Medium-voltage alternating-current voltage regulating device and control method

Abstract

The invention provides a medium-voltage alternating-current voltage regulating device and a control method, and relates to the technical field of circuits, and the medium-voltage alternating-current 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 bank. When the voltage of the medium-voltage power grid is too high or too low, the power conversion module automatically compensates the voltage of the power grid, so that the voltage is recovered to a normal range. The medium-voltage alternating-current voltage regulating device is large in regulating range, can effectively stabilize the power supply voltage of a medium-voltage power grid, has the effects of high response speed, low cost, high reliability and convenience in maintenance, and can effectively improve the power transmission capacity of the medium-voltage power distribution network.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit, in particular to a medium-voltage AC voltage regulating device and a control method. BACKGROUND

[0002] In the operation of power system, the medium-voltage distribution line as a key link connecting the power supply end and the power consumption end, its voltage stability directly affects the power supply quality and the safety of power consumption equipment. With the development of industry and the improvement of people's living standards, the industrial and domestic power consumption is increasing rapidly year by year, while the updating and reconstruction speed of the medium-voltage distribution line in the power supply system is relatively slow, resulting in that the voltage at the end of the line is often lower than the allowable range specified in the standard, and the voltage fluctuation range is large; especially during the peak period of power consumption, the above-mentioned contradiction is more prominent, which not only seriously reduces the power supply quality, but also causes irreversible damage to electrical equipment in extreme cases.

[0003] The existing medium-voltage line voltage regulating technology using multi-winding transformer combined with multi-path thyristor switching switch has the defects of complex circuit and high cost caused by step voltage regulation, slow response speed of thyristor switch which cannot cope with rapid fluctuations of power grid, short-time voltage drop during switching process affecting stability, and overvoltage risk caused by response lag when the voltage of power grid rises rapidly, etc., which is difficult to meet the demand of continuous, rapid, stable and safe voltage regulation of medium-voltage line. SUMMARY

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

[0005] In a first aspect, a medium-voltage AC voltage regulating device is provided, which can include 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 into a voltage suitable for the operating voltage range of the power semiconductor devices in the power conversion module, and provide power 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 end, a second input end, an output end and a communication port. The main controller includes a plurality of control ports. Any bypass module is used to form a current and voltage path to realize continuous power transmission from the transformer to the load when the power conversion module stops working; each bypass module includes a bypass first port and a bypass second port; wherein one power conversion module corresponds to one bypass module; For any power conversion module, the first input end of the power conversion module is connected with the first port and the bypass first port of the corresponding bypass module respectively, the second input end is connected with the second port; the communication port is connected with the control port; the output end is connected with the bypass second port; the first port is also connected with the grid input end.

[0006] In a 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 group; The first inverter bridge arm, the second inverter bridge arm and the third inverter bridge arm constitute an inverter circuit; The positive end of the first inverter bridge arm, the positive end of the second inverter bridge arm and the positive end of the third inverter bridge arm are respectively connected with one end of the capacitor group; The negative end of the first inverter bridge arm, the negative end of the second inverter bridge arm and the negative end of the third inverter bridge arm are respectively connected with the other end of the capacitor group; The first inductor is used to filter the output current of the first inverter bridge arm; one end of the first inductor is connected with the first input end; the other end of the first inductor is connected with 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 with the second input end, and the other end of the second inductor is connected with 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 with the output end, and the other end of the third inductor is connected with the midpoint of the third inverter bridge arm; The capacitor group is used to support the direct current side voltage of the inverter circuit.

[0007] In a possible implementation, the inverter circuit is a three-level inverter circuit.

[0008] In a possible implementation, the capacitor group is composed of two groups of capacitors in series, and the voltage value of the connection midpoint formed after the two groups of capacitors are connected in series constitutes the midpoint voltage of the power conversion module.

[0009] In a possible implementation, the transformer is a self-coupling transformer or an isolation transformer.

[0010] In a possible implementation, the control port of the main controller is connected with the communication port of the power conversion module through an optical fiber, and the optical fiber realizes electrical isolation while transmitting signals.

[0011] In a possible implementation, the bypass module is composed of a mechanical switch or a bidirectional thyristor; the bidirectional thyristor is composed of two forward and reverse parallel thyristors.

