Simplified model predictive current control strategy for open-winding permanent magnet synchronous motor drives

Zhu, Shengjie,Zhang, Housheng The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.6

For a semi-controlled open-winding permanent magnet synchronous motor, to improve the steady-state control performance of the traditional predictive control system and to concurrently lessen the computation burden, a novel model predictive current control strategy is proposed in this paper. First, to achieve simultaneous control of the d-axis current, q-axis current, and current error-based cost functions. Then, to further reduce the calculation burden and complexity of the prediction algorithm, the predicted voltage of the converter is used as the reference voltage. In addition, the judgment of the sector where the reference voltage is located, and the selection method of the voltage vector are also given. Finally, the effectiveness of the proposed prediction method is tested by the simulation and experimental results.

Simplified model prediction current control strategy for permanent magnet synchronous motor

Zhang, Housheng,Zhu, Shengjie,Jiang, Junjie,Wang, Qingzhuang,Wang, Ao,Jin, Duo The Korean Institute of Power Electronics 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.11

A simplified model predictive current control strategy based on mathematical auxiliary line method is proposed to increase the permanent magnet synchronous motor (PMSM) predictive current control system's steady-state performance while reducing the system's computational complexity. The mathematical models of current prediction, first-order compensation, and cost function are presented by analyzing the prediction current control strategy of the conventional models. Within a control cycle, the simplified model predictive current control algorithm applies two voltage vectors and omits the error calculation of cost function. The anticipated voltage of transformer obtained from the beat-free current control standard is considered the reference voltage, and the judgment of the area, where the reference voltage vector is found and the strategy for double voltage vector is selected, is put forward. The optimal voltage vector can be directly output without the error calculation of the cost function in the method, thereby effectively reducing the computation load and complexity of the system and improving the steady-state performance. Experimental results verify the validity and accuracy of the proposed simplified model of predictive current control strategy for PMSM control.

Unified coordinated control strategy for two parallel inverters TPOW‑PMSM system

Housheng Zhang,Shengjie Zhu,Duo Jin,Ao Wang,Junjie Jiang,Lanlan Yu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2

The three-phase open-winding permanent magnet synchronous motor (TPOW-PMSM) is generally used to drive electric vehicles. The voltage vector spatial distribution and fault-tolerant topological structure of a TPOW-PMSM system with two parallel inverters are analyzed in this paper. Then, based on the unified PWM modulation algorithm, a unified coordinated control strategy based on reference voltage vector 120º decoupling control is proposed. The speed and current double closedloop control systems of two parallel inverters are designed, and a PI + repetitive controller of the speed loop is designed to realize fast and stable speed control. The realization process does not require sector judgment or table lookup calculations, and the switching time of each bridge arm switch tube is determined by the instantaneous value of the three-phase voltage of the two parallel inverters, which simplifies the control algorithm. Experimental results show that the unified coordinated control strategy with the PI + repetitive controller can control the normal operation of a TPOW-PMSM, and realize smooth and reliable transitions from the normal operation state to the fault-tolerant operation state. The proposed unified coordinated control strategy with the PI + repetitive controller effectively suppresses the instantaneous value of system zero-sequence current, and inhibits the influence of the dead zone effect.

Effect of Annealing on the Microstructure, Texture and Tensile Deformation Properties of Cu–3 wt%Ag–0.5 wt%Zr Thin Sheets Rolled at Room and Cryogenic Temperature

Peng Zhang,Han Wang,ShengJie Yao,ChuanJie Wang,Qiang Zhu,Gang Chen 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.2

The Cu–3 wt%Ag–0.5 wt%Zr are rolled with the same reduction process at room (RT) and cryogenic (CT) temperature,respectively. The electron backscatter diffraction and transmission electron microscope are used to analyze and comparethe evolutions of material microstructure and texture. The results show that the stability of as-rolled CT sheets is differentfrom that of the RT samples, which can be verified by the lower temperature for the occurrence of recrystallization andAg-base particles precipitation. Besides the Brass, Copper and S textures which are exhibited in the two kinds of as-rolledsheets, there are also Q and P texture components in the as-rolled CT sheets. The constitutive equation basing on evolutionof dislocation mean free path (L) and dislocation cell size (dDC) with plastic strain indicates that the initial values of L, dDCand mobile dislocation density (ρm) are associated with annealing condition closely. Furthermore, the strain ranges of thestable and instable plastic deformation are related to the degree of recovery and recrystallization.

