Network construction type AC-AC frequency converter control method and system for low-frequency power transmission

Abstract

The invention discloses a method and a system for controlling a network construction type AC-AC frequency converter for low-frequency power transmission, which are applied to the field of low-frequency power transmission, and comprise the following steps: determining the number of full-bridge sub-modules and the number of half-bridge sub-modules based on the maximum withstand voltage and rated operation current of an IGBT (Insulated Gate Bipolar Translator) and the exchangeable active power of the AC-AC frequency converter; determining a capacitor voltage average value based on the number of the full-bridge sub-modules, and adjusting an output AC voltage amplitude through the capacitor voltage average value; adjusting the output AC voltage frequency based on the exchange reactive power and the injection reactive power of the AC-AC frequency converter and the low-frequency AC system; adjusting the output AC voltage based on the AC voltage amplitude and the AC voltage frequency; and on the basis of the number of the half-bridge sub-modules, active power fed into the power frequency alternating current system by the power frequency side inversion direct current-alternating current conversion module is adjusted. According to the invention, stable and reliable transmission from the low-frequency AC system to the power-frequency AC power grid is realized.

Description

Technical Field

[0001] This invention relates to the field of low-frequency power transmission technology, and in particular to a control method and system for a grid-type AC-AC frequency converter used in low-frequency power transmission. Background Technology

[0002] Existing low-frequency power transmission uses modular multilevel matrix converters as AC-AC converters, which can convert low-frequency voltage and current into power-frequency voltage and current, providing a solution for large-scale long-distance transmission of new energy. Currently, flexible low-frequency AC-AC converters mostly adopt a three-phase, nine-arm topology, with each arm containing numerous full-bridge submodules. These submodules handle the voltages on both the low-frequency and power-frequency sides, thus achieving voltage and current conversion between different frequencies. However, existing AC-AC converters for low-frequency power transmission suffer from poor stability and reliability when transmitting low-frequency energy. Summary of the Invention

[0003] This invention provides a control method and system for a grid-type AC-AC frequency converter for low-frequency power transmission, in order to solve the technical problems of poor stability and poor reliability of existing AC-AC frequency converters when realizing low-frequency power transmission.

[0004] To address the aforementioned technical problems, this invention provides a control method for a grid-type AC-AC frequency converter for low-frequency power transmission. The AC-AC frequency converter includes a low-frequency voltage active support module and a power frequency side inverter DC-AC conversion module. The method includes: Based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC frequency converter, and the exchangeable active power of the AC-AC frequency converter, the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module are determined. The average capacitor voltage is determined based on the number of the full-bridge submodules, and the AC voltage amplitude output by the low-frequency voltage active support module is adjusted based on the average capacitor voltage. Based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module, the frequency of the AC voltage output by the low-frequency voltage active support module is adjusted. Based on the AC voltage amplitude and the AC voltage frequency, adjust the AC voltage output by the low-frequency voltage active support module; Based on the number of the half-bridge sub-modules, adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module.

[0005] As one preferred embodiment, the AC-AC inverter further includes a low-frequency side rectifier AC-DC converter module; adjusting the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module based on the number of the half-bridge sub-modules includes: By adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module, the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module is controlled. When the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module increases, the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module is controlled by adjusting the average capacitor voltage of the half-bridge submodule.

[0006] As one preferred embodiment, determining the average capacitor voltage based on the number of the full-bridge submodules, and adjusting the AC voltage amplitude output by the low-frequency voltage active support module using the average capacitor voltage includes: The average capacitor voltage is determined based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules. The amplitude of the base AC voltage is determined based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage. Based on the average capacitor voltage and the baseline AC voltage amplitude, the AC voltage amplitude output by the low-frequency voltage active support module is adjusted.

