Grid-connected inverter current harmonic suppression method and system based on wideband virtual inductance

Abstract

The application discloses a grid-connected inverter current harmonic suppression method and system based on wide-frequency virtual inductance, relates to the technical field of current transformer control, and solves the problem that existing technologies do not have the ability of inter-harmonic suppression, resulting in the problem that the harmonic suppression effect of the grid-connected inverter is reduced or even invalid. The application constructs an additional control loop for the non-power frequency component of the inverter output current, introduces wide-frequency virtual inductance in the additional control loop to increase the equivalent output impedance of the grid-connected inverter, so that the wide-frequency harmonic current of the grid-connected inverter under the grid voltage distortion condition is suppressed. The application can suppress the harmonic current of the grid-connected inverter caused by the integer harmonic and unknown frequency inter-harmonic in the grid voltage without harmonic frequency detection or pre-known harmonic frequency, so that the adaptability of the grid-connected inverter harmonic suppression under the complex grid condition is improved.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and more specifically to a method and system for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors. Background Technology

[0002] Grid-connected inverters, as crucial AC / DC interface devices in power systems, are widely used in renewable energy generation and power transmission. Harmonic emitters in power systems, such as uncontrolled rectification and impulsive loads, result in background harmonics commonly present in the grid voltage. These background harmonics can induce harmonic currents in the grid-connected inverter output, degrading system power quality, reducing equipment operating efficiency, and even inducing harmonic oscillations that can cause equipment disconnection. Therefore, ensuring the sinusoidal output of the grid-connected inverter under grid voltage harmonic distortion conditions is of great significance for improving inverter operating efficiency and power system stability.

[0003] Traditional harmonic suppression methods for grid-connected inverters mainly target the integer harmonic currents generated by integer harmonics in the grid voltage. These harmonics have a fixed frequency in both stationary and synchronous rotating coordinate systems; therefore, traditional methods primarily employ multi-PI control, resonant control, or repetitive control based on phase sequence separation. W.Xu et al., in [Negative Sequence Voltage Compensating for Unbalanced Standalone Brushless Double-Fed Induction Generator[J], IEEE Transactions on Power], […]. In Electronics, 2020, 35(1):667-680., a harmonic rotating coordinate system was constructed using phase sequence separation, and the harmonic components were converted into DC components and controlled by a PI controller. In the literature [Direct power control of grid-connected inverters without phase-locked loop under harmonic voltage [J]. Proceedings of the CSEE, 2017, 37(11):3243-3253+3380.], a resonant controller was designed for low-order harmonics of grid voltage, which realized the suppression of low-frequency integer harmonic currents of grid-connected converters. In the literature [Optimal predictive control of three-phase inverters based on repetitive control and state feedback [J]. Journal of Electrical Engineering, 2022, 37(06):1473-1481.], a sixth-harmonic repetitive controller was designed, which can be equivalent to an infinite number of sixth-harmonic resonant controllers connected in parallel, thereby realizing the suppression of high-frequency integer harmonics.

[0004] However, traditional methods, whether based on phase sequence separation multi-PI control, resonant control, or repetitive control, can only handle integer harmonics with fixed frequencies. With the influx of various types of power electronic devices into the power grid, such as circulating converters and controllable speed-changing equipment, the grid voltage also contains interharmonic voltages with variable frequencies. Traditional methods lack the ability to suppress interharmonics, leading to a decrease or even failure of the harmonic suppression effect of grid-connected inverters. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method and system for suppressing harmonic current in grid-connected inverters based on wideband virtual inductors. This aims to solve the problem that the prior art lacks interharmonic suppression capabilities, leading to a decrease or even failure in the harmonic suppression effect of grid-connected inverters.

[0006] The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors includes the following steps:

[0007] S1: Collect the three-phase output current i of the grid-connected inverter gabc The three-phase AC voltage u of the grid at the grid connection point of the grid-connected inverter gabc And calculate u gabc frequency ω g and voltage phase θ g Then i gabc and u gabc Transformed into a synchronous rotating coordinate system, the grid voltage U gdq and inverter output current I gdq ;

[0008] S2: In the synchronous speed rotating coordinate system, the inverter power frequency current command is... With inverter output current I gdq The difference is calculated, and the result is processed by a current PI controller to obtain the inverter's power frequency voltage modulation command. Inverter output current I gdq Feed into a second-order low-pass Chebyshev filter G H (s) Obtain the power frequency component of the inverter output current I gdq0 and the inverter output current I gdq With the inverter output current power frequency component I gdq0 By subtracting the input current, we obtain the non-power frequency component I of the inverter output current. gdqh ;

[0009] S3: In the synchronous speed rotating coordinate system, the inverter's non-power frequency current command is... The non-power frequency component of the inverter output current I gdqh The difference is calculated and sent to the wideband virtual inductor controller G. L In (s), the inverter additional voltage modulation command is obtained.

