A coordinated control method for variable speed pumped-storage units based on working condition optimization

Abstract

The invention discloses a coordinated control method for variable speed pumped storage units based on working condition optimization. According to the comprehensive characteristic curve of the hydraulic turbine, the power and water head relationship curves at different speeds are determined, and the optimal efficiency curve is found, η imax =f(P,H,N i ), using the maximum efficiency curve and the collected current head and current power given to determine the optimal speed n in the current working condition o =f(P,H)|η max , the optimal speed n o It is the optimal speed of the variable speed unit under the current water head H and the given power P, and the speed regulation system performs closed-loop adjustment accordingly to ensure that the variable speed unit is at the optimal speed; the invention reduces the unit transition process adjustment time and improves the unit operation stability. .

Description

technical field [0001] The invention belongs to variable-speed pumped storage, in particular to a coordinated control method for variable-speed pumped-storage units based on working condition optimization. Background technique [0002] Due to its high controllability and rapid active and reactive power support for the stable operation of the power grid, variable-speed pumped storage has attracted more and more attention. The research on variable-speed pumped-storage units in my country started relatively late, and several of them have been put into operation. Seat variable-speed units are all pole-changing speed-regulating units, and the units can only switch between two speeds, and are not really variable-speed pumped-storage units. Although the research on variable speed units in foreign countries started earlier, and a large number of variable speed pumped storage units have been put into operation in Europe and Japan, their control strategies are basically divided into tw...

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Problems solved by technology

[0004] The power priority control strategy has the advantage that the AC excitation system is uniformly responsible for the control of the active and reactive power of the unit, and can provide rapid active and reactive support to the power grid, and the power control can reach hundreds of milliseconds; the disadvantage is that the transition process is accompanied by the speed of the unit. Reverse adjustment, for example, when the AC excitation system increases the output of the unit instantaneously, since the output power of the mechanical part of the unit cannot be changed instantaneously, the unit will quickly reduce the speed and use the flywheel effect to provide the required power output, but this is just opposite to the direction of the high-efficiency speed of the unit , so as to introduce disturbance to the speed regulation; if the governor control system only adopts the traditional PID control, the reverse adjustment of the speed and the rapid fluctuation will easily cause a large adjustment of the guide vane opening, which will cause the fluctuation of the water diversion system and the rapid oscillation of the unit speed , which is not conducive to the stable operation of the unit

[0005] It can be seen from the above that in the existing control strategy, the AC excitation system and the speed regulation system are independent of each other, because the AC excitation part is very fast in terms of active power, reactive power and speed adjustment, and the mechanical control system controlled by the governor Partly due to the limitation of hydraulic characteristics and mechanical characteristics, its movement is relatively slow. If the coordinated control of AC excitation and governor is not carried out, the hydraulic mechanical part will be difficult to stabilize, and the rapid change of water flow characteristics will lead to the intensification of water hammer. On the other hand, the speed range of variable speed pumped storage units is generally about ±10%, rather than variable speed operation in any frequency range. Therefore, AC excitation has different restrictions on the use of flywheel effect at different operating points of the unit. Otherwise, variable speed pumping The energy storage unit will deviate from the variable speed range, which will have an impact on the operating stability of the unit, which also requires a device to coordinate the AC excitation and speed regulation system; finally, the water pump turbine has the reverse pump characteristic. If the speed regulation system is only Taking the speed as the control variable will also aggravate the instability of the transition process

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