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

Abstract

A reactive power enhancement control method applicable to a grid-connected converter, and related apparatuses. The method comprises: constructing a reactive power enhancement control strategy applicable to a grid-forming converter; and constructing a reactive power enhancement control strategy applicable to a grid-following converter. A reactive power enhancement control strategy applicable to a grid-forming converter in the present application can enhance the transient reactive power support capability of the grid-forming converter without requiring control switching, and can effectively suppress the risk of active power backflow in the grid-forming converter. A reactive power enhancement control strategy applicable to a grid-following converter in the present application can more fully exploit the reactive power support potential of the converter.

Description

Reactive power enhancement control methods and related devices applicable to grid-connected converters

[0001] This application claims priority to Chinese Patent Application No. 202510063662.1, filed on January 15, 2025, entitled "Reactive Power Enhancement Control Method and Related Device Applicable to Grid-Connected Converters", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of power system transient stability technology, and in particular to a reactive power enhancement control method and related device applicable to grid-connected converters. Background Technology

[0003] With the global transition to low-carbon energy, the proportion of grid-connected converters in power systems is increasing, 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 also be divided into the following two categories:

[0004] (1) Research on transient reactive power control of grid-connected converters mainly falls into two categories: First, achieving maximum support for the terminal voltage by setting the current phase to the optimal phase, but this control method relies on communication. Second, enhancing the reactive power support of the grid-connected converter by adjusting the reactive power loop droop coefficient. However, neither of these studies considers improving the reactive power support capability of the grid-connected converter from the perspective of the active power loop. (2) Research on transient reactive power control of grid-connected converters mainly falls into two categories: First, switching the GFL to reactive power priority control mode during low voltage periods and adjusting the reactive power output according to the voltage level, but this method does not fully utilize the reactive power potential of the GFL. Second, introducing additional Pf and QV droop loops to transform the external characteristics of the GFL into a voltage source to enhance its reactive power support capability, but the improved GFL may not be as good as the GFM in terms of voltage and frequency support and is less economically valuable than the traditional GFL.

[0005] Therefore, there is an urgent need to design a grid-connected converter control method that can enhance the transient reactive power support capability of grid-connected converters, effectively suppress the risk of reactive power backflow of grid-connected converters, and more fully tap the reactive power support potential of converters. Summary of the Invention

[0006] This application provides a reactive power enhancement control method and related device applicable to grid-connected converters, which enhances the transient reactive power support capability of grid-connected converters, effectively suppresses the risk of active power backflow of grid-connected converters, and more fully taps the reactive power support potential of converters.

[0007] In view of this, the first aspect of this application provides a reactive power enhancement control method applicable to grid-connected converters, the method comprising:

[0008] The first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter is collected;

[0009] Based on the first actual voltage amplitude, the active power command value of the grid converter is designed, thereby constructing the first reactive power enhancement control strategy for reactive power enhancement control of the grid converter.

[0010] Collect the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter;

[0011] Based on the second actual voltage amplitude, a q-axis current command for the grid-connected 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 reactive power enhancement control of the grid-connected converter.

[0012] Optionally, the expression for the active power command value of the grid converter is:

[0013] In the formula, U PCC1 P is the first actual voltage amplitude. ref0 K represents the steady-state active power command value before the fault. Vq U is a constant. sq This refers to the q-axis component of the low-voltage side node voltage of the step-up transformer in a grid converter.

[0014] Optionally, the expression for the q-axis current command of the grid-connected converter is as follows:

[0015] In the formula, U PCC2 i is the second actual voltage amplitude. qref This is the q-axis current.

[0016] Optionally, the suppression of q-axis current oscillations through the filter includes:

[0017] Before the q-axis current command enters the inner current loop, the q-axis current command is controlled to pass through a first-order filter to suppress i qref The oscillation.

[0018] A second aspect of this application provides a reactive power enhancement control system suitable for grid-connected converters, the system comprising:

[0019] The first acquisition unit is used to acquire the first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0020] The first control unit is used to design the 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 reactive power enhancement control of the grid converter.

