A motor soft start device based on a micro-grid system

Abstract

The application discloses a motor soft starting device based on a micro-grid system, which is composed of a tapping switch 3, a motor bus 4, a self-coupled transformer 5, a voltage regulating switch 6, a voltage regulating wire package 7, a capacitor bank 8 and a compensation switch 9. The motor soft starting device has simple structure, reliable performance, small reactive power obtained from the power grid during motor starting, smooth voltage switching during starting, stable starting current, small impact on the power grid, no influence on the quality of the power grid and can be widely applied to the starting control of large motors in various micro-grids and weak areas of the power grid structure.

Description

Technical Field

[0001] This application belongs to the field of motor control and relates to a motor soft starter, specifically a motor soft starter based on a microgrid system. Background Technology

[0002] Microgrids use renewable energy to generate electricity, which can reduce dependence on traditional energy sources, reduce energy consumption and carbon emissions, and have obvious environmental protection and energy-saving effects. However, the diversity and complexity of their power sources and loads lead to the deterioration of the reliability, stability and power quality of microgrids. In particular, the starting of large motors in microgrid systems poses a serious challenge to the stability of microgrids and may even cause the microgrid system to fail.

[0003] Currently, the equipment commonly used for starting large motors includes water resistors, switching transformers, autotransformers, and electronic step-down transformers. The starting current of these starting devices is generally 3-4 times the rated current. In particular, the large amount of reactive power required when starting a motor severely impacts the power quality of the microgrid system. Therefore, this technology is not suitable for microgrid systems. Summary of the Invention

[0004] To address the aforementioned issues, this application discloses a motor soft starter based on a microgrid system, comprising a tap changer, a motor bus, an autotransformer, a voltage regulator switch, a voltage regulator coil, a capacitor bank, and a compensation switch. The tap changer has two input terminals, respectively connected to the 85% and 60% taps on the secondary side of the autotransformer. The output terminal of the tap changer is connected to the motor bus. The neutral point tap of the autotransformer is connected to the voltage regulator coil via the voltage regulator switch. The primary side of the autotransformer is connected to the system power supply via a start switch. The motor bus is also connected to the system power supply via a running switch, and to the capacitor bank via the compensation switch, ultimately connecting to the motor.

[0005] The capacitor bank has three or more groups, each connected to the motor bus via a compensation switch, and each group of capacitors has a different capacity.

[0006] This application features a simple structure, reliable performance, low reactive power extraction from the grid during motor startup, smooth voltage switching during startup, stable starting current, minimal impact on the grid, and no impact on grid quality. It can be widely applied to the starting control of large motors in various microgrids and areas with weak grid structures. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of the single-line principle of the present invention;

[0008] In the diagram: 1. Start switch; 2. Run switch; 3. Tap switch; 4. Motor busbar; 5. Autotransformer; 6. Voltage regulating switch; 7. Voltage regulating coil; 8. Capacitor bank; 9. Compensation switch; 10. Motor. Detailed Implementation

[0009] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0010] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and 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, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0011] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0012] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0013] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0014] It should also be further understood that the term “and / or” as used in this specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0015] The accompanying drawings show various structural schematic diagrams according to embodiments of the present invention. These drawings are not to scale, and some details have been enlarged and may have been omitted for clarity. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0016] Referring to the accompanying drawings, this application discloses a motor soft starter based on a microgrid system, comprising a tap changer 3, a motor bus 4, an autotransformer 5, a voltage regulating switch 6, a voltage regulating coil 7, a capacitor bank 8, and a compensation switch 9. The tap changer 3 has two sets of input terminals, respectively connected to the 85% and 60% taps on the secondary side of the autotransformer 5. The output terminal of the tap changer 3 is connected to the motor bus 4. The neutral point tap of the autotransformer 5 is short-circuited after being connected to the voltage regulating coil 7 via the voltage regulating switch 6. The primary side of the autotransformer 5 is connected to the system power supply via a starter switch 1. The motor bus 4 is also connected to the system power supply via a running switch 2, and connected to the capacitor bank 8 via the compensation switch 9, ultimately connecting to the motor 10.

