A three-phase grid-connected converter control method, circuit, device and medium

Abstract

The application discloses a three-phase grid-connected converter control method, a circuit, a device and a medium, and relates to the technical field of AC-DC power distribution systems. The three-phase grid-connected converter control method provided by the application establishes a mathematical model of the three-phase grid-connected converter, combines the causes and suppression mechanism of the leakage current, controls the filter capacitor voltage in the zero sequence loop to be a constant value through a PI regulator, and effectively attenuates the leakage current. The phase angle of the grid voltage is obtained in a three-phase stationary coordinate system, the sampling quantity is coordinate-transformed according to the angle, a modulation signal is obtained, and the power switch tube in the grid-connected converter is controlled according to the modulation signal. Since only one connected wire needs to be added between the middle point of the filter capacitor and the common point of the lower bridge arm in the scheme, the cost is low, and the leakage current caused by the existence of the parasitic capacitance of the DC side power distribution device to the ground can be limited to the microampere level.

Description

Technical Field

[0001] This application relates to the field of AC / DC power distribution system technology, specifically to a three-phase grid-connected converter control method, circuit, device, and medium. Background Technology

[0002] In recent years, with the development of power electronics technology, building electrification has become a future development trend to adapt to user-side distributed photovoltaic, energy storage, and flexible access to terminal loads. To achieve electrical isolation between the power grid and the building's power distribution system and ensure the electrical safety of people in the building, building power distribution systems often use isolated grid-connected converters with power frequency or high frequency transformers connected to the power grid to eliminate safety hazards caused by leakage current. However, this results in low system efficiency and high investment costs. Therefore, the application of non-isolated three-phase grid-connected converters is becoming increasingly widespread.

[0003] Figure 1 The circuit diagram for an existing residential three-phase grid-connected converter topology, such as... Figure 1 The diagram shows a three-phase AC grid, an LCL filter, a three-phase voltage source rectifier, and a DC bus section. The three-phase AC grid-side voltages ea, eb, and ec have their common terminal connected to ground, and the grounding resistance Rg is used to equivalently represent the source-side resistance to ground. The grid-side voltages are connected to the three-phase voltage source rectifier via an LCL filter consisting of three-phase grid-side filter inductors Lga, Lgb, and Lgc, filter capacitors Cfa, Cfb, and Cfc, and switch-side filter inductors Lfa, Lfb, and Lfc. The three-phase voltage source rectifier consists of a first bridge arm of phase A, a second bridge arm of phase B, and a third bridge arm of phase C. Each of the three bridge arms includes two parallel power switching transistors. U, V, and W represent the midpoint of the phase A bridge arm. Current non-isolated converter control methods for eliminating leakage current and common-mode voltage mainly involve improving the topology of the photovoltaic inverter by adding an extra fourth bridge arm and using an independent bridge arm control method based on inductor current feedback. Although this method can suppress leakage current and common-mode voltage, it increases the cost and power loss due to the addition of extra switching devices.

[0004] Given the above-mentioned technologies, finding a low-cost control method for three-phase grid-connected converters that can attenuate leakage current and smooth common-mode voltage is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a control method, circuit, device, and medium for a three-phase grid-connected converter, in order to solve the current non-isolated converter control method for eliminating leakage current and common-mode voltage. This method mainly improves the topology of the photovoltaic inverter by adding an additional fourth bridge arm and using an independent bridge arm control method based on inductor current feedback. This overcomes the contradiction that the common-mode voltage and leakage current of the three-phase converter cannot be suppressed at the same time. However, the addition of additional switching devices leads to higher costs and power losses. In addition, this method cannot completely eliminate the leakage current problem of the photovoltaic inverter.

[0006] To solve the above-mentioned technical problems, this application provides a three-phase grid-connected converter control method, including:

[0007] The common-mode voltage fluctuation characteristics of the grid-connected converter were obtained through Simulink simulation.

[0008] When the midpoint of the filter capacitor and the common point of the lower bridge arm are connected, the voltage of the filter capacitor in the zero-sequence loop is controlled to be constant by the PI regulator, and the voltage of the filter capacitor is recorded.

