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

Abstract

The invention provides a current limiting method and device based on active compensation, electronic equipment and a converter, and relates to the technical field of network construction. The current limiting method based on active compensation comprises the following steps: acquiring a current actual current value and a maximum allowable current value of a grid-connected converter; determining a current difference value between the maximum allowable current value and the current actual current value; determining the compensation amount of the angular frequency according to the current difference value; the compensation amount of the angular frequency is in 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; and performing network construction type control on the grid-connected converter according to the compensated angular frequency reference value. The purpose of current limiting can be achieved, the current limiting response speed is high through current limiting, the grid-connected converter still keeps the characteristics of a voltage source, the maximum power capacity output of the converter can be maintained, the maximum power grid supporting capacity of the converter is guaranteed, and the stability of a power grid is improved.

Description

Technical Field

[0001] The present invention relates to the field of network construction technology, and in particular to a current limiting method, device, electronic equipment and converter based on active power compensation. Background Art

[0002] The widespread application of distributed new energy systems in power electronic power stations has brought about the problem of reduced grid damping and inertia, resulting in poor grid anti-interference. In order to solve this problem, a virtual synchronous generator (VSG) control strategy was proposed. By changing the control strategy of the converter, it can simulate the inertia and damping characteristics of the synchronous generator and suppress the fluctuation of frequency and output power. The converter using this control strategy is equivalent to a voltage source and is a grid-type converter.

[0003] Since the converter contains a large number of power electronic components, there will be a current limiting link in its control link to ensure the safe operation of the converter. The usual output current limiting link is set between the voltage and current double closed-loop control. In this way, after the current limiting is triggered, the converter using the VSG control strategy will become a current source control output, losing the voltage source characteristics, which is easy to cause instability under weak grid conditions, and its limiting transient transition process is complex and the power angle stability is poor. Summary of the invention

[0004] The embodiments of the present invention provide a current limiting method, device, electronic device and converter based on active power compensation to solve the problems that the existing current limiting method causes the converter to lose its voltage source characteristics, easily causes instability under weak grid conditions, and its limiting transient transition process is complex and the power angle stability is poor.

[0005] In a first aspect, an embodiment of the present invention provides a current limiting method based on active power compensation, comprising:

[0006] Obtain the current actual current value and the maximum allowable current value of the grid-connected converter;

[0007] Determine the current difference between the maximum allowable current value and the current actual current value;

[0008] According to the current difference, the compensation amount of the angular frequency is determined; the compensation amount of the angular frequency is negatively correlated with the current difference;

[0009] The angular frequency reference value of the grid-connected converter is compensated according to the angular frequency compensation amount to obtain a compensated angular frequency reference value;

[0010] According to the compensated angular frequency reference value, the grid-connected converter is controlled in a grid-type manner.

[0011] In a possible implementation, determining the compensation amount of the angular frequency according to the current difference includes:

[0012] Based on the inverse proportional function, the compensation amount of the angular frequency is determined according to the current difference.

[0013] In a possible implementation, determining the compensation amount of the angular frequency according to the current difference includes:

[0014] Obtain the actual value of the D-axis current component of the grid-connected converter;

[0015] Determine the ratio of the actual value of the D-axis current component to the current actual current value;

[0016] The compensation amount of the angular frequency is determined according to the ratio and the current difference; the compensation amount of the angular frequency is positively correlated with the ratio.

[0017] In a possible implementation, before determining the compensation amount of the angular frequency according to the current difference, the current limiting method based on active power compensation further includes:

[0018] Compare the current difference with the preset current limit threshold;

[0019] Accordingly, the compensation amount of the angular frequency is determined according to the current difference, including:

[0020] If the current difference is less than the preset current limit threshold, the compensation amount of the angular frequency is determined according to the current difference. In a possible implementation, after comparing the current difference with the preset current limit threshold, the current limiting method based on active power compensation further includes:

[0021] If the current difference is greater than or equal to the preset current limit point threshold, the compensation amount of the angular frequency is determined to be 0.

[0022] In a possible implementation, compensating an angular frequency reference value of a grid-connected converter according to a compensation amount of an angular frequency to obtain a compensated angular frequency reference value includes:

[0023] The angular frequency reference value of the grid-connected converter is subtracted from the angular frequency compensation amount to obtain a compensated angular frequency reference value.

