Low voltage ride through device, peripheral wiring system and working method

Abstract

The invention relates to the technical field of frequency converters, in particular to a low-voltage ride-through device, a peripheral wiring system and a working method, and the device comprises a control unit which comprises a power supply module, a charging module connected with the power supply module, and a receiving module connected with the charging module; the power supply module comprises a frequency converter cabinet alternating-current power supply and an in-plant direct-current power supply, the receiving module comprises a frequency converter control power supply, and by arranging the control unit, when the voltage of a power grid is abnormal, the low-voltage ride-through device can intervene and provide voltage support, so that continuous operation of key equipment such as a coal feeder and an air pre-heater is ensured; and the occurrence of equipment shutdown is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency converters, and in particular to a low voltage ride-through device, a peripheral wiring system and a working method. Background Art

[0002] In modern power systems, boiler systems are important energy conversion equipment, and their stable operation is crucial to the safety and efficiency of the entire power system. Boiler systems usually include key equipment such as coal feeders and air preheaters, and the operation of these equipment depends on the stable power supply of the inverter.

[0003] However, when a fault occurs in the power system, such as a fault outside the proximal zone, the system voltage may drop significantly. This phenomenon is called voltage sag. The magnitude of the voltage sag is usually between 20% and 80%, and the duration may exceed 0.5 seconds. In this case, the traditional frequency converter may not be able to maintain normal operation, causing the coal feeder and air preheater to stop working, seriously affecting the safety and efficiency of the boiler system.

[0004] In the boiler system, each boiler is equipped with two air preheaters, each air preheater is equipped with one set of main and auxiliary motors, and both main and auxiliary motors are equipped with frequency converters. Each boiler is also equipped with four coal feeders, each of which is also equipped with a corresponding frequency converter. These frequency converters can provide stable power under normal circumstances, but when the power system fails, the frequency converter may stop working due to the influence of voltage sag, causing the coal feeder and air preheater to fail to operate normally.

[0005] To solve this problem, it is necessary to carry out low voltage ride-through transformation on the inverters of the coal feeder and air preheater to ensure that the inverters can maintain stable operation and guarantee the safety and efficiency of the boiler system when a power system failure occurs. Therefore, we propose a low voltage ride-through device, a peripheral wiring system and a working method. Summary of the invention

[0006] In view of the above problems, a low voltage ride through device in the present invention is proposed.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: a low voltage ride-through device, comprising a control unit, including a power supply module, a charging module connected to the power supply module, and a receiving module connected to the charging module; and wherein the power supply module respectively includes an inverter cabinet AC power supply and an in-plant DC power supply, and the receiving module includes an inverter control power supply.

[0008] As a preferred solution of the low voltage ride-through device of the present invention, wherein: the AC power supply of the inverter cabinet is connected to a circuit breaker and connected to a transformer, and the output end of the transformer is connected to a circuit breaker and connected to the charging module.

[0009] As a preferred solution of the low voltage ride through device of the present invention, wherein: the in-plant DC power supply is connected to the charging module via a circuit breaker.

[0010] As a preferred solution of the low voltage ride through device of the present invention, the output end of the charging module is connected to the inverter control power supply through two circuit breakers connected in series.

[0011] In view of the above problems, a peripheral wiring system of a low voltage ride through device in the present invention is proposed.

[0012] To solve the above technical problems, the present invention provides the following technical solutions: a peripheral wiring system of a low voltage ride-through device, comprising a low voltage ride-through device, and also comprising: by electrically connecting a DC protection power supply of the low voltage ride-through device to an RTM, the RTM monitors the operating status in real time, and one end of the RTM is electrically connected to an isolation diode to prevent current from flowing in reverse.

[0013] As a preferred solution of the peripheral wiring system of the low voltage ride-through device described in the present invention, the output end of the isolation diode is connected to the DC bus terminal of the inverter to convert DC power into AC power to drive the motor or other load connected to the inverter.

