Protection device and converter

Abstract

The utility model relates to the field of electronic circuits, and discloses a protection device and a converter, and the device comprises a controller, and a crowbar loop and a discharge resistor loop which are respectively connected with the controller. The crowbar loop is arranged between two direct-current buses on the direct-current side of equipment to be protected and is connected with the first output end of the controller; the discharge resistor loop comprises a fling-cut switch and a discharge resistor, and the fling-cut switch and the discharge resistor are connected in series and then are arranged between two direct current buses on the direct current side of the to-be-protected equipment; when the crowbar loop breaks down and the to-be-protected device breaks down and shuts down, the switching switch is switched on, and the discharge resistor is switched into the two direct-current buses for discharging. The problem that a protection circuit of an existing device is low in discharging efficiency is solved.

Description

Technical Field

[0001] The present application relates to the field of electronic power, and in particular to a protection device and a converter. Background Art

[0002] Currently, a protection circuit is generally provided in the DC circuit design of the converter, the purpose of which is to discharge and protect the converter and connected electrical equipment when the bus voltage is overvoltage.

[0003] In the related art, protection circuits are mainly designed using two methods: a crowbar circuit and a busbar discharge resistor circuit. The busbar discharge resistor circuit is used in the event of a crowbar circuit failure. Although the circuit can achieve discharge protection, its discharge is relatively slow and its response is also relatively slow, which can easily cause damage to the converter and connected electrical equipment. Utility Model Content

[0004] In view of this, the present application proposes a protection device and a converter to solve the problem of slow discharge efficiency of the protection circuit of the existing converter.

[0005] A first aspect of the present application provides a protection device, comprising: a controller, and a crowbar circuit and a discharge resistor circuit respectively connected to the controller;

[0006] The crowbar loop is provided between two DC buses on the DC side of the device to be protected and is connected to the first output terminal of the controller;

[0007] The discharge resistor circuit includes a switching switch and a discharge resistor. The switching switch and the discharge resistor are connected in series and are arranged between two DC buses on the DC side of the device to be protected. When the crowbar circuit fails and the device to be protected fails and shuts down, the switching switch is closed and the discharge resistor is connected to the two DC buses for discharge.

[0008] In a feasible implementation manner, the switching switch includes a first switch and a first coil, wherein the first switch is connected in series with the discharge resistor, and the first coil is connected to the controller;

[0009] The controller controls the closing or opening of the first switch through the first coil.

[0010] In a feasible implementation manner, the discharge resistance circuit further includes: a relay connected in series with the first coil, the controller outputs a first control signal to the relay, and the relay controls the power on or off of the first coil.

[0011] In a feasible embodiment, the relay includes a second switch and a second coil, the second switch is connected in series with the first coil, the second coil is connected to the second output end of the controller, and the second coil controls the closing or opening of the second switch under the action of the first control signal, thereby controlling the power on or off of the first coil.

[0012] In a feasible implementation manner, the discharge resistance circuit further includes:

[0013] A main circuit switch is provided on the AC side of the device to be protected, comprising a first main contact switch and a first auxiliary contact switch connected in linkage, wherein the first main contact switch is provided on the AC side, and the first auxiliary contact switch is connected in parallel with the second switch to control the power on or off of the first coil.

[0014] In a feasible implementation manner, the discharge resistance circuit further includes:

[0015] A soft-start contactor is provided on the AC side of the device to be protected, comprising a second main contact switch and a second auxiliary contact switch connected in linkage, wherein the second main contact switch is provided on the AC side, and the second auxiliary contact switch is connected in parallel with the second switch to control the power on or off of the first coil.

[0016] In a feasible implementation manner, the first switch is a normally closed switch or a normally open switch.

[0017] In a feasible implementation manner, if the first switch is a normally closed switch, when the crowbar circuit fails and the device to be protected fails and shuts down, the state of the first switch remains closed, and the discharge resistor is connected to the two DC buses for discharge;

[0018] If the first switch is a normally open switch, when the crowbar circuit fails and the device to be protected fails and shuts down, the first switch switches from the normally open state to the closed state, and the discharge resistor is connected to the two DC buses for discharge.