[0012] In a possible implementation, the bypass module is composed of a mechanical switch and a bidirectional thyristor, and the mechanical switch and the bidirectional thyristor are connected in parallel to form a composite switch; the bidirectional thyristor is composed of two forward and reverse parallel thyristors.

[0013] In a second aspect, a control method of a medium-voltage alternating-current voltage regulating device is provided, which is applied to the medium-voltage alternating-current voltage regulating device of the first aspect, and the medium-voltage alternating-current 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 and a capacitor bank; and the method comprises the following steps: When the medium-voltage alternating-current voltage regulating device is set to a normal working mode: When the grid voltage is in a configured target preset voltage range, the bypass module is turned on, the first inverter bridge arm and the second inverter bridge arm work, the capacitor bank is charged and discharged, and the total voltage of the capacitor bank is maintained in a direct-current voltage preset range; and the third inverter bridge arm does not work; When the grid voltage is lower than the target preset voltage range, the bypass module is turned off, the first inverter bridge arm, the second inverter bridge arm and the third inverter bridge arm work; the first inverter bridge arm is modulated by PWM, and outputs a first preset bridge arm alternating-current voltage which is based on the capacitor bank midpoint voltage and has the same frequency as the first port of the transformer; the second inverter bridge arm is modulated by PWM, and outputs an alternating-current voltage which is based on the capacitor bank midpoint voltage and has the same frequency as the first port of the transformer, so as to maintain the total voltage of the capacitor bank in the direct-current voltage preset range; and the third inverter bridge arm outputs a voltage which has the same direction as the grid voltage, and the voltage is superimposed with the grid voltage and the first preset bridge arm alternating-current voltage to form a total output voltage, so that the total output voltage is boosted 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 work; the first inverter bridge arm is modulated by PWM, and outputs a second preset bridge arm alternating current voltage which is referenced to the capacitor bank midpoint voltage and has the same frequency as the first port of the transformer; the second inverter bridge arm is modulated by PWM, and outputs an alternating current voltage which is referenced to the capacitor bank midpoint voltage and has the same frequency as the first port of the transformer, so as to maintain the total voltage of the capacitor bank within the preset range of the direct current voltage; the third inverter bridge arm outputs a voltage in the opposite direction of the grid voltage, and the voltage is superimposed with the grid voltage and the second preset bridge arm alternating current voltage to form a total output voltage, so that the total output voltage is reduced to the target preset voltage range. When the medium-voltage alternating current voltage regulating device is set to a low-power consumption working mode, and the grid voltage is in 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.

[0014] In a possible implementation, the bypass module comprises a mechanical switch and a bidirectional thyristor. After the bidirectional thyristor is controlled to be turned on, the mechanical switch is controlled to be turned on, so as to realize the turning on of the bypass module. After the mechanical switch is controlled to be turned off, the bidirectional thyristor is controlled to be turned off, so as to realize the turning off of the bypass module.

[0015] In a possible implementation, when the main controller runs a computer program, the main controller receives external instructions and acquires signals, and sends control instructions to the power conversion module and the bypass module. The main controller receives feedback information of the power conversion module for the control instructions, and provides the feedback information to an external device.

[0016] The application provides a medium-voltage AC voltage regulating device and a control method. The device comprises a transformer, at least one power conversion module, a main controller and at least one bypass module. When the voltage of the medium-voltage power grid is too high or too low, the power conversion module automatically compensates the voltage of the power grid to restore it to the normal range. The device has a large adjustment range, can effectively stabilize the power supply voltage of the medium-voltage power grid, 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. The application relies on power electronic inverter technology to realize efficient, economical and real-time regulation of line voltage, has high voltage output stability precision and fast response speed, can quickly adapt to load fluctuations and power grid voltage changes, the medium-voltage AC voltage regulating device has high overall reliability, does not need frequent maintenance, reduces labor cost and downtime, and has strong compatibility and can be easily expanded to be applied to higher voltage line scenarios, has a wide application range, and provides strong support for flexible voltage regulation and stable operation of the medium-voltage power grid. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed to be used in the embodiments of the application will be briefly introduced below. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 A structural schematic diagram of a medium-voltage AC voltage regulating device provided by the embodiments of the application is shown in the figure. Figure 2 An exemplary circuit diagram of a two-level power conversion module provided by the embodiments of the application is shown in the figure. Figure 3 An exemplary circuit diagram of a three-level power conversion module provided by the embodiments of the application is shown in the figure. Figure 4 An exemplary circuit diagram of a bypass module provided by the embodiments of the application is shown in the figure. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, and not all the embodiments. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the application.

