CN116928023A - Design method of coupling power generation system for pumping and storing energy between fan tower and underground aquifer - Google Patents

Abstract

The present invention proposes a design method for a coupling power generation system between a wind turbine tower and underground aquifer pumped storage. The wind turbine tower and the water tower are combined as the upper reservoir of the pumped storage system, and the large-capacity and large-flow water wells in the aquifer are used as The lower reservoir of pumped hydro storage uses water potential energy for pumped hydro storage and power generation. When pumping energy, a submersible vertical turbine pump is used to pump water from the underground reservoir into the water storage fan tower to store water gravity potential energy. When the stored energy is released, the water stored in the wind turbine tower is discharged back to the underground aquifer through the turbine. At this time, the turbine drives the generator to generate electricity. The present invention proposes a dual-feed coupling power generation system of wind energy and pumped storage energy, and proposes a modification and design method for the underground well system to improve the operating efficiency of the water pump/turbine, and also designs the control system function of the coupled power generation system. The invention utilizes the flexible adjustment ability of the pumped storage system to smooth the fluctuation of wind power and improve the power generation consumption level of a single wind turbine.

Description

Design method of coupled power generation system between wind turbine tower and underground aquifer pumped storage

Technical field

The invention belongs to the field of small-scale underground pumping energy storage and distributed wind power generation system design, and specifically relates to a coupling power generation system design method between a wind turbine tower and underground aquifer pumping energy storage.

Background technique

Pumped hydropower storage can improve the flexible adjustment capabilities of new energy power generation systems. It is one of the key means to build a new power system with new energy as the main body, and is one of the most effective ways to promote green and low-carbon development. On the one hand, the wind turbine industry may usher in the era of "high towers". When the height of the wind power tower increases, the wind speed at the wind turbine blades increases significantly, and the obtained single machine power will also increase. Especially in plain low wind speed areas, wind turbine towers The tubes will be built higher and higher. At present, the highest wind turbine hub in my country has reached more than 170m. It is expected that by 2025, the height of the wind turbine hub will reach 200m. On the other hand, new energy sources such as wind power are intermittent and random, and there is an urgent need to build a number of flexible energy storage facilities with rapid response, technological controllability, energy conservation and environmental protection.

Contents of the invention

In view of the problem that the wind power generation system cannot flexibly adjust the capacity requirements, the present invention proposes a coupling power generation system design method between a wind turbine tower and an underground aquifer pumped storage system, which combines a wind power tower and a water tower as a pumped storage system. The upper reservoir uses large-capacity and large-flow water wells in the aquifer as the lower reservoir for pumped water storage, and uses water potential energy for pumped water storage and power generation. Utilize the flexible adjustment capability of the pumped storage system to smooth the fluctuations of wind power and improve the consumption level of the power generated by a single wind turbine. Furthermore, the wind turbine and underground aquifer pumped storage are equivalent to approximately synchronous generators to construct New coupled synchronous power generation system. This invention utilizes the abandoned wind resources of a single wind turbine for pumped energy storage. On the one hand, it is beneficial to smoothing the fluctuations of wind power. On the other hand, it can improve the consumption level of renewable energy power generation while reducing the risk of wind power fluctuations.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A design method for a coupled power generation system between a wind turbine tower and underground aquifer pumped storage, including the following steps:

Step 1. Design a pumped storage method that combines the water tower of the wind turbine with the underground aquifer;

Step 2. Construct a variable speed constant frequency doubly-fed wind power generation system without grid-side converter;

Step 3. Select the efficiency of the underground submersible vertical turbine pump and design the underground well system;

Step 4. Design the control system functions of the wind power pumped storage coupled power generation system.

Further, in step 1, the flexible steel tower of the wind turbine is combined with the water tower to construct a water tower, and the water tower is used as an upper reservoir for pumped water storage, and at the same time, deep water wells with large capacity and large flow in the aquifer are used as groundwater. When pumping water, a submersible vertical turbine pump is used to pump water from the underground reservoir into the water tower of the fan used to store water to store water gravity potential energy; when the stored energy is released, the water tower of the fan is stored The water is discharged back to the underground aquifer by the turbine through the pressure pipe. At this time, the submersible vertical turbine pump drives the electric motor/generator to generate electrical energy. At the same time, the electrical center is set up, including power electronic equipment, for control and protection.

