Zero-crossing trigger circuit of bidirectional thyristor and circuit board

Abstract

The utility model relates to a zero-crossing trigger circuit of a bidirectional thyristor and a circuit board. The circuit comprises a switching control circuit and a switch driving circuit. The switching control circuit is used for detecting the alternating current zero-crossing state of the power system, the input end receives a switching signal, and the output end is connected with the input end of the switch driving circuit so as to control the input end of the switch driving circuit to generate an opening and closing signal when the switching signal is received and the alternating current crosses zero. The switch driving circuit comprises a control resistor, a first diode and a second diode which are connected in series, the first diode and the second diode which are reversely arranged are respectively connected with a sixth resistor and a seventh resistor in parallel, the series starting end serves as an output end and is connected with the main electrode of the bidirectional thyristor, and two ends of the control resistor are two sides of one group of input ends. The control electrode of the first silicon controlled rectifier of the bidirectional thyristor is connected with one side of the input end of the switch driving circuit close to the anode of the first silicon controlled rectifier, and the control electrode of the second silicon controlled rectifier is connected with the other side of the input end. Current impact at the moment of on-off of the bidirectional thyristor can be reduced.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic equipment, and in particular to a zero-crossing trigger circuit and a circuit board of a bidirectional thyristor. Background Art

[0002] With the development of power electronics technology, in order to improve production efficiency and safety, a large number of nonlinear power load devices, such as thyristor rectifier power supplies and variable frequency speed regulation equipment, have begun to be used in the production process of high-power electrical equipment. However, during use, these nonlinear power loads will generate a large amount of harmonic current, consume the reactive power of the power system, and reduce the quality of power. Therefore, reactive compensation devices and electronic switches (such as bidirectional thyristors) are connected to such power systems, and the on and off of the electronic switches are used to control whether the reactive compensation devices are effectively connected to the power system for reactive compensation.

[0003] However, the instant of electronic switch on and off will cause current shock to the power system and its power load, pollute the power system grid, and interfere with the power load.

[0004] Therefore, how to better control the on and off of electronic switches such as bidirectional thyristors and reduce the current impact at the moment of on and off has become an urgent problem to be solved by those skilled in the art. Utility Model Content

[0005] In order to better control the on and off of electronic switches such as bidirectional thyristors and reduce the current impact at the moment of on and off, the present application provides a zero-crossing trigger circuit and circuit board for a bidirectional thyristor.

[0006] A zero-crossing trigger circuit of a bidirectional thyristor provided to achieve the purpose of the utility model comprises:

[0007] Switching control circuit and switch driving circuit;

[0008] The switch driving circuit comprises a first diode, a sixth resistor, a control resistor, a second diode and a seventh resistor, wherein the positive terminal of the first diode is electrically connected to a main electrode of the bidirectional thyristor as an output terminal of the switch driving circuit, the negative terminal of the first diode is electrically connected to the negative terminal of the second diode through the control resistor, the positive terminal of the second diode is electrically connected to the other main electrode of the bidirectional thyristor as another output terminal of the switch driving circuit, the two ends of the control resistor are both sides of an input terminal of the switch driving circuit, the sixth resistor is connected in parallel to the two ends of the first diode, and the seventh resistor is connected in parallel to the two ends of the second diode;

[0009] The switching control circuit is suitable for detecting the zero-crossing point of the power system connected to the bidirectional thyristor, the input end of the switching control circuit is electrically connected to the reactive power compensation controller to receive the switching signal output by the controller, and the output end of the switching control circuit is electrically connected to the input end of the switch drive circuit, and is used to control the input end of the switch drive circuit to generate a switching signal for controlling the switching of the bidirectional thyristor when receiving the switching signal and detecting that the voltage of the power system crosses the zero point;

[0010] The bidirectional thyristor is provided with a first thyristor and a second thyristor connected in reverse parallel, the control electrode of the first thyristor and the control electrode of the second thyristor are respectively electrically connected to the two sides of the input end of the switch drive circuit to receive the opening and closing signal, and the control electrode of the first thyristor is electrically connected to the side of the input end of the switch drive circuit close to the anode of the first thyristor.

[0011] According to another aspect of the present application, a zero-crossing trigger circuit board of a bidirectional thyristor is provided, and the zero-crossing trigger circuit board of the bidirectional thyristor is provided with the aforementioned zero-crossing trigger circuit of the bidirectional thyristor.

