Flexible interconnection device based on alternating current and direct current hybrid magnetic flux control and control method

Abstract

The invention relates to a flexible interconnection device based on alternating current and direct current hybrid magnetic flux control and a control method. The flexible interconnection device based on alternating-current and direct-current hybrid magnetic flux control comprises a direct-current magnetic flux control module and an alternating-current magnetic flux control module, and the target magnetic flux control module is used for controlling the transmission of the active power between the first transformer area and the second transformer area according to the phase angle difference between the transmission signal of the first transformer area and the transmission signal of the second transformer area and the transmission direction of the active power between the first transformer area and the second transformer area. The target magnetic flux control module comprises an alternating current magnetic flux control module and / or a direct current magnetic flux control module. According to the method, the alternating-current magnetic flux control module and the direct-current magnetic flux control module are combined, so that power transmission in a full-phase-angle range can be ensured under the condition of ensuring low manufacturing cost.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic equipment, and in particular to a flexible interconnection device and control method based on AC / DC hybrid flux control. Background Art

[0002] The high proportion of distributed renewable energy generation increases the volatility of sources and loads in distribution networks. Simultaneously, the large number of precision manufacturing-related production equipment places new demands on the quality of the supplied power. Distributed energy sources are often physically distant from one another, leading to significant temporal fluctuations in load across different substations and transmission lines. Consequently, flexible interconnection technologies that directly transmit active power between multiple substations are attracting attention.

[0003] In traditional technologies, flexible interconnection devices include unified power flow controller (UPFC) technology, which has certain requirements on the voltage amplitude and phase angle difference of the transmission signal between two substations, and cannot achieve power transmission within the full phase angle range. Summary of the Invention

[0004] Based on this, it is necessary to provide a flexible interconnection device and control method based on AC / DC hybrid flux control that can achieve power transmission within the full phase angle range to address the above technical problems.

[0005] In a first aspect, the present application provides a flexible interconnection device based on AC / DC hybrid magnetic flux control, comprising:

[0006] The input end of the DC magnetic flux control module is connected to the output end of the transmission line of the first substation in the power grid structure, and the output end of the DC magnetic flux control module is connected to the input end of the transmission line of the second substation in the power grid structure; the input end of the AC magnetic flux control module is connected to the output end of the transmission line of the first substation, and the output end of the AC magnetic flux control module is connected to the input end of the transmission line of the second substation;

[0007] The target flux control module is used to control the transmission of active power between the first station area and the second station area based on the phase angle difference between the transmission signal of the first station area and the transmission signal of the second station area, and the transmission direction of the active power between the first station area and the second station area. The target flux control module includes: an AC flux control module and / or a DC flux control module.

[0008] In one embodiment, the AC flux control module includes: a step-down transformer, a back-to-back converter, and a single-phase transformer;

[0009] The step-down transformer is used for converting a first alternating voltage output by a transmission line of a first substation into a second alternating voltage, and transmitting the second alternating voltage to the back-to-back converter; the voltage value of the first alternating voltage is higher than that of the second alternating voltage.

[0010] The back-to-back converter is used for converting the second alternating voltage into direct current, and transmitting the converted second alternating voltage to the single-phase transformer.

[0011] The single-phase transformer is used for converting the converted second alternating voltage into a third alternating voltage, and transmitting the third alternating voltage to a transmission line of a second substation; the voltage value of the second direct current is lower than that of the third direct current.

[0012] In one embodiment, the back-to-back converter comprises a first inverter, a capacitor and a second inverter.

[0013] The first inverter is used for converting the second alternating voltage output by the step-down transformer into a fourth direct current.

[0014] The capacitor is used for filtering the fourth direct current output by the first inverter to obtain a filtered fourth direct current, and transmitting the filtered fourth direct current to the second inverter.

[0015] The second inverter is used for converting the filtered fourth direct current into the third alternating voltage, and transmitting the third alternating voltage to an input end of the single-phase transformer.

[0016] In one embodiment, the direct current magnetic flux control module further comprises a first switch device.

[0017] An input end of the first switch device is connected to an output end of the back-to-back converter, and an output end of the first switch device is connected to an input end of the single-phase transformer.