[0009] A dynamic mathematical model is established based on the grid-connected converter structure, and the grid phase angle of the grid-side voltage in the stationary coordinate system is detected.

[0010] The modulation signal is obtained based on the voltage of the filter capacitor and the phase angle of the power grid;

[0011] The bridge arm power switch is controlled according to the modulation signal.

[0012] Preferably, obtaining the modulation signal based on the filter capacitor voltage and the power grid phase angle includes:

[0013] Based on the grid phase angle, the Parker transformation is performed on the switch-side inductor current, the filter capacitor voltage, and the filter capacitor current in the stationary coordinate system to obtain the parameters in the synchronous rotating coordinate system.

[0014] The zero-sequence component of the filter capacitor voltage is compared with the zero-sequence voltage reference value, and the zero-sequence reference value of the filter capacitor current is obtained through the PI regulator.

[0015] The modulation ratio is obtained by comparing the zero-sequence reference value with the filter capacitor current, and the modulation ratio is then inversely transformed to obtain the modulation signal.

[0016] Preferably, obtaining the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation includes:

[0017] The common-mode voltage fluctuation characteristics are obtained by observing the pulsating voltage on the DC-side parasitic capacitor and the leakage current generated by the pulsating voltage through Simulink simulation.

[0018] Preferably, before controlling the bridge arm power switch according to the modulation signal, the method further includes:

[0019] Detect whether the modulated signal meets a preset standard;

[0020] If so, proceed to the step of controlling the bridge arm power switch according to the modulation signal;

[0021] If not, then trigger an alarm.

[0022] To address the aforementioned issues, this application also provides a three-phase grid-connected converter control circuit, comprising: a three-phase AC grid, an LCL filter, a three-phase voltage source rectifier, a DC bus, a control switch, and a detection device;

[0023] The input terminal of the three-phase AC power grid is grounded, and the output terminal is connected to the input terminal of the LCL filter.

[0024] The output terminal of the LCL filter is connected to the input terminal of the three-phase voltage source rectifier.

[0025] The output terminal of the three-phase voltage source rectifier is connected to the DC bus.

[0026] The control switch is located between the midpoint of the filter capacitor and the common point of the lower bridge arm.

[0027] The detection device is connected to the control switch. When the control switch is open, the detection device is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation. When the control switch is closed, the detection device controls the voltage of the filter capacitor in the zero-sequence loop to a constant value through a PI regulator and records the voltage of the filter capacitor. A dynamic mathematical model is established based on the grid-connected converter structure, and the grid phase angle of the grid-side voltage in the stationary coordinate system is detected. Based on the voltage of the filter capacitor and the grid phase angle, a modulation signal is obtained, and the bridge arm power switch is controlled based on the modulation signal.

[0028] Preferably, it further includes: a positive DC bus capacitor and a negative DC bus capacitor;

[0029] One end of the positive DC bus capacitor is connected to the positive terminal of the DC bus, and the other end is grounded.

[0030] One end of the negative DC bus capacitor is connected to the negative terminal of the DC bus, and the other end is grounded.

[0031] Preferably, it further includes: a voltage stabilizing capacitor;

[0032] The voltage stabilizing capacitor is located between the DC bus and the common terminals of the upper and lower bridge arms of the three-phase voltage source rectifier.

[0033] To address the aforementioned problems, this application also provides a three-phase grid-connected converter control device, comprising:

[0034] The simulation module is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation;

[0035] The recording module is used to connect the midpoint of the filter capacitor and the common point of the lower bridge arm, and to control the voltage of the filter capacitor in the zero-sequence loop to a constant value through a PI regulator, and to record the voltage of the filter capacitor.

[0036] The detection module is used to establish a dynamic mathematical model based on the grid-connected converter structure and detect the grid phase angle of the grid-side voltage in the stationary coordinate system.

[0037] The acquisition module is used to acquire the modulation signal based on the voltage of the filter capacitor and the phase angle of the power grid;

[0038] The control module is used to control the bridge arm power switching transistors according to the modulation signal.

