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This article presents the design and development of a 7-kV dc bus, 1-MVA, 0–1000 Hz modular multilevel converter (MMC) prototype for high speed medium-voltage variable frequency drives. The system is designed based on 1.7-kV silicon carbide (SiC) mosfet s. First, the full in-depth design of the prototype is provided, including the submodules, arm inductors, and system integration. Then, the unique control scheme and the control hardware design are presented to achieve the full-frequency range operation. The power loss based on Si and SiC devices is analyzed. Finally, experimental results are presented to demonstrate the performance of both the SiC-based submodule and the full-scale MMC system. Compared with the traditional Si-based solution, the established SiC MMC can reduce the drive system volume by 75% and achieve 325% power density, and the peak energy efficiency reaches around 99.35%.

Errors in the injected high-frequency circulating currents are originally investigated for modular multilevel converters (MMCs) in low-speed drive operation. The mathematical analysis reveals that the magnitude and phase errors in the injected circulating currents cause serious energy imbalance in the MMC arms, resulting in large voltage fluctuations in the submodules. Furthermore, these fluctuations get larger when the circulating currents are injected at higher frequencies, which reduces the drive system stability and damages the submodule capacitors. A remedy approach is proposed to minimise the error effects by adjusting the circulating current command. A full-scale system comprising a 1 MVA MMC and a 1 MW induction machine is simulated to verify the theoretical analysis. The experimental investigation of a down-scale MMC feeding an inductor is also conducted to validate the theoretical results.

Solar photovoltaic (PV) energy sources are rapidly becoming more popular. The PV system output power relies on the applied current or voltage nonlinearity and there exist a unique point called the ...

Low frequency operation in the modular multilevel converters (MMCs) is enabled by applying a reference common mode voltage and circulating currents at a frequency much higher than the desired output frequency. The frequency of injected common-mode signals is limited for maintaining a good performance in the circulating current control. Firstly, this paper theoretically analyzes the effect of increasing the frequency of injected common-mode signals by evaluating the error between reference and actual circulating currents. Secondly, we introduce an additional parameter in the reference circulating current to enhance the suppression of MMC's capacitor voltage fluctuations. Intensive computer simulations are developed for a seven-level MMC driving a medium-voltage induction motor drive system to verify the circulating current error analysis and assess the capacitor voltage fluctuations. Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency.

Modular multilevel converter (MMC) is a popular topology in the medium-/high-voltage power conversion due to its modular structure, equal voltage stress, small line-line filter and low-distortion current. It can be operated as an active rectifier and achieve controllable dc output voltage and adjustable active/reactive power. However, dc-link voltage sensors must be installed to realize the feedback control of the system. To reduce the costs and improve the performance of MMC-based rectifier, this paper presents a sensor-less control strategy, which removes the traditional dc-link voltage sensors. An accurate prediction model of dc-link voltage is developed as well as a complete implementing method. The value of the output DC voltage is obtained through the prediction algorithm. The pre-charging, active-power and reactive-power mode of the MMC-based rectifier is extensively studied to validate its effectiveness. The proposed method not only reduces the system device cost but presents excellent steady-state and dynamic performance.

Modular multilevel converters (MMC) are popular for high-voltage, high-power electric energy conversion. To improve the reliability of MMCs, fault diagnosis and tolerant control have been studied by many researchers. Fault reconfiguration, one important step of the fault tolerant control, has become a challenge, especially under high-voltage operation. Arm current overshoot occurs during the reconfiguration if the MMC does not provide redundant submodules (SMs). Existing publications focus on the fault detection and localization. This work investigates the reconfiguration and proposes a suppression control strategy for the overcurrent. The strategy does not require redundant SMs. The proposed method is simulated in Matlab/Simulink and validated by experiments based on a three-phase MMC using an RL load.