[0021] The second acquisition unit is used to acquire the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0022] The second control unit is used to design the q-axis current command of the grid-connected converter based on the second actual voltage amplitude, and to suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for reactive power enhancement control of the grid-connected converter.

[0023] Optionally, the expression for the active power command value of the grid converter is:

[0024] In the formula, U PCC1 P is the first actual voltage amplitude. ref0 K represents the steady-state active power command value before the fault. Vq U is a constant. sq This refers to the q-axis component of the low-voltage side node voltage of the step-up transformer in a grid converter.

[0025] Optionally, the expression for the q-axis current command of the grid-connected converter is as follows:

[0026] In the formula, U PCC2 i is the second actual voltage amplitude. qref This is the q-axis current.

[0027] Optionally, the oscillation of the q-axis current is suppressed by a filter, including:

[0028] Before the q-axis current command enters the inner current loop, the q-axis current command is controlled to pass through a first-order filter to suppress i qref The oscillation.

[0029] A third aspect of this application provides a reactive power enhancement control device suitable for grid-connected converters, the device comprising a processor and a memory:

[0030] The memory is used to store program code and transmit the program code to the processor;

[0031] The processor is configured to execute, according to the instructions in the program code, the steps of the reactive power enhancement control method for grid-connected converters as described in the first aspect above.

[0032] A fourth aspect of this application provides a computer-readable storage medium for storing program code for executing the reactive power enhancement control method for grid-connected converters described in the first aspect above.

[0033] As can be seen from the above technical solutions, this application has the following advantages:

[0034] 1) The reactive power enhancement control strategy applicable to grid-connected converters in this application can enhance the transient reactive power support capability of grid-connected converters without control switching, and effectively suppress the risk of active power backflow of grid-connected converters.

[0035] 2) The reactive power enhancement control strategy for grid-connected converters in this application can more fully tap the reactive power support potential of the converters. Attached Figure Description

[0036] Figure 1 is a flowchart illustrating a reactive power enhancement control method for grid-connected converters provided in an embodiment of this application;

[0037] Figure 2 is a reactive power enhancement control diagram applicable to grid converters provided in the embodiments of this application;

[0038] Figure 3 is a reactive power enhancement control diagram applicable to grid-connected converters provided in the embodiments of this application;

[0039] Figure 4 is a diagram of a multi-machine two-area system provided in an embodiment of this application;

[0040] Figure 5 is a graph of the active power of the grid converter provided in the embodiment of this application;

[0041] Figure 6 is a reactive power curve of the grid converter provided in the embodiment of this application;

[0042] Figure 7 is a reactive power curve of the grid-connected converter provided in the embodiment of this application;

[0043] Figure 8 is a schematic diagram of a reactive power enhancement control system for grid-connected converters provided in an embodiment of this application. Detailed Implementation

[0044] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0045] Please refer to Figures 1, 2, and 3. An embodiment of this application provides a reactive power enhancement control method suitable for grid-connected converters, comprising:

[0046] Step 101: Collect the first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0047] It should be noted that the actual voltage amplitude U on the high-voltage side of the step-up transformer of the grid converter is collected. PCC1 (Per unit value)

[0048] Step 102: Based on the first actual voltage amplitude, design the active power command value of the grid converter, thereby constructing the first reactive power enhancement control strategy for reactive power enhancement control of the grid converter.

[0049] In one embodiment, the expression for the active power command value of the designed grid converter is:

[0050] In the formula, U PCC1 P is the first actual voltage amplitude. ref0 K represents the steady-state active power command value before the fault. Vq U is a constant. sq This refers to the q-axis component of the low-voltage side node voltage of the step-up transformer in a grid converter.

[0051] It should be noted that by adaptively reducing the active power command value during transient periods, the transient reactive power support capability of the grid converter can be increased. This is achieved by introducing U... sq The square of this value can enhance the grid converter's control over active power during transient periods, thereby suppressing the risk of active power backflow caused by a decrease in active power command, and simultaneously suppressing... Negative impact on active power recovery of grid-connected converters.

[0052] In this embodiment, the grid converter is a converter controlled by a virtual synchronous machine, P ref0 =0.8, K Vq =2.