[0039] To address the aforementioned issues, this application also provides a three-phase grid-connected converter control device, including a memory for storing computer programs;

[0040] A processor is used to execute the computer program to implement the steps of the three-phase grid-connected converter control method described above.

[0041] To address the aforementioned problems, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the three-phase grid-connected converter control method described above.

[0042] The three-phase grid-connected converter control method provided in this application obtains the common-mode voltage and leakage current waveforms of the three-phase grid-connected converter through simulation. Combining the causes and suppression mechanisms of leakage current, an equivalent circuit diagram of the parasitic leakage current path is established to achieve zero-sequence control of the common-mode voltage. A PI regulator is used to control the voltage of the filter capacitor in the zero-sequence loop to a constant value, and the filter capacitor voltage is recorded. Based on the structural model of the grid-connected converter, its mathematical model is established in a three-phase stationary coordinate system. Using phase-locked loop (PLL) technology, the grid voltage phase angle is obtained in the three-phase stationary coordinate system. Based on this phase angle, a coordinate transformation is performed, converting the rotational quantity in the three-phase stationary coordinate system into a DC quantity in a synchronous rotating coordinate system. The transformed DC quantity is compared with the carrier signal to obtain the modulation signal, and the power switching transistors in the grid-connected converter are controlled according to the modulation signal. Since this scheme only requires adding a connecting wire between the midpoint of the filter capacitor and the common point of the lower bridge arm, the cost is low. Furthermore, since no other new bridge arm components are added, the leakage current caused by the parasitic capacitance to ground of the DC-side power distribution device is limited to the microampere level.

[0043] The three-phase grid-connected converter control circuit, three-phase grid-connected converter control device, and computer-readable storage medium provided in this application correspond to the three-phase grid-connected converter control method described above, and have the same beneficial effects. Attached Figure Description

[0044] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 The circuit diagram for the existing three-phase grid-connected converter topology;

[0046] Figure 2 A flowchart of a three-phase grid-connected converter control method provided in this application embodiment;

[0047] Figure 3 An equivalent circuit diagram of the parasitic path when switch S is open, provided in an embodiment of this application;

[0048] Figure 4 An equivalent circuit diagram of the parasitic path when switch S is closed, provided in an embodiment of this application;

[0049] Figure 5 A circuit diagram of a three-phase grid-connected converter control circuit is also provided for embodiments of this application;

[0050] Figure 6A schematic diagram of a three-phase grid-connected converter control device provided in an embodiment of this application;

[0051] Figure 7 This is a structural diagram of a three-phase grid-connected converter control device provided in another embodiment of this application. Detailed Implementation

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0053] The core of this application is to provide a three-phase grid-connected converter control method, circuit, device, and medium to address the current non-isolated converter control methods for eliminating leakage current and common-mode voltage. It should be noted that the three-phase grid-connected converter control method provided in this application specifically refers to a low-leakage-current non-isolated three-phase grid-connected converter control method. This method primarily improves the photovoltaic inverter topology by adding an additional fourth bridge arm and employing an independent bridge arm control method based on inductor current feedback. This overcomes the contradiction that common-mode voltage and leakage current in three-phase converters cannot be simultaneously suppressed. However, the addition of extra switching devices leads to higher costs and power losses. Furthermore, due to the addition of the new bridge arm, this method cannot completely eliminate the leakage current problem of the photovoltaic inverter.

[0054] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Figure 2 A flowchart of a three-phase grid-connected converter control method provided in this application embodiment is shown below. Figure 1 As shown, the method includes:

[0056] S10: Obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation.

[0057] It should be noted that a converter is an electrical device that changes the voltage, frequency, number of phases, and other electrical quantities or characteristics of a power supply system. In practical applications, some situations require converting AC power to DC power, which is the function of a rectifier circuit. In other situations, it is necessary to convert DC power to AC power; this process, the reverse of rectification, is defined as an inverter circuit. Under certain conditions, a thyristor circuit can function as both a rectifier circuit and an inverter circuit; such a device is called a converter. Specific details regarding its construction can be found in the background section and will not be elaborated upon in this embodiment.

