A method, device, equipment and storage medium for determining MMC overload boundary

Abstract

The present invention provides a method, device, equipment and storage medium for determining the overload boundary of an MMC, and belongs to the field of direct current transmission technology. The method includes: obtaining the power factor angle of a target MMC, and setting the constraint range of the zero-sequence signal amplitude and phase angle; initializing two different working conditions of the target MMC, and determining the maximum modulation signal margin of the two different working conditions under the condition of injecting a zero-sequence signal; based on the maximum modulation signal margin under the two different conditions, determining the maximum operating power of the target MMC under the current power factor angle by the chord intercept method; adjusting the power factor angle, and obtaining the overload operation limit boundary of the target MMC. In this way, the overload operation boundary of the target MMC can be clearly obtained, the modulation signal margin of the MMC can be obtained according to the zero-sequence signal, and then the maximum operating power and the starting operating power can be determined, and the overload operation boundary of the MMC can be accurately determined, which helps to reasonably set the load level of the MMC during the design and operation process to ensure safe and efficient operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of direct current transmission, and in particular relates to a method, a device, a equipment and a storage medium for determining an MMC overload boundary. Background Art

[0002] Modular Multilevel Converter (MMC) is a new type of power electronic converter with the characteristics of high voltage utilization, good control performance, high operating efficiency, good scalability and redundancy, and is widely used in high-voltage direct current transmission (HVDC) and renewable energy access. In addition to the flexibility of MMC, the grid-type MMC has the characteristics of grid-type converters that can provide system inertia support and improve the stability and reliability of the power system. It is an important part of promoting the construction of new power systems with a high proportion of new energy. When faced with sudden load demands and power fluctuations, if the equipment cannot withstand the overload demand and shutdown, it will cause power supply interruption and equipment damage, affecting the stable operation of the entire power grid. Therefore, the grid-type MMC needs to have a certain overload operation capability.

[0003] The clear construction of the overload operation boundary is crucial for the stable operation of the converter, because it is not only the trigger condition for the subsequent overload operation control, but also the basic guarantee to prevent the MMC from exceeding the operating limit. In the context of the increasing complexity of the power system and the ever-changing load demand, establishing a clear overload boundary can not only improve the reliability of the MMC, but also enhance the system's ability to respond to various power shocks. Constructing the overload operation boundary of the grid-type MMC has important practical significance for improving the overall safety and stability of the power system.

[0004] In the prior art, the determination of the overload boundary of the MMC is mainly estimated based on the historical operating data of the MMC, resulting in unclear and inaccurate operating data of the MMC overload boundary. Summary of the invention

[0005] In order to solve the problem that the overload boundary of the MMC is unclear, the present invention provides a method, an apparatus, a device and a storage medium for determining the overload boundary of the MMC.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] First, a method for determining an MMC overload boundary is provided, the method comprising:

[0008] Obtain the power factor angle of the target MMC and set the constraint range of the zero-sequence signal amplitude and phase angle;

[0009] Initialize two different working conditions of the target MMC, and determine the maximum modulation signal margin of the two different working conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle; the two different working conditions are respectively the working condition corresponding to the first apparent power and the working condition corresponding to the second apparent power;

[0010] Based on the maximum modulation signal margin under the two different operating conditions and the corresponding zero-sequence signal injection conditions, a third apparent power is iteratively obtained by the chord intercept method, and when the modulation signal margin corresponding to the third apparent power is within a preset error range, the third apparent power is determined to be the maximum operating power of the target MMC under the current power factor angle;

[0011] The power factor angle is adjusted to obtain the maximum operating power curve of the target MMC at different power factor angles, which is the overload operation limit boundary of the target MMC.

