A New Approach for Investigation of the Turbine Generator Oscillatory Behavior Affecting Power System Quality and Reliability

2004 ◽  
Author(s):  
Rajiv Kumar ◽  
Michael Merkle ◽  
Thomas Leibfried
Keyword(s):  
Power System ◽  
Synchronous Generator ◽  
System Quality ◽  
Turbine Generator ◽  
Generator System ◽  
Rotor Shaft ◽  
Shaft System ◽  
Utility Companies ◽  
Series Capacitor Compensation ◽  
Series Capacitor

Transients following switching in the network and/or the tripping of generating unit auxiliaries can excite oscillatory torques on the turbine-generator-rotor-shaft system. The oscillations can be damped or amplified with time. Damped oscillations affect the power quality and if the oscillations grow with time they may even lead to generating unit outages (and damages) resulting in possible system instabilities. Deregulation of electricity markets has resulted in separation of Utility Companies (responsible for power generation) and Transmission Companies (responsible for power transmission). The decision making is no more under the same umbrella. Companies on both the sides have severe cost reduction focus and each side is tempted to make independent decision favourable to it. The Transmission Companies want to enhance transmission capacity of existing systems by introducing measures like series capacitor compensation. However incorporation of series capacitor compensation may under certain conditions lead to oscillations and also snbsynchronous resonance. Currently, there is an urgent need to establish a systematic methodology to investigate the root cause of such oscillations so that preventive measures can be taken by both the Utility Companies and the Transmission Companies. This paper is a contribution in this direction. In this work, comprehensive dynamic model of synchronous generator system has been developed in software Matlab/Simulink. Generating unit start up and ramp loading to rated load has been simulated to get deeper insight into the oscillatory behaviour of the synchronous generator. Block loading of the turbine generator and sudden load shedding due to auxiliary trip have been investigated in detail. Further, power system network with bus connected parallel generating units and parallel transmission lines, having different series capacitor compensation ratio have been simulated in power system software NETOMAC. Transient conditions have been modelled to investigate the oscillations and the consequent torsional torques and angles between adjacent masses of the rotor shaft system causing fatigue life reduction. This work has very clearly revealed the complex dynamic interrelationship among variables responsible for power system oscillations.

scholarly journals Renewable Energy System on Frequency Stability Control Strategy Using Virtual Synchronous Generator

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1697 ◽  
Author(s):  
Lingling Li ◽  
Hengyi Li ◽  
Ming-Lang Tseng ◽  
Huan Feng ◽  
Anthony S. F. Chiu
Keyword(s):  
Renewable Energy ◽  
Power System ◽  
Large Scale ◽  
Synchronous Generator ◽  
Frequency Stability ◽  
Stability Control ◽  
System Stability ◽  
Generator System ◽  
System Frequency ◽  
Virtual Synchronous Generator

This study constructs a novel virtual synchronous generator system based on a transfer function, and optimizes the parameters of the model by using the improved whale algorithm to improve the frequency control ability of virtual synchronous generator. Virtual synchronous generator technology helps to solve the problem that the integration of large-scale renewable energy generation into the power system leads to the deterioration of system frequency stability. It can maintain the symmetry of grid-connected scale and system stability. The virtual synchronous generator technology makes the inverter to have the inertia and damping characteristics of a synchronous generator. The inverter has the inertia characteristics and damps to reduce the frequency instability of high penetration renewable energy power system. The improved whale algorithm is efficient to find the best combination of control parameters and the effectiveness of the algorithm is verified by microgrid and power system. The results show that the proposed frequency coordination control scheme suppresses the frequency deviation of power system and keep the system frequency in a reasonable range.

scholarly journals Method to Evaluate the Impact of Integration of PMSG on Stability of Synchronous Generator Shaft Under Weak Grid Connection

2021 ◽  
Vol 9 ◽  
Author(s):  
Tianyi Zhang ◽  
Haifeng Wang
Keyword(s):  
Power System ◽  
Wind Power ◽  
Synchronous Generator ◽  
Connection Strength ◽  
Continuous Growth ◽  
Grid Connection ◽  
Shaft System ◽  
Ac Power ◽  
The Stability ◽  
The Impact