[0024] In a possible implementation, the grid-connected converter is controlled according to the compensated angular frequency reference value, including:

[0025] Determine a phase angle reference value according to the compensated angular frequency reference value;

[0026] Obtaining a voltage amplitude reference value output by a voltage regulation control loop;

[0027] Determine three-phase voltage reference values ​​according to the phase angle reference value and the voltage amplitude reference value;

[0028] Input the three-phase voltage reference value into the voltage and current double closed-loop control loop to obtain the control quantity of the grid-connected converter;

[0029] According to the control quantity of the grid-connected converter, the grid-connected converter is controlled.

[0030] In a second aspect, an embodiment of the present invention provides a current limiting device based on active power compensation, comprising:

[0031] An acquisition module is used to obtain the current actual current value and the maximum allowable current value of the grid-connected converter;

[0032] A current difference determination module, used to determine the current difference between the maximum allowable current value and the current actual current value;

[0033] A compensation amount determination module is used to determine the compensation amount of the angular frequency according to the current difference; the compensation amount of the angular frequency is negatively correlated with the current difference;

[0034] A compensation module, used for compensating the 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;

[0035] The current limiting control module is used to perform grid-type control on the grid-connected converter according to the compensated angular frequency reference value.

[0036] In a third aspect, an embodiment of the present invention provides an electronic device, comprising a memory and a processor, the memory being used to store a computer program, the processor being used to call and run the computer program stored in the memory, and executing a current limiting method based on active power compensation as described in the first aspect or any possible implementation of the first aspect.

[0037] In a fourth aspect, an embodiment of the present invention provides a grid-connected converter, comprising the electronic device as described in the third aspect.

[0038] In a fifth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the current limiting method based on active power compensation as described in the first aspect or any possible implementation method of the first aspect.

[0039] The embodiment of the present invention provides a current limiting method, device, electronic device and converter based on active power compensation. The method determines the angular frequency compensation amount through the current difference between the maximum allowable current value of the grid-connected converter and the current actual current value, and then compensates the angular frequency reference amount of the grid-connected converter according to the angular frequency compensation amount, wherein the compensation for the angular frequency reference amount is equivalent to the compensation for the phase angle reference amount, and the angular frequency compensation amount is negatively correlated with the current difference, that is, the closer the current actual current value is to the maximum allowable current value, the smaller the current difference is, and the larger the angular frequency compensation amount is, the more obvious the compensation effect is, so that the current limiting can be started before the current actual current value reaches the maximum allowable current value, and the closer to the maximum allowable current limiting value is, the more obvious the current limiting effect is, until The current actual current value can be limited to achieve the purpose of current limiting; by limiting the current in this way, the current limiting response speed is fast, the grid-connected converter still retains the voltage source characteristics, and can maintain the maximum power capacity output of the converter, ensuring the maximum supporting grid capacity of the converter, and improving the stability of the grid; in addition, in the related technology, when the grid frequency changes, it can only be adjusted through the dynamic angular frequency output in the frequency adjustment control loop to adapt to the frequency change of the grid, but only adjusting through the dynamic angular frequency output can easily lead to an increase in current, and the present application adjusts the angular frequency compensation amount and the dynamic angular frequency output together to share the work of adapting to the frequency change of the grid, so that the current corresponding to the dynamic angular frequency output will not be too large, thereby achieving the purpose of current limiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0041] Figure 1 This is the control block diagram of a typical VSG;

[0042] Figure 2 is a flow chart of a current limiting method based on active power compensation provided by an embodiment of the present invention;

[0043] Figure 3 is a block diagram of an improved VSG control provided by an embodiment of the present invention;

[0044] Figure 4 is the compensation value ω of the current difference ΔI and the angular frequency provided by the embodiment of the present invention c Schematic diagram of the corresponding relationship;

[0045] Figure 5 is a structural schematic diagram of a current limiting device based on active power compensation provided by an embodiment of the present invention;

[0046] Figure 6 is a schematic diagram of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present application is described more clearly below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the effects of the present application, but are not intended to limit the present application in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present application. These all fall within the scope of protection of the present application.

