Improved three-phase current reconstruction method for meshed converter based on single current sensor

Abstract

The present disclosure provides an improved three-phase current reconstruction method for a meshed converter based on a single current sensor, which relates to the field of power electronics technology. The method comprises: based on a seven-segment SVPWM modulation strategy, sampling two symmetrically distributed sampling points once each within the effective vector interval of a switching cycle to obtain two sampling results; calculating the average value of the two sampling results for the same effective vector, and based on the average value of the sampling results, reconstructing two phases of the three-phase current on the inverter side according to the relationship between the DC current and the inverter side phase current during the turn-on or turn-off process of the switching device under different effective vectors, and then calculating the other phase through Kirchhoff's current law to obtain reconstructed inverter side current information; combining the reconstruction dead zone maintenance, first-order low-pass filtering and advance correction algorithm to reduce the influence of the reconstruction dead zone and achieve high-precision reconstruction of the inverter side current signal.

Description

Technical Field

[0001] The present disclosure relates to the field of power electronics technology, and in particular to an improved three-phase current reconstruction method for a grid-type converter based on a single current sensor. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] As core power electronics for renewable energy grid integration, grid-connected converters (GCCs) offer voltage and frequency regulation capabilities, providing auxiliary services such as inertia support and damping. Compared to traditional grid-connected converters, GCCs, with their phase self-synchronization capability, can achieve grid-connected operation without a phase-locked loop (PLL), and exhibit superior stability even in weak grid conditions.

[0004] However, existing meshed converters contain a large number of sensors, resulting in high cost and low reliability. At the same time, the control structure of the corresponding meshed converter is complex, and loop decoupling is difficult. Generally, the inverter-side current sensor is used for the current inner loop control and current limiting protection of the voltage / current dual closed loop, and the grid-side current sensor is used for power calculation. The traditional arrangement of six AC current sensors inevitably increases the cost and volume of the meshed converter, reducing its prospects for industrial application. In the field of motor control, a phase current reconstruction strategy based on DC current sensors is generally used to reconstruct the three-phase current on the inverter side, which is used to remove the inverter-side current sensors and reduce system costs. However, the mainstream phase current reconstruction strategy requires modifying the vector distribution of the SVPWM modulation strategy, which not only affects the performance of SVPWM modulation, but also increases switching harmonics. Its application effect in meshed converters needs further study. Summary of the Invention

[0005] In order to solve the above problems, the present disclosure proposes an improved three-phase current reconstruction method for a meshed converter based on a single current sensor. By improving the phase current reconstruction strategy, multi-sampling and averaging processing are performed on the effective vector within the switching cycle, thereby reducing the influence of the reconstruction error; combining the reconstruction dead zone maintenance, first-order low-pass filtering and advance correction algorithm, the influence of the reconstruction dead zone is reduced, and high-precision inverter side current signal reconstruction is achieved. On the basis of ensuring power calculation and fault current limiting protection, the AC current sensor is removed, reducing the system cost, volume and weight, and having the advantage of simple implementation.

[0006] According to some embodiments, the present disclosure adopts the following technical solutions:

[0007] An improved three-phase current reconstruction method for a meshed converter based on a single current sensor includes:

[0008] The current is sampled based on the seven-segment SVPWM modulation strategy. Two symmetrically distributed sampling points are sampled once each within the effective vector interval of the switching cycle to obtain two sampling results.

[0009] Calculate the average of two sampling results for the same effective vector. Based on the average sampling result, according to the relationship between the DC current and the inverter-side phase current during the switching device turning on or off under different effective vectors, that is, when the voltage rotating vector is located in a certain sector, synthesize the two effective vectors of the voltage rotating vector to correspond to the two phase currents respectively, reconstruct two of the three-phase phase currents on the inverter side, and then calculate the remaining phase using Kirchhoff's current law to obtain the reconstructed inverter-side current information;

[0010] Combining the reconstruction dead zone holding, first-order low-pass filtering and advance correction algorithm, the influence of the reconstruction dead zone is reduced and high-precision reconstruction of the inverter side current signal is achieved.

[0011] According to some embodiments, the present disclosure adopts the following technical solutions:

[0012] A computer program product comprises a computer program, wherein when the computer program is executed by a processor, the improved three-phase current reconstruction method of a grid-type converter based on a single current sensor is implemented.