With the continuous growth in the amount of wind power accessed by the AC grid, the impact of the grid connection of wind-power generators with the power system has gradually increased. In this study, the subsynchronous oscillation of a synchronous generator (SG) shaft caused by the integration of direct-drive permanent-magnet synchronous generators (PMSGs) was investigated. The mechanism governing the effect of the connection strength between the PMSG and AC power system on the stability of the generator shaft system was analyzed based on the complex torque coefficient method. When the connection strength between the PMSG and AC power system weakens, the same voltage variation that occurs at the point of common coupling of the PMSG stimulates more intense power fluctuations in the PMSG, and the electrical damping injected by the PMSG into the SG increases considerably. This may cause the oscillation mode dominated by the generator shaft system to move to the right half of the complex plane, thereby reducing the stability of the generator shaft system. In addition, the evaluation process of the influence of the PMSG on the SG shaft system was summarized, and the proposed method can determine the stability of the AC power system after the integration of the PMSG. Finally, the effectiveness of the proposed method was validated via study cases, and conclusions were drawn. This method is expected to serve as a useful tool for the risk assessment of subsynchronous oscillations in wind farms.

scholarly journals ANALYSIS OF SUBSYNCHRONOUS RESONANCE EFFECT IN SERIES COMPENSATED LINE WITH BOOSTER TRANSFORMER

2013 ◽  
pp. 59-63
Author(s):  
G.V. RAJASEKHAR ◽  
GVSSNS SARMA
Keyword(s):  
Resonance Effect ◽  
Power Networks ◽  
Turbine Generator ◽  
Subsynchronous Resonance ◽  
Three Phase ◽  
Electric Power Networks ◽  
In Series ◽  
Negative Damping ◽  
Series Capacitor Compensation ◽  
Series Capacitor

Series compensation has been successfully employed for many years in electric power networks. Series capacitor compensation has a tendency to act as a negative damping on torsional vibrations of nearby turbine generator units. However, their presence in the system may lead to the Sub-synchronous resonance (SSR) phenomenon especially for the nearby generating plants that have a direct or a near radial connection to series capacitor compensated line. In an attempt to analyze the SSR phenomenon, analysis has been done on Second Benchmark model system using both frequency analysis and eigenvalue techniques with three phase fault for different compensation levels. This analysis has been carried out using Matlab control system toolbox.

Virtual Synchronous Generator Control of Power System including Large-scale Wind Farm by Cooperative Operation between Battery and LFC Hydro Power Plant

2020 ◽  
Vol 140 (6) ◽  
pp. 531-538
Author(s):  
Kotaro Nagaushi ◽  
Atsushi Umemura ◽  
Rion Takahashi ◽  
Junji Tamura ◽  
Atsushi Sakahara ◽  
...  
Keyword(s):  
Power Plant ◽  
Power System ◽  
Large Scale ◽  
Wind Farm ◽  
Synchronous Generator ◽  
Hydro Power ◽  
Virtual Synchronous Generator

scholarly journals Dynamics Analysis Using Koopman Mode Decomposition of a Microgrid Including Virtual Synchronous Generator-Based Inverters

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4581
Author(s):  
Yuko Hirase ◽  
Yuki Ohara ◽  
Naoya Matsuura ◽  
Takeaki Yamazaki
Keyword(s):  
Power System ◽  
System Dynamics ◽  
Dimensional Space ◽  
Supply And Demand ◽  
Transient State ◽  
Synchronous Generator ◽  
Response Analysis ◽  
Power System Dynamics ◽  
Mode Decomposition ◽  
Virtual Synchronous Generator

In the field of microgrids (MGs), steady-state power imbalances and frequency/voltage fluctuations in the transient state have been gaining prominence owing to the advancing distributed energy resources (DERs) connected to MGs via grid-connected inverters. Because a stable, safe power supply and demand must be maintained, accurate analyses of power system dynamics are crucial. However, the natural frequency components present in the dynamics make analyses complex. The nonlinearity and confidentiality of grid-connected inverters also hinder controllability. The MG considered in this study consisted of a synchronous generator (the main power source) and multiple grid-connected inverters with storage batteries and virtual synchronous generator (VSG) control. Although smart inverter controls such as VSG contribute to system stabilization, they induce system nonlinearity. Therefore, Koopman mode decomposition (KMD) was utilized in this study for consideration as a future method of data-driven analysis of the measured frequencies and voltages, and a frequency response analysis of the power system dynamics was performed. The Koopman operator is a linear operator on an infinite dimensional space, whereas the original dynamics is a nonlinear map on a finite state space. In other words, the proposed method can precisely analyze all the dynamics of the power system, which involve the complex nonlinearities caused by VSGs.

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