Primary frequency control of multi-machine power systems with STATCOM-SMES: A case study

Primary frequency control (PFC) has the ability to regulate short period random variations of frequency during normal operation conditions and response to emergency rapidly. However, in the last decade, many large blackouts happened worldwide that led to serious economic losses. It allows concluding that the ability of current PFC to meet an emergency is poor, and security of power system (PS) should be improved. An alternative to effectively enhance the PFC and thus the PS security is to store exceeding energy during off-peak load periods in efficient energy storage systems (ESSs) for substituting the primary control reserve. In this sense, superconducting magnetic energy storage (SMES) in combination with a Static Synchronous Compensator (STATCOM) are capable of supplying power systems with both active and reactive powers simultaneously and very fast, and thus to enhance the system security dramatically. In this paper, a new concept of PFC based on incorporating a STATCOM coupled with a SMES device is presented. A full detailed model of the integrated STATCOM-SMES is proposed, including a pseudo 48-pulse voltage source inverter (VSI) and a two-quadrant three-level dc-dc converter as interface with the SMES. In addition, a dynamic equivalent model of the STATCOM-SMES for multi-machine power system studies is presented. The proposed simplified modeling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment using the phasor simulation method. Moreover, a three-level control scheme is designed, including a full decoupled current control strategy in the d-q reference frame with a novel controller to prevent the STATCOM dc bus capacitors voltage imbalance and an enhanced power system frequency controller. (C) 2012 Elsevier Ltd. All rights reserved.