阅读说明：本技术 一种多级发电系统及其运行方法 (Multistage power generation system and operation method thereof ) 是由 寇攀高 于 2020-05-26 设计创作，主要内容包括：本发明公开了一种多级发电系统及其运行方法,多级发电系统包括高压气系统、多级气液混合系统、多级液力发电系统、通道切换系统以及控制系统,多级气液混合系统包括第一级气液混合容器至第N级气液混合容器,N≥2；多级液力发电系统包括第一级液力发电系统至第N级液力发电系统；高压储气容器的出口与气阀一的进口相连；气阀i的出口连接第i级气液混合容器的进气口和气阀i+1的进口,1≤i≤N-1,气阀N连接第N级气液混合容器的进气口；每级气液混合容器的出液口经对应的每级液力发电系统后连接与大气压相连的蓄液容器的进口,蓄液容器的出口连接各级气液混合容器的进液口。本发明通过多级发电装置,充分将空气能转化为电能,减少能源浪费,提高能量转换率。(The invention discloses a multistage power generation system and an operation method thereof, wherein the multistage power generation system comprises a high-pressure gas system, a multistage gas-liquid mixing system, a multistage hydraulic power generation system, a channel switching system and a control system, the multistage gas-liquid mixing system comprises a first-stage gas-liquid mixing container to an Nth-stage gas-liquid mixing container, and N is more than or equal to 2; the multistage hydraulic power generation system comprises a first-stage hydraulic power generation system to an Nth-stage hydraulic power generation system; the outlet of the high-pressure gas storage container is connected with the inlet of the first gas valve; an outlet of the air valve i is connected with an air inlet of the ith-stage gas-liquid mixing container and an inlet of an air valve i +1, i is more than or equal to 1 and less than or equal to N-1, and the air valve N is connected with an air inlet of the Nth-stage gas-liquid mixing container; the liquid outlet of each stage of gas-liquid mixing container is connected with the inlet of a liquid storage container connected with the atmospheric pressure after passing through each corresponding stage of hydraulic power generation system, and the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container. According to the invention, through the multi-stage power generation device, air energy is fully converted into electric energy, energy waste is reduced, and the energy conversion rate is improved.)

1. A multi-stage power generation system is characterized by comprising a high-pressure gas system, a multi-stage gas-liquid mixing system, a multi-stage hydraulic power generation system, a channel switching system and a control system, wherein the high-pressure gas system, the multi-stage gas-liquid mixing system and the multi-stage hydraulic power generation system are connected through the channel switching system and are controlled by the control system to change the running state of the multi-stage power generation system;

the high-pressure gas system comprises at least one group of high-pressure gas subsystems, each high-pressure gas subsystem at least comprises a high-pressure gas storage container and an air compression device, and the high-pressure gas storage containers are correspondingly connected with the air compression devices;

the multistage gas-liquid mixing system comprises a first-stage gas-liquid mixing container to an Nth-stage gas-liquid mixing container, wherein N is more than or equal to 2;

the multistage hydraulic power generation system comprises a first stage hydraulic power generation system to an Nth stage hydraulic power generation system, and each stage of hydraulic power generation system at least comprises a prime motor for converting hydraulic energy and a generator thereof;

the control system comprises a control device and an air pressure control device of the multistage hydraulic power generation system, the control device of the multistage hydraulic power generation system at least has the functions of adjusting and controlling the rotating speed, the power and the opening degree of the hydraulic power generation system, and the air pressure control device has the function of realizing air pressure regulation and control through opening and closing of a control valve;

the channel switching system comprises valves and pipelines which are connected with all parts in the multi-stage power generation system;

