Method and system for improving overload capability of network construction converter cluster based on coordinated regulation

Abstract

The application provides a network construction converter cluster overload capacity improvement method and system based on coordinated regulation, belonging to the technical field of network construction converters, which comprises the following steps: in the pre-overload operation stage, taking the total grid-connected current harmonic current as a rigid constraint and the minimum single-converter current harmonic current as a target, the PWM optimal phase is solved; in the overload transient operation stage, the reference value of the current inner loop in the dq coordinate system is generated based on the voltage loop, and then the effective value of the reference current is calculated; the adjustment amount of the switching frequency is calculated based on the change of the effective value of the reference current; in the overload steady-state stage, the adjustment amount of the switching frequency of all the network construction converter clusters is clustered, the PWM phase of each cluster is optimized, the optimal phase of each cluster is obtained, the phase additional value of each cluster is calculated based on the optimal phase, the calculated phase additional value is added to the optimal phase in each cluster, and finally the phase value of each converter is obtained and sent to each converter.

Description

Technical Field

[0001] This invention belongs to the field of grid converter technology, and particularly relates to a method and system for improving the overload capacity of grid converter clusters based on coordinated control. Background Technology

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

[0003] A grid-connected converter cluster refers to a collaborative system composed of multiple grid-connected converters used to construct and maintain voltage and frequency stability in a power system, and is particularly suitable for power systems with a high proportion of renewable energy. The overload capacity of a grid-connected converter cluster refers to its ability to withstand loads or power surges exceeding its rated capacity for a short period of time; this capability is crucial for maintaining system transient stability.

[0004] Compared to the high overload capacity of traditional synchronous generators, grid-connected converters with power switching devices at their core have poor overload capacity. Their self-protection strategies under overload conditions lead to frequent grid disconnection problems, affecting the safe and stable operation of the system. The strength of the overload capacity of grid-connected converters has become a decisive factor in whether the power grid can operate stably.

[0005] In recent years, numerous standards and specifications have continuously raised the overload capacity requirements for grid-connected converters, such as requiring a 3x overload for more than 10 seconds. However, the actual implementation in products is simplistic, mainly relying on redundant hardware, which significantly increases equipment costs. Furthermore, the power grid demands ever-higher overload capacity from grid-connected converters; even with redundant designs meeting current standards, the overload capacity falls far short of expectations. Therefore, both academia and industry are dedicated to finding ways to fully unlock and enhance the overload capacity of grid-connected converters within hardware constraints.

[0006] Furthermore, the overload operating capability of grid-connected converters primarily depends on the overload operating capability of their internal power switching devices. The safe operating area (SOA) of the power switches is mainly composed of three boundaries: overcurrent, overvoltage, and power dissipation. When a short-circuit fault occurs inside the converter, the instantaneous rise in current will first trigger the overcurrent limit. For grid-connected overload processes, although the overload current is less than the overcurrent limit, its duration is long, causing device power dissipation to become the primary limiting condition for triggering grid disconnection. Device power dissipation is mainly affected by factors such as overload power, drive parameters, power device parameters, and pulse width modulation (PWM) frequency. Among these, the PWM frequency is directly proportional to the switching power dissipation of the device and typically accounts for more than half of the total power dissipation. Therefore, dynamically adjusting the PWM frequency is an effective method to reduce device power dissipation during overload processes. For converter clusters, the total current harmonics can be reduced by coordinating the PWM phase, which can further lower the lower limit of the PWM frequency and thus expand the adjustable range of the PWM frequency. However, existing methods do not fully utilize the system advantages of converter clusters, resulting in a limited PWM adjustable range and a small improvement in overload capability.

[0007] Furthermore, although existing technologies disclose related solutions for improving the overload capacity of grid-connected converters based on active adjustment of switching frequency, the problem that still exists is that for converter clusters, the total current harmonics can be reduced by coordinating the PWM phase, which can further reduce the lower limit of the PWM frequency and thus expand the adjustable range of the PWM frequency. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, this invention provides a method for improving the overload capacity of grid-connected converter clusters based on coordinated control. The method incorporates the PWM phase and frequency in the grid-connected converter cluster into a unified coordinated control system. Under non-overload operating conditions, the method calculates in advance the PWM frequency range that can meet the stability boundary of the grid-connected converter while ensuring harmonic elimination.