[0012] Optionally, the method further comprises:

[0013] After initializing two different working conditions of the target MMC, the maximum modulation signal margins of the two different working conditions in the absence of a zero-sequence signal are determined respectively by the power factor angle and the apparent power corresponding to the two working conditions;

[0014] Based on the two different operating conditions and the corresponding maximum modulation signal margins in the case of no zero-sequence signal, a fourth apparent power is iteratively obtained by a chord intercept method, and when the modulation signal margin corresponding to the fourth apparent power is within a preset error range, the fourth apparent power is determined to be the starting operating power of the target MMC at the current power factor angle;

[0015] The power factor angle is adjusted to obtain the initial operation power curve of the target MMC at different power factor angles, which is the overload operation starting boundary of the target MMC.

[0016] Optionally, determining the maximum modulation signal margins of the two different operating conditions under the condition of injecting the zero-sequence signal respectively through the power factor angle, the apparent power corresponding to the two operating conditions, and the constraint range of the zero-sequence signal amplitude and phase angle includes:

[0017] Construct the correlation between the power factor angle, apparent power, amplitude and phase angle of the zero-sequence signal and the modulation signal margin in the target MMC;

[0018] By adjusting the amplitude and phase angle of the zero-sequence signal within the constraint range, determining that the zero-sequence signal that maximizes the modulation signal margin is the optimal zero-sequence signal;

[0019] According to the initialized first apparent power and the initialized second apparent power, the maximum modulation signal margin under the current power factor angle is obtained through the optimal zero-sequence signal.

[0020] Optionally, the iterative formula of the chord-intercept method is:

[0021] ;

[0022] in, S n+2 is the third apparent power or the fourth apparent power, S n and S n+1 are the first apparent power and the second apparent power respectively; Mgin(S n ) and Mgin(S n+1 ) are the maximum modulation signal margins corresponding to the first apparent power and the second apparent power respectively.

[0023] Optionally, the method further comprises:

[0024] When the modulation signal margin corresponding to the third apparent power or the fourth apparent power is outside the preset range, the first apparent power and the second apparent power of the target MMC are continuously iterated by the chord intercept method until the modulation signal margin is within the preset error range.

[0025] Optionally, the constraint range expressions of the zero-sequence signal amplitude and phase angle are:

[0026] ;

[0027] The definition of the modulation signal margin Mgin of the target MMC is:

[0028] ;

[0029] in, A 3 is the amplitude of the zero-sequence signal, α 3 for A 3 corresponds to the phase angle, m rect It is the correction value of the modulation signal, obtained by the power factor angle and apparent power.

[0030] Secondly, a device for determining an MMC overload boundary is also provided, the device comprising:

[0031] An acquisition module, used to acquire the power factor angle of the target MMC and set the constraint range of the zero-sequence signal amplitude and phase angle based on the physical limitations of the target MMC;

[0032] A calculation module is used to initialize two different working conditions of the target MMC, and determine the maximum modulation signal margin of the two different working conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle; the two different working conditions are respectively the working condition corresponding to the first apparent power and the working condition corresponding to the second apparent power;

[0033] An iteration module is used to iteratively obtain a third apparent power by a chord intercept method based on the maximum modulation signal margin under the two different working conditions and the corresponding zero-sequence signal injection conditions, and determine that the third apparent power is the maximum apparent power of the target MMC injected with the optimal zero-sequence signal under the current power factor angle when the modulation signal margin corresponding to the third apparent power is within a preset error range;

[0034] The determination module is used to adjust the power factor angle to obtain the maximum apparent power curve of the target MMC injected with the optimal zero-sequence signal under different power factor angles, which is the overload operation limit boundary of the target MMC.

[0035] In addition, a computer-readable storage medium is provided, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the method for determining an MMC overload boundary is implemented.

[0036] Finally, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned method for determining an MMC overload boundary when executing the program.

