Energy recovery power generation type pressure reducing device and hydropower station technical water supply system thereof

Abstract

An energy recovery type power generation pressure reducing device comprises a water pump used as a prime motor, taking water from tail water of a hydropower station hydro-generator and driving a water pump impeller to rotate, the water pump impeller is connected with an asynchronous generator, the asynchronous generator is used as an intermediate link to complete conversion from water head pressure difference potential energy to electric energy, and the tail water is sent to a technical water using system after pressure reduction. The asynchronous generator is provided with a frequency conversion control device which is connected with the asynchronous generator and a power grid system, and rotation speed adjustment of the water pump and grid-connected control of the asynchronous generator are achieved. The device is simple in structure, low in noise and long in service life, pressure reduction of tail water is achieved, and the water energy utilization rate is effectively increased; the technical water supply system of the hydropower station provides technical water supply for the hydropower station by using the device, realizes water energy recovery and power generation, reduces the waste of water resources, improves the overall efficiency and benefits of the hydropower station, solves the problems of complex structure, difficulty in maintenance, low energy utilization efficiency and the like of the existing pressure reducing device, and has wide application prospects and important practical values.

Description

Technical Field

[0001] The utility model relates to the technical field of hydropower stations, in particular to an energy recovery type power generation type pressure reducing device and a technical water supply system of a hydropower station. Background Art

[0002] The technical water supply system of a hydropower station is one of its important auxiliary equipment, which is used to provide a water source with a certain flow rate, temperature and cleanliness to meet the cooling, sealing or fire fighting purposes required for power production. The existing technical water supply system of a hydropower station mainly relies on a mechanical pressure reducing valve for pressure reduction, but there are many shortcomings, such as easy damage to the diaphragm, short service life, difficult maintenance, large vibration, high noise, low energy utilization efficiency and other problems. Although there is a power generation type pressure reducing technical water supply scheme based on a turbine, it involves complex equipment such as volutes and guide vanes, and the control is complex, which is not conducive to popularization and use. Therefore, it is necessary to propose a new type of power generation type pressure reducing device to solve the problems existing in the prior art.

[0003] For example, CN220336996U is a high residual pressure power generation system for a water pipeline, in which the water inlet of the turbine is connected to the water outlet of the inlet valve through a pipeline, the water inlet of the inlet valve is connected to the water outlet of the filter through a pipeline, the water inlet of the filter is connected to the water outlet of the pipeline inlet valve through a pipeline, the tailwater pipe outlet of the turbine is connected to the water inlet of the outlet valve through a pipeline, the water outlet of the outlet valve is connected to the water inlet of the pressure reducing valve through a pipeline, the water outlet of the pressure reducing valve is connected to the water outlet valve of the pipeline through a pipeline, the main shaft of the turbine is connected to the generator shaft of the generator, and the generator is connected to the integrated control cabinet and incorporated into the power system; the device has a complex structure, and the pressure reducing function is still achieved through the pressure reducing valve To assist in achieving this, the use of pressure reducing valves results in a significant waste of surplus water energy, and the pressure reducing valves commonly used in the technical water supply systems of existing hydropower stations are mechanical pressure reducing devices, most of which are diaphragm-type throttling devices, and the diaphragms of the pressure reducing valves are often damaged, making the operating valves of the pressure reducing valves prone to rust, vibration, rupture, damage, and leakage, with a short service life and difficult maintenance, rendering the pressure reducing valves ineffective; and under high water heads, the vibrations are too large, causing metal fatigue in welding flanges and other parts, affecting the safety of the technical water supply pipelines; in addition, during the pressure reduction process, the converted pressure difference head potential energy is mostly dissipated in the form of heat energy, which is not effectively utilized and has poor economic efficiency.