The existing concept of aviation turboelectric distributed propulsion for passenger aircraft relies on direct current (DC) for power transmission and distribution. The mass and efficiency performance of DC-based propulsion systems becomes challenging as the system power rating increases. This work proposes a turboelectric distributed propulsion based on brushless doubly-fed machines, which will minimize the power conversion, enhance the mechanical reliability, and strengthen the fault-tolerance capability. This paper presents the background of the proposed turboelectric distributed propulsion along with the system modeling, control algorithm development, and preliminary simulation results of a full flight profile.

In this paper, a dv/dt filter is designed for the modular multilevel converters (MMCs) based variable frequency motor drives. This concept utilizes the inherent arm inductors of the MMC as a part of the output low-pass filter, thus eliminating the need for an add-on inductor. Particularly, a mathematical model is proposed to optimize the filter loss and volume for a given dv/dt requirements. It turns out that with SiC-MOSFET-based high switching frequency operation, the dv/dt filter improves the output power quality and alleviates the voltage stress in motor drive applications. For applications with various requirements on filter volume and loss, weighted-sum optimal solutions are presented. Simulation results based on a seven-level MMC are provided to validate the theoretical analysis.

This paper proposes a high-speed brushless doubly-fed machine for aviation turboelectric distributed propulsion. The electromagnetic performance of the designed machine, including power ratio, voltage capability, power factor, and efficiency is analyzed. A customized rotor mechanical design is introduced, which allows for 4 times increase in speed than legacy designs. A simple TeDP system with one generator and one motor is simulated using FEA-circuit co-simulation in certain operating conditions. The losses and efficiency of the system are investigated for a better understanding of the machine.

Modular Multilevel Converters have been proposed to be a viable topology for medium voltage and high power motor drives due to the stackable structure of the topology. This allows for a transformer-less drive, better output current THD and reduces input and output filter sizes compared to traditional topologies. Replacing the traditional Si IGBT based submodules with SiC MOSFETs has been shown to improve the overall efficiency of the MMC. However, the lower switching losses of SiC MOSFETs have not been fully utilized to realize further system level improvements in the MMC. In this paper, the impact of the SiC MOSFETs on the efficiency, power density and output current THD of the drive is compared against Si IGBTs using analytical and simulation. A 7 kV dc bus, 4.16 kV ac, 1 MVA, 0-1,000 Hz medium voltage variable speed drive based on 1.7 kV devices based is used for the comparison.

With a growing number of silicon carbide (SiC) devices used in the modular multilevel converter (MMC) based medium voltage motor drive systems, the reflected wave phenomenon (RWP) under high dv/dt needs to be studied. In this paper, the voltage reflection in the MMC based motor drives is analyzed with a focus on the impact of the leakage inductance of the arm inductors. A seven-level MMC built with 1.7 kV SiC MOSFETs is modeled and simulated. The simulation results show that the leakage inductance of the arm inductors helps reduce the dv/dt at the MMC output but increases the voltage stress on the arm inductor windings and the load. A simple method is proposed to mitigate dv/dt and voltage overshoots applied to the machine windings. Presented simulation and experimental results validate the proposed method.

This paper proposes a double-end sourced layout for multichip SiC MOSFET power module adopting conventional wire-bonded packaging technology. The unique design provides each MOSFET with two parallel commutation loops by incorporating a symmetrical pair of dc-bus terminals into the power module. This new layout provides symmetrical equivalent power loops to each paralleled MOSFET and thus enables consistent switching performances and equal dynamic current sharing for the paralleled MOSFETs. Compared to the conventional design, the proposed design reduces the equivalent power-loop stray inductance by more than 50% and achieves improved dynamic current sharing among devices. By mitigating the imbalance of the switching current, the new module design demonstrated reduced temperature differences among devices and decreased near-field radiation noise level compared to the conventional layout. These features can further help to improve the power module density by shrinking the heat sink and integrating the gate driver board with the power modules. In this paper, an analytic model has been proposed for fast prediction of the near-field radiation from the power module. Detailed design procedures and experimental validations are also included in this paper.