[0014] In view of the above problems, a working method of a low voltage ride through device in the present invention is proposed.

[0015] To solve the above technical problems, the present invention provides the following technical solutions: a working method of a low voltage ride-through device, which includes a peripheral wiring system of the low voltage ride-through device, and also includes detecting whether the power grid is normal; if so, the inverter is powered by the three-phase AC power in the factory, and the low voltage ride-through device is in a hot standby state; if not, the value of the power grid voltage is detected.

[0016] As a preferred solution of the working method of the low voltage ride through device of the present invention, when the grid voltage drops to 0% to 90% or temporarily rises to 110% or 130%, the low voltage ride through device starts working instantly.

[0017] As a preferred scheme of the working method of the low voltage ride-through device described in the present invention, when the grid voltage drops to 0% to 90%, the low voltage ride-through device is started, and the inverter continues to work for 60 seconds; when the grid voltage temporarily rises to 110%, the working state of the inverter is adjusted, and the inverter continues to work for 60 seconds; when the grid voltage temporarily rises to 130%, the working state of the inverter is adjusted, and the inverter continues to work for 0.5 seconds.

[0018] As a preferred solution of the working method of the low voltage ride through device of the present invention, when the grid voltage returns to a normal range, the low voltage ride through device stops working and switches to being powered by the power supply within the factory.

[0019] The beneficial effects of the present invention are as follows: through the low voltage ride-through device, the stability and safety of the boiler system when the grid voltage fluctuates are improved; when the grid voltage drops or rises abnormally, the device can quickly intervene to provide the necessary voltage support for the inverter, ensuring the continuous operation of key equipment such as coal feeders and air preheaters, and avoiding equipment shutdown due to voltage problems; it not only reduces the maintenance costs and potential safety risks caused by grid fluctuations, but also enhances the system's adaptability to unstable grid conditions, ensuring production continuity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0021] Figure 1 It is a schematic diagram of the overall circuit connection structure of the low voltage ride through device in the present invention.

[0022] Figure 2 For the present invention Figure 1 Enlarged schematic diagram of the connection structure of part "A" in the middle.

[0023] Figure 3 For the present invention Figure 1 Enlarged schematic diagram of the connection structure of part "B" in the middle.

[0024] Figure 4 For the present invention Figure 1 Enlarged diagram of the connection structure of part "C" in the middle.

[0025] Figure 5 For the present invention Figure 1 Enlarged schematic diagram of the connection structure of part "D" in the middle.

[0026] Figure 6 This is a peripheral wiring diagram of the low voltage ride through device system in the present invention.

[0027] Figure 7 It is a schematic diagram of the working principle of the low voltage ride through device in the present invention.

[0028] Figure 8 It is a schematic diagram of the working method of the low voltage ride through device in the present invention. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0030] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0032] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0033] Example 1

[0034] Reference Figure 1 to Figure 5 , is the first embodiment of the present invention, which provides a low voltage ride through device, a control unit 100, including a power supply module 101, a charging module 102 connected to the power supply module 101, and a receiving module 103 connected to the charging module 102; and, wherein the power supply module 101 includes an inverter cabinet AC power supply 101a and an in-plant DC power supply 101b, and the receiving module 103 includes an inverter control power supply 103a.

[0035] The power supply module 101 is divided into two parts, namely the inverter cabinet AC power supply 101a and the factory DC power supply 101b. When the grid voltage is normal, the inverter is directly powered by the factory three-phase AC power supply, and the low voltage ride-through device is in hot standby state. When the grid voltage is abnormal, the low voltage ride-through device works instantly.

[0036] Preferably, the AC power supply 101a of the inverter cabinet is connected to the transformer 101a - 1 by being connected to the circuit breaker, and the output end of the transformer 101a - 1 is connected to the charging module 102 by being connected to the circuit breaker.

[0037] Preferably, the in-plant DC power supply 101 b is connected to the charging module 102 via a circuit breaker.