[0019] In a feasible embodiment, the crowbar circuit includes a crowbar component and a crowbar resistor connected in series, and the crowbar component is connected to the controller;

[0020] When the DC side is over-voltage, the controller outputs a second control signal to control the crowbar assembly to place the crowbar resistor into two DC buses for discharge.

[0021] A second aspect of the present application provides a converter, comprising a converter and the protection device described in any one of the first aspects above; wherein the protection device is arranged between two DC buses on the DC side of the converter.

[0022] In the technical solution provided by the present application, the device includes: a controller, and a crowbar circuit and a discharge resistor circuit respectively connected to the controller; the crowbar circuit is arranged between the two DC buses on the DC side of the device to be protected, and is connected to the first output terminal of the controller; the discharge resistor circuit includes a switching switch and a discharge resistor, and the switching switch is connected in series with the discharge resistor and is arranged between the two DC buses on the DC side of the device to be protected; when the crowbar circuit fails and the device to be protected fails and shuts down, the switching switch is closed, and the discharge resistor is put into the two DC buses for discharge. The present application controls whether the discharge resistor in the discharge resistor circuit is put into the DC bus to achieve discharge by setting a switching switch. This setting method can achieve discharge under wind power circuit failure while selecting a discharge resistor with a smaller resistance value to be put into discharge. The discharge speed of a smaller resistance value is faster and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A first schematic diagram of a protection device provided in an embodiment of the present application;

[0024] Figure 2 A second schematic diagram of the protection device provided in an embodiment of the present application;

[0025] Figure 3 A third schematic diagram of the protection device provided in an embodiment of the present application;

[0026] Figure 4 A fourth schematic diagram of the protection device provided in an embodiment of the present application;

[0027] Figure 5 A fifth schematic diagram of the protection device provided in an embodiment of the present application;

[0028] Figure 6 A schematic diagram of a converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application provides a protection device and converter, which mainly adds a switching switch in the circuit of the discharge resistor and realizes the input connection based on the switching switch, so that the discharge resistor can be set to a device with a smaller resistance value, thereby accelerating the discharge when discharging using the discharge resistor, avoiding the problem of damage to the converter or power equipment caused by overvoltage existing for too long.

[0030] The terms "first," "second," "third," "fourth," etc. (if any) in the specification and claims of the present application and in the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that the numbers used in this way are interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or apparatus.

[0031] Current wind power generation systems primarily use converters to convert wind-generated electricity into electricity that meets the national grid's power requirements. A protection circuit for overvoltage protection is provided between the positive and negative DC buses on the converter's DC side. The protection circuit includes a crowbar circuit and a discharge resistor circuit. The crowbar circuit is designed to serve as the primary protection circuit for the DC bus, rapidly discharging in the event of an overvoltage, while the discharge resistor circuit slowly discharges the DC bus in the event of a crowbar circuit failure. Current discharge resistor circuit settings primarily utilize fixed connections and resistors with larger resistance values. However, such a large resistance value results in a long discharge time, and prolonged high voltage can easily damage the converter.

[0032] like Figure 1 As shown, an embodiment of the present application provides a protection device, which is primarily disposed between the busbars on the DC side of the device to be protected. The protection device includes a controller 110, a crowbar circuit 120, and a discharge resistor circuit 130. The controller 110 is connected to the DC busbar and is configured to detect the real-time voltage on the DC busbar and determine whether the real-time voltage is greater than a voltage threshold. If so, the voltage is considered overvoltage; otherwise, the voltage is considered normal. It is understood that the device to be protected may be a converter, such as a wind turbine converter.

[0033] It should be noted that the controller 110 can be a voltage comparison circuit, which collects the real-time voltage on the DC bus and compares it with a preset voltage reference value to output a high-level or low-level signal, thereby realizing overvoltage detection. It can be understood that the present application does not use software to realize analysis and detection when detecting whether the DC bus is overvoltage, but directly uses a detection circuit similar to a voltage comparison circuit to realize it.