Asymmetries in permanent magnet synchronous machines (PMSM) can result from manufacturing tolerances or optimization techniques that deliberately introduce them on rotor, stator, or both. This paper analyzes the impact of such unbalance on the air gap pressure, that is radial and tangential to the direction of motion, by means of Maxwell Stress Tensor; also, their consequences on torque pulsations and unbalanced magnetic pulling. Neglecting the manufacturing variations in the analysis of high power density PMSMs underestimates the resultant torque ripple. Additionally, new vibration modes occur due to unbalanced radial pressure. On the other hand, a geometry optimized to minimize torque ripple through controlled asymmetry is investigated, the approach compensates harmonics in torque effectively, but such compensation does not have the same effect on radial forces. Finite element analysis and experimentation are used to support the analysis and it is found that an asymmetric PMSM with low torque ripple will not necessarily produce lower vibrations and noise.

In recent years, a lot of research efforts have been devoted to the application of sliding mode control (SMC) techniques to power electronic equipment and electrical drives. Hundreds of technical papers have been published in this research field. The tendency stems from the nature of sliding mode with discontinuous control actions and due to its potential for circumventing parameter variation effects along with low implementation complexity. This paper presents a control design procedure for DC/DC power converters. It develops SMC algorithms for several types of DC/DC converters with different control objectives, complete and incomplete information about system states. A chattering reduction approach for power converters based on the idea of multi-phase converters is also proposed. A wide range of MATLAB/SIMULINK computer simulations along with experimental results are provided to demonstrate the effectiveness of the proposed control design.

This paper presents a high-temperature (HT) gate drive and protection circuit for Silicon-Carbide (SiC) power mosfets entirely built from commercial off-the-shelf HT discrete components. To estimate cost reduction, a brief comparison was made between the proposed circuit and a commercial circuit using silicon-on-insulator integrated circuits. To evaluate performance, power tests were conducted up to 180°C in a thermal chamber. Eventually, the proposed circuit achieved a 90% cost reduction, and all functions were validated by experiments at 180°C. This demonstrated that the proposed circuit is a cost-effective solution for contemporary HT applications.

In the production of surface-mounted permanent magnet machines, manufacturing tolerances also contribute to torque ripple. Additional harmonics of low electrical orders are created in the torque spectrum. Slight manufacturing variations develop asymmetry conditions in the rotor as well as in the stator. Finite element models can be used to analyze the magnitude of pulsating torque generated due to these asymmetries. However, due to its random nature, lack of periodicity, and symmetry, it is time consuming to study the problem with numerical methods for its uneven geometry that does not allow reduced geometrical models. Moreover, the experimental verification of all possible variations would be very challenging as it would require part dimensioning and part sorting a large quantity of motor builds and finally testing of all samples. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the torque ripple. The model shows an agreement against finite element models and also with experimental results when predicting torque harmonics that come from asymmetries.

Medium-voltage motor systems with adjustable- speed drives are employed in a wide range of applications. The adoption of medium-voltage Silicon Carbide (SiC) devices in motor drives can improve motor system’s efficiency, power density, and dynamic response. But the high switching dv/dt (short rise time) produced by SiC devices increases the stress on the motor winding insulation and leads to partial discharges. This paper studies the partial discharge in the medium-voltage motor winding subjected to two-level PWM waveforms produced by medium-voltage SiC devices. Partial discharge inception voltages (PDIVs) and repetitive partial discharge inception voltages (RPDIVs) of the motor winding at various rise time, switching frequencies and modulation index are tested. Statements on PD behaviors are analyzed based on the test results.