[0018] The first switch device is used for controlling the on-off state of the alternating current magnetic flux control module.

[0019] In one embodiment, the direct current magnetic flux control module comprises a controllable reactor.

[0020] In one embodiment, the direct current magnetic flux control module further comprises a second switch device.

[0021] An input end of the second switch device is connected to an output end of the controllable reactor, and an output end of the second switch device is connected to the transmission line of the second substation.

[0022] The second switch device is used for controlling the on-off state of the direct current magnetic flux control module.

[0023] In a second aspect, the present application further provides a control method for a flexible interconnection device, which is applied to the flexible interconnection device based on AC / DC hybrid flux control according to the first aspect, comprising:

[0024] Obtaining the transmission direction of active power between a first substation and a second substation in the power grid structure, and a phase angle difference between a transmission voltage of the first substation and a transmission voltage of the second substation;

[0025] Determine the active power transmission strategy based on the transmission direction and phase angle difference;

[0026] According to the active power transmission strategy, the active power is transmitted between the first substation area and the second substation area.

[0027] In one embodiment, the above-mentioned determination of the active power transmission strategy based on the transmission direction and the phase angle difference includes:

[0028] If the transmission direction is forward transmission, determining a first transmission strategy of active power according to a relationship between the phase angle difference and the rated phase angle difference;

[0029] If the transmission direction is reverse transmission, the second transmission strategy of the active power is determined according to the relationship between the phase angle difference and the rated phase angle difference.

[0030] In one embodiment, when the transmission direction is forward transmission, the second transmission strategy for determining the active power based on the relationship between the phase angle difference and the rated phase angle difference includes:

[0031] If the phase angle difference is less than the rated phase angle difference, the AC flux control module and the DC flux control module in the flexible interconnection device jointly transmit active power;

[0032] If the phase angle difference is greater than the rated phase angle difference, the DC flux control module transmits active power.

[0033] In one embodiment, when the transmission direction is reverse transmission, the second transmission strategy for determining the active power based on the relationship between the phase angle difference and the rated phase angle difference includes:

[0034] If the phase angle difference is less than the rated phase angle difference, the AC flux control module in the flexible interconnection device transmits active power;

[0035] If the phase angle difference is greater than the rated phase angle difference, the flexible interconnection device does not transmit active power.

[0036] The flexible interconnection device and the control method based on the AC-DC hybrid magnetic flux control have the advantages that a new flexible interconnection device is provided, the AC magnetic flux control module and the DC magnetic flux control module are combined, the power transmission in the full phase angle range is ensured, and the manufacturing cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed to be used in the description of the embodiments of the present application or the related art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other related drawings can be obtained by those skilled in the art without creative labor.

[0038] Figure 1 An application environment diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in an embodiment;

[0039] Figure 2 A structural schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in an embodiment;

[0040] Figure 3 A structural schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0041] Figure 4 A structural schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0042] Figure 5 A structural schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0043] Figure 6 A structural schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0044] Figure 7 An equivalent circuit diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in an embodiment;

[0045] Figure 8 A control method schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in an embodiment;

[0046] Figure 9 A control method schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0047] Figure 10 A control method schematic diagram of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in another embodiment;

[0048] Figure 11 Basic control block diagram of the flexible interconnection device based on AC-DC hybrid flux control in one embodiment;

[0049] Figure 12 Control method schematic diagram of the flexible interconnection device based on AC-DC hybrid flux control in another embodiment;

[0050] Figure 13 Power transmission capacity schematic diagram corresponding to the control method of the flexible interconnection device based on AC-DC hybrid flux control in one embodiment;

[0051] Figure 14 Simulation model schematic diagram of the flexible interconnection device based on AC-DC hybrid flux control in one embodiment;

[0052] Figure 15 Grid-connected current waveform schematic diagram of the AC flux control module in one embodiment;

[0053] Figure 16 Current waveform schematic diagram of the DC flux control module in one embodiment;

[0054] Figure 17 Simulation result schematic diagram of the flexible interconnection device based on AC-DC hybrid flux control in one embodiment.