[0007] As one preferred embodiment, adjusting the AC voltage frequency output by the low-frequency voltage active support module based on the exchange reactive power between the AC-AC converter and the low-frequency AC system, and the injected reactive power of the low-frequency voltage active support module includes: The system frequency deviation is determined based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system. The base AC voltage frequency is determined based on the system frequency deviation and the rated low-frequency operating frequency. Based on the injected reactive power of the low-frequency voltage active support module and the frequency of the base AC voltage, the frequency of the AC voltage output by the low-frequency voltage active support module is adjusted.

[0008] As one preferred embodiment, adjusting the AC voltage output by the low-frequency voltage active support module based on the AC voltage amplitude and the AC voltage frequency includes: Based on the AC voltage amplitude and the AC voltage frequency, the three-phase voltage modulation wave of the low-frequency voltage active support module is determined; By adjusting the usage data of the full-bridge submodule, the low-frequency voltage active support module is controlled to output the AC voltage corresponding to the three-phase voltage modulation wave.

[0009] Another embodiment of the present invention provides a grid-type AC-AC converter control system for low-frequency power transmission, comprising: The sub-module quantity determination module is used to determine the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC converter and the exchangeable active power of the AC-AC converter. An AC voltage amplitude adjustment module is used to determine the average capacitor voltage based on the number of the full-bridge sub-modules, and adjust the AC voltage amplitude output by the low-frequency voltage active support module based on the average capacitor voltage. An AC voltage frequency adjustment module is used to adjust the AC voltage frequency output by the low-frequency voltage active support module based on the reactive power exchanged between the AC-AC inverter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module. An output AC voltage adjustment module is used to adjust the AC voltage output by the low-frequency voltage active support module based on the AC voltage amplitude and the AC voltage frequency. The active power adjustment module is used to adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module based on the number of the half-bridge sub-modules.

[0010] As one preferred embodiment, the feed-in active power adjustment module includes: The DC voltage regulation unit is used to control the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module by adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module. The active power control unit is used to control the active power fed into the power frequency AC system by adjusting the average value of the capacitor voltage of the half-bridge submodule when the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module increases.

[0011] As one preferred embodiment, the AC voltage amplitude adjustment module includes: The capacitor voltage average value determination unit is used to determine the average capacitor voltage based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules; A basic AC voltage amplitude determination unit is used to determine the basic AC voltage amplitude based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage. An output AC voltage amplitude adjustment unit is used to adjust the AC voltage amplitude output by the low-frequency voltage active support module based on the average capacitor voltage and the basic AC voltage amplitude.

[0012] Another embodiment of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the grid-type AC-AC converter control method for low-frequency power transmission as described above.

[0013] Another embodiment of the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the grid-type AC-AC converter control method for low-frequency power transmission as described above.

[0014] This invention provides a control method and system for a grid-type AC-AC frequency converter for low-frequency power transmission. The AC-AC frequency converter, comprising a low-frequency voltage active support module and a power frequency side inverter DC-AC conversion module, controls the grid-building logic of the low-frequency voltage active support module. The output AC voltage amplitude is adjusted based on the average value of the sub-module capacitor voltage to achieve active power balance in the system. The output AC voltage frequency is adjusted based on the reactive power of the low-frequency system to ensure reactive power balance. This enables stable and reliable power transmission from the low-frequency AC system to the power frequency AC grid. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the control method for a grid-type AC-AC frequency converter for low-frequency power transmission provided by the present invention. Figure 2 This is a topology diagram of a grid-type AC-AC converter for low-frequency power transmission provided by the present invention; Figure 3 This is a schematic diagram of the structure of the grid-type AC-AC frequency converter control system for low-frequency power transmission provided by the present invention; Figure 4 This is a schematic diagram of the structure of the electronic device provided by the present invention.