an inlet of the air compression device is connected with external air, and an outlet of the high-pressure air storage container is connected with an inlet of the first air valve; an outlet of the air valve i is connected with an air inlet of the ith-stage gas-liquid mixing container and an inlet of an air valve i +1, i is more than or equal to 1 and less than or equal to N-1, and the air valve N is connected with an air inlet of the Nth-stage gas-liquid mixing container; the liquid outlet of each stage of gas-liquid mixing container is connected with the inlet of a liquid storage container connected with atmospheric pressure after passing through each corresponding stage of hydraulic power generation system, the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container and reflows to each stage of gas-liquid mixing container through formed pressure difference, the correspondingly connected gas-liquid mixing container and the hydraulic power generation system as well as the hydraulic power generation system and the liquid storage container are all connected through liquid valves, and the correspondingly connected liquid storage container and each stage of gas-liquid mixing container are connected through backflow liquid valves; along with the increase of the number of stages, the water head range of each stage of hydraulic power generation system is reduced, the volume of each stage of gas-liquid mixing container is increased, and the pressure intensity is reduced; when the ith-stage hydraulic power generation system generates power, the first air valve to the air valve i are all opened, liquid valves between the ith-stage gas-liquid mixing container and the ith-stage hydraulic power generation system and between the ith-stage hydraulic power generation system and the liquid storage container are opened, liquid return valves between the liquid storage container and the first stage gas-liquid mixing container to the ith-stage gas-liquid mixing container are all closed, and the opening degree of the air valve i is adjustable and used for keeping the pressure of the ith-stage gas-liquid mixing container stable.

2. The multi-stage power generation system according to claim 1, wherein an outlet of the liquid storage container is connected to a liquid inlet of each stage of the gas-liquid mixing container through a liquid return valve, a set height difference exists between the bottom of the liquid storage container and each stage of the gas-liquid mixing container, so that the differential pressure backflow is formed, and the high-pressure gas storage container and each stage of the gas-liquid mixing container are located on the same horizontal plane.

3. The multi-stage power generation system according to claim 1, wherein an outlet of the liquid storage container is connected to a liquid inlet of each stage of gas-liquid mixing container through a liquid pump and a liquid return valve, the liquid pump forms the differential pressure return, and the liquid storage container, the high-pressure gas storage container and each stage of gas-liquid mixing container are located on the same horizontal plane.

4. The multi-stage power generation system of claim 1, wherein the high pressure gas system further comprises a thermal storage and heat exchange system, the thermal storage and heat exchange system comprising at least one set of thermal storage and heat exchange subsystems, the thermal storage and heat exchange subsystems comprising at least one heat exchanger, a low temperature liquid thermal storage vessel connected to an inlet of the heat exchanger, and a high temperature liquid thermal storage vessel connected to an outlet of the heat exchanger; the high-pressure air storage container is connected with the air compression device through the heat exchanger, the outlet of the air compression device is connected with the air inlet of the heat exchanger, and the air outlet of the heat exchanger is connected with the inlet of the high-pressure air storage container.

5. The multi-stage power generation system of claim 1, wherein the prime mover comprises at least a water turbine or a hydraulic turbine having a low specific speed of 100 m-kW to 400 m-kW and an ultra-low specific speed of 1 m-kW to 100 m-kW, the prime mover and the generator of each stage having different head ranges.

6. The multi-stage power generation system of claim 1, wherein the gas-liquid mixing container is a container in which gas and liquid coexist in proportion, and the implementation manner comprises underground pit wells, underground caves, abandoned mines, developed salt wells/mines, aquifer caves, surface gas storage devices or underwater gas storage containers.

7. The multi-stage power generation system of claim 6, wherein the gas pressure in the multi-stage gas-liquid mixing system is not less than 0.13MPa, the liquid comprises water, brine or a high density liquid comprising drilling fluid, mud, silt-containing liquid or mercury.

8. The multi-stage power generation system of claim 1, wherein the control means of the multi-stage hydraulic power generation system comprises at least the prime mover, a generator speed regulation system, an excitation system, a monitoring system, and a protection system.

9. The multi-stage power generation system of claim 1, wherein the multi-stage power generation system is implemented in different terrains of rivers, lakes, oceans, islands, inland, and mountainous regions.