Investigation of the concentration characteristic of RCS during the boration process using a coupled model

Chi Xiangyu,Li Shengjie,Gu Mingzhou,Li Yaru,Zhu Xixi,Wang Naihua 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8

The fluid retention effect of the Volume Control Tank (VCT) leads to a long time delay in Reactor Coolant System (RCS) concentration during the boration process. A coupled model combining a lumpedparameter sub-model and a computational fluid dynamics sub-model is currently used to investigate the concentration dynamic characteristic of RCS during the boration process. This model is validated by comparison with experimental data, and the predicted results show excellent agreement with experimental data. We provide detailed fields in VCT and concentration variations of RCS to study the interaction between mixing in VCT and the transient responses of RCS. Moreover, the impacts of the inlet flow rate, inlet nozzle diameter, original concentration, and replenishing temperature of VCT on the RCS concentration characteristic are studied. The inlet flow rate and nozzle diameter of VCT remarkably affect the RCS concentration characteristic. Too-large or too-small inlet flow rates and nozzle diameters will lead to unacceptable long delays. In this work, the optimal inlet flow rate and nozzle diameter of VCT are 5 m3 /h and 58.8 mm, respectively. Besides, the impacts of the original concentration and replenishing temperature of VCT are negligible under normal operating conditions.

On Which Microphysical Time Scales to Use in Studies of Entrainment‐Mixing Mechanisms in Clouds

Lu, Chunsong,Liu, Yangang,Zhu, Bin,Yum, Seong Soo,Krueger, Steven K.,Qiu, Yujun,Niu, Shengjie,Luo, Shi American Geophysical Union 2018 Journal of Geophysical Research: Atmospheres Vol.123 No.7

<P>The commonly used time scales in entrainment-mixing studies are examined to seek the most appropriate one, based on aircraft observations of cumulus clouds from the RACORO campaign and numerical simulations with the Explicit Mixing Parcel Model. The time scales include the following: (evap), the time for droplet complete evaporation; (phase), the time for saturation ratio deficit (S) to reach 1/e of its initial value; (satu), the time for S to reach -0.5%; and (react), the time for complete droplet evaporation or S to reach -0.5%. It is found that the proper time scale to use depends on the specific objectives of entrainment-mixing studies. First, if the focus is on the variations of liquid water content (LWC) and S, then (react) for saturation, (satu) and (phase) are almost equivalently appropriate, because they all represent the rate of dry air reaching saturation or of LWC decrease. Second, if one focuses on the variations of droplet size and number concentration, (react) for complete evaporation and (evap) are proper because they characterize how fast droplets evaporate and whether number concentration decreases. Moreover, (react) for complete evaporation and (evap) are always positively correlated with homogeneous mixing degree (); thus, the two time scales, especially (evap), are recommended for developing parameterizations. However, and the other time scales can be negatively, positively, or not correlated, depending on the dominant factors of the entrained air (i.e., relative humidity or aerosols). Third, all time scales are proportional to each other under certain microphysical and thermodynamic conditions.</P>

Two‑vector predictive current control strategy based on maximum torque per ampere control for PMSMs

Duo Jin,Housheng Zhang,Shengjie Zhu,Ao Wang,Junjie Jiang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.8

In permanent magnet synchronous motor systems with double closed-loop maximum torque current ratio control, a PI adjuster is used as the current inner ring. Unfortunately, the current may not be tracked effectively due to controller saturation when the load suddenly changes. To counteract this effect, a novel two-vector predictive current control strategy based on maximum torque current ratio control is proposed in this paper. The control strategy introduces the model predictive current control of two voltage vectors based on maximum torque per ampere control, which is acted upon by two voltage vectors in one control period. The second selected vector is no longer limited to the null vector. The orientation and amplitude of the synthesized virtual voltage vector are adjustable. Simulation results indicate that the proposed control method has the advantages of maximum torque per ampere control and model predictive control. It optimizes the stability of the system and reduces the fluctuation of the stator current.