[0055] Explanation of reference signs:

[0056] 01-grid system; 10-first substation;

[0057] 20-flexible interconnection device; 30-second substation;

[0058] 201-flux control module; 202-AC flux control module;

[0059] 2021-voltage reduction transformer; 2022-back-to-back converter;

[0060] 2023-single-phase transformer; 20221-first inverter;

[0061] 20222-capacitor; 20223-second inverter;

[0062] 2024-first switching device; 2011-controllable reactor;

[0063] 2012-second switching device. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0065] The high proportion of distributed renewable energy generation increases the volatility of sources and loads in distribution networks. Simultaneously, the large number of precision manufacturing-related production equipment places new demands on the quality of the supplied power. Distributed energy sources are often physically distant from one another, leading to significant temporal fluctuations in load across different substations and transmission lines. Consequently, flexible interconnection technologies that directly transmit active power between multiple substations are attracting attention.

[0066] Traditionally, flexible interconnection devices, including power electronic transformers based on switching power supply technology and modular multilevel converters (MMCs), have been used to effectively interconnect two substations. However, these devices require a large number of high-voltage switching devices and capacitors, resulting in high costs and unreliable reliability. This application aims to provide a novel flexible interconnection device that addresses the high costs and unreliable reliability of traditional flexible interconnection devices.

[0067] After introducing the background technology of the flexible interconnection device based on AC / DC hybrid magnetic flux control provided by the embodiment of the present application, the following briefly describes the implementation environment involved in the flexible interconnection device based on AC / DC hybrid magnetic flux control provided by the embodiment of the present application. The flexible interconnection device based on AC / DC hybrid magnetic flux control provided by the embodiment of the present application can be applied to Figure 1 In the power grid system 01 shown, the power grid system 01 includes a first substation 10, a flexible interconnection device 20 based on AC / DC hybrid flux control, and a second substation 30. A substation refers to a power supply area centered on a distribution transformer. The flexible interconnection device 20 based on AC / DC hybrid flux control is connected to the first substation 10 and the second substation 30, respectively. The flexible interconnection device 20 based on AC / DC hybrid flux control is used to achieve on-demand distribution of active power between the first substation 10 and the second substation 30.

[0068] Those skilled in the art will understand that Figure 1 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the application environment to which the solution of the present application is applied. The specific application environment may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0069] After introducing the application scenarios of the flexible interconnection device 20 based on AC / DC hybrid magnetic flux control provided by the embodiment of the present application, the flexible interconnection device 20 based on AC / DC hybrid magnetic flux control described in the present application is introduced in detail below. Figure 2 As shown, the flexible interconnection device 20 based on AC / DC hybrid magnetic flux control includes: a DC magnetic flux control module 201 and an AC magnetic flux control module 202;

[0070] The input end of the DC flux control module 201 is connected to the output end of the transmission line of the first substation 10 in the power grid structure, and the output end of the DC flux control module 201 is connected to the input end of the transmission line of the second substation 20 in the power grid structure; the input end of the AC flux control module 202 is connected to the output end of the transmission line of the first substation 10, and the output end of the AC flux control module 202 is connected to the input end of the transmission line of the second substation 20;

[0071] The target flux control module is used to control the transmission of active power between the first station area 10 and the second station area 20 based on the phase angle difference between the transmission signal of the first station area 10 and the transmission signal of the second station area 20, and the transmission direction of the active power between the first station area 10 and the second station area 20. The target flux control module includes: an AC flux control module 202 and / or a DC flux control module 201.

[0072] The AC flux control module 202 is used to transmit active power between the first area 10 and the second area 20 in the reverse direction, and the phase angle difference between the transmission signal of the first area 10 and the transmission signal of the second area 20 is Less than the rated phase angle difference In the case of , the active power between the first station area 10 and the second station area 20 is transmitted separately. In addition, the AC flux control module 202 is also used to transmit the active power between the first station area 10 and the second station area 20 in the forward direction, and the phase angle difference between the transmission signal of the first station area 10 and the transmission signal of the second station area 20 is Less than the rated phase angle difference In this case, the active power between the first section 10 and the second section 20 is transmitted together with the DC flux control module 201 .