[0038] Preferably, the output end of the charging module 102 is connected to the inverter control power supply 103a through two circuit breakers connected in series.

[0039] A circuit breaker is an electrical safety device that protects circuits from overloads and short circuits by automatically cutting off the current. When an abnormal increase in current is detected, the circuit breaker responds quickly and disconnects the circuit to prevent overheating of wires, damage to equipment, or fire. In addition, circuit breakers are also used to isolate power during maintenance, control the on and off of circuits, and maintain the stability of circuits, thereby ensuring the safe and reliable operation of electrical systems.

[0040] Preferably, among the three boilers, each boiler is equipped with 8 inverters, a total of 24, which are used to control different equipment in the boiler system; among these 24 inverters, 12 are used for coal feeders and the other 12 are used for air preheaters. The coal feeder is responsible for delivering coal into the boiler, while the air preheater is used to preheat the air entering the boiler to improve combustion efficiency; in order to ensure that these inverters can operate stably when the grid voltage fluctuates, 3 sets of low voltage ride-through devices are designed, each set of which corresponds to one boiler; each set of low voltage ride-through devices consists of two cabinets, which These cabinets may contain necessary electrical equipment and control units; these two cabinets are installed in the space between the control cabinets of coal feeder B and coal feeder C, which is conducive to centralized management and maintenance; one side of the cabinet of each low voltage ride-through device is responsible for controlling the two coal feeders (A and B) and the inverters of the main motor and auxiliary motor of the air preheater on the A side; the other side of the cabinet of the device is responsible for controlling the other two coal feeders (C and D) and the inverters of the main motor and auxiliary motor of the air preheater on the B side; through this setting, stable power support can be provided for key equipment in the boiler system when the grid voltage is abnormal.

[0041] In summary, the control unit 100 is used to divide the power supply module 101 into two parts, AC and DC, to ensure that when the grid voltage is normal, the inverter can be directly powered by the three-phase AC power supply in the factory, and at the same time, the low voltage ride-through device is kept in hot standby mode, ready to respond to abnormal grid voltage at any time; when the grid voltage is abnormal, such as voltage sag or surge, the low voltage ride-through device will start quickly to provide necessary voltage support to ensure the stable operation of the inverter, by connecting the AC power supply of the inverter cabinet and the DC power supply in the factory to the circuit breaker, and adding a transformer in the AC power supply path, the transformer helps to stabilize and convert the voltage, and the circuit breaker provides protection to prevent circuit damage; the output end of the charging module is connected to the inverter control power supply through two circuit breakers in series, which adds a layer of safety protection to ensure that the power can be quickly cut off in any case to prevent the fault from expanding; the overall provides a reliable, safe and responsive power management solution that can protect key equipment when the grid fluctuates, reduce downtime, and improve the stability and reliability of the entire system.

[0042] Example 2

[0043] Reference Figure 6 , Figure 7 , which is the second embodiment of the present invention. This embodiment is based on the previous embodiment, but differs in that the DC protection power supply of the low voltage ride-through device is electrically connected to the RTM, and the RTM monitors the operating status in real time. One end of the RTM is electrically connected to the isolation diode to prevent the current from flowing in reverse.

[0044] The DC security power supply is used as an emergency backup power supply, that is, the in-plant DC power supply 101b. It provides necessary DC power to maintain the operation of the inverter when the grid voltage is abnormal.

[0045] When the grid voltage is normal, the inverter is powered by the factory's three-phase AC power supply, while the DC safety power supply is in standby mode; when the grid voltage drops temporarily or is interrupted for a short time, the DC safety power supply quickly intervenes to provide DC power through RTM monitoring and control, and prevents reverse current flow through isolation diodes to ensure that the current flows unidirectionally to the inverter DC bus terminals.

[0046] Preferably, the output end of the isolation diode is connected to a DC bus terminal of the frequency converter to convert DC power into AC power to drive a motor or other load connected to the frequency converter.