[0013] According to some embodiments, the present disclosure adopts the following technical solutions:

[0014] A non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by a processor, the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor is implemented.

[0015] According to some embodiments, the present disclosure adopts the following technical solutions:

[0016] An electronic device comprises: a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The improved three-phase current reconstruction method of the meshed converter based on a single current sensor disclosed in the present invention includes a multi-sampling module, a sampling averaging module, a current reconstruction module, a dead zone holding module, a first-order low-pass filtering module, and an advance correction module. It improves the traditional phase current reconstruction strategy based on DC bus current information, removes the AC current sensor on the basis of ensuring the power calculation and fault current limiting protection of the meshed converter, and reduces the cost of the meshed converter.

[0019] The improved three-phase current reconstruction method of the meshed converter based on a single current sensor disclosed in the present invention has a reconstruction dead zone problem in the current reconstruction strategy adopted. This reconstruction dead zone problem will be eliminated by using a dead zone holding module, a first-order low-pass filtering module and an advance correction module. Among them, when the voltage rotation vector runs into the dead zone range at the edge of the SVPWM sector, the dead zone holding module keeps the current value of the reconstruction failure within the dead zone range equal to the current value of the normal reconstruction at the moment before entering the reconstruction dead zone range, thereby preventing the reconstruction failure within the dead zone range from causing a large jump in the reconstruction current value. The first-order low-pass filtering module will perform a first-order low-pass filtering on the reconstruction current result maintained in the reconstruction dead zone, thereby eliminating the waveform distortion caused by the dead zone holding. Furthermore, the advance correction module will perform advance correction on the reconstruction result after low-pass filtering to eliminate the phase delay introduced by the first-order low-pass filtering module.

[0020] The disclosed improved three-phase current reconstruction method for a meshed converter based on a single current sensor offers a simple implementation process, low hardware computational requirements, and high-quality reconstructed phase current waveforms. This method utilizes only a single DC current sensor. This eliminates the need for an AC current sensor, enabling power calculation and current-limiting protection for the meshed converter, reducing system costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the present disclosure, are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure.

[0022] Figure 1 Schematic diagram of the circuit structure of a three-phase grid-type converter according to an embodiment of the present disclosure;

[0023] Figure 2 Schematic diagram of the control structure of a three-phase grid-type converter according to an embodiment of the present disclosure;

[0024] Figure 3 A schematic flow chart of an improved phase current reconstruction method for a grid-type converter in accordance with an embodiment of the present disclosure, wherein the AC current sensor is removed;

[0025] Figure 4A schematic diagram of selecting effective sampling points of DC current during the turn-on process of a switching device corresponding to a specific effective vector according to an embodiment of the present disclosure;

[0026] Figure 5 Schematic diagram of the selection of four valid sampling points within the seven-segment SVPWM modulation vector distribution interval by the multi-sampling module according to an embodiment of the present disclosure;

[0027] Figure 6 Schematic diagram of a sampling and averaging module according to an embodiment of the present disclosure;

[0028] Figure 7 The corresponding relationship between the DC current and the inverter-side phase current under the action of six effective vectors in the embodiment of the present disclosure;

[0029] Figure 8 is the distribution range of the reconstruction dead zone in the traditional phase current reconstruction strategy of the embodiment of the present disclosure;

[0030] Figure 9 This is a simulation result comparing the inverter side phase current reconstructed when using the method of the present disclosure in an embodiment of the present disclosure with the actual phase current. DETAILED DESCRIPTION

[0031] The present disclosure will be further described below with reference to the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] Example 1

[0035] In one embodiment of the present disclosure, an improved three-phase current reconstruction method for a meshed converter based on a single current sensor is provided, which improves the traditional phase current reconstruction strategy based on DC bus current information. While ensuring the power calculation and fault current limiting protection of the meshed converter, the AC current sensor is removed, thereby reducing the cost of the meshed converter.