[0004] In order to convert the surplus water energy that can be further utilized into electrical energy, there is an urgent need for a power generation type pressure reducing device and a technical water supply solution that utilizes a hydro-turbine generator to replace a conventional pressure reducing valve and has simple control. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide an energy recovery type power generation type pressure reducing device and its hydropower station technical water supply system, so as to solve the problems of complex structure, difficult maintenance and low energy utilization efficiency of the pressure reducing device in the prior art.

[0006] In order to solve the above technical problems, the technical solution adopted by the utility model is: an energy recovery type power generation type pressure reducing device, including a water pump, used as a prime mover, taking water from the tail water of the hydropower station turbine generator, driving the water pump impeller to rotate, the water pump impeller is connected to an asynchronous generator, the asynchronous generator is used as an intermediate link, completing the conversion of the head pressure difference potential energy to electrical energy, and the tail water is sent to the technical water system after decompression, and the asynchronous generator is provided with a frequency conversion control device, the frequency conversion control device is connected to the asynchronous generator and the power grid system, and realizes the speed regulation of the water pump and the grid connection control of the asynchronous generator. In the preferred solution, the water pump is provided with a water inlet and a water outlet, the water inlet is connected to the tail water of the hydropower station turbine generator, and the water outlet is connected to the technical water system.

[0007] In a preferred solution, the water pump adopts an axial flow pump to complete the diversion of tail water to the water pump, and the tail water pressure is used to drive the water pump impeller to rotate, and the rotating impeller drives the asynchronous generator to rotate.

[0008] In a preferred solution, the axial flow pump blades are immersed in a pool of water at the tailwater, and the impeller rotates at high speed. Under the action of the resistance generated by the blades, the water at the water inlet is continuously depressurized, axially entering and exiting, so that the water flows out along the water outlet.

[0009] In a preferred solution, the input end of the asynchronous generator is connected to the rotating impeller of the water pump, which drives the rotor of the asynchronous generator to rotate. The rotor cuts the rotating magnetic field generated by the stator to generate three-phase alternating current.

[0010] In a preferred embodiment, the asynchronous generator is an induction generator, which is an AC generator that utilizes the interaction between the rotating magnetic field in the air gap between the stator and the rotor and the induced current in the rotor winding, and the direction of rotation of the rotor is the same as that of the rotating magnetic field.

[0011] In a preferred solution, the frequency conversion control device includes two AC-DC power electronic converters, the DC sides of the two converters are connected, and their respective AC sides are connected to an asynchronous generator and a power grid, wherein the one connected to the asynchronous generator serves as a machine-side converter, and the one connected to the power grid serves as a grid-side converter.

[0012] In the preferred scheme, the frequency conversion control device is electrically connected to the asynchronous generator, using primary cable wiring and secondary wiring such as communication. The frequency conversion control device also includes a signal acquisition system and a control system. The signal acquisition system completes the collection of relevant current and voltage signals of the asynchronous generator and the machine-side converter, and sends them to the control system. The control system includes a control program and related hardware platforms, which are used to control the operation of the two converters to complete the utilization of the tail water potential energy within a reasonable range and the stable connection with the AC power grid.

[0013] The technical water supply system of a hydropower station includes any of the above-mentioned energy recovery type power generation type pressure reducing devices, which takes water from the tail water of the hydropower station's turbine generator through a water pump connected to the pipeline, and sends the reduced pressure water to the technical water system.

[0014] In a preferred solution, the technical water supply system also includes a cooling water system, the water outlet of the energy recovery type power generation type pressure reducing device is connected to the cooling water system, and the water outlet of the cooling water system eventually flows out through the tail water pipe of the hydro-generator set.

