Optical fiber serial communication control system for chained SVG (static var generator)

Abstract

The utility model relates to the technical field of communication, in particular to an optical fiber serial communication control system for a chained SVG (static var generator), which comprises a display and 3 * n chain links which are respectively in communication connection with an SVG main controller, n is greater than or equal to 2, every n chain links form a group, each group of chain links are connected in parallel on the SVG main controller, the chain links in each group are connected in series, and the display is connected with the display. The last chain links of each group are connected in parallel, each group of chain links is connected with a power grid through a reactor, and the SVG main controller comprises at least two optical fiber transmitting ports and receiving ports. A traditional parallel communication mode that each power unit is connected with an SVG controller through two optical fibers is improved into optical fiber serial communication, and due to the fact that the voltage difference between unit modules at the two ends of each optical fiber is smaller than 1000 V, the optical fibers hardly generate induced voltage caused by the electromagnetic induction phenomenon.

Description

Technical Field

[0001] The utility model relates to the field of communication technologies, and particularly to an optical fiber serial communication control system for a chain-type SVG. Background Technique

[0002] The statements in this part only provide background technical information related to the utility model, and do not necessarily constitute prior art.

[0003] A chain-type static var generator (SVG, Static Var Generator) is a device used to improve the stability and power quality of a power system. It can track load changes in real time, dynamically and continuously smooth the compensation of reactive power, improve the system power factor, manage harmonics in real time, compensate negative sequence current, and improve the power supply quality of the power grid. The SVG is connected to the power grid through a reactor or directly in parallel by a self-commutating bridge circuit, and adjusts the phase and amplitude of the output voltage on the AC side of the bridge circuit, or directly controls the current on its AC side, so that the circuit absorbs or emits reactive power that meets the requirements to achieve the purpose of dynamic reactive power compensation.

[0004] Each phase in the main circuit of the chain-type SVG is formed by cascading multiple chain links (or called power units). Each chain link has a chain link controller and an inverter circuit. The chain link controller controls the inverter circuit to output reactive power and harmonic signals by receiving the command signal from the SVG main controller. Since the SVG chain link is in a high-voltage circuit, in order to achieve electrical isolation between the low-voltage of the SVG main controller and the high-voltage of the chain, communication between the SVG main controller and each chain link controller is carried out through optical fiber connection.

[0005] Up to now, the optical fiber connection method between the SVG main controller and the chain link usually uses two optical fibers for parallel communication. For example, in the prior art 201220303246.2, one optical fiber is used to transmit the PWM signal and control signal required by the chain link, and the other optical fiber is used to upload the working state information, fault information, DC bus voltage, unit temperature, etc. of the chain link.

[0006] Under the above communication method, the required number of optical fibers is twice the number of connections, and the number of optical fiber interfaces of the SVG main controller is equal to the number of optical fibers. With the increase of the voltage level (above 35 kV) and the number of chain links, the number of optical fiber interfaces on the SVG main controller increases exponentially, making it impossible to expand. At the same time, it causes an increase in the number of optical fibers and different lengths of optical fibers, increasing the cost and wiring difficulty of the product, making the on-site installation and maintenance more difficult. At the same time, in this communication method, due to the potential difference between each chain link being affected by the system voltage, high voltage may be induced on the optical fiber, which may cause the risk of discharge and electric shock, affecting the operation reliability of the SVG. Summary of the Utility Model

[0007] To solve the technical problems existing in the above-mentioned background art, the present utility model provides an optical fiber serial communication control system for a chain-type SVG, which improves the parallel communication form in which each traditional power unit is connected to the SVG controller via two optical fibers into optical fiber serial communication.

[0008] To achieve the above object, the present utility model adopts the following technical solutions:

[0009] The present utility model provides an optical fiber serial communication control system for a chain-type SVG, including a display and 3*n links respectively communicating with an SVG main controller, where n≥2. Every n links form a group, and each group of links is connected in parallel to the SVG main controller. Each link within each group of links is connected in series, and the last link of each group of links is connected in parallel to the last link of the other groups. Each group of links is connected to the power grid through a reactor. The SVG main controller includes at least 2 optical fiber transmitting ports and receiving ports.