[0034] In this embodiment, the controller 110 has at least two output terminals, namely a first output terminal and a second output terminal. The crowbar circuit 120 is arranged between the two DC buses on the DC side of the device to be protected and is connected to the first output terminal of the controller 110. The default state is that the signal of the overvoltage detection result output by the controller 110 is used to control the operation of the crowbar circuit 120. Of course, the crowbar circuit 120 can be set to default operation, which depends on the design requirements of the actual protection device.

[0035] The discharge resistance circuit 130 is connected to the second output end. The discharge resistance circuit 130 includes a switching switch 131 and a discharge resistor 132. The switching switch 131 and the discharge resistor 132 are connected in series and are arranged between two DC buses on the DC side of the device to be protected.

[0036] When the crowbar circuit 120 fails and the device to be protected shuts down due to a fault (which can be understood as DC side overvoltage), the controller 110 outputs a first control signal to control the switching switch 131 to close, and connects the discharge resistor 132 to the two DC buses for discharge.

[0037] It should be noted that multiple DC busbars, such as three, can be provided on the DC side of the device to be protected, one serving as the N pole and the other two as the positive and negative poles, respectively. A protection device is provided between the positive and N poles, and between the negative and N poles. The crowbar circuit 120 and the discharge resistor circuit 130 are connected in parallel and provided between the two DC busbars. When two DC busbars are provided on the DC side, the protection device is provided between the positive and negative DC busbars.

[0038] In another embodiment, the crowbar circuit 120 includes a crowbar component 121 and a crowbar resistor 122 connected in series, and the crowbar component 121 is connected to the controller 110;

[0039] When the DC side is over-voltage, the controller 110 outputs a second control signal to control the crowbar assembly 121 to connect the crowbar resistor 122 to the two DC buses for discharge.

[0040] In summary, by designing the discharge resistor circuit to include at least a switching switch and a discharge resistor, the switching switch and controller used can be used to put the discharge resistor into use when overvoltage occurs and not put it into use when undervoltage occurs. In this way, since there is no need to consider the risk of short circuit, the resistance value of the discharge resistor can be set to a smaller value, so that the DC bus can be discharged quickly when it is put into use, thereby accelerating the discharge speed, improving efficiency, and reducing the probability of damage to devices such as the protected equipment.

[0041] like Figure 2As shown in FIG. 1 , an embodiment of a protection device provided by the present application using a converter with two DC buses (positive and negative) as an example, similarly, the protection device includes a controller 110, a crowbar circuit 120, and a discharge resistor circuit 130, wherein the crowbar circuit 120 and the discharge resistor circuit 130 are connected in parallel and are arranged between the positive and negative DC buses.

[0042] The discharge resistance circuit 130 includes a switching switch 131 and a discharge resistor 132, wherein the switching switch 131 and the discharge resistor 132 are connected in series and are arranged between the positive and negative DC buses of the converter; the switching switch 131 includes a first switch 1311 and a first coil 1312, wherein the first switch 1311 is connected in series with the discharge resistor 132, and the first coil 1312 is connected to the controller 110; the controller 110 controls the closing or opening of the first switch 1311 through the first coil 1312.

[0043] It should be noted that one end of the first coil 1312 is connected to the second output terminal of the controller 110, and the other end of the first coil 1312 is connected to the positive DC bus or another separate power supply. A control signal, such as a high or low level signal, output from the second output terminal is used to control the power on or off of the first coil 1312, thereby controlling the closing or opening of the first switch 1311.

[0044] The first switch 1311 can be selected as normally closed or normally open. Here, it is preferred to select a normally closed state switch. In this case, the first control signal is a disconnect control signal; if the first switch 1311 is a normally open state switch, the first control signal is a closed control signal. For the disconnect control signal. In the initial state, the first coil 1312 should be energized by the second output terminal of the controller 110 outputting a disconnect control signal, and the first switch 1311 is placed in an open state. When the controller 110 detects an overvoltage on the DC bus and a crowbar circuit failure, the first coil 1312 is de-energized by outputting a control signal through the second output terminal, and the first switch 1311 is restored to a normally closed state, thereby putting the discharge resistor 132 into use to discharge the overvoltage on the DC bus until the voltage of the DC bus drops to a normal voltage range, and then the power control of the first coil 1312 is restored. When the first switch 1311 is selected as a normally open switch, its control principle is opposite to that of the normally closed switch.

