Multi-frequency point supported LLRF front-end for CiADS wide-bandwidth application

The China initiative Accelerator Driven System,CiADS,physics design adopts 162.5 MHz,325 MHz,and 650 MHz cavities,which are driven by the corresponding radio frequency(RF)power system,requiring frequency translation front-end for the RF station.For that application,a general-purpose design front-end prototype has been developed to evaluate the multi-frequency point supported design feasibility.The difficult parts to achieve the requirements of the general-purpose design are reasonable device selection and balanced design.With a carefully selected low-noise wide-band RF mixer and amplifier to balance the performance of multi-frequency supported down-conversion,specially designed LO distribution net to increase isolation between adjacent channels,and external band-pass filter to realize expected up-conversion frequencies,high maintenance and modular front-end generalpurpose design has been implemented.Results of standard parameters show an R2 value of at least 99.991%in the range of-60-10 dBm for linearity,up to 18 dBm for P1dB,and up to 89 dBc for cross talk between adjacent channels.The phase noise spectrum is lower than 80 dBc in the range of 0-1 MHz;cumulative phase noise is 0.006°;and amplitude and phase stability are 0.022%and 0.034°,respectively.

Theoretical Analysis of the Frequency Jump in E-fishbone Experiments

It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It is found that the e-fishbone frequency increases with the hot electron energy, which is consistent with the experiments. The growth rate of the mode （m= 2, n = 2） is greater than that of the mode （m = 1, n = 1）.

Transient Stability Analysis of Converter-based Islanded Microgrids Based on Iterative Equal Area Criterion Considering Reactive Power Loop Dynamics and Varying Damping

With the rapid increase in the installed capacity of renewable energy in modern power systems,the stable operation of power systems with considerable power electronic equipment requires further investigation.In converter-based islanded microgrid(CIM)systems equipped with grid-following(GFL)and grid-forming(GFM)voltage-source converters(VSCs),it is challenging to maintain stability due to the mutual coupling effects between different VSCs and the loss of voltage and frequency support from the power system.In previous studies,quantitative transient stability analysis was primarily used to assess the active power loop of GFM-VSCs.However,frequency and voltage dynamics are found to be strongly coupled,which strongly affects the estimation result of stability boundary.In addition,the vary-ing damping terms have not been fully captured.To bridge these gaps,this paper investigates the transient stability of CIM consid-ering reactive power loop dynamics and varying damping.First,an accuracy-enhanced nonlinear model of the CIM is derived based on the effects of reactive power loop and post-disturbance frequency jump phenomena.Considering these effects will eliminates the risk of misjudgment.The reactive power loop dynamics make the model coefficients be no longer constant and thus vary with the power angle.To evaluate quantitatively the effects of re-active power loop and varying damping on the transient stability of CIM,an iterative criterion based on the equal area criterion theory is proposed.In addition,the effects of parameters on the stable boundary of power system are analyzed,and the dynamic interaction mechanisms are revealed.Simulation and experiment results verify the merits of the proposed method.

VIBRATION ANALYSIS OF A BEAM WITH EMBEDDED SHAPE MEMORY ALLOY WIRES

In this study, analytical relations for evaluating the exact solution of natural fre- quency and mode shape of beams with embedded shape memory alloy （SMA） wires are presented. Beams are modeled according to Euler-Bernoulli, Timoshenko and third order beam （Reddy） the- ories. A relation is obtained for determining the effect of axial load generated by the recovery action of pre-strained SMA wires. By defining some dimensionless quantities~ the effect of different me- chanical properties on the frequencies and mode shapes of the system are carefully examined. The effect of axial load generated by SMA wires with buckling load and frequency jump is accurately studied.