[0009] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0010] Firstly, a method for improving the overload capacity of grid-connected converter clusters based on coordinated control is disclosed, including:

[0011] During the pre-overload operation phase, the optimal PWM phase is solved with the total grid-connected current harmonic current as a rigid constraint and the minimum inverter single-unit current harmonic current as the objective.

[0012] During the overload transient operation phase, a reference value for the inner current loop in the dq coordinate system is generated based on the voltage loop, and then the effective value of the reference current is calculated; the adjustment amount of the switching frequency is calculated based on the change of the effective value of the reference current.

[0013] During the overload steady-state phase, the adjustment amounts of all switching frequencies of the obtained grid-connected converter cluster are clustered. The PWM phase of each cluster is optimized to obtain the optimal phase of each group. The phase supplement value of each group is calculated based on the optimal phase. The calculated phase supplement value is added to the optimal phase in each group to finally obtain the phase value of each converter and send it to each converter.

[0014] As a further technical solution, the total grid-connected current harmonic current is related to the PWM frequency of the converter, the PWM phase of the converter, and the harmonics flowing through the set frequency of the converter.

[0015] As a further technical solution, the single-machine current harmonic current and the converter m Harmonics generated by the converter m Other converters are injected into the converter. m Harmonic correlation.

[0016] As a further technical solution, when calculating the adjustment amount of the switching frequency based on the change of the effective value of the reference current, for devices whose heat loss is proportional to the current, the first calculation formula is used to calculate the adjustment amount of the switching frequency.

[0017] As a further technical solution, when calculating the adjustment amount of the switching frequency based on the change of the effective value of the reference current, for devices whose heat loss is proportional to the square of the current, the second calculation formula is used to calculate the adjustment amount of the switching frequency.

[0018] As a further technical solution, it also includes: for the pre-overload operation stage and the overload steady-state stage, the phase reference value is the output phase of the phase-locked loop; for the overload transient stage, the reference value is the voltage reference phase value generated by the grid construction strategy in the grid-connected converter.

[0019] Secondly, a system for enhancing the overload capacity of grid-connected converter clusters based on coordinated control is disclosed, including:

[0020] The PWM optimal phase solution module is configured to: during the pre-overload operation phase, with the total grid-connected current harmonic current as a rigid constraint and the minimum converter single-unit current harmonic current as the objective, solve for the PWM optimal phase.

[0021] The switching frequency adjustment calculation module is configured to: generate a reference value of the inner current loop in the dq coordinate system based on the voltage loop during the overload transient operation phase, and then calculate the effective value of the reference current; calculate the switching frequency adjustment based on the change of the effective value of the reference current.

[0022] The phase value sending module of each converter is configured to: during the overload steady-state stage, cluster the adjustment amounts of all switching frequencies of the obtained grid-connected converter cluster, optimize the PWM phase of each clustered group to obtain the optimal phase of each group, calculate the phase additional value of each group based on the optimal phase, add the calculated phase additional value to the optimal phase in each group, and finally obtain the phase value of each converter and send it to each converter.

[0023] The above one or more technical solutions have the following beneficial effects:

[0024] The technical solution of this invention incorporates the PWM phase and frequency in the grid-connected converter cluster into a unified and coordinated control system.

[0025] Using the PWM phase as a variable, a high-frequency harmonic model and a converter cluster stability margin evaluation model are established. The two models are then weighted to obtain an overall optimized model, and the PWM phase is calculated. During the stable phase of overload operation, the PWM phase is calculated with constraints including eliminating high-frequency harmonics from individual unit outputs and the stability domain.