[0037] The method for determining the MMC overload boundary provided by the present invention has the following beneficial effects:

[0038] First, the two apparent powers of the target MMC are initialized, and the maximum modulation signal margin of the initialized apparent power is determined. Secondly, the first apparent power and the second apparent power of the target MMC are iterated by the chord intercept method to obtain the third apparent power. In this way, the operating power of the target MMC is fitted by iterating the apparent power of the target MMC, and the corresponding zero-sequence signal is injected during the iteration process to find the maximum value of the modulation signal margin, and then the third apparent power is obtained. In this way, the third apparent power obtained by fitting the operating power of the MMC by maximizing the modulation signal margin can be determined as the maximum value of the MMC within the power range of stable operation. In this way, the present invention can clearly construct the overload operation boundary of the grid-forming MMC, accurately define the overload capacity of the MMC, enhance the responsiveness of the power system to sudden faults, and help to reasonably set the load level of the MMC during the design and operation process to ensure that it operates under safe and efficient conditions, enhance the responsiveness of the power system to sudden faults, and when a power grid failure occurs or the demand changes dramatically, the operating state of the MMC can be quickly adjusted according to the overload operation boundary to adapt to new operating conditions, avoid equipment damage or system failure caused by overload, ensure the safe and stable operation of the power system, and improve the reliability and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiment of the present invention and its design scheme, the following briefly introduces the drawings required for this embodiment. 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 creative work.

[0040] Figure 1 The present invention is a flowchart of a method for determining an MMC overload boundary according to an exemplary embodiment of the present invention.

[0041] Figure 2 A flowchart of a method for determining a maximum operating power of an MMC in overload operation is provided according to an exemplary embodiment of the present invention.

[0042] Figure 3 A flowchart of a method for determining a starting operating power of an MMC overload operation is provided according to an exemplary embodiment of the present invention.

[0043] Figure 4 A modulation signal waveform and margin data diagram for determining overload operation of an MMC provided by the present invention according to an exemplary embodiment.

[0044] Figure 5 A block diagram of a device for determining an MMC overload boundary provided according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the scope of protection of the present invention.

[0046] The present invention relates to a method for constructing an overload operation boundary of a network-type MMC. According to the power factor angle φ and apparent power S given by the MMC, the maximum modulation signal margin Magin and the zero-sequence signal amplitude OptA3 and the phase angle Optα3 under the zero-sequence signal injected under the working condition can be calculated. The apparent power is iteratively calculated until the modulation signal margin Magin is greater than 0 and less than or equal to the allowable error tol, and the overload operation limit power under the power factor angle can be obtained. By changing the power factor angle, the overload operation limit power under each power factor angle can be obtained; the MMC overload operation limit boundary curve and function are obtained by fitting the nonlinear least square method.

[0047] Similarly, according to the power factor angle φ given by the MMC, the amplitude of the zero-sequence signal is set to 0, and the apparent power is iteratively calculated until the modulation signal margin Magin is greater than 0 and less than or equal to the allowable error tol, and the overload operation starting power under the power factor angle can be obtained. By changing the power factor angle, the overload operation starting power under each power factor angle can be obtained; the MMC overload operation starting boundary curve and function are obtained by fitting the nonlinear least squares method.

[0048] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0049] First, the present invention provides a method for determining an MMC overload boundary, specifically: Figure 1 As shown, the following steps are included:

[0050] S101, obtaining the power factor angle of the target MMC, and setting the constraint range of the zero-sequence signal amplitude and phase angle.

[0051] The power factor angle refers to the phase difference between its voltage and current. This parameter is of great significance in evaluating the power transmission efficiency and operating stability of MMC. In practical applications, a dedicated power factor meter or phase meter can be used to directly measure the power factor angle of MMC.

[0052] The constraint range of the zero-sequence signal amplitude and phase angle is set based on the physical limitations of the target MMC, as shown in the following formula:

[0053] ;

[0054] S102: Initialize the target MMC working condition and determine the maximum modulation signal margin of the initialization working condition.

[0055] Initialize two different working conditions of the target MMC, and determine the maximum modulation signal margin of the two different working conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle. The two different working conditions are the working condition corresponding to the first apparent power and the working condition corresponding to the second apparent power.

[0056] Specifically, the correlation between the power factor angle, apparent power, amplitude and phase angle of the zero-sequence signal and the modulation signal margin in the target MMC is constructed; by adjusting the amplitude and phase angle of the zero-sequence signal within the constraint range, the zero-sequence signal that maximizes the modulation signal margin is determined to be the optimal zero-sequence signal; based on the initialized first apparent power and second apparent power, the maximum modulation signal margin under the current power factor angle is obtained through the optimal zero-sequence signal.

