Grid-connected system negative sequence phase voltage phase determination method, controller and grid-connected system

Abstract

The application provides a negative sequence phase voltage phase determination method, a controller and a grid-connected system. The method comprises the following steps: obtaining a phase difference between a current positive sequence line voltage and a negative sequence line voltage of the grid-connected system; determining a phase difference between a current positive sequence phase voltage and a negative sequence phase voltage of the grid-connected system based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage; obtaining a current positive sequence phase voltage phase of the grid-connected system; and determining a current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage. The current negative sequence phase voltage phase of the grid-connected system can be calculated through the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system and the current positive sequence phase voltage phase of the grid-connected system, and then the grid-connected system can output negative sequence reactive power according to the current negative sequence phase voltage phase of the grid-connected system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of grid-connected technology, and in particular to a negative sequence phase voltage phase determination method for a grid-connected system, a controller and the grid-connected system. BACKGROUND

[0002] Unbalanced ride-through refers to keeping the grid-connected system running without being disconnected within a certain time period when the three-phase is unbalanced. In some grid-connected standards, when unbalanced ride-through occurs, the grid-connected system is required to output both positive sequence reactive power and negative sequence reactive power.

[0003] Currently, when unbalanced ride-through testing is performed, the simulated is usually the unbalanced ride-through of phase voltage. When simulating the unbalanced ride-through of phase voltage, the phase of the negative sequence phase voltage needs to be obtained in order to control the grid-connected system to output negative sequence reactive power. However, for a three-phase three-wire grid-connected system, i.e., a three-phase grid-connected system without a neutral line, only line voltage sampling can be performed, and the phase of the negative sequence phase voltage cannot be directly phase-locked, resulting in the inability to control the grid-connected system to output negative sequence reactive power. SUMMARY

[0004] Embodiments of the present application provide a negative sequence phase voltage phase determination method for a grid-connected system, a controller and the grid-connected system, to solve the problem that the phase of the negative sequence phase voltage cannot be directly phase-locked when the three-phase grid-connected system without a neutral line is in unbalanced ride-through, resulting in the inability to control the grid-connected system to output negative sequence reactive power.

[0005] In a first aspect, embodiments of the present application provide a negative sequence phase voltage phase determination method for a grid-connected system, comprising:

[0006] obtaining the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system;

[0007] determining the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage;

[0008] obtaining the current positive sequence phase voltage phase of the grid-connected system;

[0009] determining the current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage.

[0010] In a possible implementation, the calculation formula of the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage is:

[0011] θ1=θ p -θ2

[0012] wherein θ1 is the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage; θ pθ1 is a first preset angle value; θ2 is a phase difference between the current positive sequence line voltage and the negative sequence line voltage.

[0013] In a possible implementation, the method for determining the first preset angle value comprises:

[0014] constructing a relationship between a phase difference between the positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system and a phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system;

[0015] for each angle value under each three-phase unbalanced operating condition, obtaining an experimental phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system under the three-phase unbalanced operating condition, substituting the angle value and the experimental phase difference into the relationship to obtain an experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, and controlling the grid-connected system based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, obtaining an output negative sequence reactive power of the grid-connected system, and determining whether the output negative sequence reactive power of the grid-connected system meets a preset requirement; the angle value is within a preset angle range;

[0016] the angle value that makes the output negative sequence reactive power of the grid-connected system meet the preset requirement under all three-phase unbalanced operating conditions is taken as the first preset angle value.

[0017] In a possible implementation, after determining the current negative sequence phase voltage phase of the grid-connected system, the method for determining the negative sequence phase voltage phase of the grid-connected system further comprises:

[0018] obtaining a first negative sequence active phase current given value and a first negative sequence reactive phase current given value of the grid-connected system;

[0019] performing park inverse transformation based on the first negative sequence active phase current given value, the first negative sequence reactive phase current given value, and the current negative sequence phase voltage phase to obtain an α-axis phase current component given value and a β-axis phase current component given value;

[0020] performing park transformation based on the α-axis phase current component given value, the β-axis phase current component given value, and the current positive sequence phase voltage phase to obtain a second negative sequence active phase current given value and a second negative sequence reactive phase current given value;

[0021] obtaining a positive sequence active phase current given value and a positive sequence reactive phase current given value of the grid-connected system;

[0022] summing the positive sequence active phase current given value and the second negative sequence active phase current given value to obtain an active phase current given value, and summing the positive sequence reactive phase current given value and the second negative sequence reactive phase current given value to obtain a reactive phase current given value;

[0023] controlling the grid-connected system based on the active phase current given value and the reactive phase current given value.