[0016] Figure label: Among them, 301 is the submodule quantity determination module; 302 is the AC voltage amplitude adjustment module; 303 is the AC voltage frequency adjustment module; 304 is the output AC voltage adjustment module; 305 is the input active power adjustment module; 410 is the processor; 420 is the communication interface; 430 is the memory; and 440 is the communication bus. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] See Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the grid-type AC-AC converter control method for low-frequency power transmission provided by the present invention, as shown below. Figure 1 As shown, this embodiment includes steps 100 to 500, and the specific steps are as follows: Step 100: Based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC converter, and the exchangeable active power of the AC-AC converter, determine the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module. like Figure 2 As shown, the grid-type AC-AC converter for low-frequency power transmission provided by this invention mainly comprises three parts: a low-frequency voltage active support module, a low-frequency side rectifier AC-DC converter module, and a power frequency side inverter DC-AC converter module. The low-frequency voltage active support module is a full-bridge submodule series valve, supporting the low-frequency side AC voltage through the full-bridge submodule. Each low-frequency side rectifier AC-DC converter module is connected in parallel with one low-frequency voltage active support module, providing voltage support for the low-frequency side rectifier AC-DC converter module and the low-frequency AC grid (e.g., a low-frequency islanded renewable energy system). The low-frequency side rectifier AC-DC converter module is a diode series rectifier valve, which can employ two six-pulse diode rectifier valves in series. The power frequency side inverter DC-AC converter module is a half-bridge submodule series valve, realizing the conversion between DC voltage and power frequency AC voltage through the half-bridge submodule.

[0022] The low-frequency voltage active support module consists of three-phase chained full-bridge sub-modules connected in series. The number of modules in each phase is equal. Each phase module is connected to the corresponding low-frequency rectifier AC / DC converter module on one side, and the other side's three phases are directly connected after convergence. Simultaneously, the low-frequency rectifier AC / DC converter module and the low-frequency voltage active support module are connected in parallel and then connected to the low-frequency AC power grid via a low-frequency transformer. Each low-frequency rectifier AC / DC converter module is connected in parallel with an independent low-frequency voltage active support module. A surge arrester is added between the chain ends of each phase full-bridge sub-module of the low-frequency voltage active support module to dissipate excess power overvoltage generated by a transformer valve-side grounding fault. The power frequency side inverter AC / DC converter module is formed by connecting half-bridge sub-modules in series. The number of modules in each phase is equal. Each phase module is connected to the power frequency transformer on one side and to the low-frequency rectifier AC / DC converter module on the other side. The AC side of the low-frequency rectifier AC / DC converter module is connected to the low-frequency transformer, and the DC side is connected to the power frequency inverter AC / DC converter module.

[0023] The number of full-bridge submodules in the low-frequency voltage active support module is related to the number of half-bridge submodules in the power frequency side inverter DC-AC converter module, the AC-AC inverter's transmission capacity level, and the specifications of the selected fully controlled power electronic devices (Insulate-Gate Bipolar Transistor, IGBT). Assume the maximum withstand voltage of the fully controlled power electronic device is... Rated operating current is The active power that the AC-AC frequency converter can exchange is The number of full-bridge submodules in the low-frequency voltage active support module Number of half-bridge submodules of the power frequency side inverter DC-AC converter module The calculation is shown in Formula 1.

[0024] (1) in, In the calculation, 0.5 indicates that the rated operating voltage of the IGBT is usually half of the maximum withstand voltage; 6× indicates that the inverter DC-AC converter module on the power frequency side has a total of 6 bridge arms; 1.05 indicates that each bridge arm is considered to have 5% redundancy. In the calculation, 1.35 represents the ratio between the equivalent values ​​of AC voltage and DC voltage during diode valve rectification; This indicates the ratio between the DC voltage and its equivalent value; 3× indicates that the low-frequency voltage active support module includes a total of 3 bridge arms.

