BG67418B1 - Water storage power plant with controlled suction pressure - Google Patents

Abstract

The water storage power plant with controlled pressure finds application in modern power systems and is used as a source of balancing/regulating power and ancillary services. The water storage power plant with controlled pressure consists of at least one three-machine unit comprising a water turbine (5), a generator/motor (6) and a single-stage or multi-stage pump (7). The three machines are connected by a horizontal or vertical shaft. The power plant also comprises three sleeves as branches of a pressure pipeline (4) connected to a groundwater and water tower (3) in an upper reservoir (1). The sleeve (14) is in turn connected via a shut-off valve (13d) to an injector-suction (ejector) (15), which is arranged in a suction inlet (16) and whose regulating needle (18) is connected to the control device (17). Ribs (19) are arranged along the outer surface of the outlet of the injector-sucker (15). The suction inlet (16) is connected to a downstream reservoir (2) by means of a control valve (13f), an inlet pipeline (9) and a water tower (11). The suction inlet (16) is connected to the inlet of the impeller of the pump (7), which on the one side is connected to one of the sleeves of the pressure pipeline (4) via a regulating valve (13c) and on the other side connected to the generator/motor (6) via a coupling (12c), wherein the generator/motor (6) is connected to the turbine (5) via a connector (12a), and the turbine (5) is connected on one side to one of the sleeves of the pressure pipeline (4) via a regulating valve (13a) and on the other side to the lower tank (2) via a regulating valve (13a) and a discharge pipeline (8) ending in a water tower (10). In the power plant, according to the invention, the switching on and off of the generator/motor (6) and the pump (7) is ensured without disturbing effects on the parts of the power plant itself and of the power system, and an effective real-time regulation of the load of the generator/motor (6) is achieved.

Description

(54) WATER STORAGE POWER PLANT C CONTROLLED SUCTION EFFORT

Field of technique

The water storage power plant with controllable suction head is used in modern power systems and is used as a source of balancing/regulating energy and auxiliary services.

Prior art

Pumps have been perfected since their discovery in the Middle Ages. Proposals have been made to improve the structures and their functioning. Some disclose methods and devices for improving efficiency and security, for example [I.3] - [I.7], others present devices for easing the start-up process [I.8], others for regulating pump power [I.9] ], [I.10], etc.

The wide spread of interruptible generators from renewable primary sources in modern and future EEC increases the requirements for responsiveness (controllability) and reliability to VESPEZ. As a response, three-engine units are being improved by two approaches: i) so-called "hydraulic short-circuiting" (simultaneous operation of turbine and pump) and ii) variable-speed units [II.3], [II.4], [I .11].

Hydroelectric power plants with pumped energy storage (PESP) are the cheapest and universal source of balancing/regulating electricity and all kinds of auxiliary services in modern electric power systems (EEC) [II. 1], [II.2].

In power generation mode, the water energy stored in the upper reservoir drives a turbine that spins an electromagnetic generator to produce and feed into the grid as much electricity as set by the EEC controller.

In power user mode, the generator works as a motor that uses electricity from the grid to turn the pump that raises the water from the lower to the upper reservoir.

In one VESPEZ there can be several aggregates of differently combined machines. Known aggregates are typified into two main types, despite the presence of exceptions [I.1], [I.2], [II.3].

The first type is an assembly of two machines: a reversible generator/motor and a reversible turbine/pump, and the second type is an assembly of three machines: a turbine, a generator/motor and a pump.

In both types of units, turbine and generator start-up is fast and does not cause disturbances in the EEC, and after synchronizing, the power fed into the grid is regulated at high speed over a wide operating range.

Unlike running the turbine and generator, each revving of the motor and pump causes shock loads to the unit and EEC, leading to frequent failures. To avoid overloads, special means are applied: a spinning motor or spinning turbine, starting transformer or starting switch, frequency converter, etc. In addition, to reduce the starting load, the water from the pump impeller must be emptied, for which an installation with compressed air.