[0036] As an example, Figure 1The three-phase grid-type converter shown here contains six power semiconductor switching devices. S g1 - S g6 Three-phase LCL The filter consists of an inverter side inductor L gi , filter capacitor C gf and grid-side inductance L gg The power grid consists of an ideal voltage source v sabc and equivalent inductance L s Series composition. S g_relay In addition, the AC side sampling capacitor voltage in the grid-type converter topology is v gfabc Used for voltage inner loop control, sampling PCC voltage v gabc Used for grid pre-synchronization. DC side sampling DC bus current i gdc Used for phase current reconstruction and sampling DC voltage v gdc Used for duty cycle calculation.

[0037] Figure 2 The control structure of the three-phase grid-type converter is shown in Figure 2. The control structure consists of an outer power control loop and an inner voltage control loop. v gfabc and the reconstructed inverter side current i gi_recon The output active power is obtained through the power calculation module p g and reactive power q g Among them, active power control realizes active power reference value P gref Tracking and generating the system's phase adjustment ∆ θ g , reactive power control realizes reactive power reference value Q gref Tracking and generating the deviation adjustment value ∆ of the voltage reference value v gfd Phase-locked loop PCC voltage v gabc Get phase θ s , and ∆ θ g Added together, the phase of the system coordinate transformation is generated θg_ref The function of the voltage inner loop is to adjust the output capacitor voltage of the grid-type converter. v gfabc The amplitude and phase of PCC voltage v gabc pass abc / dq 0 coordinate transformation is obtained v gd and v gq , as the feedforward instruction. Finally, the duty cycle of the inner loop is modulated by SVPWM to generate the switching signal.

[0038] As an embodiment, based on Figure 1 and Figure 2 The grid circuit structure shown in FIG. 1 realizes an improved phase current reconstruction method for a three-phase meshed converter without an AC current sensor. The improved three-phase current reconstruction method for a meshed converter based on a single current sensor disclosed in the present invention is proposed. The method steps include:

[0039] Step 1: Sampling the current. Based on the seven-segment SVPWM modulation strategy, two symmetrically distributed sampling points are sampled once each within the effective vector interval of the switching cycle to obtain two sampling results.

[0040] Step 2: Calculate the average of the two sampling results of the same effective vector. Based on the average of the sampling results, according to the relationship between the DC current and the inverter side phase current during the opening or closing process of the switching device under different effective vectors, that is, when the voltage rotating vector is located in a certain sector, the two effective vectors of the synthesized voltage rotating vector correspond to the two-phase currents respectively, and two of the three-phase phase currents on the inverter side are reconstructed. Then, the other phase is calculated using Kirchhoff's current law to obtain the reconstructed inverter side current information.

[0041] As an embodiment, the specific implementation process of the improved three-phase AC current reconstruction method of the grid-type converter disclosed in the present invention is as follows: Figure 3 As shown in FIG, the improved three-phase AC current reconstruction method for the grid-type converter is implemented by a multi-sampling module, a sampling averaging module, a current reconstruction module, a dead zone holding module, a first-order low-pass filtering module, and a lead correction module. It includes the following processes:

[0042] 1) The multi-sampling module performs sampling. Based on a seven-segment SVPWM modulation design, the module samples once within each active vector interval within the switching cycle. The sampling points within the symmetrically distributed intervals of the same active vector within the switching cycle are symmetrical with respect to the carrier midpoint. The sampling point can be the midpoint of the active vector interval or other feasible sampling points.

[0043] The feasible sampling time of the multi-sampling module needs to be greater than the minimum sampling window timeT min The minimum sampling window time is determined by the dead time of the switching device. T d , the rise and stabilization time of the DC current after the switching device is turned on T up , and the sample and hold time of the ADC module T hold Composition (see Figure 4 ).

[0044] Figure 4 Schematic diagram for selecting effective sampling points of DC current during the on-state of the switching device corresponding to a specific effective vector. Figure 4 As shown, when the turn-on pulse of the upper bridge arm switch device of phase A or phase B is triggered, the feasible sampling start time needs to be greater than the minimum sampling window time T min The minimum sampling window time is determined by the dead time of the switching device. T d , the rise and stabilization time of the DC current after the switching device is turned on T up , and the sample and hold time of the ADC module T hold If the sampling point setting time is less than T min ,Within the non-reconstruction dead zone of the sector, the sampling result ,has a large error, which leads to the distortion of the final current ,reconstruction result.

