Five-phase open-end winding permanent magnet synchronous motor (OEW-PMSM) fed by a dual inverter has gained increasing focus because of its advantages in voltage utilization, torque density and ...reliability. In this paper, an optimized modulation method with the sliding clamped strategy is proposed for the five-phase OEW-PMSM drive with a common DC bus. The conventional clamped strategies have a reduced switching sequence. However, the clamped inverter generates the zero-sequence voltage and third harmonic voltage, which would affect the performance of the motor. To solve this problem, the reference voltages in the proposed method are distributed by limiting the reference voltage of the clamped inverter on a line. And the reference voltage slides on this line bidirectionally. Therefore, the clamped inverter in the proposed method will not introduce additional harmonic components. For experimental verifications, the test results are presented with the resistance-inductance load and five-phase OEW-PMSM.
Multiobjective and multiload point design optimization of an interior permanent magnet (IPM) synchronous machine using a global response surface method to achieve low torque ripple with high average ...torque over the entire speed range is presented in this article. The approach consisting of a set of design steps and multiobjective optimization to obtain high-performance electric machines with optimum usage of rare-earth materials for mass production is presented. The design optimization has been applied to a 12-slot eight-pole IPM machine with two different rotor structures to arrive at the optimized design for a variable-speed high-performance application. Motor parameters are extracted under different load conditions to predict the torque/speed performance of the motors. The proposed design approach provides a machine design with maximized output torque, improved torque density, lower torque ripple, and optimum usage of rare-earth materials. Finally, the finite-element-based modeling results are validated with the experimental results.
This paper proposes a flexible active damping method for LCL-equipped high-speed permanent magnet synchronous motor. The damping ratio of the LCL resonance can be freely designed by the proposed ...high-order partial-state (virtual output voltage and the capacitor current) feedback. Moreover, a coefficient selection method is developed to complete the design of the damping system quickly and efficiently. As the main contribution, the proposal can easily apply to single-sensor (motor current feedback-only) applications to eliminate the sensor of the capacitor current with high parameter robustness. The experimental results of a 72kr/min test motor verify the stability and robustness of the proposed control strategy.
To evaluate reasons for non-fulfillment and ongoing contraceptive plans of patients who desired but did not receive inpatient postpartum permanent contraception (PC).
Multi-site retrospective cohort ...study of 1,254 patients with unfulfilled inpatient postpartum PC. We analyzed the reason for PC non-fulfillment, documented contraceptive plan, and method prescription or provision at hospital discharge, six-weeks, and one-year postpartum.
In our cohort, 44.3% of patients with unfulfilled inpatient PC did not receive any highly- or moderately-effective contraception within one year postpartum.
Removing barriers to PC fulfillment as well as contraceptive counseling that acknowledges these barriers is imperative.
We have grown Sm(Fe1−xCox)12 (x=0, 0.1 and 0.2) films epitaxially on V(001) buffered MgO(001) single crystalline substrates in order to investigate the intrinsic hard magnetic properties of the Co ...substituted SmFe12 phase with the ThMn12 structure. We found Sm(Fe0.8Co0.2)12 has excellent intrinsic hard magnetic properties with spontaneous magnetization of 1.78T, anisotropy field of 12T and Curie temperature of 859K, all of which are superior to those for Nd2Fe14B. Hence, the Sm(Fe0.8Co0.2)12 compound is promising as permanent magnet material, if it can be stabilized in a bulk form.
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Duty cycle model predictive torque control (Duty-MPTC) only uses zero vector as the second vector to form vector combinations, which restricts its torque control performance. This paper proposes a ...modified double vectors model predictive torque control (DVMPTC) by reasonably selecting active vector instead of zero vector. By analyzing the regulation of torque and flux of permanent magnet synchronous motor (PMSM), the torque and flux difference parameters are obtained, and then a second vector selection table is established to determine the best vector combination for torque ripple suppression. Based on the torque and flux difference parameters, the duty cycle calculation method is proposed to reduce the calculation burden of the control system. In order to verify the effectiveness of the proposed method, experiments with a 6-kW PMSM are carried out. Compared to the Duty-MPTC, the proposed DVMPTC method can significantly reduce the torque ripples with good dynamic performance and relatively low average switching frequency.