[0010] S4: Based on the inverter power frequency voltage modulation command Inverter Additional Voltage Modulation Command and voltage decoupling term E dq The modulation voltage vector of the grid-connected inverter is calculated.

[0011] S5: Utilizing the grid voltage phase θ g The modulation voltage vector of the grid-connected inverter obtained in step 5 Performing an inverse Parker transformation yields the modulation voltage vector of the grid-connected inverter in a two-phase stationary coordinate system. The switching trigger signal of the grid-connected inverter is obtained by using space vector pulse width modulation.

[0012] Preferably, step S1 includes the following steps:

[0013] S11: Use a voltage sensor to collect the three-phase AC voltage u of the power grid at the grid connection point of the grid-connected inverter. gabc Then, the three-phase AC voltage u of the power grid is calculated based on the phase-locked loop. gabc frequency ω g and voltage phase θ g ;

[0014] S12: Use a current sensor to collect the three-phase output current i of the grid-connected inverter. gabc ;

[0015] S13: Based on the grid voltage phase θg, respectively, the three-phase AC voltage u of the grid is... gabc and the three-phase output current i of the converter gabc Performing the Park transformation, we obtain the grid voltage and inverter output current U in the synchronous rotating coordinate system. gdq and I gdq .

[0016] Preferably, the formula for the Parker transformation in step S13 is as follows:

[0017]

[0018]

[0019] Where u and i represent voltage and current components respectively, and the subscripts ga, gb, and gc represent the phase components of the three phases a, b, and c respectively. ga u gb u gc i ga i gb i gc These are the three-phase components of the grid voltage and the inverter output current, respectively.

[0020] Preferably, in step S2, the inverter power frequency voltage modulation command The calculation formula is as follows:

[0021]

[0022] Where, k p and k i denoted as the proportional coefficient and integral coefficient in the current PI controller, respectively, and s is the frequency domain differential operator.

[0023] Preferably, in step S2, the power frequency component I of the inverter output current... gdq0 The calculation formula is as follows:

[0024]

[0025] Among them, G H (s) is a second-order Chebyshev low-pass filter, and K is G. H The gain of (s), s1 and s2 are G H The poles of (s);

[0026] The formulas for calculating K, s1, and s2 are as follows:

[0027]

[0028] Where ω n Here, ε is the filter cutoff frequency, and ε is the filter passband ripple coefficient.

[0029] The non-power frequency component I of the inverter output current gdqh The calculation formula is as follows:

[0030] I gdqh =I gdq -I gdq0 .

[0031] Preferably, in step S3, the inverter is given an additional voltage modulation command. The calculation formula is as follows:

[0032]

[0033] Among them G L (s) represents the wideband virtual inductor controller, and the specific calculation formula is as follows:

[0034]

[0035] Where α is the inductance value of the virtual inductor, T s For the equivalent delay of grid-connected inverter control, H L (s) represents the virtual inductance, H c (s) Control delay compensation.

[0036] Preferably, in step S4, the modulation voltage vector The calculation formula is as follows:

[0037]

[0038] Among them, E dq For the voltage decoupling term, the specific calculation formula is as follows:

[0039] E dq =-jω g L f I gdq

[0040] Among them, L f This is the inverter filter inductor.

[0041] Preferably, in step S5, the modulation voltage vector The calculation formula is as follows:

[0042]

[0043] The grid-connected inverter current harmonic suppression system based on wideband virtual inductor includes: grid voltage phase-locked loop and grid voltage and current Parker transformation module, power frequency current control loop module, output current non-power frequency component calculation module, wideband virtual inductor controller module, grid-connected inverter modulation voltage command calculation module, and modulation voltage vector coordinate transformation and signal modulation module.

