A topology for a full-power variable-speed pumped-storage unit based on a flexible transmission structure

Abstract

This invention relates to the field of pumped storage technology, specifically to a full-power variable-speed pumped storage unit topology based on a flexible transmission structure; it includes an upper reservoir, a water diversion system, a surge tank, a pump-turbine, a lower reservoir, magnetic gears, a generator-motor, and a full-power converter; this invention, by introducing a flexible transmission structure based on magnetic gears to replace the coaxial connection structure of the traditional unit, can effectively prevent shaft damage during unit transitions, reduce the overall weight of the unit, and achieve optimal motor support structure. In addition, by designing the pole-slot matching scheme of the magnetic gears, it can achieve simultaneous matching of optimal unit efficiency under pumping and power generation conditions, thereby effectively improving the unit's economy.

Description

Technical Field

[0001] This invention relates to the field of pumped storage technology, specifically to a topology for a full-power variable-speed pumped storage unit based on a flexible transmission structure. Background Technology

[0002] Pumped storage technology uses water as an energy storage medium, converting electrical energy into potential energy to store and manage electrical energy. Water is pumped to an upper reservoir using electricity generated during off-peak hours, and then released to a lower reservoir to generate electricity during peak hours.

[0003] Almost all pumped storage power stations in my country use constant-speed pumped storage units, whose operating modes are relatively fixed and insufficient to cope with the large-scale, rapid power fluctuations from new energy sources that have emerged in the power grid in recent years. Compared to traditional constant-speed pumped storage units, variable-speed pumped storage units are more efficient, more flexible in operation, and respond more quickly. Among variable-speed pumped storage units, full-power variable-speed pumped storage units have the widest adjustment range and the fastest response speed, thus attracting widespread attention from the international community.

[0004] However, existing full-power variable-speed pumped-storage units generally suffer from the following problems. First, existing units all use coaxial connections, and the unbalanced torque at both ends of the shaft during transitions can easily damage the shaft system, thereby inducing low-frequency oscillations. Furthermore, existing units often use low-speed, high-torque hydro-generators, resulting in a large overall unit weight and significant limitations on planning, construction, transportation, and installation, hindering the development of distributed pumped-storage units. Finally, traditional units can only achieve optimal matching between the pump-turbine speed and the converter frequency under a single operating condition, leading to lower unit efficiency under other operating conditions and severely impacting the unit's economic viability. In conclusion, optimizing the unit topology to improve its reliability, flexibility, and economy has become a research hotspot in this field.

[0005] Therefore, the present invention provides a topology for a full-power variable-speed pumped storage unit based on a flexible transmission structure to solve the aforementioned related technical problems. Summary of the Invention

[0006] The purpose of this invention is to provide a topology for a full-power variable-speed pumped-storage unit based on a flexible transmission structure, which can effectively improve the reliability, flexibility and economy of the unit.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a topology for a full-power variable-speed pumped-storage unit based on a flexible transmission structure, including an upper reservoir, a water diversion system, a pump turbine, a lower reservoir, a magnetic gear, a generator motor, and a full-power converter;

[0009] The water diversion system is connected to the upper reservoir at one end and to the lower reservoir at the other end. The water diversion system is used to provide a path for water flow during the operation of the unit.

[0010] The water pump turbine is connected to the water intake system, and the water pump turbine is connected to the generator motor through a magnetic gear. The water pump turbine is used to realize the mutual conversion between the gravitational potential energy of the water flow and the kinetic energy of the rotor.

[0011] The generator motor is connected to the full-power converter via wires, and the generator motor is used to realize the mutual conversion between rotor kinetic energy and electrical energy.

[0012] A further embodiment of the present invention is that the water diversion system includes a water diversion pipeline, and a pressure regulating well and a ball valve are installed on the water diversion pipeline.

[0013] A further feature of the present invention is that the full-power converter is connected to an external power grid.

[0014] A further feature of the present invention is that the full-power converter is a converter with a back-to-back connection.