[0057] Input the power factor angle φi and set the initial value of the iteration number n to 0. According to the chord intercept method, the apparent power S is given n , S n+1 It is the initial value of iteration, i.e. S0, S1. The initial value of iteration has no effect on the final convergence result of the chord intercept method, and its value only affects the number of iterations and calculation time. You can set S0=800e6 MW and S1=1500e6 MW.

[0058] Calculate two conditions S n & φ i and S n+1 & φ i The optimal zero-sequence signal Opt A 3、 α 3|( S n , φ i ) and Opt A 3、 α 3|( S n+1 , φ i ). The definition of the optimal zero-sequence signal is the amplitude and angle of the zero-sequence signal injected under certain working conditions. The MMC modulation signal margin M gin When the value is maximum, the zero-sequence signal is determined to be the optimal zero-sequence signal.

[0059] MMC modulation signal margin M gin The definition of is as follows

[0060] ;

[0061] in, m rect is the correction value of the modulation signal, which is expressed as follows

[0062] ;

[0063] in S m,ap (t) It is the modulation signal of the upper bridge arm of phase A of the MMC, which is generated by the MMC station-level control: power controller, circulating current controller, average capacitor voltage controller, and zero-sequence signal injection controller.

[0064] Taking the A-phase upper bridge arm modulation signal as an example, its expression is as follows:

[0065] ;

[0066] in, A 0 , A 1 , A 2 and A 3 They are the amplitudes of DC, 1st, 2nd and 3rd harmonic components respectively, and the 3rd harmonic component is the zero-sequence signal; α 1 , α 2 、α 3 represents the corresponding phase angle; ω is the fundamental angular frequency, the amplitude of the third harmonic component A 3 and its corresponding phase angle α 3 Together they constitute a zero-sequence signal.

[0067] In the present invention, the power factor angle of the power controller input in the MMC station level control is φ , Apparent Power S And zero sequence signal injection controller input A 3 、α 3 As variables, the remaining parameters are considered constants, so the modulation signal margin can be M gin Seen as φ, S, A 3 、α The function of 3 is as follows:

[0068] .

[0069] S103: Based on the initialization operating condition and its corresponding maximum modulation signal margin, determine the maximum operating power of the target MMC at the current power factor angle.

[0070] Based on the maximum modulation signal margin under the two different operating conditions and their corresponding zero-sequence signal injection conditions, the third apparent power is iteratively obtained by the chord intercept method, and when the modulation signal margin corresponding to the third apparent power is within a preset error range, the third apparent power is determined to be the maximum operating power of the target MMC under the current power factor angle, that is, the limit power of the overload operation of the target MMC.

[0071] Based on the optimal zero-sequence signal obtained in the above steps, calculate the two working conditions S n &φ i , S n+1 &φ i The optimal zero-sequence signal OptA corresponding to the lower injection 3、 α3|(S n ,φ i ) and OptA 3、 α3|(S n+1 ,φ i ) when the modulation signal margin Mgin(S n )、Mgin(S n+1 ).

[0072] Specifically, the maximum operating power of the target MMC can be determined by the following formula:

[0073] .

[0074] Among them, when determining the maximum operating power, the above formula is n ) and Mgin(S n+1 ) are respectively the first apparent power modulation signal margin and the second apparent power modulation signal margin corresponding to the optimal zero-sequence signal injection.

[0075] Calculate and determine S n+2 &φ i Is the modulation signal margin within the preset error range under working conditions, that is, greater than 0 and less than or equal to the allowable error? tol , as follows:

[0076] ;

[0077] If the modulation signal margin is greater than 0 and less than or equal to the allowable error tol , the iteration ends.