[0026] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 This is a block diagram of a method according to an embodiment of the present invention. Detailed Implementation

[0029] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0031] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0032] Example 1

[0033] The overload capacity enhancement method is mainly divided into three stages: the pre-overload operation stage, the overload transient stage, and the overload steady-state stage. The pre-overload operation stage refers to the stage before the overload occurs. The overload transient stage refers to the stage after the overload condition occurs but before the control parameters have entered a new steady state. The overload steady-state stage refers to the stage where the control parameters enter a steady state, requiring operation at several times the overload condition for a certain period (e.g., 10 seconds). This embodiment's sub-technical solution optimizes each of these three stages; see appendix. Figure 1 As shown in the figure, the specific method for improving the overload capacity of grid-connected converter clusters based on coordinated control disclosed in this embodiment includes:

[0034] Step 1: During the pre-overload operation phase, the main focus is on solving the optimal phase of the converter cluster PWM. In the solution process, the total grid-connected current harmonics are used as rigid constraints, and the goal is to minimize the current harmonics of a single grid-connected converter.

[0035] Step 2: During the overload transient operation phase, the voltage loop generates a reference value for the inner current loop in the dq coordinate system based on the voltage loop through the PI regulator. I dref , I qref Then calculate the reference current. I ref Further based on the inner loop current reference value I ref The change in the switching frequency is used to calculate the adjustment amount.

[0036] Step 3: During the overload steady-state phase, I ref The frequency tends to stabilize, therefore the adjustment amount of the switching frequency f m,PWM It also tends to stabilize. Furthermore, considering the adjustment amount of the switching frequency between converters... f m,PWM Since there are differences, the adjustment amount of the switching frequency is first based on the K-means method. f m,PWM Perform clustering and ensure the adjustment amount of the switching frequency in each group. f m,PWM The number is no less than two.

[0037] Step 4: Based on the clustering in Step 3, for each group, in order to ensure the elimination of high-order harmonics at low switching frequencies, and also to avoid device overheating caused by high PWM frequencies, the adjustment amount of the switching frequency for each group is... f m,PWM In this case, each group contains multiple converters, and each converter has an adjustment range. f m,PWM Adjustment amount of all switching frequenciesf m,PWM The maximum value should be placed within it.

[0038] Step 5: Based on Step 4, further optimize the PWM phase for each group. f m,PWM For each set of phases to be optimized, the optimization objective is to minimize the output harmonics of a single converter. Each converter has its own output harmonics; the converter with the largest harmonic current is selected, and the optimal PWM phase is chosen with minimizing the harmonics of that converter as the target. f m,PWM .

[0039] Step Six: After calculating the optimal phase for each group (i.e., the optimal PWM phase), further calculate the phase add-on value for each group. The optimization objective in calculating the phase add-on value is to minimize the total current harmonics. The specific solution method uses a particle swarm optimization algorithm. Finally, the calculated phase add-on value is compared with the values ​​in each group. f m,PWM The values ​​are added together to obtain the phase value of each converter, which is then sent to each converter.

[0040] Step 7: In addition to obtaining the phase, a unified reference value needs to be defined to ensure the accuracy of phase execution. For the pre-overload operation stage and the overload steady-state stage, the reference value is the output phase of the phase-locked loop. For the overload transient stage, the reference value is the voltage reference phase value generated by the grid-connected strategy in the grid-connected converter.

[0041] The output phase of the phase-locked loop is based on the three-phase voltage, for example, using a phase-locked loop based on synchronous rotation.

[0042] In one implementation example, the formula for calculating the total grid-connected current harmonics in step one is as follows:

[0043] (1)

[0044] in, I sum,h This is the effective value of the total harmonic current. f m,PWM The PWM frequency of the converter. f m,PWM f is the PWM phase of the converter. PWM φ represents a one-dimensional array consisting of all PWM frequencies. PWM This represents a one-dimensional array consisting of all PWM phases.

[0045] N This indicates the total number of converters. m Indicates the converter's number.I m,hf Indicates flow through the converter m The frequency is f Harmonics, f The frequency is represented by the double Fourier method, which can be calculated using a method that is common knowledge.

[0046] The formula for calculating harmonic current of a single unit is as follows:

[0047] (2)

[0048] in, I m,h This represents the effective value of the harmonic current for a single machine. I m,hf,self Indicates that it is made by the converter m Harmonics generated by itself I m,hf,other Indicates the converter m Other converters are injected into the converter. m Harmonics.