[0024] In a possible implementation, the first negative sequence reactive phase current given value of the grid-connected system is obtained, including:

[0025] The current negative sequence phase voltage of the grid-connected system and the negative sequence variation degree value of the negative sequence phase voltage under the three-phase balanced working condition are obtained;

[0026] The product of the negative sequence variation degree value, the preset negative sequence reactive coefficient and the rated current of the grid-connected system is subjected to amplitude limiting processing to obtain the first negative sequence reactive phase current given value.

[0027] In a possible implementation, the first positive sequence reactive phase current given value of the grid-connected system is obtained, including:

[0028] The current positive sequence phase voltage of the grid-connected system and the positive sequence variation degree value of the positive sequence phase voltage under the three-phase balanced working condition are obtained;

[0029] The product of the positive sequence variation degree value, the preset positive sequence reactive coefficient and the rated current of the grid-connected system is subjected to amplitude limiting processing to obtain the positive sequence reactive phase current given value.

[0030] In a possible implementation, the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system is obtained, including:

[0031] The current negative sequence active phase voltage and the current negative sequence reactive phase voltage of the grid-connected system are obtained;

[0032] The angle value of the tangent value of the negative sequence phase voltage ratio is taken as the first angle value, and the negative sequence phase voltage ratio is the ratio of the current negative sequence reactive phase voltage to the current negative sequence active phase voltage;

[0033] If the current negative sequence active phase voltage is less than a preset threshold value, the first angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system;

[0034] If the current negative sequence active phase voltage is not less than the preset threshold value, the sum of the first angle value and a second preset angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0035] In a second aspect, an embodiment of the present application provides a controller, including a memory and a processor, the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the negative sequence phase voltage phase determination method of the grid-connected system as described in the first aspect or any possible implementation of the first aspect.

[0036] In a third aspect, an embodiment of the present application provides a grid-connected system, including the controller as described in the second aspect.

[0037] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium storing a computer program, the computer program, when executed by a processor, implements steps of the method for determining a phase of a negative sequence phase voltage of a grid-connected system according to the first aspect or any possible implementation of the first aspect.

[0038] The embodiment of the present application provides a method for determining a phase of a negative sequence phase voltage of a grid-connected system, a controller and the grid-connected system. The method determines a phase difference between a current positive sequence phase voltage and a negative sequence phase voltage of the grid-connected system based on a phase difference between a current positive sequence line voltage and a negative sequence line voltage of the grid-connected system, and determines the current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage. Therefore, the current negative sequence phase voltage phase of the grid-connected system can be calculated based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system and the current positive sequence phase voltage phase of the grid-connected system, and the grid-connected system can output negative sequence reactive power according to the current negative sequence phase voltage phase of the grid-connected system. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0040] Figure 1 FIG. 1 is a flowchart of the method for determining a phase of a negative sequence phase voltage of a grid-connected system provided by the embodiment of the present application;

[0041] Figure 2 FIG. 2 is a structural diagram of the device for determining a phase of a negative sequence phase voltage of a grid-connected system provided by the embodiment of the present application;

[0042] Figure 3 FIG. 3 is a schematic diagram of the controller provided by the embodiment of the present application. DETAILED DESCRIPTION

[0043] In the following description, specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art will understand that the present application can be practiced without these specific details. In other instances, well-known methods, structures, circuits, and processes have not been described in detail in order to avoid obscuring the present application.

[0044] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be described with reference to the drawings by specific embodiments.

[0045] Referring to Figure 1 It shows an implementation flowchart of the negative sequence phase voltage phase determination method of the grid-connected system provided by the embodiment of the application. The execution subject of the negative sequence phase voltage phase determination method of the grid-connected system can be a controller.

[0046] The negative sequence phase voltage phase determination method of the grid-connected system comprises:

[0047] In S101, the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system is obtained.

[0048] For the three-phase grid-connected system without neutral line, the current negative sequence phase voltage phase cannot be directly phase-locked, but the current positive sequence phase voltage phase can be obtained, and the current negative sequence phase voltage phase can be obtained through the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage. The phase difference between the current positive sequence line voltage and the negative sequence line voltage is related to the phase difference between the current positive sequence line voltage and the negative sequence line voltage, so the embodiment first obtains the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0049] The phase difference between the current positive sequence line voltage and the negative sequence line voltage is the difference between the phase of the current positive sequence line voltage and the phase of the current negative sequence line voltage.