Further, in step 2, a variable speed constant frequency doubly-fed wind power generation system without a grid-side converter is used, and a stator-side converter of a pumped storage motor/generator is added, that is, the wind power generation system adopts a doubly-fed variable speed wind power generation system. Constant frequency generator, the aquifer underground pumped energy storage system uses a two-way permanent magnet motor/generator; the stator winding of the doubly-fed variable speed constant frequency generator is constant frequency, that is, f _s = 50Hz alternating current, which is directly connected to the external power grid, and its rotor circuit passes Inverter control realizes variable speed operation; power is transmitted to the stator side inverter of the pumped storage motor/generator through the rotor side inverter, and power can also be transmitted in the reverse direction; doubly-fed variable speed constant frequency generator rotor side inverter The maximum power transmitted by the inverter is 30% of the rated power of its stator, and the stator-side inverter of the pumped storage electric motor/generator operates in full power mode.

Further, in step 3, a submersible vertical turbine pump is used for forward pumping or in reverse turbine working conditions; the submersible vertical turbine pump includes a turbine and a water pump, and its efficiency result is: the efficiency of the turbine working condition is located 70% ~ 85%, the water pump working condition is 65 ~ 80%;

The modification design of groundwater well systems includes three methods:

1) Increase the surface area in contact with the aquifer or increase the diameter of deep water wells, thereby increasing the flow of injected water and achieving greater power generation power;

2) Recharge the aquifer and store water in the aquifer through deep water wells, that is, the water in the deep water wells penetrates into the aquifer to enrich the water or groundwater structure of the aquifer, and utilizes the well network containing a large number of water wells and the existing water resources on the ground Integration of public facilities;

3) Install expansion pipes at the bottom of the well, or dig horizontally curved well pipes or seepage pits.

Further, in step 4, the controllers of the inverter and the stator-side inverter include the following functions:

1) During pumping conditions, wind power is used to drive the motor/generator, and the motor drive strategy is used to control the stator side inverter for DC inversion;

2) Used to provide doubly-fed variable speed constant frequency generator excitation for wind turbines, by controlling the inverter and stator side inverter to simultaneously perform excitation and output rectification;

The converter and stator-side converter and its control system are located on the surface, while the submersible vertical turbine pump and electric motor/generator are located underground. A filter is used between the motor and the stator-side converter to reduce Voltage spikes due to cable line length; supercapacitors installed in the DC circuit between the converter and the stator side converter to stabilize the DC bus voltage and improve transient performance; when in off-grid operation, between the converter and the stator side converter The stator side converters are connected in parallel with backup small-capacity batteries for energy storage.

Beneficial effects:

The present invention proposes a design method for a coupled power generation system between a wind turbine tower and underground aquifer pumped energy storage, which is suitable for construction of a small wind-water complementary power generation and energy storage system in the southern plains of my country. On the one hand, aquifer pumped storage can smooth out wind power fluctuations and help effectively absorb the power generated by a single wind turbine; on the other hand, combining the wind turbine tower with the water tower can effectively utilize the gravitational potential energy of the water tower to store water. , which is an effective use of the wind turbine tower space.

Description of the drawings

Figure 1 is a schematic diagram of a coupled power generation system between wind turbines and underground aquifer pumped storage;

Figure 2(a) is a schematic diagram of the large-capacity water well modification of the unconfined layer groundwater well system;

Figure 2(b) is a schematic diagram of the horizontal well expansion of the unconfined groundwater well system;

Figure 3 is a schematic diagram of the control function logic of the coupled power generation system.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the drawings and formula derivation. It should be understood that the formula derivation process described here is only used to explain the present invention and is not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The design method of a coupled power generation system between a wind turbine tower and underground aquifer pumped storage according to the present invention includes the following steps:

Step 1: Design a pumped storage method that combines the water tower of the wind turbine with the underground aquifer:

The current development trend of wind power towers is to use flexible steel towers (flexible towers). When large-scale manufacturing companies have strong process control capabilities and advanced production techniques, wind power towers and water towers can be combined to manufacture wind power water towers. The natural frequency of the water tower is designed to be significantly lower than the impeller rotation frequency and the vibration frequency of the generator set to avoid resonance between the two. Therefore, the water tower 1 adopts a flexible steel tower combined with the water tower, and the water storage makes the tower more flexible. The water tower 1 can be used as an upper reservoir for pumped water storage, as shown in Figure 1. The aquifer underground reservoir 2 can be realized by using a large-capacity, large-flow deep water well, as shown in Figure 1.