[0048] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0049] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0050] In the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0051] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0052] In addition, the “plurality” mentioned in the embodiments of the present application should be interpreted as two or more.

[0053] As mentioned above, in related technologies, with the continuous increase in the penetration rate of distributed renewable energy, more and more converters are connected to the grid, resulting in a significant reduction in the total damping and total inertia provided by traditional generators in the grid, which makes the frequency change faster and the anti-interference ability decrease when the grid faces disturbances. In order to solve this problem, the concept of virtual synchronous generator control technology was proposed. This control technology can imitate the operating mechanism of synchronous generators, so that grid-connected converters can have grid support, inertia response, damping characteristics, and can provide grid inertia performance, provide frequency and voltage support for the system, and improve grid stability.

[0054] Figure 1 The control block diagram of a typical VSG is shown in Figure 2. The control equation of the loop of a typical VSG is:

[0055]

[0056] Among them, P ref and P e They are the output active power command (i.e., active power reference value) and the output actual active power (i.e., active power actual value); Q ref and Q e They are the output reactive power command (i.e. reactive power reference value) and the output actual reactive power (i.e. reactive power actual value); ω n ,ω0,U n and U o They are the output voltage angular frequency rated value (i.e. rated angular frequency) and the output voltage angular frequency reference value (i.e. angular frequency reference value), the grid output voltage amplitude and the grid rated voltage amplitude. q , k u They are VSG frequency damping coefficient, VSG virtual inertia coefficient, VSG voltage droop coefficient and VSG reactive inertia coefficient; E is the VSG reactive loop output excitation voltage (i.e., voltage amplitude reference value).

[0057] exist Figure 1 , ΔP=P ref -P e , is the difference between the active power reference value and the actual active power value; 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, B phase voltage reference value and C phase voltage reference value respectively.

[0058] The usual output current limiting link 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 limiting link will come into play, changing the reference input current of the current loop, thereby limiting the current. Under normal circumstances, the current limiting control will not work. When the converter is subject to a large disturbance or is 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. In this way, after the current limiting is triggered, the VSG will become a current source control output, losing the voltage source characteristics, which is easy to cause instability under weak grid conditions, and its limiting transient transition process is complex and the power angle stability is poor.

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

[0060] Reference below Figures 2 to 4 The current limiting method based on active power compensation provided according to the exemplary embodiment of the present application is described. The embodiments of the present application can be applied to any applicable scenario.

[0061] It should be noted that the embodiments of the present application can be applied to electronic devices, and the electronic devices may be servers, computers or controllers, etc., that is, the current limiting method based on active power compensation provided by the exemplary embodiments of the present application can be executed on devices such as servers, computers or controllers.

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

[0063] See also Figure 2 , which shows a flow chart of implementing a current limiting method based on active power compensation provided by an embodiment of the present invention. The current limiting method based on active power compensation may include:

[0064] In S201, the current actual current value and the maximum allowable current value of the grid-connected converter are obtained.

[0065] In this embodiment, the current actual current value of the grid-connected converter can be obtained through the current sampling device.

[0066] The maximum allowable current value of the grid-connected converter can be set according to actual needs, for example, it can be the maximum current value that the grid-connected converter can withstand, that is, the maximum current value that will not damage various components of the grid-connected converter, and so on.

[0067] In S202 , a current difference between a maximum allowable current value and a current actual current value is determined.

[0068] Among them, the maximum allowable current value I max Subtract the actual current value i real The above-mentioned current difference ΔI is obtained.

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

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

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

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

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

[0074] In S205, 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 subjected to grid-type control or VSG control to achieve the purpose of current limiting.

[0076] Specifically, see Figure 1When the angular frequency reference value of the grid-connected converter is not compensated according to the angular frequency compensation amount, if the frequency of the grid changes suddenly, the frequency regulation control loop adapts to the frequency change of the grid. Figure 1 In the frequency regulation control loop, only the dynamic angular frequency output ω x For example, if the grid frequency is normally 50Hz, and it suddenly increases to 60Hz due to some factors, the dynamic angular frequency output ω can be used to adjust the grid frequency. x The change of the dynamic angular frequency output ω x The change in may cause the active power or active current to increase.

