Steady state and transient stability analysis of wind energy system

A simplified model of a modular multilevel converter (MMC) implemented on a high voltage direct current (HVDC) transmission system is presented in this study for the analyses of steady-state and transient stabilities. The simplified model design’s goal is to reduce the complicated modeling of the MMC circuit as well as the simulation time of the analysis. The validity of the model design has been examined using the PSCAD/EMTDC simulation program, where the simulation outcomes of the detailed model and the simplified model are contrasted. It has been established that the simplified model is accurate enough and that simulation time can be substantially decreased. It is concluded that the suggested model design is very significant as a simplified model for analyzing the steady state and transient stabilities of MMC-HVDC transmission system.

In this paper a comparative study has been performed between combined Thyristor controlled series capacitor (TCSC), Static VAR compensator (SVC) and combined TCSC, Static synchronous compensator (STATCOM) to enhance the steady state, dynamic state and transient state stability of East-West interconnected system (EWIS) of Bangladesh Power System (BPS). Two TCSCs are connected in series with both interconnectors and two SVCs and STATCOMs are connected alternatively in shunt mode at the receiving end of both interconnectors. Steady state, Modal and Transient stability analyses are performed to show the improving effect of series shunt combined compensation on stability and capacity enhancement of EWIS. In case of shunt compensation superiority of STATCOM is also shown in comparison to SVC. In both the cases of comparison series compensation level is kept identical for fair comparison.

Steady state and linear stability analysis of a supercritical water natural circulation loop

The Convertible static transmission controller is a versatile device which can be installed across a transmission transformer to extend the life time of existing transformers by partially bypassing and conditioning the substation throughput power. The proposed technology can provide several integration options with multiple operational modes. From the supervisory control point of view, a control algorithm is required to set the reference values of active and reactive power flow of CSTC converters based on the desired operating points for transformer active and reactive power. In this paper, the algebraic model of CSTC in shunt-shunt mode of operation is derived. Algebraic model of CSTC is used for steady state and transient stability analysis. Algebraic model will present the behavior of transformer power flow with respect to various operating points of CSTC converters. The P-Q transformer operating range can be obtained based on the proposed algebraic model. Dynamic performance of the CSTC system is also investigated in PSCAD/EMTDC environment. Simulation results will be presented to verify the proposed algebraic model of CSTC in shunt-shunt mode of operation based on steady state results.

Zambia still faces significant challenges in her quest to become a middle-income nation by 2030. Some of these issues include low access to clean energy technologies, low electrification rates and limited infrastructure to transport electricity. Moreover, for a country that is predominantly hydropower dependent with an 85% share, climate change induced droughts contributed to approximately a 30% power deficit in 2020 owing to reduction in the hydropower generation capacity. Two years down the line the situation has not changed much with load management anticipated to commence in the fourth quarter of 2022 with an average outage duration of 6 hours a day countrywide. However, with approximately 3000 sunshine hours per annum and an average solar insolation of 5.5 kWh/m2/day and great wind resource potential (~6 to 11 m/s) for utility scale wind power in some parts of the country at heights between 80 and 200 m above sea level (A.S.L), Zambia has potential to benefit from its immense renewable resources endowment to accelerate electricity access and decarbonization of the power sector. In 2019, RES4Africa alongside Enel Foundation and with technical expertise from CESI conducted an optimal technical-economic penetration of variable renewable energy sources (VRES) in Zambia. This study had limitations as it did not tackle site-specific geospatial mapping of VRES, nor did it delve into technical system studies to include steady state and dynamic stability analyses for the Zambian power grid owing to the large-scale VRES penetration. With this motivation in research gap, a systematic methodology was developed by the author for the potential of conducting renewable energy penetration system studies for the Zambian integrated power system for the year 2025 and 2030. Thereafter, the potential sites were mapped using QGIS before applying the formulated modelling methodology on the Zambian grid to conduct steady state and dynamic stability studies for the various scenarios and study cases (i.e., 2025 base, 2025 peak demand with VRES, 2025 peak solar, 2025 peak VRES). The results obtained using Power factory Dig SILENT modelling, and simulation software are presented as system steady state, short circuit, system inertia estimation and dynamic stability analyses. The results obtained for each scenario were compared to the base case i.e., before connecting the proposed VRES projects. Further, investigation of system adequacy and security were performed through contingency analysis. The 2025 steady state analysis for the peak VRES case revealed that the loading of the transmission lines was below 100%. With the proposed VRES projects contributing to about 68% of the total system generation under this condition, the results showed huge reduction in loadings of the transmission lines from the major power plants i.e., Kariba North and Kafue Gorge Power plants when compared to the base case results. The 2025 system inertia analysis for the peak VRES case showed a reduction in the system inertia by approximately 68.5% compared to the base case. This is because the dispatch to serve the grid load in this scenario prioritized VRES over hydropower. The 2025 short circuit analysis revealed that the largest decrease in the fault level was Kariba North Bank and Kafue gorge power stations under peak VRES condition with a reduction of 6kA owing to all the machines being switched off at Kariba North from the initial 6 while Kafue Gorge upper had 2 running machines from the initial 6 in the base case. On the other hand, an overall increase in short circuit levels was experienced across the network for the Peak demand case with VRES. In the dynamic stability analysis, fault ride through (FRT) studies were conducted to ensure that VRES plants stay connected when the AC grid voltage is temporarily reduced or increased due to a fault or large load change in the grid. Moreover, the study demonstrated that for all 2025 study cases, a general increase in rate of change of frequency (RoCoF) values was observed with increased VRES integration. However, all RoCoF values obtained were well below the 1Hz/s threshold as stipulated in the Zambian transmission grid code with both frequency nadir and zenith values being well within the 50±2.5% limits.Seeing that a large share of grid demand will be met by VRES in 2025, 2030 and beyond, detailed future research must go towards utilization of machine learning and artificial intelligence in nowcasting and day ahead short-term forecasts. This has the potential to optimize both system operations during dispatch and energy market trading both local and regional.