[0058] Changes in voltage and current transmitted through conductors occur in two forms, which we call "differential mode." Power lines for equipment, communication lines for telephones, and other communication lines exchanging signals with other devices or peripherals typically have at least two conductors. These two conductors act as round-trip lines to transmit power or signals. However, there is usually a third conductor in addition to these two conductors; this is the "ground wire." Interference voltage and current are divided into two types: one where two conductors act as round-trip lines respectively; and the other where two conductors act as the outgoing path and the ground wire acts as the return path. The former is called "common mode," and the latter is called "common-mode." In this embodiment, the acquisition device for obtaining the simulated waveform of this fluctuation characteristic is not specifically limited.

[0059] S11: When the midpoint of the filter capacitor and the common point of the lower bridge arm are connected, the voltage of the filter capacitor in the zero-sequence loop is controlled to be constant by the PI regulator, and the voltage of the filter capacitor is recorded.

[0060] It should be noted that, as Figure 1 As shown, the midpoint A of the filter capacitor is connected to the common point B of the lower bridge arm, and the zero sequence is controlled by a proportional-integral (PI) regulator at this time. The filter capacitor in the loop is a constant value. It should be noted that zero sequence is a ground fault detection method. It uses a sensor to connect all phase conductors and the neutral conductor together. The sensor generates an output proportional to the degree of imbalance of the ground fault current in the line. A relay measures this output and disconnects the circuit breaker or releases the ground fault alarm. In this embodiment, the specific type of PI regulator and the specific control method are not limited.

[0061] S12: Establish a dynamic mathematical model based on the grid-connected converter structure, and detect the grid phase angle of the grid-side voltage in the stationary coordinate system.

[0062] It should be noted that, in this embodiment, the specific parameters of the stationary coordinate system established for the common-mode voltage fluctuation are not elaborated. Since the establishment is based on the characteristics of the voltage fluctuation, the parameters are voltage and the corresponding time parameters.

[0063] S13: Obtain the modulation signal based on the filter capacitor voltage and the grid phase angle.

[0064] S14: Controls the bridge arm power switch transistors according to the modulation signal.

[0065] In summary, the three-phase grid-connected converter adopts a dual-loop control method with an outer voltage loop and an inner current loop. First, the three-phase grid voltages ea, eb, and ec in the stationary coordinate system are used to obtain the grid phase angle through a phase-locked loop. Based on the phase angle, the switch-side inductor current, filter capacitor voltage, and current in the stationary coordinate system are subjected to Parker transformation to obtain parameters in the synchronous rotating coordinate system. The DC bus voltage udc after rectification of the three-phase grid voltage by the grid-connected converter is compared with the control reference value udc. After PI regulation, the d-axis reference value of the switch-side inductor current is obtained and compared with the switch-side filter inductor current value after dq transformation to obtain the d-axis modulation ratio reference value. Similarly, the q-axis component of the switch-side filter inductor current is similar to the d-axis control structure to obtain the q-axis modulation ratio reference value. In addition, after comparing the zero-sequence component of the filter capacitor voltage with the control quantity, the zero-sequence reference value of the filter capacitor current can be obtained through the PI regulator. This value is then compared with the real-time acquired filter capacitor current to obtain the 0-axis modulation ratio reference value. Based on the phase angle, the obtained dq0-sequence modulation ratio is inversely transformed to obtain the modulation signal based on the three-phase stationary coordinate system, which is then applied to the power switching transistors of each phase bridge arm.