[0045] Figure 5 The figure is a schematic diagram of the selection of four effective sampling points in the seven-segment SVPWM modulation vector distribution interval by the multi-sampling module. Figure 5 As shown, each sampling is performed once in the effective vector interval in the switching cycle, and at the same time, the sampling points of the symmetrical distribution interval of the same effective vector in the switching cycle are symmetrical relative to the midpoint of the carrier. The sampling point can be the midpoint of the effective vector interval, or other feasible sampling points can be selected. Figure 5 In the example, we take the midpoint of the valid vector as an example. t sa1 、 t sa2 、 t sa3 、 t sa4 is the sampling point time within the corresponding four valid vector intervals.

[0046] As an embodiment, the present disclosure takes the midpoint of the sampling effective vector as an example, and samples two symmetrically distributed sampling points once each within the effective vector interval of the switching cycle to obtain two sampling results.

[0047] 2) Use the sampling average module to calculate the average value of two sampling results of the same valid vector based on the multi-sampling module i sp1 、 i sp2 .

[0048] Figure 6 This is the schematic diagram of the sampling and averaging module. Figure 6 As shown, by averaging the symmetrical sampling results of the same effective vector, the DC current sampling average results corresponding to the two effective vectors in the switching cycle are obtained. i sp1 、 i sp2 ,This method can reduce the reconstruction error caused by inconsistent ,sampling time.

[0049] 3) Based on the relationship between the DC current and the inverter-side phase current during the on / off process of the switching device under different effective vectors, that is, when the voltage rotating vector is located within a certain sector, the two effective vectors of the voltage rotating vector are synthesized to correspond to the two-phase currents, respectively, to reconstruct two of the three-phase inverter-side currents. The remaining phase is then calculated using Kirchhoff's current law to obtain the reconstructed inverter-side current information;

[0050] Afterwards, the time constant of the first-order low-pass filter module is adjusted according to the waveform quality of the reconstructed inverter-side current. When the waveform quality of the reconstructed inverter-side current is poor, the time constant of the low-pass filter is increased.

[0051] Specifically, if Figure 7 As shown in the figure, the corresponding relationship between DC current and inverter side phase current under the action of six effective vectors is shown. i gdc The corresponding inverter side phase currents are different, and the effective vector V 1 DC current during action i gdc Equal to the inverter side a Phase current+ i gia , effective vector V 2 DC current during action i gdc Equal to the inverter side c Negative value of phase current − i gic , effective vector V 3 DC current during action i gdc Equal to the inverter side b Phase current+ i gib , effective vector V4 DC current during action i gdc Equal to the inverter side a Negative value of phase current − i gia , effective vector V 5 DC current during action i gdc Equal to the inverter side c Phase current+ i gic , effective vector V 6 DC current during action i gdc Equal to the inverter side b Negative value of phase current − i gib .

[0052] However, the current reconstruction strategy adopted by the current reconstruction module has the problem of reconstruction dead zone. The distribution of reconstruction dead zone is shown in Figure 8 .like Figure 8 As shown, taking sector I as an example, the effective vector V 1 and V 2 Synthesize the rotating voltage vector within this interval. When the effective vector V The action time of 1 is less than 2 T min , V 1 The corresponding DC current cannot be accurately collected, resulting in the failure of the phase current reconstruction; when the effective vector V The action time of 2 is less than 2 T min , V 2 The corresponding DC current cannot be accurately collected, resulting in the failure of the phase current reconstruction; when the effective vector V 1 and V The action time of 2 is less than 2 T min , V 1 and V 2. The corresponding DC currents cannot be accurately collected, resulting in the failure of reconstruction of all three-phase currents.

[0053] The dead zone problem of the reconstruction disclosed in this invention will be eliminated by using the dead zone holding module, the first-order low-pass filter module and the advance correction module. T min within the time (according to T minThe dead-zone retention angle range is calculated based on the switching period. The dead-zone retention module maintains the current value of the failed reconstruction within the dead-zone equal to the current value of the normal reconstruction immediately before entering the reconstruction dead-zone. The time constant, correction coefficient, and amplitude coefficient of the lead correction module are designed based on the phase lag caused by the time constant of the first-order low-pass filter module at the rated frequency and the principle of ensuring that the amplitude at the rated frequency remains unchanged.

