R. M. Monteiro Pereira

Dynamic voltage stability assessment of an electric power system using trajectory sensitivity analysis

Dynamic voltage stability has been an important problem in electric power systems. The dynamic behavior of modern power networks has been experiencing significant changes mainly due to the restructuring of electric industry, the introducing of open market environment and competition. In this paper it is presented a methodology to assess the dynamic voltage stability of an electric power system using trajectory sensitivity analysis. Trajectory sensitivity analysis can provide valuable insights into the security of an electric power system. In this study it was simulated a significant load demand disturbance in a test power network. The Automatic Voltage Regulator of the generating units, the Under Load Tap Changer and loads models were taken into account. The simulation results were obtained using EUROSTAG program and post-processing module developed using the Matlab software package.

Reactive power management of a wind farm to prevent voltage collapse of an electric power system

Nowadays, the large penetration of wind power generation poses new challenges for dynamic voltage stability analysis of an electric power system. The practical importance of dynamic voltage stability analysis is to help in designing and selecting counter-measures in order to avoid voltage collapse and enhance system stability. The impact of wind integration on reactive reserve requirements is a current area of interest for renewable integration studies and power system operators. In this paper is studied a new wind power plant model with reactive power management. The active power and the frequency management are taken into account too. The developed model can be used to represent, in a simplified way, an entire wind farm in order to simulate the dynamic voltage stability of the system, whatever the technology involved in the wind turbine. The system is completely modelled by a single dynamic converter model with appropriate control loops intended to reproduce the overall response of a wind farm for different grid events, such as faults or voltage and reactive power management at the point of common coupling.

STATCOM to improve the voltage stability of an electric power system using trajectory sensitivity analysis

The voltage stability security is a very important and relevant issue in the modern power networks. The voltage instability can drive the system to a blackout. One of the methodologies to deal with this problem is analysing the trajectory sensitivity of the system. The STATCOM is an important hardware that is used to improve the voltage stability of an electric power network. The main objective of this paper is to analyse the results of different studies that were realized in a power system with wind farms. The wind farms were modelled considering that the wind turbines were equipped with pitch control coupled with a Permanent Magnet Synchronous Generator. The EUROSTAG program was used to obtain the simulation results. The Matlab software package was used for the post-processing module developed.

STATCOM to improve the voltage stability of an electric power system with high penetration of wind generation

In the last years, the high penetration of renewable energy sources, especially wind power generation poses new challenges for the dynamic voltage stability analysis of an electric power system. The wind power plants are required to be able to satisfy the voltage control strategy and reactive power demands. The wind power plants should provide the reactive power exchange with the grid, due to the present of high penetration level of wind power in the system. The exchange rate and level are specified by the transmission system operator. Wind farm model based on Permanent Magnet Synchronous Generator equipped with STATCOM was developed using the EUROSTAG software package. The automatic voltage regulators of the generating units and the turbine speed governors were modeled in detail. Different load models were used and the load tap changers were taken into account too. In order to assess the power network voltage stability several contingency were simulated. An increase of the wind speed was also took in account during the simulations. Finally, some conclusions that provide a better understanding of the dynamic voltage stability of a system using various capacities of STATCOM are pointed out.

Impact of the ULTC on the dynamic voltage collapse of an electric power system with large scale of wind generation

Voltage stability is predominantly a load stability phenomenon and solutions to voltage stability can be found by control of the load as seen from the bulk power network. A delay of the load restoration gives time for other corrective actions. The load restoration may be delayed and/or limited by certain countermeasures, such as blocking of Under Load Tap Changers (ULTC). In this paper it was studied the impact of the ULTC on the dynamic voltage collapse of an electric power system with large scale wind generation. It is used the Cigré Electric Power Network with 32 bus and three wind farms equipped with wind turbines, including pitch control coupled with a Fixed Speed Induction Generator (FSIG) and a shunt capacitor bank. The automatic voltage regulators (AVR) of the generating units and the turbine speed governors were modelled. Different load models were used and the ULTC were taken into account. Several significant disturbances were simulated in the test power network, such as the increase of the wind speed, the tripping of an overhead transmission line and three-phase short-circuits. The simulation results were obtained using the EUROSTAG software package. Finally, some conclusions that provide a better understanding of the ULTC effect on the dynamic voltage stability in a system with a large amount of wind power generation are pointed out.