[0050] In some embodiments, the obtaining of the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system comprises:

[0051] The current negative sequence active phase voltage and the current negative sequence reactive phase voltage of the grid-connected system are obtained.

[0052] The angle value of the tangent value of the negative sequence phase voltage ratio is taken as the first angle value, and the negative sequence phase voltage ratio is the ratio of the current negative sequence reactive phase voltage to the current negative sequence active phase voltage.

[0053] If the current negative sequence active phase voltage is less than the preset threshold, the first angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0054] If the current negative sequence active phase voltage is not less than the preset threshold, the sum of the first angle value and the second preset angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0055] The embodiment does not make specific restrictions on the means for obtaining the current negative sequence active phase voltage and the current negative sequence reactive phase voltage of the grid-connected system, and any existing means that can be implemented can be used.

[0056] wherein θ3 is a first angle value, UqNeg is a current negative sequence reactive phase voltage, and UdNeg is a current negative sequence active phase voltage, is a negative sequence phase voltage ratio.

[0057] wherein the preset threshold value can be set according to actual requirements. Exemplarily, the preset threshold value can be 0 or a value close to 0. The second preset angle value can be determined according to actual application. Exemplarily, the second preset angle value can be 180 degrees.

[0058] In S102, a phase difference between a current positive sequence phase voltage and a negative sequence phase voltage of the grid-connected system is determined based on a phase difference between a current positive sequence line voltage and a negative sequence line voltage.

[0059] The phase difference between the current positive sequence phase voltage and the negative sequence phase voltage is a difference value between a phase of the current positive sequence phase voltage and a phase of the current negative sequence phase voltage.

[0060] The inventors have found that there is a certain correlation between the phase difference between the positive sequence line voltage and the negative sequence line voltage and the phase difference between the positive sequence phase voltage and the negative sequence phase voltage. Therefore, the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system can be calculated through the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0061] In some embodiments, a calculation formula of the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage is:

[0062] θ1=θ p -θ2

[0063] wherein θ1 is the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage; θ p is a first preset angle value; and θ2 is the phase difference between the current positive sequence line voltage and the negative sequence line voltage.

[0064] In some embodiments, a determination method of the first preset angle value comprises:

[0065] constructing a relationship between the phase difference between the positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system and the phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system;

[0066] For each angle value under each three-phase unbalanced working condition, an experimental phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system under the three-phase unbalanced working condition is obtained, the angle value and the experimental phase difference are substituted into the relationship to obtain an experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage corresponding to the angle value, and the grid-connected system is controlled based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, so as to obtain the output negative sequence reactive power of the grid-connected system and determine whether the output negative sequence reactive power of the grid-connected system meets a preset requirement; the angle value is within a preset angle range.

[0067] The angle value that makes the output negative sequence reactive power of the grid-connected system meet the preset requirement under all three-phase unbalanced working conditions is taken as a first preset angle value.

[0068] The relationship between the phase difference between the positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system and the phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system is shown in the above formula.

[0069] The three-phase unbalanced working conditions of the grid-connected system can include six working conditions, which are as follows: the voltages of phases A and B are normal, and the voltage of phase C is higher than the voltages of phases A and B; the voltages of phases A and B are normal, and the voltage of phase C is lower than the voltages of phases A and B; the voltages of phases A and C are normal, and the voltage of phase B is higher than the voltages of phases A and C; the voltages of phases A and C are normal, and the voltage of phase B is lower than the voltages of phases A and C; the voltages of phases C and B are normal, and the voltage of phase A is higher than the voltages of phases C and B; and the voltages of phases C and B are normal, and the voltage of phase A is lower than the voltages of phases C and B.

[0070] In determining the first preset angle value, for each three-phase unbalanced working condition, whether each angle value within the preset angle range can make the output negative sequence reactive power of the grid-connected system meet the preset requirement is tested, and finally, the angle value that makes the output negative sequence reactive power of the grid-connected system meet the preset requirement under all three-phase unbalanced working conditions is taken as the first preset angle value.

[0071] Controlling the grid-connected system based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage can include obtaining the experimental phase of the negative sequence phase voltage based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage and the experimental phase of the positive sequence phase voltage, and controlling the grid-connected system based on the experimental phase of the negative sequence phase voltage. Controlling the grid-connected system based on the experimental phase of the negative sequence phase voltage can refer to a subsequent process of controlling the grid-connected system based on a current negative sequence phase voltage phase of the grid-connected system, and details are not described herein.

[0072] The preset angle range can be determined according to actual requirements or related tests, for example, can be 0-360 degrees. The preset requirement is a requirement to be met by the output negative sequence reactive power of the grid-connected system, which can be determined according to actual use requirements.