[0054] Specifically, the three-phase current reconstruction value of the inverter side is obtained through the current reconstruction module i gi_rec . When determining the minimum sampling window time T min Based on (can be based on T min The angle range corresponding to the minimum sampling window is calculated based on the switching period. The reconstructed dead zone of the reconstructed current information is maintained, and the current value within the dead zone where reconstruction fails is kept equal to the normal reconstructed current value immediately before entering the reconstruction dead zone. Furthermore, the transfer function of the first-order low-pass filter can be expressed as:

[0055] (1)

[0056] in, T LPF is the time constant of the first-order low-pass filter. This time constant can be adjusted based on the quality of the reconstructed inverter-side current waveform. When the reconstructed inverter-side current waveform quality is poor, the time constant can be increased to improve the waveform quality.

[0057] In general, the transfer function of the lead correction module can be expressed as:

[0058] (2)

[0059] in, T c is the time constant of the lead correction module, a is the correction factor, k c is the amplitude coefficient, let ω 1= 1 / ( aT c ), ω 2= ​​1 / T c , maximum leading angular frequency ω m and maximum lead phase angle φ m Respectively expressed as:

[0060] (3)

[0061] (4)

[0062] The absolute value of the phase lag of the transfer function of the first-order low-pass filter at the rated frequency can be used to obtain the maximum leading phase angle, which can then be calculated. a Since the reconstructed phase current is expected to have good waveform quality at the rated frequency, it can be assumed that the maximum leading angular frequency ω m Equal to the rated angular frequency ω 0, and then calculate ω 1 and ω 2. Order | G LPF ( j ω 0) G c ( jω 0)| = 1, find the amplitude scaling factor of the correction module k c , and finally the transfer function of the advance correction module is obtained, which is expressed as follows:

[0063] (5)

[0064] As an example, Figure 9 The figure shows the simulation results comparing the inverter-side phase current reconstructed using the disclosed method with the actual phase current. The phase current waveform reconstructed using the improved phase current reconstruction method described in this disclosure has good quality and low harmonic content, and can replace the actual sampled phase current for power calculation and current limiting protection.

[0065] Example 2

[0066] In one embodiment of the present disclosure, a three-phase AC current reconstruction system using a grid-type converter is provided, comprising:

[0067] The multi-sampling module is used to sample the current. Based on the seven-segment SVPWM modulation strategy, two symmetrically distributed sampling points are sampled once each within the effective vector interval of the switching cycle to obtain two sampling results.

[0068] The sampling average module is used to calculate the average value of two sampling results of the same valid vector;

[0069] The current reconstruction module is used to reconstruct the phase current. Based on the average value of the sampling results and the relationship between the DC current and the inverter-side phase current during the on- or off-state of the switching device under different effective vectors, when the voltage rotating vector is located in a certain sector, the two effective vectors of the synthesized voltage rotating vector correspond to the two-phase currents, respectively, and two of the three-phase phase currents on the inverter side are reconstructed. The remaining phase is then calculated using Kirchhoff's current law to obtain the reconstructed inverter-side current information.

[0070] The first-order low-pass filter module and the advance correction module are used to improve the waveform quality of the reconstructed current. By adjusting the time constant of the first-order low-pass filter and assisting with the advance correction module, the waveform quality of the three-phase reconstructed current information can be improved and the waveform distortion introduced by the reconstruction dead zone can be eliminated.

[0071] Example 3

[0072] In one embodiment of the present disclosure, a computer program product is provided, including a computer program, which, when executed by a processor, implements the improved three-phase AC current reconstruction method for a grid-type converter.

[0073] Example 4

[0074] In one embodiment of the present disclosure, a non-transitory computer-readable storage medium is provided, which is used to store computer instructions. When the computer instructions are executed by a processor, the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor is implemented.

[0075] Example 5

[0076] In one embodiment of the present disclosure, an electronic device is provided, comprising: a processor, a memory, and a computer program; wherein the processor is connected to the memory, and the computer program is stored in the memory. When the electronic device is running, the processor executes the computer program stored in the memory, so that the electronic device executes the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor.