This paper proposes a simple control strategy for the dv/dt reduction in the modular multilevel converters (MMCs) based motor drives. In particular, the control strategy aims at the reduction of the MMC output voltage slew rate by coordinating the switching transients of several submodules. It is realized via utilizing extra submodules or simply applying a delay time to the switching transients. Both methods are implemented without affecting the switching speed of the power devices. Thus, the methods could mitigate the drawbacks caused by the high dv/dt while maintaining the advantages brought about by the fast switching speed of the silicon carbide (SiC) devices. The simulation results and test results based on a SiC MMC are provided. It is shown that the proposed control methods bring down the output dv/dt by around 50 %.

As a learning step to gain experience in designing high specific power electric machines for demanding applications such as aircraft propulsion, this paper presents research results in the design, fabrication, and experimental testing of a scaled-down 300-kW electric machine. With advanced structure and materials, this machine achieves an active-material specific power of 14.4 kW/kg and an electromagnetic efficiency of 99.2% under full load condition using finite element analysis. The mechanical integrity of the rotor is fully validated at the rated speed of 17, 000 rpm in finite element analysis. The fabricated machine prototype is mounted onto a 350-hp dynamometer for comprehensive performance characterization. The efficiency of the machine prototype is mapped based on the experimental measurements under various operating conditions. In this paper, the electromagnetic analysis, trade-offs at the design stage, mechanical stability considerations, and experimental testing results are summarized and presented in detail.

This paper reviews popular methods for estimating damper currents in field-would salient rotor synchronous machines. Most research dealing with electric machine analysis tend to simplify multi-damper bar designs with two orthogonal dampers (commonly called D and Q). This paper uses an internally developed FEA (Finite Element Analysis) software to independently analyze the current in each damper bar using 3 popular methods.

This paper presents a high-speed and high-dynamic variable frequency drive (VFD) based on the modular multilevel converter (MMC) and silicon carbide (SiC) devices. A compact submodule design with the straightforward extension feature is introduced. An integrated control scheme including the low- and high- speed control is developed. Based on the designed prototype and the advanced control scheme, the dynamic response including speed acceleration and torque step-change capabilities are investigated. Besides, the steady-state performance in the high-speed range is also examined in terms of speed control accuracy and current distortion. Validated by the experimental results, the developed VFD prototype with the proposed control scheme can successfully reach the high speed (6000 rpm). It has accurate speed control (±1%) and low current distortion (THD%=2.54%) in high-speed operation, as well as the robust dynamic response.

Modular multi-level converters (MMCs) are one of the promising topologies in recent years for medium or high voltage applications. They are considered as the next generation DC/AC converters for medium/high voltage (MV/HV) motor drive applications due to their transform-less structures, high efficiency and modularity. Reliability is one of the most important challenges in MMCs, since a large number of power switching devices are used and each of these devices can be considered as a potential failure point. It is significant to detect and locate the fault accurately and apply appropriate protections in a timely manner. This paper investigates the behavior of the failure submodules and healthy submodules and use artificial neural network (ANN) classification algorithms for single-submodule open-circuit fault diagnosis. The ANN algorithm is implemented in field programmable gate array (FPGA) and the ANN parameters training is completed offline in Matlab. Experimental results of the proposed fault diagnosis for a single-module open-circuit fault are presented in this paper.

In a mass production environment, due to the manufacturing tolerances, additional orders of cogging torque are created in addition to the fundamental components. The tolerances lead to asymmetry conditions both in the rotor as well as in the stator. Finite-element models can be used to analyze the cogging generated due to these asymmetries. However, it is extremely time consuming to study this uneven geometry numerically since periodicity and symmetry conditions cannot be used to reduce the model. Moreover, the experimental verification of all possible variations would be very challenging, as it would require part dimensioning, part sorting, a large quantity of motor builds, and finally testing of all samples. Therefore, in this paper, an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against finite-element models and also with experimental results.

