Dual mode AC DC AC converter for contactless power transfer system

A new type AC DC AC converter which can work in Buck or Boost mode is proposed in order to overcome the deficiencies of the primary circuit of the traditional contactless power transfer system. Through switching this two modes and turning the duty cycles of the switches, not only the resonant current amplitude of the primary resonant current can be controlled to be constant against a wide range variation of input voltage, but also the problems, such as surge current, high cost, complex control etc., caused by the DC filter and DC/DC converter in a traditional CPT system are effectively eliminated. The topology and operation principle of the proposed converter have been analyzed. The corresponding control strategy has been presented and verified by simulation results.     

Circulating current control method for inductive power transfer system

Inductive power transfer (IPT)technology allows electrical energy to be transferred between two loosely coupled inductors over relatively large air gaps based on electromagnetic induction. In current-fed IPT systems,resonant capacitor voltage distortions and current spikes on the semiconductor switches are easily caused when switches isn’t switched at zero crossing point of resonant voltage. As a result,the EMI level of the system and the switching loss are increased and thus the system transmission stability and efficiency decrease. The article analyzes the production mechanism of circulating current in load resonant high frequency inverter and points out that the resonant frequency change is the real cause. By analyzing the characters of circulating current before and after the zero-crossing points of resonant voltage and relationship between switching frequency and resonant frequency,this paper proposes a method of real-time detection for the direction of circulating current,and regulating the switching frequency in accordance with resonant frequency dynamically to ensure the switching of switch tubes at the zero-crossing points of the resonant capacitor voltage,and thus to inhibit circulating current. An experiental system with the platform of FPGA is set up to verify the effectiveness of this control method.     

Direction analysis on Contactless Power Transmission System

After analysis on the direction relationship betueen primary side and secondary side of existing contactless power transmission system, a random rotatable pick-up is proposed. Two connecting modes of three orthogonal wound coils are studied. Based on analysis and mathematical calculation, instantaneous output voltage and its ratio to the maximal and minimal value when the pick-up rotate in three-dimensional space is given. All the calculation is verified by experiment results.     

Study on constant current control of inductive power transfer with parameter identification

Aiminy at magnetic exciting current (resonant current) control, a constant current control method based on dynamic parameter identification is put forward. With energy conversion analysis, the energy storage, supply and dissipation functions of the system resonant network are constructed. The reflecting impedance identification functions are obtained by constructing the energy equilibrium relations in a period and among several periods. Furthermore, a constant current control strategy by regulating the system input voltage with Buck converter is presented. Combining the relations among system input voltage, the envelope of resonant current and the input of Buck converter, the constant current control law is proposed. The control law is verified with experiments. For the proposed method, in parameter identification, only the data of zero crossing point of resonant voltage and current are required, which reduces the complexity and costs of sampling system. Also, the constant current control law does not need complex computation and is easy to implement.     

Modeling and control of An LCL bi-directional inductive power transfer system

Since there exist high-frequency switching networks and complicated operating modes in bi-directional inductive power transfer (IPT) system, it is easy to result in high harmonics and EMI interference. An LCL filter network is introduced to effectively filter out the unwanted harmonics in track current and reduce EMI interference. Based on a mathematical model of the power transmission established by complex analysis of the AC variables, under the condition of maximum transmission efficiency, the phase angle differences between the primary input voltage and secondary output voltage U·so are ±90° and the energy is respectively transferred in forward or backward direction. Moreover, the power magnitude can be controlled by adjusting the modulus of U·pi and U·so. In addition, to keep the track current constant, different phase-shifting control strategies are designed in the primary and secondary parts. Simulation and experimental results show that these strategies can not only adjust track current to keep constant but also dynamically change the direction and magnitude of power transmission according to the working conditions and actual needs of the system load to improve the system operating efficiency.     

Novel Power Supply Method and Technology Analysis for Electrified Monorail System

The problems of industry monorail conveying system brought by tradition physical contact such as irregular contact spark, carbon laydown and unsafe, narrow the area which the material handling system can apply to in awful industry environment, e.g. forge, cleaning, lacquering. A novel monorail power supply method based on electromagnetic coupling theory is presented. Discussions are made on several problems such as frequency selection, load control, efficiency elements and harmonic effects at the same time. Moreover, solutions are brought about according to them. The monorail application of this technology provides clean, stable and safe power supply, and immunes to environment interference such as dust, water as well.     

Analysis of Loosely Coupled Inductive Power Transfer System

In LCIPT system, the selection of system operation frequency has a relationshi Pwith the cost and power transfer capability of the power supply. Due to the development of Power device and system efficiency requirement , it is restricted to increase the system operation frequency . This paper presentes a topology which transfers power through LC oscillation. When the voltage of the capacitor is less than reference voltage, the switch is turned off and the capacitor is charged, which makes the switching frequency far less than the syntonic frequency. Thus the system efficiency is improved, and the system cost is reduced. This is verified by the time domain and frequency domain simulations of Saber. This topology not only can be used in LCIPT, but also in other convertors.     

A New Algorithm for Open Conductor Faults in Power Systems with Variable Structures

A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples.     

A combined regularization algorithm for three-dimensional electrical impedance tomography system

By studying the reconstructed algorithms of Tikhonov regularization and the Newtons one-step error reconstructor (NOSER),a combined regularization algorithm is proposed. Two evaluation parameters of reconstructed algorithms,i.e. normalization mean square distance criterion(NMSD)and normalized mean absolute distance criterion(NMAD)are used to evaluate the results precision of inverse problem quantificationally. The comparison among Tikhonov regularization,NOSER and the combined regularization shows that the ill-condition and error of inverse problem are reduced. This new algorithm can decrease the condition number by 97%,NMSD by 51% and NMAD by 41% at least. Simulate results show that the combined regularization algorithm can reconstruct the target image in the depth from 10 mm to 40 mm. The performance of this system and the combined regularization algorithm demonstrate significantly better spatial resolution and less reconstructed error.     