[0015] The utility model provides an energy recovery type power generation type pressure reducing device and a water supply system for a hydropower station, which has the following beneficial effects:

[0016] 1. The utility model solves the problems of complex structure, difficult maintenance and low energy utilization efficiency of the decompression device in the prior art, and has broad application prospects and important practical value;

[0017] 2. The energy recovery power generation pressure reducing device of the utility model has a simple structure, avoiding the complex mechanical structure of the conventional pressure reducing valve, and improving the reliability and durability of the device;

[0018] 3. The utility model realizes the conversion and utilization of water head pressure difference potential energy into electric energy through asynchronous generator and frequency conversion control device, thus avoiding the unnecessary waste of water energy, improving the water energy utilization rate of the hydropower station and having better economy;

[0019] 4. The energy recovery power generation pressure reducing device of the utility model has a simple structure, low noise and long service life, avoiding the complex mechanical structure and easily damaged diaphragm of the conventional pressure reducing valve, and improving the reliability and durability of the device;

[0020] 5. The control process of the utility model is simple. Compared with the water supply scheme of power generation type pressure reducing technology based on turbine, the utility model uses a simple water pump as the prime mover, and uses an asynchronous generator and a frequency conversion control device to realize grid-connected control, avoiding the use of a series of complex equipment such as volutes and guide vanes;

[0021] 6. In practical applications, the energy recovery type power generation type pressure reducing device of the utility model can be customized and optimized according to the specific conditions of the hydropower station to adapt to different working environments and working requirements. At the same time, the utility model can also be combined with other hydropower station equipment and technologies to form a more complete and efficient hydropower station technical water supply system with strong scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The utility model is further described below in conjunction with the accompanying drawings and implementation examples:

[0023] Figure 1 This is a simplified structural diagram of the energy recovery type power generation type pressure reducing device of the utility model;

[0024] Figure 2 This is a simplified structural diagram of the technical water supply system of the utility model hydropower station;

[0025] Figure 3 It is a schematic diagram of the connection of the utility model energy recovery type power generation type pressure reducing device in the hydropower station;

[0026] In the figure: water pump 1, asynchronous generator 2, frequency conversion control device 3, water inlet 4, water outlet 5, machine-side converter 6, grid-side converter 7, hydropower station turbine generator 8, technical water system 9, energy recovery type power generation type pressure reducing device 10. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0028] Example 1

[0029] like Figure 1 As shown, the energy recovery type power generation type pressure reducing device 10 includes a water pump 1, which is used as a prime mover to draw water from the tail water of the hydropower station's turbine generator 8 to drive the impeller of the water pump 1 to rotate. The impeller of the water pump 1 is connected to an asynchronous generator 2. The asynchronous generator 2 is used as an intermediate link to complete the conversion of the head pressure difference potential energy into electrical energy. After the tail water is reduced in pressure, it is sent to the technical water system 9. The asynchronous generator 2 is provided with a frequency conversion control device 3. The frequency conversion control device 3 is connected to the asynchronous generator 2 and the power grid system to realize the speed regulation of the water pump 1 and the grid-connected control of the asynchronous generator 2.

[0030] In this embodiment, the water pump 1 is provided with a water inlet 4 and a water outlet 5 , the water inlet 4 is connected to the tail water of the hydroelectric generator 8 of the hydropower station, and the water outlet 5 is connected to the technical water system 9 .

[0031] Furthermore, the water pump 1 adopts an axial flow pump to complete the diversion of tail water to the water pump 1, and the tail water pressure is used to drive the impeller of the water pump 1 to rotate, and the rotating impeller drives the asynchronous generator 2 to rotate.

[0032] Furthermore, the axial flow pump blades are immersed in the water pool at the tailwater, and the impeller rotates at high speed. Under the action of the resistance generated by the blades, the water at the water inlet 4 is continuously depressurized, axially entering and axially exiting, so that the water flows out along the water outlet 5.

[0033] Furthermore, the input end of the asynchronous generator 2 is connected to the rotating impeller of the water pump 1, driving the rotor of the asynchronous generator 2 to rotate, and the rotor cuts the rotating magnetic field generated by the stator to generate three-phase alternating current.

[0034] Furthermore, the asynchronous generator 2 is an induction generator, which is an AC generator that uses the interaction between the rotating magnetic field in the air gap between the stator and the rotor and the induced current in the rotor winding, and the direction of rotation of the rotor is the same as the direction of rotation of the rotating magnetic field.