When pumping water, the submersible vertical turbine pump 3 pumps water from the underground aquifer water source or the aquifer underground reservoir 3 into the water tower 1 used for water storage to store water gravity potential energy. When the stored energy is released, water is stored in the water tower 1 and is discharged back to the underground aquifer by the submersible vertical turbine pump 3 through the pressure pipe 4. At this time, the submersible vertical turbine pump 3 drives the electric motor/generator 5 to Generate electrical energy. This comprehensive energy storage system is most suitable for use in series with varying renewable energy sources, such as wind turbines 6, to buffer varying output and reliably supply power to users. Therefore, the elements of the power generation system coupling the water tower 1 with the aquifer underground pumped water storage include: power supply (wind turbine, power grid); the water reservoir of the water tower 1; a large-capacity, high-flow deepwater well used as aquifer water storage; integration Motor-pump turbine-generator units; electrical centers (power electronics, control, protection), etc.

Step 2: Design a variable speed constant frequency doubly-fed wind power generation system without grid-side converter:

In the underground pumping system based on wind power generation, the wind power generation of the present invention uses a doubly-fed variable speed constant frequency generator, while the power generation system coupled with underground pumping and storage in the aquifer uses a permanent magnet motor/generator.

As shown in Figure 1, the motor/generator 5 is a doubly-fed variable-speed constant-frequency generator using a wound rotor asynchronous motor. Its rotor windings are three-phase windings with a spatial position difference of 120 degrees, plus a three-phase frequency f _r The stator winding is an alternating current with a constant frequency, that is, f _s = 50Hz, and is directly connected to the external power grid. Through conversion, the frequency of the rotor winding is the alternating current with the external frequency f _r , and its equivalent rotation speed is N _r = 60 f _r /N _p . The equivalent rotation speed of the stator winding with the alternating current with the constant frequency f _s is N _s = 60 f _s /N. _p , then the motor/generator rotor speed is:

N＝60(f _s -f _r )/N _p (1)

In the formula, N _p is the number of rotor magnetic pole pairs.

The rotor circuit of the doubly-fed variable speed constant frequency generator can be controlled by the inverter 7 as shown in Figure 1 to achieve variable speed operation. In addition, its power flow is bidirectional, and the direction of power depends on the working conditions of the system. The power can be transmitted to the stator-side inverter 8 of the pumped storage electric motor/generator 5 through the rotor-side converter 7, and the power can also be transmitted in the reverse direction. The rotor-side converter of the doubly-fed variable speed constant frequency generator delivers a maximum power of 30% of its stator rated power, while the stator-side converter 8 of the pumped storage electric motor/generator 5 operates in full power mode. As shown in Figure 1, the present invention omits the grid-side converter in the doubly-fed variable-speed constant-frequency power generation system, and instead adds a stator-side converter 8 of the pumped-storage motor/generator 5.

Under random wind speeds, the pumped storage system in the present invention is used to change the input and output power of the water pump/turbine through the inverter 7 and the stator side inverter 8, which can then be used to adjust the double-fed The rotor speed of the variable speed constant frequency generator achieves variable speed capture of more wind energy, and at the same time ensures that the input grid power of the stator of the variable speed constant frequency generator can be adjusted.

Step 3: Select the efficiency of the submersible vertical turbine pump and design the groundwater well system:

The submersible vertical turbine pump 3 and the electric/generator 5 are the core of the aquifer underground pumped storage system. The present invention uses a standard centrifugal pump or a vertical turbine-type well pump that can pump water in either forward or reverse turbine operation. In order to improve the overall efficiency of the energy storage system, it is necessary to optimize the pumping cycle of the water pump turbine and the efficiency of the turbine cycle. This invention is mainly based on the data of the submersible vertical turbine pump for estimation. The result is: the efficiency of the turbine operating condition is at 70%. ~85%, and the water pump operating condition is 65~80%. The operating efficiency of the motor-generator set is generally relatively high, and it is a mature and feasible technology. The efficiency of the motor-generator used in the present invention can reach more than 96%. The rotation speed of the turbine connected to the motor of the underground pumping energy storage system is one of the factors that affects the pumping and energy storage efficiency of the energy storage power station. At the same time, the water pressure in the groundwater has a greater impact on the pumping efficiency.

