Due to its low cost, excellent electrical and thermal properties, high reliability, and resistance to electromigration (EM), nano-Cu sintering paste is regarded as the next-generation die interconnection material for wide bandgap (WBG) semiconductor applications. However, there are no experimental reports on the application of nano-Cu sintering in high-power double-sided cooling (DSC) silicon carbide (SiC) power modules. This work fills this gap by demonstrating the design, fabrication, and performance of a novel high-power DSC SiC MOSFET module based on nano-Cu sintering. Using self-prepared Cu paste and a formic acid-assisted low-temperature pressureless Cu sintering process, a 1200 V/600 A DSC power module is fabricated. When sintered in a formic acid atmosphere at a temperature of 250 degrees C, the porosity of the sintered Cu is only 14.08%, and the shear strength reaches 42.5 MPa, twice that of traditional solder. Furthermore, the module exhibits superior switching performance, with switching losses reduced by more than 20% compared with a similarly rated commercial module. Its power density reaches 6.70 x 10(4) kW/L, while the total parasitic inductance is only 3.94 nH, a 40.3% reduction compared with a commercial module. Additionally, the dense Cu sintering structure and low interfacial thermal resistance significantly enhance the thermal performance of the module, with a junction-to-case thermal resistance as low as 0.035 K/W, representing a 54.5% reduction compared with a commercial module. These findings demonstrate the feasibility of applying the nano-Cu sintering process in high-power-density electronic devices.

Although the field-oriented control (FOC) with flux-weakening (FW) function has been investigated in dual-three-phase (DTP) PMSM drives, the research on model predictive control (MPC) with FW is few. In this paper, the MPC with FW and using hybrid voltage vector (VVs) is proposed. To avoid overmodulation when using FOCs with FW, a margin needs to be kept in the voltage constraint of FW or constraints needed to be applied on the z1z2 voltage reference. In contrast, in the proposed hybrid MPC both the margin and the constraints are freed with sequential optimization, resulting in larger torque-speed operation range and lower current THD. In addition, hybrid VVs are used in the proposed MPC. Two long VVs are used for αβ regulation per control cycle, which increases the torque-speed operation range, while two z1z2 virtual VVs are used for z1z2 regulation, which ensures high z1z2 harmonic suppression capability. The VVs are selected based on voltage reference estimation for light computation burden, while their duty ratios are calculated by the projected quadratic programming (QP) algorithm for the same reason. With the proposed hybrid MPC, wider torque-speed operation range and lower current distortion can be obtained, compared with the traditional MPC using virtual VVs and FOC with FW. Finally, experiments are conducted to verify the feasibility and advantages of the proposed method.

This article proposes two novel hybrid magnet rotor topologies, spoke-V and spoke-delta, for interior permanent magnet synchronous machines (IPMSMs) for reducing rare-Earth magnet usage while maintaining high electromagnetic performance in electric vehicles (EVs). Using the Tesla model 3 IPMSM as a reference, the models are parametrized and multiobjective optimization is performed. The proposed spoke-V and spoke-delta configurations achieve NdFeB volume reductions of 19.4% and 25.8%, respectively, while matching the torque performance of the reference machine. This results in a 20.5% and 35.1% improvement in torque per unit volume of rare-Earth material. Detailed electromagnetic analyses are conducted under open-circuit, peak-load, and torque-speed characteristic analysis under full operating conditions, demonstrating the feasibility of the proposed topologies for high-speed EV applications. A small-scale prototype is manufactured and tested to verify the accuracy of the calculations. These findings highlight the potential of asymmetric hybrid magnet rotor designs to deliver less rare-Earth and high-performance IPMSMs, contributing to the development of more sustainable and cost-effective electric drive solutions.