[0073] It should be noted that in the experiment of determining the first preset angle value, the related parameters of the grid-connected system are added with "experiment" to distinguish from the related parameters of the grid-connected system which is not in the experiment, but the two related parameter values represent the same meaning.

[0074] In some possible implementation manners, the first preset angle value can be 60 degrees.

[0075] In S103, the current positive sequence phase voltage phase of the grid-connected system is obtained.

[0076] For the three-phase grid-connected system without neutral line, the current negative sequence phase voltage phase cannot be directly phase-locked, but the current positive sequence phase voltage phase can be obtained.

[0077] In S104, the current negative sequence phase voltage phase of the grid-connected system is determined according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage.

[0078] In this embodiment, after the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage and the current positive sequence phase voltage phase are determined, the current negative sequence phase voltage phase of the grid-connected system can be obtained by calculation.

[0079] This embodiment determines the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system, and determines the current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage, so that the current negative sequence phase voltage phase of the grid-connected system can be calculated through the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system and the current positive sequence phase voltage phase of the grid-connected system, and then the negative sequence reactive power output by the grid-connected system can be controlled according to the current negative sequence phase voltage phase of the grid-connected system.

[0080] In some embodiments, after S104, the negative sequence phase voltage phase determination method of the grid-connected system further includes:

[0081] obtaining a first negative sequence active phase current given value and a first negative sequence reactive phase current given value of the grid-connected system;

[0082] performing park inverse transformation based on the first negative sequence active phase current given value, the first negative sequence reactive phase current given value and the current negative sequence phase voltage phase to obtain an alpha-axis phase current component given value and a beta-axis phase current component given value;

[0083] The park transformation is performed based on the alpha-axis phase current component given value, the beta-axis phase current component given value and the current positive sequence phase voltage phase to obtain a second negative sequence active phase current given value and a second negative sequence reactive phase current given value;

[0084] The positive sequence active phase current given value and the positive sequence reactive phase current given value of the grid-connected system are obtained;

[0085] The positive sequence active phase current given value and the second negative sequence active phase current given value are summed to obtain an active phase current given value, and the positive sequence reactive phase current given value and the second negative sequence reactive phase current given value are summed to obtain a reactive phase current given value;

[0086] The grid-connected system is controlled based on the active phase current given value and the reactive phase current given value.

[0087] The embodiment obtains the related parameters (the first negative sequence active phase current given value, the first negative sequence reactive phase current given value and the current negative sequence phase voltage phase) of the negative sequence coordinate axis, performs some transformations to obtain the corresponding parameters (the active phase current given value and the reactive phase current given value) of the positive sequence coordinate axis, and then controls the grid-connected system in reverse to make the grid-connected system output the required positive sequence reactive power and the required negative sequence reactive power.

[0088] The park inverse transformation (ipark transformation) is performed on the first negative sequence active phase current given value, the first negative sequence reactive phase current given value and the current negative sequence phase voltage phase to obtain the alpha-axis phase current component given value and the beta-axis phase current component given value. The park transformation is performed on the alpha-axis phase current component given value, the beta-axis phase current component given value and the current positive sequence phase voltage phase to obtain the second negative sequence active phase current given value and the second negative sequence reactive phase current given value.

[0089] The active phase current given value is obtained by summing the positive sequence active phase current given value and the second negative sequence active phase current given value, and the reactive phase current given value is obtained by summing the positive sequence reactive phase current given value and the second negative sequence reactive phase current given value. The grid-connected system is controlled based on the active phase current given value and the reactive phase current given value, so that the active phase current actual value is equal to the active phase current given value, the reactive phase current actual value is equal to the reactive phase current given value, and the positive sequence active power and the negative sequence reactive power of the grid-connected system meet the requirements.

[0090] The embodiment does not make specific limitation on the obtaining means of the first negative sequence active phase current given value, the first negative sequence reactive phase current given value, the positive sequence active phase current given value and the positive sequence reactive phase current given value, and any achievable means can be used.

[0091] In some possible implementation manners, the first negative sequence active phase current given value can be 0.

[0092] In some possible implementation manners, the positive sequence active phase current given value of the grid-connected system can be the rated current of the grid-connected system multiplied by a preset percentage. The preset percentage can be determined according to actual needs, for example, can be 2%, 3%, and the like.