[0025] Step 200: Determine the average capacitor voltage based on the number of the full-bridge submodules, and adjust the AC voltage amplitude output by the low-frequency voltage active support module using the average capacitor voltage. Specifically, the control method for the low-frequency voltage active support module is as follows: First, the capacitor voltages of all full-bridge submodules in the two low-frequency voltage active support sections are detected, summed, and then divided by the number of full-bridge submodules to obtain two average values. These two average values ​​are then averaged to obtain the average capacitor voltage. Let the rated value of the average capacitor voltage of the full-bridge submodules be the rated capacitor voltage. After subtracting the rated capacitor voltage from the average capacitor voltage, the difference between the AC voltage and the rated AC voltage is obtained through a proportional-integral (PI) circuit. Further, this difference is added to the reference AC voltage to obtain the basic AC voltage amplitude.

[0026] To further enhance the AC voltage coordination, the average values ​​of the two low-frequency voltage active support components are subtracted, and the deviation is obtained through a proportional-integral circuit. Based on the basic AC voltage amplitude, one low-frequency voltage active support component increases the deviation, while the other low-frequency voltage active support component decreases the deviation, thus obtaining the AC voltage amplitude output by the two low-frequency voltage active support components.

[0027] Step 300: Based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module, adjust the frequency of the AC voltage output by the low-frequency voltage active support module. Then, the reactive power exchanged between the AC-AC inverter and the low-frequency AC system (i.e., the exchanged reactive power) is detected. The difference between the exchanged reactive power setting value and the exchanged reactive power is calculated, and the system frequency deviation is obtained through a proportional-integral (PI) stage. The system frequency deviation is added to the rated low-frequency operating frequency to obtain the base AC voltage frequency. To achieve reactive power balance between the two low-frequency voltage active support sections, a reactive frequency coordination stage is added. This is done by subtracting the reactive power injected by the two low-frequency voltage active support sections and obtaining the deviation through a PI stage. Based on the base AC voltage frequency, one low-frequency voltage active support section reduces this deviation, while the other low-frequency voltage active support section increases it, resulting in the AC voltage frequencies output by the two low-frequency voltage active support sections.

[0028] Step 400: Based on the AC voltage amplitude and the AC voltage frequency, adjust the AC voltage output by the low-frequency voltage active support module; Specifically, based on the two AC voltage amplitudes and two AC voltage frequencies obtained above, the three-phase voltage modulation waves of the two low-frequency voltage active support sections are calculated. By adjusting the number and direction of the full-bridge sub-modules of the low-frequency voltage active support module, the low-frequency voltage active support module outputs an AC voltage corresponding to the three-phase voltage modulation wave.

[0029] Step 500: Based on the number of the half-bridge sub-modules, adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module.

[0030] Specifically, the number of half-bridge submodules obtained above The number of half-bridge sub-modules is a core quantitative parameter for the hardware selection and construction of the power frequency side inverter DC-AC converter module. It determines the bridge arm structure of the power frequency side inverter DC-AC converter module (e.g., how many half-bridge sub-modules are needed in series per phase). The power frequency side inverter DC-AC converter module controls the active power fed into the AC system through the average capacitor voltage of the half-bridge sub-modules, and this average capacitor voltage is calculated based on the number of half-bridge sub-modules.

[0031] This embodiment constructs an AC-AC converter topology including a low-frequency voltage active support module and a power frequency side inverter DC-AC conversion module. The network logic of the low-frequency voltage active support module is controlled, adjusting the output AC voltage amplitude based on the average value of the submodule capacitor voltage to achieve active power balance in the system. The output AC voltage frequency is adjusted based on the reactive power of the low-frequency system to ensure reactive power balance. This enables stable and reliable power transmission from the isolated low-frequency renewable energy system to the power frequency AC grid.

[0032] In another embodiment of the grid-type AC-AC converter control method for low-frequency power transmission provided by the present invention, step 200 specifically includes: Step 210: Determine the average capacitor voltage based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules; Step 220: Determine the amplitude of the base AC voltage based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage; Step 230: Based on the average value of the capacitor voltage and the amplitude of the basic AC voltage, adjust the amplitude of the AC voltage output by the low-frequency voltage active support module.