The conventional duty ratio modulation based direct torque control (DR-DTC) for the dual three-phase permanent magnet (DTP-PM) motor reduces the torque ripple using duty ratio modulation in torque ...control. However, the flux was controlled by a hysteresis comparator, resulting in deficient steady-state performance. This paper proposes a novel DR-DTC strategy to improve torque and flux simultaneously. Firstly, a switching table with the multiple vector selection is newly established. Two adjacent virtual voltage vectors and a null vector are selected in each control period. Then, the duty ratios of selected adjacent virtual voltage vectors are optimized with the dual objective modulation considering torque performance and flux performance. In addition, the combination of adjacent virtual voltage vectors for the DTP-PM motor generates non-standard symmetrical switching sequences. Two switching sequences generated methods are further investigated to address the issue. So, the switching sequences of the proposed strategy can also be generated easily. Finally, the conventional strategy and the proposed strategy are compared through experiments, and the experimental results verify the effectiveness of the proposed strategy.
Aiming at the problem of long computation time of finite element analysis (FEA) and poor calculation universality of existing analytical models, this paper proposes a general hybrid analytical model ...to predict the no-load and load performance of interior permanent magnet motors with any slot-pole combination, where the form of magnet can be V-shape, U-shape or flat-shape. The magnets are equivalent correspondingly according to the rotor structure in the modeling process and the motor can be divided into eight types of subdomains, the no-load and load magnetic field of the motors can be obtained by solving the equations established by boundary conditions, where the nonlinear of core is calculated by local MEC. The proposed model can be used to calculate the air-gap magnetic field, no-load back electromotive force, cogging torque and electromagnetic torque of IPM motors with different rotor topologies. The effectiveness of the proposed model is verified by both FEA and experiments. Compared with FEA, this model can consume less time with the acceptable accuracy, which brings convenience to the design and optimization of related types of motors.
This article proposes an effective stepwise nontransient method for entering and exiting the active short circuit (ASC) of permanent magnet synchronous motor (PMSM) to protect the safety of vehicle's ...drive system when fatal faults occur in the electric vehicles (EV) powertrain system with high motor speed. It is found that excessive transient current and overshoot voltage inevitably occur when ASC enters and exits directly, which may cause the demagnetization of permanent magnet and failure of motor controller unit (MCU). The two-phase short circuit is utilized as a transition step before entering and exiting three-phase ASC according to the rotor magnet position, and almost no transient current and overshoot voltage exist during the whole short-circuit period. Then, there are no constraints of ASC for system design and the system material cost can be reduced. This approach is useful for function safety implement of MCU for EV application with fast attenuation rate of transient current, high robustness, and limited resources requirement. The method with effective suppression of transient current and overshoot voltage is verified by the experimental results from a 15 kW PMSM test platform.
The current error is hard to avoid for finite control set model predictive current control (FCS-MPCC) in nine-phase open-end winding permanent magnet synchronous motors. To overcome this problem, an ...online virtual voltage vector (V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula>) synthesis strategy is proposed in this article. First, a group of V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula> s without harmonic voltage components are designed as the basic vectors for online synthesis. Then, two adjacent basic V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula> s and a zero vector are used to synthesize a new V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula>, which can output arbitrary amplitude and phase angle in the fundamental space. The two basic V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula> s are directly selected from the located sector of the predicted reference voltage vector (RVV), and their duration ratio can be simply calculated according to the angle of the RVV in the sector. In this way, the zero error is realized between the new V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula> and RVV. Moreover, an online pulse generation algorithm corresponding to the new V<inline-formula><tex-math notation="LaTeX">^{3}</tex-math></inline-formula> is proposed, which can calculate the symmetrical pulse sequences in real-time for the multiphase OW drive system without the space vector modulator. Finally, experimental results have verified the effectiveness and superiority of the proposed strategy, in comparison to existing FCS-MPCC in multiphase OW motor drive systems.