[0078] When the modulation signal margin corresponding to the third apparent power or the fourth apparent power is outside the preset range, the first apparent power and the second apparent power of the target MMC are continuously iterated by the chord intercept method until the modulation signal margin is within the preset error range.

[0079] At the end of the iteration, output S n+2 is the maximum operating power, and then the power factor angle is determined φ i under the overload operation boundary of the target MMC.

[0080] S104, adjusting the power factor angle to obtain the initial operation power curve of the target MMC under different power factor angles, which is the overload operation starting boundary of the target MMC.

[0081] Since different power factor angles correspond to different maximum operating powers, the power factor angle can be adjusted to obtain a curve consisting of maximum operating powers corresponding to multiple power factor angles, which is the overload operation limit boundary of the target MMC.

[0082] In addition, after determining the overload operation limit boundary of the target MMC, it is also necessary to determine the overload operation start boundary.

[0083] Specifically, after initializing two different operating conditions of the target MMC, the maximum modulation signal margins of the two different operating conditions in the absence of a zero-sequence signal are determined respectively through the power factor angle and the apparent powers corresponding to the two operating conditions; based on the two different operating conditions and their corresponding maximum modulation signal margins in the absence of a zero-sequence signal, a fourth apparent power is iteratively obtained through the chord intercept method, and when the modulation signal margin corresponding to the fourth apparent power is within a preset error range, the fourth apparent power is determined to be the starting operating power of the target MMC at the current power factor angle; the power factor angle is adjusted to obtain the starting operating power curve of the target MMC at different power factor angles, which is the starting boundary of the overload operation of the target MMC.

[0084] The difference between the process of determining the overload operation starting boundary and the process of determining the overload operation limit boundary is that no zero-sequence signal is injected when determining the maximum modulation signal margin corresponding to the operating condition.

[0085] The formula for determining the starting operating power of the target MMC overload operation is:

[0086] .

[0087] In the case of determining the starting operating power, the above formula is n ) and Mgin(S n+1) are respectively the maximum modulation signal margin corresponding to the first apparent power without zero-sequence signal injection and the maximum modulation signal margin corresponding to the second apparent power.

[0088] At the end of the iteration, the maximum operating power or the starting operating power is output, thereby determining the power factor angle φ i The steps of the method for determining the maximum operating power and the starting operating power of the target MMC under overload operation are as follows: Figure 2 and Figure 3 shown.

[0089] The different overload operation boundaries of the target MMC are fitted by the nonlinear least square method, and the overload operation boundary curve and function of the target MMC are obtained.

[0090] For example, the obtained MMC operation area is processed, and the elliptic function equation shown in the following formula is selected to obtain its specific boundary fitting function model through nonlinear least squares fitting:

[0091] ;

[0092] Where (xc, yc) is the center of the ellipse, a is the major semi-axis of the ellipse, and b is the minor semi-axis of the ellipse.

[0093] Using the above method, first, the two apparent powers of the target MMC are initialized, and the maximum modulation signal margin of the initialized apparent power is determined. Secondly, the first apparent power and the second apparent power of the target MMC are iterated by the chord intercept method to obtain the third apparent power. In this way, the operating power of the target MMC is fitted by iterating the apparent power of the target MMC, and the corresponding zero-sequence signal is injected during the iteration process to find the maximum value of the modulation signal margin, and then the third apparent power is obtained. In this way, the third apparent power obtained by fitting the operating power of the MMC by maximizing the modulation signal margin can be determined as the maximum value of the MMC within the power range of stable operation. In this way, the present invention can clearly construct the overload operation boundary of the grid-forming MMC, accurately define the overload capacity of the MMC, enhance the responsiveness of the power system to sudden faults, and help to reasonably set the load level of the MMC during the design and operation process to ensure that it operates under safe and efficient conditions, enhance the responsiveness of the power system to sudden faults, and when a power grid failure occurs or the demand changes dramatically, the operating state of the MMC can be quickly adjusted according to the overload operation boundary to adapt to new operating conditions, avoid equipment damage or system failure caused by overload, ensure the safe and stable operation of the power system, and improve the reliability and stability of the system.

