Improved three-phase current reconstruction method for network-building type converter based on single current sensor

Abstract

The invention provides an improved three-phase current reconstruction method for a network-building type converter based on a single current sensor, and relates to the technical field of power electronics, and the method comprises the steps: carrying out the sampling of two symmetrically-distributed sampling points once in an effective vector interval of a switching period based on a seven-segment SVPWM modulation strategy, and obtaining two sampling results; calculating an average value of two sampling results of the same effective vector, reconstructing two phases of three-phase current of the inverter side according to the relation between the direct current and the phase current of the inverter side in the switching-on or switching-off process of the switching device under different effective vectors on the basis of the average value of the sampling results, and calculating the other phase according to the Kirchhoff's current law; reconstructed inverter side current information is obtained; reconstruction dead zone keeping, first-order low-pass filtering and a lead correction algorithm are combined, the influence of a reconstruction dead zone is reduced, and high-precision inversion side current signal reconstruction is achieved.

Description

Technical Field

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

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

[0003] As the core power electronic equipment for new energy grid connection, the network-forming converter has the ability of voltage regulation / frequency modulation and can provide auxiliary services such as inertia support and damping for the power grid. Compared with the traditional grid-following converter, the network-forming converter can achieve grid connection operation without a phase-locked loop by virtue of its phase self-synchronization ability, and shows better stability under weak grids.

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

[0005] To solve the above problems, the present disclosure proposes an improved three-phase current reconstruction method for a network-forming converter based on a single current sensor. By improving the phase current reconstruction strategy, multi-sampling and mean processing are performed on the effective vectors within the switching period, reducing the influence of the reconstruction error; combined with the reconstruction dead zone hold, first-order low-pass filtering, and lead correction algorithms, the influence of the reconstruction dead zone is reduced, and high-precision reconstruction of the inverter-side current signal 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: An improved three-phase current reconstruction method for a network-forming converter based on a single current sensor, comprising: Sample the current. Based on the seven-segment SVPWM modulation strategy, sample each of the two symmetrically distributed sampling points once within the effective vector interval of the switching period to obtain two sampling results; Calculate the average value of the two sampling results of the same effective vector. Based on the average value of the sampling results, according to the relationship between the DC current and the inverter-side phase current during the on or off process of the switching device under different effective vectors, that is, when the voltage rotation vector is located in a certain sector, the two effective vectors synthesizing the voltage rotation vector respectively correspond to two-phase currents. Reconstruct two of the three-phase currents on the inverter side, and then calculate the other phase through Kirchhoff's current law to obtain the reconstructed current information on the inverter side; Combine the reconstructed dead-time hold, first-order low-pass filtering, and lead compensation algorithms to reduce the influence of the reconstructed dead-time and achieve high-precision reconstruction of the inverter-side current signal.

[0007] According to some embodiments, the present disclosure adopts the following technical solutions: A computer program product includes a computer program, and when the computer program is executed by a processor, it implements the improved three-phase current reconstruction method for a network-forming converter based on a single current sensor.

[0008] According to some embodiments, the present disclosure adopts the following technical solutions: A non-transitory computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, they implement the improved three-phase current reconstruction method for a network-forming converter based on a single current sensor.

[0009] According to some embodiments, the present disclosure adopts the following technical solutions: An electronic device includes: 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 runs, the processor executes the computer program stored in the memory so that the electronic device executes and implements the improved three-phase current reconstruction method for a network-forming converter based on a single current sensor.

[0010] Compared with the prior art, the beneficial effects of the present disclosure are: The improved three-phase current reconstruction method for a network-forming converter based on a single current sensor in the present disclosure includes a multi-sampling module, a sampling average module, a current reconstruction module, a dead-time hold module, a first-order low-pass filtering module, and a lead compensation module. It improves the traditional phase current reconstruction strategy based on DC bus current information, removes the AC current sensor while ensuring the power calculation and fault current limiting protection of the network-forming converter, and reduces the cost of the network-forming converter.

