Current-limiting method and apparatus based on active compensation, and electronic device and converter

Abstract

Provided in the present disclosure are a current-limiting method and apparatus based on active compensation, and an electronic device and a converter. The current-limiting method based on active compensation comprises: acquiring the present actual current value and the maximum allowable current value of a grid-connected converter; determining the current difference between the maximum allowable current value and the present actual current value; on the basis of the current difference, determining a compensation amount for an angular frequency, wherein the compensation amount for the angular frequency is negatively correlated with the current difference; on the basis of the compensation amount for the angular frequency, performing compensation on an angular frequency reference value of the grid-connected converter, so as to obtain a compensated angular frequency reference value; and on the basis of the compensated angular frequency reference value, performing grid-forming control on the grid-connected converter.

Description

Current limiting method and device based on active power compensation, electronic device and current transformer

[0001] Cross-reference to related applications

[0002] The present disclosure is based on and claims priority from Chinese Patent Application No. 202411362083.9 filed on September 27, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the network construction technical field, and particularly relates to a current limiting method and device based on active power compensation, an electronic device and a current transformer. BACKGROUND

[0004] The widespread application of distributed new energy systems in power electronic power stations has brought about the problem of reduced grid damping and inertia, leading to poor grid disturbance resistance. In order to solve this problem, a virtual synchronous generator (VSG) control strategy is proposed. By changing the control strategy of the current transformer, it can simulate the inertia and damping characteristics of the synchronous generator to suppress the fluctuations of frequency and output power. The current transformer using this control strategy is equivalent to a voltage source for network construction type current transformer.

[0005] Since the current transformer contains a large number of power electronic components inside, there will be a current limiting link in its control link to ensure the safe operation of the current transformer. The usual output current limiting link is set between the voltage and current double closed loop control. After triggering the current limiting, the current transformer using the VSG control strategy will become a current source control output, losing the voltage source characteristics, and is easy to cause instability under weak network, and its limiting transient process is complex and the power angle stability is poor. SUMMARY

[0006] The embodiments of the present disclosure provide a current limiting method and device based on active power compensation, an electronic device and a current transformer to solve the problem that the current limiting method makes the current transformer lose the voltage source characteristics, is easy to cause instability under weak network, and its limiting transient process is complex and the power angle stability is poor.

[0007] In a first aspect, the embodiments of the present disclosure provide a current limiting method based on active power compensation, comprising:

[0008] obtaining a current actual current value and a maximum allowed current value of a grid-connected current transformer;

[0009] determining a current difference value of the maximum allowed current value and the current actual current value;

[0010] According to the current difference, a compensation amount of the angular frequency is determined; the compensation amount of the angular frequency is negatively correlated with the current difference.

[0011] According to the compensation amount of the angular frequency, a reference value of the angular frequency of the grid-connected converter is compensated to obtain a compensated reference value of the angular frequency.

[0012] According to the compensated reference value of the angular frequency, a grid-forming control is performed on the grid-connected converter.

[0013] In a possible implementation, according to the current difference, the compensation amount of the angular frequency is determined, including:

[0014] According to the current difference, the compensation amount of the angular frequency is determined based on an inverse proportional function.

[0015] In a possible implementation, according to the current difference, the compensation amount of the angular frequency is determined, including:

[0016] An actual value of a D-axis current component of the grid-connected converter is obtained.

[0017] A ratio of the actual value of the D-axis current component to a current actual value is determined.

[0018] According to the ratio and the current difference, the compensation amount of the angular frequency is determined; the compensation amount of the angular frequency is positively correlated with the ratio.

[0019] In a possible implementation, before the compensation amount of the angular frequency is determined according to the current difference, the current-limiting method based on active compensation further includes:

[0020] The current difference and a preset current-limiting point threshold value are compared.

[0021] Correspondingly, according to the current difference, the compensation amount of the angular frequency is determined, including:

[0022] If the current difference is less than the preset current-limiting point threshold value, the compensation amount of the angular frequency is determined according to the current difference.

[0023] In a possible implementation, after the current difference and the preset current-limiting point threshold value are compared, the current-limiting method based on active compensation further includes:

[0024] If the current difference is greater than or equal to the preset current-limiting point threshold value, the compensation amount of the angular frequency is determined to be 0.

[0025] In a possible implementation, according to the compensation amount of the angular frequency, the reference value of the angular frequency of the grid-connected converter is compensated to obtain the compensated reference value of the angular frequency, including:

[0026] The reference value of the angular frequency of the grid-connected converter is subtracted by the compensation amount of the angular frequency to obtain the compensated reference value of the angular frequency.