The energy backflow phenomenon is unavoidable in small dc-link capacitor-based PMSM drive systems, which is first identified and comprehensively analysed in this paper. This phenomenon occurs when the amplitude of the stator voltage exceeds the minimum value of the fluctuating dc-link voltage. To address this issue, flux weakening (FW) control can effectively reduce the stator voltage and mitigate the energy backflow phenomenon. However, dc-link voltage fluctuation can introduce several challenges to the conventional feedback FW control. For instance, a dc offset in the calculated d-axis reference current is identified in this paper due to the dc-link voltage fluctuation. Additionally, an analysis of the small-signal model reveals that when the fluctuating q-axis voltage becomes negative, it can lead to system instability. Moreover, the commonly used PI controller in FW control fails to adequately control the ac component introduced by these fluctuations. Therefore, this paper proposes an optimised FW control method to mitigate the energy backflow issues. Furthermore, an optimal phase angle selection method for the d-axis reference current, based on the least mean square algorithm and gradient descent algorithm, is introduced to suppress current ripple caused by the fluctuating dc-link voltage. Experimental results validate the effectiveness of the proposed optimised methods.

In this paper, the magnet pole design improvements of hybrid-pole variable flux memory machines (HP-VFMMs) are proposed and investigated. A series of HP-VFMMs with different magnet pole topologies are developed to achieve a well-balanced tradeoff between torque density and flux regulation range. The original topology Model-A features a geometric combination of spoke-type high coercive force (HCF) permanent magnets (PMs) and flat-type low coercive force (LCF) PMs. This configuration can significantly expand the design flexibility of HP-VFMMs, offering a high degree of design freedom. To strengthen the flux regulation and unintentional demagnetization (UD) withstand capability of LCF PM, an improved magnet pole topology Model-B characterized by an integration of V-type HCF PM and flat-type LCF PM is developed. First, the machine topologies and operating principles are introduced, respectively. Then, the design concept for deriving the HCF PM pole from spoke-type to V-type is presented and elaborated based on analytical and finite element (FE) methods. Subsequently, for addressing the manufacturing and mechanical reliability issues arising from the relatively complex rotor topology, a simplified rotor design Model-C is further developed. The effects of HCF PM parameters on key performance metrics are investigated, highlighting the performance enhancement mechanisms, as well as identifying optimal designs. Subsequently, the electromagnetic characteristics of the proposed HP-VFMMs with different hybrid magnet pole designs are evaluated and compared by FE method. Finally, a proof-of-principle machine prototype is manufactured and tested, confirming the feasibility of the proposed design.

For the N-module permanent magnet synchronous motor (PMSM) drive system, the same phase currents of different submodules can be redundant with each other for closed-loop control. Fast and accurate replacement of currents measured by faulty current sensors is essential for the highly reliable operation of the system. In this article, a similarity learning-based fault diagnosis method for N-module PMSMs is proposed to achieve faster fault detection than traditional methods. Also, the proposed method can accurately identify all 48 fault combinations of current sensors in the faulty submodule. In particular, a hybrid metric distance (HMD) is designed to extract the different characteristics of the coaxial reference voltage based on a modified coordinate transformation of the different axis directions. Based on the HMD, an accumulative sum trigger value (ASTV) method is designed to accurately locate faulty submodules and sensors in case of gain and zero-offset faults. Based on the discrete Laplace operator can accurately locate the faulty submodule and sensor in case of signal loss and stuck faults. In addition, the discrete Laplace operator is combined with the half-wave symmetry variable for fault-type identification. The performance of the proposed method for single-current sensor and dual-current sensor fault diagnosis is experimentally verified in a four-module PMSM driver.

The field-oriented control (FOC) with flux-weakening function (FW) has been investigated in dual-three-phase (DTP) PMSM drives. However, the research on model predictive control (MPC) with FW is few. In this paper, the MPC with FW and using hybrid voltage vector (VVs) is proposed. Different from the FW in FOC, where the margin needs to be kept in the voltage constraint of FW to avoid overmodulation, this margin is freed in the FW of the proposed hybrid MPC by sequential optimization. In addition, hybrid VVs are used in the proposed MPC. Two long VVs are used for αβ regulation per control cycle, which increases the torque-speed operation range, while two z1z2 virtual VVs are used for z1z2 regulation, which ensures high z1z2 harmonic suppression capacity. The VVs are selected based on voltage reference estimation for light computation burden, while their duty ratios are calculated by projected quadratic programming algorithm (QP) for the same reason. With the proposed hybrid MPC, wider torque-speed operation range and lower current distortion can be obtained, compared with the traditional MPC using virtual VVs. Finally, experiments are conducted to verify the feasibility and advantages of the proposed method.