[0045] In another embodiment, the discharge resistance circuit 130 further includes: a relay 133 connected in series with the first coil 1312 , and the controller 110 outputs a first control signal to the relay 133 , and the relay 133 controls the power on or off of the first coil 1312 .

[0046] It should be noted that the relay 133 is a normally open relay, that is, it includes a second switch 1331 and a second coil 1332. The second switch 1331 is connected in series with the first coil 1312. The second coil 1332 is connected to the second output end of the controller 110. The second coil 1332 controls the closing or opening of the second switch 1331 under the action of the first control signal, thereby controlling the power on or off of the first coil 1312.

[0047] like Figure 3 As shown, the second switch 1331 is connected in series with the first coil 1312 and is arranged between the positive and negative poles of the DC bus. The voltage of the two DC buses provides the first coil 1312 with an operating voltage. The second coil 1332 is connected through the controller 110 and realizes power-on or power-off operations under the control of the controller 110.

[0048] In practical applications, one end of the second coil 1332 is connected to the second output terminal of the controller 110, and the other end is connected to a separate power supply. Here, the first switch 1311 is still selected as a normally closed switch to illustrate its working principle. Figure 3 In the structure, the controller 110 sends a control signal to the second coil 1332, causing the magnetic field generated by the second coil 1332 to attract the second switch 1331, thereby energizing the first coil 1312 and triggering the operation of the first switch 131, that is, the contact of the first switch 131 is turned from the normally closed state to the open state. Under normal circumstances, the switching switch 131 is actuated to turn the discharge resistor 132 into the open state. When the crowbar circuit 120 fails and the DC bus voltage cannot be discharged normally, the controller 110 sends a control signal to the relay 133 to disconnect it; or when the entire machine is powered off or the control circuit is powered off, the switching switch 131 returns to the normally closed contact state, and the discharge resistor 132 is put into the circuit to discharge.

[0049] like Figure 4 , which is a schematic diagram of an embodiment of three DC busbars, a crowbar loop 120 and a discharge resistor loop 130 are provided between DC busbars 1 and 2 , and between DC busbars 2 and 3 .

[0050] In another embodiment, the discharge resistance circuit 130 further includes:

[0051] The main circuit switch 134 provided on the AC side of the converter includes a first main contact switch and a first auxiliary contact switch connected in linkage. The first main contact switch is provided on the AC side, and the first auxiliary contact switch is connected in parallel with the second switch 1331 to control the power on or off of the first coil 1312.

[0052] like Figure 5As shown, the first main contact switch of the main circuit switch 134 is connected in series in the main circuit of the AC side of the converter, and the first auxiliary contact switch is connected in parallel with the second switch 1331 (that is, it is set on the DC side). When the circuit on the AC side is normal, the main circuit switch 134 remains in a closed state, that is, the first switch 1311 remains switched to an open state from the default normally closed state, thereby ensuring that the discharge resistance circuit is not put into the DC bus to form a discharge circuit.

[0053] In another embodiment, the discharge resistance circuit 130 further includes:

[0054] The soft-start contactor 135 provided on the AC side of the converter includes a second main contact switch and a second auxiliary contact switch connected in linkage. The second main contact switch is provided on the AC side, and the second auxiliary contact switch is connected in parallel with the second switch 1331 to control the power on or off of the first coil 1312.

[0055] like Figure 5 As shown, the soft-start contactor 135 is a charging buffer contactor on the AC side, that is, when starting the power generation operation, the electrical equipment on the AC side will enter the charging buffer period, and the soft-start contactor 135 is closed at the same time, that is, the second main contact switch and the second auxiliary contact switch are closed at the same time. After charging is completed, they are disconnected and control the main circuit switch 134 to be closed.

