A cascaded variable-speed micro-pumped storage generator motor

Abstract

The technical solution adopted by the present invention is as follows: A cascaded variable-speed micro-pumped storage generator motor includes a stator structure and a rotor structure that cooperate with each other; the stator structure is arranged outside the rotor structure; the stator structure includes a stator body, and two sets of stacked stator windings are embedded in the stator body. The number of poles of the two sets of stator windings is different and they cooperate with the rotor structure; the two sets of stator windings are respectively a power winding and a control winding, and the phase sequences of the power winding and the control winding are reversely connected; the rotor structure includes a first rotor and a second rotor arranged coaxially; both the first rotor and the second rotor are cage-type rotors; the opposite ends of the first rotor and the second rotor are reversely connected through an intermediate bar; the intermediate bar serves as the rotor winding. The present invention has the characteristics of decoupling control of active and reactive power of the output power and dynamically matching the power demand of the power grid, and can achieve large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and particularly relates to a cascaded variable-speed micro-pumped storage generator motor. Background Art

[0002] In the field of variable-speed pumped storage, various generator motors such as doubly-fed type and permanent magnet type have certain application potentials. However, they generally have problems such as high price, complex structure, cumbersome manufacturing process, and easy wear of important components. For example, if a doubly-fed motor model is adopted for a variable-speed pumped storage unit, the rotating part and the stator part have the same iron core and winding. For the rotating iron core and winding at high linear speeds, the dynamic stability design of such a structure is a major problem. The durability of the key components of the rotating part needs to be urgently overcome and broken through.

[0003] For a micro-pumped storage system, there is an urgent need to find a model that can not only achieve variable-speed operation but also be mass-produced and applied. At the same time, it is also required to have a simple and reliable structure and low cost. The cascaded motor is a special form of motor, which has advantages such as low price and firm structure and is suitable for mass production. Therefore, there is a possibility of application in the field of micro variable-speed pumped storage. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the above background art, and provide a cascaded variable-speed micro-pumped storage generator motor, which can not only enable the pumped storage unit to generate electricity with variable speed, constant frequency, and constant voltage, and drive the water pump to pump water with variable speed, but also has the characteristics of decoupling control of active and reactive power of the output power and dynamically matching the power demand of the power grid. Most importantly, it can achieve large-scale production.

[0005] The technical solution adopted by the present invention is: a cascaded variable-speed micro-pumped storage generator motor, including a stator structure and a rotor structure that cooperate with each other; the stator structure is arranged outside the rotor structure; the stator structure includes a stator body, and two sets of stacked stator windings are embedded in the stator body. The pole numbers of the two sets of stator windings are different and cooperate with the rotor structure; the two sets of stator windings are respectively a power winding and a control winding, and the phase sequences of the power winding and the control winding are reversely connected; the rotor structure includes a first rotor and a second rotor arranged coaxially; both the first rotor and the second rotor are cage-type rotors; the opposite ends of the first rotor and the second rotor are reversely connected through an intermediate bar; the intermediate bar serves as the rotor winding.

[0006] In the above technical solution, the conductor at the angular position α in the first rotor is connected to the conductor at the angular position 2π - α in the second rotor through the intermediate bar; α is a unit angle.

[0007] In the above technical solution, the ith circuit of the first rotor is connected to the n - i circuits of the second rotor; where i represents the circuit number, and n represents the total number of circuits; the number of circuits of the first rotor and the second rotor is the same.

[0008] In the above technical solution, the opposite end rings of the first rotor and the second rotor are fixedly connected through end conductors; the end conductors are evenly distributed along the circumferences of the end rings of the first rotor and the second rotor; the conductor at the angular position α in the first rotor is connected to the conductor at the angular position 2π - α in the second rotor through the end conductor; α is the unit angle.

[0009] In the above technical solution, when the number of pole pairs of the power winding and the control winding are p1 and p2 respectively, the number of rotor conductors matched with the control winding and the power winding satisfies p1n2 = kp2n1, where k is an integer, n1 is the number of turns of the winding of the rotor conductor matched with the power winding; n2 is the number of turns of the winding of the rotor conductor matched with the control winding.

