In this paper, a new method for suppressing the common-mode voltage of current-source inverter (CSI) is proposed. The key innovation lies in applying a voltage-sensing voltage-compensation (VSVC) type active EMI filter to the CSI-based motor drive system. By utilizing the existing LC filter of the CSI, a common-mode active EMI filter is designed based on this structure, resulting in a combination of a differential-mode passive LC filter and a common-mode active EMI filter. This approach achieves sinusoidal voltage and current waveforms at the motor side, while ensuring that the motor-side common-mode voltage is near-zero. This not only improves the electromagnetic compatibility (EMC) performance of the drive system but also reduces motor insulation stress and bearing currents. Both simulation and experimental results validate the effectiveness of the proposed method.

In this paper, the modeling and mitigation method of torque ripple are investigated for permanent-magnet synchronous motor (PMSM). A new torque ripple model is proposed for three-phase PMSM based on general airgap field modulation theory. The mapping relationship between the torque order and the current order has been revealed. The qualitative and quantitative relationship between the stator harmonic current and torque ripple is established directly without other intermediate variables. The phase and amplitude of the torque component are found to be proportional to the phase and amplitude of the injected harmonic current. Therefore, only a few constant coefficients are required by finite element analysis (FEA) simulation. With the proposed torque model, directional mitigation of torque ripple can be realized by harmonic current injection method with low computational burden by FEA. Repetitive control is employed for harmonic current injection. FEA simulation and experimental results at different operating conditions verify the validity of the proposed torque model and ripple mitigation method.

Natural fault-tolerance performance is becoming popular for dual three-phase permanent magnet synchronous motors (PMSMs) under open-phase fault, as it eliminates the need for control structure reconfiguration and fault diagnosis. Unlike the current constraint imposed by the open-phase fault, little attention has been given to the voltage relationship between the inverter and the motor. In this paper, aiming to address the voltage disturbance by this constraint, an improved universal control scheme has been proposed for dual three-phase PMSM under single open-phase fault. The voltage disturbances have been modelled as dc-type and periodic-type, and then the low-passing filter plus resonator-based disturbance observer has been utilized in control scheme of torque subspace for improving disturbance rejection. The simulation and experimental results are presented to illustrate the effectiveness of the proposed method.

The high-frequency switching of PWM converters generates the common-mode voltages at high frequencies, which may pose a risk to the system. In this paper, two common mode voltage (CMV) suppression methods are proposed for the six-phase permanent-magnet synchronous motor (PMSM) drive system. The first method is based on the zero common mode voltage (ZCMV) vector and the finite-control-set model predictive control (FCS-MPC) scheme for the two-level inverter, which can suppress the common mode voltage of the system to near zero. However, the ZCMV modulation method tends to reduce the voltage utilization and modulation degree of the system. Moreover, when the voltage level of inverter is increased to more than two, the number of voltage vectors of this multiphase multilevel topology is extremely large. Therefore, for the special condition, which with the multilevel inverter at the high modulation region, another common mode voltage suppression method is proposed in the paper, which can effectively suppress the common mode voltage while keeping the voltage utilization nondecreasing and other dynamic and transient performance of the system basically unchanged. The validation of both methods is verified by simulations and experiments.

Conventional wireless power transfer (WPT) systems need bulky and unreliable dc-link capacitors to accomplish a two-stage power conversion in the primary side. In order to improve efficiency and reliability, this paper proposes a novel bidirectional WPT system for vehicle-to-grid (V2G) applications, which employs three-phase to single-phase matrix converter (TSMC) to convert the power from low-frequency grids to high-frequency coils directly. In contrast to existing matrix converter based systems, the proposed TSMC with space vector modulation (SVM) is capable of achieving power factor correction on the grid side and increased power levels with low device stress. A mathematical model is derived to show the amount and direction of power can be controlled by magnitude and relative phase angle shift of converters' voltages. The simulation on a 1.8kW bidirectional WPT system verifies the validity of the proposed WPT system and control strategy. Besides, a 60W laboratory prototype is developed for experimental verification.

An improved overlap-time distribution method is proposed for the grid-connected current source rectifier (CSR) in this paper. Due to the existence of the overlapping period during current commutations, input PWM currents and input voltages of CSR as well as grid currents become distorted with a number of low-order harmonics (mainly 5thand 7th harmonics), which seriously degrades the performance of the power system. To effectively eliminate the low-order harmonics introduced by the overlapping period, the dynamic distribution method of overlap-time has been presented for the grid-connected CSR. The overlap-time effect under different rectifier input voltages is analyzed, and the working principle of the proposed method is designed and given in details. Finally, the experimental results on a low power prototype are presented to verify the proposed method.