[0035] Furthermore, the frequency conversion control device 3 includes two AC-DC power electronic converters, the DC sides of the two converters are connected, and their respective AC sides are connected to the asynchronous generator 2 and the power grid, wherein the one connected to the asynchronous generator 2 serves as the machine-side converter 6, and the one connected to the power grid serves as the grid-side converter 7.

[0036] Furthermore, the frequency conversion control device 3 is electrically connected to the asynchronous generator 2, using primary cable wiring and secondary wiring such as communication. The frequency conversion control device 3 also includes a signal acquisition system and a control system. The signal acquisition system completes the acquisition of relevant current and voltage signals of the asynchronous generator 2 and the machine-side converter 6, and sends them to the control system. The control system includes a control program and related hardware platforms for controlling the operation of the two converters to complete the utilization of the tail water potential energy within a reasonable range and the stable connection with the AC power grid.

[0037] The technical water supply system of the hydropower station includes the energy recovery type power generation type pressure reducing device 10 described in any one of the above items, which takes water from the tail water of the hydropower station's turbine generator 8 through a water pump 1 through a pipeline, and sends the reduced pressure water to the technical water system 9.

[0038] Furthermore, the technical water supply system also includes a cooling water system, and the water outlet 5 of the energy recovery type power generation type pressure reducing device 10 is connected to the cooling water system, and the water outlet of the cooling water system finally flows out through the tail water pipe of the hydro-generator set.

[0039] When in use, a water pump 1 is connected to the tailwater of the hydropower station's turbine generator 8 to take water. The water pump 1 is connected to the asynchronous generator 2. The asynchronous generator 2 is used as an intermediate link to complete the conversion of head pressure difference potential energy into electrical energy. The tailwater is decompressed after the head pressure difference potential energy conversion and sent to the cooling water system of the technical water system 9. The outlet water of the cooling water system finally flows out through the tailwater pipe of the turbine generator set; the asynchronous generator 2 is connected to the frequency conversion control device 3, and the frequency conversion control device 3 connects the asynchronous generator 2 and the power grid system to achieve grid-connected control of the asynchronous generator 2, that is, the DC sides of the two AC-DC power electronic converters of the frequency conversion control device 3 are connected, and the respective AC side machine-side converters 6 and the grid-side converter 7 connected to the power grid are connected to the asynchronous generator 2 and the power grid respectively. During the process, the signal acquisition system of the frequency conversion control device 3 completes the acquisition of relevant current and voltage signals of the asynchronous motor 2 and the machine-side converter 6, and sends them to the control system. The control system controls the operation of the two converters to complete the utilization of the tailwater potential energy within a reasonable range and the stable connection with the AC power grid.

[0040] Example 2

[0041] In another preferred embodiment, based on the above embodiment 1, Figure 1 As shown, in this embodiment, the main body of the energy recovery type power generation type pressure reducing device 10 is composed of three parts: a water pump 1, an asynchronous generator 2 and a frequency conversion control device 3. The water inlet 6 and the water outlet 7 of the water pump respectively realize the water intake and water delivery functions. The asynchronous generator 2 is connected to the water pump 1 and the frequency conversion control device 3, and the conversion of the head pressure difference potential energy to electrical energy is realized by controlling the rotation speed of the water pump 1. The frequency conversion control device 3 is composed of two AC-DC power electronic converters, wherein the machine-side converter 6 is connected to the asynchronous generator 2 to realize the control of the asynchronous generator 2; the grid-side converter 7 is connected to the power grid to realize grid-connected control.