This paper presents the effects on output voltage and current total harmonic distortion (THD) response with increasing the arm inductance (smooth reactor for HVDC) for the modular multilevel converter (MMC) behavior based on a closed loop-needless PID controller control. Also, it presents the effects on MMC quantities, such as a circulating current ripple, maximum output voltage, and submodule capacitor ripple responses with increasing the value of arm inductance. Because increasing arm inductor size could reduce the THD and circulating current ripple waveforms of the MMC, this effect will be investigated in this paper. The closed loop-needless PID controller control is presented first. Second, an examination of the effect of changing the arm inductor for MMC behavior is carried out based on many simulation results in this paper in order to analyze the change in THD for all MMC quantities, including circulating current, upper arm current and voltage, lower arm current and voltage, and AC output voltage and current. Third, arm inductance relationships with output voltage and current THD are shown. Also, arm inductance relationships with a circulating current ripple and submodule capacitor ripple are presented. As a part of this study, the relationship between arm inductance and maximum output voltage is explained. Finally, the hardware design and software design of the prototype are presented to verify the arm inductor value effect on MMC experimentally. The experimental results are also documented in this paper.

Power conversion from ultravoltage direct current (UVdc) to ultravoltage alternating current (UVac) is the biggest challenge facing industrial power application companies. Converting UVdc transmission systems with 2200 kV dc and distance up to 3000 km into UVac is the most challenging issue associated with transmitting power by UVdc transmission systems. This paper proposes an approximated arm energy control algorithm for a modular multilevel converter with a large scale of submodules per arm to convert UVdc of 2200 kV and more into UVac in order to achieve total harmonics distortion for UVac systems of $N$ ) is derived first. Second, the flooring switching pulsewidth modulation is explained in order to generate the number of inserted and bypassed submodules per arm. Third, submodules’ selections are proposed and verified by the simulations. Fourth, a set of simulation results for a dc bus of 2200 kV and 481 levels for the output voltage conducted in the MATLAB/Simulink environment are presented to verify the proposed algorithm. Finally, the proposed algorithm is experimentally verified by the hardware and software designs of the prototype.

Power generation and grid stability have become key issues in the last decade. The high penetration of large capacity wind generation into the electric power grid has led to serious concerns about its influence on the dynamic behavior of power systems. The low-voltage ride-through (LVRT) capability of wind turbines during grid faults is one of the core requirements to ensure stability in the power grid during transient conditions. The doubly-fed induction generators (DFIGs) offer several advantages when utilized in wind turbines, but discussions about their LVRT capabilities are limited. This paper presents a comprehensive study of the LVRT of grid-connected DFIG-based wind turbines. It provides a detailed investigation of the transient characteristics and the dynamic behavior of DFIGs during symmetrical and asymmetrical grid voltage sags. A detailed theoretical study supported by computer simulations is provided. This paper also provides a new rotor-side control scheme for DFIG-based wind turbines to enhance its LVRT capability during severe grid voltage sags. The proposed control strategy focuses on mitigating the rotor-side voltage and current transients during abnormal grid conditions, without any additional cost or reliability issues. As a result, the DFIG performance is improved and utility company standards are fulfilled. Computer simulations are used to verify the expanded ride-through capability of the novel strategy and its effective performance compared to the conventional control schemes.

A novel discharging control strategy is proposed and implemented for submodules in modular multilevel converters (MMCs). By sequentially controlling the arm currents of a MMC to the arm resistors, all submodule capacitors are discharged safely and rapidly without adding additional devices and circuits, resulting in improved performance and reduced cost. Both open- and closed-loop control methods are evaluated for effectiveness of the new control strategy. Simulation and experimental results are provided to validate the new control strategy.

The errors between the reference and actual injected circulating currents are investigated for modular multilevel converters (MMCs) in low frequency operation. These errors cause low frequency oscillatory power components in the MMC arms and large voltage fluctuations in the submodule capacitors. By adjusting the circulating current reference with a single parameter, it is possible to compensate the errors and suppress the undesired voltage fluctuations. Computer simulations and experimental results are provided to verify the theoretical derivations.