[0044] The grid voltage phase-locked loop and grid voltage-current Parker conversion module is used to implement grid voltage phase-locked loop, grid voltage and inverter current Parker conversion;

[0045] The power frequency current control loop module is used to implement the inverter's power frequency voltage modulation commands. The calculation process;

[0046] The output current non-power frequency component calculation module is used to calculate the non-power frequency component I of the inverter output current. gdqh The calculation process;

[0047] The wideband virtual inductor controller module is used to implement inverter additional voltage modulation commands. Acquisition;

[0048] The grid-connected inverter modulation voltage command calculation module is used to implement the modulation voltage vector of the grid-connected inverter in the synchronous speed coordinate system. Calculation;

[0049] The modulated voltage vector coordinate transformation and signal modulation module is used to implement the modulated voltage vector of the grid-connected inverter in a two-phase stationary coordinate system. Calculation and modulation.

[0050] The beneficial effects of this invention include:

[0051] (1) Compared with traditional grid-connected inverter output current harmonic suppression methods, the control method of this invention has the advantages of a wide applicable frequency range and convenient implementation. Traditional grid-connected inverter harmonic current suppression methods based on phase sequence separation multi-PI control, resonant control, and repetitive control can only cope with integer harmonics with fixed frequencies. They require prior knowledge of the harmonic component frequencies, and the phase sequence separation-based multi-PI control also involves vector transformations between multiple rotating coordinate systems, making calculations complex. These reasons lead to a decrease in the performance or even failure of traditional grid-connected inverter harmonic suppression methods when the grid voltage contains interharmonic components. This invention constructs an additional control loop for the non-power frequency components of the inverter output current. A wideband virtual inductor is introduced into the additional control loop to increase the equivalent output impedance of the grid-connected inverter, thereby suppressing the wideband harmonic current of the grid-connected inverter under grid voltage distortion conditions. It can suppress the harmonic current of the grid-connected inverter caused by integer harmonics and unknown frequency harmonics in the grid voltage without the need for harmonic frequency detection or prediction, thereby improving the adaptability of the grid-connected inverter to harmonic suppression under complex grid conditions.

[0052] (2) The control method proposed in this invention can be completed by adding current feedback control on the basis of synchronous speed coordinate system vector control of grid-connected inverter. It can be directly applied to grid-connected inverters that have been put into operation without changing the original control structure, and has strong engineering practicality.

[0053] (3) This invention optimizes the inverter current control to obtain an improved grid-connected inverter modulation voltage vector. This process is independent of the acquisition method of voltage and current signals, the controller form of the power frequency current such as PI control or PID control, and the specific modulation method of the grid-connected inverter such as SVPWM or SPWM. Therefore, it has the advantage of being well applicable to grid-connected inverters with different control types. Attached Figure Description

[0054] Figure 1 This is a block diagram of a grid-connected inverter current harmonic suppression system based on a wideband virtual inductor.

[0055] Figure 2 This refers to the topology of a grid-connected inverter system.

[0056] Figure 3 This is a block diagram illustrating the control principle of a grid-connected inverter that incorporates a harmonic suppression method based on a wideband virtual inductor, as described in Example 1.

[0057] Figure 4The graph shows the amplitude curves of the output harmonic impedance before and after the harmonic suppression method is applied to the grid-connected inverter involved in Example 1, which is based on a wideband virtual inductor.

[0058] Figure 5 The results show the comparison between the operating effect of the current harmonic suppression strategy involved in Example 1 and the traditional harmonic suppression strategy (resonance control). Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, 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 a part of the embodiments of this application, and not all of the embodiments. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0060] Example 1

[0061] The following is in conjunction with the appendix Figure 2-5 Specific embodiments of the present invention will be described in detail;

[0062] Taking a grid-connected inverter with a rated capacity of 1kW as an example, it includes a DC component, a grid-connected inverter, a filter, and an AC grid. The grid-connected inverter is a three-phase, six-arm, fully controlled converter, and the filter is an L-type filter. ga u gb u gc Let i be the three-phase voltage of the power grid. ga i gb i gc These are the three-phase currents of the grid-connected inverter; L a L b L c R is the equivalent inductance of a three-phase filter. a R b R c V is the equivalent resistance of a three-phase filter. dc This refers to the DC bus voltage; specifically, as shown below. Figure 1 As shown in the diagram. The DC bus is powered by a DC power supply to ensure voltage stability. The inverter control system controls the inverter output current by applying different voltage modulation commands. The inverter is a three-phase, six-arm IGBT fully controlled converter, connected to the grid via an L-type filter.