[0077] In the method provided in this application, see Figure 3 When the angular frequency reference value of the grid-connected converter is compensated according to the angular frequency compensation amount, if the frequency of the power grid suddenly changes, based on Figure 3 The frequency regulation control loop in the circuit can be controlled by the dynamic angular frequency output ω x and the compensation amount of angular frequency ω c The changes of the two adapt to the frequency changes of the power grid, which is equivalent to the compensation amount of angular frequency ω c Shares part of the dynamic angular frequency output ω x The work of the active current does not need to be due to the dynamic angular frequency output ω x The change is too large, thus achieving the effect of current limiting.

[0078] The embodiment of the present application determines the angular frequency compensation amount through the current difference between the maximum allowable current value of the grid-connected converter and the current actual current value, and then compensates the angular frequency reference amount of the grid-connected converter according to the angular frequency compensation amount, wherein the compensation for the angular frequency reference amount is equivalent to the compensation for the phase angle reference amount, and the angular frequency compensation amount is negatively correlated with the current difference, that is, the closer the current actual current value is to the maximum allowable current value, the smaller the current difference is, and the larger the angular frequency compensation amount is, the more obvious the compensation effect is, so that the current can be pre-limited before the current actual current value reaches the maximum allowable current value, and the closer to the maximum allowable current limit value, the more obvious the current limiting effect is, until the current actual current value can be limited to reach Purpose of current limiting: By limiting the current in this way, the current limiting response speed is fast, the grid-connected converter still retains the voltage source characteristics, can maintain the converter's maximum power capacity output, ensure the converter's maximum grid support capacity, and improve grid stability; in addition, in the related art, when the grid frequency changes, it can only be adjusted through the dynamic angular frequency output in the frequency regulation control loop to adapt to the frequency change of the grid. However, only adjusting through the dynamic angular frequency output can easily lead to an increase in current. The present application jointly adjusts the angular frequency compensation amount and the dynamic angular frequency output to share the work of adapting to the frequency change of the grid, so that the current corresponding to the dynamic angular frequency output will not be too large, thereby achieving the purpose of current limiting.

[0079] The above-mentioned embodiment introduces the overall process of the current limiting method based on active power compensation. The following further introduces how to determine the compensation amount of the angular frequency according to the current difference.

[0080] In some embodiments, the above S203 may include:

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

[0082] In this embodiment, the compensation amount of the angular frequency may be in an inversely proportional relationship to the current difference. In the inversely proportional relationship, as the current difference increases, the compensation amount of the angular frequency decreases.

[0083] In some embodiments, the above S203 may include:

[0084] Obtain the actual value of the D-axis current component of the grid-connected converter;

[0085] Determine the ratio of the actual value of the D-axis current component to the current actual current value;

[0086] The compensation amount of the angular frequency is determined according to the ratio and the current difference; the compensation amount of the angular frequency is positively correlated with the ratio.

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

[0088] The D-axis current represents the 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, this embodiment also considers the ratio of the actual value of the D-axis current component to the current actual current value, that is, the proportion of the actual value of the D-axis current component to the current actual current value. The larger the ratio, the greater the compensation amount of the angular frequency, thereby achieving the purpose of better limiting the D-axis current component.

[0089] In this 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 its specific value can be set according to actual needs; 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] See also Figure 4 , Figure 4 The above current difference ΔI and the compensation amount ω of the angular frequency are shown c The horizontal axis is the current difference ΔI, and the vertical axis is the compensation amount ω of the angular frequency. c .Depend on Figure 4 It can be seen that when the current difference ΔI approaches 0, that is, when the current actual current value is close to the maximum allowable current value, G(i real ) tends to infinity, so the compensation amount of angular frequency ω c The phase compensation also tends to infinity. That is to say, as the actual current value approaches the maximum allowable current value, the phase compensation effect becomes more obvious.

[0091] This embodiment uses the idea of ​​inverse proportional function to limit the current, which can achieve the purpose of starting pre-limiting before the current limit point. The closer to the current limit point, the more obvious the current limiting effect is, until the actual current is limited. In addition, the current limiting capacity of the method provided in this embodiment has no upper limit. As the overcurrent becomes more serious, the current limiting effect becomes more obvious. When the current difference ΔI is large, the compensation amount ω of the angular frequency c The smaller the value, the smaller the impact on the overall control loop; and it has a dynamic adjustment process, and the final adjustment result makes the actual current tend to the stable current limit point.