In order to increase the power of the underground pumped storage system, the underground well system can be modified and the seepage pit can be used. The following parameters or influencing factors need to be considered, including the filtration coefficient or hydraulic conductivity of the geological structure around the large-capacity water well, the depth of the well water, and the diameter of the well. , well pipe design and the impact of confined or unconfined aquifers, etc. Considering the above factors, there are three main design methods for groundwater well systems: 1) Compared with the current groundwater well diameter of about 1.5 meters and its surface area of about 943 square meters, the surface area in contact with the aquifer can be increased or the diameter of the water well can be increased (Figure 2 The large-capacity water well on the middle right), thereby increasing the flow of injected water and achieving greater power generation. At the same time, increasing the surface area of the connected aquifer and the radius of action of the well will help increase the filtration coefficient or water conductivity, thereby reducing the height of the injection cone generated by well drainage and ensuring the effective water head and turbine generator output power. 2) Recharge the aquifer through water wells and store water in the aquifer, that is, enrich the water or underground structure of the aquifer by flowing water back to the well, and be able to utilize the well network containing a large number of water wells and existing water resources public facilities on the ground Combine. 3) The water level in the well will change significantly in pumping and drainage modes. In order to solve the depleted pumping state, expansion pipes can be installed at the bottom of the well, or horizontally curved well pipes or seepage pits can be excavated. For example, when a deepwater well is dry, treated drinking water needs to be recharged through supply pipelines. It is worth mentioning that the upper surface of the aquifer is called the phreatic surface. Deep water wells filter or conduct water to the aquifer. The phreatic surface closer to the deep water well is higher than that farther away from the deep water well. This is called Water cone effect. In this invention, the water injection/power generation state can form a water cone. Dependent on the surface area of the contact between the deep water well and the aquifer, as shown in Figure 2(a) and Figure 2(b), the water cone phreatic surface of a large diameter deep water well is lower than that of a small diameter deep water well.

Step 4: Design the control system functions of the wind power pumped storage coupled power generation system:

The electrical system of the wind power pumped storage coupled power generation system needs to realize the underground pumped storage function of the aquifer and connect the wind turbine, user load and main grid.

The controller of the stator-side converter 8 in the present invention has two main functions: 1) During pumping conditions, the motor is driven by wind power and a motor-driven strategy is used to control the stator-side converter 8 to perform DC inversion; 2) Provide The wind turbine is excited by a doubly-fed variable-speed constant-frequency generator. By controlling the inverter 7 and the stator-side inverter 8, the excitation and output rectification are performed simultaneously. In addition, in the present invention, the inverter 7 and the stator-side inverter 8 and their control systems are located on the surface, while the submersible vertical turbine pump 3 and the motor/generator 5 are located underground. Between the motor/generator 5 and the stator-side inverter A filter is used between the current converters 8 to attenuate voltage spikes due to the length of the cable runs. The DC line between converter 7 and stator side converter 8 is connected to a supercapacitor to stabilize the DC bus voltage and improve transient performance. In actual operation, the system may be operating off-grid, and a backup battery needs to be connected in parallel in the DC link between the converter 7 and the stator side converter 8 for energy storage. The converter 7, the stator-side converter 8 and their controllers need to ensure the function of the overall system in the following working conditions.

(1) If the electric energy generated by the fan is not used by the load, the power is allocated to the electric motor/engine 5 to drive the submersible vertical turbine pump 3 to pump water, and then the water is pumped to the water tower 1 of the fan until the water tower 1 is full .

(2) If the load power demand is large and the wind turbine power is too small, the underground pumping energy storage system is placed in power generation mode to release the stored energy until the energy reserve is used up.

(3) If the power of the wind turbine is more than the power used, and the water tower 1 of the wind turbine is full, the power will be "net metered" to the grid.

As shown in Figure 3, the wind power generated by the wind turbine is connected to the external transformer through the wind turbine interface and circuit breaker, and further supplies power to the load through the circuit breaker; on the other hand, the wind power is connected to the wind turbine side rectifier inverter and electric/power generation through the circuit breaker. The machine-side rectifier inverter is connected to provide power to the motor M. On the contrary, the motor M can be used as a pumped storage generator to supply power to the external DC side through the motor/generator side rectifier inverter. On the DC side, small-capacity battery energy storage can be connected to supercapacitors to charge and discharge externally. Finally, the system sends instructions to system controllers, turbine controllers, etc. through system control, monitoring, and user interfaces.