10. An operation method of the multi-stage power generation system according to any one of claims 1 to 9, wherein the operation state of the multi-stage power generation system is divided into an energy storage state and a power generation state, the energy storage state is realized by the high-pressure gas system, the multi-stage gas-liquid hybrid system and the control system together, and the energy storage state comprises two parts, namely liquid storage and gas storage; the power generation state is realized by the high-pressure gas system, the multi-stage gas-liquid mixing system, the multi-stage hydraulic power generation system, the channel switching system and the control system together; a method of operating the multi-stage power generation system includes the steps of:

s1, entering a storage liquid in an energy storage state: the liquid valves between the liquid storage container and the gas-liquid mixing containers at all levels are opened, and the liquid in the liquid storage container flows back to the gas-liquid mixing containers at all levels by gravity flow or pumping by the liquid pump to form pressure difference;

s2, entering energy storage state gas storage: normal pressure air is converted into high temperature and high pressure air through the air compression device, the high temperature and high pressure air is converted into normal temperature and high pressure air through the heat storage and exchange subsystem, and the normal temperature and high pressure air is stored in the high pressure air storage container;

s3, entering a power generation state: each stage of hydraulic power generation system works in sequence from a first stage of hydraulic power generation system, a gas valve I to a gas valve I are opened, liquid valves between an ith stage gas-liquid mixing container and the ith stage of hydraulic power generation system and between the ith stage of hydraulic power generation system and a liquid storage container are opened, a liquid storage container and a backflow liquid valve between the first stage gas-liquid mixing container and the ith stage gas-liquid mixing container are closed, the opening of the gas valve I is used for adjusting the pressure of the corresponding ith stage gas-liquid mixing container to keep stable, the ith stage of hydraulic power generation system generates power until the liquid level in the ith stage gas-liquid mixing container is reduced to the lowest, the i +1 stage of hydraulic power generation system generates power under the combined action of the residual pressure in a high-pressure gas storage container and the residual pressure in the first stage gas-liquid mixing container to the ith stage gas-liquid mixing container, i is not less than 1 and not more than N-1 until the liquid level in the Nth stage, the air is discharged and the process advances to step S1.

Technical Field

The invention relates to the technical field of large-scale new energy storage and conversion, in particular to a multi-stage power generation system and an operation method thereof.

Background

With the development of large-scale wind energy/photovoltaic resources, the development of wind power/photovoltaic in China keeps the strong momentum of rapid development, but the large-scale wind power/photovoltaic energy with the characteristics of randomness, intermittence, anti-adjustability, large output fluctuation and the like has great influence on the voltage stability, transient stability and frequency stability of a system when being connected into a power grid, and the wind power/photovoltaic energy is difficult to grid and difficult to absorb after grid connection. The hydroelectric generating set has the characteristics of rapid halt, high adjusting speed, wide adjusting range and the like, and has the functions of peak regulation, frequency modulation and the like in a system, however, conventional hydroelectric power plants and pumped storage power plants have limited effects on large-scale new energy storage and energy conversion and cannot absorb abundant large-scale renewable energy power such as wind power, solar energy and the like; therefore, the novel energy and surplus electric energy are converted into air energy by combining the advantages of the novel energy and the surplus electric energy in the prior art, so that the novel energy and surplus electric energy has large-scale energy storage, and the air energy is converted into electric energy through hydraulic power generation.

However, in the process of converting air energy into electric energy, when the liquid in the gas-liquid mixing container reaches the lowest liquid level and stops generating electricity, the pressure in the gas-liquid mixing container is not equal to the atmospheric pressure, and generally, the air is discharged and depressurized to prepare for storing liquid, so that the air which is not converted into electric energy can be directly discharged into the atmosphere, energy waste is caused, the conversion efficiency is reduced, and the economical efficiency is influenced. Therefore, a multistage power generation system is needed to fully convert air energy into electric energy and improve energy conversion rate.

Disclosure of Invention

Technical problem to be solved

Based on the problems, the invention provides a multi-stage power generation system and an operation method thereof.

(II) technical scheme

Based on the technical problem, the invention provides a multi-stage power generation system, which comprises a high-pressure gas system, a multi-stage gas-liquid mixing system, a multi-stage hydraulic power generation system, a channel switching system and a control system, wherein the high-pressure gas system, the multi-stage gas-liquid mixing system and the multi-stage hydraulic power generation system are connected through the channel switching system and are controlled by the control system to change the running state of the multi-stage power generation system;

the high-pressure gas system comprises at least one group of high-pressure gas subsystems, each high-pressure gas subsystem at least comprises a high-pressure gas storage container and an air compression device, and the high-pressure gas storage containers are correspondingly connected with the air compression devices;