[0063] The method of suppressing current harmonics in grid-connected inverters based on wideband virtual inductors is applied to inverters. The control principle of the inverter is as follows: Figure 3 Where s is the frequency domain differential operator, G p (s) represents the equivalent controlled object of the inverter, and its value is 1 / (sL). f +R f ), L f and R f These are the equivalent inductance and equivalent resistance of the inverter filter, respectively, G d (s) represents the inverter's equivalent control delay.

[0064] This invention is applied to the suppression of harmonic currents in grid-connected inverters under grid voltage harmonic distortion, and specifically includes the following steps:

[0065] (1) Use a voltage sensor to collect the three-phase AC voltage u of the power grid at the grid connection point of the grid-connected inverter. gabc Calculate the grid voltage frequency ω based on the phase-locked loop. g and voltage phase θ g Then, the three-phase output current i of the grid-connected inverter is collected using a current sensor. gabc According to the grid voltage phase θ g By performing Parker transformation (dq transformation) on the three-phase AC voltage of the grid and the three-phase output current of the inverter respectively, we obtain the grid voltage and inverter output current U in the synchronous speed rotating coordinate system. gdq and I gdq .

[0066] Grid voltage frequency ω g and voltage phase θ g The three-phase AC voltage u of the power grid gabc The grid voltage and inverter output current in the synchronous rotating coordinate system, obtained through a phase-locked loop, are U. gdq and I gdq The following formula is used to obtain:

[0067]

[0068]

[0069] Where: u and i represent voltage and current components, and the subscripts ga, gb, and gc represent the components of each of the three phases a, b, and c, respectively. ga u gb u gc i ga i gb i gc The three-phase components are the grid voltage and the inverter output current.

[0070] (2) In the synchronous speed rotating coordinate system, the inverter power frequency current command is... With inverter output current I gdqThe difference is calculated, and the result is processed by a current PI controller to obtain the inverter's power frequency voltage modulation command. Inverter power frequency current command With inverter output current I gdq After subtraction, the inverter power frequency voltage modulation command in the synchronous speed dq coordinate system is calculated using the following formula.

[0071]

[0072] Where, k p and k i denoted as the proportional coefficient and integral coefficient in the current PI controller, respectively, and s is the frequency domain differential operator.

[0073] (3) In the synchronous rotating coordinate system, the inverter output current is fed into the second-order low-pass Chebyshev filter G. H (s) Obtain the power frequency component of the inverter output current I gdq0 and the inverter output current I gdq With the inverter output current power frequency component I gdq0 By subtracting the input current, we obtain the non-power frequency component I of the inverter output current. gdqh .

[0074] Inverter output current power frequency component I in synchronous speed coordinate system gdq0 The following formula is used to obtain...

[0075]

[0076] Among them, G H (s) is a second-order Chebyshev low-pass filter, and K is G. H The gain of (s), s1 and s2 are G H The poles of (s), K, s1, and s2, are determined by the following formula.

[0077]

[0078] Where ω n ε is the filter cutoff frequency, and ε is the filter passband ripple coefficient.

[0079] Furthermore, the non-power frequency component I of the inverter output current gdqh It is obtained from the following formula,

[0080] I gdqh =I gdq -I gdq0

[0081] (4) In the synchronous speed rotating coordinate system, the inverter non-power frequency current command is... The non-power frequency component of the inverter output current I gdqhThe difference is calculated and sent to the wideband virtual inductor controller G. L In (s), the inverter additional voltage modulation command is obtained.

[0082] Inverter Additional Voltage Modulation Command It can be obtained from the following formula,

[0083]

[0084] Among them, the wideband virtual inductor controller G L (s) by virtual inductance H L (s) and control delay compensation H c (s) are connected in series, and the specific formula is as follows:

[0085]

[0086] Where α is the inductance value of the virtual inductor, T s This is the equivalent delay for grid-connected inverter control.

