The Application Of Switching Control Theory In The Control Of Power Systems Transient Stability

Power system transient instability occurs from time to time due to the large-scale grid and heavy loading condition, which reduces the level of security and reliability of power systems.Linearized model based controllers are widely used to maintain the stable operation of power systems. However, they can hardly provide reliable performance when suffering severe external disturbances. The nonlinear control theory has been concerned about due to the feedback linearization method based on differential geometry. However, most feedback control methods require the exact parameters or measurable state variables of the system, which restrict the control performance. This paper proposes a structure switching excitation controller(SSEC) to enhance the transient stability of power systems.The switching system theory and the design method of a bang-bang funnel controller are proposed in the thesis. Only the tracking error of rotor angle is required to realize the BFC in a bang-bang manner with two control values, and only the logic operation is contained in it. If some feasibility assumptions of the BFC is satisfied, the deviation of rotor angle can be regulated within the predefined error funnels. The SSEC switches between a BFC and a conventional excitation controller(CEC) based on an appropriately designed state-dependent switching strategy. In the cases when transient instability occurs, the BFC is switched on first to regulate the deviation of rotor angle and its derivatives into predefined region, which is small enough around the equilibrium point, then the CEC is switched on to stabilize the system to the equilibrium point.The SSEC is installed on single machine infinite bus power system and New England 10-generator 39-bus power system respectively for simulation studies, in which the simplified feasibility assumptions and the selection strategy of the parameter are given. The control performance of SSEC is evaluated through simulation studies. On one hand, the control performance of SSEC is compared with that of CEC and FLC respectively, in the case that a three-phase fault occurs in the single machine infinite bus power system. On the other hand, the SSEC is assessed through the comparison with the CEC in the cases that a three-phase fault and outage of one transmission line occurs respectively in the New England 10-generator 39-bus power system.