the multistage gas-liquid mixing system comprises a first-stage gas-liquid mixing container to an Nth-stage gas-liquid mixing container, wherein N is more than or equal to 2;

the multistage hydraulic power generation system comprises a first stage hydraulic power generation system to an Nth stage hydraulic power generation system, and each stage of hydraulic power generation system at least comprises a prime motor for converting hydraulic energy and a generator thereof;

the control system comprises a control device and an air pressure control device of the multistage hydraulic power generation system, the control device of the multistage hydraulic power generation system at least has the functions of adjusting and controlling the rotating speed, the power and the opening degree of the hydraulic power generation system, and the air pressure control device has the function of realizing air pressure regulation and control through opening and closing of a control valve;

the channel switching system comprises valves and pipelines which are connected with all parts in the multi-stage power generation system;

an inlet of the air compression device is connected with external air, and an outlet of the high-pressure air storage container is connected with an inlet of the first air valve; an outlet of the air valve i is connected with an air inlet of the ith-stage gas-liquid mixing container and an inlet of an air valve i +1, i is more than or equal to 1 and less than or equal to N-1, and the air valve N is connected with an air inlet of the Nth-stage gas-liquid mixing container; the liquid outlet of each stage of gas-liquid mixing container is connected with the inlet of a liquid storage container connected with atmospheric pressure after passing through each corresponding stage of hydraulic power generation system, the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container and reflows to each stage of gas-liquid mixing container through formed pressure difference, the correspondingly connected gas-liquid mixing container and the hydraulic power generation system as well as the hydraulic power generation system and the liquid storage container are all connected through liquid valves, and the correspondingly connected liquid storage container and each stage of gas-liquid mixing container are connected through backflow liquid valves; along with the increase of the number of stages, the water head range of each stage of hydraulic power generation system is reduced, the volume of each stage of gas-liquid mixing container is increased, and the pressure intensity is reduced; when the ith-stage hydraulic power generation system generates power, the first air valve to the air valve i are all opened, liquid valves between the ith-stage gas-liquid mixing container and the ith-stage hydraulic power generation system and between the ith-stage hydraulic power generation system and the liquid storage container are opened, liquid return valves between the liquid storage container and the first stage gas-liquid mixing container to the ith-stage gas-liquid mixing container are all closed, and the opening degree of the air valve i is adjustable and used for keeping the pressure of the ith-stage gas-liquid mixing container stable.

Further, the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container through a reflux liquid valve, the bottom of the liquid storage container and each stage of gas-liquid mixing container have a set height difference, so that the differential pressure reflux is formed, and the high-pressure gas storage container and each stage of gas-liquid mixing container are located on the same horizontal plane.

Further, an outlet of the liquid storage container is connected with a liquid inlet of each stage of gas-liquid mixing container through a liquid pump and a reflux valve respectively, the liquid pump forms the differential pressure reflux, and the liquid storage container, the high-pressure gas storage container and each stage of gas-liquid mixing container are located on the same horizontal plane.

Furthermore, the high-pressure gas system also comprises a heat storage and exchange system, wherein the heat storage and exchange system comprises at least one group of heat storage and exchange subsystems, and each heat storage and exchange subsystem at least comprises a heat exchanger, a low-temperature liquid heat storage container connected with a liquid inlet of the heat exchanger, and a high-temperature liquid heat storage container connected with a liquid outlet of the heat exchanger; the high-pressure air storage container is connected with the air compression device through the heat exchanger, the outlet of the air compression device is connected with the air inlet of the heat exchanger, and the air outlet of the heat exchanger is connected with the inlet of the high-pressure air storage container.

Further, the prime motor at least comprises a water turbine or a hydraulic turbine, the low specific speed is 100 m-kW-400 m-kW, the ultra-low specific speed is 1 m-kW-100 m-kW, and the prime motor and the generator in each stage have different water head ranges.

Furthermore, the gas-liquid mixing container is a container in which gas and liquid coexist in proportion, and the implementation mode comprises the modes of an underground pit well, an underground cave, a waste mine, a developed salt well/mine, an aquifer cave, a ground gas storage device or an underwater gas storage container.