[0042] Example 3

[0043] In another preferred embodiment, based on the above embodiments 1 and 2, as Figure 2 As shown, in the embodiment, the energy recovery type power generation type pressure reducing device 10 draws water from the tail water of the hydropower station's turbine generator 8 through a pipeline through a water pump 1, and the drawn water flows through the water pump 1, and is used for power generation and pressure relief through the energy recovery type power generation type pressure reducing device 10. After the pressure relief is completed, the water outlet 7 of the water pump 1 is connected to the technical water supply and cooling water system, and the outlet water of the cooling water system finally flows out through the tail water pipe of the turbine generator set.

[0044] In practical applications, the energy recovery type power generation type pressure reducing device 10 of the utility model can be customized and optimized according to the specific conditions of the hydropower station to adapt to different working environments and working requirements. At the same time, the utility model can also be combined with other hydropower station equipment and technologies to form a more complete and efficient hydropower station technical water supply system.

[0045] Example 4

[0046] In another preferred embodiment, based on the above embodiments 1, 2, and 3, as Figure 3 As shown, the energy recovery type power generation type pressure reducing device 10 and its technical water supply system of the underground power station of a certain hydropower station use a turbine generator set to replace the pressure reducing valve, so that part of the energy of the high-pressure water is converted into electrical energy through the turbine generator set and transmitted out. The tail water pressure of the turbine meets the water inlet pressure requirement of the water supply system, and the flow through the turbine meets the water demand of the water supply system. Its maximum head is 200 m, and it is equipped with 5 600MW turbine generator sets. Based on the research of various water supply schemes, a hybrid water supply scheme of single-unit small turbine power generation pressure reducing water supply plus gravity pressure reducing water supply is adopted. The system design is as follows Figure 3The power station is equipped with 5 horizontal shaft mixed flow units with a single unit capacity of 1250 kW. The flow rate within the full head range of the small unit can meet the cooling flow requirement of one large unit.

[0047] In the preferred scheme, the water pump 1 is provided with a water inlet 4 and a water outlet 5, the water inlet 4 is connected to the tail water of the hydropower station's turbine generator 8, and the water outlet 5 is connected to the technical water system 9; the above arrangement enables the tail water of the hydropower station's turbine generator 8 to be reused as technical water after the water pump 1 is connected to the asynchronous generator 2 to complete the conversion of the head pressure difference potential energy into electrical energy, thereby further improving the utilization rate of the system energy.

[0048] In the preferred scheme, the water pump 1 adopts an axial flow pump to complete the water diversion from tail water to the water pump 1, and the tail water pressure is used to drive the impeller of the water pump 1 to rotate, and the rotating impeller drives the asynchronous generator 2 to rotate; the above arrangement enables the water pump 1 to draw water from the tail water of the hydropower station's turbine generator 8, and the water diversion drives the impeller of the water pump 1 to rotate, thereby driving the asynchronous generator 2 to rotate and generate electricity.

[0049] In the preferred scheme, the axial flow pump blades are immersed in the water pool at the tail water, and the impeller rotates at high speed. Under the action of the resistance generated by the blades, the water at the water inlet 4 is continuously depressurized, axially entering and axially exiting, so that the water flows out along the water outlet 5; the above arrangement enables the water pump 1 to draw water from the tail water of the hydropower station's turbine generator 8, and the water drives the impeller of the water pump 1 to rotate. After the water head pressure difference potential energy is converted to reduce the pressure, the water flows out through the water outlet 5, so that the residual pressure of the tail water can be fully utilized while reducing the impact on the system, thereby further improving the reliability and safety of the system.

[0050] In the preferred scheme, the input end of the asynchronous generator 2 is connected to the rotating impeller of the water pump 1, driving the rotor of the asynchronous generator 2 to rotate, and the rotor cuts the rotating magnetic field generated by the stator to generate three-phase alternating current; the above setting enables the water pump 1 to draw water to drive the impeller of the water pump 1 to rotate, and then drives the asynchronous generator 2 to rotate and generate electricity, so that the residual pressure of the tail water can be fully utilized, while reducing the impact on the system, thereby further improving the energy utilization rate of the system.