[0073] It should be noted that forward transmission means that the value of the active power transmitted from the first substation 10 to the second substation 20 is greater than 0, or the value of the active power transmitted from the second substation 20 to the first substation 10 is less than 0; reverse transmission means that the value of the active power transmitted from the first substation 10 to the second substation 20 is less than 0, or the value of the active power transmitted from the second substation 20 to the first substation 10 is greater than 0.

[0074] The DC flux control module 201 is used to transmit active power between the first station area 10 and the second station area 20 in the forward direction, and the phase angle difference between the transmission signal of the first station area 10 and the transmission signal of the second station area 20 is Greater than the rated phase angle difference In the case of , the active power between the first station area 10 and the second station area 20 is transmitted separately. In addition, the DC flux control module 201 is also used to transmit the active power between the first station area 10 and the second station area 20 in the forward direction, and the phase angle difference between the transmission signal of the first station area 10 and the transmission signal of the second station area 20 is Less than the rated phase angle difference In this case, the active power between the first section 10 and the second section 20 is transmitted together with the AC flux control module 202 .

[0075] The power transmission principle of the flexible interconnection device based on AC / DC hybrid magnetic flux control provided by this application will be described below. Assuming that an active power of 2Pe (greater than 0) is transmitted between the first substation 10 and the second substation 30 via the flexible interconnection device 20 based on AC / DC hybrid magnetic flux control, the following four situations exist:

[0076] (1) Phase angle difference between the transmission signal in the first station area 10 and the transmission signal in the second station area 30 At the rated phase angle difference Within the range, the AC flux control module 202 and the DC flux control module 201 jointly transmit an active power of 2Pe;

[0077] (2) The phase angle difference between the transmission signal in the first station area 10 and the transmission signal in the second station area 30 Rated phase angle difference When , the active power transmitted by the AC flux control module 202 and the DC flux control module 201 is Pe;

[0078] (3) The phase angle difference between the transmission signal in the first station area 10 and the transmission signal in the second station area 30 Greater than the rated phase angle difference When , the DC flux control module 201 transmits active power alone;

[0079] (4) Phase angle difference between the transmission signal in the first station area 10 and the transmission signal in the second station area 30 When the angle is greater than 90°, both the AC flux control module 202 and the DC flux control module 201 do not transmit active power.

[0080] In this embodiment, a new flexible interconnection device based on AC / DC hybrid flux control is provided. This new flexible interconnection device based on AC / DC hybrid flux control combines an AC flux control module and a DC flux control module to ensure power transmission within the full phase angle range while ensuring low manufacturing costs.

[0081] In one embodiment, see Figure 3 , the AC flux control module 202 includes: a step-down transformer 2021, a back-to-back converter 2022, and a single-phase transformer 2023;

[0082] The step-down transformer 2021 is used to convert the first AC voltage output by the transmission line of the first substation 10 into a second AC voltage, and transmit the second AC voltage to the back-to-back converter 2022; the voltage value of the first AC voltage is higher than the voltage value of the second AC voltage;

[0083] The back-to-back converter 2022 is configured to convert the second AC voltage into DC and transmit the converted second AC voltage to the single-phase transformer 2023;

[0084] The single-phase transformer 2023 is used to convert the converted second AC voltage into a third AC voltage and transmit the third AC voltage to the transmission line of the second station area 30; the voltage value of the second DC voltage is lower than the voltage value of the third DC voltage.

[0085] It should be noted that the back-to-back converter 2022 serves as the AC flux control portion of the AC flux control module 202. The input end of the back-to-back converter 2022 is connected to the step-down transformer 2021 and then connected in parallel to the three-phase power grid of the first substation 10. The output end of the back-to-back converter 2022 is connected to three single-phase transformers 2023 and then connected in series to the transmission line between the first substation 10 and the second substation 30.

[0086] In one embodiment, see Figure 4 The back-to-back converter 2022 includes a first inverter 20221, a capacitor 20222 and a second inverter 20223;

[0087] The first inverter 20221 is configured to convert the second AC voltage output by the step-down transformer 2021 into a fourth DC voltage;

[0088] The capacitor 20222 is configured to filter the fourth DC voltage output by the first inverter 20221 to obtain a filtered fourth DC voltage, and transmit the filtered fourth DC voltage to the second inverter 20223;

[0089] The second inverter 20223 is configured to convert the filtered fourth DC voltage into a third AC voltage, and transmit the third AC voltage to the input end of the single-phase transformer 2023 .

