英文翻译2

Dynamic extending nonlinear ������∞ control andits application to hydraulic turbine governor There exists a large class of nonlinear systems with uncertainties, such as hydraulicturbine governors, whose robust control problem is hard to solve by means ofthe existing robust control approaches. For this class of systems, this work presentsa dynamic extending H∞ controller via both differential geometry and ������∞ theory. Furthermore, based on differential game theory, it has been verified that theproposed control strategy has robustness in the sense that the disturbance can beattenuated effectively because the L2-gain from the disturbance input to the regulationoutput signal could be reduced to any given level. Thirdly, a robust controlstrategy for hydraulic turbine governor is designed according to the proposed extending������∞ control method, and has been developed into a real control equipment. Finally the field experiments are carried out which show clearly that the developedcontrol equipment can enhance transient stability of power systems more effectivelythan the conventional controller. 1 Introduction Power systems are large scale, distributed and highly nonlinear systems with complicated and fast transients, where random and exogenous disturbances, such as short-circuit faults, sudden loadshedding, generator tripping, etc, all make the system stability problem even more severe. As aresult, the advanced governor control plays an important role in improving the transient stabilityof power systems. However, the governor control of the hydraulic turbine is very complicatedsince both hydraulic system dynamics and electromechanical system transients should be considered. In addition, the water hammer effect makes the governor control even more difficult[1,2]. Inorder to deal with the nonlinearity anduncertainty (mainly exogenous disturbances) existing commonly in modern power systems, the nonlinear robust control on power systems has beenexploited actively in the last decade or so[3..12]. Many of them rely on nonlinear H∞approaches[13.15] or differential geometry methods[16,17], the main idea of which is that thenonlinear nominal model (without disturbance) of power system can be exactly linearized via state feedback, and consequently the conventional linear H∞ theory[18] can be used to design therobust control law to achieve the expected performances. It should be pointed out that, these methods mentioned above depend on the exact linearizationcondition which requires that the relative degree from the control input to the measurement outputis equal to the system’s dimension in the state space[8,19]. But unfortunately, a large class ofsystems in nature and engineering systems, such as the governor systems of hydraulic turbine, donot satisfy this condition.
and the closed-loop system is asymptotically stable when������ = ������. Roughly speaking, the aim ofthe H∞ control is twofold: one is the disturbance attenuation which means that the L2-gain inequality(2) holds; and the other is the internal stability. It was shown in refs. [15,19] that the ������∞ problem of system (1) is equivalent to solving Hamilton-Jacobi-Issass inequality, for which is no general method to solve. It was also in refs. [15,19],a novel feedback linearization H∞ method was proposed to design the nonlinear H∞ controller toprovide the robustness in the sense of L2-gain combining differential geometry techniques withlinear ������∞ theory. But for the system without considering the disturbance in(1)
and if the relative degree of the system above is less than the system’s order, from refs. [8,19], thefeedback linearization ������∞ approach fails to
In this paper, in order to deal with the class of nonlinear systems that cannot be linearized exactly,the dynamic extending������∞ control strategy is first introduced systematically by means ofdynamic state feedback and linear ������∞ theory. Then the nonlinear decentralized robust control law is derived for the hydroturbine-generator governor control. Next a real control equipment is dΒιβλιοθήκη Baiduvelopedaccording to the proposed control law. Finally, experimental tests are carried out on anOMIB power system, installed with the presented turbine governor controller, the results of which validate the proposed controller has much better performance than the conventional controller. 2 Dynamic extending H∞ control Consider the following nonlinear affine system with disturbances: ������ = ������ ������ + ������2 ������ ������ + ������1 ������ ������ ������������ = ������ ������ where x ∈ ������ ������ , u ∈ ������ ������ , w ∈ ������ ������ are state, control, and disturbance vectors, respectively; ������������ ∈ ������ ������ is the regulation output vector; f(������)������1 (������)������2 (������)and h(������) are the smooth vectorfields with relevant dimensions, satisfying f ������ = 0 and h ������ = 0. For system (1), its normal H∞ control problem can be stated as to find a small enough numberλ > 0 and a suitable state feedback control such that the closed-loop system satisfies