[0020] In the operation of power system, as the key link connecting the power supply end and the power consumption end, the voltage stability of the medium voltage distribution line directly affects the power supply quality and the safety of the power consumption equipment. With the development of industry and the improvement of the living standard of residents, the industrial and civil power consumption increases rapidly year by year, while the updating and reconstruction speed of the medium voltage distribution line in the power supply system is relatively slow, which results in that the voltage at the end of the line is often lower than the allowable range specified in the standard, and the voltage fluctuation range is large. Especially during the peak period of power consumption, the above-mentioned contradiction is more prominent, which not only seriously reduces the power supply quality, but also causes the non-illumination load such as washing machine, air conditioner and television to be unable to work normally, and even causes irreversible damage to the electrical equipment.

[0021] In order to solve the voltage regulation problem of the medium voltage line, the existing medium voltage line voltage regulation technology adopts a multi-winding transformer cooperating with a multi-way thyristor switching switch. However, this technology has defects such as complex circuit and high cost caused by step voltage regulation, slow response speed of the thyristor switch which cannot cope with the rapid fluctuation of the power grid, short-time voltage drop in the switching process which affects the stability, and overvoltage risk caused by response lag when the voltage of the power grid rapidly rises, etc., which is difficult to meet the demand of continuous, rapid, stable and safe voltage regulation of the medium voltage line.

[0022] Therefore, the present application directly installs a medium voltage alternating current voltage regulating device on the power distribution network, which can automatically regulate the power supply voltage in real time, so as to stabilize it at the standard value, improve the operation safety of the power supply transformer, greatly improve the stability of the medium voltage power supply, prolong the effective power supply radius, increase the effective power supply capacity, reduce the line energy consumption, and protect the safety of the power consumption equipment.

[0023] The preferred embodiments of the present application are described below in combination with the drawings of the specification. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0024] Figure 1 A structure schematic diagram of a medium voltage alternating current voltage regulating device provided by the embodiments of the present application is shown in the figure. Figure 1 As shown in the figure, the device can include a transformer 1, at least one power conversion module 2, a main controller 3 and at least one bypass module 11. The transformer 1 includes a first port and a second port; each power conversion module 2 includes a first input end L1, a second input end L2, an output end R and a communication port CA; the main controller 3 includes a plurality of control ports, 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. It should be noted that the output end R is also the output end of the medium voltage alternating current voltage regulating device provided by the present application, Figure 1The medium shown is three power conversion modules, therefore, the output end of the medium voltage alternating current voltage regulating device includes output end A2, output end B2 and output end C2.

[0025] A, transformer 1, for converting the input voltage into a voltage suitable for the working voltage range of the power semiconductor devices in the power conversion module, and providing power to the power conversion module 2.

[0026] The first port of the transformer 1 is connected with the grid input end and the first input end L1 of the power conversion module 2 respectively; the second port of the transformer 1 is connected with the second input end L2 of the power conversion module 2.

[0027] The transformer 1 can be a single-phase transformer or a three-phase transformer; further, the transformer 1 can be set as a three-phase autotransformer.

[0028] The transformer 1 can be a three-phase star connection, and the three-phase power supply includes a first power input end A1, a second power input end B1 and a third power input end C1, each of which is connected to the middle lead-out end of the corresponding winding of the transformer 1 (i.e. the first port of the transformer 1).

[0029] Further, continue to combine Figure 1 As shown, each winding in the transformer 1 also includes a head lead-out end and a tail lead-out end; the head lead-out end of any winding (i.e. as the second port of the transformer 1) is connected with the second input end L2 of the corresponding power conversion module 2; the three tail lead-out ends are connected with each other to form the midpoint of the star connection. The transformer converts the grid voltage input from the first port into a voltage suitable for the working voltage range of the power semiconductor devices in the power conversion module, and provides power to the power conversion module; that is, the transformer 1 can convert high voltage of 10kV or 6kV into lower grade voltage to adapt to the working voltage range of the power semiconductor devices in the power conversion module 2.