[0090] In one embodiment, see Figure 5 , the AC magnetic flux control module 202 further includes: a first switching device 2024;

[0091] An input end of the first switching device 2024 is connected to an output end of the back-to-back converter 2022 , and an output end of the first switching device 2024 is connected to an input end of the single-phase transformer 2023 ;

[0092] The first switch device 2024 is used to control the on / off state of the AC magnetic flux control module 202 .

[0093] In one embodiment, see Figure 6 The DC flux control module 201 further includes: a controllable reactor 2011 .

[0094] It should be noted that the controllable reactor 2011 serves as the DC flux control part in the DC flux control module 201 .

[0095] In one embodiment, see Figure 6 , the DC flux control module 201 further includes: a second switching device 2012;

[0096] The input end of the second switch device 2012 is connected to the output end of the controllable reactor 2011 , and the output end of the second switch device 2012 is connected to the transmission line of the second substation 30 ;

[0097] The second switch device 2012 is used to control the on / off state of the DC flux control module 201 .

[0098] In one embodiment, an equivalent circuit diagram of the flexible interconnection device 20 based on AC / DC hybrid magnetic flux control is also provided. That is, the output end of the AC magnetic flux control module 202 is equivalent to a voltage source, and the equivalent circuit diagram can be obtained. Figure 7 In the equivalent model shown in Figure 1, the transmission line of the system is simplified to a pure inductor.

[0099] Please continue to see Figure 7 , when there is only AC flux control module 202, the receiving end area (i.e. Figure 7 middle ) The expressions of active and reactive power received are shown in the following formulas (1) and (2):

[0100]

[0101]

[0102] in, is the voltage amplitude of the first station 10, is the voltage amplitude of the second stage 30, is the phase angle difference between the two stations, is the output reactance of the series unit, and is the voltage amplitude and phase angle of the series unit. The AC flux control module 202 can control and The power transmission effect of the DC flux control module 201 branch directly connected in parallel between two substations depends only on the voltage amplitude and phase angle difference of the substations, which can be obtained by writing the circuit equation.

[0103] The total power expression of the flexible interconnection device 20 based on AC / DC hybrid flux control is shown in the following formula (3) and formula (4):

[0104]

[0105]

[0106] in, When the AC flux control module 202 is switched off due to overvoltage protection (ie, V3 = 0), the flexible interconnection device 20 based on AC / DC hybrid flux control can still achieve a certain range of power flow control through the reactance value of the DC flux control module 201.

[0107] Based on the same inventive concept, embodiments of the present application also provide a method for implementing the aforementioned flexible interconnect device based on AC / DC hybrid magnetic flux control. The solution provided by this method is similar to the solution described in the aforementioned device. Therefore, the specific limitations in the following embodiments of the control method for one or more flexible interconnect devices based on AC / DC hybrid magnetic flux control can be found in the above-mentioned limitations on flexible interconnect devices based on AC / DC hybrid magnetic flux control, and will not be further elaborated here.

[0108] In an exemplary embodiment, Figure 8 As shown, a control method for a flexible interconnection device based on AC / DC hybrid magnetic flux control is provided, which is applied to the flexible interconnection device based on AC / DC hybrid magnetic flux control described in each of the above embodiments, including:

[0109] S201: Acquire the transmission direction of active power between a first substation area and a second substation area in a power grid structure, and the phase angle difference between the transmission voltage of the first substation area and the transmission voltage of the second substation area.

[0110] In the embodiment, before determining the transmission strategy of the active power, the transmission direction of the active power between the first substation and the second substation in the power grid structure and the phase angle difference between the transmission signal of the first substation and the transmission signal of the second substation can be acquired.

[0111] S202, determine the transmission strategy of the active power according to the transmission direction and the phase angle difference.

[0112] In the embodiment, after acquiring the transmission direction of the active power between the first substation and the second substation in the power grid structure and the phase angle difference between the first substation and the second substation, the transmission strategy of the active power can be determined according to the size relationship between the phase angle difference and the rated phase angle difference and the transmission direction of the active power. and the rated phase angle difference and the transmission direction of the active power.