[0047] The output end of the isolation diode is connected to the DC bus terminal of the inverter, converting DC power into AC power to drive the motor or other load connected to the inverter. This design ensures that when the grid voltage is abnormal, the inverter can continue to provide power to the motor and maintain the continuity of the production process.

[0048] The working principle of the charging power supply of the low voltage ride-through device is that through DC / DC conversion, the DC power supply is inverted into high-frequency AC through a full-bridge PWM circuit, and then isolated and transformed through a high-frequency isolation transformer, and then becomes a stable DC power through high-frequency rectification and filtering; when a DC power supply (such as a battery) is used for power supply, the low voltage ride-through device can achieve a voltage boost effect and output a stable high-voltage DC power.

[0049] Detailed, working principle of low voltage ride through device charging power supply Figure 6 and Figure 7 As shown, the DC power supply is inverted into high-frequency AC through a full-bridge PWM circuit, isolated and transformed by a high-frequency isolation transformer, and then becomes DC power through high-frequency rectification and filtering (i.e., DC / DC conversion), and finally output through anti-reverse connection protection.

[0050] When a DC power supply (battery) is used for power supply, the DC power provided by the battery pack is directly connected to the DC input terminal of the low voltage ride-through device module; in the DC power supply mode, the input voltage of the DC power supply is usually required to be lower than the output voltage of the low voltage ride-through device, and the low voltage ride-through device is used to achieve the boost effect, and its output is a stable high-voltage DC power; when the AC input voltage of the inverter is normal, the low voltage ride-through device is in standby mode.

[0051] When the AC power experiences a voltage drop or short interruption, the DC bus voltage of the inverter will drop, and the high-voltage DC power output by the low voltage ride-through device will be sent to the DC bus terminal of the inverter to provide voltage support, ensuring that the inverter will not shut down due to AC undervoltage. The low voltage ride-through device module plays a supporting role for the inverter.

[0052] When the AC voltage returns to normal, the low voltage ride-through device automatically exits support and is in standby mode, ready for the next voltage drop or short interruption in the power grid.

[0053] Example 3

[0054] Reference Figures 1 to 8 , which is the third embodiment of the present invention. This embodiment is based on the previous embodiment, and the difference is that it detects whether the power grid is normal; if so, the inverter is powered by the three-phase AC power in the factory, and the low voltage ride-through device is in hot standby state; if not, the value of the power grid voltage is detected.

[0055] Preferably, when the grid voltage drops to 0% to 90% or temporarily rises to 110% or 130%, the low voltage ride-through device starts working instantaneously.

[0056] Preferably, when the grid voltage drops to 0% to 90%, the low voltage ride-through device is started, allowing the inverter to continue working for 60 seconds; when the grid voltage temporarily rises to 110%, the working state of the inverter is adjusted, and the inverter continues to work for 60 seconds; when the grid voltage temporarily rises to 130%, the working state of the inverter is adjusted, and the inverter continues to work for 0.5 seconds.

[0057] Preferably, when the grid voltage returns to a normal range, the low voltage ride-through device stops working and switches to being powered by the in-plant power supply.

[0058] When the grid voltage is normal, the inverter is powered directly by the three-phase AC power in the factory, and the low voltage ride-through device is in hot standby state; when the grid voltage drops, the power bus voltage drops to 0% to 90% or rises to 110% or 130% of the rated voltage, the low voltage ride-through device starts working instantly (<0.2ms) to ensure the normal operation of the inverter. When the voltage drops (0% to 90% of the rated voltage), the inverter can continue to work for 60 seconds, and when the voltage rises temporarily (110% or 130% of the rated voltage), the inverter can continue to work for 60 seconds and 0.5 seconds respectively. When the power bus voltage recovers, the low voltage ride-through device automatically exits the working state and switches to hot standby state, and the inverter automatically switches to power supply by the factory power bus.