[0010] Further, there is a communication connection between the optical fiber transmitting port of the SVG main controller and the optical fiber receiving port of the first link in each group of links.

[0011] Further, within each group of links, there is a communication connection between the optical fiber transmitting port and the optical fiber receiving port of adjacent two links.

[0012] Further, within each group of links, there is a communication connection between the transmitting optical fiber port of the last link and the receiving port of the SVG main controller.

[0013] Further, there is a communication connection between the last link within each group of links and the last link within the next group of links.

[0014] Further, each link has a link control circuit, and the link control circuit has 2 optical fiber receiving ports and 2 optical fiber transmitting ports. The optical fiber receiving port receives the control signal from the transmitting port of the SVG main controller, and the optical fiber transmitting port is used to forward the control signal of the SVG main controller and the information of this link to the next link.

[0015] Further, each link has an inverter circuit, and the inverter circuit is an H-bridge converter formed by capacitors, resistors and fully controlled electronic devices.

[0016] Further, the power devices of the inverter circuit are at least one or more of insulated gate bipolar transistors IGBTs, integrated gate-commutated thyristors IGCTs or power MOSFETs.

[0017] Further, all the links are cascaded into a star or delta main circuit.

[0018] Furthermore, communication connections are achieved between the links through optical fibers, and the optical fibers are plastic optical fibers or quartz optical fibers.

[0019] Compared with the prior art, the above one or more technical solutions have the following beneficial effects:

[0020] 1. The traditional parallel communication form in which each power unit is connected to the SVG controller through two optical fibers is improved to optical fiber serial communication. Since the voltage difference between the unit modules at both ends of the optical fiber is less than 1000V, the optical fiber hardly generates induced voltage caused by electromagnetic induction, improving the reliability and safety of the SVG.

[0021] 2. The design of the control system interface is simplified, and the control system has good scalability. The voltage level of the device can be extended only by connecting the links in series to each phase; the number of optical fiber ports of the SVG main controller and the number of optical fibers used are greatly reduced, reducing the equipment cost, and at the same time significantly improving the production and installation and maintenance efficiency, and the effect is more obvious in the chain-type SVG with a higher voltage level. Description of the Drawings

[0022] The attached drawings forming a part of this utility model are used to provide a further understanding of this utility model. The schematic embodiments and descriptions thereof of this utility model are used to explain this utility model and do not constitute an improper limitation of this utility model.

[0023] Figure 1 is a schematic diagram of the principle of the optical fiber serial communication control system for SVG provided by this utility model;

[0024] Figure 2 is a schematic diagram of the principle of the link circuit provided by this utility model. Detailed Embodiments

[0025] The following further describes this utility model in conjunction with the drawings and embodiments.

[0026] It should be noted that the following detailed descriptions are all exemplary and are intended to provide a further description of this utility model. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this utility model belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to this utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] As introduced in the background art, the optical fiber connection method between the SVG main controller and the link usually adopts two optical fibers for connection, with a parallel communication method. One optical fiber is used to transmit the PWM signal and control signal required by the link, and the other optical fiber is used to upload the working state information, fault information, DC bus voltage, unit temperature, etc. of the link. The number of optical fibers in this method is twice the number of connections. With the increase of the voltage level (above 35 kV) and the increase of the number of links, the number of optical fiber interfaces on the SVG main controller increases exponentially, making it impossible to expand. The lengths of the optical fibers are different, increasing the cost of the product and the wiring difficulty, and also increasing the difficulty of on-site installation and maintenance. The potential difference between each link is affected by the system voltage, and high voltage may be induced on the optical fiber, which may cause the risk of discharge and electric shock, affecting the operation reliability of the SVG.

[0029] Therefore, the following embodiments provide an optical fiber serial communication control system for a chain-type SVG, which improves the traditional parallel communication form in which each power unit is connected to the SVG controller through two optical fibers to optical fiber serial communication.

[0030] As Figure 1 shown, an optical fiber serial communication control system for a chain-type SVG includes a display and 3*n links (n≥2) that are respectively communicatively connected to the SVG main controller; every n links form a group, and each group of links is connected in parallel to the SVG main controller. Each link within each group is connected in series, and the last links of each group are connected in parallel. Each group of links is connected to the power grid through a reactor.