[0012] Compared with the simple opening and closing of the existing electronic switch, if the on-off node of the electronic switch is not controlled, the on-off moment of the electronic switch will cause current impact and interference to the power system and its power load, shortening the service life. The on-off control method of the bidirectional thyristor provided in the present application can reduce the impact voltage and current borne by the thyristor, reduce the harmonic component of the output voltage, and reduce its pollution to the power grid and interference with the power load. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A circuit diagram showing a zero-crossing trigger circuit of a bidirectional thyristor according to an embodiment of the present application;

[0014] Figure 2 A circuit diagram showing a zero-crossing trigger circuit of a bidirectional thyristor according to an embodiment of the present application;

[0015] Figure 3 The internal structure diagram of the MOC3083 optocoupler according to the embodiment of the present application is shown;

[0016] Figure 4 The internal structure diagram of the MOC3083 optocoupler according to the embodiment of the present application is shown;

[0017] Figure 5 A schematic structural diagram of a circuit board according to an embodiment of the present application is shown.

[0018] Bidirectional thyristor 100, first thyristor Q1, control electrode G1 of the first thyristor, second thyristor Q2, control electrode G2 of the second thyristor, switch drive circuit 200, first diode D1, sixth resistor R6, one control resistor R1, another control resistor R2, another control resistor R3, second diode D2, seventh resistor R7, one MOC3083 optocoupler U1, another MOC3083 optocoupler U2, another MOC3083 optocoupler U3, switching control circuit 300, light emitting diode 310 of MOC3083 optocoupler, three-terminal bidirectional thyristor 320 of MOC3083 optocoupler, zero crossing detection circuit 330, voltage divider resistor R0, RC buffer circuit 400, one buffer resistor R4, another buffer resistor R5, capacitor C1. DETAILED DESCRIPTION

[0019] Various exemplary embodiments, features and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0020] Among them, it should be understood that the directions or positional relationships indicated by terms such as "length", "width", "height", "up", "down", "front", "back", "left", "right", "top", "bottom", "inside" and "outside" are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0021] In addition, in order to better illustrate the present application, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present application.

[0022] The present application provides a zero-crossing trigger circuit of a bidirectional thyristor, comprising a switching control circuit 300 and a switch driving circuit 200. The switch driving circuit 200 comprises a first diode, a sixth resistor, a control resistor (a resistor to be switched), a second diode and a seventh resistor, wherein the positive terminal of the first diode is electrically connected to a main electrode of the bidirectional thyristor as an output terminal of the switch driving circuit 200, the negative terminal of the first diode is electrically connected to the negative terminal of the second diode through the control resistor, the positive terminal of the second diode is electrically connected to another main electrode of the bidirectional thyristor as another output terminal of the switch driving circuit 200, the two ends of the control resistor are both sides of an input terminal of the switch driving circuit 200, the sixth resistor is connected in parallel to the two ends of the first diode, and the seventh resistor is connected in parallel to the two ends of the second diode;

[0023] The switching control circuit 300 is suitable for detecting the zero-crossing point of the power system connected to the bidirectional thyristor. The (switching control signal of the reactive compensation controller) input end of the switching control circuit 300 is electrically connected to the reactive compensation controller to receive the switching signal output by the reactive compensation controller. The output end of the switching control circuit 300 is electrically connected to the input end of the switch drive circuit 200, and is used to control the input end of the switch drive circuit 200 to generate a switching signal for controlling the bidirectional thyristor to be switched when the switching signal is received and the voltage of the power system is detected to have a zero-crossing point. Specifically, if the switching signal is an access signal, the control resistor is controlled to be short-circuited. The bidirectional thyristor is provided with a first thyristor and a second thyristor connected in reverse parallel. The control electrode of the first thyristor and the control electrode of the second thyristor are electrically connected to both sides of the input end of the switch drive circuit 200 to receive the switching signal. The first thyristor is arranged in reverse to the first diode, and the control electrode of the first thyristor is electrically connected to the side of the input end of the switch drive circuit 200 connected to the first diode. The control electrode of the first thyristor is electrically connected to one side of the input end of the switch driving circuit 200 close to the anode of the first thyristor (that is, the control resistor between the two sides of the input end is close to the anode of the first thyristor), and this side is directly connected to one end of the main electrode close to the anode of the first thyristor through D1 / D2 / . The control electrode of the second thyristor is electrically connected to one side of the input end of the switch driving circuit 200 close to the anode of the second thyristor.