[0051] In the preferred scheme, the asynchronous generator 2 is an induction generator, which is an AC generator that utilizes the interaction between the rotating magnetic field of the air gap between the stator and the rotor and the induced current in the rotor winding, and the direction of rotation of the rotor is the same as the direction of rotation of the rotating magnetic field; the above setting enables the function of the asynchronous generator 2 to rotate and generate electricity, so that the tail water residual pressure can be fully utilized, while reducing the impact on the system, thereby further improving the energy utilization rate of the system.

[0052] In a preferred solution, the frequency conversion control device 3 includes two AC-DC power electronic converters, the DC sides of the two converters are connected, and their respective AC sides are connected to the asynchronous generator 2 and the power grid, wherein the one connected to the asynchronous generator 2 serves as a machine-side converter 6, and the one connected to the power grid serves as a grid-side converter 7; the above arrangement enables the function of the frequency conversion control device 3 connecting the asynchronous generator 2 and the power grid to be realized, and then the grid-connected control is realized through the asynchronous generator and the frequency conversion control device 3.

[0053] In the preferred scheme, the frequency conversion control device 3 is electrically connected to the asynchronous generator 2, and adopts primary cable wiring and secondary wiring such as communication. The frequency conversion control device 3 also includes a signal acquisition system and a control system. The signal acquisition system completes the acquisition of relevant current and voltage signals of the asynchronous motor 2 and the machine-side converter 6, and sends them to the control system. The control system includes a control program and related hardware platforms for controlling the operation of the two converters to complete the utilization of the tail water potential energy within a reasonable range and the stable connection with the AC power grid; the above settings further improve the reliability and safety of the system, and are also conducive to subsequent expansion and upgrading, and grid-connected control of the entire power station.

[0054] In the preferred scheme, the technical water supply system also includes a cooling water system, and the water outlet 5 of the energy recovery type power generation type pressure reducing device 10 is connected to the cooling water system, and the water outlet of the cooling water system finally flows out through the tail water pipe of the hydro-turbine generator set; the above arrangement enables the tail water of the hydro-turbine generator 8 of the hydropower station to be fully utilized, thereby further improving the efficiency and economy of the system.

[0055] In summary, the utility model provides an energy recovery type power generation type pressure reducing device and its hydropower station technical water supply system, which solves the problems of complex structure, difficult maintenance and low energy utilization efficiency of the pressure reducing device in the prior art, and has broad application prospects and important practical value; the energy recovery type power generation type pressure reducing device 10 has a simple structure, avoids the complex mechanical structure of the conventional pressure reducing valve, and improves the reliability and life durability of the device; through the asynchronous generator and the frequency conversion control device, the conversion and utilization of the head pressure difference potential energy into electrical energy is realized, avoiding the unnecessary waste of water energy, improving the water energy utilization rate of the hydropower station, and having better economy; the energy recovery type power generation type pressure reducing device 10 of the utility model has a simple structure, low noise, and long life, and avoids the complex mechanical structure of the conventional pressure reducing valve. and easily damaged diaphragms, thereby improving the reliability and durability of the device; the control process is simple. Compared with the turbine-based power generation type pressure reducing technology water supply solution, the utility model uses a simple water pump 1 as the prime mover, and utilizes an asynchronous generator 2 and a frequency conversion control device 3 to achieve grid-connected control, thereby avoiding the use of a series of complex equipment such as volutes and guide vanes; and in actual applications, the energy recovery type power generation type pressure reducing device 10 can be customized and optimized according to the specific conditions of the hydropower station to adapt to different working environments and work requirements. At the same time, the utility model can also be combined with other hydropower station equipment and technologies to form a more complete and efficient hydropower station technology water supply system, which has strong scalability, good practicality, a wide range of applications, and high practical application value. It is widely used and promoted in national hydropower stations.

