A method and device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus

Abstract

The present application discloses a method and device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus. The method and device are applied to any of the inverters in the parallel inverters with a common DC bus, specifically collecting the three-phase current output by the inverter; obtaining a first control parameter according to the three-phase current and a given current value; obtaining a second control parameter according to the three-phase current and the reference instruction value; and controlling the pulse width modulation controller output to the inverter based on the first control parameter and the second control parameter to suppress the zero-sequence commutation. Obviously, when the present application performs suppression control on the zero-sequence commutation of the inverter, there is no need to communicate with other inverters, thereby solving the problem of control failure caused by communication failure in the prior art.

Description

Technical Field

[0001] The present application relates to the technical field of electric power equipment, and more specifically, to a method and device for suppressing zero-sequence circulating current between parallel inverters sharing a common DC bus. Background Art

[0002] In order to improve the power level of the system, in high current applications, such as electric traction, energy storage converters, and renewable energy power generation, connecting multiple inverters in parallel is a common method. By connecting inverters in parallel, the power level, reliability, and efficiency of the system can be greatly improved, and it also brings convenience to the capacity expansion and converter design of the system. When multiple inverters with a common DC bus are connected in parallel on the AC side, a zero-sequence circulating current path will be formed between the parallel inverters, generating a zero-sequence circulating current flowing between the parallel inverters. When the zero-sequence circulating current is too large, it will cause problems such as unbalanced stress of the switch tube, grid current distortion, and increased system losses. Therefore, it is necessary to suppress the zero-sequence circulating current.

[0003] Most of the existing circulating current suppression methods are software controlled, that is, by adjusting the redundant zero vector action time, or adjusting the redundant zero vector duty cycle, the correction compensation amount of the zero sequence voltage can be obtained according to the zero sequence current feedback, and then the zero sequence current is suppressed by the PI controller or the deadbeat controller. However, the method of suppressing the circulating current between multiple inverters through software and conducting coordinated control requires real-time monitoring and communication of the current, voltage and other state quantities of each parallel inverter, that is, the parallel effect is achieved by detecting the information of other modules in the parallel system. Therefore, this circulating current suppression method has a strong dependence on the effective communication between the inverters, and once a communication failure occurs, it will cause control failure. Summary of the invention

[0004] In view of this, the present application provides a method and device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus, which is used to suppress zero-sequence circulating current between multiple parallel inverters to solve the problem of control failure caused by communication failure in the prior art.

[0005] In order to achieve the above objectives, the proposed solution is as follows:

[0006] A method for suppressing zero-sequence circulating current between parallel inverters with a common DC bus is applied to any of the inverters in the parallel inverters with a common DC bus. The method comprises the following steps:

[0007] Collecting the three-phase current output by the inverter;

[0008] Obtaining a first control parameter according to the three-phase current and a given current value;

[0009] Obtaining a second control parameter according to the three-phase current and the reference instruction value;

[0010] A pulse width modulation controller output to the inverter is controlled based on the first control parameter and the second control parameter to suppress the zero-sequence commutation.

[0011] Optionally, obtaining the first control parameter according to the three-phase current and the given current value comprises the steps of:

[0012] Performing Clark transformation and Park transformation on the three-phase current in sequence to obtain current components of the first three-phase current in a two-phase synchronous rotating coordinate system;

[0013] Calculation is performed based on the current component and the given current value, and the current control parameter obtained by the calculation is output to obtain the current controller of the inverter, so that the current controller outputs the first control parameter.

[0014] Optionally, obtaining the second control parameter according to the three-phase current and the reference instruction value comprises the steps of:

[0015] Calculating zero-sequence circulating current according to the three-phase current;

[0016] A second control parameter is obtained by searching on a circulating current control droop curve of the inverter based on the zero-sequence circulating current and the reference command value.

[0017] Optionally, the collecting of the three-phase current output by the inverter comprises the steps of:

[0018] The current signal output by the current sensor of the inverter is acquired to obtain the three-phase current.

[0019] Optionally, the second control parameter is zero-sequence compensation voltage or zero-sequence zero vector action time.

[0020] A device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus, applied to any of the inverters in the parallel inverters with a common DC bus, the device comprising:

[0021] A current acquisition module is configured to acquire the three-phase current output by the inverter;

[0022] A first calculation module is configured to obtain a first control parameter according to the three-phase current and a given current value;

[0023] A second control module is configured to obtain a second control parameter according to the three-phase current and the reference command value;

[0024] The control execution module is configured to control the pulse width modulation controller output to the inverter based on the first control parameter and the second control parameter to suppress the zero-sequence commutation.

[0025] Optionally, the first calculation module includes:

[0026] a first calculation unit, configured to perform Clark transformation and Park transformation on the three-phase current in sequence to obtain current components of the first three-phase current in a two-phase synchronous rotating coordinate system;

[0027] The second calculation unit is used to perform calculation based on the current component and the given current value, and output the current control parameter obtained by calculation to obtain the current controller of the inverter, so that the current controller outputs the first control parameter.