Modular multilevel converters (MMCs), with the filter-less and transformer-less features, are considered as a promising topology for high-efficiency medium voltage (MV) high voltage (HV) drive systems. However, a large current ripple flowing through the capacitors of each submodule will cause significant capacitor voltage fluctuation. This paper proposes a new compensation method in common mode voltage injection to further reduce the magnitude of the fundamental component in capacitor voltages. The capacitor voltage ripples are reduced significantly by using the proposed control method, which means that smaller size of capacitors can be used for same voltage ripple requirements. Simulation and experimental test results verify the proposed compensation method using a three-phase permanent magnet synchronous machine (PMSM).

A four-level Hybrid Clamped Converter (4L-HCC) is a novel promising DC/AC multilevel converter for high-efficiency medium-voltage drives. This paper presents a new control method of the 4L-HCC using the switching state redundancy to reduce the DC-link capacitor voltage ripples at low frequencies (

Application of electric machines in the traction and transmission systems of hybrid/electric vehicles has been studied for many years. The hybrid vehicle based on dual mechanical port (DMP) electric machine has gained more and more attention, because it eliminates the need for planetary gear and combines the motor and the generator into a compact electric machine. The DMP machine with a squirrel-cage outer rotor (SCDMP) is investigated in this paper. Due to its unique electromagnetic characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results show that the proposed control algorithm is able to independently control the torque productions and the flux levels of the two rotors of the SCDMP machine.

A new type of electric machine with two free rotating rotors [dual mechanical port (DMP)] is investigated in this paper. Since this DMP machine has a squirrel-cage outer rotor, it is named as SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models are verified by finite element method and simulation. The results show that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine.

Modular multilevel converters (MMCs), with the filter-less and transformer-less features, are considered as a promising topology for high-efficiency medium voltage (MV) high voltage (HV) drive systems. However, at low frequencies (< 30 Hz), a large current ripple flowing through the capacitors of each submodule will cause significant capacitor voltage fluctuation. This paper proposes an optimal submodule capacitor selection based on the common mode voltage injection. The proposed sizing model includes two functions: a) accurately estimating the capacitor voltage ripple based on the drive system parameters; and b) identifying the minimum capacitance of the submodule capacitors based on the allowed maximum capacitor voltage fluctuations. Simulation and hardware-in-the-loop (HIL) test results show that the error between the actual and estimated values of the voltage fluctuation is within 3% using the proposed model.

The four-level Hybrid Clamped Converter (4L-HCC) is emerging as a promising DC/AC converter topology for high-efficiency medium-voltage drives. However, without proper control, the voltage fluctuation of the DC-link capacitors will be excessive, resulting in distorted AC current and stability issue in low frequency operation. In reality, the distorted current makes it impractical for motor drive during the rotor speed ramp up. This paper presents a control method of the HCC to reduce the DC link capacitor voltage fluctuations at very low frequency. Simulation results show that the proposed method can significantly reduce the capacitor fluctuation from 43% to 4.3% at 5 Hz and allow the HCC to operate at high steady-state frequency (60Hz). Meanwhile, a comparison study is conducted between the 4L-HCC and an equivalent 4-level Modular Multilevel Converter (4L-MMC). Compared to the equivalent MMC converter at very low frequency, the properly controlled HCC has more margin in DC bus voltage to generate high AC output voltage with a lower AC output current in THD and lower switching losses in power switches.

This paper presents the design and operational analysis of a high-performance squirrel-cage induction machine intended for wide load range applications, including electric traction and highly dynamic industrial loads. High performance operation and high torque density are achieved through a combination of four strategies: (1) An inverter-dedicated design in which stator and rotor configurations are based on low slip; (2) High-performance materials including high flux cobalt alloy and copper rotor bars; (3) Optimized pole counts with relatively high frequency stator operation to avoid field weakening in most load ranges; (4) Adaptive flux control to maintain high efficiency over a 10:1 or more load range. Based on the high cost of rare-earth permanent magnets, the cost tradeoffs for cobalt alloys become plausible and feasibility is studied. The design and operation of the induction machine's broad motor behavior are discussed, and simulation results are used to validate its application in electric vehicles. It is verified that the design achieves 4x higher torque density than conventional machines of the same size. At the same time, nominal efficiency of the design is greater than 96% over a wide load range, and the machine is capable of peak efficiency as high as 98%.