[0031] The optical fiber receiving port of the first link in each group is communicatively connected to the optical fiber transmitting port of the SVG main controller for receiving the control instructions of the SVG main controller.

[0032] Each group of links is connected in parallel to the SVG main controller. Each link within each group is connected in series, and the last links of each group are connected in parallel, for sending the collected operating state information of the current link and the reconstructed control signal of the SVG main controller to the next link.

[0033] The transmitting optical fiber port of the last link in each group is communicatively connected to the optical fiber receiving port of the SVG main controller for transmitting the operating state information of the current link and the operating state information of all links to the SVG main controller.

[0034] The display shows a human-machine interface for displaying the working state of the SVG and the setting operation of the SVG operating parameters, and adopts the RS485 communication method with the SVG main controller.

[0035] The SVG main controller is used for the calculation of SVG control signals and the control of links. There are more than 2 optical fiber transmitting ports and receiving ports on the SVG main controller.

[0036] The optical fiber communication loop includes: the optical fiber communication connection between the optical fiber transmitting port of the SVG main controller and the optical fiber receiving port of the first link, the optical fiber communication connection between the optical fiber transmitting ports and receiving ports of adjacent two links, and the optical fiber communication connection between the transmitting optical fiber port of the last link and the receiving port of the SVG main controller. Modbus communication protocol is used for data transmission between the SVG main controller and the links and between each link.

[0037] The link control circuit is used to decode and reconstruct the received control instruction optical signal of the SVG main controller, and convert it into the drive control signal required by the inverter circuit. At the same time, the operating state information of this link collected and the control signal of the reconstructed SVG main controller are sent to the control circuit of the second link;

[0038] The control circuit of the second link receives the control instruction optical signal from the first link, decodes and reconstructs it, and converts it into the drive control signal required by the inverter circuit. At the same time, the operating state information of this link collected, the operating state information of the first link, and the control signal of the reconstructed SVG main controller are sent to the control circuit of the third link;

[0039] And so on, the control circuit of the last link transmits the operating state information of this link collected and the operating state information of all links to the SVG main controller through optical fiber.

[0040] In this embodiment, the communication optical fiber adopts plastic optical fiber or quartz optical fiber.

[0041] As Figure 2 shown, each link includes a link control circuit and an inverter circuit. The link control circuit contains 2 optical fiber receiving ports (r1, r2) and 2 optical fiber transmitting ports (t1, t2). The optical fiber receiving ports are used to receive the control signals from the transmitting ports of the SVG main controller, and the optical fiber transmitting ports are used to forward the control signals of the SVG main controller and the information of this link to the next link. The control chip of the link control circuit adopts a field programmable gate array (FPGA) to complete the control of the link.

[0042] The inverter circuit is an H-bridge converter composed of capacitors C, resistors R, and fully controlled electronic devices T1, T2, T3, and T4, which receives the drive signal of the link control circuit and completes the AC-DC power conversion.

[0043] The link inverter circuit adopts a modular design. The power devices used are an inverter circuit composed of insulated gate bipolar transistors (IGBTs), integrated gate-commutated thyristors (IGCTs), or power MOSFETs. Multiple links are cascaded into a star or delta main circuit and connected to the power grid through a connecting reactor for energy conversion.

[0044] In this embodiment, the fully controlled electronic devices T1 - T4 can be triodes. The inverter circuit includes a capacitor C, a resistor R, a triode T1, and a triode T3 connected in parallel. The triode T2 is connected in series with the triode T1, and the triode T4 is connected in series with the triode T3.

[0045] This embodiment changes the traditional parallel communication form where each power unit is connected to the SVG controller via two optical fibers, and instead uses optical fiber serial communication. Since the voltage difference between the unit modules at both ends of the optical fiber is less than 1000V, the optical fiber hardly generates induced voltage caused by electromagnetic induction, improving the reliability and safety of the SVG.

[0046] The design of the control system interface is simplified, and the control system has good scalability. The equipment voltage level can be extended by simply connecting the links in series to each phase. This significantly reduces the number of optical fiber ports and the amount of optical fiber used in the SVG main controller, reducing equipment costs. At the same time, it significantly improves the production, installation, and maintenance efficiency, and the effect is more obvious in the chain - type SVG with a higher voltage level.

