Transient Stability Analysis Research Articles

Algorithm development for analyzing transient stability in Matlab

The electrical energy supply quality of the supply company is of great importance for both the supply company as the end users. This is because it is convenient for the supply company to bill all the electrical energy generated at that moment, and the end users can thus benefit from the supplied energy to perform the day-to-day chores. However, the electrical energy supply quality can be discontinued due to electrical faults caused by natural phenomena (thunderstorm, snow etc.) or by human operation errors. Therefore, due to the possible electrical fault occurrences in the different location of power system, transient stability analysis is required to determine the power system capacity to remain stable in presence of electrical disturbances.

Transient stability analysis and modelling of systems with grid-forming converters and synchronous generators

Transient stability analysis and modelling of systems with grid-forming converters and synchronous generators

Research on optimization scheme for boiling heat transfer models of mini-channels casing-pipes once-through steam generator

The mini-channels casing-pipes once-through steam generator(MCOTSG) is used for a certain type of small modular reactor. The boiling heat transfer model is crucial to the accuracy of simulating the heat transfer process on the secondary loop of MCOTSG. In this paper, the heat transfer tubes of MCOTSG are taken as the research object. The thermal–hydraulic model of primary and secondary loops is established based on the RELAP5 program. Then the different nucleate boiling heat transfer models are calibrated and analyzed based on the experimental results of the steady state under low flow rate conditions. On this basis, the secondary loop heat transfer characteristics and the overall operating characteristics of OTSG under the transient state of feedwater flow rate reduction are simulated. The results of the steady state and transient state analysis show that the revised model that the Bertsch correlation is used to correct the Chen correlation performs the best in terms of computational stability and computational accuracy. The results of the study can provide a basis for the safety analysis and optimal design of MCOTSG and small modular reactor under low flow rate conditions.

Multi-Machine Power System Transient Stability Enhancement Utilizing a Fractional Order-Based Nonlinear Stabilizer

Given the intricate nature of contemporary energy systems, addressing the control and stability analysis of these systems necessitates the consideration of highly large-scale models. Transient stability analysis stands as a crucial challenge in enhancing energy system efficiency. Power System Stabilizers (PSSs), integrated within excitation control for synchronous generators, offer a cost-effective means to bolster power systems’ stability and reliability. In this study, we propose an enhanced nonlinear control strategy based on synergetic control theory for PSSs. This strategy aims to mitigate electromechanical oscillations and rectify the limitations associated with linear approximations within large-scale energy systems that incorporate thyristor-controlled series capacitors (TCSCs). To dynamically adjust the coefficients of the nonlinear controller, we employ the Fractional Order Fish Migration Optimization (FOFMO) algorithm, rooted in fractional calculus (FC) theory. The FOFMO algorithm adapts by updating position and velocity within fractional-order structures. To assess the effectiveness of the improved controller, comprehensive numerical simulations are conducted. Initially, we examine its performance in a single machine connected to the infinite bus (SMIB) power system under various fault conditions. Subsequently, we extend the application of the proposed nonlinear stabilizer to a two-area, four-machine power system. Our numerical results reveal highly promising advancements in both control accuracy and the dynamic characteristics of controlled power systems.

Transient state analysis of a rub-impact rotor system during maneuvering flight

Maneuvering flight substantially affects the dynamic behavior of rotors; particularly, such flight may cause rubbing between a rotor and stator, which is one of the most serious damages in aircraft engines. In this paper, a nonlinear dynamic model for describing the dynamic characteristics of a rub-impact rotor system during maneuvering flight is established based on the Lagrange equations. Subsequently, numerical simulations employing the Newmark method are performed, delving into the detailed discussion of the influence of parameters such as rotational speed and maneuvering flight on the transient and steady-state responses of the rotor system. The effect mechanism of maneuver load and its coupling with rub impact is revealed. The results show that the impact response induced by maneuvering flight is more obvious in the subcritical state than in the supercritical state. The additional stiffness and damping are also induced; in particular, the additional damping has a coupling effect. Moreover, the rub impact imposes an additional constraint on the rotor system, thereby weakening the influence of the maneuver load and becoming the major factor that determines the dynamic behavior of the rotor system at high speeds.

