Medium voltage ac voltage regulating device and control method

Abstract

The application provides a medium-voltage AC voltage regulating device and a control method, relates to the technical field of circuits, and the medium-voltage AC voltage regulating device comprises a transformer, at least one power conversion module, a main controller and at least one bypass module; the power conversion module comprises a first inverter bridge arm, a second inverter bridge arm, a third inverter bridge arm, a first inductor, a second inductor, a third inductor and a capacitor group. When the medium-voltage power grid voltage is too high or too low, the power conversion module is used for automatically compensating the power grid voltage, so that the power grid voltage is restored to the normal range. The medium-voltage AC voltage regulating device has a large regulating range, can effectively stabilize the medium-voltage power grid power supply voltage, has the effects of fast response speed, low cost, high reliability and convenient maintenance, and can effectively improve the power transmission capacity of the medium-voltage distribution network.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and more specifically, to a medium-voltage AC voltage regulating device and control method. Background Technology

[0002] In the operation of power systems, medium-voltage distribution lines serve as a crucial link connecting the power supply end and the power consumption end, and their voltage stability directly affects power supply quality and the safety of electrical equipment. With industrial development and the improvement of residents' living standards, industrial and residential electricity consumption has been growing rapidly year by year. However, the pace of upgrading and renovation of medium-voltage distribution lines in the power supply system has lagged behind, resulting in voltage at the end of the lines often falling below the allowable range specified by standards, and voltage fluctuations being significant. This problem is particularly pronounced during peak electricity consumption periods, which not only severely reduces power supply quality but, in extreme cases, can also cause non-lighting loads such as washing machines, air conditioners, and televisions to malfunction, and even cause irreversible damage to electrical equipment.

[0003] Existing medium-voltage line voltage regulation technology, which uses multi-winding transformers and multi-channel thyristor switching, suffers from drawbacks such as circuit complexity and high cost due to stepped voltage regulation, slow response speed of thyristor switches which cannot cope with rapid fluctuations in the power grid, short-term voltage drop during switching which affects stability, and overvoltage risk due to response lag when the power grid voltage rises rapidly. These drawbacks make it difficult to meet the requirements of medium-voltage lines for continuous, fast, stable and safe voltage regulation. Summary of the Invention

[0004] The purpose of this application is to provide a medium-voltage AC voltage regulating device and control method, which solves the above-mentioned problems existing in the prior art, simplifies the traditional complex multi-switch circuit structure, reduces hardware costs, and ultimately realizes the stability of medium-voltage line voltage within a preset range, improves power supply quality and the safety of electrical equipment, and adapts to the dynamic voltage regulation needs under the large-scale access of new energy.

[0005] In one aspect, a medium-voltage AC voltage regulating device is provided, which may include: a transformer, at least one power conversion module, a main controller and at least one bypass module;

[0006] The transformer is used to convert the input voltage to a voltage that is compatible with the operating voltage range of the power semiconductor devices in the power conversion module, and to provide electrical energy to the power conversion module; the transformer includes a first port and a second port;

[0007] Each power conversion module is used to adjust the voltage and current of the medium-voltage line in real time; each power conversion module includes a first input terminal, a second input terminal, an output terminal, and a communication port.

[0008] The main controller includes multiple control ports;

[0009] Any bypass module is used to form a current and voltage path when the power conversion module stops working, so as to enable the transformer to continuously transmit power to the load; each bypass module includes a first bypass port and a second bypass port; wherein, one power conversion module corresponds to one bypass module;

[0010] For any power conversion module, the first input terminal of the power conversion module is connected to the first port and the bypass first port of the corresponding bypass module, the second input terminal is connected to the second port; the communication port is connected to the control port; the output terminal is connected to the bypass second port; and the first port is also connected to the grid input terminal.

[0011] In one possible implementation, the power conversion module includes a first inverter bridge arm, a second inverter bridge arm, a third inverter bridge arm, a first inductor, a second inductor, a third inductor, and a capacitor bank.