One-pot synthesis of electron-acceptor composite enables efficient fullerene-free ternary organic solar cells

Zhang, Jianyun,Liu, Wenrui,Chen, Shanshan,Xu, Shengjie,Yang, Changduk,Zhu, Xiaozhang The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.45

<P>An effective strategy of “synthesizing an electron-acceptor composite (ZITI-m) by one-pot reaction” to improve photovoltaic performance is proposed. The ZITI-m composite is synthesized by one-pot Knoevenagel reaction of ZIT-2CHO and a mixture of INCN-2F and I-a, from which asymmetrical ZITI-3F and symmetrical ZITI-4F are separated. J71:ZITI-m-based OSC shows the highest PCE of 13.65 ± 0.13% with remarkable PCE of 13.85% than those based on J71:ZITI-3F (12.97 ± 0.15%) and J71:ZITI-4F (13.02 ± 0.13%) blends. The effect of acceptor ratio in the composite on OPV performance indicates that all PCEs of composite system are higher than those of the materials based on pure acceptors with a broad composition tolerance, which is ascribed to the synergistic effect of the ternary blend system.</P>

Cathode interfacial layer-free all small-molecule solar cells with efficiency over 12%

Wu, Hao,Yue, Qihui,Zhou, Zichun,Chen, Shanshan,Zhang, Dongyang,Xu, Shengjie,Zhou, Huiqiong,Yang, Changduk,Fan, Haijun,Zhu, Xiaozhang The Royal Society of Chemistry 2019 Journal of materials chemistry. A, Materials for e Vol.7 No.26

<P>While nonfullerene small-molecule solar cells (NF-SMSCs) have relatively inferior performance compared with nonfullerene polymer solar cells, their performance is improving. In this work, a weak crystalline molecular donor BSFTR, was designed and synthesized to achieve efficient NF-SMSCs. By blending with a strong crystalline acceptor NBDTP-Fout, BSFTR achieves a well-intermixed blending morphology, which favors the formation of efficient charge percolation pathways with suppressed recombination. The BSFTR:NBDTP-Fout device obtains a power-conversion efficiency (PCE) of approximately 11.97% by achieving an efficient cathode interfacial layer (CIL)-free device that delivers an even higher PCE of 12.3%, which ranks among the top values for the reported NF-SMSCs. This work provides a simple solution for achieving high-performance NF-SMSCs by identifying the key factors for designing efficient, cost-saving, mass production-favorable CIL-free organic photovoltaic devices.</P>

Predictive direct torque control of permanent magnet synchronous motors using deadbeat torque and flux control

Ao Wang,Housheng Zhang,Junjie Jiang,Duo Jin,Shengjie Zhu 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.2

In consideration of the shortcomings of the large torque and flux ripples in direct torque control (DTC), and the insufficient utilization of the duty cycle module in traditional DTC based on the duty cycle modulation of PMSMs, a DTC method based on deadbeat control of the torque and flux is proposed in this paper. In the synchronous rotation, coordinate system positioned with the stator flux vector, the reference voltage vector is calculated in accordance to the deadbeat control method. Six virtual voltages are constructed in such a manner that two adjacent basic voltage vectors are evenly divided in one control cycle. The effective voltage vectors are expanded to 12. The effective voltage vector closest to the phase angle of the reference voltage vector is determined to be the optimal voltage vector. Then, the duty cycle is introduced to further reduce the error between the final output voltage vector and the voltage vector required by the system. Simulation comparisons are carried out for DTC, traditional DTC based on duty cycle modulation, and the proposed DTC. The obtained simulation results demonstrate that the proposed DTC can effectively suppress both torque ripple and flux ripple, improve the utilization rate of the duty cycle module, and reduce the stator current distortion rate.