[0027] In a possible implementation, the grid-connected converter is controlled according to the compensated angular frequency reference value, including:

[0028] The phase angle reference value is determined according to the compensated angular frequency reference value.

[0029] The voltage amplitude reference value output by the voltage regulation control loop is obtained.

[0030] The three-phase voltage reference value is determined according to the phase angle reference value and the voltage amplitude reference value.

[0031] The three-phase voltage reference value is input into the voltage-current double closed loop control loop to obtain the control quantity of the grid-connected converter.

[0032] The grid-connected converter is controlled according to the control quantity of the grid-connected converter.

[0033] In a second aspect, the embodiments of the present disclosure provide a current limiting device based on active compensation, including:

[0034] The acquisition module is configured to acquire the current actual current value and the maximum allowable current value of the grid-connected converter.

[0035] The current difference value determination module is configured to determine the current difference value between the maximum allowable current value and the current actual current value.

[0036] The compensation quantity determination module is configured to determine the compensation quantity of the angular frequency according to the current difference value, and the compensation quantity of the angular frequency is negatively correlated with the current difference value.

[0037] The compensation module is configured to compensate the angular frequency reference value of the grid-connected converter according to the compensation quantity of the angular frequency to obtain the compensated angular frequency reference value.

[0038] The current limiting control module is configured to control the grid-connected converter according to the compensated angular frequency reference value.

[0039] In a third aspect, the embodiments of the present disclosure provide an electronic device, including a memory and a processor, the memory is configured to store a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the current limiting method based on active compensation as described in the first aspect or any possible implementation of the first aspect.

[0040] In a fourth aspect, the embodiments of the present disclosure provide a grid-connected converter, including the electronic device as described in the third aspect.

[0041] In a fifth aspect, the present disclosure provides a computer-readable storage medium, which stores a computer program. The computer program is executed by a processor to implement the steps of the active power compensation based current limiting method according to the first aspect or any possible implementation manner of the first aspect. BRIEF DESCRIPTION OF DRAWINGS

[0042] Fig. 1 is a control block diagram of a typical VSG;

[0043] Fig. 2 is a flowchart of the active power compensation based current limiting method according to an embodiment of the present disclosure;

[0044] Fig. 3 is a control block diagram of an improved VSG according to an embodiment of the present disclosure;

[0045] Fig. 4 is a diagram of the correspondence between the current difference and the compensation amount ωc of the angular frequency according to an embodiment of the present disclosure;

[0046] Fig. 5 is a structural diagram of the active power compensation based current limiting device according to an embodiment of the present disclosure;

[0047] Fig. 6 is a diagram of an electronic device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0048] The present disclosure will be further clarified by the following examples, which should not be construed as limiting the present disclosure. The following examples will help those skilled in the art to further understand the role of the present disclosure, but do not limit the present disclosure in any form. It should be noted that for those skilled in the art, without departing from the concept of the present disclosure, a number of modifications and improvements can be made. These all belong to the protection scope of the present disclosure.

[0049] It should be understood that when used in the specification and appended claims of the present disclosure, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or sets thereof.

[0050] It should also be understood that the term "and / or" used in the specification and appended claims of the present disclosure refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0051] In the description of the present disclosure and the appended claims, the terms "first", "second", "third", etc. are only configured to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0052] Reference to "one embodiment" or "some embodiments" etc. in the present disclosure means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment" or "in some embodiments" etc. in various places in the specification are not necessarily all referring to the same embodiment, but can refer to one or more but not all embodiments, unless otherwise specifically stated. The terms "including," "containing," "having," and variations thereof, mean "including but not limited to," unless expressly specified otherwise.

[0053] In addition, "a plurality of" mentioned in the embodiments of the present disclosure should be interpreted as two or more.

[0054] As described previously, in the related art, as the penetration rate of distributed new energy continues to increase, more and more converters are integrated into the power grid, which greatly reduces the total damping and total inertia provided by the traditional generators in the power grid, so that the frequency changes faster and the anti-interference ability of the power grid is reduced when the power grid is disturbed. In order to solve this problem, the concept of virtual synchronous generator control technology is proposed, which can simulate the operation mechanism of synchronous generators, so that grid-connected converters can have grid support, inertia response, damping characteristics, and can provide grid inertia performance, and can provide frequency and voltage support for the system, and improve the stability of the power grid.