[0012] The first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm constitute an inverter circuit;

[0013] The positive ends of the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are respectively connected to one end of the capacitor bank.

[0014] The negative terminals of the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are respectively connected to the other end of the capacitor bank.

[0015] The first inductor is used to filter the output current of the first inverter bridge arm; one end of the first inductor is connected to the first input terminal; the other end of the first inductor is connected to the midpoint of the first inverter bridge arm.

[0016] The second inductor is used to filter the output current of the second inverter bridge arm; one end of the second inductor is connected to the second input terminal, and the other end of the second inductor is connected to the midpoint of the second inverter bridge arm.

[0017] The third inductor is used to filter the output current of the third inverter bridge arm; one end of the third inductor is connected to the output terminal, and the other end of the third inductor is connected to the midpoint of the third inverter bridge arm.

[0018] The capacitor bank is used to provide DC support for the DC side voltage of the inverter circuit.

[0019] In one possible implementation, the inverter circuit is a three-level inverter circuit.

[0020] In one possible implementation, the capacitor bank consists of two sets of capacitors connected in series, and the voltage value at the midpoint of the connection formed by the two sets of capacitors connected in series constitutes the midpoint voltage of the power conversion module.

[0021] In one possible implementation, the transformer is an autotransformer or an isolation transformer.

[0022] In one possible implementation, the control port of the main controller is connected to the communication port of the power conversion module via an optical fiber, which provides electrical isolation during signal transmission.

[0023] In one possible implementation, the bypass module is composed of a mechanical switch or a bidirectional thyristor; the bidirectional thyristor is composed of two thyristors connected in parallel in opposite directions.

[0024] In one possible implementation, the bypass module consists of a mechanical switch and a bidirectional thyristor, wherein the mechanical switch and the bidirectional thyristor are connected in parallel to form a composite switch; the bidirectional thyristor consists of two thyristors connected in parallel in opposite directions.

[0025] In a second aspect, a control method for a medium-voltage AC voltage regulator is provided, applied to the medium-voltage AC voltage regulator of the first aspect. The medium-voltage AC voltage regulator includes: a transformer, at least one power conversion module, a main controller, and at least one bypass module; the power conversion module includes a first inverter arm, a second inverter arm, a third inverter arm, and a capacitor bank; the method includes:

[0026] When the medium-voltage AC voltage regulator is set to normal operating mode:

[0027] When the grid voltage is within the configured target preset voltage range, the bypass module is turned on, and the first inverter bridge arm and the second inverter bridge arm work to charge and discharge the capacitor bank, so that the total voltage of the capacitor bank is maintained within the DC voltage preset range; the third inverter bridge arm is not working.

[0028] When the grid voltage is lower than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm operate. The first inverter bridge arm outputs a first preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation. The second inverter bridge arm outputs an AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation, so as to maintain the total voltage of the capacitor bank within the DC voltage preset range. The third inverter bridge arm outputs a voltage in the same direction as the grid voltage. This voltage, together with the grid voltage and the first preset bridge arm AC voltage, forms the total output voltage, thereby raising the total output voltage to the target preset voltage range.

[0029] When the grid voltage is higher than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm and the second inverter bridge arm operate. The first inverter bridge arm outputs a second preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation. The second inverter bridge arm outputs an AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation, so as to maintain the total voltage of the capacitor bank within the DC voltage preset range. The third inverter bridge arm outputs a voltage in the opposite direction to the grid voltage. This voltage, together with the grid voltage and the second preset bridge arm AC voltage, forms the total output voltage, thereby reducing the total output voltage to the target preset voltage range.

[0030] When the medium-voltage AC voltage regulator is set to low-power operation mode and the grid voltage is within the target preset voltage range, the bypass module is turned on, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm stop working.

[0031] In one possible implementation, the bypass module includes a mechanical switch and a bidirectional thyristor;

[0032] After controlling the bidirectional thyristor to conduct, the mechanical switch is then controlled to conduct, thereby enabling the bypass module to conduct.

[0033] After the mechanical switch is turned off, the bidirectional thyristor is turned off to turn off the bypass module.