[0024] It should be noted that the "switching control" of the switching control circuit 300 means: connecting the control resistor to the brake unit (switching control circuit 300). On the premise that the switching control circuit 300 detects that the voltage of the power system passes through the zero point: the switching control circuit 300 issues an input signal (connecting its own short-circuiting circuit to the input end of the switch drive circuit 200), controls the control resistor between the input ends of the short-circuiting switch drive circuit 200, and thus generates an opening and closing signal (for the bidirectional thyristor to close and turn on) at the input end of the switch drive circuit 200. The switching control circuit 300 issues a cut-off signal (cutting off its own short-circuiting circuit from the input end of the switch drive circuit 200), and the control resistor connected to the switch drive circuit 200 works normally, and generates an opening and closing signal (for the bidirectional thyristor to disconnect) at the input end of the switch drive circuit 200, see below for details.

[0025] In the zero-crossing trigger circuit of the bidirectional thyristor, "zero-crossing trigger" means that the bidirectional thyristor, as an electronic switch used for reactive power compensation in AC circuits, is turned on and off when the AC current passes through zero or near zero. This on-off control method can reduce the impact voltage and current borne by the thyristor, reduce the harmonic components of the output voltage, and will not pollute the power grid or interfere with the equipment.

[0026] The present application sets a switching control circuit 300, which has the dual functions of receiving the switching signal of the reactive compensation controller and detecting the voltage zero-crossing signal of the power system to which the reactive compensation device of the bidirectional thyristor and its control switch is connected, and can generate the control signal of the switching control circuit 300 according to the switching signal of the (controller switching signal) input end and the zero-crossing signal of the (power system) zero-crossing detection end, and output this control signal at its output end. The switch driving circuit 200 generates the opening and closing signal for controlling the opening and closing of the bidirectional thyristor according to the control signal output and transmitted by the switching driving circuit. That is, the zero-crossing trigger circuit of the bidirectional thyristor provided in the present application can control the bidirectional thyristor to be turned on when the voltage of the power system passes through zero under the control of the reactive compensation controller, so as to start the reactive compensation work of the power system; it can also control the bidirectional thyristor to be turned off under the control of the reactive compensation controller, so as to stop the reactive compensation work of the power system.

[0027] The present application divides the voltage by adding the sixth resistor and the seventh resistor to prevent the two main electrodes of the bidirectional thyristor from being short-circuited after the control resistor is short-circuited, and the switch of the reactive power compensation device is only controlled by the bidirectional thyristor. When a voltage difference is generated between the two main electrodes (K1 and K2) of the bidirectional thyristor 100: when the voltage on the side of one main electrode K1 of the bidirectional thyristor 100 is higher than that on the side of the other main electrode K2, the first diode D1 is turned on, and the sixth resistor R6 is short-circuited; the second diode D2 is turned off, and the AC side loop current flows through the seventh resistor R7. When the voltage on the K2 side is higher than that on the K1 side, the first diode D1 is turned off, and the AC side loop current flows through the sixth resistor R6; the second diode D2 is turned on, and the seventh resistor R7 is short-circuited.

[0028] It should be noted that if the reactive power compensation controller outputs a cut-off signal (does not output 12V DC), then regardless of whether the AC power of the power system passes through zero, the switching control circuit 300 cannot generate its control signal, nor can it control the input end of the driving switch circuit to generate an opening and closing signal for the bidirectional thyristor. If the reactive power compensation controller outputs an access signal (12V DC), then when the AC power of the power system passes through zero, the bidirectional thyristor is started, and the reactive power compensation device is connected to the power system to perform reactive power compensation; after crossing the zero point, the bidirectional thyristor is disconnected, and the reactive power compensation device is cut out of the power system and no longer performs reactive power compensation. Specifically:

[0029] When the zero-crossing detection terminal of the switching control circuit 300 detects that the power system voltage crosses zero, the short-circuit circuit of the switching control circuit 300 is triggered to be put into the two ends of the control resistor, short-circuiting the control resistor. Therefore, the control electrode G1 of the first thyristor Q1 and the control electrode G2 of the second thyristor Q2 connected to the two ends of the control resistor are both high level, and the control electrodes (gates) of Q1 and Q2 have trigger current. When a voltage difference is generated between the two main electrodes K1 and K2 of the bidirectional thyristor 100, for example ( Figure 1 When the voltage of K1 is higher than that of K2, Q2 is turned on, the reactive power compensation device is connected to the power system, and the reactive power compensation work is started; when the voltage of K1 is lower than that of K2, Q1 is turned on, the reactive power compensation device is connected to the power system, and the reactive power compensation work is started.