[0056] It should be noted that, because this application uses a switching method to control the discharge resistor, the discharge resistor does not need to be constantly connected. Therefore, the discharge resistor is selected to have a relatively low resistance to accelerate discharge, such as below 1K, or even tens of ohms. However, the discharge resistor cannot operate in the circuit for a long time. To prevent damage to the controller 110 or logic errors, a hardware interlock is added. Specifically, the auxiliary contacts of the slow-start contactor 135 and the main circuit switch 134 are connected in parallel. During the slow-start / soft-start process, the slow-start contactor 135 needs to be activated (i.e., closed). Simultaneously, the switching switch 131 is also activated when the main circuit switch 134 is activated (i.e., closed), which in turn activates the switching switch 131. Simultaneously, the signal contactor 133, controlled by the controller 110, is also activated (i.e., closed) upon initial power-up. These three control groups ensure that the switching switch 131 operates normally, disconnecting the discharge resistor 132, in the absence of any faults.

[0057] The slow start contactor 135 will be disconnected after the pre-charge delay period ends, and the main circuit switch 134 will be operated and closed during operation, so as to ensure that the relay 133 control circuit will not lose power when the machine is running. The main circuit switch 134 will be disconnected when the machine stops / failures occur.

[0058] Through the implementation of the protection device provided in this embodiment, a switching switch is used to control the discharge resistor to be put into the circuit, so that a resistor with a smaller resistance value can be selected. When put into use, it can work and discharge quickly, reducing the probability of device damage caused by overvoltage for too long, and at the same time, it can also reduce DC side electric shock accidents during maintenance.

[0059] The present application also provides a converter, such as Figure 6 As shown, the converter includes: a converter 610 and a protection device 620 provided in the above embodiment; wherein the protection device 620 is provided between two DC buses on the DC side of the converter 620 .

[0060] It should be noted that multiple protection devices 620 may be provided, and the number of protection devices 620 is determined by the number of DC buses provided on the converter. The figure uses two DC buses and one protection device 620 as an example. The input of the controller 110 is connected to the two DC buses to collect the voltages of the two DC buses to determine whether there is overvoltage. If there are three DC buses, two protection devices 620 are provided.

[0061] The crowbar circuit 120 and the discharge resistor circuit 130 are connected in parallel between the two DC bus bars and are respectively connected to the first output terminal and the second output terminal of the controller 110. Of course, the crowbar circuit 120 may also be uncontrolled by the controller 110, but it will still be connected to the controller 110 for detecting faults in the crowbar circuit.

[0062] Specifically, the first switch 1311 and the discharge resistor 132 in the discharge resistor 130 are connected in series and are arranged on the two DC bus bars. The first coil 1312 and the second switch 1331 are also connected in series and are arranged on the two DC bus bars. The second coil 1332 is connected to the second output terminal of the controller 110 and the 24V power supply. At the same time, switches QF1 and KM1 are also connected in parallel to the first switch 1311, where QF1 is the auxiliary contact in the main circuit switch and KM1 is the auxiliary contact in the soft start contactor.

[0063] The operating principle of this overvoltage discharge protection is as follows: Here, first switch 1311 is assumed to be a normally closed switch. When the voltages of the two DC buses are normal, controller 110 energizes second coil 1312, which in turn closes second switch 1331. Simultaneously, first coil 1312 is energized, thereby opening first switch 1311 and, consequently, disconnecting the entire discharge resistor circuit 130. During this process, QF1 and KM1 are also closed, ensuring that discharge resistor circuit 130 is disconnected.

[0064] When the voltage of the two DC buses is overvoltage, the controller 110 detects whether the crowbar circuit 120 is faulty. If not, the control of the discharge resistor circuit 130 is maintained to be disconnected. If there is a fault or the overvoltage time reaches a threshold, the controller 110 controls the second coil 1332 to be de-energized, thereby disconnecting the second switch 1331. Further, the first coil 1312 is de-energized, and the second switch 1331 returns to the normally closed state. At this time, the discharge resistor 132 is put into the DC bus to form a discharge circuit for rapid discharge.