[0059] In summary, through this method, the power supply strategy can be intelligently adjusted according to the change of grid voltage, and by providing corresponding values, a clear threshold is set for the abnormal fluctuation of grid voltage, ensuring that when the grid voltage drops to 0% to 90% or temporarily rises to 110% or 130%, the low voltage ride-through device can be quickly started to provide the necessary voltage support for the inverter; this design can cover the common abnormal range of grid voltage, and at the same time provide differentiated processing strategies for different voltage abnormalities, such as providing 60 seconds of continuous power supply when the voltage drops, and providing 60 seconds of power supply when the voltage temporarily rises to 110%, but when the voltage temporarily rises to 130%, only 0.5 seconds of power supply is provided due to possible damage to the equipment. Such a design not only protects the equipment but also ensures the stability of the grid.

[0060] When the grid voltage returns to the normal range, the low voltage ride-through device can automatically exit the working state and switch to the power supply in the factory, realizing the automation and intelligence of the system. This method can significantly improve the reliability and stability of the power system and reduce equipment downtime and production interruption caused by abnormal grid voltage; by accurately controlling the operation time of the inverter, the system can also protect the equipment while minimizing the impact on the production process; through this automated response mechanism, the need for manual intervention is reduced, maintenance costs are reduced, and the efficiency of the entire power system is improved.

[0061] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

[0062] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0063] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0064] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A low voltage ride through device, characterized in that: include, A control unit (100) comprises a power supply module (101), a charging module (102) connected to the power supply module (101), and a receiving module (103) connected to the charging module (102); and The power supply module (101) includes a frequency converter cabinet AC power supply (101a) and an in-plant DC power supply (101b), and the receiving module (103) includes a frequency converter control power supply (103a).

2. The low voltage ride through device according to claim 1, wherein: The inverter cabinet AC power supply (101a) is connected to a transformer (101a-1) via a circuit breaker, and the output end of the transformer (101a-1) is connected to a circuit breaker and connected to the charging module (102).

3. The low voltage ride through device according to claim 3, wherein: The in-plant DC power supply (101b) is connected to the charging module (102) via a circuit breaker.

4. The low voltage ride through device according to any one of claims 1 to 3, characterized in that: The output end of the charging module (102) is connected to the inverter control power supply (103a) via two circuit breakers connected in series.

5. A peripheral wiring system for a low voltage ride through device, characterized in that: The low voltage ride through device according to any one of claims 1 to 4 further comprises: By electrically connecting the DC protection power supply of the low voltage ride through device to the RTM, the RTM monitors the operation status in real time, and one end of the RTM is electrically connected to the isolation diode to prevent the current from flowing in reverse.

6. The peripheral wiring system of the low voltage ride through device as claimed in claim 5, characterized in that: The output end of the isolation diode is connected to the DC bus terminal of the inverter to convert DC power into AC power to drive the motor or other loads connected to the inverter.

7. A method for operating a low voltage ride through device, characterized in that: The peripheral wiring system of the low voltage ride through device according to any one of claims 5 to 6 further comprises: Check whether the power grid is normal; If yes, the inverter is powered by the three-phase AC power in the factory, and the low voltage ride-through device is in hot standby state; If not, check the value of the grid voltage.

8. The operating method of the low voltage ride through device as claimed in claim 7, wherein: When the grid voltage drops to 0% to 90% or temporarily rises to 110% or 130%, the low voltage ride-through device starts working instantly.

9. The operating method of the low voltage ride through device as claimed in claim 8, characterized in that: When the grid voltage drops to 0% to 90%, the low voltage ride-through device starts, allowing the inverter to continue working for 60 seconds; When the grid voltage temporarily rises to 110%, the inverter working state is adjusted and the inverter continues to work for 60 seconds; When the grid voltage temporarily rises to 130%, the inverter working state is adjusted and the inverter continues to work for 0.5 seconds.

10. The operating method of the low voltage ride through device as claimed in claim 9, characterized in that: When the grid voltage returns to the normal range, the low voltage ride-through device stops working and switches to power supply from the factory power supply.

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