When an emergency happens to electric vehicles, the voltage of the dc-bus capacitor, which is an important part of the permanent magnet synchronous machine (PMSM) drive system, requires to be reduced as quickly as possible. Recently, a new idea of directly using the windings to discharge the capacitor has come forth. This paper proposes a physical energy flow model (EFM) to explain explicitly the winding-based discharge mechanism first. In the EFM, the performance characteristics of the classical winding-based discharge scheme are evaluated, but it is found that the discharge time will not be qualified when the machine rotor inertia is large and the system safe current is small. In order to reject intense voltage surge, a current control algorithm is proposed to bleed the capacitor voltage. Moreover, the proposed current control method shortens the discharge period to below 3 s for the system studied. The proposed discharge algorithm is verified by the experiment that is conducted on a three-phase PMSM drive system.

In this paper, a novel hybrid DTC scheme is proposed for asymmetric six-phase PMSM drives, which can achieve faster dynamic response of classical ST-DTC scheme and good steady-state performance of classical SVM-DTC scheme. The key is that a completely novel control strategy for torque and stator flux is designed. Different torque control methods are adopted under dynamic mode and steady-state mode without adding complexity of control algorithm. And a mode switching method is design to guarantee the smooth transition between the two modes. In addition, the proposed scheme can suppress current harmonics induced from inherent property of asymmetric six-phase motor effectively. Comparative experiments are carried out on a laboratory prototype to verify the effectiveness of the proposed scheme. The proposed hybrid DTC scheme applies equally to three-phase and other multiphase PMSM drives.

An optimized modulation based on model predictive control for current-fed dual active bridge converter achieving high efficiency in wide load range is proposed in this paper. The low voltage side switches can realize zero current switching by secondary clamping technique. The pulse width modulation of secondary side switches is encoded with instantaneous power. When in light load, the turn-on moment of high voltage side switches is decided by the calculation of model predictive control to avoid overlarge leak inductor current and reduce low voltage side RMS current. Through this method, the converter achieves higher efficiency in wide load range. Steady-state operation modes, analysis, simulation and experience results are presented in this paper. A 250W laboratory prototype is built to demonstrate the validity of the proposed modulation.

This paper is to study the control scheme for neutral-point-clamping three-level (NPC-3L) inverters fed dual three-phase permanent magnet synchronous motor (PMSM) drives based on vector space decomposition (VSD). The key is to propose a novel VSD based space vector modulation (SVM) strategy for the dual-three phase drives. The torque of the PMSM drive is controlled by voltage components on α-β plane while the current harmonics are suppressed by voltage components on x - y plane of the VSD-SVM. The upper and lower capacitor voltages are balanced well in DC link. Based on the proposed VSD-SVM strategy, a simple control scheme is presented for the dual three-phase PMSM drives. The principles of the proposed modulation strategy and control scheme are described in detail. The experiments are carried on a laboratory prototype to verify that the proposed VSD-SVM based control scheme can provide both good steady-state and dynamic performance for the dual three-phase PMSM drives.

An interleaved current-fed bidirectional full-bridge DC/DC converter for on-board Electric Vehicle (EV) charger is proposed in this paper. This proposed DC/DC converter interleaves two isolated full-bridge converters. In the forward direction power flow, it is an input-parallel output-series (IPOS) voltage-fed construct with the merits that low input current ripple and output voltage ripple. The IPOS construct can also decrease the current stress on the primary side devices and voltage stress on second side devices. In the reverse direction power flow, it is an input-series output-parallel (ISOP) current-fed construct with the merits low input voltage stress and low output current stress. It can realize zero current switching (ZCS) by second-side voltage clamping technique without snubber circuit. Moreover, the boost topology can decrease the turn ration of the transformer and lower the input current ripple. These merits make the bidirectional converter suitable for electric vehicles charging and driving mode. Operation equivalent circuits, analysis, simulation results are presented in this paper. A 3.3KW on-board EV charger prototype is built to demonstrate the validity of the proposed topology.

Compared with the traditional microgrid, a smart transformer (ST)-based microgrid shows advantages in terms of higher efficiency, increased hosting capacity, and enhanced reliability. However, this novel microgrid presents challenges because of the complex resonances within the system and the interactions between ST and power converter-based distributed energy resources (DERs). Both the ST and DERs might be severely affected by each other and leads to performance degradation and system instability. To solve these problems, this paper first develops equivalent circuits of a ST-based microgrid. Then, the resonance and interaction problems are investigated based on the equivalent circuits. The active damping method is used to fully address the resonance issue and mitigate the coupling effects. To guarantee superior performance, this paper also designs high-performance control strategies for both the ST and DERs. Simulation and experimental results are provided to verify the validity of the proposed control strategy.

The purpose of this paper is to design and implement the interleaved PWM and generalized control schemes for the paralleled grid converters. The key is to design the shifted angle among the PWM carriers of different grid converters, in such a way that the switching harmonics in the total grid current can be mitigated. By detecting and controlling the negative-sequence components in grid voltages and currents, the generalized grid synchronization and current controllers are designed to operate effectively under various grid voltage conditions, and thus ride through the short periods of grid faults. The laboratory prototype is setup, and the experimentation is given to verify the validity of the proposed interleaved PWM and the generalized control schemes.