DC-link capacitors are among the most critical components in traction inverters, with a high likelihood of failure. Effective condition monitoring (CM) of these capacitors is crucial for improving converter reliability and preventing catastrophic failures. This article presents a cost-effective and reliable methodology for evaluating the health state of film capacitors used as dc-link in traction inverters. The proposed approach uses a controlled discharge test to track capacitance variations over time, which can be used as an indirect indicator of the capacitor’s health state. Key advantages of this technique include the minimal additional component requirements for cost efficiency, strong noise immunity, and high precision. Furthermore, the proposed aging detection test can be fully automated without requiring the removal of the capacitor or modifications to the converter’s power stage. Experimental results are provided to validate the effectiveness of the proposed solution.

Due to much more available voltage vectors (VVs), dual-three-phase (DTP) permanent magnet synchronous machine (PMSM) drives are more challenging in selecting the VVs than single-three-phase (STP) ones. The model predictive control (MPC) based on synthetic VVs is an excellent solution. However, its torque-speed operation range and harmonic suppression capacity at high speed are limited by the utilized synthetic VVs. In this article, the MPC based on long (L) and medium-long (ML) VVs is proposed for DTP PMSM drives, which uses L and ML VVs directly instead of using them to construct synthetic VVs. A restraint strategy based on voltage estimation is designed to reduce the range of VV candidates and computation burden. A selection strategy based on cost functions is developed for the optimal L and ML VVs. In addition, it is verified that the optimization model for duty ratio calculation in the proposed MPC is convex. Thus, the projected quadratic programming (QP) algorithm, used in the STP drives, can be extended and used for duty ratio calculation in the proposed method, with which faster calculation than the discrete enumeration is achieved. Furthermore, it is verified that the QP algorithm is also suitable for other MPCs for DTP PMSM drives whatever VVs are used. By using the L and ML VVs directly, the proposed MPC can not only obtain a wider torque-speed operation range than MPC based on synthetic VVs but also realize lower current THD at high speed. Finally, experiments are conducted to verify the feasibility and advantages of the proposed method.

The concept of asymmetric magnetic pole (AMP) has been developed to further improve the torque density of interior permanent magnet (IPM) machines. Compared with the conventional IPM machine, the AMP-IPM machine exhibits different operating characteristics in different rotating directions due to its unique magnetic-field-shifting (MFS) effect. Therefore, this article investigates the operating characteristics of AMP-IPM machine with aligned magnet and reluctance torques. To obtain the torque-speed relations, the maximum torque per ampere (MTPA) control method is studied. It shows that the MTPA trajectory obtained from AMP-IPM machine mathematical model is straight, which significantly simplifies the control efforts. On this basis, the torque-speed curves over the entire operating region are then analytically derived and compared, which indicate that AMP-IPM machine in low-speed region exhibits large peak torque in forward direction, while the machine in reverse direction is suitable for wide-speed range operation. Besides, the electromagnetic performances of the AMP-IPM machine are compared with those of the conventional IPM machine to further highlight the particular impact of MFS effect. The experimental results on an AMP-IPM prototype are obtained to verify all the theoretical analyses.

Inductance asymmetries introduce the 2nd-order harmonic estimated position error in the high-frequency (HF) signal injection (HFSI) sensorless control. To address this issue, a novel anti-rotating d-axis signal injection-based compensation method is proposed. The anti-rotating d-axis rotates in the opposite direction to the estimated d-axis at the same frequency, and its initial phase relative to alpha-axis depends on inductance asymmetry level. An additional HF voltage signal with the same injection frequency and injection phase as the one for position estimation but with an asymmetry level dependent amplitude is injected into the anti-rotating d-axis, generating a compensation signal to cancel the 2nd-order harmonic error in the demodulated HF current response. Two online estimators are established to determine the inductance asymmetry dependent initial phase of the anti-rotating d-axis and the amplitude of the injected voltage signal, respectively. It is also proved that these two parameters are almost independent of load and speed and thus can be fixed after estimation. Hence, acting as a feedforward control, the proposed method achieves a fast dynamic performance. Experimental results confirm that the proposed method effectively reduces the 2nd-order harmonic position error under both dynamic and steady-state conditions.

