Dynamic Characteristics Of Power System Research Articles

Tunnel Magnetoresistance-Based Noncontact Current Sensing and Measurement Method

The dynamic characteristics of power systems have become increasingly complex with the growing application of power electronics equipment. A high level of real-time monitoring is now required to provide a database for system stability and safety control. Therefore, flexible and accurate sensor technology is crucial. In this article, a noncontact current sensing method is proposed using tunnel magnetoresistance (TMR) technology. Based on the introduction of TMR chip characteristics, the sensing law of a TMR chip surrounding a current-carrying wire is revealed. An arrangement of four TMR chips is then proposed to reflect the magnetic field intensity around a current-carrying wire. A TMR chip array-based noncontact current sensing technique is presented for use as a real set-and-use current sensing method. The convenience of the proposed method is superior to traditional current sensors because the wire does not need to be surrounded by a magnetic ring or coil. A method for location detection is presented to avoid iterating for every sample, which significantly reduces the computation burden. Simulations are then carried out to demonstrate the effectiveness of the proposed method. A current sensor prototype based on a printed circuit board (PCB) is developed, and its practicality is proven by experiments. Test results show that the prototype can meet the requirements of phasor measurement unit (PMU) standards, indicating that the proposed current sensing method is practical and can be applied in M-class and P-class PMUs for current sensing.

A Critical Review of Data-Driven Transient Stability Assessment of Power Systems: Principles, Prospects and Challenges

Transient stability assessment (TSA) has always been a fundamental means for ensuring the secure and stable operation of power systems. Due to the integration of new elements such as power electronics, electric vehicles and renewable power generations, dynamic characteristics of power systems are becoming more and more complex, which makes TSA an increasingly urgent task. Since traditional time-domain simulations and direct method cannot meet the actual operation requirements of power systems, data-driven TSA has attracted growing attention from both academia and industry. This paper makes a comprehensive review from the following four aspects: feature extraction and selection, model construction, online learning and rule extraction; and then, summarizes the challenges and prospects for future research; finally, draws the conclusions of this review. This review will be beneficial for relevant researchers to better understand the research status, key technologies, and existing challenges in the field.

Reliability and Dynamic Performance Simulation Based on Relay Protection Summary

With the development of science and technology, national security and social life can not be separated from electricity every moment, and the safety of power grid is becoming more and more important. At present, the research on relay protection model in dynamic simulation of power system in China is still in the primary stage. Because the research is not deep enough, the control law of relay protection elements can not be well grasped. The failure can not be handled well. Therefore, in order to ensure the safe operation of the power system, we must first strengthen the grid structure of the power system, improve the elasticity coefficient, distribute the reserve capacity reasonably, strengthen the adjustment ability of the tie line between the major power grids, and improve the stable reserve of the power grid. In order to improve the authenticity and reliability of dynamic simulation, it is necessary to establish a set of relay protection models, which should be consistent with the actual relay protection. In this way, the stability problem in power system can be analyzed accurately to improve the reliability of power system. The relay protection model established in this paper reduces the complexity of modeling and can reflect the dynamic characteristics of power system after interference. It is of great significance to the analysis and research of power system.

Model order reduction analysis of DFIG integration on the power system small‐signal stability considering the virtual inertia control

In view of the problem that the detailed model of doubly-fed induction generator (DFIG) considering virtual inertia control is high ordered and difficult to analyse, a reduced-order model for DFIG that is applicable to small-signal stability analysis is presented. First, according to the attenuating speed of each state variable, the dynamic characteristics of different components of DFIG are explored from the time scale perspective. On this basis, considering the electromechanical coupling characteristic of DFIG, the third-order simplified model retaining the dynamic of virtual inertia control and phase-locked loop is derived. Moreover then, the dynamic model of inter-connected system with reduced-order model integration is established. Finally, the attenuation time constant of each state variable of DFIG detailed model is calculated. Simulation tests on the New England 10-generator 39-bus test system verify that compared with detailed model of DFIG, the presented reduced-order model could reflect the dynamic characteristics of power system under small-signal disturbance more accurately, with greatly reduced computation amount.

Estimation of the Instantaneous Values of the Electrical Operating Parameters in the Ac Network1

The problem of determining the instantaneous values of the electrical operating parameters for the purpose of investigating dynamic processes in nonlinear systems is considered. It is shown that existing procedures for calculating the parameters, which provide a sampling rate of the output data equal to the operating frequency period, does not enable the value of the parameters to be estimated at an arbitrary instant of time with high accuracy. A method of determining the instantaneous values of the electrical operating parameters is proposed, based on a modified Hilbert transformation. An example of the determination of the frequency, amplitude and phase of the current when there is a short circuit is presented. The results enable phenomena occurring “within” the period of the industrial current frequency to be investigated, and also enable the dynamic characteristics of power systems to be determined more accurately.

Analysis of System Key Variables under Power Fluctuation from Wind Power Cluster

The influence of power fluctuation from wind power clusters on power system is more and more significant. In order to describe this influence, a key variable set which can perfectly reflect dynamic characteristics of power system under wind power fluctuation is determined based on a pratical power system. Then, drift characteristics of the key variables under typical power fluctuation of wind power cluster are analyzed. The comparison of the drift characteristics between the key variables and the non-key variables verifies the feasibility and validity of the method.