[0017] The voltage regulating coil 7 is formed by a continuous winding with three or more taps drawn from the middle, and the impedance between each tap is equal. The connection between the taps and the neutral point tap of the autotransformer 5 is changed sequentially by the voltage regulating switch 6 to adjust the output voltage of the secondary side of the autotransformer 5.

[0018] The capacitor bank 8 has three or more groups, each corresponding to a compensation switch 9. Each capacitor bank 8 has a different capacity and is connected to the motor bus 4 via the compensation switch 9. The capacitor bank is switched on or off as needed according to the reactive power required when the motor 10 starts.

[0019] The operating switch 2 is interlocked with the starting switch 1 and the tap changer 3. That is, when the operating switch 2 is closed, the starting switch 1 and the tap changer 3 must be completely disconnected; when the starting switch 1 and the tap changer 3 are closed, the operating switch 2 is disconnected.

[0020] Before motor 10 starts, running switch 2 is in the open position, voltage regulating switch 6 closes the adjusting contact to the low position of voltage regulating coil 7, and all switches in the device are in the open position. When the motor starts, start switch 1 is closed, tap changer 3 closes the 60% tap of autotransformer 5, voltage regulating switch 6 closes step by step from the low position, and compensation switch 9 is closed according to the calculated starting reactive power of motor 10 to engage the capacitor bank 8 of the corresponding capacity. Motor 10 starts from low speed. As the speed of motor 10 increases, voltage regulating switch 6 increases the secondary voltage of autotransformer 5 through voltage regulating coil 7. When voltage regulating switch 6 reaches the highest position and motor 10 runs smoothly, tap changer 3 is opened. When the 60% tap of the autotransformer 5 is closed, the voltage regulating switch 6 returns to the low position, the tap changer 3 closes the 85% tap of the autotransformer 5, and the voltage regulating switch 6 starts closing again from the low position step by step to adjust the secondary output voltage of the autotransformer 5. The speed of the motor 10 increases further as the voltage regulating switch 6 moves up. As the speed of the motor 10 increases, the reactive power demand decreases, and the corresponding compensation switch 9 is gradually disconnected according to the capacity of the capacitor bank 8 to disconnect the corresponding capacitor bank 8. After the motor 10 runs smoothly again, the start switch 1 and tap changer 3 are disconnected, the voltage regulating switch 6 returns to the lowest position, and the running switch 2 is closed to complete the starting process of the motor 10.

Claims

1. A motor soft starter based on a microgrid system, comprising a tap changer (3), a motor bus (4), an autotransformer (5), a voltage regulating switch (6), a voltage regulating coil (7), a capacitor bank (8), and a compensation switch (9), characterized in that: The tap changer (3) has two sets of input terminals, which are connected to the 85% tap and 60% tap on the secondary side of the autotransformer (5) respectively. The output terminal of the tap changer (3) is connected to the motor bus (4). The neutral point tap of the autotransformer (5) is short-circuited after being connected to the voltage regulating coil (7) via the voltage regulating switch (6). The primary side of the autotransformer (5) is connected to the system power supply via the start switch (1). The motor bus (4) is also connected to the system power supply via the running switch (2), and connected to the capacitor bank (8) via the compensation switch (9), and finally connected to the motor (10).

2. The motor soft starter based on a microgrid system according to claim 1, characterized in that: The voltage regulating coil (7) is formed by a continuous winding with more than 3 taps drawn from the middle, and the impedance between each tap is equal. The connection between the taps and the neutral point tap of the autotransformer (5) is changed sequentially by the voltage regulating switch (6) to adjust the output voltage of the secondary side of the autotransformer (5).

3. The motor soft starter based on a microgrid system according to claim 1, characterized in that: The capacitor bank (8) has three or more groups, each group corresponding to a compensation switch (9). Each group of capacitor banks (8) has a different capacity and is connected to the motor bus (4) via the compensation switch (9).

4. The motor soft starter based on a microgrid system according to claim 1, characterized in that: The operation switch (2) is interlocked with the start switch (1) and the tap switch (3).

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