| Summary: | 博士 === 國立交通大學 === 電控工程研究所 === 106 === In this thesis, we discuss the nonlinear phenomenon and remote design of power systems. In face of rising environmental protection awareness, PM2.5, nuclear-free home, uncertainty regarding sustainable energy, fluctuation of international energy prices and difficulties in arranging power plant fixes due to extreme weather; power companies are unable to engage in power development. In addition, current technology is unable to control the power output from solar and wind generated energy sources so as to satisfy the ever-increasing loading requirements. This means power system often need to be operated close to their limit. Once loading exceeds the capabilities of the power system, it becomes unstable and the load voltage will descend dramatically; resulting in voltage collapse. Once this happens, there will be no choice but to restrict power usage. The general agreement on the cause of voltage collapse is due to saddle node bifurcating of the system’s equilibrium point. This means that the loading has surpassed the capabilities of the power system and equilibrium is no longer present. The balance point has all but collapsed. However, in 1992, Abed proposed the theory that loading voltage will collapse at the Hopf bifurcation point before saddle node bifurcation occurs.
In this thesis, we shall discuss the relationship between the properties of the voltage regulator and system variables such as loading, level of voltage regulation and voltage collapse. Through nonlinear analysis of the power system, one can deduce that the power system has static saddle node bifurcation as well as dynamic Hopf bifurcation. As system variable changes, cyclic fold bifurcation and amplified cycles are seen within the Hopf bifurcation cycle fluctuation. Furthermore, we discovered that transient chaos or commonly referred to as chaos occurs after amplified bifurcation cycles. These dynamic bifurcation phenomena contribute to dynamic voltage collapse while the occurrence of static saddle node bifurcation will result in static voltage collapse.
In terms of dynamic control of loading voltage, we propose four control methods to stabilize the unstable equilibrium point or cycle that arises from Hopf bifurcation: direct state feedback, washout filter, backstepping control and sliding mode control. This study proposes two different goals which utilize different items and control methods to achieve voltage regulation, control and prevent or delay bifurcation and chaos. The first method requires using the tap changer to control items and incorporating direct state feedback control and washout filter in its design. Data simulation indicates aside from achieving stable voltage, it can also reduce Hopf bifurcation period. Moreover, another method involves using static var compensator as the control (SVC) as the controlled item and implementing backstepping and sliding mode control into the design, so as to control loading voltage of power systems. Data simulation indicate that these control methods not only control the loading voltage up to par with normal standards, but also prevent delay or chaos from occurring.
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