lower order harmonics in motor phase voltage. Use of a single dc-link facilitates four-quadrant operation of the inverter. The proposed scheme is validated for steady-state and dynamic performance by experimental results. [ABSTRACT FROM AUTHOR]

Battery energy storage systems (BESS) based on modular multilevel converters (MMCs) allow battery packs to be integrated into the electrical grid in a modular fashion. Inherent to the operation of the MMC, the module's dc-link capacitor voltage experiences oscillations at grid frequency and its harmonics. This article investigates the close relation between this voltage oscillation and the battery current ripple. The precise capacitor energy requirements for various operations of BESS-MMC, which include arm/phase power balancing and state-of-charge balancing are analyzed in this article. Furthermore, this article also explores the relation between the controller design and the submodule's (SMs) capacitor sizing in terms of its energy requirements. Design guidelines for the SM level voltage control to attenuate battery ripple and detailed analysis for the capacitor energy requirement in each operating mode are presented. The control and capacitor sizing design are validated in real-time using embedded microprocessors in a Typhoon-based controller hardware-in-the-loop environment. [ABSTRACT FROM AUTHOR]

An isolated multilevel bidirectional dc–dc converter is presented in this article to interface the low-voltage (LV) battery and the high-voltage (HV) propulsion inverter in electric vehicles. The proposed topology achieves a HV step-up ratio in the motoring mode by reconfiguring two split capacitor half-bridge circuits in series/parallel through the symmetrical modulation of a voltage bidirectional, two quadrant switch. This reconfiguration generates a high-frequency multilevel voltage output at the dc-bus side of the inverter, which reduces the output filter volume. The dc-bus voltage is regulated by the duty cycle modulation of the intermediary switch in the motoring mode, simplifying the sensing and control. During regenerative braking, the converter is operated with phase shift modulation between the HV half bridges and the LV full bridge to regulate the battery voltage. The presented modulation strategies achieve zero voltage switching for the full-bridge devices over a wide load range. A comprehensive analysis of the proposed multilevel converter in motoring and braking modes along with the design constraints and soft switching boundary conditions is presented in this article. Detailed experimental results on a 1.5-kW laboratory prototype are presented to verify the design approach and illustrate the converter performance. [ABSTRACT FROM AUTHOR]

High voltage direct current (HVdc) power transmission systems do not encounter any natural zero crossing unlike the ac systems, and hence, the dc circuit breakers employed should be fast-acting and reliable to ensure safe operation. Circuit breakers (CBs) that have fast response time with lower energy loss dissipation are required for subsea HVdc transmission systems. This article investigates the performance of various CB topologies, including ultrafast coupled inductor hybrid CB (CIHCB) topology without and with the integration of resistive-type superconducting fault current limiter (R-SFCL) for a 100-kV, 100-MW HVdc transmission systems. It is found that the addition of R-SFCL with 1.7-ms response time decreases the peak current through the breaker and, hence, the power dissipated in the CB during short-circuit fault conditions. Thus, the rating of CB can be significantly decreased with the proposed topology. Furthermore, a comparison of power loss in CIHCB with the existing topologies, such as mechanical CB, resonant CB, and HVdc-hybrid CB, are also presented in this article. [ABSTRACT FROM AUTHOR]

This article proposes a multilevel dc–dc converter topology for fast charging of electric and plug-in hybrid electric vehicles (EVs and PHEVs). The proposed dc–dc converter topology converts the front end ac–dc converter output and provides regulated supply to the EV propulsion battery. The proposed topology consists of full-bridge converter at the primary, while the secondary side consists of voltage doubler rectifier units and combination of diodes and mosfet for reconfiguration of the voltage doubler rectifiers to generate the multilevel voltage. The multilevel voltage at the output helps in reducing the output filter size and increases the power density of the converter. The topology utilizes the resonance between leakage inductor of high frequency transformer, parasitic output capacitors of full-bridge mosfets and voltage doubler capacitors to achieve soft switching (ZVS turn-on) for all the full-bridge devices and soft turn-offfor the rectifier diodes. The load limited ZVS turn on capability of conventional full-bridge topologies is mitigated through the use of resonance between magnetizing inductance of transformer and mosfet output capacitors. The converter is designed for 650 V dc bus input and 200–400 V EV battery output at 100 kW rated charging power. The analysis of the proposed converter in continuous and discontinuous modes of operation, soft switching operation, and the component design guidelines are presented in this article. The proposed converter is validated through detailed PLECS simulation results for 100 kW charging power. Experimental results from laboratory prototype of 500 W power are also presented to validate the design methodology and converter performance. [ABSTRACT FROM AUTHOR]