[0094] In order to verify the method for determining the overload boundary of the MMC proposed in the present invention, verification is performed in conjunction with an embodiment below. The main circuit parameters of the MMC in the embodiment are shown in Table 1.

[0095] Table 1 MMC main circuit parameters

[0096]

[0097] In order to obtain a complete grid-type MMC overload operation boundary, the input power factor angle φ 0 =0, iterative calculation error tol= 0.01, initial value of iteration S 0 =800MW 、S 1 =1500MW. Calculated Opt A 3|( S 0 , φ 0 )=0.0718, Opt α 3|( S 0 , φ 0 )=3.7429, M gin (S 0 )= 0.1148; Opt A 3|( S 1 , φ 0 )=0.0730, Opt α 3|( S 1 , φ 0 )=4.3388, M gin (S 1 )= 0.0938. Iterative calculation is done by the following formula: S 2 =4626.7MW:

[0098] ;

[0099] At this time, Opt A 3|( S 2 , φ 0 )=0.1578, Opt α 3|(S 2 , φ 0 )=6.0034, M gin (S 2 )= -0.1345; M gin (S 2 ) Less than 0, does not satisfy the judgment formula .

[0100] So through the formula Perform iterative calculations and get S 3 =2784.6 MW, at this time Opt A 3|( S 3 , φ 0 ) = 0.1066, Opt α 3|( S 3 , φ 0 ) = 5.2581, M gin (S 3 )= 0.0302; M gin (S 3 ) Greater than the allowable error tol , does not satisfy the judgment formula , continue iterating until the modulation signal margin satisfies the formula The modeling procedure in the above steps calculates S max,φ0 =3059 MW, Opt A 3= 0.1133, Opt α 3 = 5.4004, the modulation signal margin at this time M gin = 0.010; Under this working condition and zero-sequence signal injection, the modulation signal margin meets the iteration end condition, and the power factor angle is obtained. φ 0 =0, the MMC overload operation limit power injected with zero sequence signal S max,φ0 =3059 MW. The modulation signal waveform and margin under the power factor angle and overload operation limit power are obtained through simulation as follows: Figure 4As shown. Figure 4 The simulation results show that the modulation signal margin is M gin = 0.0109, which has a small error compared with the result calculated by the program, proving the accuracy of the result calculated by the program.

[0101] Similarly, the iterative power factor angle φ 1 =π / 24, repeat the above steps to get S max,φ1 =2638 MW; iterate until the power factor angle φ i = 2π, we get φ i ∈[0, 2π], the overload operation limit power of the zero-sequence signal injected at each power factor angle is the overload operation limit boundary of the grid-type MMC.

[0102] Set the zero-sequence signal amplitude and phase angle to 0, and repeat the above steps to obtain an MMC overload operation boundary without injecting zero-sequence signal, that is, the grid-type MMC overload operation starting boundary. The MMC overload operation boundary data under various power factor angles are shown in Table 2.

[0103] Table 2 Overload operation boundary of meshed MMC

[0104]

[0105] According to the calculated data, a scatter plot of the operating domain data is drawn, and the nonlinear implicit function elliptic curve is selected and fitted by the nonlinear least square method. The two mesh-type MMC overload operating areas and the corresponding boundary fitting functions are shown in Figure 2. Figure 4 As shown. Among them, the overload operation starting boundary fitting curve is: , overload operation limit boundary fitting curve The corresponding residual sum of squares RSS of the fitting function are 1.80e -31 and 5.34e -28 , infinitely close to 0, proving that the deviation between the fitting function and the actual data is very small, and it can well describe the trend and distribution of the data.

[0106] So far, the overload operation starting boundary and overload operation limit boundary of MMC are obtained based on the main circuit parameters of MMC, the overload operation boundary of meshed MMC is constructed, and the fitting functions of the overload operation boundary are given respectively by the least squares method.