[0077] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0078] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0079] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Those skilled in the art should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. An improved three-phase current reconstruction method based on a grid-type converter with a single current sensor is characterized in that: include: The DC bus current is sampled based on the seven-segment SVPWM modulation strategy. Two symmetrically distributed sampling points are sampled once each within the effective vector interval of the switching cycle to obtain two sampling results. Calculate the average of two sampling results for the same effective vector. Based on the average sampling result, according to the relationship between the DC current and the inverter-side phase current during the on- or off-state of the switching device under different effective vectors, that is, when the voltage rotating vector is located in a certain sector, synthesize the two effective vectors of the voltage rotating vector to correspond to the phase currents of two phases, reconstruct two of the three-phase phase currents on the inverter side, and then calculate the remaining phase using Kirchhoff's current law to obtain the reconstructed inverter-side current information; Combining dead zone holding, first-order low-pass filtering and advance correction algorithm, the impact of reconstruction dead zone is reduced and high-precision inverter side current signal reconstruction is achieved; When the voltage rotation vector runs to the sector edge before and after the time, the dead zone holding module keeps the current value of the reconstruction failure within the dead zone range equal to the current value of the normal reconstruction before entering the reconstruction dead zone range.

2. The improved three-phase current reconstruction method for a meshed converter based on a single current sensor according to claim 1, characterized in that: During sampling, the sampling time must be greater than the minimum sampling window time. The minimum sampling window time is composed of the dead time of the switching device, the rise and stabilization time of the DC current after the switching device is turned on, and the sampling and holding time of the ADC module.

3. The improved three-phase current reconstruction method for a grid-type converter based on a single current sensor according to claim 1, characterized in that: Based on the seven-segment SVPWM modulation strategy, sampling is performed once in each effective vector interval of the switching cycle. At the same time, the sampling points of the symmetrically distributed interval of the same effective vector within the switching cycle are guaranteed to be symmetrical relative to the midpoint of the carrier. The sampling point is selected as the midpoint of the effective vector interval, and the average of the two sampling results of the same effective vector is calculated.

4. The improved three-phase current reconstruction method for a grid-type converter based on a single current sensor according to claim 1, characterized in that: A current reconstruction strategy is adopted to reconstruct the inverter side current information based on the relationship between the DC current and the inverter side phase current during the opening or closing process of the switching device under different effective vectors. The current reconstruction strategy has a reconstruction dead zone problem, which will be eliminated by using a dead zone holding module, a first-order low-pass filter module and an advance correction module.

5. The improved three-phase current reconstruction method of a grid-type converter based on a single current sensor according to claim 1, characterized in that: The time constant of the first-order low-pass filter module is adjusted according to the waveform quality of the reconstructed inverter-side current. When the waveform quality of the reconstructed inverter-side current is poor, the time constant of the low-pass filter is increased.

6. The improved three-phase current reconstruction method of a grid-type converter based on a single current sensor according to claim 1, characterized in that: The time constant, correction coefficient and amplitude coefficient of the lead correction module are designed and determined based on the lagging phase caused by the time constant of the first-order low-pass filter module at the rated frequency and the principle of ensuring the amplitude remains unchanged at the rated frequency.

7. The improved three-phase current reconstruction method of a grid-type converter based on a single current sensor according to claim 6, characterized in that: The transfer function of a first-order low-pass filter can be expressed as: in, T LPF It is the time constant of the first-order low-pass filter. The time constant can be adjusted according to the waveform quality of the reconstructed inverter-side current. When the waveform quality of the reconstructed inverter-side current is poor, the waveform quality can be improved by increasing the time constant.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the improved three-phase current reconstruction method of a meshed converter based on a single current sensor as described in any one of claims 1 to 7 is implemented.

9. A non-transitory computer-readable storage medium, characterized in that The non-transitory computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by the processor, the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor as described in any one of claims 1 to 7 is implemented.

10. An electronic device, characterized in that: include: A processor, a memory, and a computer program; wherein the processor is connected to the memory, the computer program is stored in the memory, and when the electronic device is running, the processor executes the computer program stored in the memory to enable the electronic device to implement the improved three-phase current reconstruction method of the grid-type converter based on a single current sensor as described in any one of claims 1 to 7.

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