[0055] FIG. 1 is a control block diagram of a typical VSG. The control equation of the loop of the typical VSG is:

[0056] Wherein, P ref and P e are output active power instruction (i.e. active power reference value) and output actual active power (i.e. active power actual value) respectively; Q ref and Q e are output reactive power instruction (i.e. reactive power reference value) and output actual reactive power (i.e. reactive power actual value) respectively; ω n , ω0, U n and U o are output voltage angular frequency rated value (i.e. rated angular frequency) and output voltage angular frequency reference value (i.e. angular frequency reference value), grid output voltage amplitude and grid rated voltage amplitude respectively. D, J, k q , k u are VSG frequency damping coefficient, VSG virtual inertia coefficient, VSG voltage droop coefficient and VSG reactive inertia coefficient respectively; E is VSG reactive ring output excitation voltage (i.e. voltage amplitude reference value).

[0057] In FIG. 1, ΔP=Pref P e is the difference between the active power reference value and the actual value of the active power; ω x is the dynamic angular frequency output; θ ref is the phase angle reference value; E0 is the rated value of the voltage amplitude; 1 / s represents the integral operation; ua_ref, ub_ref and uc_ref are the A-phase voltage reference value, the B-phase voltage reference value and the C-phase voltage reference value respectively.

[0058] The amplitude limiting link of the general output current is added between the voltage and current double closed loop control. When the output reference current of the voltage loop exceeds a certain threshold, the amplitude limiting link will play a role to change the reference input current of the current loop, thereby limiting the current. Normally, the current limiting control does not play a role, when the converter is disturbed or in an unstable operating state, the current limiting control will start to prevent the converter from generating excessive current, thereby causing a more complex transient transition process. After triggering the current limiting, the VSG will become a current source control output, lose the voltage source characteristics, and easily cause instability in a weak grid, and the limiting transient transition process is complex and the power angle stability is poor.

[0059] To solve the above problems, the embodiment of the present disclosure provides a current limiting method based on active power compensation. The method improves the VSG control block diagram, increases the compensation amount of angular frequency based on the inverse proportional function idea, to realize phase compensation and achieve the purpose of current limiting. The method can achieve current limiting without changing the voltage source characteristics of the VSG, maintain the maximum power output capability of the converter, ensure the maximum support capability of the grid of the converter, and improve the stability of the grid.

[0060] The current limiting method based on active power compensation provided by the exemplary embodiment of the present disclosure will be described below with reference to FIGS. 2 to 4. The embodiment of the present disclosure can be configured to be applicable to any scenario.

[0061] It should be noted that the embodiment of the present disclosure can be configured as an electronic device, which can be a server, a computer or a controller, etc., that is, the current limiting method based on active power compensation provided by the exemplary embodiment of the present disclosure can be executed on the server, the computer or the controller, etc.

[0062] It should be noted that the current limiting method based on active power compensation provided by the exemplary embodiment of the present disclosure can be executed on the same device, or can be executed on different devices.

[0063] Referring to FIG. 2, an implementation flowchart of the current limiting method based on active power compensation provided by the embodiment of the present disclosure is shown. The current limiting method based on active power compensation described above can include:

[0064] In S201, a current actual current value and a maximum allowed current value of the grid-connected converter are acquired.

[0065] In the embodiment, the current actual current value of the grid-connected converter can be acquired by a current sampling device.

[0066] The maximum allowed current value of the grid-connected converter can be set according to actual requirements, for example, can be a maximum current value that the grid-connected converter can withstand, that is, a maximum current value that does not damage the devices of the grid-connected converter, and the like.

[0067] In S202, a current difference value of the maximum allowed current value and the current actual current value is determined.

[0068] The maximum allowed current value I max The current actual current value i real The above-mentioned current difference value ΔI is obtained.

[0069] In S203, a compensation amount of the angular frequency is determined according to the current difference value; the compensation amount of the angular frequency is negatively correlated with the current difference value.

[0070] When the current difference value increases, the compensation amount of the angular frequency decreases; when the current difference value decreases, the compensation amount of the angular frequency increases. That is, if the current actual current value decreases, so that the current difference value obtained by subtracting the current actual current value from the maximum allowed current value increases, the compensation amount of the angular frequency will decrease; if the current actual current value increases, so that the current difference value obtained by subtracting the current actual current value from the maximum allowed current value decreases, the compensation amount of the angular frequency will increase, that is, the closer the current actual current value is to the maximum allowed current value, the more obvious the compensation effect of the angular frequency is.

[0071] In S204, the angular frequency reference value of the grid-connected converter is compensated according to the compensation amount of the angular frequency, to obtain a compensated angular frequency reference value.

[0072] The angular frequency reference value of the grid-connected converter is ω0 in FIG. 1, and the value is the sum of a dynamic angular frequency output ω x and a rated angular frequency ω n .

