http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Yingjie Wang,Lanyi Jiao,Bo Yang,Wenchao Wang,Haiyuan Liu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6
With power level of grid-connected converters rising, the switching frequency of the switching devices is commonly greatly reduced to improve its power capacity. However, this results in serious couplings of the dq current components, which leads to degradation of the static and dynamic performances of grid-connected converters and fluctuations of the reactive power in dynamic processes. In this paper, complex vector models under low switching frequency are established for an L/LCL grid-connected converter, and the relationship between the switching frequency and the coupling degree is analyzed. In addition, a series decoupling current control strategy is put forward. It is shown that the proposed control strategy can eliminate the couplings, improve the performances and have good robustness to parameter variations through static and dynamic characteristics analyses and a sensitivity analysis. Experimental and simulation results also verify the correctness of the theoretical analyses and the superiority of the proposed control strategy.
Yingjie He,Jinjun Liu,Zhaoan Wang,Yunping Zou 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1
Tracking harmonic current quickly and precisely is one of the keys to designing active power filters (APF). In the past, the current state feedback decoupling PI control was an effective means for three-phase systems in the current control of constant voltage constant frequency inverters and high frequency PWM reversible rectifiers. This paper analyzes in detail the limitation of the conventional PI conditioner in the APF application field and presents a novel PI control method. Canceling the delay of one sampling period and the misadjustment for tracking the harmonic current is the key problem of this PI control. In this PI control, the predictive output current value is obtained by a state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by a repetitive predictor synchronously. The repetitive predictor can achieve better predictions of the harmonic current. By this means, the misadjustment of the conventional PI control for tracking the harmonic current is cancelled. The experiment results with a three-level NPC APF indicate that the steady-state accuracy and dynamic response of this method are satisfying when the proposed control scheme is implemented.
Deadbeat Control with a Repetitive Predictor for Three-Level Active Power Filters
Yingjie He,Jinjun Liu,Jian Tang,Zhaoan Wang,Yunping Zou 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.4
Three-level NPC inverters have been put into practical use for years especially in high voltage high power grids. This paper researches three-level active power filters (APFs). In this paper a mathematical model in the d-q coordinates is presented for 3-phase 3-wire NPC APFs. The deadbeat control scheme is obtained by using state equations. Canceling the delay of one sampling period and providing the predictive value of the harmonic current is a key problem of the deadbeat control. Based on this deadbeat control, the predictive output current value is obtained by the state observer. The delay of one sampling period is remedied in this digital control system by the state observer. The predictive harmonic command current value is obtained by the repetitive predictor synchronously. The repetitive predictor can achieve a better prediction of the harmonic current with the same sampling frequency, thus improving the overall performance of the system. The experiment results indicate that the steady-state accuracy and the dynamic response are both satisfying when the proposed control scheme is implemented.
Yingjie Hu,Lu Xiong 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10
The accuracy of MEMS inertial sensors is affected by stochastic errors. The stochastic error of a MEMS inertial gyro consists of high frequency and low frequency components. Low frequency part is characterized by correlated noise and can be modeled by means of random process error model while the high frequency part cannot due to its white noise characteristics. An integrated method of wavelet de-noising and time series analysis is proposed in this paper: First, wavelet de-noising is employed to dispose of the high frequency noise and then time series analysis combined with Sage-Husa adaptive Kalman filter is utilized to eliminate the low frequency noise. An experiment using IMU ADIS16445 is conducted. Through Allan variance analysis, two main random noise parameters are notably diminished by almost 10 times. Results show that this proposed method is effective in suppressing MEMS gyro stochastic noise.
A Study on the DC Link Voltage Balancing for Power Conditioners based on Cascaded H-bridges
Yingjie He,DU Si-xing,LIU Jin-jun 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In medium and high power field, cascade multilevel converter has been paid more attentions to research and application. When the cascade multilevel converters compensate reactive power and harmonic current, the control of the floating capacitor voltage has been being a hot research topic. So far, DC bus voltage balance control method can be divided into two groups: circuit balance and algorithm balance. The latter one is preferable from both cost and other aspects. Based on layered control algorithm, this paper focus on the voltage balance fundament and analyzes the process of DC capacitor’s absorbing active power and releasing active power with the influence of converter’s output pulse voltage. Based on this fundament, a new control method, voltage vector trimming in the parallel direction, is introduced. Compared with other DC voltage balance control methods, this method has the advantage of improving efficiency of DC voltage. At last, the simulation based on the tools of matlab/simulink is made. The simulation result results indict that this DC voltage balance control method functions well.
EFFECT OF Cu ATOMIC SEGREGATION ON THE FROZEN STRUCTURES OF Co–Cu BIMETALLIC CLUSTERS
YINGJIE ZHANG,YONGQIANG LI,XUYANG XIAO,YUNHUI YAN 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.6
Atomic segregation in bimetallic clusters can in°uence the surface constituent and be used to a®ect the frozen structure. In this study, molecular dynamics simulation with an embedded atom method was used to study the frozen structures of (CoCu)561 clusters with di®erent Co contents. It is found that the clusters can freeze to form icosahedron, truncated octahedron, decahedron or hcp with the change of Co contents. In these geometries, the structure of the lowest energy state is hcp, then in turn decahedron and truncated octahedron. The frozen structures are related to the release of excess energy, while the released excess energy was a®ected by the amount of segregated Cu atoms. This means that the atomic segregation can be used to tune the structures of bimetallic clusters.
Yingjie He,Jinjun Liu,Jian Tang,Zhaoan Wang,Yunping Zou 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.2
In recent years, multilevel technology has become an effective and practical solution in the field of moderate and high voltage applications. This paper discusses an APF with a three-level NPC inverter. Obviously, the application of such converter to APFs is hindered by the problem of the voltage unbalance of DC capacitors, which leads to system instability. This paper comprehensively analyzes the theoretical limitations of the neutral-point voltage balancing problem for tracking different harmonic currents utilizing current switching functions from the space vector PWM(SVPWM)point of view. The fluctuation of the neutral point caused by the load currents of certain order harmonic frequency is reported and quantified. Furthermore, this paper presents a close-loop digital control algorithm of the DC voltage for this APF. A PI controller regulates the DC voltage in the outer-loop controller. In the current-loop controller, this paper proposes a simple neutral-point voltage control method. The neutral-point voltage imbalance is restrained by selecting small vectors that will move the neutral-point voltage in the direction opposite the direction of the unbalance. The experiment results illustrate that the performance of the proposed approach is satisfactory.
Yingjie Qian,정상영,진명종 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.6
A highly efficient and recyclable catalyst for Suzuki reaction.