With the integration of renewable energy sources into the power grid, a number of power electronic converters need to be connected together in parallel. Due to this interconnection among the power converters with a common DC bus, the equivalent impedance of the DC network, i.e., DC network impedance (DCNI) of these parallel converters, may vary and can cause oscillations in the DC link voltage (DCLV). In the literature, impedance models of grid-tied converters (GCs) based on the AC side are well reported without including these variations in DCNI. In addition, the dynamics of a phase-locked loop (PLL) play a significant role in GC system stability. To evaluate these stability issues, this paper proposes small signal impedance models viewing from the DC side of a three-phase GC operating under different control modes considering the PLL dynamics and the DCNI variations. Using the proposed DC impedance models (DCIM), DCLV stability analysis is evaluated for a GC. It is verified through bode plots that the interaction between the proposed DCIM and DCNI leads to unstable operation of the closed-loop converter near the PLL bandwidth when the phase difference between DCIM and DCNI is more than 180 degrees. Finally, the analytically developed models are validated using hardware in-the-loop (HIL) testing. [ABSTRACT FROM AUTHOR]

Direct electrical heating (DEH) is a well-established method for preventing hydrate formation inside subsea oil transfer pipelines. However, poor efficiency and high reactive power requirement of the existing line-frequency DEH systems have necessitated high-frequency power processing along with reactive power compensation. To meet these design objectives, a dc–ac converter using an LCCL resonant tank is presented in this article to function as a high-frequency alternating current source. The LCCL resonant tank is tuned at the frequency of the maximum tank current gain to maximize the heat generation and reduce the VA rating of the tank. The maximum tank current gain operation also ensures zero-voltage switching of the bridge inverter devices. Detailed frequency domain analysis and design guidelines are presented for the proposed LCCL resonant inverter (RI). Experimental results on a 10-A laboratory prototype and controller hardware-in-the-loop results for a 350-A system illustrate the advantages of the LCCL RI in DEH application. [ABSTRACT FROM AUTHOR]

DC-link-based variable speed constant frequency (VSCF) ac power generating system is being considered as one of the popular power architectures in the new generation aircraft to provide backup power to the 115 V, 400 Hz aircraft loads. These systems directly convert the variable frequency output of the generator to the fixed frequency of 400 Hz using a voltage source inverter. These inverters use dc-link capacitors that are heavy and space consuming. In aircraft, the weight requirement is very critical; hence, minimizing the dc-link capacitance is one of the major research challenges to achieve high power density in the VSCF power converter. In this article, novel control strategies to minimize the dc-link capacitance of the ac–dc–ac VSCF power converter are presented. The proposed control strategies enable to achieve 95% reduction in dc-link capacitance value when compared with the conventional control strategy, while the control is robust enough to meet MIL-STD-704F transient specification at the inverter output. The proposed strategies are validated through controller hardware-in-loop testing of the VSCF system based on an 80 kVA brushless synchronous generator and a four-leg inverter. The transient and steady-state operation of the VSCF system with a 95% reduction in dc-link capacitance has been verified for rated power operation. [ABSTRACT FROM AUTHOR]

With the requirements for reducing emissions and improving fuel economy, automotive companies are developing electric, hybrid electric, and plug-in hybrid electric vehicles. Power electronics is an enabling technology for the development of these environmentally friendlier vehicles and implementing the advanced electrical architectures to meet the demands for increased electric loads. In this paper, a brief review of the current trends and future vehicle strategies and the function of power electronic subsystems are described. The requirements of power electronic components and electric motor drives for the successful development of these vehicles are also presented. Index Terms--Electric machines, electric vehicles, fuel-cell vehicles, hybrid vehicles, motor drive, plug-in hybrid vehicles, power electronics, propulsion systems, vehicle strategy.