[0092] In some embodiments, before the above S203, the above current limiting method based on active power compensation may further include:

[0093] Compare the current difference with the preset current limit threshold;

[0094] Accordingly, the compensation amount of the angular frequency is determined according to the current difference, including:

[0095] If the current difference is less than the preset current limit point threshold, the compensation amount of the angular frequency is determined according to the current difference.

[0096] In some embodiments, after comparing the current difference with the preset current limiting point 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 limit point threshold, the compensation amount of the angular frequency is determined to be 0.

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

[0099] When the current difference is less than the preset current limit threshold, it means that the current actual current value may be close to or greater than the maximum allowable current value, and the method in the above embodiment needs to be used to achieve the purpose of current limiting. When the current difference is greater than or equal to the preset current limit threshold, it means that the current actual current value is less than the maximum allowable current value, and current limiting is not required. Therefore, the compensation amount of the angular frequency can be 0.

[0100] The preset current limit threshold is a constant, and its value can be set according to actual needs, for example, it can be set according to the actual operating conditions of different models. Its value must meet the normal operation of the converter (that is, when no current limiting is required) and the compensation amount of the angular frequency has no effect.

[0101] In some embodiments, compensating 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 includes:

[0102] The angular frequency reference value of the grid-connected converter is subtracted from the angular frequency compensation amount to obtain a compensated angular frequency reference value.

[0103] See also Figure 3 , the angular frequency reference value after compensation ω 01 The angular frequency reference value ω0 minus the angular frequency compensation value ω c The difference is obtained. The angular frequency reference value ω0 is the dynamic angular frequency output ω x and rated angular frequency ω n The sum of the angular frequency after compensation is ω 01 is the dynamic angular frequency output ω x and rated angular frequency ωn The sum of the angular frequency and the compensation value ω c The difference obtained.

[0104] based on Figure 3 The control loop, the compensation amount at the angular frequency ω c Under the action of , the control equation becomes:

[0105]

[0106] By simplifying the above formula, we can get:

[0107]

[0108] In some embodiments, the grid-connected converter is controlled according to the compensated angular frequency reference value, including:

[0109] Determine a phase angle reference value according to the compensated angular frequency reference value;

[0110] Obtaining a voltage amplitude reference value output by a voltage regulation control loop;

[0111] Determine three-phase voltage reference values ​​according to the phase angle reference value and the voltage amplitude reference value;

[0112] Input the three-phase voltage reference value into the voltage and current double closed-loop control loop to obtain the control quantity of the grid-connected converter;

[0113] According to the control quantity of the grid-connected converter, the grid-connected converter is controlled.

[0114] See also Figure 3 , integrate the compensated angular frequency reference value to obtain the phase angle reference value θ ref The voltage amplitude reference value E can be obtained through the voltage regulation control loop; thus, according to the phase angle reference value θ ref And the voltage amplitude reference value E, the three-phase voltage reference values ​​can be obtained, which are 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.

[0115] The three-phase voltage reference value is used as the voltage given value of the voltage control loop to obtain the current reference value; the current reference value is used as the current given value of the current control loop to obtain the control quantity of the grid-connected converter; finally, corresponding control is performed according to the control quantity to achieve the current limiting effect on the grid-connected converter.

[0116] Through relevant experiments, it is verified that when the grid frequency changes from the normal 50Hz to 48Hz at a rate of 1Hz / s, if the current is not limited, the converter will have an overcurrent fault. When the frequency is changed from 48Hz to 50Hz at a rate of 1Hz / s, the method provided in the embodiment of the present application is used to calculate the compensation amount ω of the angular frequency in the process of the current actual current value of the converter approaching the maximum allowable current value. c The compensation enters the loop control, limiting the maximum current and maximum power output to ensure that the converter does not flow out of the grid and maintains full load operation. During the continuous operation at a frequency of 48Hz, the converter can still maintain current limiting, limit the maximum power output, and support the grid with maximum capacity.