Power System Subsynchronous Oscillations Electromagnetic and Electromechanical Transient Hybrid Real-Time Simulation Based on RTDS

In this paper, power system electromagnetic and electromechanical transient hybrid real-time simulation technology is expounded in details, which has advantages of the electromagnetic transient simulation program and electromechanical ones. The more details needed to analyze the dynamic characteristics of power systems are provided by this hybrid simulation technology, and the scale of power system simulated is not limited in the hybrid simulation program. The hybrid simulation program is applied to analyze the power system subsynchronous oscillation problem occurred in a power plant with 4 turbine generators located in the northwestern China. According to the simulation results, it is clear that the stability of generators is threatened by the subsynchronous oscillations caused by capacitor series compensation in the transmission line connecting the power plant and the load center system. In meantime, the effectiveness of the countermeasure is validated simultaneously by the hybrid simulation results.

A Dynamic Synchrophasor Estimation Algorithm for Online Application

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A new algorithm for synchrophasor estimation is proposed to improve estimation accuracy under dynamic conditions. The real component of a constantly rotating vector and a low-frequency band-limited vector, which is linearized by Taylor series, is employed to model supplied signals in power systems. And dynamic characteristics of power systems are described in form of Taylor series' derivatives, which are calculated through consecutive phasors. The accuracy of phasor estimation was dramatically improved by the reassignment of estimation of short-time Fourier transform (STFT) with knowledge of these derivatives. Simulation results allow us to make the conclusion that the proposed algorithm improves the accuracy of phasor estimations under dynamic conditions dramatically, such as frequency ramping, low frequency oscillation, etc., at the cost of the calculation burden is a minimal increase whilst still meeting the requirements of the application for power systems. </para>

Dynamic phasor and frequency estimator for phasor measurement units

Synchrophasors and frequency estimations play an increasingly important role in power systems. Discrete Fourier transform (DFT) may introduce errors into phasor and frequency estimations under dynamic conditions, such as power oscillation. A dynamic phasor and frequency estimator for phasor measurement units (PMUs) is proposed to improve accuracy by considering dynamic characteristics of power systems expressed as Taylor derivatives. Firstly, phasor estimations of sequence components of diffident data windows are attained via DFT. Secondly Taylor derivatives, expressed by adjacent phasors at different data windows, are employed to improve accuracy of estimations by reassigning estimations with the knowledge of dynamic characteristics. Finally, dynamic characteristics of positive sequence components are applied to estimate the fundamental frequency with less delay compared to a state-of-the-art algorithm, phasor-based synchronised frequency measurement (PSFM). To verify the performance, a set of digital dynamic tests and a power oscillation model using PSCAD/EMTDC are presented. The simulation results show that proposed algorithm can achieve highly accurate estimations of phasor and frequency over a wide range of dynamic conditions. Even though a minor increase in calculation burden is required, this technique provides accurate phasor and frequency estimations without changing the legacy structure of PMU devices. Additionally, it has been found that proposed algorithm really meets the needs of online applications.

Visualization of results of load flow calculation and dynamic simulation

AbstractThis paper proposes graphical representation methods of static and dynamic characteristics of power systems. The methods use the computed results of load flow calculation and dynamic stability calculation. This work develops three kinds of representation methods using maps and animation which are sequential graphical representation of maps based on dynamic stability calculation.Conventionally the results of load flow calculation and dynamic stability calculation are represented and comprehended using load flow maps or dynamic swing curve. However, quick and effective comprehension of power system characteristics by such conventional representation methods is becoming more difficult as power systems to be analyzed are becoming larger and more complicated, especially in power systems with many loops or grids. Graphical representation using the proposed methods makes it easy to understand the static and dynamic characteristics of power systems quickly and comprehensively.In addition to these methods, this paper proposes a heuristic logic that makes it possible to draw maps automatically. It is very convenient to apply these methods to arbitrary power systems even if their constitutions or characteristics are not well known.

電力系統の潮流計算結果と安定度計算結果の視覚化

This paper proposes graphical representation methods of static and dynamic characteristics of power systems. The methods use the computed results of load flow calculation and dynamic stability calculation. This work develops three kinds of representation methods using maps and animation which are sequential graphical representation of maps based on dynamic stability calculation. Conventionally the results of load flow calculation and dynamic stability calculation are represented and comprehended using load flow maps or dynamic swing curve. However, quick and effective comprehension of power system characteristics by such conventional representation methods is becoming more difficult as power systems to be analyzed are becoming larger and more complicated, especially in power systems with many loops or grids. Graphical representation using the proposed methods makes it easy to understand the static and dynamic characteristics of power systems quickly and comprehensively. In addition to these methods, this paper proposes a heuristic logic that makes it possible to draw maps automatically. It is very convenient to apply these methods to arbitrary power systems even if their constitutions or characteristics are not well known.

A new eigen-analysis method of steady-state stability studies for large power systems: S matrix method

The authors discuss an advanced version of the S matrix method, an eigenvalue technique for the analysis of the steady-state stability (or the stability against small signals) of large power systems. The dynamic characteristics of power systems can be linearly approximated with a set of differential equations. The technique transforms the matrix A into the matrix S and then determines several eigenvalues with the largest absolute values from matrix S that correspond to the dominant eigenvalues of matrix A. In the process of identifying the appropriate eigenvalues, the method uses the refined Lanczos process, which makes high-speed calculation possible through the use of the sparsity and the structural uniformity of matrices. >