[0049] For different frequencies, the generated harmonic current is added to the harmonic current injected by other external converters. The squares of the results for different frequencies are then summed, and the square root is taken. The calculation requires obtaining... I m,hf,self and I m,hf,other The specific calculation method is existing technology and will not be elaborated here.

[0050] The optimization problem to be solved is as follows:

[0051] (3)

[0052] in, l This represents the penalty factor, which can be set to a larger value to ensure that the total current harmonics do not exceed the limit. I sum,hlimit This indicates the upper limit of total current harmonics.

[0053] Formula (3) can be calculated using particle swarm optimization algorithms, etc.

[0054] In one implementation example, in step two, for devices where heat loss is proportional to current, the formula for calculating the adjustment amount of the switching frequency is:

[0055] (4)

[0056] in, f PWMrated The rated PWM frequency of the converter. I rated This is the rated current of the converter.a This is the switching frequency adjustment factor, the specific value of which can be calculated relative to the heat loss. I ref The rate of change is obtained and evaluated through experiments in practice.

[0057] The above calculation formula is simple, reducing the computational burden on the controller. It also allows for adjustment of the PWM frequency based on the current magnitude.

[0058] To be applicable to devices where heat loss is proportional to the square of the current, the formula for calculating the switching frequency adjustment is as follows:

[0059] (5)

[0060] in, b This is the switching frequency adjustment factor, the specific value of which can be calculated relative to the heat loss. I ref The rate of change of the square is obtained; the specific value can be obtained through experiments.

[0061] In the specific steps of the above embodiments, the advantage of step one is that it ensures harmonic elimination and the stability of the grid-connected converter cluster during the pre-overload operation phase. The advantage of step two is that it enables the assessment of the PWM frequency adjustment amount. The advantage of step three is that by clustering the converters, it can both ensure harmonic elimination and improve overload capacity. The advantage of step four is that it achieves the elimination of total current harmonics within the group.

[0062] Step five's advantage is the elimination of current harmonics in a single converter. Step six's advantage is the optimization of harmonic elimination between groups. Step seven's advantage is ensuring the accuracy of PWM phase execution. All steps offer the advantage of both improving overload capacity by reducing the PWM frequency during overload phases and ensuring power quality and stability throughout the process.

[0063] Under non-overload operating conditions, and assuming harmonic elimination, the PWM frequency range that satisfies the stability boundary of the grid-type converter is calculated in advance. A small-signal model of the grid-type converter is established, and 1.5 times the switching cycle is equated to a delay element. Stability is determined using the Bode plot criterion or the Nyquist criterion. If stable, the switching frequency is gradually reduced until the stability boundary is reached; this switching frequency is the minimum open-circuit frequency. The range between the minimum switching frequency and the rated switching frequency constitutes the PWM frequency range.

[0064] In the initial stage of overload operation, based on the degree of voltage drop, the current overload curve is predicted, and the temperature rise curve of the power switching device caused by the current overload process is calculated in advance. Based on this curve, the required PWM frequency curve is derived in reverse to counteract the sharp increase in temperature in the early stage of overload.

[0065] The method for obtaining the predicted overload current curve is as follows: Based on the pre-set reactive power droop control formula inside the grid-connected converter, the required reactive power is predicted based on the voltage drop value. The corresponding reactive current reference value is then predicted, and finally, the maximum value of the total current is predicted in conjunction with the active current. Based on the obtained maximum total current, the overload operation curve is predicted using the grid-connected converter control response model.

[0066] Based on the overload operation curve and the RC network model of the power switching device, the temperature rise curve of the power switching device is calculated.

[0067] The basic principle of adjustment is to adjust the PWM frequency in reverse according to the change process of the reference current. Specifically, the current difference is obtained by subtracting the current reference value from the rated current value. This difference is multiplied by a coefficient to obtain the degree of PWM frequency reduction. The PWM frequency value is obtained by subtracting this degree of reduction from the rated PWM frequency.

[0068] Example 2

[0069] The purpose of this embodiment is to provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the above-described method.