[0093] In some embodiments, the first negative sequence reactive phase current given value of the grid-connected system is obtained by:

[0094] obtaining a negative sequence variation degree value of a current negative sequence phase voltage of the grid-connected system and a negative sequence phase voltage in a three-phase balanced working condition;

[0095] performing amplitude limiting processing on a product of the negative sequence variation degree value, the preset negative sequence reactive coefficient and the rated current of the grid-connected system, to obtain the first negative sequence reactive phase current given value.

[0096] The preset negative sequence reactive coefficient can be understood as a proportion or coefficient of the negative sequence reactive output of the grid-connected system, and can be a value between 0 and 2. For example, if the preset negative sequence reactive coefficient is 0, it means that no negative sequence reactive power is output, if the preset negative sequence reactive coefficient is 1, it means that 1 times of negative sequence reactive power is output, if the preset negative sequence reactive coefficient is 2, it means that 2 times of negative sequence reactive power is output, and the like.

[0097] The current negative sequence phase voltage of the grid-connected system is The current negative sequence phase voltage and the negative sequence phase voltage in the three-phase balanced working condition are normalized respectively to obtain the normalized current negative sequence phase voltage and the normalized negative sequence phase voltage in the three-phase balanced working condition. The difference between the normalized negative sequence phase voltage in the three-phase balanced working condition and the normalized current negative sequence phase voltage is taken as the negative sequence variation degree value. The normalized negative sequence phase voltage in the three-phase balanced working condition is 0, and therefore the difference between 0 and the normalized current negative sequence phase voltage is the negative sequence variation degree value.

[0098] The negative sequence variation degree value can be understood as the variation of the negative sequence phase voltage of the grid-connected system in the current working condition and the negative sequence phase voltage in the three-phase balanced working condition. The three-phase balanced working condition refers to that the voltages of the A phase, the B phase and the C phase of the grid-connected system are balanced, and there is no difference or the difference is small.

[0099] The product of the negative sequence variation degree value, the preset negative sequence reactive coefficient and the rated current of the grid-connected system is calculated, and the first negative sequence reactive phase current given value is obtained by performing amplitude limiting processing on the product. The purpose of the amplitude limiting processing is to limit the power of the grid-connected system within the rated power. The specific implementation form of the amplitude limiting processing is not limited in the embodiment, and any implementable manner can be used.

[0100] In some embodiments, the above-mentioned obtaining the given value of the positive-sequence reactive phase current of the grid-connected system comprises:

[0101] obtaining a positive-sequence variation degree value of the current positive-sequence phase voltage of the grid-connected system and the positive-sequence phase voltage under the three-phase balanced working condition;

[0102] amplifying the product of the positive-sequence variation degree value, the preset positive-sequence reactive coefficient and the rated current of the grid-connected system to obtain the given value of the positive-sequence reactive phase current.

[0103] The preset positive-sequence reactive coefficient can be understood as the proportion or coefficient of the output positive-sequence reactive of the grid-connected system, which can be understood in the same way as the above-mentioned preset negative-sequence reactive coefficient, and will not be described here.

[0104] The current positive-sequence phase voltage of the grid-connected system is UdPos is the current positive-sequence reactive phase voltage of the grid-connected system, and UdPos is the current positive-sequence active phase voltage of the grid-connected system. When phase locking, UdPos=0, so the current positive-sequence phase voltage of the grid-connected system is equal to UdPos. By normalizing the current positive-sequence phase voltage and the positive-sequence phase voltage under the three-phase balanced working condition, the normalized current positive-sequence phase voltage and the normalized positive-sequence phase voltage under the three-phase balanced working condition are obtained. The difference between the normalized current positive-sequence phase voltage and the normalized positive-sequence phase voltage under the three-phase balanced working condition is taken as the positive-sequence variation degree value. The normalized positive-sequence phase voltage under the three-phase balanced working condition is 1.0, so the difference between the normalized current positive-sequence phase voltage and 1.0 is the positive-sequence variation degree value.

[0105] The positive-sequence variation degree value can be understood as the variation of the positive-sequence phase voltage of the grid-connected system under the current working condition and the positive-sequence phase voltage under the three-phase balanced working condition. Since UqPos=0, it can be understood as the variation of the positive-sequence active phase voltage of the grid-connected system under the current working condition and the positive-sequence active phase voltage under the three-phase balanced working condition, i.e. the drop depth of the positive-sequence active component.

[0106] The product of the positive-sequence variation degree value, the preset positive-sequence reactive coefficient and the rated current of the grid-connected system is calculated, and the given value of the positive-sequence reactive phase current is obtained by amplifying the product. The purpose of the amplification is to limit the power of the grid-connected system within the rated power. The specific implementation form of the amplification is not limited in this embodiment, and any implementable way can be used.