[0065] In summary, a protection device comprising a controller, a crowbar circuit, and a discharge resistor circuit, each connected to the controller, is used to provide overcurrent protection for components such as converters. The crowbar circuit is located between the two DC buses on the DC side of the converter and is connected to the first output terminal of the controller. The discharge resistor circuit includes a switching switch and a discharge resistor, which are connected in series and located between the two DC buses on the DC side of the converter. When the crowbar circuit fails and the DC side is overvoltage, the switching switch closes, and the discharge resistor is connected to the two DC buses for discharge. This solves the problem of slow discharge efficiency in existing converter protection circuits.

[0066] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The scope of protection of the present application is not limited thereto. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art who is familiar with the technical field can still modify the technical solutions described in the above embodiments within the technical scope disclosed in the present application, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate from the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A protective device, characterized in that: The protection device includes: a controller, and a crowbar circuit and a discharge resistance circuit respectively connected to the controller; The crowbar loop is provided between two DC buses on the DC side of the device to be protected and is connected to the first output terminal of the controller; The discharge resistor circuit includes a switching switch and a discharge resistor. The switching switch and the discharge resistor are connected in series and are arranged between two DC buses on the DC side of the device to be protected. When the crowbar circuit fails and the device to be protected fails and shuts down, the switching switch is closed and the discharge resistor is connected to the two DC buses for discharge.

2. The protection device according to claim 1, characterized in that The switching switch includes a first switch and a first coil, wherein the first switch is connected in series with the discharge resistor, and the first coil is connected to the controller; The controller controls the closing or opening of the first switch through the first coil.

3. The protection device according to claim 2, characterized in that: The discharge resistance circuit further includes: a relay connected in series with the first coil, and the controller outputs a first control signal to the relay, so that the relay controls the power on or off of the first coil.

4. The protection device according to claim 3, characterized in that: The relay includes a second switch and a second coil. The second switch is connected in series with the first coil. The second coil is connected to the second output end of the controller. The second coil controls the closing or opening of the second switch under the action of the first control signal, thereby controlling the power on or off of the first coil.

5. The protection device according to claim 4, characterized in that: The discharge resistance circuit also includes: A main circuit switch is provided on the AC side of the device to be protected, comprising a first main contact switch and a first auxiliary contact switch connected in linkage, wherein the first main contact switch is provided on the AC side, and the first auxiliary contact switch is connected in parallel with the second switch to control the power on or off of the first coil.

6. The protection device according to claim 5, characterized in that: The discharge resistance circuit also includes: A soft-start contactor is provided on the AC side of the device to be protected, comprising a second main contact switch and a second auxiliary contact switch connected in linkage, wherein the second main contact switch is provided on the AC side, and the second auxiliary contact switch is connected in parallel with the second switch to control the power on or off of the first coil.

7. The protection device according to any one of claims 2 to 6, characterized in that: The first switch is a normally closed switch or a normally open switch.

8. The protection device according to claim 7, characterized in that: If the first switch is a normally closed switch, when the crowbar circuit fails and the device to be protected fails and stops, the state of the first switch remains closed, and the discharge resistor is connected to the two DC buses for discharge; If the first switch is a normally open switch, when the crowbar circuit fails and the device to be protected fails and shuts down, the first switch switches from the normally open state to the closed state, and the discharge resistor is connected to the two DC buses for discharge.

9. The protection device according to claim 1, characterized in that: The crowbar circuit includes a crowbar component and a crowbar resistor connected in series, and the crowbar component is connected to the controller; When the DC side is over-voltage, the controller outputs a second control signal to control the crowbar assembly to place the crowbar resistor into two DC buses for discharge.

10. A converter, characterized in that: The converter includes a converter and a protection device according to any one of claims 1 to 9, wherein the protection device is arranged between two DC buses on the DC side of the converter.

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