Immediately after connecting the motor to the mains, the compressed air is released from the pump and the valves of the pressure pipeline and the discharger are opened. In a few seconds, the motor is suddenly loaded to full power, determined by the flow rate and pump head. This load is practically unadjustable throughout the pump's operating time. In other words, the motor is not responsive to changes in frequency and other conditions in the power grid, such as overloads or random disturbances.

In the known three-machine units, the pressure pipeline from the upper reservoir branches into two arms immediately before the unit. One sleeve lowers the water to the turbine, and along the other sleeve the pump takes the water back up from the lower to the upper reservoir. During operation in hydraulic short-circuit mode, part of the pumped water flows through the turbine, which is a significant drawback.

Technical essence of the invention

The task of the invention is to propose a water-storage power plant, in which the start-up is facilitated and the efficiency, security and responsiveness of three-machine hydro units in pump mode are increased, without worsening the indicators in turbine mode.

The task is solved with a water storage power plant with controllable suction head, consisting of at least one unit of three machines, including a water turbine 5, a generator/motor 6 and a single-stage or multi-stage pump 7. The three machines are connected by a horizontal or vertical shaft. The water storage power plant contains three more sleeves, as branches of a pressure pipeline 4 connected to a water intake and water intake tower 3 in an upper reservoir 1. Sleeve 14 is connected in turn through a shut-off valve 13d to an injector-suction (ejector) 15 located in a suction 16 , whose regulating needle 18 is connected to a control device 17. Plate ribs 19 are located on the outer surface of the injector-suction outlet 15.

The sucker 16 is connected to the lower reservoir 2 by means of a regulating valve 13e, a suction pipeline 9 and a water intake tower 11. The sucker 16 is connected to the inlet of the impeller of the pump 7, which on the one hand is connected to one of the sleeves of the pressure pipeline 4 through a regulating valve 13c, and on the other hand is connected to the generator/motor 6 by means of a coupling 12c, the generator/motor 6 being connected to the turbine 5 via a coupling 12a, and the turbine 5 on the one hand being connected to one of the sleeves of the pressure pipeline 4 by means of a regulating valve 13a and on the other hand with the lower reservoir 2 by means of a regulating valve 13c and a discharge pipe 8 ending in a water tower 10.

The suction injector 15 can be made as a toroid 20 with holes 21 in its upper part, placed inside the suction cup 16, to which is attached an inverted cone 22, on the upper part of the outer surface, to which plate fins 19a are attached.

The injector-sucker 15 can also be realized as an external toroid 23 wrapped around the sucker 16, to which elbow-tube injector-suckers 24a, 24b and 24c, located inside the sucker 16, are attached.

The invention complements the well-known hydraulic scheme of the three-machine units, where at the end of the pressure pipeline from the upper reservoir branching into two arms, a third branch with another arm is provided. The disclosed third sleeve is a conduit, a valve, and one or a set of injectors (ejectors) that is installed in the pump suction between the impeller and the shut-off valve of the suction line.

One function of the injector-suction pump is to inject water from the discharge pipe and simultaneously suck water from the lower reservoir. Its other function is to vary the pressure and velocity of the water in front of the pump impeller, and the third is to impart vorticity to the flow in front of the impeller.

The invention makes it possible to start the pump without excessive load on the parts of the unit and without a disturbing effect on the EEC, as well as to regulate the motor load according to the economic and technical conditions of the electricity market.

The disclosed improvements replace the auxiliary installations and apparatus at known stations used to run the generator/motor and pump and to regulate their output. In addition, the energy losses in the operation of a three-machine unit with a third sleeve are smaller than the losses in the well-known "hydraulic short circuit".

