電力系統(tǒng)自動化課件2010frequency stability and control

1、Frequency Stability and Control9.1 Automatic Generation Controlmaintain frequency at the scheduled value (frequency control); maintain the net power interchanges with neighbouring control areas at their scheduled values(tie-line control); maintain power allocation among the units in accordance with

2、area dispatching needs (energy market, security or emergency).In some systems the role of AGC may be restricted to one or two of the above objectives.Figure 1 Structure of an electrical power system.Figure 2 Block diagram of a power generation unit.Figure 3 Steam configuration of a tandem compound s

3、ingle-reheat turbine.Typically the individual turbine stages contribute to the total turbine torque inthe ratio 30% (HP) : 40% (IP) : 30% (LP).Figure 4 Open regenerative cycle of the gas turbine.Figure 5 Example of a combined cycle gas turbine.Figure 6 Hydro turbines: (a) low- and medium-head reacti

4、on turbine; (b) high-head Pelton wheel.For adjustable-blade runners the governor can change both the blade angle and the wicket gateopening (Kaplan-type turbine).Turbine Governing SystemsFigure 7 Mechanicalhydraulic governing system of the steam turbine.Figure 8 Schematic diagram of the governing sy

5、stem: (a) mechanicalhydraulic; (b) electrohydraulic.Turbine CharacteristicsFigure 9 Turbine powerspeed characteristic for the unregulated turbine (lines 1, 2) and the regulated turbine (lines 3, 2, 4).Figure 10 Simplified model of the steam turbine governing system : block diagram with negative feed

6、back; equivalent block diagram; equivalent blockdiagram for the steady state.Figure 11 Illustration of the definition of the speeddroop coefficient.where = R/n is referred to as the speeddroop coefficient or simply the droop. The reciprocal of droop K = 1/ is the effective gain of the governing system. The definition of is illustrated inFigure 11.Figure 2.16 The equilibrium point between the turbine power and the load power: (a) stable point; (b) unstable point.9.1.1 Generation CharacteristicIn the ste