Primary Frequency Control of Power Systems using FACTS Controllers and Energy Storage Systems

MOLINA, MARCELO GUSTAVO

SanJuan, Argentina

Workshop; Workshop on Energy Systems - Argentina, Alemania; 2003

Instituto de Energía Eléctrica

In this work, the power system (PS) security problem is dealt with the primary frequency control (PFC). The high security requirements imposed on actual power systems demand implementation of control measures to increase the operation security margins. Because electrical generation is an electromechanical process, the primary reserve controllability is not as fast as required to face the wide range of likely disturbances in the power system. This controllability slowness causes the reduction of transient stability margins and therefore the decrease of the dynamic security. Nowadays, this situation has been made worse by the increasing number of fast solid-state-based voltage regulators, the increasing use of loads especially insensitive to frequency changes and the emergence of new deregulated markets with high competitiveness. All the realities stated above make it necessary to implement control measures aimed at improving the use of existing facilities by maintaining acceptable security levels of the PS thereby enhancing the performance of the primary frequency control. Nowadays, new devices exist that can be used for improving the PS control. Energy storage advanced solutions are a feasible alternative to decrease the generation reserve and to improve the PFC. By using proper energy storage systems (ESS), excess energy may be stored to substitute the generation reserve during the action of the primary frequency control. These actions can be performed with power converter-based flexible alternating current transmission systems (FACTS), which provide high speed and control flexibility. Based on these considerations, a PFC approach is proposed in this work that has been improved through application of STATCOM-type FACTS controllers and superconducting magnetic energy storage (SMES) devices. Two different modeling proposals of STATCOM/SMES integrated controllers are presented. Firstly, a detailed modeling is carried out of all components comprising the STATCOM/SMES and secondly, a simplified modeling is performed of the proposed controller, also known as average modeling. For both modeling approaches, two multi-level control schemes are developed in order to carry out the PFC of the electric system. The first three-level control approach is designed by using concepts of the conventional power theory whereas the second control approach is designed on the basis of the active and reactive instantaneous power in the rotating dq0 reference frame. Finally, a solution is proposed for the problem of voltage balancing on the STATCOM/SMES DC bus capacitors. All the models and control algorithms developed are validated through digital simulation on test power systems in case of several disturbances. The effectiveness of the proposed PFC approach is also demonstrated in the work.