[0073] In the embodiment, the angular frequency reference value of the grid-connected converter is compensated by the compensation amount of the angular frequency, to obtain a compensated angular frequency reference value. Referring to FIG. 3, the compensation amount of the angular frequency is ω c , and the compensated angular frequency reference value is ω 01 .

[0074] In S205, the grid-connected converter is controlled according to the compensated angular frequency reference value.

[0075] Based on the compensated angular frequency reference value, the grid-connected converter is controlled in a grid-forming mode or VSG mode, so as to achieve the current limiting purpose.

[0076] Specifically, referring to FIG. 1, when the angular frequency reference value of the grid-connected converter is not compensated according to the compensation amount of the angular frequency, if the frequency of the power grid suddenly changes, the frequency adjustment control loop can only adapt to the frequency change of the power grid through the change of the dynamic angular frequency output ω x . For example, assuming that the frequency of the power grid is normally 50 Hz, when it suddenly increases to 60 Hz due to some factors, the frequency adjustment control loop can only adapt to the frequency change of the power grid through the change of the dynamic angular frequency output ω x . The change of the dynamic angular frequency output ω x may increase the active power or the active current.

[0077] In the method provided in the present disclosure, referring to FIG. 3, when the angular frequency reference value of the grid-connected converter is compensated according to the compensation amount of the angular frequency, if the frequency of the power grid suddenly changes, based on the frequency adjustment control loop in FIG. 3, the frequency change of the power grid can be adapted through the change of the dynamic angular frequency output ω x and the compensation amount of the angular frequency ω c . In other words, the compensation amount of the angular frequency ω c shares part of the work of the dynamic angular frequency output ω x , so that the active current does not need to be too large due to the change of the dynamic angular frequency output ω x , thereby achieving the effect of current limiting.

[0078] The disclosure embodiment determines the compensation amount of the angular frequency according to the current difference value between the maximum allowed current value and the current actual current value of the grid-connected converter, and then compensates the angular frequency reference amount of the grid-connected converter according to the compensation amount of the angular frequency, wherein the compensation of the angular frequency reference amount is equivalent to the compensation of the phase angle reference amount, and the compensation amount of the angular frequency is negatively related to the current difference value, that is, the closer the current actual current value is to the maximum allowed current value, the smaller the current difference value is, and the larger the compensation amount of the angular frequency is, and the more obvious the compensation effect is, so that the pre-current limiting can be started before the current actual current value reaches the maximum allowed current value, the closer the maximum allowed current limiting value is, the more obvious the current limiting effect is, and the current actual current value can be limited until the current limiting purpose is achieved; in this way, the current limiting response speed is fast, the grid-connected converter still retains the voltage source characteristics, can maintain the maximum power capability output of the converter, ensures the maximum support capability of the grid-connected converter, and improves the stability of the power grid; in addition, in the related technology, when the grid frequency changes, only the dynamic angular frequency output amount in the frequency regulation control loop can be adjusted to adapt to the frequency change of the power grid, but only adjusting the dynamic angular frequency output amount can easily lead to an increase in current, and the disclosure adjusts the dynamic angular frequency output amount and the compensation amount of the angular frequency together to share the work of adapting to the frequency change of the power grid, so that the current corresponding to the dynamic angular frequency output amount is not too large, and the current limiting purpose is achieved.

[0079] The foregoing embodiment introduces the overall flow of the current limiting method based on active compensation, and how to determine the compensation amount of the angular frequency according to the current difference value is further introduced below.

[0080] In some embodiments, S203 can include:

[0081] The compensation amount of the angular frequency is determined according to the current difference value based on the inverse proportional function.

[0082] In this embodiment, the compensation amount of the angular frequency can be inversely proportional to the current difference value, and in the inverse proportional relationship, the compensation amount of the angular frequency becomes smaller as the current difference value increases.

[0083] In some embodiments, S203 can include:

[0084] The actual value of the D-axis current component of the grid-connected converter is obtained.

[0085] The ratio of the actual value of the D-axis current component to the current actual current value is determined.

[0086] The compensation amount of the angular frequency is determined according to the ratio and the current difference value, and the compensation amount of the angular frequency is positively related to the ratio.

[0087] In this embodiment, the compensation amount of the angular frequency is negatively related to the current difference value, and the compensation amount of the angular frequency is positively related to the ratio.

[0088] The D-axis current represents an active current. In order to better achieve the purpose of limiting the D-axis current (active current), in addition to considering the current difference between the maximum allowable current value and the current actual current value, the embodiment also considers the ratio of the actual value of the D-axis current component to the current actual current value, i.e., the proportion of the actual value of the D-axis current component in the current actual current value. The larger the ratio, the larger the compensation amount of the angular frequency, thereby achieving the purpose of better limiting the D-axis current component.