[0113] It should be noted that the transmission direction is different, and the transmission strategy of the active power determined according to the size relationship between the phase angle difference and the rated phase angle difference and the rated phase angle difference is different.

[0114] S203, transmit the active power between the first substation and the second substation according to the transmission strategy of the active power.

[0115] In the embodiment, after determining the transmission strategy of the active power, the active power between the first substation and the second substation is transmitted according to the transmission strategy of the active power.

[0116] In the embodiment, by providing a novel control method corresponding to a flexible interconnection device based on AC-DC hybrid magnetic flux control, the control method can control the switching of the AC magnetic flux control module and the DC magnetic flux control module, thereby ensuring power transmission in the full phase angle range while ensuring low manufacturing cost.

[0117] In one exemplary embodiment, the determination method of the transmission strategy of the active power can also be described in detail, as shown in Figure 9 S202, determine the transmission strategy of the active power according to the transmission direction and the phase angle difference.

[0118] S301, if the transmission direction is forward transmission, determine the first transmission strategy of the active power according to the relationship between the phase angle difference and the rated phase angle difference.

[0119] In the embodiment, in the case that the transmission direction of the active power between the first substation and the second substation is forward transmission, the first transmission strategy of the active power can be determined according to the relationship between the phase angle difference and the rated phase angle difference.

[0120] Optional, in the case of forward transmission, see Figure 10 The above-mentioned S301 “determining a first transmission strategy of active power according to a relationship between the phase angle difference and the rated phase angle difference” includes:

[0121] S3011. If the phase angle difference is less than the rated phase angle difference, the AC flux control module and the DC flux control module in the flexible interconnection device jointly transmit active power.

[0122] In this embodiment, when the transmission direction is forward transmission, if the phase angle difference is less than the rated phase angle difference, the AC flux control module and the DC flux control module in the flexible interconnection device jointly transmit active power. In this case, it can be determined whether the AC flux control module or the DC flux control module transmits active power based on the transmission power reference P* and the rated power Pe, as follows:

[0123] (1) When the transmission power reference P* is less than the rated power Pe of the AC flux control module, the power reference of the AC flux control module is P*, that is, the AC flux control module transmits all active power;

[0124] (2) When the transmission power reference P* is greater than the rated power Pe of the AC flux control module, the power reference of the AC flux control module is Pe. At this time, the remaining power (i.e., the difference between the transmission power reference P* and the rated power Pe of the AC flux control module) is transmitted by the DC flux control module. The required reactance value can be calculated by referring to the circuit model shown in formula (5), and the saturation degree of the DC flux control module can be controlled according to the reactance value. At this time, the adjustment range of active power is mainly determined by the phase angle difference. Decide.

[0125]

[0126] See also Figure 11 , provides a basic control flow chart of the flexible interconnection device, that is, after the required reactance value is calculated according to the circuit model, the reactance value range limit can be determined according to the reactance value, and a command signal is generated according to the reactance value range limit, and the command signal is sent to the DC flux control module to instruct the DC flux control module to work according to the instruction of the command signal. In addition, after the direct axis current is calculated according to the circuit model, and the measured direct-axis current The difference between the two generates the direct-axis voltage , and the quadrature-axis current calculated from the circuit model and the measured quadrature-axis current The difference between the two generates the quadrature axis voltage , then the direct axis voltage and quadrature axis voltage The dq transformation and SVPWM transformation are performed to obtain the transformed PWM pulse signal, and the PWM pulse signal is transmitted to the AC flux control module, so that the AC flux control module works according to the indication of the instruction signal.

[0127] S3012, if the phase angle difference is greater than the rated phase angle difference, the DC flux control module transmits active power.

[0128] In the embodiment, if the phase angle difference is greater than the rated phase angle difference, the DC flux control module transmits active power alone in the case of positive transmission direction. At this time, the transmission power reference P* is input, and the required reactance value is calculated according to the circuit model shown in formula (5), so as to control the saturation degree of the DC flux control module. At this time, the adjustment range of the active power is mainly determined by the phase angle difference and the reactance adjustment range of the DC flux control module.