[0034] In one possible implementation, the main controller, while running a computer program, receives external instructions and acquires signals, and sends control instructions to the power conversion module and the bypass module.

[0035] The main controller receives feedback information from the power conversion module in response to the control command and provides the feedback information to external devices.

[0036] This application provides a medium-voltage AC voltage regulating device and control method. The device includes a transformer, at least one power conversion module, a main controller, and at least one bypass module. When the medium-voltage grid voltage is too high or too low, the power conversion module automatically compensates for the grid voltage, restoring it to the normal range. This device has a wide regulation range, effectively stabilizing the medium-voltage grid supply voltage. It features fast response, low cost, high reliability, and convenient maintenance, effectively improving the transmission capacity of the medium-voltage distribution network. This application relies on power electronic inverter technology to achieve efficient and economical real-time regulation of the line voltage. The voltage output stability is high, the response speed is fast, and it can quickly adapt to load fluctuations and grid voltage changes. Furthermore, the medium-voltage AC voltage regulating device has high overall reliability, requiring no frequent maintenance, reducing labor costs and downtime. In addition, the medium-voltage AC voltage regulating device has strong compatibility and can be easily extended to higher voltage level line scenarios, with a wide range of applications, providing strong support for flexible voltage regulation and stable operation of the medium-voltage grid. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of a medium-voltage AC voltage regulating device provided in an embodiment of this application;

[0039] Figure 2 This is an exemplary circuit diagram of a two-level power conversion module provided in an embodiment of this application;

[0040] Figure 3 This is an exemplary circuit diagram of a three-level power conversion module provided in an embodiment of this application;

[0041] Figure 4 An exemplary circuit diagram of the bypass module provided in the embodiments of this application. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0043] In the operation of power systems, medium-voltage distribution lines serve as a crucial link connecting the power supply end and the power consumption end, and their voltage stability directly affects power supply quality and the safety of electrical equipment. With industrial development and the improvement of residents' living standards, industrial and residential electricity consumption has been growing rapidly year by year. However, the pace of upgrading and renovation of medium-voltage distribution lines in the power supply system has lagged behind, resulting in voltage at the end of the lines often falling below the allowable range specified by standards, and voltage fluctuations being significant. This problem is particularly pronounced during peak electricity consumption periods, which not only severely reduces power supply quality but, in extreme cases, can also cause non-lighting loads such as washing machines, air conditioners, and televisions to malfunction, and even cause irreversible damage to electrical equipment.

[0044] To address the voltage regulation problem in medium-voltage lines, existing medium-voltage line voltage regulation technologies employing multi-winding transformers and multi-channel thyristor switching have several drawbacks. These include circuit complexity and high cost due to stepped voltage regulation, slow thyristor switching response speed which cannot cope with rapid grid fluctuations, short-term voltage drops during switching affecting stability, and overvoltage risks due to response lag when the grid voltage rises rapidly. Consequently, these technologies fail to meet the requirements of continuous, rapid, stable, and safe voltage regulation for medium-voltage lines.

[0045] Therefore, this application proposes to directly install a medium-voltage AC voltage regulating device on the power distribution network, which can automatically adjust the power supply voltage in real time to stabilize it at the standard value, improve the operational safety of the power supply transformer, significantly improve the stability of medium-voltage power supply, extend the effective power supply radius, increase the effective power supply capacity, reduce line energy consumption, and ensure the safety of electrical equipment.

[0046] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0047] Figure 1 This is a schematic diagram of a medium-voltage AC voltage regulating device provided in an embodiment of this application. Figure 1 As shown, the device may include: a transformer 1, at least one power conversion module 2, a main controller 3, and at least one bypass module 11;

[0048] Transformer 1 includes a first port and a second port; each power conversion module 2 includes a first input terminal L1, a second input terminal L2, an output terminal R, and a communication port CA; the main controller 3 includes a multi-channel control port, an external control port CTL, a main communication port CM, and a detection port; each bypass module 11 includes a bypass first port and a bypass second port; wherein, one power conversion module corresponds to one bypass module;

[0049] It should be noted that the output terminal R is also the output terminal of the medium-voltage AC voltage regulating device provided in this application. Figure 1 The diagram shows three power conversion modules; therefore, the output terminals of a medium-voltage AC voltage regulator include output terminal A2, output terminal B2, and output terminal C2.

