A brake device suitable for a permanent magnet flywheel energy storage motor

Abstract

The application provides a brake device suitable for a permanent magnet flywheel energy storage motor, comprising three-phase resistors and three three-phase contactors; the three-phase resistors comprise three single-phase resistors with the same resistance, each single-phase resistor comprising two resistance sheets with the same resistance; each single-phase resistor has two connecting terminals on the first resistance sheet, which are a1, a2, b1, b2, c1 and c2 respectively, and two connecting terminals on the second resistance sheet, which are a2, a3, b2, b3, c2 and c3 respectively; the brake device has three connecting terminals on the external output end, which are a4, b4 and c4 respectively; each three-phase contactor is divided into three paths, six terminals of the first three-phase contactor are connected with a2-a4, b2-b4 and c2-c4 respectively, six terminals of the second three-phase contactor are connected with a3-a4, b3-b4 and c3-c4 respectively, and six terminals of the third three-phase contactor are connected with a3-b3, b3-c3 and c3-c1 respectively; and the application can solve the technical problem that the brake resistor in the prior art is not suitable for high-speed flywheels.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a braking device suitable for permanent magnet flywheel energy storage motors. Background Technology

[0002] A permanent magnet flywheel energy storage motor is a device that uses a large-inertia rotor to convert kinetic energy into electrical energy. In actual operation, it can function as a motor to drive the flywheel rotor to accelerate and store electrical energy, or as a generator to convert the rotor's kinetic energy into electrical energy for output. Based on these characteristics, flywheel energy storage motors are widely used in fields such as subway braking energy recovery and UPS uninterruptible power supplies.

[0003] With technological advancements and market demands, flywheel speeds are continuously increasing. This leads to the problem of higher safety requirements for high-speed flywheels. Serious malfunctions such as flywheel rotor instability can cause significant property damage and personal injury. Therefore, braking resistors and circuit breakers are necessary to handle unexpected situations during flywheel operation. This solution addresses the issue by using a braking resistor to dissipate flywheel energy. However, as the flywheel speed decreases, the back electromotive force decreases, consequently reducing the resistor's discharge power and significantly increasing the overall braking time. Summary of the Invention

[0004] This invention provides a braking device suitable for permanent magnet flywheel energy storage motors, which can solve the technical problem that braking resistors are not suitable for high-speed flywheels in the prior art.

[0005] The present invention provides a braking device suitable for a permanent magnet flywheel energy storage motor, the braking device comprising a three-phase resistor and three three-phase contactors;

[0006] The three-phase resistor includes three single-phase resistors with the same resistance value. Each single-phase resistor includes two resistor pieces with the same resistance value. The first ends of the first resistor pieces of the three single-phase resistors are connected to ground respectively, and the second ends of the first resistor pieces of the three single-phase resistors are connected to the first ends of their respective second resistor pieces.

[0007] In the first three-phase contactor, the first end of each phase contactor is connected to the second end of the first resistor in the three single-phase resistors. The second end of each phase contactor serves as the three-phase output terminal of the braking device, which is used to connect to the three phases of the flywheel energy storage motor respectively.

[0008] In the second three-phase contactor, the first terminal of each phase contactor is connected to the second terminal of the second resistor in the three single-phase resistors, and the second terminal of each phase contactor is connected to the second terminal of each phase contactor in the first three-phase contactor.

[0009] The first terminal of the first phase contactor in the third three-phase contactor is connected to the first terminal of the first phase contactor in the second three-phase contactor. The second terminal of the first phase contactor in the third three-phase contactor is connected to the first terminal of the second phase contactor in the second three-phase contactor and the first terminal of the second phase contactor in the third three-phase contactor. The first terminal of the third phase contactor in the third three-phase contactor is grounded. The second terminal of the third phase contactor in the third three-phase contactor is connected to the second terminal of the second phase contactor in the third three-phase contactor and the first terminal of the third phase contactor in the second three-phase contactor.

[0010] During braking, when the speed of the flywheel energy storage motor is greater than the preset speed, the first and third three-phase contactors are both closed, and the second three-phase contactor is open; when the speed of the flywheel energy storage motor is less than or equal to the preset speed, the first and third three-phase contactors are both open, and the second three-phase contactor is closed.

[0011] Preferably, the preset speed is 1000 rpm.

[0012] Preferably, the relationship between the speed of the flywheel energy storage motor and the discharge time is obtained by the following formula:

[0013]

[0014] a = 2πKE, b = 2π 2 J,

[0015] In the formula, n is the rotational speed of the flywheel energy storage motor, E0 is the initial energy of the flywheel energy storage motor, R is the resistance value of the flywheel braking resistor, t is the discharge time, a and b are constants, KE is the back EMF constant, and J is the moment of inertia.

[0016] Specifically, the value of the flywheel braking resistor when the speed of the flywheel energy storage motor is greater than the preset speed is 4 times the value of the flywheel braking resistor when the speed of the flywheel energy storage motor is less than or equal to the preset speed.