[0107] It should be understood that the size of the serial number of each step in the above-mentioned embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0108] The following is an embodiment of the device of the application, for details not described in detail, can refer to the corresponding method embodiment described above.

[0109] Figure 2 The structure diagram of the negative sequence phase voltage phase determination device of the grid-connected system provided by the embodiment of the application is shown, for the convenience of description, only the part related to the embodiment of the application is shown, and the details are as follows:

[0110] As Figure 2 shown, the negative sequence phase voltage phase determination device 30 of the grid-connected system can include: a first acquisition module 31, a phase voltage phase difference determination module 32, a second acquisition module 33, and a negative sequence phase voltage phase determination module 34.

[0111] The first acquisition module 31 is configured to acquire the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0112] The phase voltage phase difference determination module 32 is configured to determine the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage.

[0113] The second acquisition module 33 is configured to acquire the current positive sequence phase voltage phase of the grid-connected system.

[0114] The negative sequence phase voltage phase determination module 34 is configured to determine the current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage.

[0115] In a possible implementation, in the phase voltage phase difference determination module 32, the calculation formula of the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage is:

[0116] θ1=θ p -θ2

[0117] Wherein, θ1 is the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage; θ p is a first preset angle value; and θ2 is the phase difference between the current positive sequence line voltage and the negative sequence line voltage.

[0118] In a possible implementation, in the phase voltage phase difference determination module 32, the determination method of the first preset angle value includes:

[0119] Constructing the relationship between the phase difference between the positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system and the phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0120] For each angle value under each three-phase unbalanced working condition, an experimental phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system under the three-phase unbalanced working condition is obtained, the angle value and the experimental phase difference are substituted into the relationship to obtain an experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage corresponding to the angle value, and the grid-connected system is controlled based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, to obtain an output negative sequence reactive power of the grid-connected system, and to determine whether the output negative sequence reactive power of the grid-connected system meets a preset requirement; the angle value is within a preset angle range;

[0121] The angle value that makes the output negative sequence reactive power of the grid-connected system meet the preset requirement under all three-phase unbalanced working conditions is taken as a first preset angle value.

[0122] In a possible implementation, the negative sequence phase voltage phase determination apparatus 30 of the grid-connected system can further include a grid-connected control module.

[0123] The grid-connected control module is configured to:

[0124] After determining the current negative sequence phase voltage phase of the grid-connected system, a first negative sequence active phase current given value and a first negative sequence reactive phase current given value of the grid-connected system are obtained;

[0125] Based on the first negative sequence active phase current given value, the first negative sequence reactive phase current given value, and the current negative sequence phase voltage phase, a park inverse transformation is performed to obtain an alpha-axis phase current component given value and a beta-axis phase current component given value;

[0126] Based on the alpha-axis phase current component given value, the beta-axis phase current component given value, and the current positive sequence phase voltage phase, a park transformation is performed to obtain a second negative sequence active phase current given value and a second negative sequence reactive phase current given value;

[0127] A positive sequence active phase current given value and a positive sequence reactive phase current given value of the grid-connected system are obtained;

[0128] The positive sequence active phase current given value and the second negative sequence active phase current given value are summed to obtain an active phase current given value, and the positive sequence reactive phase current given value and the second negative sequence reactive phase current given value are summed to obtain a reactive phase current given value;

[0129] Based on the active phase current given value and the reactive phase current given value, the grid-connected system is controlled.

[0130] In a possible implementation, in the grid-connected control module, the first negative sequence reactive phase current given value of the grid-connected system is obtained by:

[0131] A negative sequence variation degree value of the current negative sequence phase voltage and the negative sequence phase voltage of the grid-connected system under a three-phase balanced working condition is obtained.

[0132] The product of the positive sequence change degree value, the preset positive sequence reactive power coefficient and the rated current of the grid-connected system is subjected to amplitude limiting processing to obtain a first positive sequence reactive phase current given value.

[0133] In a possible implementation, in the grid-connected control module, the positive sequence reactive phase current given value of the grid-connected system is obtained by:

[0134] The positive sequence change degree value of the current positive sequence phase voltage of the grid-connected system and the positive sequence phase voltage under the three-phase balanced working condition is obtained.

[0135] The product of the positive sequence change degree value, the preset positive sequence reactive power coefficient and the rated current of the grid-connected system is subjected to amplitude limiting processing to obtain a first positive sequence reactive phase current given value.

[0136] In a possible implementation, the first obtaining module 31 is specifically configured to:

[0137] The current negative sequence active phase voltage and the current negative sequence reactive phase voltage of the grid-connected system are obtained.