[0033] Specifically, as shown in Formulas 2 and 3, the capacitor voltages of all full-bridge submodules in the two low-frequency voltage active support sections are detected, summed, and then divided by the number of full-bridge submodules for each section. Two average values ​​were obtained. and The average of these two averages is then taken to obtain the average capacitor voltage. Let the rated value of the average operating value of the capacitor voltage of the full-bridge submodule be the rated value of the capacitor voltage. The rated capacitor voltage is subtracted from the average capacitor voltage, and then passed through a proportional-integral circuit. The difference between the AC voltage and the rated AC voltage is obtained. The difference is then added to the reference AC voltage to obtain the amplitude of the base AC voltage. .in, This is the proportional coefficient of the proportional integral element; The integral coefficient of the proportional-integral component; For the Laplace operator.

[0034] (2) (3) To further enhance the AC voltage coordination, as shown in Formula 4, the average value of the two low-frequency voltage active support components mentioned above is... and Subtraction, through the proportional-integral process The deviation is obtained from the amplitude of the base AC voltage. Based on this, one low-frequency voltage active support section increases the deviation, while the other low-frequency voltage active support section decreases the deviation, thus obtaining the AC voltage amplitudes output by the two low-frequency voltage active support sections respectively. and .

[0035] (4) In formula 4, The proportional coefficient of the proportional-integral link for the capacitor voltage deviation of the submodule; The integral coefficient of the proportional-integral link for the capacitor voltage deviation of the submodule; For the Laplace operator.

[0036] This embodiment uses the submodule capacitor voltage as a control element to actively adjust the low-frequency voltage to actively support the AC voltage amplitude output by the module, thereby meeting the system's requirements for active power transmission and power balance.

[0037] In another embodiment of the grid-type AC-AC converter control method for low-frequency power transmission provided by the present invention, step 300 specifically includes: Step 310: Determine the system frequency deviation based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system; Step 320: Determine the base AC voltage frequency based on the system frequency deviation and the rated low-frequency operating frequency; Step 330: Based on the injected reactive power of the low-frequency voltage active support module and the base AC voltage frequency, adjust the AC voltage frequency output by the low-frequency voltage active support module.

[0038] Specifically, regarding reactive power balance control, the reactive power exchanged between the AC-AC converter and the low-frequency AC system is first detected. That is, to exchange reactive power, the set value of the exchange reactive power. Compared with actual value The difference is calculated by using a proportional-integral (PI) circuit to obtain the system frequency deviation. With the rated low-frequency operating frequency The basic AC voltage frequency is obtained by adding them together. As shown in formulas 5 and 6, where, This is the proportional coefficient of the proportional-integral link in this embodiment; This refers to the integral coefficient of the proportional-integral term in this embodiment; For the Laplace operator.

[0039] (5) (6) To achieve reactive power balance between the two low-frequency voltage active support sections, a reactive power frequency coordination link is added to adjust the reactive power injected into the two low-frequency voltage active support sections. and Subtracting the two, the deviation is obtained through the proportional-integral process. Based on this, one low-frequency voltage active support section reduces the deviation, while the other low-frequency voltage active support section increases the deviation, thus obtaining the AC voltage frequencies output by the two low-frequency voltage active support sections respectively. and .

[0040] (7) In formula 7, and These represent the proportional coefficient and integral coefficient of the proportional-integral link, respectively, for the reactive power deviation component. For the Laplace operator.

[0041] This embodiment uses the low-frequency system frequency as a control element to actively adjust the AC voltage frequency output by the low-frequency voltage active support module, thereby meeting the system's reactive power balance requirements.