[0030] Then the switching control circuit 300 detects that the alternating current of the power system is no longer at zero position, and no longer generates and transmits control signals to the output end of the switch driving circuit 200. The control resistor is no longer short-circuited and works normally, and the potential on the front side of the control resistor is high, and the potential on the back side is low. The control electrode G1 of the first thyristor Q1 connected to the site on the front side of the control resistor (current direction) is at a high potential, and the control electrode G2 of the second thyristor Q2 connected to the site on the back side of the control resistor is at a low potential. At this time, the control (gate) electrode of the first thyristor Q1 has a trigger current, but because the voltage on the K1 side is higher than that on the K2 side at this time, the first thyristor Q1 is in a reverse cut-off state and does not meet the trigger condition; the second thyristor Q2 has no trigger current and does not meet the trigger condition. Therefore, the two main electrodes K1 and K2 of the bidirectional thyristor 100 are in a disconnected cut-off state, and the reactive power compensation work of the power system is stopped.

[0031] Compared with the simple opening and closing of the existing electronic switch, if the on-off node of the electronic switch is not controlled, the on-off moment of the electronic switch will cause current impact and interference to the power system and its power load, shortening the service life. The on-off control method of the bidirectional thyristor provided in the present application can reduce the impact voltage and current borne by the thyristor, reduce the harmonic component of the output voltage, and reduce its pollution to the power grid and interference with the power load.

[0032] In a possible implementation, the switching control circuit 300 is provided with a zero-crossing detection circuit and a short-circuit circuit, the control end of the zero-crossing detection circuit is electrically connected to the reactive power compensation controller as the input end of the switching control circuit 300, and the reactive power compensation controller controls the on-off of the zero-crossing detection circuit, thereby starting / stopping the zero-crossing detection work of the alternating current of the power system. The input end of the zero-crossing detection circuit (as the zero-crossing detection end of the switching control circuit 300 and electrically connected to the power system) is suitable for connecting to the circuit to be detected to detect the zero-crossing point of its alternating current, and the output end of the zero-crossing detection circuit is electrically connected to the control end of the short-circuit circuit to control the on-off of the short-circuit circuit. The short-circuit circuit is electrically connected between the two sides of the input end of the driving switch circuit.

[0033] Furthermore, both sides of the input end of the zero-crossing detection circuit are electrically connected to the two ends of the control resistor, so as to be connected to the power grid of the power system to detect the zero-crossing point of the alternating current of the power system.

[0034] Furthermore, the switching control circuit 300 includes a thyristor optocoupler with zero-crossing detection, which includes a light-emitting diode, a zero-crossing detection circuit and a short-circuit circuit, wherein the short-circuit circuit uses a triac.

[0035] The positive and negative electrodes of the light emitting diode are suitable for serving as two sides of a set of input terminals of the switching control circuit 300, and are electrically connected to two sides of the output terminal of the reactive power compensation controller to receive the switching signal. The two main electrodes of the triac are electrically connected to two sides of the input terminal of the switch driving circuit 200, respectively, to control the input terminal of the switch driving circuit 200 to generate the opening and closing signal of the bidirectional thyristor.

[0036] The zero-crossing detection circuit is provided with a photosensitive element, and the light-emitting state of the light-emitting diode is suitable for controlling the conduction state of the zero-crossing detection circuit. The former light-emitting controls the latter photosensitive element to be turned on, thereby turning on the zero-crossing detection circuit for effective detection and control. If it emits light, it is closed for zero-crossing detection, and if it does not emit light, it is cut off and does not perform zero-crossing detection.

[0037] The zero-crossing detection circuit forms and outputs a signal to control the conduction state between the two main electrodes of the three-terminal bidirectional thyristor according to the zero-position detection result. The two sides of the input end of the zero-crossing detection circuit are electrically connected to the two sides of the control resistor respectively to perform zero-position detection of the alternating current, and the output end of the zero-crossing detection circuit is electrically connected to the control electrode of the three-terminal bidirectional thyristor.

[0038] The zero-crossing detection circuit starts the zero-crossing detection of the alternating current when the light-emitting diode is activated and turned on. After detecting that the alternating current crosses zero, the control electrode of the triac controls the conduction of its two main electrodes. After the two main electrodes of the triac are turned on, the control resistor is short-circuited, and the control electrodes of the first thyristor and the second thyristor are both at high potential, triggering the conduction between the two main electrodes of the bidirectional thyristor 100, and using the bidirectional thyristor 100 to perform reactive power compensation of the power system, eliminate power harmonics, and ensure the quality of power.