[0138] The angle value of the tangent value of the negative sequence phase voltage ratio is taken as a first angle value, and the negative sequence phase voltage ratio is the ratio of the current negative sequence reactive phase voltage to the current negative sequence active phase voltage.

[0139] If the current negative sequence active phase voltage is less than a preset threshold value, the first angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0140] If the current negative sequence active phase voltage is not less than the preset threshold value, the sum of the first angle value and a second preset angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

[0141] Figure 3 is a schematic diagram of the controller provided by the embodiment. As shown in the figure, the controller 4 of the embodiment includes a processor 40 and a memory 41. The memory 41 is configured to store a computer program 42, and the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to perform the steps in each of the above-described grid-connected system negative sequence phase voltage phase determination method embodiments, for example, S101 to S104 as shown in the figure. Alternatively, the processor 40 is configured to invoke and run the computer program 42 stored in the memory 41 to implement the functions of each module / unit in each of the above-described device embodiments, for example, the functions of the modules / units 31 to 34 as shown in the figure. Figure 3 Figure 1 Figure 2

[0142] ​​​For example, the computer program 42 can be divided into one or more modules / units stored in the memory 41 and executed by the processor 40 to accomplish the present application. The one or more modules / units can be a series of computer program instruction segments capable of accomplishing specific functions, which are used to describe the execution process of the computer program 42 in the controller 4. For example, the computer program 42 can be divided into the following modules / units 31 to 34 shown in the figure. Figure 2 The modules / units 31 to 34 shown in the figure.

[0143] The controller 4 can include, but is not limited to, the processor 40 and the memory 41. Those skilled in the art can understand that the controller 4 can include more or fewer components than those shown in the figure, or combine certain components, or include different components, for example, the controller can also include an input / output device, a network access device, a bus, etc. Figure 3 The controller 4 shown in the figure is only an example and does not constitute a limitation on the controller 4, and the controller 4 can include more or fewer components than those shown in the figure, or combine certain components, or include different components, for example, the controller can also include an input / output device, a network access device, a bus, etc.

[0144] The processor 40 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0145] The memory 41 can be an internal storage unit of the controller 4, for example, a hard disk or a memory of the controller 4. The memory 41 can also be an external storage device of the controller 4, for example, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the memory 41 can include both an internal storage unit and an external storage device of the controller 4. The memory 41 is used to store the computer program and other programs and data required by the controller. The memory 41 can also be used to temporarily store data that has been output or will be output.

[0146] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to complete all or part of the above described functions. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific names of each functional unit and module are only for the convenience of mutual distinction, and do not limit the protection scope of the present application. The specific working process of the units and modules in the above system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0147] Corresponding to the above controller, the embodiment of the present application also provides a grid-connected system, comprising the controller according to any one of the above.

[0148] In some possible implementation manners, the grid-connected system can further comprise a grid-connected inverter, an output end of the grid-connected inverter being connected with the power grid, and the grid-connected inverter being controlled by the above controller. The related parameters of the above grid-connected system can be understood as the corresponding parameters of the grid-connected inverter.

[0149] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0150] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0151] In the embodiments of the present application, it should be understood that the disclosed apparatuses / controllers and methods can be implemented in other manners. For example, the embodiments of the apparatuses / controllers described above are merely schematic. For example, the division of the modules or units is merely logical function division. There can be another division manner for the actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections can be indirect couplings or communication connections through some interfaces, devices or units, and can be in electrical, mechanical or other forms.

[0152] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place, or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0153] In addition, each functional unit in the various embodiments of the present application can be integrated into a processing unit, or each unit can exist physically, or two or more units can be integrated into one unit. The integrated unit can be implemented in the form of hardware, or in the form of a software functional unit.

[0154] The integrated module / unit, if implemented in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, all or part of the flow of the above-mentioned embodiment methods can also be implemented by a computer program instructing related hardware to complete, and the computer program can be stored in a computer readable storage medium. When the processor executes the computer program, the steps of each of the above-mentioned grid-connected system negative sequence phase voltage phase determination method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable file or some intermediate form. The computer readable medium can include any entity or device capable of carrying the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0155] The above-described embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for determining the phase of negative sequence phase voltage of a grid-connected system, characterized in that, The method comprises the following steps: obtaining the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system; determining the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system based on the phase difference between the current positive sequence line voltage and the negative sequence line voltage; obtaining the current positive sequence phase voltage phase of the grid-connected system; determining the current negative sequence phase voltage phase of the grid-connected system according to the current positive sequence phase voltage phase and the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage.