[0011] The improved three-phase current reconstruction method of the network-forming converter based on a single current sensor in the present disclosure has a reconstruction dead zone problem in the adopted current reconstruction strategy. This reconstruction dead zone problem will be eliminated by using a dead zone holding module, a first-order low-pass filtering module, and a lead correction module. Among them, when the voltage rotation vector runs to the dead zone range at the edge of the SVPWM sector, the dead zone holding module keeps the reconstructed current value that fails within the dead zone equal to the normally reconstructed current value at the moment before entering the reconstruction dead zone, thereby preventing a large jump in the reconstructed current value due to the failure within the dead zone. The first-order low-pass filtering module will perform first-order low-pass filtering on the reconstructed current result held by the reconstruction dead zone, so as to eliminate the waveform distortion caused by the dead zone holding. Further, the lead correction module will perform lead correction on the reconstructed result after low-pass filtering to eliminate the phase delay introduced by the first-order low-pass filtering module.

[0012] The improved three-phase current reconstruction method of the network-forming converter based on a single current sensor in the present disclosure has a simple implementation process, low computational requirements for hardware, good quality of the reconstructed phase current waveform, and only adds a DC current sensor. On the basis of removing the AC current sensor, the power calculation and current limiting protection functions of the network-forming converter are realized, reducing the system cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The specification drawings forming a part of the present disclosure are used to provide a further understanding of the present disclosure. The schematic embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure.

[0014] Figure 1 is a schematic circuit structure diagram of a three-phase network-forming converter according to an embodiment of the present disclosure; Figure 2 is a schematic control structure diagram of a three-phase network-forming converter according to an embodiment of the present disclosure; Figure 3 is a schematic flow diagram of an improved phase current reconstruction method for a network-forming converter removing an AC current sensor according to an embodiment of the present disclosure; Figure 4 is a schematic diagram of the selection of 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; Figure 5 is a schematic diagram of the selection of four effective sampling points of a multi-sampling module within the seven-segment SVPWM modulation vector distribution interval according to an embodiment of the present disclosure; Figure 6 is a schematic diagram of the principle of a sampling average module according to an embodiment of the present disclosure; Figure 7 is the corresponding relationship between DC current and inverter-side phase current under the action of six effective vectors according to an embodiment of the present disclosure; Figure 8The distribution range of the reconstructed dead zone in the traditional phase current reconstruction strategy of the embodiment of the present disclosure; Figure 9 The comparative simulation results of the reconstructed phase current on the inverter side and the actual phase current when using the method of the present disclosure in the embodiment of the present disclosure. Specific embodiments

[0015] The present disclosure will be further described below in conjunction with the accompanying drawings and embodiments.

[0016] It should be noted that the following detailed description is illustrative and is intended to provide further description of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs.

[0017] 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 also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0018] Embodiment 1 In an embodiment of the present disclosure, an improved three-phase current reconstruction method for a network-forming converter based on a single current sensor is provided, which 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 network-forming converter, and reduces the cost of the network-forming converter.

[0019] As an embodiment, as Figure 1 shown is a three-phase network-forming converter, which includes 6 power semiconductor switching devices S g1 - S g6 . The three-phase LCL filter is composed of the inductor L gi on the inverter side, the filter capacitor C gf , and the inductor L gg on the grid side. The power grid is composed of an ideal voltage source v sabc and an equivalent inductor L s connected in series. S g_relay is a three-phase AC relay. In addition, the AC side sampling capacitor voltage v gfabcFor voltage inner-loop control, sample the PCC voltage v gabc For grid-connected pre-synchronization. Sample the DC bus current on the DC side i gdc For phase current reconstruction, sample the DC voltage v gdc For duty cycle calculation.