A hybrid power system consists of a combination of two or more power generation technologies to make best use of their operating characteristics and to obtain efficiencies higher than that could be obtained from a single power source. Since fuel cells directly convert fuel and an oxidant into electricity through an electrochemical process, they produce very low emissions and have higher operating efficiencies. Hence, combining fuel cells with other sources, the efficiency of the combined system can be further increased or extend the duration of the available power to the load as a backup power. In this paper, different types of fuel-cell hybrid systems and their applications are presented. An analysis of the combined cycle operation of a solid oxide fuel cell (SOFC)--microturbine is presented. A strategy for combining the thermophotovoltaic power generation unit and SOFC to obtain the hybrid power system that would have higher efficiency is proposed. The hybrid operation of wind power and solar power system with proton exchange membrane fuel cell is also presented. Index Terms--Fuel cell, hybrid power systems, solar power, thermophotovoltaic (TPV) system, wind power.

This paper discusses the operational characteristics of the topologies for hybrid electric vehicles (HEV), fuel cell vehicles (FCV), and more electric vehicles (MEV). A brief description of series hybrid, parallel hybrid, and fuel cell-based propulsion systems are presented. The paper also presents fuel cell propulsion applications, more specific to light-duty passenger cars as well as heavy-duty buses. Finally, some of the major fundamental issues that currently face these advanced vehicular technologies including the challenges for market penetration are highlighted. Index Terms--Electric drives, electric propulsion, electric vehicles, fuel cells, hybrid electric vehicles (HEVs), internal combustion engines, power electronic converters, road vehicles.

The increasing penetration of renewable energy resources (RESs) leads to a continuous displacement of synchronous generators. Since the grid integration of RESs is usually achieved through inertialess power converters, the system inertia reduces and the power system frequency stability is compromised. Consequently, unexpected generator tripping, load shedding, and even blackouts may occur and pose a great threat to the system normal operation. In view of these challenges, this article explores the possibility of providing the inertia support from power-electronics interfaced smart loads. Specifically, a transformerless electric spring topology and the associated control strategy have been developed to provide a substantial inertia support from the noncritical load. As compared with existing inertia enhancement techniques, the proposed solution is cost-effective without the need of additional energy storage units. The smart load inertia provision capability is quantitatively analyzed and experimentally verified on a laboratory-scale test. In the testing results, 40% and 18% reductions of the rate of change of frequency and the maximum frequency deviation are, respectively, observed with a 12% smart load penetration ratio. [ABSTRACT FROM AUTHOR]

In islanded microgrids, distributed generations (DGs) have been increasingly employed through parallel voltage source inverters (VSIs). To fully utilize the VSI capacity and avoid overloading, the total load power is expected to be accurately shared among VSIs based on their power ratings. However, it is revealed that even small voltage measurement scaling errors may severely deteriorate the power sharing by injecting positive- and negative-sequence circulating currents. An explicit analysis indicates that this issue cannot be avoided if the conventional voltage-feedback control is adopted with an accurate fundamental voltage tracking ability. To solve this problem, a hybrid feedback and feedforward control is proposed, which makes the power sharing robust against voltage measurement errors. In specific, the feedforward control is utilized to enhance the unbalanced and reactive power sharing by reshaping the VSI fundamental output impedance. Meanwhile, the feedback-based impedance shaping control is also employed to improve the harmonic power sharing. As no communication and sensor error knowledge are required, the proposed control scheme provides a simple but effective solution for decentralized power sharing among parallel three-phase VSIs. Finally, both simulation and experimental results are provided for verification. [ABSTRACT FROM AUTHOR]

The starter/generator (SG) system is widely used in various applications, including more-electric/hybridelectric aircraft (MEA/HEA) and hybrid electric vehicles (HEVs). The electric machine operates as a motor to provide the required torque to start the engine. Once the engine starts, the same electric machine transforms to a generator to produce electrical power. With the advantages of a simple and robust structure, low cost and maintenance, and a good overload capability, the cage-type induction machine (IM) is a competitive candidate for SG systems. [ABSTRACT FROM AUTHOR]