[0015] The invention is further configured such that: the magnetic gear is provided with an inner rotor, an outer rotor and a modulation ring, the inner rotor is connected to a generator motor, and the outer rotor and the modulation ring are both connected to a water pump turbine.

[0016] The invention is further configured such that the magnetic gear has two operating modes: a power generation mode and a water pumping mode, realizing bidirectional variable speed flexible transmission. The operating processes of the two modes are as follows:

[0017] When in power generation operation, the outer rotor is locked, while the inner rotor and modulation ring rotate.

[0018] When in pumping operation, the modulation ring is locked, and the inner and outer rotors rotate.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) The present invention introduces a flexible transmission structure to replace the traditional coaxial connection structure, which can protect the unit shaft system during the transition process, effectively avoid low-frequency oscillation caused by shaft damage, and improve the reliability of the unit.

[0021] (2) The bidirectional transmission characteristics of the magnetic gear of the present invention enable the generator motor to maintain forward rotation in both pumping and power generation conditions. As a result, the eccentric support structure with lower design and manufacturing costs and stronger support capacity can be used instead of the traditional central support structure, thus optimizing the support structure of the generator motor.

[0022] (3) The variable torque characteristics of the magnetic gear of the present invention enable the generator motor to use a high-speed, low-torque steam turbine generator instead of the traditional low-speed, high-torque hydro turbine generator, thereby greatly reducing the total weight of the unit and effectively improving the flexibility of its planning and construction.

[0023] (4) The speed change characteristics of the magnetic gear of the present invention enable the optimal speed of the pump turbine and the optimal frequency of the full-power converter to be matched under the pumping and power generation conditions of the unit through a specific pole pair design, thereby effectively improving the overall efficiency and economic efficiency of the unit. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the topology of the full-power variable-speed pumped-storage unit based on a flexible transmission structure according to the present invention;

[0026] Figure 2 This is a schematic diagram of the magnetic gear structure in the topology of the full-power variable-speed pumped-storage unit based on a flexible transmission structure according to the present invention;

[0027] Figure 3 This is a torque curve diagram of the present invention.

[0028] Legend: 100, Upper reservoir; 200, Water diversion system; 300, Surge well; 400, Pump turbine; 500, Lower reservoir; 600, Magnetic gear; 610, Inner rotor; 620, Outer rotor; 630, Modulation ring; 700, Generator motor; 800, Full-power converter. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Example

[0033] like Figures 1-3 As shown, this embodiment provides a topology for a full-power variable-speed pumped-storage unit based on a flexible transmission structure, including an upper reservoir 100, a water intake system 200, a pump-turbine 400, a lower reservoir 500, a magnetic gear 600, a generator-motor 700, and a full-power converter 800. One end of the water intake system 200 is connected to the upper reservoir 100, and the other end is connected to the lower reservoir 500. The water intake system 200 provides a pathway for water flow during unit operation. The pump-turbine 400 is connected to the water intake system 200, and the pump-turbine 400 is connected to the generator-motor 700 through the magnetic gear 600. The pump-turbine 400 is used to realize the mutual conversion between the gravitational potential energy of the water flow and the kinetic energy of the rotor. The generator-motor 700 is connected to the full-power converter 800 through wires. The generator-motor 700 is used to realize the mutual conversion between the kinetic energy of the rotor and the electrical energy.

[0034] In this embodiment, it should be noted that the water pump turbine 400 can operate in both pumping and power generation modes. Its speed or power can be controlled by adjusting the guide vane opening. Its function is to realize the mutual conversion between the gravitational potential energy of the water flow and the kinetic energy of the rotor. The generator motor 700 can adopt the structure of electric excitation and permanent magnet, etc. It can operate in both motor and generator modes. Its function is to realize the mutual conversion between rotor kinetic energy and electrical energy.

[0035] In this invention, the water diversion system 200 includes a water diversion pipe, on which a pressure regulating well 300 and a ball valve are installed.

