双绕组异步风电机组同步化并网运行仿真研究

针对定子双绕组异步电机(DWIG)在并网运行条件下展开研究,通过对发电机的控制,使其在功率绕组侧输出稳定三相交流。借鉴同步发电机的运行控制策略,将有功-频率、无功-电压下垂控制方法移植到并网逆变器的控制中,使得逆变器有了频率与电压保持特性,从而在外特性上具有同步发电机的特征。提升了包括DWIG在内的整个风电机组并网运行性能,使其具备维持系统功率平衡、维持电网频率和电压稳定性等优点。有效缓解了风电大规模接入电网而对电网造成的不利影响。基于Simulink的仿真结果证明了系统和控制策略的正确性与有效性。     

A stable programming pulse generator for single power supply flashmemories

A stable programming pulse generator has been developed for single power supply, high-speed programming, and low-power flash memories. The newly developed delay circuit operates by amplifying the difference between the reference voltage and the capacitor voltage raised by the charging current which is proportional to the reference voltage. Linearity between the capacitor voltage swing and the driving current enables us to make the delay circuit supply voltage-, temperature-, and process-tolerant. Thus, the proposed delay circuit stably controls a programming pulse width through all operational ranges of supply voltage and temperature. The output frequency of the newly developed oscillator is inversely proportional to the supply voltage. This oscillator stably drives charge pump circuits which generate high programming voltages on chip since dependence of charge pump characteristics on frequency and supply voltage can be cancelled. As a result, the programming pulse generator including the delay circuit and the oscillator has reduced the total programming time under the slowest condition, i.e., high temperature and low voltage condition, by 30% and the power consumption under the fastest condition, i.e., low temperature and high voltage condition, by 20%, for a 3.3 V-only flash memory     

离网型斯特林异步发电技术研究

根据斯特林发动机和异步发电机的特点,采用串联结构的异步发电模式,通过三相PWM全桥变换器解决了离网型斯特林发电系统的起动和发电问题,实现起动／发电双功能,使功率双向流动。系统电机控制采用带端电压补偿的V／f控制策略,对蓄电池采用DC—DC桥臂进行独立控制,稳态时保持蓄电池缓慢充电,在负载突变时,蓄电池相应放出或吸收能量,缓冲发动机的能量调节过程。仿真和实际示范应用证明了本系统的正确性和可行性。     

Maximum power transfer between finite antennas

The optimum illumination for maximum power transfer between two opposed rotationally symmetric antennas is determined. The antennas have spherical surfaces and dissimilar apertures. Given an angular variation of the illumination ofcos (alpha theta), withalphaintegral, the optimum radial distribution becomes solutions of a finite Hankel transform.     

Wireless information and power transfer using single and multiple path relays

A relay‐based wireless communication model can relay information along with the power bidirectionally using the amplify‐and‐forward scheme. This paper studies such model extensively. Three information and power relaying protocols, that is, time‐based switching relaying, power‐based splitting relaying, and hybrid time switching‐based and power splitting‐based relaying (HTPSR) are used to carry forward bidirectional information and power transfer. First, a solo relay model is studied, for which, we derived a throughput expression for end‐to‐end information transfer, and this is done for all the three relaying protocols. The paper indicates that the system throughput depends upon the time switching and the power splitting ratio. Further, to make the system more reliable and robust, multiple relays are used in the path. Various relay selection schemes are used for path selection in each transmission, thereby yielding different throughput performances. The results show that an optimal throughput is obtained for a given relay location at an optimal set of values of splitting and switching ratio. Moreover, the HTPSR outperforms both the power splitting and time switching protocol in system throughput performance for a single as well as a multiple‐relay model. Whereas, in relay selection schemes, the best SNR selection scheme outperforms in all the schemes used. The simulated results confirm that the system throughput is an active function of relay placement.     