The feasibility of utilizing multiphase machines in electrical vehicles (EVs) is investigated in this paper by designing three-phase, five-phase, six-phase, and nine-phase interior permanent magnet synchronous machines (IPMSMs) with the same sizing parameters as the Tesla Model 3 IPMSM which is used as a reference. The optimized three-phase machine results in a 20% higher average output torque per permanent magnet (PM) volume compared to the reference design. Multiphase machines show 3-5% higher torque per PM volume over their three-phase counterpart while achieving inherently low torque ripples. The torque-speed analysis of the multiphase machines demonstrates enhanced efficiency regions attributable to the increased output power although this improvement is accompanied by increased iron losses due to high winding factors of harmonics. PWM losses are calculated, and thermal simulations of the machines are performed to validate that the designs work with thermal limitations. It is also shown that the DC-link capacitor size can be reduced by up to 55% compared to a three-phase system by using a multiphase structure. The total number of power switches used in the drive remains the same for the six-phase machine since the lower phase currents can be achieved by increasing the number of phases. The cost analysis for each of the machines has shown that multiphase machines are not necessarily more expensive than three-phase machines since the same total number of switches considering paralleled switches in three-phase machine can be used in six-phase machine while having smaller DC-link capacitors and PM volume. As a result, 14.2% higher output power per cost can be achieved compared to the reference design.

One of the main contributors to global greenhouse gas emissions is the public transportation sector. The streamlined operation of heavy-duty vehicles in this area is crucial for improving energy efficiency. Focusing on heavy-duty battery electric vehicles (BEVs), this paper proposes to add a hybrid energy storage system (HESS) to support the batteries and extend their lifespan by adding supercapacitors and fuel cells. By implementing advanced energy management strategies (EMS) in the HESS, such as a fuzzy logic controller (FLC) and an adaptive neurofuzzy inference system (ANFIS), the power distribution between the energy sources can be optimized. This study highlights the adaptability of ANFIS in handling nonlinear relationships among power demand, battery state of charge (SOC), and vehicle mass while addressing its changes due to dynamic passenger loads. An analysis is conducted between the ANFIS-based EMS and FLC-based controller, as well as with the baseline BEV model without HESS. Results demonstrate that the HESS equipped with the ANFIS controller improves power distribution and minimizes battery stress during the reference driving cycle by reducing the root mean square (RMS) of battery C-rate. Specifically, ANFIS achieves reductions of approximately 3% and 7% when compared to the FLC, with vehicle masses of 14036 kg and 15072 kg, respectively, which correspond to different passenger loads. This reduction in the RMS of the battery C-rate, a critical factor influencing battery lifespan, will benefit heavy-duty vehicles in public transportation systems in the long term. These findings underline the optimization capability of the ANFIS controller to enhance the power delivery of electric heavy-duty vehicles with HESS under dynamic operating conditions.

Multi-sector motor drive systems are increasingly crucial in applications that demand high power and reliability. Stator phase resistance can identify faults such as poor stator winding connection and overheating, making online resistance monitoring effective for assessing motor condition and predicting faults. This paper proposes an online resistance monitoring method for multi-sector motor utilizing DC current injection. The method can accurately detect stator resistance in each phase and reduces torque pulsation post-injection through coordinated injection among multiple sectors. The proposed method holds significant value for assessing the condition and early fault warning of multi-sector motors, and its effectiveness has been validated through experiments.

Capacitor monitoring plays a crucial role in evaluating inverter health. Traditional methods frequently require additional sensors or system operation adjustments. In this paper, we propose an online technique for monitoring capacitor, which relies on finely tuned duty cycles for 3L-Neutral-Point Clamped(NPC) inverter driven open winding multiphase motor systems. This strategy leverages the benefits of multiphase and multilevel systems, eliminating the need for additional sensors and minimizing potential impacts on output performance. The validity of the proposed method as demonstrated by experiments.