[0036] In this embodiment, it should be noted that the surge tank 300 is used to reduce the impact of water hammer on the unit, and the ball valve (not shown in the figure) is used to control the flow rate of water in the water intake system 200. The overall function of the water intake system 200 is to provide a path for water flow during unit operation.

[0037] In this invention, the full-power converter 800 is connected to an external power grid.

[0038] In this embodiment, it should be noted that the generator motor 700 is connected to the power grid via a full-power converter 800 and can operate in both motor and generator modes, with the function of realizing the mutual conversion between rotor kinetic energy and electrical energy.

[0039] In this invention, the full-power converter 800 is a converter with a back-to-back connection.

[0040] In this embodiment, it should be noted that all the power generated by the generator motor 700 is converted by the full-power converter 800 and then input into the grid. The converter adopts a corresponding control strategy to achieve stable control of the unit's speed or power, and its function is to achieve stable grid-connected operation of the generator motor 700.

[0041] In this invention, the magnetic gear 600 is provided with an inner rotor 610, an outer rotor 620 and a modulation ring 630. The inner rotor 610 is connected to a generator motor 700, and the outer rotor 620 and the modulation ring 630 are both connected to a water pump turbine 400.

[0042] In this embodiment, it should be noted that the number of pole pairs of the inner rotor 610, outer rotor 620, and modulation ring 630 satisfies the magnetic field modulation relationship. The inner rotor 610 and outer rotor 620 are equipped with permanent magnets with different numbers of pole pairs, while the modulation ring 630 is composed of toothed magnets.

[0043] In this invention, the magnetic gear 600 has two operating modes: power generation and pumping, realizing bidirectional variable speed flexible transmission. The operating process of the two modes is as follows:

[0044] When in power generation operation, the outer rotor 620 is locked, while the inner rotor 610 and modulation ring 630 rotate.

[0045] When in pumping operation, the modulation ring 630 is locked, and the inner rotor 610 and outer rotor 620 rotate.

[0046] In this embodiment, it should be noted that the magnetic gear 600 can realize bidirectional variable speed flexible transmission. In addition, by designing the number of pole pairs of the three rotating parts of the magnetic gear 600, the optimal efficiency of the unit can be matched simultaneously under pumping and power generation conditions.

[0047] Compared to the coaxial connection structure of traditional units, the three rotatable parts of the magnetic gear 600 interact through the air gap magnetic field, achieving a flexible connection between the water pump turbine 400 and the generator motor 700. During the unit transition process, the imbalance of torque at both ends of the shaft system will cause a change in the angle between the magnetic field components. The resulting change in the energy of the air gap magnetic field acts as a buffer against the unbalanced torque, effectively reducing its damage to the shaft system.

[0048] According to the relevant theory of magnetic field modulation, if the subscript h represents the inner rotor, the subscript l represents the outer rotor, and the subscript m represents the modulation ring, then under the power generation condition, i.e., when the outer rotor 620 is locked and the inner rotor 610 and the modulation ring 630 are rotating, the rotational angular velocity of the two rotors and the number of pole pairs have the following relationship:

[0049] ;

[0050] Under pumping conditions, i.e., when the modulation ring 630 is locked and the inner rotor 610 and outer rotor 620 are rotating, their rotational angular velocities and the number of pole pairs have the following relationship:

[0051] ;

[0052] As can be seen from the above two equations, under the conditions of pumping and power generation, the water pump turbine 400 rotates in opposite directions, but the rotation direction of the generator motor 700 remains unchanged. This allows the support structure of the generator motor 700 to be changed from the traditional central support to an eccentric support structure that is more economical and has a stronger support capacity, thereby optimizing the support structure of the generator motor 700.