[0039] When the power system does not need to perform reactive power compensation, the reactive power compensation controller does not output current or voltage, the light-emitting diode of the optocoupler cannot emit light, the zero-crossing detection circuit is always in the disconnected state, cannot detect the zero-position state of the alternating current, cannot output a control signal to the control electrode of the triac, and the two main electrodes of the triac are cut off. At this time, the switching control circuit 300 is invalid, the two main electrodes of the bidirectional thyristor 100 are disconnected, and the bidirectional thyristor 100 does not perform reactive power compensation on the power system.

[0040] When the power system needs to perform reactive power compensation, the reactive power compensation controller outputs a control current to make the light-emitting diode emit light, thereby turning on the two main electrodes of the three-terminal bidirectional thyristor and short-circuiting the control resistor. The control electrode G1 of the first thyristor connected at both ends of the control resistor and the control electrode G2 of the second thyristor are both at high potential, and the current direction is forward, which can trigger the conduction between the two main electrodes of the bidirectional thyristor 100. The bidirectional thyristor 100 is used to perform reactive power compensation for the power system, eliminate power harmonics, and ensure the quality of power.

[0041] In a possible implementation, the switching control circuit 300 includes a thyristor optocoupler with zero-crossing detection, the number of which is consistent with the number of input terminals of the switch drive circuit 200 and connected one-to-one; the input terminal of the thyristor optocoupler with zero-crossing detection is electrically connected to the reactive power compensation controller as the input terminal of the zero-crossing trigger circuit, and the output terminal of the thyristor optocoupler with zero-crossing detection is electrically connected to the corresponding input terminal in the switch drive circuit 200 as the output terminal of the zero-crossing trigger circuit.

[0042] The thyristor optocoupler with zero-crossing detection adopts the MOC3083 optocoupler, and the two ends of the light-emitting diode 310 of the MOC3083 optocoupler are electrically connected to the output end of the reactive power compensation controller as the input end of the switching control circuit 300. The light-emitting state of the light-emitting diode is suitable for controlling the conduction state between the two main electrodes of the three-terminal bidirectional thyristor 320 of the MOC3083 optocoupler. The input end of the zero-crossing detection circuit 330 is electrically connected to the two ends of the control resistor through the fourth pin and the sixth pin, and the output end of the zero-crossing detection circuit 330 is electrically connected to the control electrode of the three-terminal bidirectional thyristor 320. The two main electrodes of the three-terminal bidirectional thyristor 320 are electrically connected to the two ends of the control resistor through the fourth pin and the sixth pin of the optocoupler.

[0043] like Figure 1 As shown in the figure, MOC3083 optocoupler is mainly used in industrial devices that require switch control at 240V low-voltage AC grid level. The pin distribution of MOC3083 optocoupler is as follows Figure 2 As shown, it includes a first pin (ANODE), a second pin (CATHODE), a third pin (N / C), a fourth pin (MAIN RERM), a fifth pin (N / C), and a sixth pin (MAIN RERM). The two ends (positive and negative electrodes, anode and cathode) of the light-emitting diode 310 are electrically connected to the two sides of the output end of the reactive power compensation controller through the first pin and the second pin, respectively, which is called the DC side circuit of the MOC3083 optocoupler. The two main electrodes of the triac 320 are electrically connected to the two sides of the input end of the driving switch circuit through the fourth pin and the sixth pin, respectively, which is called the low-voltage AC main circuit of the MOC3083 optocoupler.

[0044] When there is a trigger current greater than 5mA between the first pin and the second pin, the internal light emitting diode 310 can be lit. At this time, the zero-crossing detection circuit 330 in the MOC3083 optocoupler detects the primary voltage between the fourth pin and the sixth pin. If the voltage crosses zero, the triac is triggered to change the fourth pin and the sixth pin from the off state to the on state, and the bidirectional thyristor 100 is turned on to perform reactive power compensation. On the contrary, when the current between the first pin and the second pin disappears, the fourth pin and the sixth pin are cut off, the bidirectional thyristor 100 is turned off, and reactive power compensation is no longer performed.