[0070] Example 3

[0071] The purpose of this embodiment is to provide a computer-readable storage medium.

[0072] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the above method.

[0073] Example 4

[0074] The purpose of this embodiment is to provide a system for enhancing the overload capacity of a grid-connected converter cluster based on coordinated control, including:

[0075] The PWM optimal phase solution module is configured to: during the pre-overload operation phase, with the total grid-connected current harmonic current as a rigid constraint and the minimum converter single-unit current harmonic current as the objective, solve for the PWM optimal phase.

[0076] The switching frequency adjustment calculation module is configured to: generate a reference value of the inner current loop in the dq coordinate system based on the voltage loop during the overload transient operation phase, and then calculate the effective value of the reference current; calculate the switching frequency adjustment based on the change of the effective value of the reference current.

[0077] The phase value sending module of each converter is configured to: during the overload steady-state stage, cluster the adjustment amounts of all switching frequencies of the obtained grid-connected converter cluster, optimize the PWM phase of each clustered group to obtain the optimal phase of each group, calculate the phase additional value of each group based on the optimal phase, add the calculated phase additional value to the optimal phase in each group, and finally obtain the phase value of each converter and send it to each converter.

[0078] Example 5

[0079] The purpose of this embodiment is to provide a computer program product containing instructions that, when run on a computer, cause the computer to perform the methods and functions involved in any of the above embodiments.

[0080] The steps and methods involved in the apparatus of the above embodiments correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0081] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0082] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for improving the overload capacity of grid-connected converter clusters based on coordinated regulation, characterized by: include: During the pre-overload operation phase, the optimal PWM phase is solved with the total grid-connected current harmonic current as a rigid constraint and the minimum inverter single-unit current harmonic current as the objective. The formula for calculating the total grid-connected current harmonics is as follows: in, I sum,h This is the effective value of the total harmonic current. f m,PWM The PWM frequency of the converter. φ m,PWM f is the PWM phase of the converter. PWM φ represents a one-dimensional array consisting of all PWM frequencies. PWM This represents a one-dimensional array consisting of all PWM phases. N This indicates the total number of converters. m Indicates the converter's serial number. I m,hf Indicates flow through the converter m The frequency is f Harmonics, f Indicates frequency; The formula for calculating the harmonic current of the single-unit current is as follows: in, I m,h This represents the effective value of the harmonic current for a single machine. I m,hf,self Indicates that it is made by the converter m Harmonics generated by itself I m,hf,other Indicates the converter m Other converters are injected into the converter. m Harmonics; The optimization problem to be solved is as follows: in, λ This represents the penalty factor, which is set to a large value to ensure that the total current harmonics do not exceed the limit. I sum,hlimit Indicates the upper limit of total current harmonics; During the overload transient operation phase, a reference value for the inner current loop in the dq coordinate system is generated based on the voltage loop, and then the effective value of the reference current is calculated; the adjustment amount of the switching frequency is calculated based on the change of the effective value of the reference current. The formula for calculating the adjustment amount of the switching frequency is as follows: For devices where heat loss is directly proportional to current: in, f PWMrated The rated PWM frequency of the converter. I rated This is the rated current of the converter. a This is the switching frequency adjustment factor, the specific value of which is calculated relative to the heat loss. I ref The rate of change is obtained and evaluated through experiments in practice; For devices where heat loss is proportional to the square of the current: in, b This is the switching frequency adjustment factor, the specific value of which is calculated relative to the heat loss. I ref The rate of change of the square is obtained; the specific value is obtained through experiments. During the overload steady-state phase, the adjustment values ​​of all switching frequencies in the obtained grid-connected converter cluster are clustered based on the K-means method, ensuring that the adjustment values ​​of the switching frequencies in each group are within the specified range. f m,PWM The number should be no less than two. For each clustered group, optimize the PWM phase, and adjust the switching frequency for each group. f m,PWM Each group contains multiple converters, and each converter has an adjustment range. f m,PWM Adjustment amount of all switching frequencies f m,PWM The maximum value should be placed among them. For each group of phases to be optimized, the optimization objective is to minimize the output harmonics of a single converter. Each converter has its own output harmonics. The converter with the largest harmonic current is selected, and the optimal phase for each group is obtained with the minimum harmonics of that converter as the objective. Based on the optimal phase, the phase additional value of each group is calculated with the minimum total current harmonics as the optimization objective. The specific solution method is to use the particle swarm optimization algorithm, add the calculated phase additional value to the optimal phase in each group, and finally obtain the phase value of each converter, and send it to each converter.