[0053] Due to the law of conservation of energy, the ratio of torques in each component should be equal to the reciprocal of the ratio of angular velocities. Therefore, the generator-motor 700 can be transformed from a traditional low-speed, high-torque hydro-generator into a high-speed, low-torque steam turbine generator. Calculations show that for a 100-megawatt full-power variable-speed pumped-storage unit, the addition of the magnetic gear 600 significantly reduces the weight of the generator-motor 700 and the total weight of the unit, greatly improving the flexibility of unit planning and construction, and facilitating the future development of distributed pumped-storage systems.

[0054] The optimal speed of the pump-turbine 400 in pumping mode is about 18% higher than that in power generation mode, while the highest efficiency point of the full-power converter 800 remains unchanged. Therefore, traditional units cannot achieve simultaneous matching of the optimal efficiency of the turbine and motor under both modes. However, as shown in the above two equations, the transmission ratio of the magnetic gear 600 can be changed by adjusting the number of pole pairs in each part during pumping and power generation. Therefore, by designing a specific number of pole pairs, it is possible to achieve a speed of approximately 18% higher for the pump-turbine 400 in pumping mode than in power generation mode, while keeping the generator motor 700 speed constant at its rated speed. This allows for simultaneous matching of the highest efficiency points in both pumping and power generation modes, improving the overall efficiency of the unit.

[0055] like Figure 3 As shown, taking the locking of the modulation ring 630 and the rotation of the inner rotor 610 and outer rotor 620 as an example, the torque amplitude of the inner rotor 610 and outer rotor 620 is proportional to the sine of the magnetic field angle, and their rotation directions are opposite. Furthermore, the ratio of their amplitudes is equal to the ratio of the number of pole pairs of the inner and outer rotors. Therefore, during the transition process, the unbalanced torque at both ends of the shaft system will cause a change in the magnetic field angle between the inner and outer rotors. The resulting change in the air gap magnetic field energy will absorb the influence of the unbalanced torque on the shaft system, thereby protecting the shaft system during the transition process and preventing low-frequency oscillations of the unit caused by shaft damage.

[0056] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A topology for a full-power variable-speed pumped-storage unit based on a flexible transmission structure, characterized in that, It includes an upper reservoir (100), a water diversion system (200), a water pump turbine (400), a lower reservoir (500), a magnetic gear (600), a generator motor (700), and a full-power converter (800). The water diversion system (200) is connected at one end to the upper reservoir (100) and at the other end to the lower reservoir (500). The water diversion system (200) is used to provide a passage for water flow during unit operation. The water pump turbine (400) is connected to the water intake system (200), and the water pump turbine (400) is connected to the generator motor (700) through the magnetic gear (600). The water pump turbine (400) is used to realize the mutual conversion between the gravitational potential energy of the water flow and the kinetic energy of the rotor. The generator motor (700) is connected to the full-power converter (800) via wires, and the generator motor (700) is used to realize the mutual conversion between rotor kinetic energy and electrical energy; The magnetic gear (600) is provided with an inner rotor (610), an outer rotor (620) and a modulation ring (630). The inner rotor (610) is connected to a generator motor (700), and the outer rotor (620) and the modulation ring (630) are both connected to a water pump turbine (400). The magnetic gear (600) has two operating modes: power generation and pumping, realizing bidirectional variable speed flexible transmission. The operating process of the two modes is as follows: When in power generation operation, the outer rotor (620) is locked, and the inner rotor (610) and modulation ring (630) rotate. When in pumping operation, the modulation ring (630) is locked, and the inner rotor (610) and outer rotor (620) rotate.

2. The topology of a full-power variable-speed pumped-storage unit based on a flexible transmission structure as described in claim 1, characterized in that: The water intake system (200) includes a water intake pipe on which a pressure regulating well (300) and a ball valve are installed.

3. The topology of a full-power variable-speed pumped-storage unit based on a flexible transmission structure as described in claim 1, characterized in that: The full-power converter (800) is connected to an external power grid.

4. The topology of a full-power variable-speed pumped-storage unit based on a flexible transmission structure as described in claim 1, characterized in that: The full-power converter (800) is a converter with a back-to-back connection.

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