[0117] The current limiting method provided in the embodiment of the present application can ensure that after the current limiting is triggered, the converter can still maintain the VSG voltage source characteristics and does not change the control properties of the overall system; after the current limiting is triggered, the maximum power capacity output of the converter can be maintained to ensure the maximum grid support capacity of the converter; the change to the VSG control loop is small and easy to modify, and when the current limiting is not triggered, it has no impact on the system; the current limiting response speed is fast, and it is effective for overcurrent phenomena caused by primary frequency modulation and inertia response.

[0118] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0119] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0120] Figure 5 The structure diagram of the current limiting device based on active power compensation provided by an embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0121] like Figure 5 As shown, the current limiting device 30 based on active power compensation may 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 .

[0122] An acquisition module 31 is used to acquire a current actual current value and a maximum allowable current value of the grid-connected converter;

[0123] A current difference determination module 32, used to determine a current difference between a maximum allowable current value and a current actual current value;

[0124] The compensation amount determination module 33 is used to determine the compensation amount of the angular frequency according to the current difference; the compensation amount of the angular frequency is negatively correlated with the current difference;

[0125] The compensation module 34 is used 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;

[0126] The current limiting control module 35 is used to perform grid-type control on the grid-connected converter according to the compensated angular frequency reference value.

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

[0128] Based on the inverse proportional function, the compensation amount of the angular frequency is determined according to the current difference.

[0129] In a possible implementation, the compensation amount determination module 33 is specifically used to:

[0130] Obtain the actual value of the D-axis current component of the grid-connected converter;

[0131] Determine the ratio of the actual value of the D-axis current component to the current actual current value;

[0132] The compensation amount of the angular frequency is determined according to the ratio and the current difference; the compensation amount of the angular frequency is positively correlated with the ratio.

[0133] In a possible implementation, the compensation amount determination module 33 is specifically used to:

[0134] Before determining the compensation amount of the angular frequency according to the current difference, comparing the current difference with the preset current limit threshold;

[0135] If the current difference is less than the preset current limit point threshold, the compensation amount of the angular frequency is determined according to the current difference.

[0136] In a possible implementation, the compensation amount determination module 33 is further configured to:

[0137] If the current difference is greater than or equal to the preset current limit point threshold, the compensation amount of the angular frequency is determined to be 0.

[0138] In a possible implementation, the compensation module 34 is specifically configured to:

[0139] The angular frequency reference value of the grid-connected converter is subtracted from the angular frequency compensation amount to obtain a compensated angular frequency reference value.

[0140] In a possible implementation, the current limiting control module 35 is specifically used to:

[0141] Determine a phase angle reference value according to the compensated angular frequency reference value;

[0142] Obtaining a voltage amplitude reference value output by a voltage regulation control loop;

[0143] Determine three-phase voltage reference values ​​according to the phase angle reference value and the voltage amplitude reference value;

[0144] Input the three-phase voltage reference value into the voltage and current double closed-loop control loop to obtain the control quantity of the grid-connected converter;

[0145] According to the control quantity of the grid-connected converter, the grid-connected converter is controlled.

[0146] Figure 6 Schematic diagram of an electronic device provided by an embodiment of the present invention. Figure 6 As shown, the electronic device 4 of this embodiment includes: a processor 40 and a memory 41. The memory 41 is used to store a computer program 42, and the processor 40 is used to call and run the computer program 42 stored in the memory 41 to perform the steps in the above-mentioned current limiting method embodiments based on active power compensation, for example Figure 2 Alternatively, the processor 40 is used to call and run the computer program 42 stored in the memory 41 to implement the functions of each module / unit in the above-mentioned device embodiments, for example Figure 5 The functions of each module are shown.

[0147] Exemplarily, the computer program 42 may be divided into one or more modules / units, which are stored in the memory 41 and executed by the processor 40 to implement the present invention. The one or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, which are used to describe the execution process of the computer program 42 in the electronic device 4. For example, the computer program 42 may be divided into Figure 5 The modules shown.

[0148] The electronic device 4 may include, but is not limited to, a processor 40 and a memory 41. Those skilled in the art will appreciate that Figure 6 It is only an example of the electronic device 4 and does not constitute a limitation of the electronic device 4. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the electronic device may also include input and output devices, network access devices, buses, etc.