[0045] The present application sets up a zero-crossing trigger circuit based on the MOC3083 optocoupler, and the reactive compensation controller controls the output of a 12V DC voltage. When the power system does not need reactive compensation, the reactive compensation controller is operated to send a cut-off signal to cut off the input end of the optocoupler self-driving switch circuit (for example, no voltage is output), the DC side of the light-emitting diode 310 has no voltage and does not emit light, the MOC3083 optocoupler is not triggered, the fourth pin and the sixth pin are disconnected, and the AC side loop current flows through the control resistors R1, R2, and R3. And:

[0046] When the voltage on one of the main electrodes K1 of the bidirectional thyristor 100 is higher than that on the other main electrode K2, the first diode D1 is turned on, and the sixth resistor R6 is short-circuited; the second diode D2 is turned off, and the AC side loop current flows through the seventh resistor R7. The potential on the front side of the control resistor is high and the potential on the rear side is low. G1 connected to the site on the front side of the control resistor (them) along the current direction is at a high potential, and G2 connected to the site on the rear side of the control resistor (them) is at a low potential. At this time, the Q1 control electrode of the bidirectional thyristor 100 has a trigger current, but because the voltage on the K1 side is higher than that on the K2 side at this time, Q1 is in a reverse cut-off state and does not meet the trigger condition; Q2 has no trigger current and does not meet the trigger condition. Therefore, the two main electrodes of the bidirectional thyristor 100 are in a disconnected cut-off state, and the reactive power compensation device is not connected to the power system, and will not perform reactive power compensation on the power system.

[0047] When the voltage on the K2 side is higher than that on the K1 side, the first diode D1 is cut off, and the AC side loop current flows through the sixth resistor R6; the second diode D2 is turned on, and the seventh resistor R7 is short-circuited. The potential on the front side of the control resistor is high, and the potential on the back side is low. G1 is at a low potential, and G2 is at a high potential. At this time, there is no trigger current in the Q1 control electrode of the bidirectional thyristor 100, and the trigger condition is not met; Q2 has a trigger current, but because the voltage on the K2 side is higher than that on the K1 side at this time, Q1 is in a reverse cut-off state and does not meet the trigger condition. Therefore, the two main electrodes of the bidirectional thyristor 100 are in a disconnected cut-off state, and the reactive power compensation device is not connected to the power system, and will not perform reactive power compensation on the power system.

[0048] When the power system needs to perform reactive power compensation, the reactive power compensation controller is operated to send a signal to short the control resistor by short-circuiting the circuit. The DC side of the light-emitting diode 310 inputs a 12V DC voltage to emit light. When the zero-crossing detection circuit 330 works and detects that the AC power at both ends of the control resistor (also between K1 and K2) passes through zero, the three-terminal bidirectional thyristor 320 is triggered to conduct, and the AC side loop current flows through the control resistors R1, R2, and R3, which are all short-circuited. Therefore, the current flows through the inside of the optocoupler. At this time, the voltage difference between K1 and K2 is generated from the zero point of the AC power:

[0049] When the voltage on the K1 side is higher than that on the K2 side, D1 is turned on, D2 is turned off, R6 is short-circuited, G1 and G2 are both at high potential, there are trigger currents on the gates of Q1 and Q2, and Q1 cannot be turned on in the reverse direction; the voltage on the anode K1 of Q2 is greater than the cathode K2. At this time, the second thyristor Q2 satisfies both conduction conditions at the same time, and Q2 is turned on.

[0050] When the voltage on the K2 side is higher than that on the K1 side, there are trigger currents on the gates of Q1 and Q2, and Q2 cannot be turned on in the reverse direction; the voltage on the anode K2 of the first thyristor Q1 is greater than that on the cathode K2, and Q1 is turned on.

[0051] The zero-crossing trigger circuit based on MOC3083 can realize zero-crossing triggering, and has fast triggering response, reliable stability and strong anti-interference ability. It can be applied to the automatic switching of filters and reactive compensation devices composed of bidirectional thyristors. It can detect the zero-position state of the AC power between the two main electrodes of the bidirectional thyristor in real time, realize zero-crossing triggering, reduce the impact current generated during switching, achieve fast contactless switching of filters or reactive compensation devices, and improve the power quality of the power grid.

[0052] In a possible implementation, the switching control circuit 300 includes at least two or more thyristor optocouplers with zero-crossing detection connected in series. It should be noted that the series connection of the two or more thyristor optocouplers with zero-crossing detection is to connect the light-emitting diodes 310 of each optocoupler in series (and the two ends of the series connection serve as the input ends of the switching control circuit 300) to the output end of the reactive power compensation controller. In addition, the series start end of the thyristor optocoupler with zero-crossing detection is electrically connected to the reactive power compensation controller as the input end of the zero-crossing trigger circuit, and the output end of each thyristor optocoupler with zero-crossing detection is electrically connected to the corresponding input end of the switch drive circuit 200 as an output end of the zero-crossing trigger circuit. The switch drive circuit 200 includes more than two control resistors, and the two ends of each control resistor constitute a group of input ends of the switch drive circuit 200. The two or more control resistors are electrically connected in sequence to form a control resistor branch, and the control resistor branch is connected to the drive switch circuit as a subcircuit of the drive switch circuit. Specifically, the cathode terminal of the first diode is electrically connected to the cathode terminal of the second diode through the control resistor branch. Furthermore, the control end of the bidirectional thyristor is electrically connected to the two ends of the control resistor branch to receive the opening and closing signal.

