Current Status, Influence and Countermeasure of Biological Invasion on Ecological Security in China

The concept, pathways and the present status of biological invasion in China are reviewed in the paper, and the effect of biological invasion on ecological security is also introduced. On this basis, the measures such as establishing early-warning mechanism, strengthening the management of invasive species and quarantine of alien species, establishing scientific system of introduction and improving people awareness are proposed to control the invasion of alien species, so as to ensure the ecological security in china.

A Realization Method of Protocol Conversion Between Modbus and IEC61850

In order to adapt to the construction needs of the smart grid, smart substation need to solve the problem of protocol conversion between the conventional non-standardized condition monitoring equipment and the standardized monitoring system. This paper proposed a realization method of conversion method between Modbus and IEC61850. Object-oriented technology is used for information model on Modbus. After the analysis of IEC61850 and MMS information and service model, to establish the model mapping relationship between IEC61850, MMS and Modbus based on the principle of minimum information point which is one to one correspondence. Combined with the implementation of SISCO MMS-EASE LITE software development kit programming, giving a realization method using QT programming techniques based on the mapping model. Finally, the establishment the interval controller as an example of protocol scheme verifies the correctness and the feasibility of protocol conversion method.

Mechanics Analysis of Overhead Transmission Lines Based On-line Monitoring

At present, the on-line monitoring is widely applied to the power line monitoring. In this paper, a new mechanical calculation model is established according to the on-line monitoring. And this model is based on the parameters that tension sensors and angle sensors on suspended points detect, and combines with the parameters of the wire itself, and also considers the deflection angel of wires due to wind. In this model, mechanics parameters of wires are turned into the new coordinate plane after deflection angel of wires due to wind, or windage yaw plane. A statics tension balance equation is built in the vertical direction of the new windage yaw plane. According to the theoretical analysis and algorithm, we verify the accuracy of this newly developed mechanical calculation model.

Fast Uncertainty Quantification of Electromechanical Oscillation Frequency on Varying Generator Damping

This letter develops a fast analytical method for uncertainty quantification of electromechanical oscillation frequency due to varying generator dampings. By employing the techniques of matrix determinant reduction, two types of uncertainty analysis are investigated to quantify the impact of the generator damping on electromechanical oscillation frequency, i.e., interval analysis and probabilistic analysis. The proposed analytical frequency estimation formula is verified against conventional methods on two transmission system models. Then, Monte Carlo experiments and interval analysis are respectively conducted to verify the established lower/upper bound formulae and probability distribution formulae. Results demonstrate the accuracy and speed of the proposed method.

A fault locating method for multi-branch hybrid transmission lines in wind farm based on redundancy parameter estimation

In order to solve the problem of‘‘abandoned’’wind caused by short circuit faults in a wind farm,a wind farm fault locating method based on redundancy parameter estimation is proposed.Using the characteristics of the traveling wave,transmission equations containing the position of the fault point are constructed.Parameter estimation from statistical theory is used to solve the redundant transmission equations formed by multiple measuring points to locate the faults.In addition,the bad data error detection capability of the parameter estimation is used to determine bad data and remove them.This improves locating accuracy.A length coefficient is introduced to solve the error enlargement problem caused by a transmission line sag.The proposed fault locating method can solve the fault branch misjudgment problem caused by the short-circuit faults near the data measuring nodes of thewind farm based on the proposed fault interval criterion.It also avoids the requirements to the traveling wave speed of traditional methods,thus its fault location is more accurate.Its effectiveness is verified through simulations in PSCAD/EMTDC,and the results show that it can be used in thefault locating of hybrid transmission lines.

Multiple Random Forests Based Intelligent Location of Single-phase Grounding Fault in Power Lines of DFIG-based Wind Farm

To address the problems of wind power abandonment and the stoppage of electricity transmission caused by a short circuit in a power line of a doubly-fed induction generator(DFIG) based wind farm, this paper proposes an intelligent location method for a single-phase grounding fault based on a multiple random forests(multi-RF) algorithm. First, the simulation model is built, and the fundamental amplitudes of the zerosequence currents are extracted by a fast Fourier transform(FFT) to construct the feature set. Then, the random forest classification algorithm is applied to establish the fault section locator. The model is resampled on the basis of the bootstrap method to generate multiple sample subsets, which are used to establish multiple classification and regression tree(CART) classifiers. The CART classifiers use the mean decrease in the node impurity as the feature importance,which is used to mine the relationship between features and fault sections. Subsequently, a fault section is identified by voting on the test results for each classifier. Finally, a multi-RF regression fault locator is built to output the predicted fault distance. Experimental results with PSCAD/EMTDC software show that the proposed method can overcome the shortcomings of a single RF and has the advantage of locating a short hybrid overhead/cable line with multiple branches. Compared with support vector machines(SVMs)and previously reported methods, the proposed method can meet the location accuracy and efficiency requirements of a DFIG-based wind farm better.

Damping control for a target oscillation mode using battery energy storage

In this paper, a battery energy storage system(BESS) based control method is proposed to improve the damping ratio of a target oscillation mode to a desired level by charging or discharging the installed BESS using local measurements. The expected damping improvement by BESS is derived analytically for both a single-machineinfinite-bus system and a multi-machine system. This BESS-based approach is tested on a four-generator, twoarea power system. Effects of the power converter limit,response time delay, power system stabilizers and battery state-of-charge on the control performance are also investigated. Simulation results validate the effectiveness of the proposed approach.