An optimally designed ferrite permanent magnet (PM)-assisted synchronous reluctance machine (PMaSynRM) is presented to demonstrate its feasibility in electric vehicle applications. The Prius rare-earth interior PM machine is used as the benchmark, and through theoretical study and experimental testing, it is verified that the optimally designed PMaSynRM can achieve performance very close to that of the benchmark PM machine with much lower costs.

Purpose – The purpose of this paper is to present optimally designed synchronous reluctance machine (SynRM) to demonstrate the feasibility of eliminating the use of rare earth permanent magnet (PM) in electric machine for vehicle traction applications. Design/methodology/approach – A typical rare earth interior permanent magnet (IPM) machine is used as the benchmark to conduct the optimal design study. Based on the flux distribution, major changes are made to the rotor lamination design. Enhanced torque production and lower torque ripple are specifically targeted as the two main objectives of the proposed design approach. Findings – As a result, the optimally designed SynRM can achieve performance very close to that of the benchmark PM machine with a potential for further improvement. Originality/value – Discussions of IPM replacement by optimally designed SynRM in electrical and hybrid electrical vehicles are given in terms of performance and cost.

The capabilities of peak power and continuous power are the main concerns for electrified vehicles. To achieve good acceleration on uphill climbing, improved peak power density is necessary. The motor's peak power is determined by the maximum allowable temperature of the motor package. If the temperature at peak output power can be kept low, then a higher peak power is achieved. The major purpose of thermal management is to control both the heat generation and dissipation. Therefore, to maximize the interior permanent magnet (IPM) motor peak power capability, the losses or heat generation among the various key components, such as the windings, stator core, and magnets, should be reasonably distributed.

With the proposed dual-current-loop control algorithm, the torque and air-gap flux of a doubly fed induction motor are controlled directly. Compared to the singly fed permanent magnet and induction motors, the torque-speed operation region for electric vehicle/hybrid electric vehicle applications is nearly doubled with the proposed dual-current-loop control algorithm for a given battery voltage. Computer simulations and experimental results are provided to verify the proposed control algorithm.

In the widely applied non-direct driven wind power generation system, a gearbox is connected between the wind turbine and the high speed doubly-fed induction generator (DFIG) so that the system could be smaller and supply power with constant voltage and constant frequency as the wind turbine speed varies. However, the multi-level mechanical gearbox is rather vulnerable and poses many difficulties to maintain. Electrical variable transmission (EVT), an electrical continuous variable gearbox, is a very competitive alternative for vulnerable constant speed-ratio mechanical gearbox. In this paper, the application of EVT in wind power generation system with its unique power conversion characteristics is presented. EVT machine structures and the main principles of the EVT-based wind power generation system are introduced. Unique power conversion characteristics of the EVT-based system are investigated and compared among the conventional DEIG system and direct-driven permanent magnet generator (PMG) system. A controller without maximum power point tracking (MPPT) control to the outer rotor is implemented in Matlab/Simulink and speed sensorless control of the inner rotor is tested. The operational principle and the operation modes are evaluated by computer simulation and system experiments.

In this paper, a comprehensive evaluation work on 1.7 kV SiC Super Junction Transistor (SJT) power module and 1.7 kV SiC MOSFET power modules is presented. Both device static and dynamic performance is extracted and compared at wide device current range and temperature range. The data presented in this paper can be used as input for medium voltage power conversion system power transistor selection, gate drive design and system level thermal management design. Since the SiC SJT is a new power transistor with unique current driven mechanism. A dedicated section discusses the SiC SJT power module gate drive configuration and device false turn on suppress as well. In a summary, 1.7 kV SiC SJT shows superior on state conductivity, but similar switching performance compared to 1.7 kV SiC MOSFET power modules.