Integration of a Nuclear Power Plant in a Transmission Grid with a Large Penetration of Wind Generation

This article will explain how to utilize a static synchronous compensator (STATCOM) near a wind farm to restore organization voltage following framework side disturbances, for example, a line-line fault, temporary outage of a wind turbine, and unexpected load shifts. This study describes security enhancement using wind and solar cell for a multi-machine power system with integration of super capacitor (SC) and STATCOM. For SC's bidirectional DC/DC converter to be overhauled, a corresponding required regulator (PID)-important damping controller (PID-SDC) is expected. Damping properties of low-recurrence movements associated among studied multimachine power system viability of suggested SC in conjunction among PID-SDC in chipping away at presentation of investigated structure under various disruptive effect circumstances is further demonstrated utilizing time-space reproduction.

The efficient handling and distribution of electrical power consist one of the most complex and appealing research problems. Due to the interconnection of different power plants and intensity of load, which gradually changes due to continuous change in load on generating units, careful treatment of the small disturbances in a power system which may lead to severe disturbance is necessary. Stability is an essential part in electrical power system operation and control. The stability problem is related with the behavior of synchronous machine after the power system is subjected to trouble. This work presents Steady State Stability (SSS) analysis of a Jamshoro Thermal Power Plant (JTPP) by using eigenvalue analysis of the different cases by varying load at three different positions. A mathematical model has been used for the JTPP with real data in order to examine the behavior of the system and to find the eigenvalues. A Simulink model of the JTTP for waveform analysis in MATLAB/Simulink has been used without and with Power System Stabilizer (PSS). Numerical quantification of the eigenvalues under the examined cases categorizes the stability of the system. The waveforms of the system are analyzed, and in cases of instability, the proposed procedure utilizing PSS helps in maintaining the system’s usual working conditions. The eigenvalue analysis and simulation results show the behavior of synchronous machines when loading changes gradually. The existing system becomes stable after more swings, whereas by using PSS in the existing system, stable regimes are attained in less time. The obtained results demonstrate the effectiveness of the proposed solution for SSS examination and securing of the disturbances of the JTPP.

This committee report documents two-terminal HVDC system model structures for power system stability analysis. These-models are intended for steady-state and transient stability analysis. The DC system structures are limited to two-terminal links; however, the modularity of the control systems will make extension to multi-terminal systems relatively easy. The modularity of the structure will also facilitate the incorporation of newer control schemes for AC/DC systems.