The advantages of the described water storage power plant are:

• starting and stopping the pump without shock loads on the machine parts and without disturbances in the EEC, as a result of practically equal water pressure at the inlet and outlet of the pump impeller;

• cranking and starting the generator/motor and the pump without auxiliary starting devices applied in the known VESPEZ (starting motor or starting turbine, frequency converter, starting transformer or voltage switch, installation for pushing the water out of the pump by compressed air, etc.) ;

• regulating the load of the generator/motor in real time according to the needs of the power system of balancing/regulating energy and auxiliary services, depending on the economic and technical conditions in the power market.

Explanations of the attached figures

For better illustration, the figures show only the main parts of the station, which are sufficient to explain the proposed improvements, without illustrating the building parts, bearing supports and other components.

Figure 1 shows the main parts of the revealed station, by symbols and contours projected on an imaginary vertical plane passing through the axis of the three machines: turbine, generator/motor and pump.

Figure 2 shows an implementation of the pumping part of the same station by another type of injector suction.

Figure 3 represents implementation of the pumping part of the same station by means of a third type of injector suction.

Examples of implementation of the invention

Similar to the known technical solutions, the station disclosed by figure 1 consists of upper 1 and lower 2 reservoirs, water intake and water intake tower 3 in the upper reservoir 1, pressure pipeline 4, turbine

5, generator/motor 6, pump 7, discharge pipe 8 of turbine 5, suction pipe 9 of pump 7, water inlet tower 10 and water intake tower 11 from lower reservoir 2. Coupling 12a connects turbine shaft 5 to generator/motor shaft 6 , and coupling 12b connects the pump shaft to the generator/motor shaft 6. Valves 13a and 13b separate the turbine from the pressure and discharge pipelines, respectively, and valves 13c and 13e separate the pump 7 from the pressure pipeline 4 and the suction pipeline 9, respectively.

The new essential part that characterizes the exposed station is a third sleeve 14 of the pressure pipeline 4, which leads the high-pressure water from the upper reservoir 1 or from the outlet of the pump 7, through the shut-off valve 13d and through the injector-suction (ejector) 15 to the inlet on the pump impeller 7.

The operation of the injector-injector 15 is controlled by a device 17 which acts on the adjusting needle 18 as well as on the shut-off valves 13c, 13d and 13e. In the illustrated implementation, the adjusting needle 18 serves simultaneously as a shut-off valve of the injector-injector 15.

On the outer surface of the outlet of the injector-suction nozzle 15, plate ribs 19 are located, which have an involute shape similar to the shape of the vanes of the impeller. The optimal number of ribs is equal to the number of blades of the impeller. These lamellar ribs 19 change the longitudinal direction of the water flow and turn it so that at the moment of reaching the front edges of the vanes, the water particles move parallel to the vane surfaces. This reduces vortices and cavitations on the suction part of the impeller.

The control device 17 is part of an automated station control subsystem, not shown, which combines the requirements of the automatic system for regulating the frequency and exchange powers in the EEC with the restrictive conditions of the reservoirs or the technical capabilities of the machines.

The revealed improvements to the hydraulic scheme implement the following new modes of operation of the station.

The rotation of the generator/motor 6 and the pump 7 connected to it from rest to synchronous revolutions is easy and fast by rotating the turbine 5 connected to the generator/motor 6 with the closed valve 13e to the suction line from the lower reservoir and the open pressure valves 13d to the suction and 13c to the pump supercharger, as well as the open injector-suction 15, because then the water pressure at the outlet and the suction pressure at the inlet of the impeller of the pump 7 are the same, and no water rises through the pump 7, which leads to an almost zero load on the generator /motor 6.

After reaching synchronous revolutions and connecting the generator/motor 6 to the grid, the turbine 5 is disconnected via the clutch 12a and stopped. The connected generator/motor 6 and pump 7 remain in idle operation. From there, the flow rate of the pumped water and the corresponding load on the generator/motor 6 can be adjusted by the control device 17. For example, coordinated closing of the injector-suction 15 and opening of the valve 13e leads to an increase in the load on the pump 7 and the generator/motor 6 because the injection water with high pressure is reduced and the suction water from the lower reservoir 2 is increased, thereby reducing the water pressure in front of the impeller of the pump 7 and increasing the flow rate of the water raised in the upper reservoir 1. The reverse process of unloading the pump 7 and the generator/motor 6 takes place by coordinated opening of the injection nozzle 15 and closing of the valve 13e.