In three-phase four-wire systems, the four-leg converter has been an attractive solution for mitigating power quality problems, such as reactive power compensation, load balancing, neutral current reduction, etc. However, its conventional control algorithms based on instantaneous reactive power theory (IRPT) and synchronous reference frame theory (SRFT) have relatively slow dynamic response and unstable operation during transient conditions. Thus, a novel control algorithm using double reduced-order generalized integrators for a four-leg shunt converter is presented in this article. The first integrator is adopted to extract required reference compensation currents for power quality improvement, and the second one is to decouple compensation currents and rectification currents of the converter side. The reference rectification currents are generated using an outer-loop dc-link voltage controller and are synchronized to the three-phase voltages. Since the compensation mode (dc–ac) and rectification mode (ac–dc) of converter are decoupled and regulated separately, the four-leg converter operation with fast dynamic response, robust performance, and flexible controllability is achieved. The effectiveness of the proposed algorithm is validated using both simulation and experimental results for a 1.1-kW rated system. Experimental results for the proposed scheme are presented and compared with that of existing IRPT and SRFT detection methods in the literature. [ABSTRACT FROM AUTHOR]

This paper proposes a soft-switched modulation technique with synchronous rectification for an isolated single-stage single-phase matrix-type dc–ac converter. The dc side consists of a full bridge inverter, and the ac side is a 2×2 matrix converter-based cycloconverter. The proposed unipolar modulation strategy provides zero current switching/zero voltage switching (ZVS) for the ac side devices and ZVS-on for the dc side devices. It also allows natural commutation of the current flowing through the secondary side leakage inductor of the isolation transformer and the grid inductor during unity power factor (UPF) condition, thus eliminates the requirement of snubber circuit. An improved soft-switched flyback-based regenerative snubber circuit is also presented for non-UPF operation. Proposed snubber circuit recycles the energy stored in the snubber capacitors in every switching cycle. A guideline to design snubber circuit along with a comparative study is discussed in this paper. Performance of the proposed hybrid modulation technique is evaluated in an SiC mosfet based 1.2-kW dc–ac converter prototype. A detailed analysis of the converter performance has been presented in this paper considering the circuit non-idealities. [ABSTRACT FROM AUTHOR]

This paper proposes a coupled inductor-based hybrid dc circuit breaker topology with zero current switching for fast fault interruption in dc systems. A series resonant circuit comprising of the secondary winding of a two-winding coupled inductor and a charged capacitor (commutation capacitor) is switched on during fault to inject a counter-current pulse, and, consequently, force a zero crossing of fault current. Proposed solution facilitates arcless breaking for a mechanical circuit breaker due to zero current turn-off. The proposed circuit breaker exhibits fast fault response ($\sim$ 30  $\mu$ s), and the response time is programmable based on the design of the coupled inductor and commutation capacitor. Furthermore, presented solution mitigates the requirement of energy-absorbing elements for demagnetizing the dc network following fault interruption, in contrast to conventional dc breakers. The paper also presents two modified circuit-breaker topologies to achieve unipolar voltage profile on the capacitor, which will enable the use of electrolytic capacitors for commutation so that the capacitor stack size is reduced in high-voltage applications. Detailed analysis and design equations are presented to explain the operation of the proposed topologies. Functionality of the proposed circuit breakers is verified through simulation, and experimental results are based on two laboratory prototypes. [ABSTRACT FROM AUTHOR]

Due to current sensor errors, tolerance of power switching devices, and asymmetry of PWM gating driving pulses, grid-connected inverters without isolation transformer usually have certain amount of dc components injected to the ac grid. Many efforts, such as using a blocking capacitor, a current dc component feedback control, and a voltage dc component feedback control have been introduced to try to suppress the dc injection to the grid. This paper proposes a novel control strategy of suppressing dc current injection to the grid for a three-phase inverter by accurately sensing the dc component of line voltages of three-phase inverter and adding a dc component control loop. A dc suppression control scheme is presented, and the suppression performance of the proposed dc rejection method is evaluated and compared with the traditional method. Finally, the control scheme is verified on a 20-kW three-phase grid-connected inverter. [ABSTRACT FROM AUTHOR]