[0050] A. Transformer 1 is used to convert the input voltage to a voltage that is compatible with the operating voltage range of the power semiconductor devices in the power conversion module, and to provide power to the power conversion module 2.

[0051] The first port of transformer 1 is connected to the grid input terminal and the first input terminal L1 of power conversion module 2, respectively; the second port of transformer 1 is connected to the second input terminal L2 of power conversion module 2.

[0052] Transformer 1 can be a single-phase transformer or a three-phase transformer; furthermore, transformer 1 can be configured as a three-phase autotransformer.

[0053] Transformer 1 can be a three-phase star connection. The three-phase power supply includes a first power input terminal A1, a second power input terminal B1 and a third power input terminal C1. Each power input terminal is connected to the middle lead of the corresponding winding of transformer 1 (that is, the first port of transformer 1).

[0054] Furthermore, continue to combine Figure 1 As shown, each winding in transformer 1 also includes a first lead and a last lead; the first lead of any winding (which serves as the second port of transformer 1) is connected to the second input terminal L2 of the corresponding power conversion module 2; the three last leads are interconnected, forming the midpoint of a star connection. The transformer converts the grid voltage input at its first port to a voltage suitable for the operating voltage range of the power semiconductor devices in the power conversion module, and provides electrical energy to the power conversion module; that is, transformer 1 can convert a high voltage of 10kV or 6kV to a lower voltage level to adapt to the operating voltage range of the power semiconductor devices in the power conversion module 2.

[0055] B. Each power conversion module 2 is used to adjust the voltage and current of the medium-voltage line in real time;

[0056] For any power conversion module 2, the first input terminal L1 of the power conversion module 2 is connected to the first port and the bypass first port of the corresponding bypass module, the second input terminal L2 is connected to the second port; the communication port CA is connected to the control port; and the output terminal R is connected to the bypass second port.

[0057] The communication port CA can be used to receive control commands from the main controller and return corresponding feedback information to the main controller.

[0058] The power conversion module 2 can achieve real-time voltage adjustment, stabilize the output voltage, and also has the function of power quality management.

[0059] C. Main controller 3 is used to control the power conversion module and bypass module, communicate with external devices, and detect system operating parameters and environmental parameters through control ports, main communication ports, and detection ports, so as to ensure the normal operation and voltage regulation function of the medium-voltage AC voltage regulator.

[0060] Each control port is connected to the corresponding power conversion module 2, and is used to send control commands to the power conversion module 2 and read its operating data. The control port can also output control commands to external control devices to realize connection and interaction with external control devices. The main communication port CM is used to establish a communication connection with the external controller to receive commands issued by the external controller and upload the corresponding feedback information to the external controller. The detection port is used to collect equipment operating parameters and environmental parameters such as voltage, current, temperature, smoke and arc light.

[0061] Furthermore, each control port of the main controller 3 is connected to the corresponding power conversion module 2 via optical fiber to achieve safe electrical isolation from the high-voltage circuit and to control and monitor the operating status of each power conversion module 2. The main communication port CM of the main controller 3 is used to communicate with external controllers, specifically including: receiving external commands and acquiring signals, and sending control commands to the power conversion module and bypass module. After that, the main controller receives feedback information from the power conversion module in response to the control commands and uploads the feedback information to the external device.

[0062] D. Any bypass module is used to form a current and voltage path when the power conversion module stops working, so as to enable the transformer to continuously transmit power to the load.

[0063] In some embodiments, combined with Figure 2 As shown, the power conversion module 2 may include a first inverter bridge arm, a second inverter bridge arm and a third inverter bridge arm, a first inductor 4, a second inductor 9, a third inductor 12 and a capacitor bank; further, the capacitor bank may be a set of capacitors 7.