[0042] In another embodiment of the grid-type AC-AC converter control method for low-frequency power transmission provided by the present invention, step 400 specifically includes: Step 401: Based on the AC voltage amplitude and the AC voltage frequency, determine the three-phase voltage modulation wave of the low-frequency voltage active support module; Step 402: By adjusting the usage data of the full-bridge submodule, control the low-frequency voltage active support module to output the AC voltage corresponding to the three-phase voltage modulation wave.

[0043] Specifically, as shown in Formulas 8 and 9, based on the two AC voltage amplitudes obtained above... and and two AC voltage frequencies and The three-phase voltage modulation waves of the two low-frequency voltage active support sections are calculated. By adjusting the usage data of the full-bridge submodule of the low-frequency voltage active support module (such as the number and direction of connection), the low-frequency voltage active support module outputs an AC voltage corresponding to the three-phase voltage modulation wave.

[0044] (8) (9) Formula 8 , and This is a three-phase voltage modulation wave for a low-frequency voltage active support section; in Formula 9... , and This is a three-phase voltage modulation wave for another low-frequency voltage active support section; For time.

[0045] This embodiment achieves regulation of the AC voltage output by the low-frequency voltage active support module by adjusting the AC voltage amplitude and AC voltage frequency.

[0046] In another embodiment of the grid-type AC-AC converter control method for low-frequency power transmission provided by the present invention, step 500 specifically includes: Step 510: By adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module, control the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module; Step 520: When the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter AC-DC converter module increases, the active power fed into the power frequency AC system by the power frequency side inverter AC-DC converter module is controlled by adjusting the average capacitor voltage of the half-bridge submodule.

[0047] The low-frequency side rectifier AC / DC converter module consists of a converter valve (i.e., a diode rectifier valve) formed by diodes connected in series. The AC side of the low-frequency side rectifier AC / DC converter module is connected to a low-frequency transformer (e.g., 20Hz), and the DC side is connected to the power frequency side inverter AC / DC converter module. A parallel resistor-capacitor voltage divider is connected to the diode converter valve to ensure voltage balance among the series-connected diodes. Two sets of six-pulse diode valve groups are connected in series and then connected to the low-frequency transformer and the low-frequency voltage active support module, respectively. Due to the use of a certain number of diodes as the AC / DC conversion device, the operational reliability of the components is relatively high.

[0048] (10) (11) Specifically, the DC voltage output by the diode rectifier valves can be controlled by controlling the AC voltage output from the low-frequency voltage active support module. The DC voltages output by the two diode rectifier valves are respectively... and Its expression is similar to that of AC voltage. and The relationship between them is shown in Equation 10. The DC voltage output by the diode-connected rectifier valve. As shown in Formula 11.

[0049] When the system's active power is unbalanced, if the active power output from the low-frequency AC grid is higher than the active power injected into the power frequency AC grid by the inverter DC-AC converter module on the power frequency side, the voltage of the series valve capacitor in the half-bridge submodule of the inverter DC-AC converter module on the power frequency side will continuously increase, further leading to an increase in DC voltage. Since the active power of the diode series rectifier valve cannot be transmitted externally, the active power output from the low-frequency AC grid is injected into the low-frequency voltage active support module. The low-frequency voltage active support module adjusts the amplitude of the output AC voltage through the aforementioned control, increasing... This increases the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module. The power frequency side inverter DC-AC converter module, through the average value of the capacitor voltage of the sub-modules, controls and increases the active power fed into the AC system, thereby achieving power balance. Conversely, similar logic is used to achieve system power balance.

[0050] This embodiment determines the amount of active power transmitted from the rectifier section to the power frequency side by changing the DC voltage, and indirectly achieves power regulation of the rectifier section through downstream control.

[0051] The following describes the grid-type AC-AC converter control system for low-frequency power transmission provided by the present invention. The grid-type AC-AC converter control system for low-frequency power transmission described below can be referred to in correspondence with the grid-type AC-AC converter control method for low-frequency power transmission described above.