For decades, although plenty of work has been done on modulation of the fundamental voltage component for five-phase systems, the research on modulation algorithm and modulation capability of the third-harmonic component in five-phase systems is very less. In this article, the third-harmonic component modulation capability of five-phase motor drive systems is first analyzed. It is found that the third-harmonic modulation capability of the existing modulation algorithm is very limited, which may affect the suppression or utilization of the third-harmonic voltage/current in five-phase systems. To improve the third-harmonic modulation capability, a novel near-six-vector space vector pulsewidth modulation (NSV-SVPWM) method is proposed. It is proved that the widely applied four-vector space vector pulsewidth modulation (NFV-SVPWM) is a special instance of the proposed NSV-SVPWM, and the proposed NSV-SVPWM has more candidate voltage vector combinations than those of the conventional NFV-SVPWM. Thus, a better modulation capability can be achieved by the proposed NSV-SVPWM. The analysis and the effectiveness of the proposed algorithm are proved by experiments. The purpose of this article is to clarify the issues suffered by the existing modulation algorithm and do some improvements.

This paper proposes a novel finite-set model predictive current control (FS-MPCC) method for variable flux memory machine (VFMM) drives with a three-stage optimization strategy. A geometric modulation method is proposed for the sake of extending the control set, by which, the number of options is extended from 7 to 193. In order to reduce the computation burden, a three-stage optimization strategy is proposed, which is composed of three parts, i.e. determining the sector, narrowing the targeted range and selecting the optimum vector. By the proposed strategy, only 9 vectors are associated with the current prediction and the cost function calculation. On this basis, a duty-cycle solving algorithm is utilized to further improve the steady-state performance of the investigated VFMM. Finally, simulation results are presented to verify the proposed method.

In response to the time-consuming calculation of eddy current losses in 3D finite element analysis (FEA) and the unclear relationship between eddy current losses and machine parameters, an analytical calculation model is proposed for eddy current losses in permanent magnets (PMs) caused by stator slotting. The magnetic flux density variation and distribution of eddy current losses inside PMs corresponding to the position of stator slots are studied. Additionally, to reduce eddy current losses in PMs and mitigate the increased manufacturing costs associated with complete magnet segmentation (CMS), a single-side partial segmentation (SSPS) method is proposed to weaken PM eddy current losses. Finally, the effectiveness of the proposed approach is validated through prototype experiments.

Inter-turn fault is a serious stator winding short-circuit fault of permanent magnet synchronous machine (PMSM). Once it occurs, it produces a huge short-circuit current that poses a great risk to the safe operation of PMSM. Thus, an inter-turn short-circuit fault (ITSCF) diagnosis method based on high frequency (HF) voltage residual is proposed in this paper with proper HF signal injection. First, the analytical models of PMSM after the ITSCF are deduced. Based on the model, the voltage residual at low frequency (LF) and HF can be obtained. It is revealed that the HF voltage residual has a stronger ITSCF detection capability compared to the LF voltage residual. To obtain optimal fault signature, a 3-phase symmetrical HF voltage is injected into the machine drive system, and the HF voltage residuals are extracted. The fault indicator is defined as the standard deviation of the 3-phase HF voltage residuals. The effectiveness of the proposed ITSCF diagnosis method is verified by experiments on a triple 3-phase PMSM. It is worth noting that no extra hardware equipment is required to implement the proposed method.

The symmetrical CLLC-type dc transformer (DCT) has been widely adopted in dc microgrid for its high-power density and outstanding bidirectional power transfer capacity. However, the practical values of the inductors and capacitors in the circuit may fluctuate because of variations of temperature and power, which results in some challenges for the parameter design of the CLLC-type DCT to meet the following two design requirements. First, the CLLC-type DCT is expected to maintain stable when it is cascaded with a constant power load (CPL) even if its output impedance is affected by fluctuating values of inductors and capacitors. Second, the CLLC-type DCT is expected to maintain satisfactory power efficiency even if the inductors or capacitors fluctuate. To meet both design requirements, cascaded system stability and satisfactory power efficiency, this article proposes a four-stage particle swarm optimization (PSO)-aided parameter design approach for the CLLC-type DCT which fully considers the unpredictable fluctuations of practical inductors and capacitors. With this proposed approach, even if the values of inductors or capacitors fluctuate, the CLLC-type DCT can work stably when it is cascaded with CPL and meet power efficiency requirement. Finally, the effectiveness of the proposed four-stage PSO-aided parameter design approach has been experimentally verified.