查看更多>>摘要：To tackle emerging power system small-signal sta-bility problems such as wideband oscillations induced by the large-scale integration of renewable energy and power electron-ics,it is crucial to review and compare existing small-signal sta-bility analysis methods.On this basis,guidance can be provided on determining suitable analysis methods to solve relevant small-signal stability problems in power electronics-dominated power systems(PEDPSs).Various mature methods have been developed to analyze the small-signal stability of PEDPSs,in-cluding eigenvalue-based methods,Routh stability criterion,Ny-quist/Bode plot based methods,passivity-based methods,posi-tive-net-damping method,lumped impedance-based methods,bi-furcation-based methods,etc.In this paper,the application con-ditions,advantages,and limitations of these criteria in identify-ing oscillation frequencies and stability margins are reviewed and compared to reveal and explain connections and discrepan-cies among them.Especially,efforts are devoted to mathemati-cally proving the equivalence between these small-signal stabili-ty criteria.Finally,the performance of these criteria is demon-strated and compared in a 4-machine 2-area power system with a wind farm and an IEEE 39-bus power system with 3 wind farms.
查看更多>>摘要：Renewable energy sources(RESs)are rapidly devel-oping and their substitution for traditional power generation poses significant challenges to the frequency regulation in pow-er systems.The load damping factor D characterizes the active power of load that changes with power system frequency,which is an important factor influencing the frequency response.How-ever,the value of D is small,resulting in the limitation in fre-quency regulation of the power system.This paper proposes a parallel-type load damping factor controller to enhance load damping factor by utilizing static var generators(SVGs)in sub-stations.Additionally,it discusses the configuration method for the relevant parameters of the controller,evaluates its frequen-cy regulation capability,investigates the impact of large-scale application of the controller on static and dynamic loads,and conducts a comprehensive evaluation of the impact of the damp-ing factor control process on the voltage stability of the main grid.The large-scale application of the proposed controller can significantly improve the frequency regulation capability,and al-most have no influence on the working status of the load.It can also significantly improve the dynamic performance of system frequency.The proposed controller can provide technical sup-port for the frequency regulation of new power systems with high proportion of RESs.
查看更多>>摘要：In recent years,with increasing amounts of renew-able energy sources connecting to power grids,sub-/super-syn-chronous oscillations(SSOs)occurred more frequently.Due to the time-variant nature of SSO magnitudes and frequencies,as well as the mutual interferences among SSO modes with close frequencies,the accurate parameter estimation of SSO has be-come a particularly challenging topic.To solve this issue,this paper proposes an improved spectrum analysis method by im-proving the window function and a spectrum correction method to achieve higher precision.First,by aiming at the sidelobe characteristics of the window function as evaluation criteria,a combined cosine function is optimized using a genetic algorithm(GA).Furthermore,the obtained window function is self-con-volved to extend its excellent characteristics,which have better performance in reducing mutual interference from other SSO modes.Subsequently,a new form of interpolated all-phase fast Fourier transform(IpApFFT)using the optimized window func-tion is proposed to estimate the parameters of SSO.This meth-od allows for phase-unbiased estimation while maintaining algo-rithmic simplicity and expedience.The performance of the pro-posed method is demonstrated under various conditions,com-pared with other estimation methods.Simulation results vali-date the effectiveness and superiority of the proposed method.
查看更多>>摘要：In recent years,with the growth of wind energy re-sources,the capability of wind farms to damp low-frequency os-cillations(LFOs)has provided a notable advantage for the sta-bility enhancement of the modern power grid.Meanwhile,ow-ing to variations in the power system operating point(OP),the damping characteristics of LFOs may be affected adversely.In this respect,this paper presents a coordinated robust propor-tional-integral-derivative(PID)based damping control ap-proach for permanent magnet synchronous generators(PMSGs)to effectively stabilize LFOs,while considering power system op-erational uncertainties in the form of a polytopic model con-structed by linearizing the power system under a given set of OPs.The proposed approach works by modulating the DC-link voltage control loop of the grid-side converter(GSC)via a sup-plementary PID controller,which is synthesized by transform-ing the design problem into H-infinity static output feedback(SOF)control methodology.The solution of H-infinity SOF con-trol problem involves satisfying linear matrix inequality(LMI)constraints based on the parameter-dependent Lyapunov func-tion to ensure asymptotic stability such that the minimal H-in-finity performance objective is simultaneously accomplished for the entire polytope.The coordinated damping controllers for the multiple wind farms are then designed sequentially by using the proposed approach.Eigenvalue analysis confirms the im-proved damping characteristics of the closed-loop system for several representative OPs.Afterward,the simulation results,in-cluding the performance comparison with existing approaches,validate the higher robustness of the proposed approach for a wide range of operating scenarios.
查看更多>>摘要：In the existing small-signal stability constrained op-timal power flow(SSSC-OPF)algorithms,only the rightmost ei-genvalue or eigenvalues that do not satisfy a given threshold,e.g.,damping ratio threshold and real-part threshold of eigen-value,are considered in the small-signal stability constraints.The effect of steady-state,i.e.,operating point,changes on eigen-values is not fully taken into account.In this paper,the small-signal stability constraint that can fully reflect the eigenvalue change and system dynamic performance requirement is formed by analyzing the eigenvalue distribution on the complex plane.The small-signal stability constraint is embedded into the standard optimal power flow model for generation reschedul-ing.The simultaneous solution formula of the SSSC-OPF is es-tablished and solved by the quasi-Newton approach,while pen-alty factors corresponding to the eigenvalue constraints are de-termined by the stabilization degree of constrained eigenvalues.To improve the computation speed,a hybrid algorithm for ei-genvalue computation in the optimization process is proposed,which includes variable selection for eigenvalue estimation and strategy selection for eigenvalue computation.The effectiveness of the proposed algorithm is tested and validated on the New England 10-machine 39-bus system and a modified practical 68-machine 2395-bus system.