[0053] Step 103: Collect the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0054] It should be noted that the data collected is the actual voltage amplitude U on the high-voltage side of the step-up transformer of the grid converter. PCC2 (Per unit value)

[0055] Step 104: Based on the second actual voltage amplitude, design the q-axis current command of the grid-connected converter, and suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for reactive power enhancement control of the grid-connected converter.

[0056] In one embodiment, the expression for the q-axis current command of the grid-connected converter is as follows:

[0057] In the formula, U PCC2 i is the second actual voltage amplitude. qref This is the q-axis current.

[0058] In one embodiment, suppressing oscillations in the q-axis current through a filter includes: controlling the q-axis current command to pass through a first-order filter (a first-order low-pass digital filter in the art) before it enters the inner current loop to suppress i qref The oscillation.

[0059] As shown in Figure 3, when U PCC2 If U < 0.8, then N0 = 1; otherwise, N0 = 1. PCC2 If the value is less than 0.9, then N1 = 1; otherwise, N1 = 0.

[0060] The following are simulation examples provided in this application:

[0061] To verify the proposed reactive power enhancement control strategy applicable to grid-connected converters, the number of synchronous machines G1, G2, G3, G4, and G5 in the system shown in Figure 4 was set to 4, 4, 3, 1, and 4, respectively. The rated capacity and active power of each synchronous machine were 360 ​​MVA and 288 MW, respectively. A virtual synchronous machine with a capacity of 864 MW was connected to the R bus to control the converter. The fault was set as follows: a three-phase short circuit fault occurred on the L side of a certain line at section KL at 0.1 s, and the circuit breakers on both sides of the line tripped after 0.1 s. Two simulation experimental groups were set up. One experimental group adopted the control strategy proposed in this invention, called GFM Experimental Group 1, and the other experimental group did not adopt it, called GFM Experimental Group 2. The simulation results are shown in Figures 5 and 6.

[0062] As shown in Figure 5, the strategy proposed in this invention can effectively suppress the risk of active power backflow in grid-connected converters. As shown in Figure 6, the strategy proposed in this invention can enhance the transient reactive power support capability of grid-connected converters.

[0063] To verify the proposed reactive power enhancement control strategy applicable to grid-connected converters, the number of synchronous generators for G1, G2, G3, G4, and G5 in the system shown in Figure 4 was set to 4, 4, 3, 1, and 1 respectively. 864MW grid-connected converters were connected to the R and P buses respectively. Fault settings were the same as above. Two simulation experimental groups were set up: one experimental group adopted the control strategy proposed in this invention, referred to as GFL Experimental Group 1, and the other experimental group adopted the reactive power control strategy for grid-connected converters required by national standards, referred to as GFL Experimental Group 2. The simulation results are shown in Figure 7. As can be seen from Figure 7, the strategy proposed in this application can enhance the transient reactive power support capability of grid-connected converters.

[0064] This application provides reactive power enhancement control strategies for grid-connected converters, including: constructing a reactive power enhancement control strategy suitable for grid-connected converters; and constructing a reactive power enhancement control strategy suitable for grid-connected converters. The reactive power enhancement control strategy for grid-connected converters in this application can enhance the transient reactive power support capability of grid-connected converters without control switching, and effectively suppress the active power backflow risk of grid-connected converters. The reactive power enhancement control strategy for grid-connected converters in this application can more fully tap the reactive power support potential of the converters.

[0065] The above is a reactive power enhancement control method for grid-connected converters provided in the embodiments of this application. The following is a reactive power enhancement control system for grid-connected converters provided in the embodiments of this application.

[0066] Please refer to Figure 8. An embodiment of this application provides a reactive power enhancement control system suitable for grid-connected converters, comprising:

[0067] The first acquisition unit 201 is used to acquire the first actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0068] The first control unit 202 is used to design the 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 reactive power enhancement control of the grid converter.

[0069] The second acquisition unit 203 is used to acquire the second actual voltage amplitude on the high-voltage side of the step-up transformer of the grid converter.