[0047] As Figure 1 shown, the SVG main controller shown has 6 (tza, txa, tzb, txb, tzc, txc) optical fiber transmitting ports and 6 (rza, rxa, rzb, rxb, rzc, rxc) optical fiber receiving ports, and each link shown has 2 optical fiber transmitting ports and 2 optical fiber receiving ports.

[0048] Taking link A1 as an example, it includes two optical fiber receiving ports, ra1 and rxa, and two optical fiber transmitting ports, ta1 and txa.

[0049] Taking the communication loop of the A - phase link as an example, the optical fiber of the A - phase link communication loop includes:

[0050] The optical fiber connecting the optical fiber transmitting ports (tza, txa) of the SVG main controller to the optical fiber receiving ports (ra1, rxa) of link A1, whose function is to send the control signal and set parameter values of the main controller to link A1;

[0051] The optical fiber connecting the optical fiber transmitting ports (ta1, txa) of link A1 to the optical fiber receiving ports (ra2, rxa) of link A2, whose function is to forward the control signal, set parameter values of the SVG main controller, and upload the working state information of link A1 to link A2;

[0052] The optical fiber that connects the optical fiber emission ports (ta2, txa) of link A2 to the optical fiber reception ports (ra3, rxa) of link A3 is used to forward the control signals of the SVG main controller, set parameter values, and upload the working status information of links A1 and A2 to link A3;

[0053] And so on until the last link An of phase A. The optical fiber that connects the optical fiber emission ports (tan, txa) of link An to the optical fiber reception ports (rza, rxa) of the SVG main controller is used to upload the working status information of links A1, A2, A3... An to the SVG main controller;

[0054] The SVG main controller judges the operation conditions of each link according to the received signals, and at the same time sends the information to the human-machine interface for display.

[0055] Taking the SVG of the 10kV star main circuit as an example, each phase of the SVG consists of 12 links. According to the traditional parallel communication technology, each link uses 2 optical fibers to connect to the SVG main controller. The SVG main controller needs to design 36 optical fiber reception ports and 36 optical fiber emission ports, and 72 optical fibers with different lengths need to be manufactured for the whole machine; after adopting this solution, the SVG main controller only needs to design 6 optical fiber reception ports and 6 optical fiber emission ports, and only 12 optical fibers with different lengths and 66 short optical fibers with equal lengths (short optical fibers for communication between adjacent power units) need to be manufactured for the whole machine. In actual design and application, the optical fiber between the optical fiber emission port (tan) of link An and the optical fiber reception port (rza) of the SVG main controller can be omitted, and only 9 optical fibers with different lengths need to be manufactured for the whole machine.

[0056] The communication working principle of this embodiment is described in detail below:

[0057] As Figure 1 shown, taking the phase A communication loop as an example, it includes 2 communication loops. The two communication loops work in parallel, and the FPGA control chip is used to complete the operation of the program. The working principles of each loop are described separately below:

[0058] The optical fiber emission port (tza) of the SVG main controller sends the normalized phase A command signal and synchronization signal to the optical fiber reception port (ra1) of link A1 through the optical fiber;

[0059] Link A1 decodes the received command signal and synchronization signal, and at the same time sends the reconstructed command signal and synchronization signal to the optical fiber reception port (ra2) of link A2 through the optical fiber emission port (ta1) of link A1;

[0060] Link A2 decodes the received command signal and synchronization signal, and at the same time sends the reconstructed command signal and synchronization signal to the optical fiber receiving port (ra3) of link A3 through the optical fiber of the optical fiber transmitting port (ta2) of link A2;

[0061] And so on until the last link An. Link An decodes the received command signal and synchronization signal, and at the same time sends the reconstructed command signal and synchronization signal to the optical fiber receiving port rza of the SVG main controller through the optical fiber of the optical fiber transmitting port (tan) of link An, so that after the SVG main controller sends the phase A command signal and synchronization signal each time, links A1, A2, A3... An can quickly receive the command signal and synchronization signal issued by the SVG controller.

