Active and reactive power control model of superconducting magnetic energy storage (SMES) for the improvement of power system stability

Ham, Wan Kyun
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Superconducting Magnetic Energy Storage (SMES) can inject or absorb real and reactive power to or from a power system at a very fast rate on a repetitive basis. These characteristics make the application of SMES ideal for transmission grid control and stability enhancement. Superconducting Magnetic Energy Storage (SMES) is an attractive apparatus for some power system applications because it is capable of leveling load demand with high efficiency, compensating for load changes, maintaining a bus voltage, and stabilizing power swings. Power system stability problems have attracted the attention of power system engineers for several decades. Considerable progress has been made on excitation control, governor control, control by static var compensator, etc. Modern power systems, which are growing in size and complexity, are characterized by long distance bulk power transmissions and wide area interconnections. In such power systems, undamped power swings of low frequency can occur. This can be a serious problem since the instability often decreases the power transmission capacity. As a result, the power that can be transmitted in steady state and transient situations is limited. If the limit is exceeded, the generator loses synchronous operation and system instabilities occur. SMES may be an effective means of preventing these instabilities, thereby maximizing power transfer to meet increased load demand. A SMES system can be represented in dynamic simulations as a continuous controllable real and reactive power source. In steady-state simulations, SMES can be represented as a continuous controllable reactive power source since it can continuously operate throughout its range of reactive power. However, the output of real power from a SMES device is limited to the amount of energy stored in the coil. The first objective of this research is to determine the optimal internal control scheme needed to decide the controllable active and reactive power based on active and reactive power demanded by the power system. The second objective is to design and simulate SMES external control models which are dependent on the network configuration. The third objective is to determine how the optimal size of a SMES device varies for a given transient stability disturbance when alternative internal control models and external control models are used.