[0064] Furthermore, the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm can be composed of a first power semiconductor device 5 and a second power semiconductor device 6 connected in series.

[0065] The first, second, and third inverter arms constitute an inverter circuit; this inverter circuit and other corresponding components constitute a three-arm inverter circuit 10; the positive terminals of the first, second, and third inverter arms are respectively connected to one end of capacitor 7; the negative terminals of the first, second, and third inverter arms are respectively connected to the other end of capacitor 7. The inverter circuit can be configured as a three-level inverter circuit.

[0066] The first inductor 4 is used to filter the output current of the first inverter bridge arm; one end of the first inductor 4 is connected to the first input terminal L1; this end of the first inductor 4 can also be understood as the first input terminal L1 of the power conversion module 2; the other end of the first inductor 4 is connected to the midpoint of the first inverter bridge arm.

[0067] The second inductor 9 is used to filter the output current of the second inverter bridge arm; one end of the second inductor 9 is connected to the second input terminal L2. Similarly, this end of the second inductor 9 can also be understood as the second input terminal L2 of the power conversion module 2; the other end of the second inductor 9 is connected to the midpoint of the second inverter bridge arm.

[0068] In some scenarios, the first inductor and the second inductor can be combined into a single inductor.

[0069] The third inductor 12 is used to filter the output current of the third inverter bridge arm; one end of the third inductor 12 is connected to the output terminal R, and the other end of the third inductor 12 is connected to the midpoint of the third inverter bridge arm.

[0070] Capacitor 7 is used to provide DC support for the DC side voltage of the inverter circuit; in practical applications, the midpoint voltage of capacitor 7 is the average value of the voltages at the positive and negative terminals of the capacitor.

[0071] In some embodiments, the capacitor bank can be two capacitor banks connected in series. In practical applications, when two capacitor banks are connected in series, the voltage value at the midpoint of the connection formed by the two capacitor banks connected in series can be used as the midpoint voltage of the power conversion module.

[0072] Furthermore, the first, second, and third inductors in this method function as a filter to filter out the output current and voltage harmonics of the power conversion module. In some embodiments, the filter can be implemented in various circuit ways, including LC circuits and LCL circuits, which are well known to those skilled in the art and are all within the scope of protection disclosed in this application.

[0073] Combination Figure 3As shown, the power conversion module 2 can also be configured as a three-level power conversion module; specifically, a diode-clamped three-level inverter circuit is adopted; for any inverter bridge arm, it is a three-level inverter bridge arm; in this embodiment, the second inverter bridge arm 13 is described, which may include four power semiconductor devices connected in series and two clamping diodes. The capacitor bank can be composed of two sets of capacitors connected in series.

[0074] It should be noted that the inverter circuit can also adopt three-level inverter circuits such as ANPC and flying capacitor type. In order to achieve higher voltage applications, the inverter circuit can also adopt four-level or five-level inverter circuits. Inverter circuits with different connection forms are known to those skilled in the art and are all within the scope of protection disclosed in this application.

[0075] Combination Figure 4 As shown, the bypass module 11 may include a mechanical switch 15 and a bidirectional thyristor. The mechanical switch 15 and the bidirectional thyristor are connected in parallel to form a composite switch. The bidirectional thyristor is composed of two thyristors 14 connected in opposite parallel configurations. When the bypass module 11 needs to be turned on, the bidirectional thyristor is triggered to turn on first, and then the mechanical switch 15 is controlled to turn on. When the bypass module 11 needs to be turned off, the mechanical switch 15 is controlled to turn off first, and then the triggering of the bidirectional thyristor is stopped to turn it off. Using a composite switch can avoid the arcing caused by the mechanical switch operation, thereby extending the service life of the switch. At the same time, it can also avoid the voltage drop loss caused by the long-term conduction of the bidirectional thyristor.

[0076] In addition, in different application scenarios, the bypass module 11 can also be composed of a single mechanical switch or a bidirectional thyristor, which can reduce the cost of the circuit corresponding to the bypass module 11.