[0017] By applying the technical solution of this invention, three three-phase contactors are set up, and the conduction state of the three three-phase contactors is controlled according to the speed of the flywheel energy storage motor. This allows the three-phase resistors to change their resistance values ​​according to the real-time speed, accelerating the discharge of the flywheel energy storage motor, significantly reducing the motor discharge time, and improving braking efficiency. This invention can complete the braking discharge of the energy storage motor, reducing the overall motor discharge time by more than 70%, greatly accelerating the braking process, improving system safety, and enabling the flywheel to stop safely. Attached Figure Description

[0018] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0019] Figure 1 A schematic diagram of a braking device for a permanent magnet flywheel energy storage motor according to an embodiment of the present invention is shown;

[0020] Figure 2 A graph showing the relationship between the rotational speed of the flywheel energy storage motor and the discharge time during braking without the braking device of the present invention is shown.

[0021] Figure 3 A graph showing the relationship between the rotational speed of the flywheel energy storage motor and the discharge time during the braking process when using the braking device of the present invention is shown. Detailed Implementation

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] like Figure 1 As shown, the present invention provides a braking device suitable for a permanent magnet flywheel energy storage motor, the braking device comprising a three-phase resistor and three three-phase contactors;

[0026] The three-phase resistor includes three single-phase resistors with the same resistance value. Each single-phase resistor includes two resistor pieces with the same resistance value. The first ends of the first resistor pieces of the three single-phase resistors are connected to ground respectively, and the second ends of the first resistor pieces of the three single-phase resistors are connected to the first ends of their respective second resistor pieces.

[0027] First three-phase contactor ( Figure 1 In the three-phase contactor 1), the first end of each phase contactor is connected to the second end of the first resistor in the three single-phase resistors. The second end of each phase contactor in the first three-phase contactor serves as the three-phase output terminal of the braking device, which is used to connect to the three phases of the flywheel energy storage motor respectively.

[0028] Second and third phase contactors ( Figure 1 In the three-phase contactor 2), the first end of each phase contactor is connected to the second end of the second resistor in the three single-phase resistors, and the second end of each phase contactor in the second three-phase contactor is connected to the second end of each phase contactor in the first three-phase contactor.

[0029] Third phase contactor ( Figure 1In the three-phase contactor 3), the first terminal of the first phase contactor is connected to the first terminal of the first phase contactor in the second three-phase contactor, and the second terminal of the first phase contactor in the third three-phase contactor is connected to the first terminal of the second phase contactor in the second three-phase contactor and the first terminal of the second phase contactor in the third three-phase contactor respectively; the first terminal of the third phase contactor in the third three-phase contactor is grounded, and the second terminal of the third phase contactor in the third three-phase contactor is connected to the second terminal of the second phase contactor in the third three-phase contactor and the first terminal of the third phase contactor in the second three-phase contactor respectively;

[0030] During braking, when the speed of the flywheel energy storage motor is greater than the preset speed, the first and third three-phase contactors are both closed, and the second three-phase contactor is open; when the speed of the flywheel energy storage motor is less than or equal to the preset speed, the first and third three-phase contactors are both open, and the second three-phase contactor is closed.

[0031] In this invention, the first resistor piece of each single-phase resistor has two terminals, namely a1, a2, b1, b2, c1, c2, and the second resistor piece of each single-phase resistor has two terminals, namely a2, a3, b2, b3, c2, c3, and the braking device has three terminals at its output end, namely a4, b4, and c4.

[0032] Each three-phase contactor is divided into three paths. The six terminals of the first three-phase contactor are connected to a2-a4, b2-b4, and c2-c4 respectively. The six terminals of the second three-phase contactor are connected to a3-a4, b3-b4, and c3-c4 respectively. The six terminals of the third three-phase contactor are connected to a3-b3, b3-c3, and c3-c1 respectively.

[0033] This invention utilizes three three-phase contactors, controlling their conduction states based on the flywheel energy storage motor's rotational speed. This allows the three-phase resistors to adjust their resistance according to the real-time rotational speed, accelerating the flywheel energy storage motor's discharge, significantly reducing discharge time, and improving braking efficiency. This invention enables complete braking and discharging of the energy storage motor, reducing the overall discharge time by over 70%, greatly accelerating the braking process, enhancing system safety, and ensuring a safe stop for the flywheel.

[0034] In this invention, the rotational speed of the flywheel energy storage motor and the flywheel back electromotive force satisfy the following relationship:

[0035] u=KEω=2πKEn=an

[0036] In the formula, u is the back EMF of the flywheel energy storage motor, ω is the angular velocity of the flywheel energy storage motor, and KE is the back EMF constant, which is usually determined by the parameters of the motor itself. For a fixed motor, KE is a constant, so 2πKE can be simplified to the constant a.

[0037] The relationship between energy E and back electromotive force during flywheel discharge is as follows:

[0038]

[0039] The remaining energy of the flywheel is related to its back electromotive force by the following relationship:

[0040]

[0041] In the formula, E is the energy during the flywheel discharge process, and J is the moment of inertia, which is usually determined by the parameters of the motor itself. For a fixed-type motor, J is a constant, therefore 2π 2 J can be simplified to the constant b.