[0053] Furthermore, the thyristor optocoupler with zero-crossing detection adopts MOC3083 optocoupler, multiple (for example, three) MOC3083 optocouplers are connected in series, and multiple control resistors are connected in series for voltage division. It should be noted that the present application does not specifically limit the number of MOC3083 optocouplers and control resistors, and can be flexibly adjusted according to the actual situation of the power system for reactive power compensation as needed to achieve the voltage division effect and ensure work safety. Specifically: If the reverse cutoff withstand voltage of a single MOC3083 optocoupler output terminal can reach 800V, for safety reasons, five MOC3083s can be connected in series in a 1140V power network to achieve the purpose of safe and reliable triggering and operation. In addition, the voltage at both ends of the main electrode of the bidirectional thyristor 100 can be freely selected, and the input range is 220~1140VAC.

[0054] In a possible implementation, when there is a trigger current greater than 5 mA between the two ends of the light emitting diode 310 of the MOC3083 optocoupler, the light emitting diode 310 is lit to trigger the AC side circuit. The switching signal of the switching controller refers to the 12V DC signal output from its output end. In addition, Figure 1 As shown, there are three MOC3083 optocouplers and three control resistors. The circuit uses +12V voltage as the trigger signal of the thyristor. When the controller issues a start-up command, the +12V voltage is connected to the trigger circuit. Three MOC3083 optocouplers are connected in series, and the circuit on the side of the light-emitting diode 310 is connected in series with a 1KΩ / 1W voltage divider resistor. Due to its minimum trigger current, continuous conduction current, and forward voltage drop, we have:

[0055] I1=(12V-3×1.3) / (1000Ω)=8.1mA

[0056] The current complies with 5mA<8.1mA<60mA, which can drive the light emitting diode 310 to light up and is within its safe operating range.

[0057] In a possible implementation, the switching control circuit 300 further includes a voltage-dividing resistor, and the series starting end of the thyristor optocoupler with zero-crossing detection is electrically connected to the reactive power compensation controller through the voltage-dividing resistor.

[0058] In a possible implementation, when the triac 320 of the MOC3083 optocoupler is turned off, the grid voltage is instantly applied to both sides of the main electrode of the bidirectional thyristor 100. In order to prevent the du / dt (voltage rise rate) from being too high and triggering incorrectly, the present application connects an RC buffer circuit 400 in parallel at both ends of the main electrode of the bidirectional thyristor 100 to form a turn-off buffer circuit. That is, the zero-crossing trigger circuit of the bidirectional thyristor also includes the RC buffer circuit 400; the input end and the output end of the RC circuit are electrically connected to the two main electrodes of the bidirectional thyristor respectively.

[0059] Further, the RC buffer circuit 400 includes a buffer resistor and a capacitor connected in series, and the two ends of the RC buffer circuit 400 are electrically connected to the two main electrodes of the bidirectional thyristor. Further, the RC buffer circuit 400 includes more than two buffer resistors, and the two or more buffer resistors and the capacitor are connected in series to form the RC buffer circuit 400. Preferably, the RC circuit includes two buffer resistors (R4 and R5) and a capacitor (C1), and R4, R5 and C1 are connected in series in sequence to form the RC circuit.

[0060] In a possible implementation, the RC circuit includes a buffer resistor and two or more capacitors (power capacitors) connected in series, preferably including three power capacitors, which are connected in series with the buffer resistor, and can discharge the residual voltage of the power capacitor to a safe voltage within 60 seconds. Furthermore, a small light bulb is connected in parallel at both ends of one of the power capacitors, and the triggering of the bidirectional thyristor is judged by the on and off of the light bulb. Furthermore, the two ends of the main electrode of the bidirectional thyristor 100 are connected to 220V AC mains. Before the 12V DC voltage trigger signal is given, the bidirectional thyristor 100 is not turned on, there is no voltage at both ends of the power capacitor, and the small light bulb is not lit. When the 12V DC voltage trigger signal is given, when the trigger module detects the zero-crossing voltage, the bidirectional thyristor 100 is triggered and the small light bulb lights up.