[0077] This application provides a medium-voltage AC voltage regulator. The capacitors in this device can directly utilize non-polarized film capacitors, resulting in small DC capacitor capacity. This completely avoids the inherent defects of traditional large-capacity electrolytic capacitors, such as bulky size, short lifespan, and low long-term operational reliability, significantly reducing the overall size of the device, thereby extending the maintenance cycle and reducing the risk of failure. Furthermore, relying on power electronic inverter technology, the device achieves efficient and economical real-time regulation of the line voltage, with high voltage output stability and accuracy, fast response speed, and the ability to quickly adapt to load fluctuations and grid voltage changes. Additionally, the medium-voltage AC voltage regulator has high overall reliability, requiring no frequent maintenance, reducing labor costs and downtime. Moreover, the medium-voltage AC voltage regulator has strong compatibility and can be easily extended to higher voltage level line scenarios, with a wide range of applications, providing strong support for flexible voltage regulation and stable operation of medium-voltage power grids.

[0078] This application also provides a control method for a medium-voltage AC voltage regulator, applied to the aforementioned medium-voltage AC voltage regulator, the method including:

[0079] When the medium-voltage AC voltage regulator is set to normal operating mode:

[0080] Step S210: Obtain the grid voltage.

[0081] Specifically, the grid voltage of the medium-voltage line is collected in real time through the configured sensors, and the corresponding grid voltage is collected through the detection port, which is used as the basic input parameter for subsequent voltage regulation and control.

[0082] Step S220: Compare the grid voltage with the configured target preset voltage range to obtain the grid voltage status.

[0083] Specifically, the grid voltage is compared with the configured target preset voltage range to determine the grid voltage status:

[0084] The grid voltage status includes: A) the grid voltage is within the target preset voltage range; B) the grid voltage is below the target preset voltage range; C) the grid voltage is above the target preset voltage range.

[0085] Furthermore, for a power grid with a nominal voltage of 10kV, the target preset voltage range can be set to 93%~107% of the nominal voltage (i.e., the ±7% range specified by the standard). It can also be set according to actual needs.

[0086] Step S230: Determine the operating mode of the medium-voltage AC voltage regulator based on the state of the grid voltage.

[0087] Specifically, A. When the grid voltage is within the target preset voltage range, the bypass module is turned on, the first and second inverter bridge arms work, and the third inverter bridge arm stops working.

[0088] That is, after charging and discharging the capacitor bank through the first inverter bridge arm and the second inverter bridge arm, the total voltage of the capacitor bank is kept within the preset DC voltage range.

[0089] B. When the grid voltage is lower than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are activated.

[0090] The first inverter arm outputs a first preset AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation.

[0091] The second inverter bridge arm outputs an AC voltage with the midpoint voltage of the capacitor bank as a reference and the same frequency as the first port of the transformer through PWM modulation; by adjusting the phase and amplitude of this voltage, the charging and discharging current of the capacitor bank is adjusted so that the total voltage of the capacitor bank is kept within the preset DC voltage range.

[0092] The third inverter arm outputs a voltage in the same direction as the grid voltage. This voltage, together with the grid voltage and the AC voltage of the first preset bridge arm, forms the total output voltage, thereby raising the total output voltage to the target preset voltage range.

[0093] When the grid voltage is higher than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are activated.

[0094] The first inverter arm outputs a second preset AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation.

[0095] The second inverter bridge arm outputs an AC voltage with the midpoint voltage of the capacitor bank as a reference and the same frequency as the first port of the transformer through PWM modulation; by adjusting the phase and amplitude of this voltage, the charging and discharging current of the capacitor bank is adjusted so that the total voltage of the capacitor bank is kept within the preset DC voltage range.

[0096] The third inverter arm outputs a voltage in the opposite direction to the grid voltage. This voltage, together with the grid voltage and the AC voltage of the second preset bridge arm, forms the total output voltage, which reduces the total output voltage to the target preset voltage range.