[0066] The three-phase grid-connected converter control method provided in this embodiment obtains the common-mode voltage and leakage current waveforms of the three-phase grid-connected converter through simulation, and combines the causes of leakage current generation and suppression mechanisms. Figure 3 An equivalent circuit diagram of the parasitic path when switch S is open, provided in an embodiment of this application. Figure 4 An equivalent circuit diagram of the parasitic path when switch S is closed is provided in an embodiment of this application, such as... Figure 3 and Figure 4 As shown, by establishing an equivalent circuit diagram of the leakage current parasitic path, zero-sequence control of the common-mode voltage is achieved. A PI regulator is used to control the voltage of the filter capacitor in the zero-sequence loop to a constant value, and the filter capacitor voltage is recorded. Based on the grid-connected converter structural model, its mathematical model is established in a three-phase stationary coordinate system. Using phase-locked loop (PLL) technology, the grid voltage phase angle is obtained in the three-phase stationary coordinate system. Based on this phase angle, a coordinate transformation is performed, converting the rotational quantity in the three-phase stationary coordinate system into a DC quantity in a synchronous rotating coordinate system. The transformed DC quantity is compared with the carrier signal to obtain the modulation signal. The power switching transistors in the grid-connected converter are then controlled based on the modulation signal. Since this scheme only requires adding a connecting wire between the midpoint of the filter capacitor and the common point of the lower bridge arm, the cost is low. Furthermore, since no other new bridge arm components are added, the leakage current caused by the parasitic capacitance to ground of the DC-side power distribution equipment is limited to the microampere level.

[0067] The above embodiments do not limit the specific method of obtaining the modulation signal. Here, a preferred solution is provided, in which the modulation signal is obtained based on the filter capacitor voltage and the power grid phase angle, including:

[0068] Based on the grid phase angle, the Parker transformation is performed on the switch-side inductor current, filter capacitor voltage, and filter capacitor current in the stationary coordinate system to obtain the parameters in the synchronous rotating coordinate system.

[0069] The zero-sequence component of the filter capacitor voltage is compared with the zero-sequence voltage reference value, and the zero-sequence reference value of the filter capacitor current is obtained through the PI regulator.

[0070] The modulation ratio is obtained by comparing the zero-sequence reference value with the filter capacitor current, and the modulation ratio is then inversely transformed to obtain the modulation signal.

[0071] It should be noted that the Parker transformation is one of the most commonly used coordinate transformations for analyzing the operation of synchronous motors. The Parker transformation projects the three-phase currents (a, b, c) of the stator onto the direct axis (d-axis), the quadrature axis (q-axis), and the zero axis (0-axis) perpendicular to the dq plane, which rotates with the rotor. This diagonalizes the stator inductance matrix, simplifying the analysis of synchronous motor operation. In other words, it transforms the abc coordinate system to the dq coordinate system. In this embodiment, by restricting the specific acquisition method of the modulation signal, the acquired data is made more accurate.

[0072] The above embodiments do not limit the method for obtaining common-mode voltage fluctuation characteristics. Here, a preferred solution is provided to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation, including:

[0073] The common-mode voltage fluctuation characteristics were obtained by observing the pulsating voltage on the DC-side parasitic capacitance and the leakage current generated by the pulsating voltage through Simulink simulation.

[0074] It should be noted that, in this embodiment, the specific method of obtaining the common-mode voltage characteristics is restricted, thereby making the obtained data more accurate.

[0075] Considering circuit safety issues, a preferred solution is provided here, which includes the following before controlling the bridge arm power switch transistors according to the modulation signal:

[0076] Detect whether the modulation signal meets the preset standard;

[0077] If so, proceed to the step of controlling the bridge arm power switch transistors according to the modulation signal;

[0078] If not, then trigger an alarm.

[0079] There are no restrictions on preset standards, alarm frequency, alarm time, etc.; they can be determined based on the actual situation.

[0080] This embodiment provides a method to detect whether the modulation signal meets a preset standard and to issue an alarm if the modulation signal does not meet the preset standard, allowing users to intuitively understand the circuit's status.

[0081] Figure 5 A circuit diagram of a three-phase grid-connected converter control circuit is also provided for embodiments of this application, such as... Figure 5 As shown, it includes: a three-phase AC power grid, an LCL filter, a three-phase voltage source rectifier, a DC bus and control switches, a detection device, and a controller;

[0082] The input terminal of the three-phase AC power grid is grounded, and the output terminal is connected to the input terminal of the LCL filter.

[0083] The output of the LCL filter is connected to the input of a three-phase voltage source rectifier.