Claims

1. An energy recovery type power generation type pressure reducing device (10), characterized in that: The invention comprises a water pump (1) which is used as a prime mover and draws water from the tailwater of a hydroelectric generator (8) of a hydropower station to drive the impeller of the water pump (1) to rotate. The impeller of the water pump (1) is connected to an asynchronous generator (2). The asynchronous generator (2) is used as an intermediate link to complete the conversion of water head pressure difference potential energy into electric energy. The tailwater is decompressed and then sent to a technical water system (9). The asynchronous generator (2) is provided with a frequency conversion control device (3). The frequency conversion control device (3) is connected to the asynchronous generator (2) and a power grid system to realize the speed regulation of the water pump (1) and the grid connection control of the asynchronous generator (2).

2. The energy recovery type power generation type pressure reducing device (10) according to claim 1, characterized in that: The water pump (1) is provided with a water inlet (4) and a water outlet (5), the water inlet (4) being connected to the tail water of the hydroelectric generator (8) of the hydropower station, and the water outlet (5) being connected to the technical water system (9).

3. The energy recovery type power generation type pressure reducing device (10) according to claim 2, characterized in that: The water pump (1) adopts an axial flow pump to carry out the diversion of tail water to the water pump (1), and utilizes the tail water pressure to drive the impeller of the water pump (1) to rotate, and the rotating impeller drives the asynchronous generator (2) to rotate.

4. The energy recovery type power generation type pressure reducing device (10) according to claim 3, characterized in that: The axial flow pump blades are immersed in the water pool at the tailwater, and the impeller rotates at high speed. Under the action of the resistance generated by the blades, the water at the water inlet (4) is continuously depressurized, axially entering and axially exiting, so that the water flows out along the water outlet (5).

5. The energy recovery type power generation type pressure reducing device (10) according to claim 3, characterized in that: The input end of the asynchronous generator (2) is connected to the rotating impeller of the water pump (1), driving the rotor of the asynchronous generator (2) to rotate, and the rotor cuts the rotating magnetic field generated by the stator to generate three-phase alternating current.

6. The energy recovery type power generation type pressure reducing device (10) according to claim 5, characterized in that: The asynchronous generator (2) is an induction generator, which is an AC generator that utilizes the interaction between the rotating magnetic field in the air gap between the stator and the rotor and the induced current in the rotor winding, and the direction of rotation of the rotor is the same as the direction of rotation of the rotating magnetic field.

7. The energy recovery type power generation type pressure reducing device (10) according to claim 6, characterized in that: The frequency conversion control device (3) comprises two AC-DC power electronic converters, the DC sides of the two converters are connected, and the AC sides of the two converters are respectively connected to an asynchronous generator (2) and a power grid, wherein the one connected to the asynchronous generator (2) serves as a machine-side converter (6), and the one connected to the power grid serves as a grid-side converter (7).

8. The energy recovery type power generation type pressure reducing device (10) according to claim 7, characterized in that: The frequency conversion control device (3) is electrically connected to the asynchronous generator (2) by using primary cable wiring and secondary wiring such as communication. The frequency conversion control device (3) also includes a signal acquisition system and a control system. The signal acquisition system completes the acquisition of relevant current and voltage signals of the asynchronous generator (2) and the machine-side converter (6) and sends them to the control system. The control system includes a control program and a related hardware platform for controlling the operation of the two converters to achieve the utilization of tailwater potential energy within a reasonable range and a stable connection with the AC power grid.

9. Technical water supply system of hydropower station, characterized in that: The invention comprises an energy recovery type power generation type pressure reducing device (10) as claimed in any one of claims 1 to 8, wherein the device is connected to the tail water of the hydroelectric generator (8) of the hydropower station through a pipeline to take water, and sends the water after pressure reduction to the technical water system (9).

10. The technical water supply system of a hydropower station according to claim 9, characterized in that: The technical water supply system also includes a cooling water system. The water outlet (5) of the energy recovery type power generation type pressure reducing device (10) is connected to the cooling water system, and the water outlet of the cooling water system eventually flows out through the tail water pipe of the hydro-generator set.

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