[0089] In the embodiment, the calculation formula of the compensation amount of the angular frequency can be wherein K is a preset adjustment coefficient, which can be a constant, and the specific value thereof can be set according to actual needs; I max is the maximum allowable current value; i real is the current actual current value; i d is the actual value of the D-axis current component; H(i d ) is the ratio of the actual value of the D-axis current component to the current actual current value.

[0090] Referring to FIG. 4, FIG. 4 shows the corresponding relationship between the current difference ΔI and the compensation amount ω c of the angular frequency. The abscissa is the current difference ΔI, and the ordinate is the compensation amount ω c of the angular frequency. As can be seen from FIG. 4, when the current difference ΔI tends to 0, i.e., in the process that the current actual current value approaches the maximum allowable current value, at this time, G(i real ) tends to infinity, and thus the compensation amount ω c of the angular frequency also tends to infinity, and the phase compensation also tends to infinity. That is, as the current actual current value approaches the maximum allowable current value, the phase compensation effect is more obvious.

[0091] The application of the inverse proportional function in the current limiting method of the embodiment can achieve the purpose of starting pre-limiting before the current limiting point, and the current limiting effect is more obvious as the current limiting point is approached, until the actual current is limited. In addition, the current limiting method provided by the embodiment has no upper limit on the current limiting capacity, and the current limiting effect is more obvious as the overcurrent is more serious. When the current difference ΔI is large, the compensation amount ω c of the angular frequency is small, and the influence on the overall control loop is small. Moreover, the method has a dynamic adjustment process, and the final adjustment result makes the actual current tend to be stable at the current limiting point.

[0092] In some embodiments, before S203, the active compensation-based current limiting method can further include:

[0093] comparing the size of the current difference and the preset current limiting point threshold value;

[0094] Accordingly, based on the current difference, the compensation amount for the angular frequency is determined, including:

[0095] If the current difference is less than the preset current limiting threshold, the compensation amount of the angular frequency is determined based on the current difference.

[0096] In some embodiments, after comparing the current difference with a preset current limiting threshold, the current limiting method based on active power compensation further includes:

[0097] If the current difference is greater than or equal to the preset current limiting threshold, then the compensation amount for the angular frequency is determined to be 0.

[0098] In this embodiment, to ensure that the current limiting process does not affect normal power in steady state, this embodiment adds a judgment condition, namely, judging whether the current difference is less than a preset current limiting threshold. If the current difference is less than the preset current limiting threshold, the angular frequency compensation amount is determined according to the aforementioned method; if the current difference is greater than or equal to the preset current limiting threshold, the angular frequency compensation amount is 0.

[0099] When the current difference is less than the preset current limiting threshold, it indicates that the current actual current value may be close to or greater than the maximum allowable current value. In this case, the current limiting method described in the previous embodiment is required. When the current difference is greater than or equal to the preset current limiting threshold, it indicates that the current actual current value is less than the maximum allowable current value. In this case, current limiting is not required, and therefore, the angular frequency compensation can be 0.

[0100] The preset current limiting threshold is a constant, and its value can be set according to actual needs, such as the actual operating conditions of different models. Its value must ensure that the angular frequency compensation is not affected when the converter is operating normally (i.e., when current limiting is not required).

[0101] In some embodiments, the angular frequency reference value of the grid-connected converter is compensated according to the compensation amount of the angular frequency to obtain the compensated angular frequency reference value, including:

[0102] The compensated angular frequency reference value is obtained by subtracting the angular frequency compensation amount from the angular frequency reference value of the grid-connected converter.

[0103] Referring to Figure 3, the compensated angular frequency reference value ω 01 The angular frequency reference value ω0 is subtracted from the angular frequency compensation amount ω. c The difference obtained. The angular frequency reference value ω0 is the dynamic angular frequency output ω. x and rated angular frequency ω n The sum of these, therefore, the compensated angular frequency reference value ω 01 The dynamic angular frequency output ω x and rated angular frequency ω n The sum, minus the angular frequency compensation ωc The difference obtained.