IGBT short-circuit protection is the key factor to improve the reliability of the power electronics system. The conventional short-circuit protection method based on VCE measurement detects the collector–emitter voltage of an IGBT to determine whether the IGBT short-circuit fault occurs. The blanking circuit is needed in this kind of protection method to avoid the false triggering of the short-circuit protection during IGBT turn-on transient. However, this blanking circuit should be carefully designed for different types of IGBT modules. In order to make the IGBT short-circuit protection circuit suitable for the tolerance of IGBT modules, a self-adaptive blanking circuit combined with the aforementioned short-circuit protection method based on VCE measurement is proposed. The proposed method is achieved by feeding back the required minimum blanking time interval which is decided by comparing the desaturation reference voltage with the collector–emitter voltage. The short-circuit protection delay time for the conventional circuit and the proposed circuit are compared. Experimental results are included to prove the effectiveness of the proposed circuit. [ABSTRACT FROM PUBLISHER]

SiC MOSFET can operate at a junction temperature of 200–250  ^\circ C due to its improved material properties and thermal stability. However, successful realization of SiC MOSFET based high-temperature (HT) converter requires HT gate drivers. This paper presents a low-cost HT gate driver developed with discrete transistors and signal diodes rated at 180–200 ^\circ C. The gate driver has a robust overcurrent and undervoltage lock out protection circuit. The propagation delay of the protection circuit and gate driving circuit is greatly reduced compared to commercial HT gate drivers. A comparative analysis of the developed HT gate driver using discrete components and the commercially available silicon-on-insulator technology based HT gate driver is presented. The performance of the HT gate driver is evaluated for both hard switched fault and fault under load condition at an ambient temperature of 180  ^\circ C. [ABSTRACT FROM PUBLISHER]

In automotive testing systems such as chassis dynamometers and engine dynamometers, effective and efficient control strategies are required to control the induction motor drives, so that fast torque response and low-torque ripples can be obtained. The fast torque response can be obtained by using model predictive control (MPC) due to its high bandwidth over a wide-speed range; and the torque ripple can be reduced by using open-end winding induction motor (OEWIM). Since MPC can be current based or flux/torque based, and can be linear and non-linear, it is necessary to evaluate the effectiveness of different MPC methods on the open-end winding drives. In this study, linear and non-linear current-based MPC methods and flux/torque-based MPC methods for OEWIM drive are derived and evaluated. The transient and steady-state responses of MPC methods are compared through simulation and experiment. The results show that linear MPC methods require less computation time, and under the same sampling frequency, linear MPC methods provide lower current ripple and better zero-sequence-current suppression than non-linear MPC methods. This study provides practical perception for MPC used on multi-level converters and MPC used for unbalanced situations. [ABSTRACT FROM AUTHOR]

Cascasded delayed signal cancellation (DSC) phase-locked loop (PLL) technique has been attractive for grid synchronization under nonideal grid voltage due to its good harmonics filtering capability. However, it has to face the challenge of slow dynamic response. In this paper, an improved DSC-PLL that features high filtering capability, fast dynamic response and simple structure is presented. This PLL employs only one DSC block and one moving average filter (MAF) block to eliminate all even-order and odd-order harmonics while a second-order phase lead compensator and q-axis feedforward path are introduced to increase the PLL bandwidth. The effect of the phase lead compensator on PLL dynamic performance is analyzed. The feedforward path works only when grid voltage frequency or phase jumps and will not affect the steady state behaviors. Therefore, the PLL can improve the phase estimation accuracy and dynamic speed at the same time even under highly distorted and unbalanced grid voltage. Moreover, linear Lagrange interpolation method is adopted to reduce the discretized errors in the digital implementation of the PLL. The effectiveness of the proposed method is validated by both simulation and experimental results. The comparison results with the existing cascaded DSC-PLL and standard MAF-PLL are also presented. [ABSTRACT FROM AUTHOR]

The papers in this special section focus on the fuel cell systems with particular emphasis on extended the lifetime and robustness of these systems. The fuel cell is an electrochemical device that converts the chemical energy stored in a fuel directly into electrical energy, with only heat and water as by-products. Hence, it is one of the cleanest technologies for producing electric power. However, the durability of fuel cells is a main concern for the massive deployment of fuel cell technology for transportation and stationary power generation applications. The fuel cell power generation system consists of a fuel cell stack and the balance of plant consisting of auxiliary units such as air compressor, cooling circuit, power converter, etc. The fuel cell?s lifetime is closely related to its electrode/electrolyte material aging and degradation during its operation. Over time and with use, the degradation of fuel cell performance cannot be avoided; however, with well-designed balance of plant and control system, the rate of performance degradation can be minimized, and the robustness of the fuel cell systems can be improved. [ABSTRACT FROM PUBLISHER]