[0087] (5) Calculate the modulation voltage vector of the grid-connected inverter based on the output of the current regulator, the additional voltage modulation command of the inverter, and the voltage decoupling term. The specific formula is as follows:

[0088]

[0089] (6) Utilizing the grid voltage phase θ g Modulation voltage vector of grid-connected inverter By performing an inverse Parker transformation, the modulation voltage vector of the grid-connected inverter in the two-phase stationary coordinate system (αβ coordinate system) is obtained. The switching trigger signal of the grid-connected inverter is obtained by using space vector pulse width modulation (SVPWM). The calculation process is as follows:

[0090]

[0091] Specific implementation effects are as follows: Figure 4 As shown, Figure 4The amplitude curves of the output harmonic impedance of the grid-connected inverter when equipped with the control strategy proposed in this invention are shown. It can be seen that the proposed strategy, namely the output current harmonic suppression strategy, can effectively improve the output impedance amplitude of the grid-connected inverter. Taking the integer harmonics at 350Hz and the interharmonics at 640Hz as examples, the proposed control strategy can increase the output impedance amplitude of the grid-connected inverter from 4dB and 10dB to 25dB and 29dB, respectively. This indicates that the response current of the grid-connected inverter to the 350Hz and 640Hz grid harmonic voltages can be significantly suppressed. Similarly, this beneficial effect of the proposed control strategy on the grid-connected inverter is effective within the range of 100Hz to 1000Hz. This shows that the control scheme of this invention not only effectively reduces the impact of the grid's integer harmonics on the output current of the grid-connected inverter, but also significantly suppresses the inverter output current harmonics caused by interharmonic voltages over a wide frequency range.

[0092] The operational performance of grid-connected inverters using the current harmonic suppression strategy proposed in this invention is compared with that using traditional harmonic suppression strategies (resonance control) as follows: Figure 5 As shown, the proposed strategy refers to the current harmonic suppression strategy proposed in this invention, and the traditional strategy refers to the traditional harmonic suppression strategy (resonance control). Figure 5 The harmonic components of the grid voltage at 250Hz, 528Hz, 640Hz, and 950Hz are 5.6%, 3.7%, 3.0%, and 1.7%, respectively, with an active power of 500kW and a reactive power of 0. When the traditional harmonic suppression strategy is enabled, there are significant harmonics in the output current of the grid-connected inverter, with a total harmonic distortion of 5.8%. After adopting the current harmonic suppression strategy proposed in this solution, the components of the grid-connected inverter output current at 250Hz, 528Hz, 640Hz, and 950Hz are suppressed to 1.3%, 0.5%, 0.4%, and 0.6%, respectively, and the total harmonic distortion of the current is 1.7%. This indicates that the frequency range of the grid-connected inverter output current harmonic suppression strategy proposed in this invention is wider than that of the traditional harmonic suppression strategy, and it can effectively achieve sinusoidal output of the grid-connected inverter under conditions where the grid voltage includes interharmonics.

[0093] Example 2

[0094] See attached document Figure 1 The grid-connected inverter current harmonic suppression system based on wideband virtual inductance should be understood to be related to the above-mentioned appendix. Figure 1 Corresponding to the method implementation examples, it is capable of executing the attached... Figure 1 The various steps involved in the method implementation and the specific functions of the system can be found in the description above. To avoid repetition, detailed descriptions are omitted here.

[0095] As attached Figure 1As shown, the grid-connected inverter current harmonic suppression system based on wideband virtual inductor includes: a grid voltage phase-locked loop and grid voltage-current Parker transformation module ①, a power frequency current control loop module ②, an output current non-power frequency component calculation module ③, a wideband virtual inductor controller module ④, a grid-connected inverter modulation voltage command calculation module ⑤, and a modulation voltage vector coordinate transformation and signal modulation module ⑥; wherein ① is used to implement grid voltage phase-locking, grid voltage and inverter current Parker transformation, and ② is used to implement inverter power frequency voltage modulation commands. The calculation process, ③ is used to implement the non-power frequency component I of the inverter output current. gdqh Calculation process, ④ is used to implement the inverter additional voltage modulation command. The acquisition of, ⑤ is used to implement the modulation voltage vector of the grid-connected inverter in the synchronous speed coordinate system. Calculation, ⑥ is used to implement the modulation voltage vector of the grid-connected inverter in a two-phase stationary coordinate system. Calculation and modulation.