[0010] In the above technical solution, the power winding of the stator is electrically connected to the three - phase power frequency grid, and the control winding of the stator is electrically connected to the converter to achieve variable - speed operation.

[0011] In the above technical solution, the voltage matrix equation in its rotor speed coordinate model is expressed as:

[0012]

[0013] Among them, U dq represents the voltage matrix in the rotor speed model; I dq represents the current matrix in the rotor speed model; L dq represents the self - inductance matrix in the rotor speed model; Ψ dq represents the magnetic flux linkage matrix in the rotor speed model; C represents the capacitance in the rotor speed model, ω r represents the rotational speed in the rotor speed model, θ r represents the phase in the rotor speed model; R abc is the resistance matrix in the coupled circuit model in the formula, and R dq is the resistance matrix in the rotor speed model.

[0014] In the above technical solution, the electromagnetic torque equation and the torque equation in its rotor speed coordinate model are as follows,

[0015]

[0016]

[0017] Among them, the number of pole pairs of the power winding and the control winding are p1 and p2 respectively; J is the torque inertia of the cascaded variable - speed micro - pumped storage generator - motor, and Rω is the rotor damping coefficient, T em represents the electromagnetic torque T of the motor l is the load torque of the motor, M m1 represents the mutual inductance matrix of the power winding; M’ m2 represents the mutual inductance matrix of the control winding, i s1q represents the q-axis current of the power winding, i s1d represents the d-axis current of the power winding; i' rd represents the d-axis component of the rotor current; i' rq represents the q-axis component of the rotor current; i' s2d represents the d-axis current of the control winding; i’ s2q represents the q-axis current of the control winding.

[0018] The beneficial effects of the present invention are as follows: The present invention discloses a micro pumped-storage unit that can function as both a generator and a motor, with a fast response speed. The pumped-storage unit introduced in the present invention has a cascaded variable-speed motor structure, which is a motor structure where two asynchronous motors share a common shaft. The two asynchronous motors are directly connected through windings, without devices such as easily damaged carbon brushes or slip ring devices in the middle. The mechanical connection of the two motor shafts is equivalent to a special motor that can both operate electrically and generate electricity, and has the potential to be used as a motor-generator in a micro pumped-storage power station. In a micro pumped-storage system, this new type of variable-speed pumped-storage unit has obvious application advantages compared with fixed-speed units and conventional variable-speed units, specifically manifested as: low cost, short manufacturing period, adjustable speed under all working conditions, power dynamic tracking adjustment, etc.

[0019] Furthermore, in the case of the rotor rotating electrically in the present invention, a current with a corresponding frequency is passed through the stator control winding, so that the stator power winding maintains constant-frequency and constant-voltage power generation.

[0020] Furthermore, in the present invention, the stator power winding is connected to a constant-frequency and constant-voltage power supply of a large power grid, and the stator control winding is connected to a current with variable frequency and amplitude, so that the rotor operates at a variable speed to meet the demand for driving a water pump to pump water at variable speed.

[0021] Furthermore, the present invention can achieve active and reactive decoupling control based on the motor structure, and through power electronic power devices with high dynamic response characteristics, the frequency and amplitude of the stator control winding are changed to adapt to different scenario requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the connection of the end part and the bars of the rotor of the present invention;

[0023] Figure 2 is a three-dimensional schematic diagram of the production and manufacturing of the cascaded variable-speed unit of the present invention;

[0024] Figure 3a Schematic diagram a of the principle of the present invention;

[0025] Figure 3b Schematic diagram b of the principle of the present invention;

[0026] Figure 4 Schematic diagram of the flow of the control method of the present invention.

[0027] Wherein, 1 - first rotor, 2 - second rotor, 3 - rotor conductor, 4 - intermediate bar, 5 - end bar, 6 - end ring. Detailed implementation manners

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, which is convenient for clearly understanding the present invention, but they do not constitute a limitation to the present invention.