[0107] Secondly, the present invention also provides a device for determining the MMC overload boundary, such as Figure 5 As shown, including:

[0108] The acquisition module 501 is used to acquire the power factor angle of the target MMC and set the constraint range of the zero-sequence signal amplitude and phase angle based on the physical limitations of the target MMC.

[0109] The calculation module 502 is used to initialize two different operating conditions of the target MMC, and determine the maximum modulation signal margin of the two different operating conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two operating conditions, and the constraint range of the zero-sequence signal amplitude and phase angle; the two different operating conditions are the operating condition corresponding to the first apparent power and the operating condition corresponding to the second apparent power.

[0110] The iteration module 503 is used to iteratively obtain the third apparent power through the chord intercept method based on the maximum modulation signal margin under the two different operating conditions and the corresponding zero-sequence signal injection conditions, and determine the third apparent power as the maximum apparent power of the target MMC when the optimal zero-sequence signal is injected at the current power factor angle when the modulation signal margin corresponding to the third apparent power is within a preset error range.

[0111] The determination module 504 is used to adjust the power factor angle to obtain the maximum apparent power curve of the target MMC when injecting the optimal zero-sequence signal at different power factor angles, which is the overload operation limit boundary of the target MMC.

[0112] Using the above-mentioned device, firstly, the two apparent powers of the target MMC are initialized, and the maximum modulation signal margin of the initialized apparent power is determined. Secondly, the first apparent power and the second apparent power of the target MMC are iterated by the chord intercept method to obtain the third apparent power. In this way, the operating power of the target MMC is fitted by iterating the apparent power of the target MMC, and the corresponding zero-sequence signal is injected during the iteration process to find the maximum value of the modulation signal margin, and then the third apparent power is obtained. In this way, the third apparent power obtained by fitting the operating power of the MMC by maximizing the modulation signal margin can be determined as the maximum value of the MMC within the power range of stable operation. In this way, the present invention can clearly construct the overload operation boundary of the grid-forming MMC, accurately define the overload capacity of the MMC, enhance the responsiveness of the power system to sudden faults, and help to reasonably set the load level of the MMC during the design and operation process to ensure that it operates under safe and efficient conditions, enhance the responsiveness of the power system to sudden faults, and when a power grid failure occurs or the demand changes dramatically, the operating state of the MMC can be quickly adjusted according to the overload operation boundary to adapt to new operating conditions, avoid equipment damage or system failure caused by overload, ensure the safe and stable operation of the power system, and improve the reliability and stability of the system.

[0113] The present invention also provides a computer-readable storage medium, which stores a computer program, which can be used to execute the above Figure 1Steps of a method for determining an MMC overload boundary are provided.

[0114] The present invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory. Of course, it may also include hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to achieve the above Figure 1 Steps of a method for determining an MMC overload boundary are provided.

[0115] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0116] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as a combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0117] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0118] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0119] It should be noted that the above specific implementation method can enable those skilled in the art to understand the invention more comprehensively, but does not limit the invention in any way. Therefore, although the present invention has been described in detail in this specification, those skilled in the art should understand that the invention can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the invention are included in the protection scope of the patent for the invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for determining an MMC overload boundary, characterized in that: The method comprises: Obtain the power factor angle of the target MMC and set the constraint range of the zero-sequence signal amplitude and phase angle; Initialize two different working conditions of the target MMC, and determine the maximum modulation signal margin of the two different working conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle; the two different working conditions are respectively the working condition corresponding to the first apparent power and the working condition corresponding to the second apparent power; Based on the maximum modulation signal margin under the two different operating conditions and the corresponding zero-sequence signal injection conditions, a third apparent power is iteratively obtained by the chord intercept method, and when the modulation signal margin corresponding to the third apparent power is within a preset error range, the third apparent power is determined to be the maximum operating power of the target MMC under the current power factor angle; The power factor angle is adjusted to obtain the maximum operating power curve of the target MMC at different power factor angles, which is the overload operation limit boundary of the target MMC; By using the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle, the maximum modulation signal margin under the condition of injecting the zero-sequence signal under the two different working conditions is determined respectively, including: Construct the correlation between the power factor angle, apparent power, amplitude and phase angle of the zero-sequence signal and the modulation signal margin in the target MMC; By adjusting the amplitude and phase angle of the zero-sequence signal within the constraint range, determining that the zero-sequence signal that maximizes the modulation signal margin is the optimal zero-sequence signal; According to the initialized first apparent power and the initialized second apparent power, the maximum modulation signal margin under the current power factor angle is obtained through the optimal zero-sequence signal.