[0129] S302, if the transmission direction is reverse transmission, the second transmission strategy of the active power is determined according to the relationship between the phase angle difference and the rated phase angle difference.

[0130] In the embodiment, in the case that the transmission direction of the active power between the first and second areas is reverse transmission, the second transmission strategy of the active power can be determined according to the relationship between the phase angle difference and the rated phase angle difference.

[0131] Optionally, in the case of positive transmission direction, referring to Figure 12 The above S302 “determining the first transmission strategy of the active power according to the relationship between the phase angle difference and the rated phase angle difference” comprises:

[0132] S3021, if the phase angle difference is less than the rated phase angle difference, the AC flux control module in the flexible interconnection device transmits active power.

[0133] In the embodiment, if the phase angle difference is less than the rated phase angle difference, the DC flux control module is cut out because the power transmission direction of the DC flux control module is limited by the phase angle direction in the case of reverse transmission direction. At this time, the AC flux control module transmits active power alone, and the power reference of the AC flux control module is P*. At this time, the adjustment range of the active power is the rated power of the AC flux control module.

[0134] S3022, if the phase angle difference is greater than the rated phase angle difference, the flexible interconnection device does not transmit active power.

[0135] In the embodiment, when the transmission direction is reverse transmission, if the phase angle difference is greater than the rated phase angle difference, the AC magnetic flux control module and the DC magnetic flux control module are both cut off, and at this time the flexible interconnection device has no power transmission capability.

[0136] It should be noted that according to the operation modes described in S3011, S3012, S3021 and S3022, the power transmission capability curve of the flexible interconnection device under different phase angle differences can be obtained, as shown in Figure 13 .

[0137] In the embodiment, by providing a novel control method corresponding to the flexible interconnection device, the control method can control the switching of the AC magnetic flux control module and the DC magnetic flux control module, so as to ensure the power transmission in the full phase angle range while ensuring the low manufacturing cost.

[0138] To quantitatively analyze the power transmission capability of the flexible interconnection device based on the AC-DC hybrid magnetic flux control and verify the accuracy of the equivalent circuit model, the present application also builds a simulation model of the flexible interconnection device based on the AC-DC hybrid magnetic flux control in Simulink, as shown in Figure 14 .

[0139] The AC magnetic flux control module in the simulation model is a back-to-back converter, which has two three-phase full-bridge converters as rectifiers and inverters respectively. The rectifier adopts DC voltage outer ring and AC current inner ring control; the inverter adopts AC current grid-connected control, and the reference value is calculated by power reference and grid-connected point voltage. In the simulation model, the waveforms of various electrical quantities can be viewed, as shown in Figure 15 , taking the waveforms of the grid-connected current of the AC magnetic control device and the output current of the magnetic control reactor as examples. As shown in Figure 15 , the amplitude of the grid-connected current of the AC magnetic flux control module increases with the increase of the active power reference value, and the overshoot process is small, which can follow the current reference without static error. As shown in Figure 16 , the current of the DC magnetic flux control module basically increases with the decrease of the reactor inductance. Based on Figure 13 , several typical working points are selected for simulation, and the simulation and theoretical calculation results are shown in Figure 17 . The simulation results show that there is basically no error between the simulation and theoretical analysis, which can illustrate the accuracy of the equivalent circuit model.

[0140] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0141] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile memory and volatile memory. The non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. The volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, the RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., without being limited thereto.

[0142] The technical features of the above embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0143] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A flexible interconnection device based on AC / DC hybrid magnetic flux control, characterized in that: The flexible interconnection device based on AC / DC hybrid magnetic flux control includes: a DC magnetic flux control module and an AC magnetic flux control module; The input end of the DC magnetic flux control module is connected to the output end of the transmission line of the first substation in the power grid structure, and the output end of the DC magnetic flux control module is connected to the input end of the transmission line of the second substation in the power grid structure; the input end of the AC magnetic flux control module is connected to the output end of the transmission line of the first substation, and the output end of the AC magnetic flux control module is connected to the input end of the transmission line of the second substation; A target flux control module is used to control the transmission of the active power between the first station area and the second station area based on the phase angle difference between the transmission signal of the first station area and the transmission signal of the second station area, and the transmission direction of the active power between the first station area and the second station area. The target flux control module includes: the AC flux control module, and / or the DC flux control module.