[0029] As Figure 1 shown, the present invention provides a cascaded variable-speed micro-pumped storage generator motor, including a stator structure and a rotor structure that cooperate with each other; the stator structure is arranged outside the rotor structure; the stator structure includes a stator body, and two sets of stacked stator windings are embedded in the stator body. The number of poles of the two sets of stator windings is different and they cooperate with the rotor structure; the two sets of stator windings are respectively a power winding and a control winding, and the phase sequences of the power winding and the control winding are reversely connected; the rotor structure includes a first rotor 1 and a second rotor 2 arranged coaxially; both the first rotor 1 and the second rotor 2 are cage-type rotors; the opposite ends of the first rotor 1 and the second rotor 2 are reversely connected through an intermediate bar 4; the intermediate bar 4 serves as the rotor winding.

[0030] The shape and winding distribution manner of the stator structure are common technical means in the art, so they are not shown in Figure 1 , and those skilled in the art know the structure of the stator structure and its relative relationship with the rotor structure.

[0031] The structure of the cascaded variable-speed motor adopted by the present invention is a motor structure in which two asynchronous motors share a common shaft connection. The two asynchronous motors are directly connected through windings, and there are no easily damaged devices such as carbon brushes or slip ring devices in the middle. The mechanical connection of the two motor shafts is equivalent to a special motor that can both be electric and generate electricity, and has the potential to be used as a generator motor for a micro-pumped storage power station.

[0032] In terms of working mode, the cascaded variable-speed micro-pumped storage generator motor can be regarded as the structure of a complete motor. Its motor body is composed of a specially constructed rotor and stator, and two sets of windings are embedded in the stator slots. The pole numbers of these two sets of windings are different and cooperate with the rotor. These two sets of windings are respectively called the power winding group and the control winding group. At the same time, the cascaded variable-speed micro-pumped storage generator motor can also be regarded as a cascaded system composed of two asynchronous motors with different pole numbers p1 and p2. That is to say, the rotor shafts of the two motors share a bearing, and the two sets of rotor windings are connected in reverse phase sequence. The winding of one motor, that is, the power winding with a pole logarithm of p1, is connected to the three-phase power frequency power grid, and the stator winding of the other motor, that is, the control winding with a pole logarithm of p2, is connected to the converter to achieve variable-speed operation.

[0033] From the perspective of winding theory, when the stator power winding and control are respectively supplied with three-phase symmetrical voltages, there are two fundamental magnetic fields existing simultaneously in the variable-speed motor. This requires the rotor winding to couple the two fundamental magnetic fields with different pole numbers p1 and p2 at the same time. These two magnetic fields are respectively generated by the two sets of windings on the stator. It is very convenient to arrange two sets of windings on the rotor. According to the principle of magnetic potential superposition, as Figure 3a shown, A1, B1, C1 respectively represent the rotor power three-phase windings for coupling the stator power three-phase windings, and A2, B2, C2 respectively represent the rotor control three-phase windings for coupling the stator control three-phase windings. In order to make the output torque have the same direction, these two sets of rotor windings need to be connected in reverse phase sequence, as Figure 3b shown.

[0034] The only disadvantage of the cascaded variable-speed motor is the wound rotor. The disadvantages of the wound rotor are as follows: It is more expensive than the cage rotor and the structure is less reliable. The mechanical strength of the cable in the wound rotor is much smaller than that of the solid bar in the cage rotor. Insulation breakdown is a serious problem for the wound rotor. Because the wound rotor circuit usually has a very high number of turns and its induced voltage is high. In addition, due to the action of the rotor centrifugal force, the movement of the wire and the insulator film is inevitable. The slot filling factor of the wound rotor is lower than that of the cage rotor. Therefore, the energy of the wound rotor is higher.

[0035] Therefore, the wound-rotor cascaded variable-speed micro-pumped storage generator motor cannot be widely applied yet. The stator of the cage-rotor cascaded variable-speed motor proposed by the present invention is the same as that of the wound-rotor cascaded variable-speed motor, but the rotor structure has been innovated. This structure has two cage rotors and is connected in series according to needs. This structure has the following characteristics: First, the two rotors are installed on the same shaft; Second, the end structures of the two cage rotors are completely retained to improve the mechanical strength; Third, the phase sequence of the power winding and the control winding is reversely connected.