[0042] Based on the above three formulas, the following relationship can be deduced between the speed of the flywheel energy storage motor and the discharge time:

[0043]

[0044] a = 2πKE, b = 2π 2 J,

[0045] In the formula, n is the rotational speed of the flywheel energy storage motor, E0 is the initial energy of the flywheel energy storage motor, R is the resistance value of the flywheel braking resistor, t is the discharge time, a and b are constants, KE is the back EMF constant, and J is the moment of inertia.

[0046] The above braking resistor formula can be used to select the resistance value of the flywheel braking resistor and the gear shift, providing a basis for selection.

[0047] In this embodiment, the peak flywheel speed is set to 5000 rpm, the corresponding back EMF u is 690V, the corresponding energy E0 is 25kWh, and the braking resistance is 2Ω. The relationship between the flywheel speed and time during braking is as follows: Figure 2 As shown.

[0048] from Figure 2 It can be seen that the entire braking process approximates an exponential function. The braking effect of the braking resistor is good in the initial stage, but as the speed decreases, the overall discharge capacity of the resistor gradually declines, such as... Figure 2 The gray area is difficult to reduce to below the safe speed even after an hour, so a variable resistance resistor is needed to speed up the discharge rate.

[0049] Therefore, during the braking process of this invention, when the flywheel speed drops to 1000 rpm, the resistance value switches to a low-resistance mode, decreasing from 1 ohm to 0.25 ohms. In other words, the flywheel braking resistor value corresponding to a flywheel energy storage motor speed greater than the preset speed is four times the flywheel braking resistor value corresponding to a flywheel energy storage motor speed less than or equal to the preset speed. At this time, the discharge curve is as follows: Figure 3 As shown.

[0050] from Figure 3 It can be seen that the overall discharge speed is greatly accelerated. When the motor speed drops from 5000rpm to 500rpm, 99% of the motor energy has been released. Therefore, 500rpm can be selected as a reference point. The discharge time using a traditional discharge resistor is about 3000 seconds, while the discharge time of the improved variable resistance resistor is only 800 seconds. The entire discharge time is reduced by three-quarters, which greatly improves the system safety.

[0051] In summary, the present invention provides a braking device suitable for a permanent magnet flywheel energy storage motor, which has the following beneficial effects:

[0052] 1. It can perform braking discharge on the energy storage motor, enabling the flywheel to stop safely;

[0053] 2. The braking resistor value can be adjusted by relay control, thereby improving braking efficiency;

[0054] 3. A braking resistor formula is proposed to enable the selection of flywheel braking resistor value and gear shifting, providing a basis for selection.

[0055] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0056] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0057] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0058] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A braking device suitable for use in a permanent magnet flywheel energy storage motor, characterized in that, The braking device includes a three-phase resistor and three three-phase contactors; The three-phase resistor includes three single-phase resistors with the same resistance value. Each single-phase resistor includes two resistor pieces with the same resistance value. The first ends of the first resistor pieces of the three single-phase resistors are connected to ground respectively, and the second ends of the first resistor pieces of the three single-phase resistors are connected to the first ends of their respective second resistor pieces. In the first three-phase contactor, the first end of each phase contactor is connected to the second end of the first resistor in the three single-phase resistors. The second end of each phase contactor serves as the three-phase output terminal of the braking device, which is used to connect to the three phases of the flywheel energy storage motor respectively. In the second three-phase contactor, the first terminal of each phase contactor is connected to the second terminal of the second resistor in the three single-phase resistors, and the second terminal of each phase contactor is connected to the second terminal of each phase contactor in the first three-phase contactor. The first terminal of the first phase contactor in the third three-phase contactor is connected to the first terminal of the first phase contactor in the second three-phase contactor. The second terminal of the first phase contactor in the third three-phase contactor is connected to the first terminal of the second phase contactor in the second three-phase contactor and the first terminal of the second phase contactor in the third three-phase contactor. The first terminal of the third phase contactor in the third three-phase contactor is grounded. The second terminal of the third phase contactor in the third three-phase contactor is connected to the second terminal of the second phase contactor in the third three-phase contactor and the first terminal of the third phase contactor in the second three-phase contactor. During braking, when the speed of the flywheel energy storage motor is greater than the preset speed, the first and third three-phase contactors are both closed, and the second three-phase contactor is open; when the speed of the flywheel energy storage motor is less than or equal to the preset speed, the first and third three-phase contactors are both open, and the second three-phase contactor is closed.

2. The brake device according to claim 1, characterized by The preset speed is 1000 rpm.

3. The brake device according to claims 1 and 2, characterized in that, The relationship between the speed of the flywheel energy storage motor and the discharge time can be obtained through the following formula: a = 2πKE, b = 2π 2 J, In the formula, n is the rotational speed of the flywheel energy storage motor, E0 is the initial energy of the flywheel energy storage motor, R is the resistance value of the flywheel braking resistor, t is the discharge time, a and b are constants, KE is the back EMF constant, and J is the moment of inertia. Specifically, the value of the flywheel braking resistor when the speed of the flywheel energy storage motor is greater than the preset speed is 4 times the value of the flywheel braking resistor when the speed of the flywheel energy storage motor is less than or equal to the preset speed.

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