[0030] B, each power conversion module 2 is used for real-time regulation of the voltage and current of the medium voltage line; For any power conversion module 2, the first input end L1 of the power conversion module 2 is connected with the first port and the bypass first port of the corresponding bypass module respectively, and the second input end L2 is connected with the second port; the communication port CA is connected with the control port; the output end R is connected with the bypass second port.

[0031] Among them, the communication port CA can be used to receive the control instruction of the main controller, and return the feedback information corresponding to the control instruction to the main controller.

[0032] The power conversion module 2 can realize real-time regulation of voltage, and can stabilize the output voltage, and also has the function of power quality management.

[0033] C. A main controller 3 is configured to control the power conversion module and the bypass module, communicate with external devices, and detect system operation parameters and environmental parameters through the control port, the main communication port, and the detection port, so as to ensure the normal operation and voltage regulation function of the medium-voltage AC voltage regulating device.

[0034] The control port is connected with the corresponding power conversion module 2, and is configured to send control instructions to the power conversion module 2 and read operation data of the power conversion module 2. The control port can also output control instructions to external control devices to realize connection and interaction with the external control devices. The main communication port CM is configured to establish a communication connection with an external controller, receive instructions issued by the external controller, and upload feedback information corresponding to the instructions to the external controller. The detection port is configured to collect device operation parameters and environmental parameters such as voltage, current, temperature, smoke, and arc light.

[0035] Further, the control ports of the main controller 3 are connected with the corresponding power conversion modules 2 through optical fibers to realize safe electrical isolation from the high-voltage circuit and control and monitoring of the working state of the power conversion modules 2. The main communication port CM of the main controller 3 is configured to communicate with an external controller, specifically including receiving external instructions and collecting signals, and sending control instructions to the power conversion module and the bypass module. Then, the main controller receives feedback information of the power conversion module in response to the control instructions, and uploads the feedback information to the external device.

[0036] D. Any bypass module is configured to form a current and voltage path when the power conversion module stops working, so as to realize continuous power transmission from the transformer to the load.

[0037] In some embodiments, in combination with Figure 2 As shown in the figure, the power conversion module 2 can 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 can be a group of capacitors 7.

[0038] Further, 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.

[0039] The first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm constitute an inverter circuit; the inverter circuit and corresponding other components constitute a three-bridge-arm inverter circuit 10; the positive terminal of the first inverter bridge arm, the positive terminal of the second inverter bridge arm, and the positive terminal of the third inverter bridge arm are respectively connected with one end of the capacitor 7; the negative terminal of the first inverter bridge arm, the negative terminal of the second inverter bridge arm, and the negative terminal of the third inverter bridge arm are respectively connected with the other end of the capacitor 7. The inverter circuit can be a three-level inverter circuit.

[0040] The first inductor 4 is configured 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. The one 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.

[0041] The second inductor 9 is configured 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, the one 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. In some scenarios, the first inductor and the second inductor can be combined into one inductor.

[0042] The third inductor 12 is configured 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. The other end of the third inductor 12 is connected to the midpoint of the third inverter bridge arm.

[0043] The capacitor 7 is configured to support the direct current voltage of the inverter circuit. In actual applications, the midpoint voltage of the capacitor 7 is the average of the positive and negative electrode voltages of the capacitor.

[0044] In some embodiments, the capacitor bank can be two capacitors connected in series. In actual applications, when the two capacitors are connected in series, the voltage value of the connection midpoint formed by the two capacitors connected in series can be taken as the midpoint voltage of the power conversion module.

[0045] Further, the first inductor, the second inductor and the third inductor in this mode realize the function of a filter, which is configured to filter the output current and voltage harmonics of the power conversion module. In some embodiments, the filter has multiple circuit implementation modes, which can specifically include LC circuit and LCL circuit, etc. All of them are well known to those skilled in the art and also belong to the range of protection disclosed in the present application.

[0046] In combination with Figure 3 As shown in the figure, the power conversion module 2 can also be configured as a three-level power conversion module. Specifically, a diode midpoint clamping type 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. The second inverter bridge arm 13 can include four power semiconductor devices connected in series and two clamping diodes. The capacitor bank can be composed of two capacitors connected in series.

[0047] It should be noted that the inverter circuit can also adopt ANPC, flying capacitor type and other three-level inverter circuits. In order to realize higher voltage application, the inverter circuit can also adopt four-level or five-level inverter circuit, etc. Different connection forms of inverter circuit are known to those skilled in the art and also belong to the protection range of the present application.