[0052] Please refer to Figure 3 The present invention also provides a grid-type AC-AC converter control system for low-frequency power transmission, comprising: The sub-module quantity determination module 301 is used to determine the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC inverter and the exchangeable active power of the AC-AC inverter. The AC voltage amplitude adjustment module 302 is used to determine the average capacitor voltage based on the number of the full-bridge submodules, and adjust the AC voltage amplitude output by the low-frequency voltage active support module through the average capacitor voltage. The AC voltage frequency adjustment module 303 is used to adjust the AC voltage frequency output by the low-frequency voltage active support module based on the reactive power exchanged between the AC-AC inverter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module. The output AC voltage adjustment module 304 is used to adjust the AC voltage output by the low-frequency voltage active support module based on the AC voltage amplitude and the AC voltage frequency. The active power adjustment module 305 is used to adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module based on the number of the half-bridge sub-modules.

[0053] Optionally, the feed-in active power adjustment module includes: The DC voltage regulation unit is used to control the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module by adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module. The active power control unit is used to control the active power fed into the power frequency AC system by adjusting the average value of the capacitor voltage of the half-bridge submodule when the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module increases.

[0054] Optionally, the AC voltage amplitude adjustment module includes: The capacitor voltage average value determination unit is used to determine the average capacitor voltage based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules; A basic AC voltage amplitude determination unit is used to determine the basic AC voltage amplitude based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage. An output AC voltage amplitude adjustment unit is used to adjust the AC voltage amplitude output by the low-frequency voltage active support module based on the average capacitor voltage and the basic AC voltage amplitude.

[0055] Please refer to Figure 4 The present invention also provides a schematic diagram of the physical structure of an electronic device, such as... Figure 4 As shown, the electronic device may include a processor 410, a communication interface 420, a memory 430, and a communication bus 440, wherein the processor 410, the communication interface 420, and the memory 430 communicate with each other through the communication bus 440. The processor 410 can call logic instructions in the memory 430 to execute a grid-type AC-AC inverter control method for low-frequency power transmission.

[0056] Furthermore, the logical instructions in the aforementioned memory 430 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0057] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to perform the grid-type AC-AC converter control method for low-frequency power transmission provided by the methods described above.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A control method for a grid-type AC-AC frequency converter for low-frequency power transmission, characterized in that, The AC-AC inverter includes a low-frequency voltage active support module and a power frequency side inverter DC-AC conversion module. The method includes: Based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC frequency converter, and the exchangeable active power of the AC-AC frequency converter, the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module are determined. The average capacitor voltage is determined based on the number of the full-bridge submodules, and the AC voltage amplitude output by the low-frequency voltage active support module is adjusted based on the average capacitor voltage. Based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module, the frequency of the AC voltage output by the low-frequency voltage active support module is adjusted. Based on the AC voltage amplitude and the AC voltage frequency, adjust the AC voltage output by the low-frequency voltage active support module; Based on the number of the half-bridge sub-modules, adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module.

2. The control method for a grid-type AC-AC frequency converter for low-frequency power transmission as described in claim 1, characterized in that, The AC-AC inverter also includes a low-frequency side rectifier AC-DC converter module; adjusting the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module based on the number of the half-bridge sub-modules includes: By adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module, the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module is controlled. When the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module increases, the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module is controlled by adjusting the average capacitor voltage of the half-bridge submodule.

3. The control method for a grid-type AC-AC frequency converter for low-frequency power transmission as described in claim 1, characterized in that, The step of determining the average capacitor voltage based on the number of the full-bridge submodules, and adjusting the AC voltage amplitude output by the low-frequency voltage active support module using the average capacitor voltage, includes: The average capacitor voltage is determined based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules. The amplitude of the base AC voltage is determined based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage. Based on the average capacitor voltage and the basic AC voltage amplitude, the AC voltage amplitude output by the low-frequency voltage active support module is adjusted.