[0084] The output of the three-phase voltage source rectifier is connected to the DC bus.

[0085] The control switch is located between the midpoint of the filter capacitor and the common point of the lower bridge arm.

[0086] The detection device is connected to the control switch. When the control switch is open, the detection device is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation. When the control switch is closed, the detection device controls the voltage of the filter capacitor in the zero-sequence loop to a constant value through the PI regulator and records the voltage of the filter capacitor. A dynamic mathematical model is established based on the structure of the grid-connected converter, and the grid phase angle of the grid-side voltage in the stationary coordinate system is detected. Based on the voltage of the filter capacitor and the grid phase angle, the modulation signal is obtained, and the bridge arm power switch is controlled according to the modulation signal.

[0087] Since the embodiments of the circuit section correspond to the embodiments of the method section, please refer to the description of the embodiments of the method section for the embodiments of the circuit section and their corresponding beneficial effects, which will not be repeated here. Furthermore, it has the same beneficial effects as the three-phase grid-connected converter control method mentioned above.

[0088] Considering the simulated state of parasitic capacitance, a preferred solution is provided here, which also includes: a positive DC bus capacitor and a negative DC bus capacitor;

[0089] One end of the positive DC bus capacitor is connected to the positive terminal of the DC bus, and the other end is grounded.

[0090] One end of the negative DC bus capacitor is connected to the negative terminal of the DC bus, and the other end is grounded.

[0091] The aforementioned capacitor is added to simulate the parasitic capacitance of the DC-side photovoltaic-storage-charging unit and the DC load to ground.

[0092] Considering the voltage stability in the circuit, a preferred solution is provided here, which also includes: a voltage stabilizing capacitor;

[0093] The voltage stabilizing capacitor is located between the DC bus and the common terminals of the upper and lower bridge arms of the three-phase voltage source rectifier.

[0094] In the above embodiments, the control method for a three-phase grid-connected converter has been described in detail. This application also provides embodiments corresponding to a three-phase grid-connected converter control device. It should be noted that this application describes the embodiments of the device part from two perspectives: one is based on the functional modules, and the other is based on the hardware.

[0095] Figure 6 A schematic diagram of a three-phase grid-connected converter control device provided in this application embodiment is shown. The device includes:

[0096] Simulation module 10 is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation;

[0097] The recording module 11 is used to connect the midpoint of the filter capacitor and the common point of the lower bridge arm, and to control the voltage of the filter capacitor in the zero-sequence loop to a constant value through the PI regulator, and to record the voltage of the filter capacitor.

[0098] The detection module 12 is used to establish a dynamic mathematical model based on the grid-connected converter structure and detect the grid phase angle of the grid-side voltage in the stationary coordinate system.

[0099] The acquisition module 13 is used to acquire the modulation signal based on the filter capacitor voltage and the grid phase angle;

[0100] Control module 14 is used to control the bridge arm power switching transistors according to the modulation signal.

[0101] Since the embodiments of the device section correspond to the embodiments of the method section, please refer to the description of the embodiments of the method section for the embodiments of the device section and their corresponding beneficial effects, which will not be repeated here. Furthermore, it has the same beneficial effects as the three-phase grid-connected converter control method mentioned above.

[0102] Figure 7 A structural diagram of a three-phase grid-connected converter control device provided in another embodiment of this application is shown below. Figure 7 As shown, the three-phase grid-connected converter control device includes: a memory 20 for storing computer programs;

[0103] The processor 21 is used to execute computer programs to implement the steps of the three-phase grid-connected converter control method mentioned in the above embodiments.

[0104] The processor 21 may include one or more processing cores, such as a quad-core processor or an octa-core processor. The processor 21 may be implemented using at least one hardware form of Digital Signal Processor (DSP), Field-Programmable Gate Array (FPGA), or Programmable Logic Array (PLA). The processor 21 may also include a main processor and a coprocessor. The main processor, also known as the Central Processing Unit (CPU), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, the processor 21 may integrate a Graphics Processing Unit (GPU), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, the processor 21 may also include an Artificial Intelligence (AI) processor, which is used to handle computational operations related to machine learning.