2. The method of claim 1, wherein The calculation formula of the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage is: θ1 = θ p -θ2 wherein θ1 is the phase difference between the current positive sequence phase voltage and the negative sequence phase voltage; θ p is a first preset angle value; and θ2 is the phase difference between the current positive sequence line voltage and the negative sequence line voltage.

3. The method of claim 2, wherein the negative sequence phase voltage phase of the grid-connected system is determined by: The determination method of the first preset angle value comprises: constructing the relationship between the phase difference between the positive sequence phase voltage and the negative sequence phase voltage of the grid-connected system and the phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system; for each angle value under each three-phase unbalanced working condition, obtaining the experimental phase difference between the positive sequence line voltage and the negative sequence line voltage of the grid-connected system under the three-phase unbalanced working condition, substituting the angle value and the experimental phase difference into the relationship to obtain the corresponding experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, and based on the experimental phase difference between the positive sequence phase voltage and the negative sequence phase voltage, controlling the grid-connected system, obtaining the output negative sequence reactive power of the grid-connected system, and determining whether the output negative sequence reactive power of the grid-connected system meets the preset requirement; the angle value is within a preset angle range; the angle value that makes the output negative sequence reactive power of the grid-connected system meet the preset requirement under all three-phase unbalanced working conditions is taken as the first preset angle value.

4. The method of claim 1, wherein, After determining the current negative sequence phase voltage phase of the grid-connected system, the method for determining the negative sequence phase voltage phase of the grid-connected system further comprises: obtaining the first negative sequence active phase current given value and the first negative sequence reactive phase current given value of the grid-connected system; based on the first negative sequence active phase current given value, the first negative sequence reactive phase current given value and the current negative sequence phase voltage phase, performing park inverse transformation to obtain the alpha-axis phase current component given value and the beta-axis phase current component given value; based on the alpha-axis phase current component given value, the beta-axis phase current component given value and the current positive sequence phase voltage phase, performing park transformation to obtain the second negative sequence active phase current given value and the second negative sequence reactive phase current given value; obtaining the positive sequence active phase current given value and the positive sequence reactive phase current given value of the grid-connected system; summing the positive sequence active phase current given value and the second negative sequence active phase current given value to obtain the active phase current given value, and summing the positive sequence reactive phase current given value and the second negative sequence reactive phase current given value to obtain the reactive phase current given value; controlling the grid-connected system based on the active phase current given value and the reactive phase current given value.

5. The method of claim 4, wherein, The method for obtaining the first negative sequence reactive phase current given value of the grid-connected system comprises: obtaining the negative sequence change degree value of the current negative sequence phase voltage and the negative sequence phase voltage of the grid-connected system under the three-phase balanced working condition; The product of the negative sequence change degree value, a preset negative sequence reactive power coefficient and a rated current of the grid-connected system is subjected to amplitude limiting processing to obtain a first negative sequence reactive phase current given value.

6. The method of claim 4, wherein, The positive sequence reactive phase current given value of the grid-connected system is obtained, including: A positive sequence change degree value between a current positive sequence phase voltage of the grid-connected system and a positive sequence phase voltage under a three-phase balanced working condition is obtained. The product of the positive sequence change degree value, a preset positive sequence reactive power coefficient and the rated current of the grid-connected system is subjected to amplitude limiting processing to obtain a positive sequence reactive phase current given value.

7. The method of claim 1 to 6, wherein, The phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system is obtained, including: A current negative sequence active phase voltage and a current negative sequence reactive phase voltage of the grid-connected system are obtained. An angle value of a tangent value of a negative sequence phase voltage ratio is taken as a first angle value, the negative sequence phase voltage ratio being a ratio of the current negative sequence reactive phase voltage to the current negative sequence active phase voltage. If the current negative sequence active phase voltage is less than a preset threshold value, the first angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system. If the current negative sequence active phase voltage is not less than the preset threshold value, a sum of the first angle value and a second preset angle value is taken as the phase difference between the current positive sequence line voltage and the negative sequence line voltage of the grid-connected system.

8. A controller characterized by comprising: A memory and a processor are included, the memory being used to store a computer program, and the processor being used to call and run the computer program stored in the memory to execute the negative sequence phase voltage phase determination method of the grid-connected system according to any one of claims 1 to 7.

9. A grid-connected system characterized by, The controller according to claim 8 is included.

10. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 9. The computer program is executed by the processor to implement the steps of the negative sequence phase voltage phase determination method of the grid-connected system according to any one of claims 1 to 7.

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