[0020] Figure 2 It is a schematic diagram of the control structure of a three-phase grid-forming converter. The control structure consists of an outer power control loop and an inner voltage control loop. The sampled capacitor voltage v gfabc and the reconstructed current on the inverter side i gi_recon pass through the power calculation module to obtain the output active power p g and reactive power q g . Among them, the active control realizes the tracking of the active reference value P gref and generates the phase adjustment amount ∆ θ g of the system, and the reactive control realizes the tracking of the reactive reference value Q gref and generates the deviation adjustment amount ∆ v gfd of the voltage reference value. The phase-locked loop locks the PCC voltage v gabc to obtain the phase θ s , which is added to ∆ θ g to generate the phase θ g_ref for system coordinate transformation. The function of the voltage inner loop is to adjust the amplitude and phase of the output capacitor voltage v gfabc of the grid-forming converter. The PCC voltage v gabc is transformed through abc / dq 0 coordinate transformation to obtain v gd and v gq , which are used as feedforward commands. Finally, the duty cycle of the inner loop generates switching signals through SVPWM modulation.

[0021] As an embodiment, based on Figure 1 and Figure 2The shown power grid circuit structure realizes an improved phase current reconstruction method for a three-phase grid-forming converter to remove an AC current sensor, and proposes an improved three-phase current reconstruction method for a grid-forming converter based on a single current sensor. The method steps include: Step 1: Sample the current. Based on the seven-segment SVPWM modulation strategy, sample each of the two symmetrically distributed sampling points once within the effective vector interval of the switching period to obtain two sampling results; Step 2: Calculate the average value of the two sampling results of the same effective vector. Based on the average value of the sampling results, according to the relationship between the DC current and the inverter-side phase current during the on or off process of the switching device under different effective vectors, that is, when the voltage rotation vector is located in a certain sector, the two effective vectors synthesizing the voltage rotation vector respectively correspond to two-phase phase currents, reconstruct two of the three-phase phase currents on the inverter side, and then calculate the other phase through Kirchhoff's current law to obtain the reconstructed current information on the inverter side.

[0022] As an embodiment, the specific implementation process of the improved three-phase AC current reconstruction method for the grid-forming converter of the present disclosure is as Figure 3 shown. The improved three-phase AC current reconstruction method for the grid-forming converter is implemented by a multi-sampling module, a sampling average module, a current reconstruction module, a dead zone holding module, a first-order low-pass filter module, and a lead compensation module. The following processes are included: 1) The multi-sampling module performs sampling. The multi-sampling module is designed based on the seven-segment SVPWM modulation, and samples once within the effective vector interval of the switching period, while ensuring that the sampling points in the symmetric distribution interval of the same effective vector within the switching period are symmetric with respect to the carrier midpoint. The sampling point can be selected as the midpoint of the effective vector interval or other feasible sampling points.

[0023] The feasible sampling moment of the multi-sampling module needs to meet the requirement of being greater than the minimum sampling window time T min . This minimum sampling window time is composed of the dead zone time T d of the switching device, the rising and stabilizing time of the DC current after the switching device is turned on T up , and the sampling and holding time of the ADC module T hold (see Figure 4 ).

[0024] Figure 4 is a schematic diagram of the selection of the effective sampling point of the DC current during the on process of the switching device corresponding to a specific effective vector. As Figure 4 shown, when the on pulse of the switching device on the upper bridge arm of phase A or phase B is triggered, the feasible sampling start moment needs to meet the requirement of being greater than the minimum sampling window timeT min requirements. The minimum sampling window time consists of 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 moment is less than T min , within the non-reconstruction dead zone of the sector, the sampling result error is large, resulting in distortion of the final current reconstruction result.

[0025] Figure 5 FIG. is a schematic diagram of the selection of four effective sampling points within the vector distribution interval of the seven-segment SVPWM modulation. As Figure 5 shown, samples are taken once in each effective vector interval during the switching period, and at the same time, it is ensured that the sampling points in the symmetric distribution interval of the same effective vector within the switching period are symmetric with respect to the carrier midpoint. The sampling point can be selected as the midpoint of the effective vector interval, or other feasible sampling points can be selected. Figure 5 In, the midpoint of the sampling effective vector is taken as an example. t sa1 , t sa2 , t sa3 , t sa4 are the sampling point moments within the corresponding four effective vector intervals.