查看更多>>摘要：Continuous power supply of urban power networks(UPNs)is quite essential for the public security of a city be-cause the UPN acts as the basis for other infrastructure net-works.In recent years,UPN is threatened by extreme weather events.An accurate modeling of load loss risk under extreme weather is quite essential for the preventive action of UPN.Con-sidering the forecast intensity of a typhoon disaster,this paper proposes analytical modeling of disaster-induced load loss for preventive allocation of mobile power sources(MPSs)in UPNs.First,based on the topological structure and fragility model of overhead lines and substations,we establish an analytical load loss model of multi-voltage-level UPN to quantify the spatial dis-tribution of disaster-induced load loss at the substation level.Second,according to the projected load loss distribution,a pre-ventive allocation method of MPS is proposed,which makes the best use of MPS and dispatches the limited power supply to most vulnerable areas in the UPN.Finally,the proposed meth-od is validated by the case study of a practical UPN in China.
查看更多>>摘要：Battery energy storage stations(BESSs)pose sever-al challenges for both phasor-based differential protection and the newly-proposed time-domain differential protection.These challenges include low sensitivity and even rejection.Besides,the negative impact of various nonideal conditions,including current transformer(CT)saturation,errors,and outliers,on the security of differential protection remains an important problem.Motivated by the aforementioned issues,this study ac-counts for the trajectory distribution discrepancy on Cartesian plane under various conditions and proposes a time-domain dif-ferential protection method.In this paper,the trajectory formed by operating and restraining current samples is devel-oped.Subsequently,after considering different operating states,the fault severity levels,and nonideal conditions,the variances in trajectory distribution between internal and external faults are extensively analyzed.On this basis,the Cartesian plane is divided into operating,uncertainty,and restraining zones.Fur-ther,the operating and restraining trajectory indices are meticu-lously designed and a protection criterion based on these indi-ces is formed to accurately separate internal faults from other events,unaffected by CT saturation,errors,and outliers.The exceptional performance of the proposed protection method is extensively validated through PSCAD simulations and a hard-ware-in-the-loop testing platform.Regarding the dependability,sensitivity,and security,the proposed protection method outper-forms three state-of-the-art differential protection methods.
查看更多>>摘要：Since the scale and uncertainty of the power sys-tem have been rapidly increasing,the computation efficiency of constructing the security region boundary(SRB)has become a prominent problem.Based on the topological features of histori-cal operation data,a sample generation method for SRB identi-fication is proposed to generate evenly distributed samples,which cover dominant security modes.The boundary sample pair(BSP)composed of a secure sample and an unsecure sam-ple is defined to describe the feature of SRB.The resolution,sampling,and span indices are designed to evaluate the cover-age degree of existing BSPs on the SRB and generate samples closer to the SRB.Based on the feature of flat distribution of BSPs over the SRB,the principal component analysis(PCA)is adopted to calculate the tangent vectors and normal vectors of SRB.Then,the sample distribution can be expanded along the tangent vector and corrected along the normal vector to cover different security modes.Finally,a sample set is randomly gen-erated based on the IEEE standard example and another new sample set is generated by the proposed method.The results in-dicate that the new sample set is closer to the SRB and covers different security modes with a small calculation time cost.
查看更多>>摘要：Improving the restoration efficiency of a distribu-tion system is essential to enhance the ability of power systems to deal with extreme events.The distribution system restoration(DSR)depends on the interaction among the electric network(EN),cyber network(CN),and traffic network(TN).However,the coordination of these three networks and co-dispatching of multiple recovery resources have been mostly neglected.This paper proposes a novel DSR framework,which is formulated as a mixed-integer linear programming(MILP)problem.The fail-ures in cyber lines result in cyber blind areas,which restrict the normal operation of remote-controlled switches.To acceler-ate the recovery process,multiple recovery resources are uti-lized including electric maintenance crews(EMCs),cyber main-tenance crews(CMCs),and emergency communication vehicles(ECVs).Specifically,CMCs and ECVs restore the cyber func-tion of switches in cooperation,and EMCs repair damaged elec-tric lines.The travel time of these three dispatchable resources is determined by TN.The effectiveness and superiority of the proposed framework are verified on the modified IEEE 33-node and 123-node test systems.
查看更多>>摘要：An nonlinear model predictive controller(NMPC)is proposed in this paper for compensations of single line-to-ground(SLG)faults in resonant grounded power distribution networks(RGPDNs),which reduces the likelihood of power line bushfire due to electric faults.Residual current compensation(RCC)inverters with arc suppression coils(ASCs)in RGPDNs are controlled using the proposed NMPC to provide appropri-ate compensations during SLG faults.The proposed NMPC is incorporated with the estimation of ASC inductance,where the estimation is carried out based on voltage and current measure-ments from the neutral point of the power distribution net-work.The compensation scheme is developed in the discrete time using the equivalent circuit of RGPDNs.The proposed NMPC for RCC inverters ensures that the desired current is in-jected into the neutral point during SLG faults,which is veri-fied through both simulations and control hardware-in-the-loop(CHIL)validations.Comparative results are also presented against an integral sliding mode controller(ISMC)by demon-strating the capability of power line bushfire mitigation.
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