[0048] In combination Figure 4 As shown in the figure, the bypass module 11 can include a mechanical switch 15 and a bidirectional thyristor, and the mechanical switch 15 and the bidirectional thyristor are connected in parallel to form a composite switch. When the bypass module 11 needs to be turned on, the bidirectional thyristor is first triggered to be turned on, and then the mechanical switch 15 is controlled to be turned on. When the bypass module 11 needs to be turned off, the mechanical switch 15 is first controlled to be turned off, and then the bidirectional thyristor is stopped to be turned off. The composite switch can avoid the arc caused by the action of the mechanical switch, thereby prolonging the service life of the switch, and also avoiding the voltage drop loss caused by the long-term conduction of the bidirectional thyristor.

[0049] In addition, in different application scenarios, the bypass module 11 can also be composed of a single mechanical switch or a bidirectional thyristor. In this way, the corresponding circuit of the bypass module 11 can reduce the cost.

[0050] The medium-voltage alternating-current voltage regulating device provided by the present application can directly use a non-polarized film capacitor for the capacitor in the device, and the capacity of the direct-current capacitor is small, thereby completely avoiding the inherent defects of the traditional large-capacity electrolytic capacitor, such as large size, short service life, and low long-term operation reliability, greatly reducing the overall size of the device, thereby prolonging the operation and maintenance period and reducing the risk of failure. The device also relies on power electronic inverter technology to achieve efficient, economical and real-time regulation of line voltage, with high voltage output stability and precision and fast response speed, and can quickly adapt to load fluctuations and grid voltage changes. In addition, the medium-voltage alternating-current voltage regulating device has high overall reliability, does not need to be frequently maintained, reduces labor costs and downtime, and has strong compatibility and can be easily expanded to be applied to higher voltage line scenarios, thereby having a wide range of applications and providing strong support for flexible voltage regulation and stable operation of medium-voltage power grids.

[0051] The control method of the medium-voltage alternating-current voltage regulating device provided by the present application embodiment can be applied to the above-mentioned medium-voltage alternating-current voltage regulating device, and can include the following steps. When the medium-voltage alternating-current voltage regulating device is set to a normal working mode: Step S210, acquiring a grid voltage.

[0052] Specifically, the grid voltage of the medium-voltage line is acquired in real time through the configured sensor, and the corresponding grid voltage is acquired through the detection port, and the grid voltage is used as a basic input parameter for subsequent voltage regulation control.

[0053] Step S220: Compare the grid voltage with the configured target preset voltage range to obtain the state of the grid voltage.

[0054] Specifically, the grid voltage is compared with the configured target preset voltage range to determine the grid voltage status: The states of the grid voltage include: A. the grid voltage is within a target preset voltage range; B. the grid voltage is lower than the target preset voltage range; C. the grid voltage is higher than the target preset voltage range.

[0055] Furthermore, for a grid with a nominal voltage of 10 kV, the target preset voltage range can be set to 93% to 107% of the nominal voltage (i.e., the ±7% range specified by the standard). It can also be set according to actual needs.

[0056] Step S230: Determine the operating mode of the medium voltage AC voltage regulator based on the state of the grid voltage.

[0057] Specifically, A. when the grid voltage is within the target preset voltage range, the bypass module is turned on, the first inverter bridge arm and the second inverter bridge arm are in operation, and the third inverter bridge arm stops operating.

[0058] That is, after the capacitor bank is charged and discharged through the first inverter bridge arm and the second inverter bridge arm, the total voltage of the capacitor bank is maintained in a preset DC voltage range.

[0059] B. When the grid voltage is lower than the target preset voltage range, the bypass module is shut down, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are in operation; The first inverter bridge arm outputs a first preset bridge arm AC voltage with the same frequency as the first port of the transformer and based on the midpoint voltage of the capacitor bank through PWM modulation; The second inverter bridge arm uses PWM modulation to output an AC voltage with the same frequency as the first port of the transformer and based on the midpoint voltage of the capacitor bank. By adjusting the phase and amplitude of this voltage, the charging and discharging currents of the capacitor bank are regulated to keep the total voltage of the capacitor bank within the preset DC voltage range. The third inverter bridge arm outputs a voltage in the same direction as the grid voltage. This voltage is superimposed on the grid voltage and the first preset bridge arm AC voltage to form a total output voltage, so that the total output voltage is increased to within the target preset voltage range.