Filtering Method for the Decomposition of Heart Rate Variability Power Spectral

Heart rate variability is a convenient tool to study the autonomic nervous system of human body. It is a focus of studying cardiovascular disease in clinic. The main spectral components are distinguished in the heart rate variability spectrum: ultra low frequency(ULF),very low frequency(VLF), low frequency(LF), high frequency(HF) components .While different part has different physiological meaning. This paper discusses the design of an effective digital filter for heart rate variability power spectral analysis,which provides a scientific measure of heart rate variability power spectral analysis in further studies and clinical applications.     

改进粒子群算法的自动阻抗匹配技术

由于无线电能传输距离的改变或谐振线圈之间发生偏移、负载改变等多方面的影响使系统的输入阻抗发生变化,导致输入阻抗与射频源内阻不匹配,使传输效率大幅下降。在射频源和发射线圈之间加入阻抗匹配网络可以提高无线电能的传输效率。为了提高阻抗匹配的精度和速度,提出了一种改进的粒子群算法。重点将改进算法和传统算法进行仿真实验比较,证明了改进算法在匹配精度和速度方面的优越性。最后将该算法嵌入到自动阻抗匹配系统中,提高了无线电能的传输效率,同时证明了所提算法的有效性。     

Overall control strategy and operational performances of a doubly fed wind turbine generator system

In order to comprehensively and correctly analyze the real-time operational characteristics of a grid-connected wind turbine generator system, it is necessary to analyze the overall control strategies and operation performances of the wind turbine generator system. According to the type of a doubly fed wind turbine generator system, the mathematical models of wind turbine, drive train and doubly fed induction generator (DFIG) are presented. From the viewpoints of the maximum wind energy capture and safe operation of the wind turbine, a maximum power output control strategy is proposed by considering the DFIG loss minimization, and a variable pitch control strategy is also presented by considering generator rotational speed restriction and the output power restriction. Combined with a power decoupling strategy of DFIG, the overall operational performances of the doubly fed wind turbine generator system are simulated. By comparing the simulation, theoretical analysis and actual operational data, the results show that the presented model and overall control strategies of the doubly fed wind turbine generator system are valid.     

Power model and tarepower characteristic of CNC machine tool feed system

A power model of a CNC machine tool feed system is proposed based on analyzing the power characteristic of each component in the CNC machine tool feed system. And the tarepower characteristic and its dominant affecting factors are analyzed by using the power model. The analysis results show that the tarepower of feed system is a monotone increasing quadratic function in term of the feed speed. Meanwhile, the feed speed and load mass both affect tarepower, but the influence of load mass is minuteness. Some experiments are conducted on a 3-axis CNC milling and the experimental results justify the theoretical analysis.     

Stratification transfer model for predicting complex mining subsidence

Based on the new probability integral 3D model for forecasting the solution mining subsidence, the transfer rule of superincumbent strata in mining subsidence is studied and a prediction model of stratification transfer for mining subsidence is developed. The model can take into account of the impacts of features of different rock strata on mining subsidence and improve prediction precision of irregular goaf. Based on the situation that it’s hard to get the analytical solution of the model with triple integral, the numerical algorithm of the model is supplied. With the superposition principle theory, a prediction model of multi cavern mining subsidence is developed. With the application in ground subsidence prediction of oil gas storage in Jintan, it proves that the transfer prediction model holds higher precision than those of traditional models     

LCL型CPT系统的参数设计方法及频率特性分析

以金鲳鱼为原料,固定小麦粉与水的质量比为2∶1,食盐添加量2%,微波真空度0.095 MPa,在单因素试验的基础上,通过正交试验对微波真空技术膨化鱼糜饼工艺条件进行优化。结果表明,鱼糜饼制作的最佳工艺条件为:鱼糜含量35%,膨化温度100℃,膨化时间20 min,鱼糜饼厚度2 mm,在该工艺条件下,制得的膨化鱼糜饼色泽金黄、质地酥脆、风味清香,成品膨化率可达到540%。     

A Predictive Method of Index on Power Consumption in a Resident Unit

In this paper, a series of data on power consumption and the numbers of household appliance in a resident unit of a district, were analyzed by regression technique. A curve of the index on power consumption of a resident unit in a district has been gained. This curve was tested by another series of data obtained at the same time.     

An Improved Method of the Transient Waveform Analysis in Power Systems

The angular frequency and decaying constant of each copmonect for the transient waveform in power systems were obtained by using the discrete Fourier transform; the amplitude and phase angle were calculated in the linear curve fitting method. And all of the parameters obtained above were treated in an unified optimization by using the curve fitting optimization of the least square method of general nonlinear funcrion so as to get the results of waveform analysis. Two examples are included.     

The Stability Analysis of Single end Flyback Switching Power Supplies

Based on the research of a practical project for high hrequency high voltage switching power supplies,the state space average model as well as the transfer function of single end flyback converters,which can be used to analyze the stability of single end flyback switching power supplies,are established.     

An improved sliding mode reaching law for continuous-time system

The advantages and disadvantages of traditional reaching laws for continuous-time systems are analyzed and a new reaching law is proposed. The new reaching law is based on a piecewise region of switching function. When the absolute value of the switching function is greater than one,a type of reaching law is in action. Otherwise,the other one is in action. As a result,the reaching velocity of the system’s state trajectory is promoted further,while the advantages of exponential reaching law and power rate reaching law are reserved,i.e. chattering is restrained when system’s state trajectory approaches the switching surface while the entry is smooth. Finally,the simulation results based on a car-type inverted pendulum show the effectiveness of the proposed new reaching law.