Interconnection Study in Utilizing of Solar Energy for 150 MW Photovoltaic Power Generation through 150 kV Transmission Line

The interconnection of utility-scale photovoltaic (PV) power plants with the electric grid is a crucial factor that requires comprehensive analysis and assessment. The focus of this research article is on a specific photovoltaic (PV) power plant that is planned for construction in the X Power System located in Indonesia which has 150 MW capacity which has intermittent behavior, experiencing fluctuations in power generation based on the availability of sunlight and the cloud movement. The objective of this paper is to explore the feasibility, technical prerequisites, and potential solutions for the successful integration of the PV power plant into the existing power system. Multiple investigations will be carried out, which is Load Flow, Short-Circuit, and Transient Stability analyses, with the aim of assessing the consequences of linking the PV power plant to the existing power system. Consequently, it is vital to model the X power system conditions prior to the interconnection process. Moreover, modeling an intermittent PV power plant necessitates different approaches compared to conventional power plants. According to the research findings from load flow analysis, the voltage levels near the interconnection point, both prior to and after linking the PV Power Plant, remain within permissible bounds of +5% and -10%. Furthermore, there are no constraints on the load capacity of the transmission lines and Interbus Transformers (IBT) either prior to or following the integration of the PV Power Plant. The short-circuit current around the point of interconnection experiences a marginal increase, and it is advisable to employ circuit breakers (CB) rated at 40 kA for both the PV Power Plant and the switching station. Furthermore, the power system exhibits resilience in preserving its stability, even in scenarios involving abrupt power loss or intermittent generation from the PV Power Plant. These situations can result from unexpected outages or variations in solar radiation. The interconnection of the 150 MW PV Power Plant can be implemented without significant adverse effects on the system's voltage, loading capacity, and stability.

Transient Stability Analysis for a Multi-VSC Parallel System Based on the CFND Method

Because of the control complexity of voltage source converters (VSCs), transient stability analysis of multi-VSC parallel systems is challenging, and there are still no effective methods to solve this problem. Inspired by the decoupling principle and combined with the normal form method, an innovative coupling-factor-based nonlinear decoupling (CFND) method is proposed. According to the coupling factors that can be used to evaluate the nonlinear coupling degree among different state variables, the CFND method approximately transforms a high-order nonlinear multi-VSC parallel system into multiple decoupled low-order modes. Thus, the transient stability of the original high-order multi-VSC system can be reflected indirectly by the mature inversing trajectory method and the phase plane method. The CFND method has universality, flexibility, and insensitivity to system order, and no need to construct corresponding Lyapunov functions for different nonlinear systems, breaking through the inherent limitations of traditional analysis methods. Furthermore, this paper derives a reduced-order large-signal model and the corresponding truncated model for a single VSC grid-connected system. The effectiveness of the reduced-order model is verified through simulation waveforms and ROAs partitioning. Subsequently, a generalized model of the multi-VSC grid-connected system is developed. Finally, taking the grid-connected system with three VSCs as an example, the proposed CFND method is used to analyze typical operation cases, and the conclusions of transient stability analysis are verified using the hardware-in-loop (HIL) experiments.

