Virtual Inertia Estimation Method of DFIG-based Wind Farm with Additional Frequency Control

With the increasing penetration of wind power,using wind turbines to participate in the frequency regulation to support power system has become a clear consensus.To accurately quantify the inertia provided by the doubly-fed induction generator(DFIG)based wind farm,the frequency response model of DFIG with additional frequency control is established,and then by using Routh approximation,the explicit expression of the virtual moment of inertia is derived for the DFIG gridconnected system.To further enhance the availability of the expression,an estimation method is proposed based on the matrix pencil method and the least squares algorithm for estimating the virtual moment of inertia provided by the wind farm.Finally,numerical results tested by a DFIG grid-connected system and a modified IEEE 30-bus system verify the derived expression of the virtual moment of inertia and the proposed estimation method.

Interval optimal power flow applied to distribution networks under uncertainty of loads and renewable resources

Optimal power flow(OPF) has been used for energy dispatching in active distribution networks.To satisfy constraints fully and achieve strict operational bounds under the uncertainties from loads and sources, this paper derives an interval optimal power flow(I-OPF)method employing affine arithmetic and interval Taylor expansion.An enhanced I-OPF method based on successive linear approximation and second-order cone programming is developed to improve solution accuracy.The proposed methods are benchmarked against Monte Carlo simulation(MCS) and stochastic OPF.Tests on a modified IEEE 33-bus system and a real 113-bus distribution network validate the effectiveness and applicability of the proposed methods.

An Impedance-based Parameter Design Method for Active Damping of Load Converter Station in MTDC Distribution System

To achieve the efficient application of impedance analysis in the stability assessment and enhancement of multiterminal DC distribution systems, this paper proposes the DCside reduced-order impedance models with power control and AC voltage control, respectively, by taking the load converter station as the object. By using the DC-side current as the feedforward state, the active compensator applied to the load converter station with two control modes is also derived as well as the corresponding reduced-order impedance models. Combined with the reduced-order impedance models, a method based on damping factor sensitivity is further proposed to design the parameters of the derived active compensators. The verification results in the frequency domain and time domain demonstrate the accuracy of the reduced-order impedance and the effectiveness of the proposed compensator parameter design method.

Fiber‑Optic Microfiber:Tracking Activity Enhancement and Suppression of Heterogeneous Photocatalysts

Obtaining detailed insight into the photocatalytic performance of heterogeneous photocatalytic materials,is important for evaluating material properties as well as guiding material design.However,capture of the detailed matter changes on a photocatalyst surface in real time,and in situ during photocatalysis remains challenging.This work reports a promising optical microfiber sensor integrating a photocatalytic reaction monolayer on an optical microfiber surface to monitor reaction kinetics using Cu_(2)O-based heterogeneous photocatalysts,as an example.The evanescent field of microfiber is used to track the photocatalytic process in real time,through the interaction with the catalytic layer,by monitoring the surface refractive index changes caused by adsorption and degradation.Since the catalytic layer is less than 1µm thick,the typical high-power light source can be replaced by low-power light irradiation.This method successfully reveals that relative to the pristine Cu_(2)O microspheres,the photocatalytic activity is enhanced by the incorporation of Ti_(3)C_(2)T_(x) MXene into Cu_(2)O,whereas incorporation of CdS into Cu_(2)O suppresses the activity.Compared with the existing methods used for photocatalysis evalu-ation,this optical microfiber can be directly employed in real matrices to track local photocatalytic performance.It can also provide details about the different adsorption/degradation kinetics of photocatalysts.It is suitable for most photocatalytic processes and is not limited to pollutants with characteristic UV–visible absorption spectra.This study provides important inspiration for the future development of in situ,real-time reaction assessment.