[0026] As an embodiment, the present disclosure takes the midpoint of the sampling effective vector as an example, and samples each of the two symmetric sampling points within the effective vector interval of the switching period to obtain two sampling results.

[0027] 2) Use the sampling average module to calculate the average value of the two sampling results of the same effective vector based on the multi-sampling module i sp1 , i sp2 .

[0028] Figure 6 FIG. is the schematic diagram of the sampling average module. As Figure 6 shown, by averaging the symmetric sampling results of the same effective vector, the sampled average results of the DC current corresponding to the two effective vectors within the switching period are obtained i sp1 , i sp2 , and this method can reduce the reconstruction error caused by inconsistent sampling moments.

[0029] 3) According to the relationship between the DC current and the phase current on the inverter side during the turn-on or turn-off process of the switching device under different effective vectors, that is, when the voltage rotation vector is located in a certain sector, the two effective vectors synthesizing the voltage rotation vector respectively correspond to two-phase currents. Reconstruct two of the three-phase currents on the inverter side, and then calculate the other phase through Kirchhoff's current law to obtain the reconstructed current information on the inverter side; After that, the time constant of the first-order low-pass filter module is adjusted according to the waveform quality of the reconstructed current on the inverter side. When the waveform quality of the reconstructed current on the inverter side is poor, the time constant of the low-pass filter is increased.

[0030] Specifically, as Figure 7 shown, it shows the corresponding relationship between the DC current and the phase current on the inverter side under the action of six effective vectors. The DC current i gdc corresponding to different effective vectors is different. During the action of effective vector V 1, the DC current i gdc is equal to the phase current on the inverter side a plus i gia . During the action of effective vector V 2, the DC current i gdc is equal to the negative value of the phase current on the inverter side c minus i gic . During the action of effective vector V 3, the DC current i gdc is equal to the phase current on the inverter side b plus i gib . During the action of effective vector V 4, the DC current i gdc is equal to the negative value of the phase current on the inverter side a minus i gia . During the action of effective vector V 5, the DC current i gdc is equal to the phase current on the inverter side c plus i gic . During the action of effective vector V 6, the DC current i gdc is equal to the negative value of the phase current on the inverter side b minus i gib .

[0031] However, there is a problem of reconstruction dead zone in the current reconstruction strategy adopted by the current reconstruction module. The distribution of the reconstruction dead zone is shown in Figure 8 . As Figure 8 shown, taking Sector I as an example, the effective vectors V 1 and V 2 synthesize the rotating voltage vector within this interval. When the action time of the effective vector V 1 within the switching period is less than 2 T min , V the DC current corresponding to 1 cannot be accurately collected, resulting in the failure of the current reconstruction of this phase; when the action time of the effective vector V 2 within the switching period is less than 2 T min , V the DC current corresponding to 2 cannot be accurately collected, resulting in the failure of the current reconstruction of this phase; when the action times of the effective vectors V 1 and V 2 within the switching period are both less than 2 T min , V the DC currents corresponding to 1 and V 2 cannot be accurately collected, resulting in the failure of the reconstruction of all three-phase currents.

[0032] The reconstruction dead zone problem of the present disclosure will be eliminated by using a dead zone holding module, a first-order low-pass filter module, and a lead compensation module. When the voltage rotating vector runs around the sector edge T min within a certain time (the angle range of dead zone holding can be calculated according to T min and the switching period), the dead zone holding module keeps the reconstructed current value that fails within the dead zone equal to the normally reconstructed current value at the previous moment before entering the reconstruction dead zone. According to the lag 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, the time constant, correction coefficient, and amplitude coefficient of the lead compensation module are designed and determined.