Adaptive power capability control scheme for voltage source converter to improve transient stability

Applications of Power Electronic Devices (PED) are rapidly increasing because of their controllability. A Direct Current (DC) transmission system is used for the interconnection of Renewable Energy Sources (RES), and a DC grid research reached the stage of demonstration. Since power electronic devices are controllable, as opposed to conventional ac power facilities, various studies have been carried out on control schemes. Based on fast response speed, the device can affect the stability of the power system by improving the transient stability according to the control method. However, the operation range of converters is limited based on the normal state of the AC system. Therefore, the entire converter capacity cannot be used, and the same standard is applied even in the transient state. In this paper, a novel control scheme is proposed in order to improve the voltage and frequency stability by using the maximum capacity of the converter. The control scheme calculates an Adaptive Power Capability Index (APCI) based on the range of variation of frequency and voltage in the transient state, then applies this index to the controller. In order to verify the new control scheme, a dynamic model is developed and verified in a Transient Stability Analysis (TSA) program. Following the verification of the model, the model is applied to the actual power system data and the power system stability is analyzed.

Aggregation reduced-order modeling of grid-connected multi-converter system for transient stability analysis

Aggregation reduced-order modeling of grid-connected multi-converter system for transient stability analysis

Transient stability analysis of grid forming-controlled converters considering three types of current limiting algorithms

Transient stability analysis of grid forming-controlled converters considering three types of current limiting algorithms

A hybrid DMO-RERNN based UPFC controller for transient stability analysis in grid connected wind-diesel-PV hybrid system

AbstractIn this paper, a novel hybrid technique is proposed for transient stability analysis on grid connected Wind-Diesel-PV hybrid system. The proposed hybrid methodology is combination of the dwarf mongoose optimization algorithm (DMO) and the recalling enhanced recurrent neural network (RERNN) named DMO-RERNN. The main purpose of this work is to consider various elements on hybrid system for the analysis of transient stability according to different conditions. The voltage profile of hybrid system is enhanced using the proposed unified power flow controller (UPFC), which also has higher performance improving transient performance compared to the conventional ANN, PI and fuzzy-sliding mode controller. Considering the proposed technique, DMO is used to find the optimal global solution for the fault predicted by the RERNN approach. The proposed system is executed on MATLAB work platform; its performance with existing systems is analyzed. The result proves that the proposed hybrid technique based UPFC controller provides better results compared with other existing technique. The efficiency of the PI is 82.136, ANN is 77, Fuzzy Sliding Mode is 65.097% and proposed technique is 97.99038%.

Analysis of Power System Transient Stability of the Nigerian 330-kV Electricity Grid

Faults on power system are inevitable and can occur at any time resulting into transient instability. Transient instability can cause loss of synchronism and possible damage to power equipment and consumer loads. Therefore, this study analyzed the transient stability (TS) of the Nigerian 330-kV, 34-bus power network. Power flow and swing equations describing the system steady and transient states were respectively analyzed using Newton-Rahpson and Runge-Kutta, fourth order numerical techniques to provide linear solution due to their non-linearity. Simulations were done and swing curves for different fault conditions obtained. The critical clearing time at which the simulated faults were cleared was determined. The results of load flow analyses revealed that buses 6, 10, 13, 14, and 17 with respective voltage magnitude of 0.937, 0.921, 0.938, 0.829 and 0.780 per unit violated voltage tolerance limit of 0.95 to 1.05 p.u. The system total active and reactive power losses were 57.62 MW and -70.62 MVar respectively. The obtained swing curve showed that for fault on bus 11 [line 9-11] generators 2, 3 and 7 lost synchronism after 1.0 s but other generators retained their stability. Similarly, for fault on bus 13 [line 10-14] generators 3 and 7 lost synchronism but other generators retained stability after 0.4 s. These results indicate that faults occurrence on generating stations of power system is unavoidable, but the clearance time must be short (few seconds) to avert total system collapse and loss of synchronism.

