Optimal Sliding-Mode LFC with high penetration of variable Distributed Energy Resources

  • Maksymilian Klimontowicz

Student thesis: Master's Thesis

Abstract

Frequency stability in the conventional electrical power systems is highly dependent on the active power management. During each second of power system operation active power demand changes in a random way. Some loads are being connected while others are disconnected. This operation create mismatch between generated and consumed power. From the load point of view, frequency sensitive devices like engines or clocks require quasi constant frequency to work properly. Power losses in the transmission system are frequency dependent, e.g. hysteresis and eddy currents in transformers . At the generation side, it is essential to prevent rotor angle from exceeding maximal threshold values; thus avoiding generators becoming out-of-step. There is also a third aspect, which is dictated by interconnection between power system areas. Tie line power flow is determined by contracts between utilities so within the interest of both sides it is crucial to maintain tie - line power flows as scheduled. In reality frequency regulation problem comes down to the adjustment of power outputs from generating units within strictly determined time. Many control techniques like sliding model control or robust control were proposed to solve the load frequency control problem. Sliding mode control is one of the nonlinear control techniques which provide outstanding performance over transients state and is claimed to be robust over noises and uncertainties. Moreover, current optimization methods and high performance computers allow engineers to solve complicated linear and nonlinear problems. Heuristic based genetic algorithm optimization is utilized in this work. This thesis presents a comparative study of conventional and new sliding mode control approaches towards load frequency problem. Sliding mode control is nonlinear and robust technique which reveals robustness and can be easily applied as compensator to conventional secondary frequency control loop. The aim of the new control strategy implementation is to improve transient performance of the power system. Optimal controllers are applied to the three area generalized system model and two – area nonlinear power system model to validate designed control strategies. Finally distributed energy resources are introduced to show that proposed structure outperforms conventional techniques.
Date of AwardMay 2015
Original languageAmerican English
SupervisorAmer Al Hinai (Supervisor)

Keywords

  • Distributed energy resources
  • electric power systems
  • power generation
  • transmission systems
  • electric transformers
  • Power output
  • optimization methods
  • electric load frequency.

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