The system layout of the present invention includes circuit wave-controlled circuit breakers and other protection and control systems. Circuit breakers use relays or contactors as isolating elements to protect circuits. When a doubly-fed variable-speed constant-frequency generator is connected to a utility meter, the system controller must monitor and verify whether its stator-side frequency and voltage waveform are consistent with the grid. When aligned with the grid, the system controller connects the system to the grid using a closed circuit breaker.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (5)

1. A design method of a coupling power generation system for pumping and storing energy between a fan tower and an underground aquifer is characterized by comprising the following steps:

step 1, designing a water tower cylinder of a fan and an underground aquifer combined pumped storage mode;

step 2, constructing a variable speed constant frequency doubly-fed wind power generation system of the grid-side converter;

step 3, selecting the efficiency of the underground submersible vertical turbine pump, and designing an underground water well system;

and 4, designing a control system function of the wind power generation pumped storage coupling power generation system.

2. The design method of the coupling power generation system for pumping and storing energy of the fan tower and the underground aquifer as set forth in claim 1, wherein the design method comprises the following steps: in the step 1, a flexible steel tower of a fan is combined with a water tower to construct a water tower cylinder, the water tower cylinder is used as a pumped storage upper reservoir, and meanwhile, a deep water well with high capacity and high flow rate of a water-bearing layer is used as an underground reservoir; when pumping water, a submersible vertical turbine pump is adopted to pump water from an underground reservoir into a water tower cylinder of a fan for storing water, so as to store gravitational potential energy of the water; when the energy storage is released, the water in the water tower cylinder of the fan is stored, the water is discharged back to the underground aquifer through the pressure pipeline, and the submersible vertical turbine pump can push the motor/generator to generate electric energy at the moment, and meanwhile, an electric center, including power electronic equipment, is arranged for control and protection.

3. The method for designing the coupling power generation system for pumping and storing energy of the fan tower and the underground aquifer as claimed in claim 2, wherein the method comprises the following steps: in the step 2, a variable speed constant frequency doubly-fed wind power generation system without a net side converter is adopted, and a stator side converter of a pumped storage motor/generator is added, namely, the wind power generation system adopts a doubly-fed variable speed constant frequency generator, and a water-bearing layer underground pumped storage system adopts a bidirectional permanent magnet motor/generator; stator winding of doubly-fed variable-speed constant-frequency generator is constant frequency, namely f _s Alternating current of 50Hz is directly connected with an external power grid, and a rotor circuit is controlled by an inverter to realize variable speed operation; power is transferred through the rotor-side inverter to the stator-side inverter of the pumped-storage motor/generator, and power may also be transferred in reverse; the maximum power transmitted by the rotor-side converter of the doubly-fed variable speed constant frequency generator is 30% of the rated power of a stator of the doubly-fed variable speed constant frequency generator, and the stator-side converter of the pumped storage motor/generator is in a full-power operation mode.

4. The method for designing the coupled power generation system for pumping and storing energy of the fan tower and the underground aquifer according to claim 3, wherein the method comprises the following steps: in the step 3, the submersible vertical turbine pump is used for pumping water in the forward direction or is in a reverse turbine working condition; submersible vertical turbine pumps include a turbine and a water pump, the efficiency results from: the efficiency of the turbine working condition is 70-85%, and the water pump working condition is 65-80%;

the reconstruction design of the underground water well system comprises three methods:

1) The surface area contacted with the aquifer is increased or the diameter of the deep water well is increased, so that the flow rate of injected water is increased, and larger power generation is realized;

2) Supplementing the aquifer through the deep well and storing water quantity in the aquifer, namely, the water in the deep well permeates into the aquifer to enrich the water or underground water structure of the aquifer, and the well network containing a large number of wells is combined with the existing water resource public facilities on the ground;

3) By installing extension pipes at the bottom of the well, or by excavating horizontally curved well pipes or penetration pits.

5. The method for designing a pump-up energy storage coupled power generation system for a wind turbine tower and an underground aquifer according to claim 1, wherein in the step 4, the controllers of the inverter and the stator-side inverter comprise the following functions:

1) In the pumping working condition, a motor/generator is driven by wind power, and a motor driving strategy is adopted to control a stator-side converter to perform direct current inversion;

2) The double-fed variable speed constant frequency generator excitation device is used for providing excitation of the double-fed variable speed constant frequency generator of the wind turbine generator, and the excitation and the output rectification are simultaneously carried out by controlling the converter and the stator side converter;

the converters and stator side converters and their control systems are located at the surface while the submersible vertical turbine pump and motor/generator are located underground, with a filter between the motor and stator side converters to attenuate voltage spikes due to the length of the cabling; the direct current circuit between the converter and the stator side converter is provided with a super capacitor to stabilize the direct current bus voltage and improve transient performance; and when the motor is in off-grid operation, a spare small-capacity battery is connected in parallel between the current converter and the current converter at the stator side for energy storage.