Reactive power enhancement control method and related device applicable to grid-connected converter

Abstract

The present application discloses a reactive power enhancement control method and related devices applicable to grid-connected converters, including: constructing a reactive power enhancement control strategy applicable to grid-connected converters; constructing a reactive power enhancement control strategy applicable to grid-following converters. The reactive power enhancement control strategy applicable to grid-connected converters of the present application can enhance the transient reactive power support capability of the grid-connected converter without the need for control switching, and effectively suppress the risk of active power backflow of the grid-connected converter. The reactive power enhancement control strategy applicable to grid-following converters of the present application can more fully tap the reactive power support potential of the converter.

Description

Technical Field

[0001] The present application relates to the technical field of transient stability of power systems, and in particular to a reactive power enhancement control method and related devices applicable to grid-connected converters. Background Art

[0002] With the global transition to low-carbon energy, grid-connected converters are becoming increasingly important in power systems, and their impact on system transient voltage stability cannot be ignored. Grid-connected converters can generally be divided into two categories: grid-forming (GFM) and grid-following (GFL). Therefore, research on their reactive power and voltage control can be divided into the following two categories:

[0003] (1) There are two main studies on transient reactive power control of grid-connected converters. First, the current phase is set to the optimal phase to achieve maximum support for the node voltage, but this control method relies on communication. Second, the reactive power support of the grid-connected converter is enhanced by adjusting the reactive loop sag coefficient. However, these studies do not consider improving the reactive power support capability of the grid-connected converter from the perspective of the active loop. (2) There are two main studies on transient reactive power control of grid-connected converters. First, the GFL is switched to reactive power priority control mode during low voltage periods and reactive power output is adjusted according to the voltage level, but this method does not fully utilize the reactive power potential of the GFL. Second, additional Pf and QV droop loops are introduced to transform the external characteristics of the GFL into a voltage source to enhance its reactive power support capability. However, the improved GFL may not be as good as the GFM in voltage and frequency support and is not as economically valuable as the traditional GFL.

[0004] Therefore, it is urgent to design a grid-connected converter control method that can enhance the transient reactive power support capability of the grid-connected converter, effectively suppress the active power backflow risk of the grid-connected converter, and more fully tap the reactive power support potential of the converter. Summary of the Invention

[0005] The present application provides a reactive power enhancement control method and related devices applicable to a grid-connected converter, which are used to enhance the transient reactive power support capability of the grid-connected converter, effectively suppress the active power backflow risk of the grid-connected converter, and more fully tap the reactive power support potential of the converter.

[0006] In view of this, a first aspect of the present application provides a reactive power enhancement control method applicable to a grid-connected converter, the method comprising:

[0007] Collecting the first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-connected converter;

[0008] Based on the first actual voltage amplitude, an active power command value of the grid converter is designed, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter;

[0009] Collect the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter;

[0010] Based on the second actual voltage amplitude, a q-axis current command of the grid-following converter is designed, and the oscillation of the q-axis current is suppressed by a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter.

[0011] Optionally, the expression of the active power command value of the grid-connected converter is:

[0012] ;

[0013] Where, is the first actual voltage amplitude, is the steady-state active power command value before the fault, is a constant, is the voltage of the low voltage side node of the step-up transformer of the grid converter Axis component.

[0014] Optionally, the expression of the q-axis current instruction of the grid-following converter is, including:

[0015] ;

[0016] Where, is the second actual voltage amplitude, is the q-axis current.

[0017] Optionally, suppressing the oscillation of the q-axis current by using a filter includes:

[0018] Before the q-axis current command enters the current inner loop, the q-axis current command is controlled to pass through a first-order filter to suppress oscillation.

[0019] A second aspect of the present application provides a reactive power enhancement control system applicable to a grid-connected converter, the system comprising:

[0020] A first acquisition unit is used to acquire a first actual voltage amplitude on the high-voltage side of a step-up transformer of a grid-connected converter;

[0021] a first control unit, configured to design an active power command value of the grid converter based on the first actual voltage amplitude, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter;

[0022] A second acquisition unit is used to acquire a second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter;

[0023] The second control unit is used to design the q-axis current instruction of the grid-following converter based on the second actual voltage amplitude, and suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter.

[0024] Optionally, the expression of the active power command value of the grid-connected converter is:

[0025] ;

[0026] Where, is the first actual voltage amplitude, is the steady-state active power command value before the fault, is a constant, is the voltage of the low voltage side node of the step-up transformer of the grid converter Axis component.

[0027] Optionally, the expression of the q-axis current instruction of the grid-following converter is, including:

[0028] ;

[0029] Where, is the second actual voltage amplitude, is the q-axis current.

[0030] Optionally, the oscillation of the q-axis current is suppressed by a filter, including:

[0031] Before the q-axis current command enters the current inner loop, the q-axis current command is controlled to pass through a first-order filter to suppress oscillation.

[0032] A third aspect of the present application provides a reactive power enhancement control device applicable to a grid-connected converter, the device comprising a processor and a memory:

[0033] The memory is used to store program code and transmit the program code to the processor;

[0034] The processor is configured to execute the steps of the reactive power enhancement control method applicable to a grid-connected converter as described in the first aspect above according to the instructions in the program code.