[0104] Based on the control loop in Figure 3, the compensation amount ω at the angular frequency... c Under the influence of the control equations, the governing equations become:

[0105] Simplifying the above equation, we can obtain:

[0106] In some embodiments, the above-mentioned grid configuration control of the grid-connected converter based on the compensated angular frequency reference value includes:

[0107] Determine the phase angle reference value based on the compensated angular frequency reference value;

[0108] Obtain the reference value of the voltage amplitude output by the voltage regulation control loop;

[0109] The three-phase voltage reference values ​​are determined based on the phase angle reference value and the voltage amplitude reference value;

[0110] The three-phase voltage reference value is input into the voltage and current dual closed-loop control circuit to obtain the control quantity of the grid-connected converter;

[0111] Based on the control input of the grid-connected converter, grid-type control is performed on the grid-connected converter.

[0112] Referring to Figure 3, the phase angle reference value θ can be obtained by integrating the compensated angular frequency reference value. ref The voltage amplitude reference value E can be obtained through the voltage regulation control loop; therefore, based on the phase angle reference value θ... ref From the voltage amplitude reference value E, we can obtain the three-phase voltage reference values, namely the A-phase voltage reference value ua_ref, the B-phase voltage reference value ub_ref, and the C-phase voltage reference value uc_ref.

[0113] The three-phase voltage reference value is used as the voltage setpoint of the voltage control loop to obtain the current reference value; the current reference value is used as the current setpoint of the current control loop to obtain the control quantity of the grid-connected converter; finally, according to the control quantity, corresponding control is performed to achieve the current limiting effect of the grid-connected converter.

[0114] Through relevant experiments, it has been verified that when the grid frequency changes from the normal 50Hz to 48Hz at a rate of 1Hz / s, the converter will experience an overcurrent fault if no current limiting is applied. When the frequency changes from 48Hz to 50Hz at a rate of 1Hz / s, the method provided in this embodiment calculates the angular frequency compensation ω as the actual current value of the converter approaches the maximum allowable current value. cThe compensation is introduced into the loop control, the maximum current and the maximum power output are limited, and the converter is prevented from overcurrent off-grid to maintain full load operation. During the continuous operation at a frequency of 48 Hz, the converter can still maintain the current limiting and the maximum power output limiting to support the power grid with the maximum capacity.

[0115] The current limiting method provided in the embodiments of the present disclosure can maintain the VSG voltage source characteristics of the converter after triggering the current limiting, does not change the control properties of the overall system, can maintain the maximum power capacity output of the converter after the current limiting, and guarantees the maximum support capacity of the converter for the power grid. The VSG control loop is changed slightly, is easy to modify, and does not affect the system when the current limiting is not triggered. The current limiting response speed is fast, and the overcurrent phenomenon caused by the primary frequency modulation and inertia response is effectively solved.

[0116] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present disclosure.

[0117] The following is a device embodiment of the present disclosure. For details not described in detail, reference can be made to the corresponding method embodiments described above.

[0118] FIG. 5 shows a structure schematic diagram of the current limiting device based on active compensation provided in the embodiments of the present disclosure. For ease of illustration, only the parts related to the embodiments of the present disclosure are shown, and the details are as follows:

[0119] As shown in FIG. 5, the current limiting device based on active compensation 30 can include an acquisition module 31, a current difference determination module 32, a compensation amount determination module 33, a compensation module 34, and a current limiting control module 35.

[0120] The acquisition module 31 is configured to acquire the current actual current value and the maximum allowable current value of the grid-connected converter;

[0121] The current difference determination module 32 is configured to determine the current difference value of the maximum allowable current value and the current actual current value;

[0122] The compensation amount determination module 33 is configured to determine the compensation amount of the angular frequency according to the current difference value; the compensation amount of the angular frequency is negatively correlated with the current difference value;

[0123] The compensation module 34 is configured to compensate the angular frequency reference value of the grid-connected converter according to the compensation amount of the angular frequency to obtain the compensated angular frequency reference value;

[0124] The current limiting control module 35 is configured to perform grid-forming control on the grid-connected converter according to the compensated angular frequency reference value.

[0125] In a possible implementation, the compensation amount determination module 33 is further configured to:

[0126] determine the compensation amount of the angular frequency according to the current difference value based on an inverse proportional function.

[0127] In a possible implementation, the compensation amount determination module 33 is further configured to:

[0128] obtain an actual value of the D-axis current component of the grid-connected converter;

[0129] determine a ratio of the actual value of the D-axis current component to the current actual value;

[0130] determine the compensation amount of the angular frequency according to the ratio and the current difference value; the compensation amount of the angular frequency is positively correlated with the ratio.

[0131] In a possible implementation, the compensation amount determination module 33 is further configured to:

[0132] before determining the compensation amount of the angular frequency according to the current difference value, compare the current difference value with a preset current limit point threshold value;

[0133] if the current difference value is less than the preset current limit point threshold value, determine the compensation amount of the angular frequency according to the current difference value.