The Analysis and Calculation of Power Angle Transient Characteristics in VSG Control Using Parameter-Perturbation-Based Averaging Method

With the increasing penetration of power converters in modern power system, virtual synchronous generator (VSG) control is considered to be a promising method due to its grid friendliness. However, the lack of clear and accurate description of its power angle dynamics poses challenges to the stability analysis and converter parameters design. In this paper, Krylov-Bogoliubov (K-B) averaging method, an effective parameter-perturbation-based analytical calculation method for dissipative process, is first presented to characterize the dynamic trajectory of VSG control. Moreover, the solvable problem is transformed from typical simple harmonic motion (SHM) into damped oscillation, which redistributes the weights of solvable and perturbed problems. On top of that, an unperturbed-result-based (URB) averaging method is further proposed to obtain the explicit time-domain expression of power angle dynamics, which may provide good potential for transient stability analysis and grid-connected converter design. Finally, simulations and control-hardware-in-loop (CHIL) experiments have been both demonstrated to verify the effectiveness of proposed method.

Dihydropyrimidine dehydrogenase from Escherichia coli: Transient state analysis reveals both reductive activation prior to turnover and diminished substrate effector roles relative to the mammalian form

Dihydropyrimidine dehydrogenase (DPD) is an enzyme that uses an elaborate architecture to catalyze a simple net reaction: the reduction of the vinylic bond of uracil and thymine. Known DPDs have two active sites separated by approximately 60 Å. One active site has an FAD cofactor and binds NAD(P) and the other has an FMN cofactor and binds pyrimidines. The intervening distance is spanned by four Fe4S4 centers that act as an electron conduit. Recent advancements with porcine DPD have revealed unexpected chemical sequences where the enzyme undergoes reductive activation by transferring two electrons from NADPH to the FMN via the FAD such that the active form has the cofactor set FAD•4(Fe4S4)•FMNH2. Here we describe the first comprehensive kinetic investigation of a bacterial form of DPD. Using primarily transient state methods, DPD from E. coli (EcDPD) was shown to have a similar mechanism to that observed with the mammalian form in that EcDPD is observed to undergo reductive activation before pyrimidine reduction and displays half-of-sites activity. However, two distinct aspects of the EcDPD reaction relative to the mammalian enzyme were observed that relate to the effector roles for substrates: (i) the enzyme will rapidly take up electrons from NADH, reducing a flavin in the absence of pyrimidine substrate, and (ii) the activated form of the enzyme can become fully oxidized by transferring electrons to pyrimidine substrates in the absence of NADH.

Transient power angle stability analysis and improvement strategy for parallel system of virtual synchronous generator and static var generator

SummaryVirtual synchronous generators (VSGs) can actively support the frequency and voltage of the grid and are widely used in new energy power plants. Static var generators (SVGs) can improve the reactive power–voltage drop characteristics of the VSG and increase its ability to cope with complex operating conditions. However, the interaction between the VSG and the SVG can affect the output characteristics of the VSG and thus its transient power angle stability. Therefore, this paper proposes a method for analyzing the transient power angle stability of a VSG–SVG parallel system and its improvement strategy. Firstly, based on the equivalent circuit of the parallel system, the interaction‐coupled power model and the transient power angle characteristic model are derived. On this basis, the influence law of various parameters on the transient stability of VSG is analyzed based on the phase plane method. Secondly, a strategy is proposed to improve the transient power angle stability of the VSG–SVG parallel system based on the adaptive regulation of active power, and the feasibility of the strategy is verified by comparing the phase plane diagrams before and after the improved control. Finally, the effectiveness of the proposed model and strategy is verified by Matlab/Simulink simulation.

Transient stability analysis of a grid-connected type-4 wind turbine with grid-forming control during the fault

Thanks to the ability of the inertia provision and the voltage support, the virtual synchronous generator with reactive power control (RPC) is a promising solution among various grid-forming control schemes. This paper analyzes the transient angle stability of the grid-connected type-4 wind turbine with virtual synchronous generator and reactive power control strategy during the fault. By deriving the analytical criterion with the transient energy function, various key factors on the transient stability of the system can be revealed comprehensively and jointly. Additionally, the impacts of the integral coefficient of the RPC and the power reference switching delay on the transient stability are also analyzed by plotting the phase portraits of the derived third-order large-signal model of the grid-connected wind turbine system. The analytical result can be helpful for the determination of the parameters of the grid-connected wind turbine in order to keep transient stable and keep connected with the grid during the fault. Finally, the robustness and the effectiveness of the theoretical analysis results are validated by the electromagnetic transient simulation in MATLAB/Simulink under various conditions.