[0035] In a fourth aspect, the present application provides a computer-readable storage medium, which is used to store program code, and the program code is used to execute the reactive power enhancement control method applicable to the grid-connected converter described in the first aspect.

[0036] It can be seen from the above technical solutions that this application has the following advantages:

[0037] 1) The reactive power enhancement control strategy applied to the grid-connected converter in this application can enhance the transient reactive power support capability of the grid-connected converter without control switching, and effectively suppress the active power backflow risk of the grid-connected converter.

[0038] 2) The reactive power enhancement control strategy for the grid-following converter of the present application can more fully tap the reactive power support potential of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flowchart of a reactive power enhancement control method applicable to a grid-connected converter provided in an embodiment of the present application;

[0040] Figure 2 A reactive power enhancement control diagram applicable to a grid-connected converter provided in an embodiment of the present application;

[0041] Figure 3 A reactive power enhancement control diagram applicable to a grid-following converter provided in an embodiment of the present application;

[0042] Figure 4 This is a diagram of a multi-machine two-area system provided in an embodiment of the present application;

[0043] Figure 5 This is a graph showing the active power curve of the grid-connected converter provided in an embodiment of the present application;

[0044] Figure 6 This is a reactive power curve diagram of the grid-connected converter provided in an embodiment of the present application;

[0045] Figure 7 This is a reactive power curve diagram of the grid-connected converter provided in an embodiment of the present application;

[0046] Figure 8 This is a structural diagram of a reactive power enhancement control system suitable for a grid-connected converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0048] See also Figure 1 、 Figure 2 、 Figure 3 , a reactive power enhancement control method applicable to a grid-connected converter provided in an embodiment of the present application includes:

[0049] Step 101: Collect a first actual voltage amplitude on the high-voltage side of a step-up transformer of a grid-connected converter.

[0050] It should be noted that the actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter is collected. (Per unit value).

[0051] Step 102: Based on the first actual voltage amplitude, design an active power command value of the grid converter, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter.

[0052] In one embodiment, the expression of the active power command value of the designed grid converter is:

[0053] ;

[0054] Where, is the first actual voltage amplitude, is the steady-state active power command value before the fault, is a constant, is the voltage of the low voltage side node of the step-up transformer of the grid converter Axis component.

[0055] It should be noted that by adaptively reducing the active power command value during the transient period, the transient reactive power support capability of the grid converter can be increased. The square of the active power can enhance the control of the grid converter on the active power during the transient period, thereby suppressing the risk of active power backflow caused by the decrease of active power instruction, and at the same time suppressing Negative impact on active power recovery of grid converters.

[0056] In this embodiment, the grid-connected converter is a converter controlled by a virtual synchronous machine. , .

[0057] Step 103: Acquire a second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter.

[0058] It should be noted that the actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter is collected. (Per unit value).

[0059] Step 104: Based on the second actual voltage amplitude, design a q-axis current command for the grid-following converter, and suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter.

[0060] In one embodiment, the designed expression of the q-axis current instruction of the grid-following converter is as follows:

[0061] ;

[0062] Where, is the second actual voltage amplitude, is the q-axis current.

[0063] In one embodiment, the oscillation of the q-axis current is suppressed by a filter, including: before the q-axis current command enters the current inner loop, controlling the q-axis current command to pass through a first-order filter (a first-order low-pass digital filter in the art) to suppress oscillation.

[0064] like Figure 3 As shown, when ,but ,otherwise .when , ,otherwise .

[0065] The following is a simulation example provided in this application:

[0066] In order to verify the proposed reactive power enhancement control strategy for grid-connected converters, we set Figure 4 The number of synchronous machines in the system G1, G2, G3, G4, and G5 is 4, 4, 3, 1, and 4, and the rated capacity and active power of each synchronous machine are 360MVA and 288MW respectively. A virtual synchronous machine of 864MW is connected to the R bus to control the converter. The fault setting is: a three-phase short circuit fault occurs on the L side of a certain line of section KL at 0.1s, and the circuit breakers on both sides of the line trip after 0.1s. Two simulation experimental groups are set up, one experimental group adopts the control strategy proposed by the present invention, called GFM experimental group 1, and the other experimental group does not adopt it, called GFM experimental group 2. The simulation results are shown in Figure 5 and Figure 6 .

[0067] from Figure 5 It can be seen that the strategy proposed in this invention can effectively suppress the risk of active power backflow in the grid-connected converter. Figure 6 It can be seen that the strategy proposed in the present invention can enhance the transient reactive power support capability of the grid-connected converter.

[0068] In order to verify the proposed reactive power enhancement control strategy for grid-following converter, we set Figure 4 The number of synchronous machines in the system G1, G2, G3, G4, and G5 is 4, 4, 3, 1, and 1, and the R bus and P bus are connected to 864MW grid-following converters respectively. The fault setting is the same as above. Two simulation experiment groups are set up, one experiment group adopts the control strategy proposed by the present invention, called GFL experiment group 1, and the other experiment group adopts the grid-following converter reactive power control strategy required by the national standard, called GFL experiment group 2. The simulation results are shown in Figure 7 .from Figure 7 It can be seen that the strategy proposed in this application can enhance the transient reactive power support capability of the grid-connected converter.