[0097] When the medium-voltage AC voltage regulator is set to low-power operation mode and the grid voltage is within the target preset voltage range, the bypass module is turned on, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm stop working to reduce the power consumption of the device itself.

[0098] In some embodiments, when the bypass module includes a mechanical switch and a bidirectional thyristor, the mechanical switch is turned on after the bidirectional thyristor is turned on, thereby enabling the bypass module to conduct. When the bypass module includes a mechanical switch and a bidirectional thyristor, the bidirectional thyristor is turned off after the mechanical switch is turned off, thereby enabling the bypass module to turn off. This on / off sequence avoids electrical sparks generated when the mechanical switch is disconnected, thus extending the lifespan of the mechanical switch.

[0099] It should also be noted that the main controller runs a computer program and can accept external commands, such as output voltage settings, operating mode settings, shutdown, and startup commands. It can also collect signals, such as equipment temperature signals and output voltage signals. The main controller sends control commands to the power conversion module and bypass module, including startup, shutdown, bypass, and output voltage commands. At the same time, it receives feedback information from the power conversion module, including radiator temperature and DC voltage, and provides feedback information to external devices, including equipment operating status and operating voltage.

[0100] The control method provided in this application can dynamically switch operating modes based on the grid voltage status. When the voltage is within the target preset voltage range, the bypass module is turned on and some bridge arms are put into sleep mode, which can maintain the voltage stability of the capacitor bank and reduce ineffective energy consumption. When the voltage deviates from the target preset voltage range, all bridge arms are quickly activated to work together, and the superimposed voltage is precisely output through PWM modulation to achieve dynamic voltage rise or fall, ensuring that the total output voltage is stable within the target preset voltage range. The response speed is fast and the adjustment accuracy is high. In low power mode, when the grid voltage is normal, all inverter bridge arms are turned off, and only the bypass module is turned on, which significantly reduces the power consumption of the device itself and extends the equipment life. The modular bridge arm control logic and flexible voltage superposition strategy in this method can adapt to different voltage deviation scenarios, improve the applicability and reliability of the device in medium voltage lines, and provide strong support for the stable operation of the grid.

[0101] This application describes embodiments of methods, apparatus (systems), and computer program products according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0102] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0103] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0104] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected," "coupled," or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0105] Although preferred embodiments have been described in this application, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the embodiments in this application are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments in this application.

[0106] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations to the embodiments of this application fall within the scope of the embodiments of this application and their equivalents, then these modifications and variations are also intended to be included in the embodiments of this application.

Claims

1. A medium-voltage AC voltage regulating device, characterized in that, The device includes: a transformer, at least one power conversion module, a main controller, and at least one bypass module; The transformer is used to convert the input voltage to a voltage that is compatible with the operating voltage range of the power semiconductor devices in the power conversion module, and to provide electrical energy to the power conversion module; the transformer includes a first port and a second port; Each power conversion module is used to adjust the voltage and current of the medium-voltage line in real time; each power conversion module includes a first input terminal, a second input terminal, an output terminal, and a communication port. The main controller includes multiple control ports; Any bypass module is used to form a current and voltage path when the power conversion module stops working, so as to enable the transformer to continuously transmit power to the load; each bypass module includes a first bypass port and a second bypass port; wherein, one power conversion module corresponds to one bypass module; For any power conversion module, the first input terminal of the power conversion module is connected to the first port and the bypass first port of the corresponding bypass module, the second input terminal is connected to the second port; the communication port is connected to the control port; the output terminal is connected to the bypass second port; and the first port is also connected to the grid input terminal. The power conversion module includes a first inverter bridge arm, a second inverter bridge arm, a third inverter bridge arm, a first inductor, a second inductor, a third inductor, and a capacitor bank; The first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm constitute an inverter circuit; The positive ends of the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are respectively connected to one end of the capacitor bank. The negative terminals of the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are respectively connected to the other end of the capacitor bank. The first inductor is used to filter the output current of the first inverter bridge arm; one end of the first inductor is connected to the first input terminal; the other end of the first inductor is connected to the midpoint of the first inverter bridge arm. The second inductor is used to filter the output current of the second inverter bridge arm; one end of the second inductor is connected to the second input terminal, and the other end of the second inductor is connected to the midpoint of the second inverter bridge arm. The third inductor is used to filter the output current of the third inverter bridge arm; one end of the third inductor is connected to the output terminal, and the other end of the third inductor is connected to the midpoint of the third inverter bridge arm. The capacitor bank is used to provide DC support for the DC side voltage of the inverter circuit.

2. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The inverter circuit is a three-level inverter circuit.

3. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The capacitor bank consists of two sets of capacitors connected in series. The voltage value at the midpoint of the connection formed by the two sets of capacitors connected in series constitutes the midpoint voltage of the power conversion module.

4. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The transformer is an autotransformer or an isolation transformer.

5. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The control port of the main controller is connected to the communication port of the power conversion module via an optical fiber, which provides electrical isolation during signal transmission.

6. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The bypass module is composed of a mechanical switch or a bidirectional thyristor; the bidirectional thyristor is composed of two thyristors connected in parallel in opposite directions.

7. The medium-voltage AC voltage regulating device as described in claim 1, characterized in that, The bypass module consists of a mechanical switch and a bidirectional thyristor, which are connected in parallel to form a composite switch; the bidirectional thyristor consists of two thyristors connected in parallel in opposite directions.

8. A control method for a medium-voltage AC voltage regulating device, characterized in that, The method is applied to the medium-voltage AC voltage regulating device according to any one of claims 1-7, the medium-voltage AC voltage regulating device comprising: a transformer, at least one power conversion module, a main controller, and at least one bypass module; the power conversion module comprising a first inverter bridge arm, a second inverter bridge arm, a third inverter bridge arm, and a capacitor bank; the method comprising: When the medium-voltage AC voltage regulator is set to normal operating mode: When the grid voltage is within the configured target preset voltage range, the bypass module is turned on, and the first inverter bridge arm and the second inverter bridge arm work to charge and discharge the capacitor bank, so that the total voltage of the capacitor bank is maintained within the DC voltage preset range; the third inverter bridge arm is not working. When the grid voltage is lower than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm operate. The first inverter bridge arm outputs a first preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation. The second inverter bridge arm outputs an AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation, so as to maintain the total voltage of the capacitor bank within the DC voltage preset range. The third inverter bridge arm outputs a voltage in the same direction as the grid voltage. This voltage, together with the grid voltage and the first preset bridge arm AC voltage, forms the total output voltage, thereby raising the total output voltage to the target preset voltage range. When the grid voltage is higher than the target preset voltage range, the bypass module is turned off, and the first inverter bridge arm and the second inverter bridge arm operate. The first inverter bridge arm outputs a second preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation. The second inverter bridge arm outputs an AC voltage based on the midpoint voltage of the capacitor bank and at the same frequency as the first port of the transformer through PWM modulation, so as to maintain the total voltage of the capacitor bank within the DC voltage preset range. The third inverter bridge arm outputs a voltage in the opposite direction to the grid voltage. This voltage, together with the grid voltage and the second preset bridge arm AC voltage, forms the total output voltage, thereby reducing the total output voltage to the target preset voltage range. When the medium-voltage AC voltage regulator is set to low-power operation mode and the grid voltage is within the target preset voltage range, the bypass module is turned on, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm stop working.

9. The control method as described in claim 8, characterized in that, The bypass module includes a mechanical switch and a bidirectional thyristor; After controlling the bidirectional thyristor to conduct, the mechanical switch is then controlled to conduct, thereby enabling the bypass module to conduct. After the mechanical switch is turned off, the bidirectional thyristor is turned off to turn off the bypass module.

10. The control method according to claim 8, characterized in that, When the main controller is running the computer program, it receives external instructions and acquired signals, and sends control instructions to the power conversion module and the bypass module. The main controller receives feedback information from the power conversion module in response to the control command and provides the feedback information to external devices.

Images