The Impact of Adding Solar Panels on The Wind Turbine Performance During Transient Disturbances

Recently electrical engineers look forward to replace the conventional power grid with a smart grid. This replacement requires massive changes, one of them is the integration of distributed generations and renewable energy sources in the distribution networks of the grid. These changes may affect the transient stability of the grid. In this paper, IEEE 9-bus system is used to perform transient stability analysis for a three-phase fault contingency. A 20 MW wind turbine was installed to study its performance and impact on the transient stability of the system. Then, a 3.6 MW PV station was added to study its impact on the wind turbine performance during the contingency. ETAP® 2016 software is used for simulation. The results show that the critical clearing time (CCT) of the system increases when the wind turbine is added and decreases when the PV station is installed. The impact of PV station on the wind turbine performance is not significant and it mainly affects the reactive power of the wind turbine generator after the fault is cleared.

Transient stability analysis of dual excited synchronous generator with excitation control

A Dual Excited Synchronous Generator (DESG) has two field windings. The stability enhancement of the power system can be achieved with felicitous control of these two field windings independently. Most of the work covered in the literature is on the stability analysis of DESG and the independent control of field windings. The independent control allows different amounts of current in field windings, which leads to unequal field losses and uneven rotor heating. The drawback is minimized in this work by keeping a predetermined angle between the excitation voltages. A simple excitation control similar to IEEE static exciter, regulates the d-axis and q-axis components of voltage, termed as Excitation type-1 (ET1), is presented in this paper. Also, the excitation system presented in the literature termed in this paper as Excitation type-2 (ET2) for comparison. The modified versions of both ET1 and ET2 are also presented to get overall improvement after a disturbance. The DESG connected to an infinite bus through a double-circuit transmission line is the system under study. Transient stability analysis of DESG with both types of exciters as well as Conventional Synchronous Generator for several disturbances in the system are presented, and also the results are compared.

Computational Fluid Dynamics Insights into Chemical Vapor Deposition of Homogeneous MoS2 Film with Solid Precursors

AbstractIn this work, a comprehensive computational fluid dynamics (CFD) investigation to develop an in‐depth understanding on the fluid flow to obtain a homogenous deposition of MoS2 thin film is reported. First, the effect of substrate orientations (0, 20, 45, 70, and 90°) was simulated using ANSYS Fluent. The horizontal substrate (0°) showed a non‐uniform surface deposition rate (SDR) with relative standard deviation (RSD) of 44.1 %. The non‐uniformity gradually reduces with the increase of substrate angles and reaches the lowest for 90° with RSD of 13.1 %. The transient state analysis showed that no growth occurred for the first 8 s, followed by an SDR overshoot and finally reached a steady state >200 s. Next, the effect of horizontal separation distance (d = 1 to 6 cm) between MoO3 and the substrate is investigated. It is find that the Mo/S ratio reduces with the increase of separation distance. For d between 5 and 6 cm, the Mo/S drops by >1000 times and causes the growth environment to switch from Mo to S‐rich. This work offers a fast and cost‐effective approach to understand the fluid flow and to obtain a homogeneous deposition of MoS2 and other 2D TMD thin films.

Transient Stability Analysis of Virtual Synchronous Generator Equipped With Quadrature-Prioritized Current Limiter

A current limiter (CL), which protects virtual synchronous generators (VSGs) from overcurrents, may significantly alter the operation of the VSGs when activated. In this letter, a transient stability analysis of VSGs equipped with quadrature- (q-)prioritized CL is performed. This study shows that in addition to the instability caused by the positive feedback of the primary controller, a VSG could become unstable after large disturbances due to the failure of the inner voltage controller. In this study, a stability criterion is provided for the voltage control loop.