Further, the gas pressure in the multistage gas-liquid mixing system is not lower than 0.13MPa, the liquid comprises water, brine or high-density liquid, and the high-density liquid comprises drilling fluid, mud, silt-containing liquid or mercury.

Furthermore, the control device of the multistage hydraulic power generation system at least comprises the prime mover, a speed regulating system of the generator, an excitation system, a monitoring system and a protection system.

Further, the multi-stage power generation system is realized under different terrains of rivers, lakes, oceans, islands, inland and mountainous regions.

The invention also discloses an operation method of the multistage power generation system, the operation state of the multistage power generation system is divided into an energy storage state and a power generation state, the energy storage state is realized by the high-pressure gas system, the multistage gas-liquid mixing system and the control system together, and the energy storage state comprises a liquid storage part and a gas storage part; the power generation state is realized by the high-pressure gas system, the multi-stage gas-liquid mixing system, the multi-stage hydraulic power generation system, the channel switching system and the control system together; a method of operating the multi-stage power generation system includes the steps of:

s1, entering a storage liquid in an energy storage state: the liquid valves between the liquid storage container and the gas-liquid mixing containers at all levels are opened, and the liquid in the liquid storage container flows back to the gas-liquid mixing containers at all levels by gravity flow or pumping by the liquid pump to form pressure difference;

s2, entering energy storage state gas storage: normal pressure air is converted into high temperature and high pressure air through the air compression device, the high temperature and high pressure air is converted into normal temperature and high pressure air through the heat storage and exchange subsystem, and the normal temperature and high pressure air is stored in the high pressure air storage container;

s3, entering a power generation state: each stage of hydraulic power generation system works in sequence from a first stage of hydraulic power generation system, a gas valve I to a gas valve I are opened, liquid valves between an ith stage gas-liquid mixing container and the ith stage of hydraulic power generation system and between the ith stage of hydraulic power generation system and a liquid storage container are opened, a liquid storage container and a backflow liquid valve between the first stage gas-liquid mixing container and the ith stage gas-liquid mixing container are closed, the opening of the gas valve I is used for adjusting the pressure of the corresponding ith stage gas-liquid mixing container to keep stable, the ith stage of hydraulic power generation system generates power until the liquid level in the ith stage gas-liquid mixing container is reduced to the lowest, the i +1 stage of hydraulic power generation system generates power under the combined action of the residual pressure in a high-pressure gas storage container and the residual pressure in the first stage gas-liquid mixing container to the ith stage gas-liquid mixing container, i is not less than 1 and not more than N-1 until the liquid level in the Nth stage, the air is discharged and the process advances to step S1.

(III) advantageous effects

The technical scheme of the invention has the following advantages:

(1) the multistage power generation system sequentially generates power under the action of the residual pressure of the high-pressure air storage container and the front gas-liquid mixing container at each stage, and through multistage power generation, the pressure of the high-pressure air storage container and the gas-liquid mixing container at each stage is close to the atmospheric pressure, so that air is discharged when the high-pressure air cannot be reused, the high-pressure air is fully utilized, the stored high-pressure air energy is fully converted into electric energy, the loss and waste of the high-pressure air energy are reduced, and the energy conversion rate is improved;

(2) the invention reduces energy loss and improves economic benefit;

(3) the liquid storage container of the invention can automatically flow or be pumped by a liquid pump through the set elevation difference, so that the liquid flows back, and the circulation is carried out, thereby saving resources;

(4) the multi-stage power generation system is independent of terrain fall, can be realized under different terrains of rivers, lakes, oceans, islands, inland and mountainous regions, and the realization mode of the gas-liquid mixing container comprises or is not limited to the modes of underground pit wells, underground caves, abandoned mines, developed salt wells/mines, aquifer caves, ground gas storage devices or underwater gas storage containers, various liquid media are applicable, and the multi-stage power generation system is high in practicability;

(5) in the energy storage process, the heat in the high-pressure air is fully absorbed through the heat storage and exchange system, the combined heat and power supply can be realized, and the air pressure in the gas-liquid mixing container can be increased or stabilized.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic structural diagram of a first embodiment of a multi-stage power generation system according to the present invention;