A quantitative analysis of the steady state stability of a general network with arbitrary PV, PQ and slack buses is presented. Steady state stability is that property of the power network defining the constraints on the bus injections under which a steady state equilibrium exists. Necessary and sufficient conditions for steady state stability as well as an algorithm to verify these conditions are derived. The degree of steady state stability of the injections (operating points) is quantified through a computable scalar stability margin. Such a stability margin serves as a design measure with which to compare the steady state stability of different operating points or networks. This result is extended to include the important case where the injections are restricted to certain subspaces. Another result is a simple-to-verify sufficient conditions for steady state stability-in the vicinity of a feasible injection vector

Supercritical water has excellent heat transfer characteristics as a coolant for nuclear reactors. Besides it results in high thermal efficiency of the plant. However, the flow can experience instabilities in supercritical water reactors, as the density change is very large for the supercritical fluids. A computer code SUCLIN has been developed employing supercritical water properties to carry out the steady state and linear stability analysis of a SCW natural circulation loop. The conservation equations of mass, momentum and energy have been linearised by imposing small perturbation in flow rate, enthalpy, pressure and specific volume. The equations have been solved analytically to generate the characteristic equation. The roots of the equation determine the stability of the system. The code has been benchmarked against published results. Then the code has been extensively used for studying the effect of diameter, heater inlet temperature and pressure on steady state and stability behavior of a Supercritical Water Natural Circulation Loop (SCWNCL). A separate computer code NOLSTA has been developed which investigates stability characteristics of supercritical natural circulation loop using non-linear analysis. The conservation equations of mass, momentum and energy in transient form were solved numerically using finite volume method. The stable, unstable and neutrally stable points were identified by examining the amplitude of flow and temperature oscillations with time for a given set of operating conditions. The stability behavior of loop, predicted using non-linear analysis has been compared with that obtained from linear analysis. The results show that the stability maps obtained by the two methods agree qualitatively. The present paper describes the linear and nonlinear stability analysis models and the results obtained in detail.

In this article, an inference process is defined as a series of events in which the truth values flow from propositions along certain inference channels. the concepts of netlike inference process and solution searching process are then described. the notion of excitedness is defined as a measure of the activeness of thinking. In the context of an inference process, excitedness describes the truth of the proposition or the belief in the proposition. While in a solution searching process, excitedness describes the ability and/or desire to solve the problem. By introducing simple flows and their network graphs, the process of excitedness flows on the network is described be a set of differential equations with steady state solutions and stability analysis performed by applying Markov process theory. By introducing the concepts of complex flows and multi-branch graphs, the process of excitedness flows on the graph is also described by a set of differential equations with steady state solutions and stability analysis performed similar to Prigogine's theory of dissipative structures.1 Finally, the idea of using computers in netlike inference is proposed.

Haematopoietic stem cell dynamics regulate healthy blood cell production and are disrupted during leukaemia. Competition models of cellular species help to elucidate stem cell dynamics in the bone marrow microenvironment (or niche), and to determine how these dynamics impact leukaemia progression. Here we develop two models that target acute myeloid leukaemia with particular focus on the mechanisms that control proliferation via feedback signalling. It is within regions of parameter space permissive of coexistence that the effects of competition are most subtle and the clinical outcome least certain. Steady state and linear stability analyses identify parameter regions that allow for coexistence to occur, and allow us to characterise behaviour near critical points. Where analytical expressions are no longer informative, we proceed statistically and sample parameter space over a coexistence region. We find that the rates of proliferation and differentiation of healthy progenitors exert key control over coexistence. We also show that inclusion of a regulatory feedback onto progenitor cells promotes healthy haematopoiesis at the expense of leukaemia, and that – somewhat paradoxically – within the coexistence region feedback increases the sensitivity of the system to dominance by one lineage over another.

Nowadays, the hybrid power system is getting popular because of its advantage of renewable integration to the traditional power grid. In this paper, a review of the hybrid power system is presented and detailed analysis of steady state & transient stability is performed. For detailed analysis, IEEE 9 bus system has been adopted and modified for this study. The proposed isolated hybrid system consists of the wind turbine, solar PV array, energy storage system, a backup diesel generator and battery bank to study the system analysis. The hybrid wind-solar electric power system was modeled in ETAP software. The variation in power angle of the system after a three-phase fault is studied. The whole system also is studied and simulated for different case studies and combination of some outages to study the impact of disturbance in system stability.

The process of biodegradation requires the success of bacteria to colonize the reactor. In this work, we will give a sufficient condition, which is the minimum amount of nutrient that must be injected into the reactor for the bacteria to evolve, for the existence and stability of a steady state other than the washout steady state, for a coupled system of partial differential equations (PDE) modelling the bio‐denitrification process. The existence of a weak steady state is showed contrary to what is done for the ordinary differential equation (ODE) because our system consists of a coupled partial differential equations (PDE). The stability of this steady state depends on the stability of the washout steady state which is, more or less, easy to study.