[0033] Specifically, the reconstructed values of the three-phase currents on the inverter side are obtained through the current reconstruction module i gi_rec . On the basis of determining the minimum sampling window time T min (the angle range corresponding to the minimum sampling window can be calculated according to T min and the switching period), the reconstruction dead zone of the reconstructed current information is held, and the reconstructed current value that fails within the dead zone is kept equal to the normal reconstructed current value at the previous moment before entering the reconstruction dead zone. Further, the transfer function of the first-order low-pass filter can be expressed as: (1) Among them, T LPF is the time constant of the first-order low-pass filter. This time constant can be adjusted according to the waveform quality of the reconstructed current on the inverter side. When the waveform quality of the reconstructed current on the inverter side is poor, the time constant can be increased to improve the waveform quality.

[0034] Generally, the transfer function of the lead compensation module can be expressed as: (2) Among them, T c is the time constant of the lead compensation module, a is the correction coefficient, k c is the amplitude coefficient. Let ω 1 = 1 / ( aT c ), ω 2 = 1 / T c , the maximum lead angular frequency ω m and the maximum lead phase angle φ m are respectively expressed as: (3) (4) Taking the absolute value of the phase lag of the transfer function of the first-order low-pass filter at the rated frequency can obtain the maximum lead phase angle, and then a can be calculated. Since the reconstructed phase current is expected to have good waveform quality at the rated frequency, it can be assumed that the maximum lead angular frequency ω m is equal to the rated angular frequency ω 0, and then ω 1 and ω 2 are calculated. Let | G LPF ( j ω 0) G c ( jω 0) | = 1, and the amplitude scaling coefficient k c of the compensation module is obtained. Finally, the transfer function of the lead compensation module is obtained and expressed as follows: (5) As an embodiment, such as Figure 9As shown, the comparative simulation results of the reconstructed inverter-side phase current and the actual phase current when using the method of the present disclosure are presented. The phase current waveform reconstructed by the improved phase current reconstruction method described in the present disclosure has good quality and low harmonic content, and can replace the sampled actual phase current for power calculation and current-limiting protection.

[0035] Embodiment 2 In one embodiment of the present disclosure, an improved three-phase AC current reconstruction system for a network-forming converter is provided, including: A multi-sampling module for sampling the current. Based on the seven-segment SVPWM modulation strategy, two sampling points symmetrically distributed are each sampled once within the effective vector interval of the switching period to obtain two sampling results. A sampling averaging module for calculating the average value of the two sampling results of the same effective vector. A current reconstruction module for reconstructing the phase current. Based on the average value of the sampling results, according to the relationship between the DC current and the inverter-side phase current during the on or off process of the switching device under different effective vectors, that is, when the voltage rotation vector is in a certain sector, the two effective vectors synthesizing the voltage rotation vector respectively correspond to two-phase phase currents, and two of the three-phase phase currents on the inverter side are reconstructed. Then, the other phase is calculated through Kirchhoff's current law to obtain the reconstructed current information on the inverter side. A first-order low-pass filter module and a lead compensator module for improving the waveform quality of the reconstructed current. By adjusting the time constant of the first-order low-pass filter and with the assistance of the lead compensator module, the waveform quality of the three-phase reconstructed current information can be improved, and the waveform distortion introduced by maintaining the reconstruction dead zone can be eliminated.

[0036] Embodiment 3 In one embodiment of the present disclosure, a computer program product is provided, including a computer program, and when the computer program is executed by a processor, the improved three-phase AC current reconstruction method for a network-forming converter is implemented.

[0037] Embodiment 4 In one embodiment of the present disclosure, a non-transitory computer-readable storage medium is provided, and the non-transitory computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the improved three-phase current reconstruction method for a network-forming converter based on a single current sensor is implemented.

[0038] Embodiment 5 In one embodiment of the present disclosure, an electronic device is provided, including: 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 runs, 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-forming converter based on a single current sensor.