[0070] The second control unit 204 is used to design the q-axis current command of the grid-connected converter based on the second actual voltage amplitude, and to suppress the oscillation of the q-axis current through a filter, thereby constructing a second reactive power enhancement control strategy for reactive power enhancement control of the grid-connected converter.

[0071] Furthermore, this application embodiment also provides a reactive power enhancement control method and device suitable for grid-connected converters, the device including a processor and a memory:

[0072] The memory is used to store program code and transmit the program code to the processor;

[0073] The processor is used to execute the steps of the reactive power enhancement control method for grid-connected converters as described in the above method embodiments, according to the instructions in the program code.

[0074] Furthermore, this application embodiment also provides a computer-readable storage medium for storing program code, which is used to execute the reactive power enhancement control method for grid-connected converters described in the above method embodiments.

[0075] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0076] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0077] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0078] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0079] The units described as separate components may or may not be physically separate. 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 the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0080] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0081] If the integrated unit is implemented as 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 this application, in essence, 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. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes: USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, optical disks, and other media capable of storing program code.

[0082] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method of reactive power boost control suitable for a grid-connected converter, characterized in that, The method comprises: collecting a first actual voltage amplitude of a high-voltage side of a step-up transformer of a grid-forming converter; designing an active power instruction value of the grid-forming 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-forming converter; collecting a second actual voltage amplitude of a high-voltage side of a step-up transformer of a grid-following converter; designing a q-axis current instruction of the grid-following converter based on the second actual voltage amplitude, and suppressing 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.

2. The method for reactive power boost control suitable for grid-tie converters as claimed in claim 1, wherein, An expression of the active power instruction value of the network construction converter is: wherein U PCC1 is the first actual voltage magnitude, P ref0 is the pre-fault steady state active power command value, K Vq is a constant, U sq is the q-axis component of the grid-forming converter step-up transformer low voltage side node voltage.

3. The method for reactive power boost control suitable for grid-tie converters as claimed in claim 1, wherein, An expression of a q-axis current instruction of the grid-side converter is, including: In the formula, U PCC2 is the second actual voltage amplitude, i qref is the q-axis current.

4. The method for reactive power boost control suitable for grid-tie converters as claimed in claim 3, wherein, The suppressing of the oscillation of the q-axis current through the filter comprises: Before the q-axis current command enters the current inner loop, the q-axis current command is filtered by a first-order filter to suppress the oscillation of i qref .

5. A reactive power boost control system suitable for use with a grid-tie converter, characterized by, The method comprises: a first collecting unit configured to collect a first actual voltage amplitude of a high-voltage side of a step-up transformer of a grid-forming converter; a first control unit configured to design an active power instruction value of the grid-forming 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-forming converter; a second collecting unit configured to collect a second actual voltage amplitude of a high-voltage side of a step-up transformer of a grid-following converter; a second control unit configured to design a q-axis current instruction of the grid-following converter based on the second actual voltage amplitude, and suppress 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.

6. The reactive power boost control system suitable for use with a grid-tie converter of claim 5, wherein, An expression of the active power instruction value of the network construction converter is: wherein U PCC1 is the first actual voltage magnitude, P ref0 is the pre-fault steady state active power command value, K Vq is a constant, U sq is the q-axis component of the network-forming converter step-up transformer low-voltage side node voltage.

7. The reactive power boost control system suitable for use with a grid-tie converter of claim 5, wherein, An expression of a q-axis current instruction of the grid-side converter is, including: In the formula, U PCC2 is the second actual voltage amplitude, i qref is the q-axis current.

8. The reactive power boost control system suitable for use with a grid-tie converter of claim 5, wherein, The suppressing of the oscillation of the q-axis current through the filter comprises: Before the q-axis current command enters the current inner loop, the q-axis current command is filtered by a first-order filter to suppress the oscillation of i qref .

9. A reactive power boost control device suitable for use with a grid- connected converter, characterized by, The device comprises a processor and a memory: The memory is configured to store program code and transmit the program code to the processor; The processor is configured to execute the instructions in the program code to perform the method for reactive power enhancement control on a grid-connected converter according to any one of claims 1-4.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is configured to store program code for performing the method for reactive power enhancement control on a grid-connected converter according to any one of claims 1-4.

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