Sensorless induction motor drive with a single DC-link currentsensor and instantaneous active and reactive power feedback

This paper proposes a novel torque and speed control structure for low-cost induction motor variable-speed drives with a single DC-link current sensor. The controller is based on reconstruction of the active and instantaneous reactive power from the DC-link current without the use of a shaft sensor. An effective way of achieving tracking of set values of motor torque and flux is to base the estimation on the instantaneous active (P) and reactive power (Q). The paper proposes a way for extracting instantaneous P and Q information from the DC-link current and the pulsewidth modulation pattern. Torque and flux controllers suitable for general purpose and traction applications are proposed. The paper presents analytical considerations, straightforward design guidelines, and experimental results obtained from a traction system with a battery-fed three-phase inverter and a 7.5 kW traction motor     

Independent field-oriented control of two split-phase induction motors from a single six-phase inverter

Split-phase (six-phase) induction motor stator windings consist of two sets of three phase windings, which are spatially phase separated by 30 electrical degrees. Due to mutual cancellation of the air gap flux for all the 6n/spl plusmn/1 (n=1,3,5...) order harmonic voltages, called zero sequence components, large harmonic currents are generated in the stator phases. Only the 12n/spl plusmn/1 (n=0,1,2,3...)-order harmonic voltage components contribute toward the air gap flux and electromagnetic torque production in the machine. In this paper, a novel scheme is proposed where two six-phase induction motors are connected in series with proper phase sequence so that the zero sequence component voltages of one machine act as torque and flux producing components for the other. Thus, the two six-phase motors can be independently controlled from a single six-phase inverter. A vector control scheme for the dual motor drive is developed and experimentally verified in this paper.     

A solid-state controller for a wind-driven slip-ring induction generator

This letter describes an electronic technique for controlling a system-connected induction generator with wind turbine drive to extract maximum available power at all rotational speeds in the usable wind speed range.     

一种新型X射线发生器电源设计

设计了一种新型X射线发生器电源,应用高频开关电源技术、高压倍压整流技术与单片机控制技术,成功研制出一台额定电压160 kV,管电流0.4 mA~1.2 mA的用于安检设备的X射线发生器。介绍了X射线发生器的应用场合、工作原理、主要设计思想及国内外研究现状;详细介绍了设计的X射线发生器电源的功能构成,阐述了高压与灯丝高频逆变电路、高压倍压整流电路以及控制系统的拓扑结构、设计过程和仿真结果;最后给出了试验结果以及与安检系统进行联试的扫描图像,测试结果表明,其技术指标达到安检设备用X射线发生器的要求。     

A novel sine-wave generator using a single operational amplifier

A new realization of a variable frequency active RC oscillator using a single operational amplifier is given. The frequency variation is obtained by controlling a single grounded capacitor in the network.     

Increasing power input to a single solar power satellite rectenna by using a pair of satellites

An outline of the solar power satellite concept is given, and some remarks are made regarding the desirability of increasing the power handling capability of the receiving site. Three arrangements, each based on the use of a pair of satellites, are described by means of which the power handled by a single site may be doubled.     

A new automatic generation controller for a wind-driven slip-ring induction generator

A new scheme for controlling the stator power output of a system-connected slip-ring induction generator by electronic variation of its rotor resistance is presented. Laboratory testing suggests the application of this scheme in overcoming major operational difficulties experienced by wind turbine generators operating in parallel with a small power grid.     

Performance analysis of a complete adiabatic logic system driven by the proposed power clock generator

We analyze the energy performance of a complete adiabatic circuit/system including the Power Clock Generator （PCG） at the 90 nm CMOS technology node. The energy performance in terms of the conversion efficiency of the PCG is extensively carried out under the variations of supply voltage, process comer and the driver transistor＇s width. We propose an energy-efficient singe cycle control circuit based on the two-stage comparator for the synchronous charge recovery sinusoidal power clock generator （PCG）. The proposed PCG is used to drive the 4-bit adiabatic Ripple Carry Adder （RCA） and their simulation results are compared with the adiabatic RCA driven by the reported PCG. We have also simulated the logically equivalent static CMOS RCA circuit to compare the energy saving of adiabatic and non-adiabatic logic circuits. In the clock frequency range from 25 MHz to 1GHz, the proposed PCG gives a maximum conversion efficiency of 56.48%. This research work shows how the design of an efficient PCG increases the energy saving of adiabatic logic.     