[0134] In a possible implementation, the compensation amount determination module 33 is further configured to:

[0135] if the current difference value is greater than or equal to the preset current limit point threshold value, determine the compensation amount of the angular frequency as 0.

[0136] In a possible implementation, the compensation module 34 is further configured to:

[0137] subtract the compensation amount of the angular frequency from the angular frequency reference value of the grid-connected converter to obtain a compensated angular frequency reference value.

[0138] In a possible implementation, the current limit control module 35 is further configured to:

[0139] determine a phase angle reference value according to the compensated angular frequency reference value;

[0140] obtain a voltage amplitude reference value output by a voltage regulation control loop;

[0141] determine a three-phase voltage reference value according to the phase angle reference value and the voltage amplitude reference value;

[0142] input the three-phase voltage reference value into a voltage-current double closed loop control loop to obtain a control quantity of the grid-connected converter;

[0143] perform grid-forming control on the grid-connected converter according to the control quantity of the grid-connected converter.

[0144] FIG. 6 is a schematic diagram of an electronic device according to an embodiment of the present disclosure. As shown in FIG. 6, the electronic device 4 according to this embodiment includes a processor 40 and a memory 41. The memory 41 is configured to store a computer program 42, and the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to perform the steps in each of the above-described active compensation based current limiting method embodiments, such as S201 to S205 shown in FIG. 2. Alternatively, the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to implement the functions of each module / unit in each of the above-described device embodiments, such as the functions of each module shown in FIG. 5.

[0145] For example, the computer program 42 can be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to complete the present disclosure. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are configured to describe the execution process of the computer program 42 in the electronic device 4. For example, the computer program 42 can be divided into the modules shown in FIG. 5.

[0146] The electronic device 4 can include, but is not limited to, the processor 40 and the memory 41. Those skilled in the art can understand that FIG. 6 is only an example of the electronic device 4, and does not limit the electronic device 4, which can include more or fewer components than those shown, or combine certain components, or different components, for example, the electronic device can also include an input / output device, a network access device, a bus, etc.

[0147] The processor 40 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0148] The memory 41 can be an internal storage unit of the electronic device 4, for example, a hard disk or a memory of the electronic device 4. The memory 41 can also be an external storage device of the electronic device 4, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the electronic device 4. Further, the memory 41 can also include both the internal storage unit and the external storage device of the electronic device 4. The memory 41 is configured to store the computer program and other programs and data required by the electronic device. The memory 41 can also be configured to temporarily store data that has been output or is to be output.

[0149] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of each functional unit and module is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not configure the protection scope of the present disclosure. The specific working process of the unit and module in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0150] Corresponding to the above-mentioned electronic device, the embodiment of the present disclosure also provides a network-constructed converter comprising the above-mentioned electronic device.

[0151] In the above embodiments, the description of each embodiment has its own focus, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0152] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in connection with the embodiments disclosed herein can be realized in electronic hardware, or in a combination of computer software and electronic hardware. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present disclosure.

[0153] In the embodiments of the present disclosure, it should be understood that the disclosed apparatus / equipment and method can be implemented in other manners. For example, the described apparatus / equipment embodiments are merely schematic. For example, the division of the modules or units is merely logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0154] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0155] In addition, each functional unit in the various embodiments of the present disclosure can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0156] The integrated module / unit, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, all or part of the flow of the above-mentioned embodiment methods can be implemented by a computer program instructing related hardware to complete, and the computer program can be stored in a computer readable storage medium. When the processor executes the computer program, the steps of each of the above-mentioned active compensation based current limiting method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable file or some intermediate form. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0157] The above-described embodiments are only used to illustrate the technical solutions of the present disclosure, rather than limit them; although the foregoing embodiments of the present disclosure are described in detail, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and should be included in the protection scope of the present disclosure. Industrial applicability