[0060] When the grid voltage is higher than the target preset voltage range, the bypass module is shut down, and the first inverter bridge arm, the second inverter bridge arm and the third inverter bridge arm are in operation; The first inverter bridge arm outputs a second preset bridge arm AC voltage with the same frequency as the first port of the transformer and based on the midpoint voltage of the capacitor bank through PWM modulation; The second inverter bridge arm outputs an AC voltage with the capacitor set midpoint voltage as a reference and the same frequency as the first port of the transformer. By adjusting the phase and amplitude of the voltage, the current of the capacitor set charging and discharging is adjusted, so that the total voltage of the capacitor set is maintained in a preset DC voltage range. The third inverter bridge arm outputs a voltage in the opposite direction of the grid voltage. The voltage is superimposed with the grid voltage and the second preset bridge arm AC voltage to form a total output voltage, so that the total output voltage is reduced to the target preset voltage range.

[0061] When the medium-voltage AC voltage regulator is set to a low-power working mode and the grid voltage is in 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, so as to reduce the power consumption of the device itself.

[0062] In some embodiments, when the bypass module includes a mechanical switch and a bidirectional thyristor, after the bidirectional thyristor is turned on, the mechanical switch is controlled to be turned on to realize the turn-on of the bypass module. When the bypass module includes a mechanical switch and a bidirectional thyristor, after the mechanical switch is turned off, the bidirectional thyristor is controlled to be turned off to realize the turn-off of the bypass module. In this way, the working sequence of turn-on and turn-off can avoid the electric spark generated by the mechanical switch breaking, thereby prolonging the service life of the mechanical switch.

[0063] It should be further noted that the main controller runs a computer program, can accept external instructions, such as output voltage settings, working mode settings, corresponding external instructions such as shutdown, startup, etc., and can also collect signals such as device temperature signal collection, output voltage signal collection, etc. The main controller sends control instructions to the power conversion module and the bypass module, including startup, shutdown, bypass, output voltage, etc., while receiving feedback information from the power conversion module, including radiator temperature, DC voltage, etc., and providing feedback information to external devices, including device operating status, working voltage, etc.

[0064] The control method provided in the present application can dynamically switch the working mode based on the grid voltage state. When the voltage is in the target preset voltage range, the bypass module is turned on and part of the bridge arms are in a dormant state, which can not only maintain the stability of the capacitor set voltage, but also reduce the invalid power consumption. When the voltage deviates from the target preset voltage range, the full bridge arms are quickly started to work cooperatively, and the superimposed voltage is accurately output through PWM modulation, so as to realize the dynamic lifting or lowering of the voltage and ensure that the total output voltage is stable in the target preset voltage range, with fast response speed and high regulation accuracy. In the low-power mode, all inverter bridge arms are turned off when the grid voltage is normal, and only the bypass module is turned on, which significantly reduces the power consumption of the device itself and prolongs the service life of the device. The modular bridge arm control logic and the flexible voltage superposition strategy in the method adapt to different voltage deviation scenarios, improve the applicability and reliability of the device in the medium-voltage line, and provide strong support for stable operation of the grid.

[0065] The embodiments of the present application are described with reference to the flowchart and / or block diagram of the method, device (system) and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as a combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a device implemented in the flowchart and / or block diagram. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the function specified in the flow or flows and / or block or blocks.

[0066] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including instruction apparatus, which implements the flowchart and / or block diagram. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the function specified in the flow or flows and / or block or blocks.

[0067] These computer program instructions can also be loaded into a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a process for implementing the flowchart and / or block diagram. Figure 1 one or more flows and / or blocks Figure 1 an apparatus that implements the function specified in the flow or flows and / or block or blocks.

[0068] Unless otherwise defined, technical terms or scientific terms used in the present application should be understood as the common meaning understood by a person having ordinary skill in the art to which the present application belongs. The terms "first", "second" and similar words used in the present application do not represent any order, number or importance, but are only used to distinguish different components. "Include" or "contain" and similar words mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects. "Connect", "couple" or "connect" and similar words are not limited to physical or mechanical connection, but can include electrical connection, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to represent relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0069] While the preferred embodiments in the application have been described, additional modifications and changes can occur to those skilled in the art once they learn of the basic creative principles contained herein. Therefore, the present embodiments are to be regarded as including all modifications and variations that fall within the scope of the present embodiments.