When the injector-suction nozzle 15 is fully opened and the valve 13e is closed, idle operation is restored. The generator/motor 6 can then be switched off and the pump 7 closed or the turbine 5 can be rotated and connected to the rotating generator/motor 6 to switch to a production mode where the pump 7 is disconnected via the coupling 12b .

When the injector-suction nozzle 15 (and/or the shut-off valve 13 d) is fully closed and when the valve 13e is fully opened to the suction pipeline 9, the pump 7 raises water with a maximum flow rate from the lower reservoir 2 to the upper reservoir 1, and the generator/motor 6 consumes maximum power from the mains, like a regular pump with uncontrolled suction.

In other ways of implementing the station, a variety of injector suckers can be used. Their design is selected depending on the size of the pump suction, the range of pressure and flow rate, as well as other hydraulic parameters.

For example, figure 2 illustrates the injector-sucker (ejector) 15, in which the third sleeve 14 of the pressure pipe 4 ends in an internal toroid 20 of the sucker 16.

The flow of water from the pressure pipe 4 is regulated by the valve 13d. From the holes 21 on the upper surface of the toroid 20, the high-pressure water is accelerated between the inner surface of the suction cup 16 and the outer surface of an inverted cone 22, in the upper part of which plate fins 19a are fixed to rotate the water flow. The middle circle of the toroid 20 serves as a channel for the water sucked from the lower reservoir 2. The clear opening of the channel is adjusted or closed by the adjusting needle 18a of the control device 17, which controls the flow of water from the lower reservoir 2, as part of the control station subsystem.

When implementing the station with a large diameter of the suction 16 and large flow rates of the pump 7, several injector-suckers, located in parallel in the suction, can be used. For example, figure 3 illustrates the sucker 16, around which an outer toroid 23 is wrapped, leading the water at high pressure to simple elbow-pipe injector-suckers 24a, 24b and 24c, the flow through which is simultaneously regulated by the valve 13d. The nozzle-suckers 24a, 24b and 24c are inclined in the direction of rotation of the impeller to give the necessary rotation to the movement of the water before it is sucked in by the vanes.

Claims (1)

Water storage power plant with controllable suction pressure, consisting of an upper reservoir (1) and a lower reservoir (2) with respective water intake and water intake towers (3), (10) and (11) and at least one unit of three machines including a water turbine (5), generator / motor (6) and single-stage or multistage pump (7), assembled to a horizontal or vertical shaft, with turbine exhaust pipe (8) (5) and pump suction line (9) of the pump (7), characterized in that the pressure pipe (4) connected to the water intake and water tower (3) of the upper reservoir (1) is branched by another sleeve (14), which is connected in turn by a shut-off valve (13d) with a suction injector (15) located in a suction cup (16), the adjusting needle (18) of which is connected to a control device (17), with plate ribs (19) arranged on the outer surface of the suction injector outlet (15) , the suction cup (16) being connected on one side to the lower reservoir (2) by means of a control valve (13e), a suction cup the pipeline (9) and the water intake tower (11), and on the other hand to the inlet of the impeller of the pump (7), which in turn is connected to one of the sleeves of the pressure pipe (4) by a regulating valve (13c) and with the generator / motor (6) by means of a coupling (12c), the generator / motor (6) being connected to the turbine (5) by means of a coupling (12a) and the turbine (5) on one side connected to the other of the pressure pipe sleeves (4) by means of a control valve (13a) and on the other hand with the lower reservoir (2) by means of a control valve (13c) and the exhaust pipe (8) ending in the water tower (10)