[0096] The above description of the embodiments is provided to enable those skilled in the art to quickly understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be easily made to the above embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors, characterized in that, The steps include the following: S1: Collect the three-phase output current of the grid-connected inverter The three-phase AC voltage of the grid at the grid connection point of the grid-connected inverter and calculate frequency and voltage phase , and then and Transformed into a synchronous rotating coordinate system for grid voltage and inverter output current ; S2: In the synchronous speed rotating coordinate system, the inverter power frequency current command is... With inverter output current The difference is calculated, and the result is processed by a current PI controller to obtain the inverter's power frequency voltage modulation command. ; Inverter output current Feed into a second-order low-pass Chebyshev filter Obtain the power frequency component of the inverter output current and the inverter output current With the power frequency component of the inverter output current By subtraction, the non-power frequency component of the inverter output current can be obtained. ; S3: In the synchronous speed rotating coordinate system, the inverter's non-power frequency current command is... Non-power frequency component of inverter output current The difference is calculated and sent to the wideband virtual inductor controller. In the process, the inverter additional voltage modulation command is obtained. ; S4: Based on the inverter power frequency voltage modulation command Inverter Additional Voltage Modulation Command and voltage decoupling terms The modulation voltage vector of the grid-connected inverter is calculated. ; S5: Utilizing grid voltage phase The modulation voltage vector of the grid-connected inverter obtained in step 5 Performing an inverse Parker transformation yields the modulation voltage vector of the grid-connected inverter in a two-phase stationary coordinate system. And the switching trigger signal of the grid-connected inverter is obtained by using space vector pulse width modulation; The wideband virtual inductor controller mentioned in step S3 The specific calculation formula is as follows: ； Where α is the inductance value of the virtual inductor. For the equivalent delay of grid-connected inverter control, For virtual inductance, Control delay compensation, where s is the frequency domain differential operator.

2. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, Step S1 includes the following steps: S11: Use a voltage sensor to collect the three-phase AC voltage of the power grid at the grid connection point of the grid-connected inverter. Then, the three-phase AC voltage of the power grid is calculated based on the phase-locked loop. frequency and voltage phase ; S12: Acquire the three-phase output current of the grid-connected inverter using a current sensor. ; S13: Based on the grid voltage phase The three-phase AC voltage of the power grid were respectively tested. and the three-phase output current of the converter Performing the Park transformation, we obtain the grid voltage and inverter output current in the synchronous rotating coordinate system. and .

3. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 2, characterized in that, The formula for the Parker transformation in step S13 is as follows: ； ； Where u and i represent the voltage and current components, respectively, and the subscripts ga, gb, and gc represent the components of each of the three phases a, b, and c, respectively. , , , , , These are the three-phase components of the grid voltage and the inverter output current, respectively.

4. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, In step S2, the inverter power frequency voltage modulation command The calculation formula is as follows: ； in, and denoted as the proportional coefficient and integral coefficient in the current PI controller, respectively, and s is the frequency domain differential operator.

5. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, In step S2, the inverter output current power frequency component The calculation formula is as follows: ； in, For a second-order Chebyshev low-pass filter, K is Gain, and for The extreme point; The K, , The calculation formula is as follows: ； in Here, ε is the filter cutoff frequency, and ε is the filter passband ripple coefficient. Non-power frequency component of inverter output current The calculation formula is as follows: 。 6. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, In step S3, the inverter is given an additional voltage modulation command. The calculation formula is as follows: 。 7. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, In step S4, the modulation voltage vector The calculation formula is as follows: ； in, For the voltage decoupling term, the specific calculation formula is as follows: ； in, This is the inverter filter inductor.

8. The method for suppressing current harmonics in grid-connected inverters based on wideband virtual inductors according to claim 1, characterized in that, In step S5, the modulation voltage vector The calculation formula is as follows: 。 9. A grid-connected inverter current harmonic suppression system based on wideband virtual inductor, characterized in that, include: The module includes: grid voltage phase-locked loop and grid-connected voltage and current Parker conversion module, power frequency current control loop module, output current non-power frequency component calculation module, wideband virtual inductor controller module, grid-connected inverter modulation voltage command calculation module, and modulation voltage vector coordinate transformation and signal modulation module. The grid voltage phase-locked loop and grid voltage-current Parker conversion module is used to implement grid voltage phase-locked loop, grid voltage and inverter current Parker conversion; The power frequency current control loop module is used to implement the inverter's power frequency voltage modulation commands. The calculation process; The output current non-power frequency component calculation module is used to calculate the non-power frequency component of the inverter output current. The calculation process; The wideband virtual inductor controller module is used to implement inverter additional voltage modulation commands. Acquisition; The grid-connected inverter modulation voltage command calculation module is used to implement the modulation voltage vector of the grid-connected inverter in the synchronous speed coordinate system. Calculation; The modulated voltage vector coordinate transformation and signal modulation module is used to implement the modulated voltage vector of the grid-connected inverter in a two-phase stationary coordinate system. Calculation and modulation.

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