[0070] Obviously, numerous modifications and variations of the embodiments in the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the embodiments in the present application, the embodiments can be practiced otherwise than as specifically described.

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 into a voltage that is adapted to the operating voltage range of the power semiconductor device in the power conversion module and provide electric 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, used to form a current and voltage path when the power conversion module stops working, so as to achieve continuous power transmission from the transformer 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 end of the power conversion module is respectively connected to the first port and the bypass first port of the corresponding bypass module, and the second input end is connected to the second port; the communication port is connected to the control port; the output end is connected to the bypass second port; and the first port is also connected to the grid input end.

2. The medium voltage AC voltage regulating device according to claim 1, characterized in that: 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 end of the first inverter bridge arm, the positive end of the second inverter bridge arm, and the positive end of the third inverter bridge arm are respectively connected to one end of the capacitor bank; The negative end of the first inverter bridge arm, the negative end of the second inverter bridge arm, and the negative end of 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 end; 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 end, 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 end, 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.

3. The medium voltage AC voltage regulating device according to claim 2, characterized in that: The inverter circuit is a three-level inverter circuit.

4. The medium voltage AC voltage regulating device according to claim 2, characterized in that: The capacitor group is composed of two groups of capacitors connected in series, and the voltage value of the connection midpoint formed by the two groups of capacitors connected in series constitutes the midpoint voltage of the power conversion module.

5. The medium voltage AC voltage regulating device according to claim 1, characterized in that: The transformer is an autotransformer or an isolation transformer.

6. The medium voltage AC voltage regulating device according to 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, and the optical fiber realizes electrical isolation while transmitting signals.

7. The medium voltage AC voltage regulating device according to 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 forward and reverse directions.

8. The medium voltage AC voltage regulating device according to claim 1, characterized in that: The bypass module is composed of a mechanical switch and a bidirectional thyristor. The mechanical switch and the bidirectional thyristor are connected in parallel to form a composite switch. The bidirectional thyristor is composed of two thyristors connected in parallel in forward and reverse directions.

9. A control method for a medium voltage AC voltage regulator, characterized in that: The medium voltage AC voltage regulating device according to any one of claims 1 to 8 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, and a capacitor bank; the method comprises: When setting the medium voltage AC voltage regulator to normal working mode: When the grid voltage is within the configured target preset voltage range, the bypass module is turned on, the first inverter bridge arm and the second inverter bridge arm operate 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 does not operate; When the grid voltage is lower than the target preset voltage range, the bypass module is shut down, and the first inverter bridge arm, the second inverter bridge arm, and the third inverter bridge arm are in operation; the first inverter bridge arm outputs a first preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and 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 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 preset DC voltage range; the third inverter bridge arm outputs a voltage in the same direction as the grid voltage, which is superimposed with the grid voltage and the first preset bridge arm AC voltage to form a total output voltage, so that the total output voltage is increased to within the target preset voltage range; When the grid voltage is higher than the target preset voltage range, the bypass module is shut down, and the first inverter bridge arm and the second inverter bridge arm are in operation; the first inverter bridge arm outputs a second preset bridge arm AC voltage based on the midpoint voltage of the capacitor bank and 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 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 preset DC voltage range; the third inverter bridge arm outputs a voltage in the opposite direction to the grid voltage, which is superimposed with the grid voltage and the second preset bridge arm AC voltage to form a total output voltage, so that the total output voltage is reduced to within the target preset voltage range; When the medium voltage AC voltage regulating device is set to a low power consumption working mode and the grid voltage is within a 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.

10. The control method according to claim 9, wherein: The bypass module includes a mechanical switch and a bidirectional thyristor; After controlling the bidirectional thyristor to be turned on, controlling the mechanical switch to be turned on to achieve the conduction of the bypass module; After controlling the mechanical switch to turn off, controlling the bidirectional thyristor to turn off, so as to realize the shutoff of the bypass module.

11. The control method according to claim 9, characterized in that: When the main controller runs the computer program, it receives external instructions and acquisition 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 instruction, and provides the feedback information to an external device.

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