[0061] According to another aspect of the present application, a zero-crossing trigger circuit board of a bidirectional thyristor is provided. The zero-crossing trigger circuit board of the bidirectional thyristor is provided with the aforementioned zero-crossing trigger circuit of the bidirectional thyristor.

[0062] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A zero-crossing trigger circuit of a bidirectional thyristor, characterized in that: include: Switching control circuit and switch driving circuit; The switch driving circuit comprises a first diode, a sixth resistor, a control resistor, a second diode and a seventh resistor, wherein the positive terminal of the first diode is electrically connected to a main electrode of the bidirectional thyristor as an output terminal of the switch driving circuit, the negative terminal of the first diode is electrically connected to the negative terminal of the second diode through the control resistor, the positive terminal of the second diode is electrically connected to the other main electrode of the bidirectional thyristor as another output terminal of the switch driving circuit, the two ends of the control resistor are both sides of an input terminal of the switch driving circuit, the sixth resistor is connected in parallel to the two ends of the first diode, and the seventh resistor is connected in parallel to the two ends of the second diode; The switching control circuit is suitable for detecting the zero-crossing point of the power system connected to the bidirectional thyristor, the input end of the switching control circuit is electrically connected to the reactive power compensation controller to receive the switching signal output by the controller, and the output end of the switching control circuit is electrically connected to the input end of the switch drive circuit, and is used to control the input end of the switch drive circuit to generate a switching signal for controlling the switching of the bidirectional thyristor when receiving the switching signal and detecting that the voltage of the power system crosses the zero point; The bidirectional thyristor is provided with a first thyristor and a second thyristor connected in reverse parallel, the control electrode of the first thyristor and the control electrode of the second thyristor are respectively electrically connected to the two sides of the input end of the switch drive circuit to receive the opening and closing signal, and the control electrode of the first thyristor is electrically connected to the side of the input end of the switch drive circuit close to the anode of the first thyristor.

2. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 1, characterized in that: The switching control circuit includes a thyristor optocoupler with zero-crossing detection, and the number of the thyristor optocouplers with zero-crossing detection is consistent with the number of input terminals of the switch drive circuit and is connected one-to-one; The input end of the thyristor optocoupler with zero-crossing detection is electrically connected to the reactive power compensation controller as the input end of the zero-crossing trigger circuit, and the output end of the thyristor optocoupler with zero-crossing detection is electrically connected to the corresponding input end in the switch drive circuit as the output end of the zero-crossing trigger circuit.

3. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 2, characterized in that: The zero-crossing trigger circuit includes at least two or more thyristor optocouplers with zero-crossing detection connected in series, wherein the series starting end of the thyristor optocouplers with zero-crossing detection is electrically connected to the reactive power compensation controller as the input end of the zero-crossing trigger circuit, and the output end of each thyristor optocoupler with zero-crossing detection is electrically connected to the corresponding input end of the switch drive circuit as an output end of the zero-crossing trigger circuit.

4. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 3, characterized in that: The switch driving circuit includes more than two control resistors, which are electrically connected in sequence to form a control resistor branch. The negative terminal of the first diode is electrically connected to the negative terminal of the second diode through the control resistor branch. The control end of the bidirectional thyristor is electrically connected to both ends of the control resistor branch for receiving the opening and closing signal.

5. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 3, characterized in that: The switching control circuit further comprises a voltage-dividing resistor, and the series starting end of the thyristor optocoupler with zero-crossing detection is electrically connected to the reactive power compensation controller through the voltage-dividing resistor.

6. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 1, characterized in that: Also includes: RC snubber circuit; The RC snubber circuit is electrically connected between two main electrodes of the bidirectional thyristor.

7. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 6, characterized in that: The RC snubber circuit includes a snubber resistor and a capacitor connected in series, and both ends of the RC snubber circuit are electrically connected to two main electrodes of the bidirectional thyristor.

8. The zero-crossing trigger circuit of the bidirectional thyristor according to claim 7, characterized in that: The RC buffer circuit includes more than two buffer resistors, and the more than two buffer resistors and the capacitor are connected in series to form an RC buffer circuit.

9. A zero-crossing trigger circuit board for a bidirectional thyristor, characterized in that: The zero-crossing trigger circuit board of the bidirectional thyristor is provided with the zero-crossing trigger circuit of the bidirectional thyristor as claimed in any one of claims 1 to 8.

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