[0062] The optical fiber transmitting port (txa) of the SVG main controller sends the switching frequency, the number of links, and the protection parameters to the optical fiber receiving port (rxa) of link A1;

[0063] Link A1 decodes the received switching frequency, the number of links, and the protection parameters, and at the same time sends the reconstructed switching frequency, the number of links, the protection parameters, and the working information of link A1 to the optical fiber receiving port (rxa) of link A2 through the optical fiber of the optical fiber transmitting port (txa) of link A1;

[0064] Link A2 decodes the received switching frequency, the number of links, and the protection parameters, and at the same time sends the reconstructed switching frequency, the number of links, the protection parameters, and the working information of links A1 and A2 to the optical fiber receiving port (rxa) of link A3 through the optical fiber of the optical fiber transmitting port (txa) of link A2;

[0065] And so on until the last link An. Link An decodes the received command signal and synchronization signal, and at the same time sends the reconstructed command signal and synchronization signal and the working information of links A1, A2, A3... An to the optical fiber receiving port rxa of the SVG main controller through the optical fiber of the optical fiber transmitting port (txa) of link An, so that after the SVG main controller sends the switching frequency, the number of links, and the protection parameters each time, links A1, A2, A3... An can quickly receive the switching frequency, the number of links, and the protection parameters issued by the SVG controller. At the same time, the SVG main controller receives the working information of each link and uploads the working information of the link to the human-machine interface.

[0066] The above two communication loops realize the communication control function between the SVG main controller and each link, and solve the problems mentioned in the background technology.

[0067] The working information of each uploaded link includes the unit DC bus voltage, unit temperature, auxiliary power supply voltage, and various protection fault information. The traditional parallel communication form in which each power unit is connected to the SVG controller via two optical fibers is improved to fiber serial communication. Since the voltage difference between the unit modules at both ends of the optical fiber is less than 1000V, the induced voltage caused by electromagnetic induction hardly occurs in the optical fiber, improving the reliability and safety of the SVG.

[0068] The design of the control system interface is simplified, and the control system has good scalability. The voltage level of the device can be extended only by connecting the links in series to each phase; the number of optical fiber ports of the SVG main controller and the number of optical fibers used are significantly reduced, reducing the equipment cost. At the same time, the production and installation and maintenance efficiency are significantly improved, and the effect is more obvious in the chain-type SVG with a higher voltage level.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An optical fiber serial communication control system for chained SVG, characterized in that: The invention comprises a display and 3*n chain links respectively connected to the SVG main controller for communication, n≥2, each n chain links form a group, each group of chain links is connected in parallel to the SVG main controller, each chain link in each group of chain links is connected in series, the last chain link in each group of chain links is connected in parallel with the last chain link in other groups, each group of chain links is connected to the power grid through a reactor, and the SVG main controller comprises at least 2 optical fiber transmitting ports and receiving ports.

2. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: The optical fiber transmitting port of the SVG main controller is communicatively connected with the optical fiber receiving port of the first link in each group of links.

3. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: In each group of chain links, the optical fiber transmitting ports and the optical fiber receiving ports of two adjacent chain links are communicatively connected.

4. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: In each group of chain links, the transmitting optical fiber port of the last chain link is communicatively connected with the receiving port of the SVG main controller.

5. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: The last link in each group of links is in communication connection with the last link in the next group of links.

6. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: Each link has a link control circuit, which has two fiber optic receiving ports and two fiber optic transmitting ports. The fiber optic receiving port receives the control signal from the transmitting port of the SVG main controller, and the fiber optic transmitting port is used to forward the control signal of the SVG main controller and the information of the current link to the next link.

7. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: Each link has an inverter circuit, which is an H-bridge converter formed by capacitors, resistors and fully controlled electronic devices.

8. The optical fiber serial communication control system for chained SVG according to claim 7, characterized in that: The power device of the inverter circuit is at least one or more of an insulated gate bipolar transistor IGBT, an integrated gate commutated thyristor IGCT or a power MOSFET.

9. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: All chain links are cascaded to form a star or delta main circuit.

10. The optical fiber serial communication control system for chained SVG according to claim 1, characterized in that: The chain links are connected to each other by optical fiber, which is plastic optical fiber or quartz optical fiber.

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