2. The flexible interconnection device based on AC / DC hybrid magnetic flux control according to claim 1, characterized in that: The AC flux control module based on AC / DC hybrid flux control includes: a step-down transformer, a back-to-back converter, and a single-phase transformer; The step-down transformer is used to convert the first AC voltage output by the transmission line of the first substation into a second AC voltage, and transmit the second AC voltage to the back-to-back converter; the voltage value of the first AC voltage is higher than the voltage value of the second AC voltage; The back-to-back converter is used to convert the second AC voltage into DC and transmit the converted second AC voltage to the single-phase transformer; The single-phase transformer is used to convert the converted second AC voltage into a third AC voltage and transmit the third AC voltage to the transmission line of the second station area; the voltage value of the second DC voltage is lower than the voltage value of the third DC voltage.

3. The flexible interconnection device based on AC / DC hybrid magnetic flux control according to claim 2, characterized in that: The back-to-back converter comprises: a first inverter, a capacitor and a second inverter; The first inverter is configured to convert the second AC voltage output by the step-down transformer into a fourth DC voltage; The capacitor is configured to filter the fourth DC voltage output by the first inverter to obtain a filtered fourth DC voltage, and transmit the filtered fourth DC voltage to the second inverter; The second inverter is configured to convert the filtered fourth DC voltage into a third AC voltage, and transmit the third AC voltage to the input end of the single-phase transformer.

4. The flexible interconnection device based on AC / DC hybrid magnetic flux control according to claim 2, characterized in that: The DC flux control module further includes: a first switching device; The input end of the first switching device is connected to the output end of the back-to-back converter, and the output end of the first switching device is connected to the input end of the single-phase transformer; The first switching device is used to control the on / off state of the AC magnetic flux control module.

5. The flexible interconnection device based on AC / DC hybrid magnetic flux control according to any one of claims 1 to 4, characterized in that: The DC flux control module includes a controllable reactor.

6. The flexible interconnection device based on AC / DC hybrid magnetic flux control according to claim 5, characterized in that: The DC flux control module further includes: a second switching device; The input end of the second switching device is connected to the output end of the controllable reactor, and the output end of the second switching device is connected to the transmission line of the second substation; The second switching device is used to control the on / off state of the DC flux control module.

7. A control method for a flexible interconnection device, characterized in that: Applied to the flexible interconnection device based on AC / DC hybrid flux control as described in any one of claims 1 to 6 above, the method comprises: Acquire the transmission direction of active power between a first substation and a second substation in the power grid structure, and the phase angle difference between the transmission voltage of the first substation and the transmission voltage of the second substation; determining an active power transmission strategy according to the transmission direction and the phase angle difference; Active power is transmitted between the first station area and the second station area according to the active power transmission strategy.

8. The method according to claim 7, characterized in that Determining the active power transmission strategy according to the transmission direction and the phase angle difference includes: If the transmission direction is forward transmission, determining a first transmission strategy for the active power according to a relationship between the phase angle difference and the rated phase angle difference; If the transmission direction is reverse transmission, the second transmission strategy of the active power is determined according to the relationship between the phase angle difference and the rated phase angle difference.

9. The method according to claim 8, characterized in that In a case where the transmission direction is forward transmission, determining the second transmission strategy of the active power according to the relationship between the phase angle difference and the rated phase angle difference includes: If the phase angle difference is less than the rated phase angle difference, the AC magnetic flux control module and the DC magnetic flux control module in the flexible interconnection device jointly transmit the active power; If the phase angle difference is greater than the rated phase angle difference, the DC flux control module transmits the active power.

10. The method according to claim 8, characterized in that In a case where the transmission direction is reverse transmission, determining the second transmission strategy of the active power according to the relationship between the phase angle difference and the rated phase angle difference includes: If the phase angle difference is less than the rated phase angle difference, the AC magnetic flux control module in the flexible interconnection device transmits the active power; If the phase angle difference is greater than the rated phase angle difference, the flexible interconnection device does not transmit the active power.

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