A 30kVA SiC MOSFET inverter is developed for 180°C ambient temperature operation. The power structure and gate drivers of the inverter system are designed based on SiC MOSFETs and other high temperature (HT) components. The prototype inverter system has been built, and placed in a thermal chamber of 180°C for testing. The HT operation of the inverter has lasted for more than 85 hours accumulatively without any problems, and the designed HT SiC inverter technology is verified.

Wireless power transfer (WPT) holds great potential to achieve strong galvanic isolation, compact size, and low parasitic capacitance in the power supply of gate driver. In this paper, a wireless power supply is designed and analyzed for high voltage gate driver application. The performance of the power supply in terms of power delivery, parasitic capacitance, and driver output is explored in the functional test. Meanwhile, electromagnetic interference (EMI) is investigated in both frequency and space distribution based on measurement and simulation. The experimental results demonstrate that the prototype successfully delivers power for gate driver board with an 80 mm air gap while the maximum transfer efficiency is kept around 90%. The parasitic capacitance brought by the air gap is only 1.72 pF, which significantly increases common mode impedance. Radiated EMI affects the frequency span around the resonant frequency, and its distribution regularity in space is clearly displayed by field curves in horizontal axis and vertical axis.

This paper proposes a double-end sourced layout for wire-bonded multi-chip paralleled silicon carbide power modules. The simulation results demonstrate suppressed voltage-overshoot and improved current-sharing with the proposed layout, as well as reduced total switching losses and a more even loss-distribution among paralleling devices. Power modules were fabricated in the lab, a double-pulse test and continuous power test were conducted, whose outcomes verified the simulation results. Furthermore, this paper investigates and compares the thermal management on the proposed layout and the conventional baseline layout. It proves that the proposed structure has a smaller footprint on the heatsink under the same thermal requirements. Finally, a high power-density three-phase inverter that adopts the proposed structure was designed and tested.

A 30kVA SiC MOSFET inverter is designed and evaluated for 180°C ambient temperature operation. The entire inverter system is designed for high temperature (HT) except the DSP control circuit in room temperature environment. The power structure is designed using SiC MOSFETs and HT capacitors. The gate driver circuits with protections are also designed for the HT environment. The prototype has been built and tested in 180°C environment at 30kVA for 5 hours accumulatively without any problems. The inverter is also tested in −10°C environment at its full capacity of 30kVA for competed evaluation.

This paper proposes an improved wire-bonded design with a unique double-end sourced (DES) structure for multi-chip paralleled silicon carbide (SiC) power modules. The new structure adopts two pairs of DC bus-bars to source the power module from the two ends, not only shortens the equivalent power loops but also provides a symmetrical structure for the paralleled devices. The proposed design achieved a minimized power-loop inductance of 7.2 nH. In addition, the design improved current sharing among the paralleled devices. A 1200 V, 60 A SiC metal-oxide-semiconductor field-effecttransistor (MOSFET) half-bridge module (3 devices in parallel) is fabricated and tested for verification. Improved performances are observed in both switching and continuous operation. A converter level design is also presented to accommodate this unique module structure.

This paper introduces a new method to solve the sensorless control problem for a grid-connected doubly fed induction machine (DFIM). The proposed method is based on high-frequency signal injection and the fact that the rotor of a DFIM can be seen as the rotating secondary of an induction transformer. The commonly used sensorless technique based on stator-flux linkage, aside from being parameter sensitive, does not work during fault ride through (FRT) conditions. Nevertheless, the proposed method is parameter independent and remains fully functional during FRT conditions. Moreover, as opposed to other high-frequency injection methods, the proposed method does not require rotor saliency. The mathematical principle of the proposed technique and its implementation are presented. Computer simulations and initial experimental results are also included for verification.