[0105] The memory 20 may include one or more computer-readable storage media, which may be non-transitory. The memory 20 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In this embodiment, the memory 20 is used to store at least the following computer program 201, which, after being loaded and executed by the processor 21, can implement the relevant steps of the three-phase grid-connected converter control method disclosed in any of the foregoing embodiments. In addition, the resources stored in the memory 20 may also include an operating system 202 and data 203, and the storage method may be temporary or permanent storage. The operating system 202 may include Windows, Unix, Linux, etc. The data 203 may include, but is not limited to, the data involved in the above-described three-phase grid-connected converter control method.

[0106] In some embodiments, the three-phase grid-connected converter control device may further include a display screen 22, an input / output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.

[0107] Those skilled in the art will understand that Figure 7 The structure shown does not constitute a limitation on the control device for a three-phase grid-connected converter and may include more or fewer components than shown.

[0108] The three-phase grid-connected converter control device provided in this application includes a memory and a processor. When the processor executes the program stored in the memory, it can implement the following method: the three-phase grid-connected converter control method involved in the above embodiments.

[0109] Since the embodiments of the apparatus and the embodiments of the method correspond to each other, please refer to the description of the embodiments of the method for the embodiments of the apparatus and their corresponding beneficial effects, which will not be repeated here.

[0110] Finally, this application also provides an embodiment corresponding to a computer-readable storage medium. The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps described in the above method embodiments.

[0111] It is understood that if the methods in the above embodiments are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or 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 executes all or part of the steps of the methods described in the various embodiments of this application. 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.

[0112] Since the embodiments of the readable storage medium portion correspond to the embodiments of the method portion, the embodiments of the apparatus portion and their corresponding beneficial effects are described in the description of the embodiments of the method portion, and will not be repeated here.

[0113] The foregoing has provided a detailed description of a three-phase grid-connected converter control method, circuit, apparatus, and medium provided in this application. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

[0114] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A control method for a three-phase grid-connected converter, characterized in that, include: The common-mode voltage fluctuation characteristics of the grid-connected converter were obtained through Simulink simulation. When the midpoint of the filter capacitor and the common point of the lower bridge arm are connected, the voltage of the filter capacitor in the zero-sequence loop is controlled to be constant by the PI regulator, and the voltage of the filter capacitor is recorded; wherein, a connecting wire is added between the midpoint of the filter capacitor and the common point of the lower bridge arm. A dynamic mathematical model is established based on the grid-connected converter structure, and the grid phase angle of the grid-side voltage in the stationary coordinate system is detected. The modulation signal is obtained based on the voltage of the filter capacitor and the phase angle of the power grid; Control the bridge arm power switch transistors according to the modulation signal; The step of obtaining the modulation signal based on the filter capacitor voltage and the power grid phase angle includes: Based on the grid phase angle, the Parker transformation is performed on the switch-side inductor current, the filter capacitor voltage, and the filter capacitor current in the stationary coordinate system to obtain the parameters in the synchronous rotating coordinate system. The zero-sequence component of the filter capacitor voltage is compared with the zero-sequence voltage reference value, and the zero-sequence reference value of the filter capacitor current is obtained through the PI regulator. The modulation ratio is obtained by comparing the zero-sequence reference value with the filter capacitor current, and the modulation ratio is then inversely transformed to obtain the modulation signal.

2. The three-phase grid-connected converter control method according to claim 1, characterized in that, The method of obtaining the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation includes: The common-mode voltage fluctuation characteristics are obtained by observing the pulsating voltage on the DC-side parasitic capacitor and the leakage current generated by the pulsating voltage through Simulink simulation.

3. The three-phase grid-connected converter control method according to claim 2, characterized in that, Before controlling the bridge arm power switch according to the modulation signal, the method further includes: Detect whether the modulated signal meets a preset standard; If so, proceed to the step of controlling the bridge arm power switch according to the modulation signal; If not, then trigger an alarm.