2. A method for determining an MMC overload boundary according to claim 1, characterized in that: The method further comprises: After initializing two different working conditions of the target MMC, the maximum modulation signal margins of the two different working conditions in the absence of a zero-sequence signal are determined respectively by the power factor angle and the apparent power corresponding to the two working conditions; Based on the two different operating conditions and the corresponding maximum modulation signal margins in the case of no zero-sequence signal, a fourth apparent power is iteratively obtained by a chord intercept method, and when the modulation signal margin corresponding to the fourth apparent power is within a preset error range, the fourth apparent power is determined to be the starting operating power of the target MMC at the current power factor angle; The power factor angle is adjusted to obtain the initial operation power curve of the target MMC at different power factor angles, which is the overload operation starting boundary of the target MMC.

3. A method for determining an MMC overload boundary according to claim 1 or 2, characterized in that: The iterative formula of the chord-intercept method is: Among them, S n+2 is the third apparent power or the fourth apparent power, S n and S n+1 are the first apparent power and the second apparent power respectively; M gin (S n ) and M gin (S n+1 ) are the maximum modulation signal margins corresponding to the first apparent power and the second apparent power respectively.

4. A method for determining an MMC overload boundary according to claim 3, characterized in that: The method further comprises: When the modulation signal margin corresponding to the third apparent power or the fourth apparent power is outside the preset range, the first apparent power and the second apparent power of the target MMC are continuously iterated by the chord intercept method until the modulation signal margin is within the preset error range.

5. A method for determining an MMC overload boundary according to claim 1, characterized in that: The constraint range expression of the zero-sequence signal amplitude and phase angle is: Modulation signal margin M of target MMC gin The definition of: Among them, A3 is the amplitude of the zero-sequence signal, α3 is the phase angle corresponding to A3, and m rect It is the correction value of the modulation signal, obtained by the power factor angle and apparent power.

6. A device for determining an MMC overload boundary, characterized in that: The device comprises: An acquisition module is used to obtain the power factor angle of the target MMC and set the constraint range of the zero-sequence signal amplitude and phase angle; A calculation module is used to initialize two different working conditions of the target MMC, and determine the maximum modulation signal margin of the two different working conditions when the zero-sequence signal is injected through the power factor angle, the apparent power corresponding to the two working conditions, and the constraint range of the zero-sequence signal amplitude and phase angle; the two different working conditions are respectively the working condition corresponding to the first apparent power and the working condition corresponding to the second apparent power; An iteration module is used to iteratively obtain a third apparent power by a chord intercept method based on the maximum modulation signal margin under the two different working conditions and the corresponding zero-sequence signal injection conditions, and determine that the third apparent power is the maximum apparent power of the target MMC injected with the optimal zero-sequence signal under the current power factor angle when the modulation signal margin corresponding to the third apparent power is within a preset error range; A determination module is used to adjust the power factor angle to obtain a maximum apparent power curve of the target MMC injected with the optimal zero-sequence signal under different power factor angles, which is the overload operation limit boundary of the target MMC; The calculation module is also used to construct the correlation between the power factor angle, apparent power, amplitude and phase angle of the zero-sequence signal and the modulation signal margin in the target MMC; by adjusting the amplitude and phase angle of the zero-sequence signal within the constraint range, the zero-sequence signal that maximizes the modulation signal margin is determined to be the optimal zero-sequence signal; and according to the initialized first apparent power and the second apparent power, the maximum modulation signal margin under the current power factor angle is obtained through the optimal zero-sequence signal.

7. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

8. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 5 when executing the program.

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