Turbine Fast Valving to Aid System Stability: Benefits and Other Considerations

Feasibility of different corrective control options for the improvement of transient stability

“…The curves in Fig. 3 are typical curves obtained based on information taken from [7][8][9][11][12][13][14] which present different curves for various FV schemes, according to manufacturer information, design characteristics and field tests. All the characteristics presented in the cited references are similar and the curves in Fig.…”

“…The FV response is usually fixed and not controllable for each case. Control Valves (CV) and Intercept Valves (IV) are capable of closing together, but since IV control over 70% of the total unit power, they are the most commonly controlled [8,10,11,14,15]. The use of CV and IV would bring greater stability benefits.…”

“…However, it is not recommended because the sudden drop in pressure that occurs when both valves are closing could affect the boiler and control systems negatively [8]. It is also observed that even though the valves could take around up to 6 s to completely open again, P m reacts faster and goes back to the initial value in less time, approximately 2-3 s, as shown in [7,[11][12][13][14] where the P m output versus time curve characteristics are presented, for different turbines in a FV scheme. Initial research on FV considered feasible its application in fossil-fired and nuclear units.…”

“…Several corrective control methods for TSI exist, such as connection of braking resistors [1][2][3][4][5][6], fast valving schemes in thermal generators [7][8][9][10][11][12][13][14][15], switched series capacitors [16], switched shunt capacitors [17], FACTS devices [18], control of HVDC links [19], islanding schemes [19], and generator and load shedding [19]. Previous work reported in the literature studied each method independently focusing mainly in the modelling and in the control of the insertion-removal of the specific devices to optimize the impact on TSI; some existing comparative studies [18] analyzed similar Corrective Measures (CMs) based on FACTS devices.…”

On-line transient stability enhancement using multi-agent technique

“…After a period of dead time during which the valve remains closed, the valve will reopen to an appropriate final position µ inf . This process can be described as a fixed control logic [11], which has a fixed stroke characteristic curve as shown in Fig. (5).…”