4. A control circuit for a three-phase grid-connected converter, characterized in that, include: Three-phase AC power grid, LCL filter, three-phase voltage source rectifier, DC bus and control switch, detection device; The input terminal of the three-phase AC power grid is grounded, and the output terminal is connected to the input terminal of the LCL filter. The output terminal of the LCL filter is connected to the input terminal of the three-phase voltage source rectifier. The output terminal of the three-phase voltage source rectifier is connected to the DC bus. The control switch is located between the midpoint of the filter capacitor and the common point of the lower bridge arm; a connecting wire is added between the midpoint of the filter capacitor and the common point of the lower bridge arm. The detection device is connected to the control switch. When the control switch is open, the detection device is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation. When the control switch is closed, the detection device controls the voltage of the filter capacitor in the zero-sequence loop to a constant value through a PI regulator and records the voltage of the filter capacitor. A dynamic mathematical model is established based on the grid-connected converter structure, and the grid phase angle of the grid-side voltage in the stationary coordinate system is detected. Based on the voltage of the filter capacitor and the grid phase angle, a modulation signal is obtained, and the bridge arm power switch is controlled based on the modulation signal. The step of obtaining the modulation signal based on the filter capacitor voltage and the power grid phase angle includes: Based on the grid phase angle, the Parker transformation is performed on the switch-side inductor current, the filter capacitor voltage, and the filter capacitor current in the stationary coordinate system to obtain the parameters in the synchronous rotating coordinate system. The zero-sequence component of the filter capacitor voltage is compared with the zero-sequence voltage reference value, and the zero-sequence reference value of the filter capacitor current is obtained through the PI regulator. The modulation ratio is obtained by comparing the zero-sequence reference value with the filter capacitor current, and the modulation ratio is then inversely transformed to obtain the modulation signal.

5. The three-phase grid-connected converter control circuit according to claim 4, characterized in that, It also includes: positive DC bus capacitor and negative DC bus capacitor; One end of the positive DC bus capacitor is connected to the positive terminal of the DC bus, and the other end is grounded. One end of the negative DC bus capacitor is connected to the negative terminal of the DC bus, and the other end is grounded.

6. The three-phase grid-connected converter control circuit according to claim 5, characterized in that, Also includes: Zener capacitor; The voltage stabilizing capacitor is located between the DC bus and the common terminals of the upper and lower bridge arms of the three-phase voltage source rectifier.

7. A three-phase grid-connected converter control device, characterized in that, include: The simulation module is used to obtain the common-mode voltage fluctuation characteristics of the grid-connected converter through Simulink simulation; A recording module is used to connect the midpoint of the filter capacitor and the common point of the lower bridge arm, and to control the voltage of the filter capacitor in the zero-sequence loop to a constant value through a PI regulator, and to record the voltage of the filter capacitor; wherein, a connecting wire is added between the midpoint of the filter capacitor and the common point of the lower bridge arm; The detection module is used to establish a dynamic mathematical model based on the grid-connected converter structure and detect the grid phase angle of the grid-side voltage in the stationary coordinate system. The acquisition module is used to acquire the modulation signal based on the voltage of the filter capacitor and the phase angle of the power grid; The control module is used to control the bridge arm power switching transistors according to the modulation signal; The acquisition module is specifically used for: Based on the grid phase angle, the Parker transformation is performed on the switch-side inductor current, the filter capacitor voltage, and the filter capacitor current in the stationary coordinate system to obtain the parameters in the synchronous rotating coordinate system. The zero-sequence component of the filter capacitor voltage is compared with the zero-sequence voltage reference value, and the zero-sequence reference value of the filter capacitor current is obtained through the PI regulator. The modulation ratio is obtained by comparing the zero-sequence reference value with the filter capacitor current, and the modulation ratio is then inversely transformed to obtain the modulation signal.

8. A control device for a three-phase grid-connected converter, characterized in that, Includes memory used to store computer programs; A processor, configured to execute the computer program to implement the steps of the three-phase grid-connected converter control method as described in any one of claims 1 to 3.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the three-phase grid-connected converter control method as described in any one of claims 1 to 3.

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