In more electric aircraft (MEA) system, both ac and dc electric power with multiple voltage levels are required for various aircraft loads. This paper presents an induction generator-based ac/dc hybrid electric power generation system for MEA. In the proposed system architecure, a high-speed induction starter/generator and a low-speed induction generator are installed on the high pressure (HP) and low pressure (LP) spools of the engine, respectively. In generating mode of operation, all of the constant voltage variable frequency ac power is generated by the HP generator while the dc power demand is shared by both HP and LP generators. A control scheme is developed to regulate the ac load voltage and coordinate dc power generation between the two generators. The proposed induction generator based ac/dc hybrid generation system results in reduced hardware requirement compared with both ac and dc primary generation systems. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel harmonic suppression scheme for two-level inverter fed three-terminal induction motor drives using switched capacitive filter. Capacitor fed H-bridges used as filters are cascaded to conventional two-level inverter to eliminate fifth- and seventh-order harmonics for the full modulation range including a six-step operation. For the first time, two-level dodecagonal voltage space vector is implemented with single dc supply for three-terminal induction motor drive. Enabling the switched capacitive filtering at low-voltage domain and shifting the high frequency switching to the switched capacitive filter is shown. A uniform pulse width modulation technique is shown which charges and maintains the capacitor voltages while eliminating the fifth- and seventh-order harmonics for the full speed range. [ABSTRACT FROM AUTHOR]

This paper presents a nine-level inverter topology for an open-end induction motor drive requiring only eight switches per phase, using two three-level inverters with two isolated dc links in a 3:1 ratio. A space-vector-based formulation is used to determine pole voltages such that both inverters supply power to the load over the full modulation range, eliminating the possibility of dc bus overcharging. Proper selection of switching states ensures that all floating capacitor voltages are kept tightly balanced. A digital state machine is used to select sequences of switching states in order to eliminate deadtime-induced pole voltage transients, further improving the output-voltage quality. A level-shifted carrier-based pulse width modulation scheme is used. The steady-state and transient performance of this topology were verified and the experimental results are included. [ABSTRACT FROM AUTHOR]

Unbalance in a three-phase system is created due to single-phase loads and distributed single-phase renewable energy sources connected to the same system. This unbalance can be compensated locally at the point of common coupling using a three-phase four-wire grid-tied inverter. This paper presents a comparative study of three-phase four-wire inverter topologies to compensate for positive, negative, and zero sequence components of the current injected into the grid. The function of the inverter is to inject power to the grid and additional active power compensation (APC) to support unbalance, load reactive power, and load neutral current. Performance analysis and control of these topologies are being compared to evaluate utilization of dc link, size, control, and ease of implementation. A quantitative comparison of the topologies is provided to illustrate the advantages and disadvantages of the analyzed systems. The control algorithm has been presented to regulate the active and reactive power in each phase independently during both grid-connected and islanded modes. The analysis of three-phase 480-V 50-kV·A system based on three H-bridge converter is presented with simulation and experimental results. The experimental results validate the ability of the inverter to provide four-quadrant control of each phase independently. [ABSTRACT FROM AUTHOR]

This paper presents a new space vector pulsewidth modulation scheme to reconstruct phase currents using neutral-point current sensing in three-level T-type converters (TLTTCs). For this purpose, zero vector and offset vectors are replaced with complementary active vectors. These active vectors do not affect the resultant output voltage and the voltage balance at the neutral point of TLTTCs. Hence, the pulsewidths of corresponding active vectors can be adjusted even at low speeds without much additional switching losses and low-frequency noise in the inverter. The modified switching patterns can easily be generated without significant computational complexity. The proposed method is experimentally verified using Texas Instruments TMS320F28335 and Spartan 6 controllers, on a custom designed T-type converter based on Fuji IGBT modules. [ABSTRACT FROM PUBLISHER]

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