FIG. 2 is a schematic structural diagram of a second embodiment of the multi-stage power generation system of the present invention;

in the figure: 1: a first air valve; 2: a second air valve; 3: a third air valve; 4: a first water valve; 5: a second water valve; 6: a third water valve; 7: a fourth water valve; 8: a fifth water valve; 9: a water valve six; 10: a first reflux valve; 11: a second reflux valve; 12: a third reflux valve; 13: a fourth reflux valve; 14: a water pump; 15: a gas-water mixing container on the B side; 16: a first-stage gas-water mixing container; 17: a second-stage gas-water mixing container; 18: a third-stage gas-water mixing container; 19: a first water turbine; 20: a second water turbine; 21: a third water turbine; 22: a high pressure gas storage tank; 23: an air storage valve; 24: an air compressor.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The invention discloses a multi-stage power generation system, which comprises a high-pressure gas system, a multi-stage gas-liquid mixing system, a multi-stage hydraulic power generation system, a channel switching system and a control system, wherein the control system changes the running state of the multi-stage power generation system, and the running state of the multi-stage power generation system is divided into an energy storage state and a power generation state: under the action of the control system, converting surplus new energy electric energy into air energy through a channel switching system and storing the air energy in a high-pressure gas system, wherein the multi-stage power generation system is in an energy storage state; under the action of the control system, air energy stored in the multi-stage power generation system is converted into electric energy through the channel switching system, the multi-stage gas-liquid mixing system and the multi-stage hydraulic power generation system, and the multi-stage power generation system is in a power generation state.

The high-pressure gas system comprises at least one group of parallel high-pressure gas subsystems and a heat storage and exchange system, each group of high-pressure gas subsystems at least comprises an air compression device and a high-pressure gas storage container which are correspondingly connected, the heat storage and exchange system comprises at least one group of heat storage and exchange subsystems, and each heat storage and exchange subsystem comprises a heat exchanger, a low-temperature liquid heat storage container connected with a liquid inlet of the heat exchanger and a high-temperature liquid heat storage container connected with a liquid outlet of the heat exchanger; the inlet of the air compression device is connected with external air, the outlet of the air compression device is connected with the air inlet of the heat exchanger, and the air outlet of the heat exchanger is connected with the inlet of the high-pressure air storage container, namely the air compression device and the high-pressure air storage container are connected through the heat storage and exchange system; the air compression device fully absorbs new energy electric energy and redundant electric energy and converts the new energy electric energy and the redundant electric energy into high-pressure air energy, and the heat storage and heat exchange system is used for increasing or stabilizing air pressure in the gas-liquid mixing container while supplying electricity and heat;

the multistage gas-liquid mixing system comprises a first-stage gas-liquid mixing container to an Nth-stage gas-liquid mixing container, wherein N is more than or equal to 2, each stage of gas-liquid mixing container is a container in which gas and liquid coexist according to a certain proportion, the implementation mode is not limited to underground pit wells, underground caves, abandoned mines, developed salt wells/mines, aquifer caves, ground gas storage devices, underwater gas storage containers and the like, the gas pressure is not lower than 0.13MPa, the liquid is not limited to working media such as water, saline water, high-density liquid and the like, all liquid media are suitable for the multistage power generation system, and the high-density liquid is not limited to drilling fluid (mud), silt-containing liquid and mercury; because the water head ranges of the hydraulic power generation systems corresponding to the gas-liquid mixing containers at all levels are different, the volume of the gas-liquid mixing containers at all levels is larger along with the increase of the levels, and the pressure intensity is reduced along with the increase of the levels, for example, a high-pressure gas storage container is a container of 100 cubic meters under 10MPa, a first-level gas-liquid mixing container is a container of 200 cubic meters under 3.1MPa when the power generation of the first-level hydraulic power generation system is finished, a second-level gas-liquid mixing container is a container of 600 cubic meters under 1.033MPa when the power generation of the second-level hydraulic power generation system is finished, a third-level gas-liquid mixing container is a container of 1800 cubic meters under 0.344MPa when the power generation of the;