[0036] In this way, a reverse phase sequence interconnection between the two rotor circuits is obtained. The interconnection between the rotor conductors 3 is as shown by the dashed line in Figure 1 . For simplicity in manufacturing, the rotor conductors 3 and the end rings are implemented with copper bars. The butting scheme of the rotor conductors 3 is as shown in Figure 2 . In this rotor circuit, the conductor at the angular position α in one motor is connected to the conductor at the angular position 2π - α in the other motor. The i-th loop of the first rotor 1 is connected to the n - i-th loop of the second rotor 2. The connection between the rotor conductors 3 can be achieved by bolt connection.

[0037] Although for simplicity, similar two-pole motors are considered in the power and control motors, the proposed structure can be extended to other pole number combinations. The rule that the new cage-type structure should follow is that the conductors with opposite phase angles (in electrical radians) must be connected together. To meet this condition, an appropriate number of rotor bars must be selected in the motor. When the pole numbers of the power winding and the control winding are p1 and p2 respectively, the number of rotor conductors 3 of the control winding and the power winding satisfies p1n2 = kp2n1, where k is an integer, and n1 and n2 are the number of turns of the two sets of windings.

[0038] In addition, in a high-power pumped-storage power generation motor, the cross-section of the rotor interconnection increases. This may bring some difficulties to the connection of the rotor conductors 3. In this case, the number of conductors can be increased with a smaller cross-section, thereby increasing the relatively weak interconnection part, that is, the connection part between the conductor and the end. The opposite end rings of the first rotor and the second rotor are fixedly connected through end bars; the end bars are evenly distributed circumferentially along the ends of the first rotor and the second rotor. The conductor at the angular position α in the first rotor is connected to the conductor at the angular position 2π - α in the second rotor through the end bar; α is a unit angle.

[0039] As is well known, new motors are inseparable from control, and the two complement each other and are indispensable. To obtain the control method of the proposed motor type, a complete motor mathematical model needs to be established for the cascaded variable-speed micro-pumped-storage power generation motor. Based on the matrix transformation of the coupled circuit model, the present invention gives a rotor speed model of the cascaded variable-speed micro-pumped-storage power generation motor.

[0040] The voltage matrix equation in the rotor speed coordinate model of the cascaded variable-speed micro-pumped-storage power generation motor can be expressed as

[0041]

[0042] where U dq represents the voltage matrix under the rotor speed model; I dq represents the current matrix under the rotor speed model; L dqrepresents the self-inductance matrix under the rotor speed model; Ψ dq represents the flux linkage matrix under the rotor speed model; C represents the capacitance under the rotor speed model, ω r represents the rotational speed under the rotor speed model, θ r represents the phase under the rotor speed model; R abc is the resistance matrix in the coupled circuit model in the formula, R dq is the resistance matrix under the rotor speed model.

[0043] For simplicity, assume the matrix K dq is

[0044]

[0045] Similarly, the electromagnetic torque equation and torque equation can also be derived as follows,

[0046]

[0047]

[0048] wherein, the number of pole pairs of the power winding and the control winding are p1 and p2 respectively; J is the torque inertia of the cascaded variable-speed micro-pumped storage generator motor, R ω is the rotor damping coefficient, T em represents the electromagnetic torque T of the motor l is the load torque of the motor, M m1 represents the mutual inductance matrix of the power winding; M’ m2 represents the mutual inductance matrix of the control winding, i s1q represents the q-axis current of the power winding, i s1d represents the d-axis current of the power winding; i' rd represents the d-axis component of the rotor current; i' rq represents the q-axis component of the rotor current; i' s2d represents the d-axis current of the control winding; i’ s2q represents the q-axis current of the control winding.

[0049] In summary, through appropriate matrix transformation, the rotor speed model of the cascaded variable-speed micro-pumped storage generator motor can be obtained, and each mutual inductance matrix in this model is a function independent of the rotor position angle, which provides convenience for building the control block diagram of the cascaded variable-speed micro-pumped storage generator motor.