[0039] The present disclosure is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0040] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, so that a series of operation steps are executed on the computer or other programmable devices to generate computer-implemented processing, and thus the instructions executed on the computer or other programmable devices provide steps for realizing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0041] Although the specific implementation manners of the present disclosure have been described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present disclosure. Those skilled in the art should understand that, based on the technical solutions of the present disclosure, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present disclosure.

Claims

1. An improved three-phase current reconstruction method for a network-forming converter based on a single current sensor, characterized in that, Including: Sampling the current, and based on the seven-segment SVPWM modulation strategy, sampling each of the two symmetrically distributed sampling points once within the effective vector interval of the switching period to obtain two sampling results; Calculating the average value of the two sampling results of the same effective vector, and based on the average value of the sampling results, according to the relationship between the DC current and the inverter-side phase current during the on or off process of the switching device under different effective vectors, that is, when the voltage rotation vector is located in a certain sector, the two effective vectors synthesizing the voltage rotation vector respectively correspond to the phase currents of two phases, reconstructing two of the three-phase currents on the inverter side, and then calculating the other phase through Kirchhoff's current law to obtain the reconstructed current information on the inverter side; Combining the reconstructed dead-time holding, first-order low-pass filtering, and lead compensation algorithms to reduce the influence of the reconstructed dead-time and achieve high-precision reconstruction of the inverter-side current signal.

2. The improved three-phase current reconstruction method for a network-forming converter based on a single current sensor according to claim 1, wherein, During sampling, the sampling time needs to be greater than the minimum sampling window time, which 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 network-forming converter based on a single current sensor according to claim 1, characterized in that, Based on the seven-segment SVPWM modulation strategy, sampling once within the effective vector interval of the switching period respectively, and at the same time ensuring that the sampling points in the symmetric distribution interval of the same effective vector within the switching period are symmetric with respect to the carrier midpoint, the sampling points are selected as the midpoints of the effective vector intervals, and calculating the average value of the two sampling results of the same effective vector.

4. The improved three-phase current reconstruction method for a network-forming converter based on a single current sensor according to claim 1, characterized in that Adopting a current reconstruction strategy to reconstruct the current information on the inverter side according to the relationship between the DC current and the inverter-side phase current during the on or off process of the switching device under different effective vectors. There is a reconstructed dead-time problem in the current reconstruction strategy, and the reconstructed dead-time problem will be eliminated by using a dead-time holding module, a first-order low-pass filtering module, and a lead compensation module. When the voltage rotation vector runs within the time before and after the sector edge, the dead-time holding module keeps the current value of the reconstruction failure within the dead-time range equal to the normal reconstruction current value at the previous moment before entering the reconstructed dead-time range.

5. The improved three-phase current reconstruction method for a network-forming converter based on a single current sensor according to claim 1, characterized in that, The time constant of the first-order low-pass filtering 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 filtering is increased.

6. The improved three-phase current reconstruction method of the grid-forming converter based on a single current sensor according to claim 1, characterized in that Design and determine the time constant, correction coefficient, and amplitude coefficient of the lead compensation module according to the lag phase caused by the time constant of the first-order low-pass filtering 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 for a network-forming converter based on a single current sensor according to claim 6, characterized in that, The transfer function of the first-order low-pass filter can be expressed as: Among them, T LPF is the time constant of the first-order low-pass filter. This time constant can be adjusted according to the waveform quality of the reconstructed current on the inverter side. When the waveform quality of the reconstructed current on the inverter side 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, it implements the improved three-phase current reconstruction method for a grid-forming converter based on a single current sensor as described in any one of claims 1-7.

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

10. An electronic device, characterized in that, Including: 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 operates, the processor executes the computer program stored in the memory so that the electronic device executes and implements the improved three-phase current reconstruction method of the network-forming converter based on a single current sensor as described in any one of claims 1-7.

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