[0158] In the technical solutions provided in the embodiments of the present disclosure, the compensation amount of the angular frequency is determined through the current difference between the maximum allowed current value and the current actual current value of the grid-connected converter, and then the angular frequency reference amount of the grid-connected converter is compensated according to the compensation amount of the angular frequency, wherein the compensation of the angular frequency reference amount is equivalent to the compensation of the phase angle reference amount, and the compensation amount of the angular frequency is negatively related to the current difference, that is, the closer the current actual current value is to the maximum allowed current value, the smaller the current difference is, and the larger the compensation amount of the angular frequency is, and the more obvious the compensation effect is, so that the pre-current limiting can be started before the current actual current value reaches the maximum allowed current value, the closer to the maximum allowed current value, the more obvious the current limiting effect is, until the current actual current value can be limited to achieve the current limiting purpose; in this way, the current limiting response speed is fast, the grid-connected converter still retains the voltage source characteristics, can maintain the maximum power capability output of the converter, ensures the maximum support capability of the grid-connected converter, and improves the stability of the power grid; in addition, in the related art, when the grid frequency changes, only the dynamic angular frequency output amount in the frequency regulation control loop can be adjusted to adapt to the frequency change of the power grid, but only adjusting through the dynamic angular frequency output amount can easily lead to an increase in current, and the present disclosure adjusts through the compensation amount of the angular frequency and the dynamic angular frequency output amount, and shares the work of adapting to the frequency change of the power grid together, so that the current corresponding to the dynamic angular frequency output amount is not too large, and the current limiting purpose is achieved.

Claims

1. A current limiting method based on active compensation, comprising: obtaining a current actual current value and a maximum allowed current value of a grid-connected converter; determining a current difference value of the maximum allowed current value and the current actual current value; determining a compensation amount of an angular frequency according to the current difference value; the compensation amount of the angular frequency is in a negative correlation with the current difference value; compensating an angular frequency reference value of the grid-connected converter according to the compensation amount of the angular frequency, to obtain a compensated angular frequency reference value; performing grid-forming control on the grid-connected converter according to the compensated angular frequency reference value.

2. The active compensation based current limiting method of claim 1, wherein, The determining of the compensation amount of the angular frequency according to the current difference value comprises: determining the compensation amount of the angular frequency according to the current difference value based on an inverse proportional function.

3. The active compensation based current limiting method of claim 1, wherein, The determining of the compensation amount of the angular frequency according to the current difference value comprises: obtaining an actual value of a D-axis current component of the grid-connected converter; determining a ratio of the actual value of the D-axis current component to the current actual current value; determining the compensation amount of the angular frequency according to the ratio and the current difference value; the compensation amount of the angular frequency is in a positive correlation with the ratio.

4. The active compensation based current limiting method of claim 1, wherein, Before the determining of the compensation amount of the angular frequency according to the current difference value, the current limiting method based on active compensation further comprises: comparing the current difference value and a preset current limiting point threshold value; The determining of the compensation amount of the angular frequency according to the current difference value comprises: if the current difference value is less than the preset current limiting point threshold value, determining the compensation amount of the angular frequency according to the current difference value.

5. The active compensation based current limiting method of claim 4, wherein, After the comparing of the current difference value and the preset current limiting point threshold value, the current limiting method based on active compensation further comprises: if the current difference value is greater than or equal to the preset current limiting point threshold value, determining the compensation amount of the angular frequency as 0.

6. The active power compensation based current limiting method according to any one of claims 1 to 5, wherein, The compensating of the angular frequency reference value of the grid-connected converter according to the compensation amount of the angular frequency, to obtain the compensated angular frequency reference value, comprises: subtracting the compensation amount of the angular frequency from the angular frequency reference value of the grid-connected converter, to obtain the compensated angular frequency reference value.

7. The active power compensation based current limiting method according to any one of claims 1 to 6, wherein, The performing of the grid-forming control on the grid-connected converter according to the compensated angular frequency reference value comprises: determining a phase angle reference value according to the compensated angular frequency reference value; obtaining a voltage amplitude reference value output by a voltage regulation control loop; determining a three-phase voltage reference value according to the phase angle reference value and the voltage amplitude reference value; inputting the three-phase voltage reference value into a voltage-current double closed loop control loop, to obtain a control quantity of the grid-connected converter; performing the grid-forming control on the grid-connected converter according to the control quantity of the grid-connected converter.

8. A current limiting device based on active compensation, comprising: an obtaining module configured to obtain a current actual current value and a maximum allowed current value of a grid-connected converter; a current difference value determining module configured to determine a current difference value of the maximum allowed current value and the current actual current value; a compensation amount determining module configured to determine a compensation amount of an angular frequency according to the current difference value; the compensation amount of the angular frequency is in a negative correlation with the current difference value; a compensation module configured to compensate an angular frequency reference value of the grid-connected converter according to a compensation amount of the angular frequency, to obtain a compensated angular frequency reference value; a current-limiting control module configured to perform grid-forming control on the grid-connected converter according to the compensated angular frequency reference value.

9. An electronic device comprising a memory configured to store a computer program and a processor configured to invoke and run the computer program stored in the memory to execute the active compensation-based current-limiting method according to any one of claims 1 to 7.

10. A grid-forming converter comprising the electronic device according to claim 9.

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