[0149] The processor 40 may be a central processing unit (CPU), or 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. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0150] The memory 41 may be an internal storage unit of the electronic device 4, such as a hard disk or memory of the electronic device 4. The memory 41 may also be an external storage device of the electronic device 4, such as 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 may also include both an internal storage unit and an external storage device of the electronic device 4. The memory 41 is used to store the computer program and other programs and data required by the electronic device. The memory 41 may also be used to temporarily store data that has been output or is to be output.

[0151] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0152] Corresponding to the above-mentioned electronic device, an embodiment of the present application further provides a grid-type converter, comprising the above-mentioned electronic device.

[0153] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0154] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0155] In the embodiments provided by the present invention, it should be understood that the disclosed devices / electronic devices and methods can be implemented in other ways. For example, the device / electronic device embodiments described above are only schematic. For example, the division of the modules or units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0156] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0157] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0158] If the integrated module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, the steps of the above-mentioned current limiting method embodiments based on active power compensation can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium.

[0159] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A current limiting method based on active power compensation, characterized in that: include: Obtain the current actual current value and the maximum allowable current value of the grid-connected converter; Determine the current difference between the maximum allowable current value and the current actual current value; Determining a compensation amount of an angular frequency according to the current difference; The compensation amount of the angular frequency is negatively correlated with the current difference; Compensating the angular frequency reference value of the grid-connected converter according to the angular frequency compensation amount to obtain a compensated angular frequency reference value; The grid-connected converter is controlled in a grid-type manner according to the compensated angular frequency reference value.

2. The current limiting method based on active power compensation according to claim 1, characterized in that: Determining the compensation amount of the angular frequency according to the current difference includes: Based on the inverse proportional function, the compensation amount of the angular frequency is determined according to the current difference.

3. The current limiting method based on active power compensation according to claim 1, characterized in that: Determining the compensation amount of the angular frequency according to the current difference includes: Obtaining an actual value of a D-axis current component of the grid-connected converter; Determine a ratio of an actual value of the D-axis current component to the current actual current value; The compensation amount of the angular frequency is determined according to the ratio and the current difference; the compensation amount of the angular frequency is positively correlated with the ratio.

4. The current limiting method based on active power compensation according to claim 1, characterized in that: Before determining the compensation amount of the angular frequency according to the current difference, the current limiting method based on active power compensation further includes: Comparing the current difference with a preset current limiting point threshold; Accordingly, determining the compensation amount of the angular frequency according to the current difference includes: If the current difference is less than the preset current limiting point threshold, the compensation amount of the angular frequency is determined according to the current difference.

5. The current limiting method based on active power compensation according to claim 4 is characterized in that: After comparing the current difference with the preset current limiting point threshold, the current limiting method based on active power compensation further includes: If the current difference is greater than or equal to the preset current limiting point threshold, the compensation amount of the angular frequency is determined to be 0.

6. The current limiting method based on active power compensation according to claim 1, characterized in that: The compensating 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 includes: The angular frequency reference value of the grid-connected converter is subtracted from the angular frequency compensation amount to obtain a compensated angular frequency reference value.

7. The current limiting method based on active power compensation according to any one of claims 1 to 6, characterized in that: The grid-connected converter is controlled according to the compensated angular frequency reference value, comprising: 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 dual closed-loop control loop to obtain a control quantity of the grid-connected converter; According to the control quantity of the grid-connected converter, the grid-connected converter is subjected to grid-connected control.

8. A current limiting device based on active power compensation, characterized in that: include: An acquisition module is used to obtain the current actual current value and the maximum allowable current value of the grid-connected converter; A current difference determination module, used to determine the current difference between the maximum allowable current value and the current actual current value; A compensation amount determination module, used to determine the compensation amount of the angular frequency according to the current difference; The compensation amount of the angular frequency is negatively correlated with the current difference; A compensation module, used for compensating the 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; The current limiting control module is used to perform grid-type control on the grid-connected converter according to the compensated angular frequency reference value.

9. An electronic device, characterized in that: It comprises a memory and a processor, the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the current limiting method based on active power compensation as described in any one of claims 1 to 7.

10. A grid-type converter, characterized in that: Comprising the electronic device as claimed in claim 9.

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