2. The method for improving the overload capacity of grid-connected converter clusters based on coordinated control as described in claim 1, characterized in that, it also... include: For the pre-overload operation stage and the overload steady-state stage, the phase reference value is the output phase of the phase-locked loop. For the overload transient stage, the reference value is the voltage reference phase value generated by the grid construction strategy in the grid-connected converter.

3. A system for enhancing the overload capacity of a grid-connected converter cluster based on coordinated control, characterized in that: include: The PWM optimal phase solution module is configured to: during the pre-overload operation phase, with the total grid-connected current harmonic current as a rigid constraint and the minimum converter single-unit current harmonic current as the objective, solve for the PWM optimal phase. The formula for calculating the total grid-connected current harmonics is as follows: in, I sum,h This is the effective value of the total harmonic current. f m,PWM The PWM frequency of the converter. φ m,PWM f is the PWM phase of the converter. PWM φ represents a one-dimensional array consisting of all PWM frequencies. PWM This represents a one-dimensional array consisting of all PWM phases. N This indicates the total number of converters. m Indicates the converter's serial number. I m,hf Indicates flow through the converter m The frequency is f Harmonics, f Indicates frequency; The formula for calculating the harmonic current of the single-unit current is as follows: in, I m,h This represents the effective value of the harmonic current for a single machine. I m,hf,self Indicates that it is made by the converter m Harmonics generated by itself I m,hf,other Indicates the converter m Other converters are injected into the converter. m Harmonics; The optimization problem to be solved is as follows: in, λ This represents the penalty factor, which is set to a large value to ensure that the total current harmonics do not exceed the limit. I sum,hlimit Indicates the upper limit of total current harmonics; The switching frequency adjustment calculation module is configured to: generate a reference value of the inner current loop in the dq coordinate system based on the voltage loop during the overload transient operation phase, and then calculate the effective value of the reference current; calculate the switching frequency adjustment based on the change of the effective value of the reference current. The formula for calculating the adjustment amount of the switching frequency is as follows: For devices where heat loss is directly proportional to current: in, f PWMrated The rated PWM frequency of the converter. I rated This is the rated current of the converter. a This is the switching frequency adjustment factor, the specific value of which is calculated relative to the heat loss. I ref The rate of change is obtained and evaluated through experiments in practice; For devices where heat loss is proportional to the square of the current: in, b This is the switching frequency adjustment factor, the specific value of which is calculated relative to the heat loss. I ref The rate of change of the square is obtained; the specific value is obtained through experiments. The phase value transmission module of each converter is configured to: during the overload steady-state phase, cluster the adjustment values ​​of all switching frequencies of the obtained grid-connected converter cluster based on the K-means method, and ensure that the adjustment values ​​of the switching frequencies in each group are clustered. f m,PWM The number should be no less than two. For each clustered group, optimize the PWM phase, and adjust the switching frequency for each group. f m,PWM Each group contains multiple converters, and each converter has an adjustment range. f m,PWM Adjustment amount of all switching frequencies f m,PWM The maximum value should be placed among them. For each group of phases to be optimized, the optimization objective is to minimize the output harmonics of a single converter. Each converter has its own output harmonics. The converter with the largest harmonic current is selected, and the optimal phase for each group is obtained with the minimum harmonics of that converter as the objective. Based on the optimal phase, the phase additional value of each group is calculated with the minimum total current harmonics as the optimization objective. The specific solution method is to use the particle swarm optimization algorithm, add the calculated phase additional value to the optimal phase in each group, and finally obtain the phase value of each converter, and send it to each converter.

4. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of claim 1 or 2.

5. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the method described in claim 1 or 2 above.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it performs the steps of the method described in claim 1 or 2 above.

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