4. The control method for a grid-type AC-AC frequency converter for low-frequency power transmission as described in claim 1, characterized in that, The adjustment of the AC voltage frequency output by the low-frequency voltage active support module, based on the exchange reactive power between the AC-AC converter and the low-frequency AC system, and the injected reactive power of the low-frequency voltage active support module, includes: The system frequency deviation is determined based on the reactive power exchanged between the AC-AC converter and the low-frequency AC system. Based on the system frequency deviation and the rated low-frequency operating frequency, the base AC voltage frequency is determined; Based on the injected reactive power of the low-frequency voltage active support module and the frequency of the base AC voltage, the frequency of the AC voltage output by the low-frequency voltage active support module is adjusted.

5. The control method for a grid-type AC-AC frequency converter for low-frequency power transmission as described in claim 1, characterized in that, The step of adjusting the AC voltage output by the low-frequency voltage active support module based on the AC voltage amplitude and the AC voltage frequency includes: Based on the AC voltage amplitude and the AC voltage frequency, the three-phase voltage modulation wave of the low-frequency voltage active support module is determined; By adjusting the usage data of the full-bridge submodule, the low-frequency voltage active support module is controlled to output the AC voltage corresponding to the three-phase voltage modulation wave.

6. A grid-type AC-AC frequency converter control system for low-frequency power transmission, characterized in that, include: The sub-module quantity determination module is used to determine the number of full-bridge sub-modules of the low-frequency voltage active support module and the number of half-bridge sub-modules of the power frequency side inverter DC-AC conversion module based on the maximum withstand voltage and rated operating current of the fully controlled power electronic device IGBT selected by the AC-AC converter and the exchangeable active power of the AC-AC converter. An AC voltage amplitude adjustment module is used to determine the average capacitor voltage based on the number of the full-bridge sub-modules, and adjust the AC voltage amplitude output by the low-frequency voltage active support module based on the average capacitor voltage. An AC voltage frequency adjustment module is used to adjust the AC voltage frequency output by the low-frequency voltage active support module based on the reactive power exchanged between the AC-AC inverter and the low-frequency AC system, and the reactive power injected by the low-frequency voltage active support module. An output AC voltage adjustment module is used to adjust the AC voltage output by the low-frequency voltage active support module based on the AC voltage amplitude and the AC voltage frequency. The active power adjustment module is used to adjust the active power fed into the power frequency AC system by the power frequency side inverter DC-AC converter module based on the number of the half-bridge sub-modules.

7. The grid-type AC-AC frequency converter control system for low-frequency power transmission as described in claim 6, characterized in that, The feed-in active power adjustment module includes: The DC voltage regulation unit is used to control the DC voltage output by the diode rectifier valve of the low-frequency side rectifier AC-DC converter module by adjusting the amplitude of the AC voltage output by the low-frequency voltage active support module. The active power control unit is used to control the active power fed into the power frequency AC system by adjusting the average value of the capacitor voltage of the half-bridge submodule when the DC voltage increases and the active power output from the low-frequency side rectifier AC-DC converter module to the power frequency side inverter DC-AC converter module increases.

8. The grid-type AC-AC frequency converter control system for low-frequency power transmission as described in claim 7, characterized in that, The AC voltage amplitude adjustment module includes: The capacitor voltage average value determination unit is used to determine the average capacitor voltage based on the capacitor voltage of all full-bridge submodules and the number of full-bridge submodules; A basic AC voltage amplitude determination unit is used to determine the basic AC voltage amplitude based on the difference between the average value of the capacitor voltage and the rated value of the capacitor voltage. An output AC voltage amplitude adjustment unit is used to adjust the AC voltage amplitude output by the low-frequency voltage active support module based on the average capacitor voltage and the basic AC voltage amplitude.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the grid-type AC-AC converter control method for low-frequency power transmission as described in any one of claims 1 to 5.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the grid-type AC-AC converter control method for low-frequency power transmission as described in any one of claims 1 to 5.

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