Sensorless speed tracking of induction motor with unknown torque based on maximum power transfer

In this paper, the authors first derive the maximum power transfer theorem for an induction motor. Then, a nonlinear indirect adaptive sensorless speed tracking controller for the motor with the maximum power transfer is proposed. In this controller, only the stator currents are assumed to be measurable. The rotor flux and speed observers are designed to relax the need of flux and speed measurement. In addition, the rotor resistance estimator is also designed to cope with the problem of the fluctuation of rotor resistance with temperature. Stability analysis based on Lyapunov theory is also performed to guarantee that the controller design here is stable. Finally, the computer simulations and experiments are conducted to demonstrate the satisfactory tracking performance of the authors' design subject to maximum power transfer.     

Eleven-bit parity generator with a single, vertically integratedresonant tunnelling device

A vertically integrated diode (VID) with five negative differential resistance regions has been developed by stacking five resonant tunnelling structures. This device can be used for processing both analogue and digital signals. An 11-bit parity checker was demonstrated using the VID. In this approach, a single device replaced a large number of exclusive-OR gates in a conventional parity checker     

Analysis of a variable-speed wind energy conversion scheme with doubly-fed induction generator

In the last decade, the high penetration of wind turbines into the power system has been closely related to the advancement of wind turbine technology and control. The electric system contained by a large wind turbine, as well as within an offshore wind farm with hundreds of MW power capacity, has become more and more important in the interaction between the mechanical system of the wind turbine and the main power system. Furthermore, power electronics is entering the wind turbine circuitry which improves the controllability. The work presented in this paper has the main objective of extending the ability of the existing wind turbine design tools, in order to simulate the dynamic behaviour of wind turbines and the wind turbine–grid interaction.     

The power transfer and frequency detuning in a gyrotron

A rigorous small-signal theory of the power transfer and the associated complex frequency shift of a gyrotron oscillator is developed. Experimental results taken from a 28 GHz gyrotron operating in the TE₀₂ mode, (measurements made at UKAEA, Culham Laboratory) and theoretical results on the frequency detuning are compared. It is seen that the frequency detuning increases as the frequency of the electric field approaches that of the cyclotron frequency. The imaginary component of the theoretical complex frequency detuning is shown to indicate the region of operation of the device and this is also compared with that obtained experimentally.     

Design, fabrication and performance of a new vibration-based electromagnetic micro power generator

This paper presents a new vibration-based electromagnetic micro power generator fabricated using microelectromechanical systems (MEMS) technology, which can convert ambient vibration energy into electric power. The microgenerator consists of a permanent magnet of NdFeB, a copper planar spring and a two-layer copper coil. ANSYS modal analysis was used to predict the resonant frequencies and resonant vibration modes of the spring-mass system. The detailed fabrication processes of the microgenerator are given. Experimental results show that the prototype microgenerator can generate open-circuit voltage of 60 mV ac peak–peak with 121.25 Hz input frequency and the acceleration of 1.5g (g=9.8 m/s²). The experimental and simulated results were compared and discussed.     

Safe and efficient power management of hard real-time networks-on-chip

The power overhead of Networks-on-Chip (NoCs) becomes tremendous in high density Multiprocessor Systems-on-Chip (MPSoCs). Especially in hard real-time and safety-critical systems, power management mechanisms must be developed and efficiently adhered to real-time requirements. However, state-of-the-art solution typically induces a high timing overhead, thus challenging safety, or has limited power saving capabilities. Additionally, current power-gating mechanisms do not provide an upper bound of the latency overhead, and thus no timing guarantees. We propose a safe and enhanced approach for power-gating that allows a global and dynamic power management under timing guarantees, i.e., all deadlines of critical tasks are met. It introduces a control-layer to save power on the NoC data layer using multiple Power-Aware Traffic-Monitor (PATM) units, which apply knowledge of the global state of the system to efficiently save power on NoC routers even at high NoCs utilizations. To safely apply the PATMs in hard real-time systems while meeting the deadlines, we provide a formal worst-case timing analysis to derive PATMs upper bound latency overhead. Experimental results show that our approach efficiently reduces static power consumption, and provides scalability inducing very small area overhead.     

Microprocessor control of a transistorized induction heating power supply

This paper describes the incorporation of a microprocessor based power controller into a transistorized induction heating power supply. The use of the system is illustrated by the implementation of circuit protection and power control procedures. In the design, emphasis has been placed on the efficient use of the microprocessor, a high level of interference immunity within the system, and the provision of a fault monitoring system so that the performance of the unit can be assessed continuously.