[0050] The control logic of the present invention is as Figure 4As shown, where the subscripts d and q respectively represent the variable parameters related to the decoupled d-axis and q-axis; the subscript abc represents the variable parameters in the abc coordinate system; the subscript r represents the variable parameters related to the rotor winding; the subscript s1 represents the variable parameters related to the stator power winding; the subscript s2 represents the variable parameters related to the stator control winding; θ m represents the rotor mechanical angle, and θ m represents the rotor electrical angle; v represents voltage, i represents current, the superscript * represents the reference value, and the superscript - represents the vector.

[0051] Contents not described in detail in this specification belong to the prior art well-known to those of ordinary skill in the art.

Claims

1. A cascaded variable-speed micro-pumped storage generator motor, characterized in that: It includes a stator structure and a rotor structure that cooperate with each other; the stator structure is arranged outside the rotor structure; the stator structure includes a stator body, and two sets of stacked stator windings are embedded in the stator body. The number of poles of the two sets of stator windings is different and they cooperate with the rotor structure; the two sets of stator windings are respectively a power winding and a control winding, and the phase sequences of the power winding and the control winding are reversely connected; the rotor structure includes a first rotor and a second rotor arranged coaxially; both the first rotor and the second rotor are cage-type rotors; the opposite ends of the first rotor and the second rotor are reversely connected through an intermediate bar; the intermediate bar serves as a rotor winding; The conductor at the angular position α in the first rotor is connected to the conductor at the angular position 2π - α in the second rotor through the intermediate bar; α is a unit angle; The i-th loop of the first rotor is connected to the (n - i)-th loop of the second rotor; where i represents the loop number and n represents the total number of loops; the number of loops of the first rotor and the second rotor is the same; The opposite end rings of the first rotor and the second rotor are fixedly connected through end bars; the end bars are evenly distributed circumferentially along the end rings of the first rotor and the second rotor; the conductor at the angular position α in the first rotor is connected to the conductor at the angular position 2π - α in the second rotor through the end bar; α is a unit angle; When the number of pole pairs of the power winding and the control winding are p1 and p2 respectively, the number of rotor conductors cooperating with the control winding and the power winding satisfies p1n2 = kp2n1, where k is an integer, n1 is the number of turns of the winding of the rotor conductor cooperating with the power winding; n2 is the number of turns of the winding of the rotor conductor cooperating with the control winding; The power winding of the stator is electrically connected to a three-phase power frequency grid, and the control winding of the stator is electrically connected to a converter to achieve variable-speed operation; For the cascaded variable-speed micro-pumped storage generator motor described above, the voltage matrix equation in its rotor speed coordinate model is expressed as: Among them, U dq represents the voltage matrix under the rotor speed model; I dq represents the current matrix under the rotor speed model; L dq represents the self-inductance matrix under the rotor speed model; Ψ dq represents the magnetic flux linkage matrix under the rotor speed model; C represents the capacitance under the rotor speed model, ω r represents the rotational speed under the rotor speed model, θ r represents the phase under the rotor speed model; R abc is the resistance matrix in the coupled circuit model in the formula, R dq is the resistance matrix under the rotor speed model; For the cascaded variable-speed micro-pumped storage generator motor described above, the electromagnetic torque equation and torque equation in its rotor speed coordinate model are as follows, Among them, the pole pairs of the power winding and the control winding are p1 and p2 respectively; J is the torque inertia of the cascaded variable-speed micro-pumped storage generator-motor, R ω is the rotor damping coefficient, T em represents the electromagnetic torque T of the motor l is the load torque of the motor, M m1 represents the mutual inductance matrix of the power winding; M’ m2 represents the mutual inductance matrix of the control winding, i s1q represents the q-axis current of the power winding, i s1d represents the d-axis current of the power winding; i' rd represents the d-axis component of the rotor current; i' rq represents the q-axis component of the rotor current; i' s2d represents the d-axis current of the control winding; i’ s2q represents the q-axis current of the control winding.

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