[0069] The reactive power enhancement control strategy for grid-connected converters provided in the present application includes: constructing a reactive power enhancement control strategy for grid-connected converters; constructing a reactive power enhancement control strategy for grid-following converters. The reactive power enhancement control strategy for grid-connected converters in the present application can enhance the transient reactive power support capability of the grid-connected converter without the need for control switching, and effectively suppress the risk of active power backflow of the grid-connected converter. The reactive power enhancement control strategy for grid-following converters in the present application can more fully tap the reactive power support potential of the converter.

[0070] The above is a reactive power enhancement control method applicable to a grid-connected converter provided in an embodiment of the present application. The following is a reactive power enhancement control system applicable to a grid-connected converter provided in an embodiment of the present application.

[0071] See also Figure 8 , a reactive power enhancement control system applicable to a grid-connected converter provided in an embodiment of the present application includes:

[0072] The first acquisition unit 201 is used to acquire a first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-connected converter;

[0073] A first control unit 202 is configured to design an active power command value of the grid converter based on the first actual voltage amplitude, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter;

[0074] The second acquisition unit 203 is used to acquire a second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter;

[0075] The second control unit 204 is used to design the q-axis current instruction of the grid-following converter based on the second actual voltage amplitude, and suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter.

[0076] Furthermore, an embodiment of the present application also provides a reactive power enhancement control method device applicable to a grid-connected converter, the device including a processor and a memory:

[0077] The memory is used to store program code and transmit the program code to the processor;

[0078] The processor is configured to execute the steps of the reactive power enhancement control method applicable to a grid-connected converter as described in the above method embodiment according to the instructions in the program code.

[0079] Furthermore, a computer-readable storage medium is provided in an embodiment of the present application, and the computer-readable storage medium is used to store program code, and the program code is used to execute the reactive power enhancement control method applicable to the grid-connected converter described in the above method embodiment.

[0080] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0081] The terms "first," "second," "third," "fourth," and the like (if any) in the specification of the present application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.

[0082] It should be understood that in this application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or plural.

[0083] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, 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 an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0084] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0085] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0086] If the integrated 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 technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (full name: Read-Only Memory, English abbreviation: ROM), random access memory (full name: Random Access Memory, English abbreviation: RAM), disk or optical disk, and other media that can store program code.

[0087] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these 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 application.

Claims

1. A reactive power enhancement control method applicable to a grid-connected converter, characterized in that: include: Collecting the first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-connected converter; Based on the first actual voltage amplitude, an active power command value of the grid converter is designed, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter; Collect the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter; Based on the second actual voltage amplitude, a q-axis current command of the grid-following converter is designed, and oscillations of the q-axis current are suppressed by a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter; The expression of the active power command value of the grid-connected converter is: ； Where, is the first actual voltage amplitude, is the steady-state active power command value before the fault, is a constant, is the voltage of the low voltage side node of the step-up transformer of the grid converter Axis component; The expression of the q-axis current instruction of the grid-following converter is as follows: ； Where, is the second actual voltage amplitude, is the q-axis current.

2. The reactive power enhancement control method applicable to the grid-connected converter according to claim 1, characterized in that: The suppressing of the oscillation of the q-axis current by the filter includes: Before the q-axis current command enters the current inner loop, the q-axis current command is controlled to pass through a first-order filter to suppress oscillation.

3. A reactive power enhancement control system suitable for grid-connected converters, characterized in that: include: A first acquisition unit is used to acquire a first actual voltage amplitude on the high-voltage side of a step-up transformer of a grid-connected converter; a first control unit, configured to design an active power command value of the grid converter based on the first actual voltage amplitude, thereby constructing a first reactive power enhancement control strategy for performing reactive power enhancement control on the grid converter; A second acquisition unit is used to acquire a second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid-following converter; a second control unit, configured to design a q-axis current command for the grid-following converter based on the second actual voltage amplitude, and suppress oscillations of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for performing reactive power enhancement control on the grid-following converter; The expression of the active power command value of the grid-connected converter is: ； Where, is the first actual voltage amplitude, is the steady-state active power command value before the fault, is a constant, is the voltage of the low voltage side node of the step-up transformer of the grid converter Axis component; The expression of the q-axis current instruction of the grid-following converter is as follows: ； Where, is the second actual voltage amplitude, is the q-axis current.

4. The reactive power enhancement control system applicable to the grid-connected converter according to claim 3, characterized in that: The oscillation of the q-axis current is suppressed by the filter, including: Before the q-axis current command enters the current inner loop, the q-axis current command is controlled to pass through a first-order filter to suppress oscillation.

5. A reactive power enhancement control device suitable for a grid-connected converter, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the reactive power enhancement control method applicable to the grid-connected converter according to any one of claims 1-2 according to the instructions in the program code.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program code, and the program code is used to execute the reactive power enhancement control method applicable to a grid-connected converter according to any one of claims 1-2.

Images