the multistage hydraulic power generation system comprises a first stage hydraulic power generation system to an Nth stage hydraulic power generation system, each stage of hydraulic power generation system at least comprises one prime motor for converting liquid energy into mechanical energy and a generator thereof, and the prime motors at all stages are used for converting the energy in the liquid into the mechanical energy and then converting the mechanical energy into electric energy by the generators at all stages; the prime motor has low specific speed of 100 m.kW-400 m.kW and ultra-low specific speed of 1 m.kW-100 m.kW, and is not limited to water turbines, hydraulic turbines and other forms; the prime movers at all levels have different water head ranges, and the generator is provided with different units according to the operation water head section;

the control system comprises a control device and a pneumatic control device of the multistage hydraulic power generation system, the control device of the multistage hydraulic power generation system at least comprises the prime motor, a speed regulating system of the generator, an excitation system, a monitoring system, a protection system and the like, and the control system at least has the function of regulating and controlling the rotating speed, the power and the opening degree of the hydraulic power generation system; the air pressure control device has the function of realizing air pressure regulation and control by controlling the opening and closing of the valve;

the channel switching system comprises valves and pipelines which are connected with all parts in the multistage power generation system, and the valves are not limited to valves for cutting off airflow and water flow and control systems thereof;

an inlet of the air compression device is connected with external normal-pressure air, and an outlet of the high-pressure air storage container is connected with an inlet of the air valve I1; an outlet of the first air valve 1 is connected with an air inlet of the first-stage gas-liquid mixing container and an inlet of the second air valve 2, namely an outlet of the air valve i is connected with an air inlet of the ith-stage gas-liquid mixing container and an inlet of an air valve i +1, an air valve N is connected with an air inlet of the Nth-stage gas-liquid mixing container, and i is more than or equal to 1 and less than or equal to N-1; the liquid outlet of each stage of gas-liquid mixing container is correspondingly connected with each stage of hydraulic power generation system through a liquid valve, each stage of hydraulic power generation system is connected with the inlet of a liquid storage container connected with the atmospheric pressure through the liquid valve, and the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container through a reflux liquid valve; when the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container only through a reflux liquid valve, the bottom of the liquid storage container and each stage of gas-liquid mixing container have a set height difference, so that differential pressure reflux is formed, and the high-pressure gas storage container and each stage of gas-liquid mixing container are positioned on the same horizontal plane; when the outlet of the liquid storage container is connected with the liquid inlet of each stage of gas-liquid mixing container through a liquid pump and a reflux valve, the liquid pump forms the differential pressure reflux, and the liquid storage container, the high-pressure gas storage container and each stage of gas-liquid mixing container are positioned on the same horizontal plane. The liquid storage container may be one liquid storage container connected to each stage of gas-liquid mixing container, or may be a plurality of liquid storage containers connected to each stage of gas-liquid mixing container. Along with the increase of the number of stages, the water head range of each stage of hydraulic power generation system is reduced, the volume of each stage of gas-liquid mixing container is increased, and the pressure intensity is reduced; when the ith-stage hydraulic power generation system generates power, the first air valve to the air valve i are all opened, liquid valves between the ith-stage gas-liquid mixing container and the ith-stage hydraulic power generation system and between the ith-stage hydraulic power generation system and the liquid storage container are opened, liquid return valves between the liquid storage container and the first stage gas-liquid mixing container to the ith-stage gas-liquid mixing container are all closed, and the opening degree of the air valve i is adjustable and used for keeping the pressure of the ith-stage gas-liquid mixing container stable.

The multi-stage power generation system has an energy storage state and a power generation state, the energy storage state is realized by the high-pressure gas system, the multi-stage gas-liquid mixing system and the control system together, the energy storage state comprises a liquid storage part and a gas storage part, the gas storage part stores air in a high-pressure gas storage container through an air compression device, the liquid storage part forms pressure difference through an elevation difference self-flowing mode or the action of the liquid pump, liquid is enabled to flow back to the gas-liquid mixing containers at all stages, and the liquid backflow amount is controlled through the opening time of a backflow liquid valve; the power generation state is realized by the high-pressure gas system, the multi-stage gas-liquid mixing system, the multi-stage hydraulic power generation system, the channel switching system and the control system together, and the multi-stage hydraulic power generation system generates power hydraulically. The following is a detailed description of specific embodiments.