[0028] Optionally, the second calculation module includes:

[0029] A third calculation unit, used for calculating the zero-sequence circulating current according to the three-phase current;

[0030] The fourth calculation unit is used to search on the circulating current control droop curve of the inverter based on the zero-sequence circulating current and the reference command value to obtain a second control parameter.

[0031] Optionally, the collecting of the three-phase current output by the inverter comprises the steps of:

[0032] The current signal output by the current sensor of the inverter is acquired to obtain the three-phase current.

[0033] Optionally, the second control parameter is zero-sequence compensation voltage or zero-sequence zero vector action time.

[0034] It can be seen from the above technical scheme that the present application discloses a method and device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus. The method and device are applied to any of the inverters in the parallel inverters with a common DC bus, specifically collecting the three-phase current output by the inverter; obtaining a first control parameter according to the three-phase current and a given current value; obtaining a second control parameter according to the three-phase current and the reference instruction value; and controlling the pulse width modulation controller output to the inverter based on the first control parameter and the second control parameter to suppress the zero-sequence commutation. Obviously, when the present application performs suppression control on the zero-sequence commutation of the inverter, there is no need to communicate with other inverters, thereby solving the problem of control failure caused by communication failure in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 This is a flow chart of a method for suppressing zero-sequence circulating current between parallel inverters with a common DC bus according to an embodiment of the present application;

[0037] Figure 2 This is the system structure diagram and circulation diagram of multiple parallel inverters;

[0038] Figure 3 This is a structural diagram of the circulation flow droop control of an embodiment of the present application;

[0039] Figure 4 A schematic diagram of a circulating current droop controller for parallel inverters according to an embodiment of the present application;

[0040] Figure 5 A schematic diagram of a circulation droop curve of an embodiment of the present application;

[0041] Figure 6 A block diagram of a device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus according to an embodiment of the present application. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0043] Embodiment 1

[0044] Figure 1 This is a flow chart of a method for suppressing zero-sequence circulating current between parallel inverters with a common DC bus according to an embodiment of the present application.

[0045] The suppression method provided in this embodiment is applicable to any inverter in an environment where multiple inverters are connected in parallel. The relationship between the multiple inverters here is that they share a common DC bus and are connected in parallel at the AC output end. Figure 2 shown.

[0046] like Figure 1 As shown, the suppression method in this embodiment includes the following steps:

[0047] S1, collect the three-phase current output by the inverter.

[0048] The three-phase current i output by the AC output terminal of the corresponding inverter is collected by the current sensor of each inverter abc .

[0049] S2. Obtain a first control parameter according to the three-phase current and a given current value.

[0050] The first control parameter can be used alone to control the current of the inverter. Specifically, when calculating the first control parameter, the following steps are adopted:

[0051] First, the three-phase current signal i of the inverter abc After Clark transformation and Park transformation, the current component i in the two-phase synchronous rotating coordinate system is obtained. dq .

[0052] Then, calculate the current component i dq The difference between the current reference command value dq and the given current is calculated to obtain a current control parameter, which is then output to the inverter's current controller via the current loop PI controller, so that the current controller outputs a first control parameter to the inverter's pulse width modulation controller.

[0053] S3. Calculate the second control parameter according to the three-phase current and the reference command value.

[0054] First, the zero-sequence circulating current i is obtained by calculating the three-phase current output by the inverter. z .

[0055] In step 3, the zero-sequence circulating current i z Generally defined as

[0056] i z =i a +i b +i c (1)

[0057] Zero sequence voltage definition is the same as above

[0058] u z =u a +u b +u c (2)

[0059] Then, the zero-sequence circulating current i fed back is z The reference command value i of the zero-sequence circulating current zref By comparison, a search is performed on the circulating current control droop curve corresponding to the corresponding inverter according to the magnitude of the measured circulating current and the reference command value to obtain a second control parameter, which may be a zero-sequence compensation voltage or a redundant zero vector action time.

[0060] When multiple inverters are connected in parallel, each inverter has an independent circulating current control droop curve. Here, the droop function between the circulating current and the corrected zero-sequence voltage is taken as an example. zref , when the actual circulating current i z with i zref When they are not equal, the corrected zero-sequence voltage that needs to be compensated will change along the set circulating current droop curve. The corrected zero-sequence voltage that needs to be compensated output by the droop controller is used as an additional value, which is superimposed with the output of the main controller as the control quantity of the inverter, which can achieve the effect of suppressing the circulating current.

[0061] For the first inverter, the following relationship exists:

[0062]

[0063] Under the condition of balanced voltage of three-phase power grid, add the three equations and substitute them into equation (1) and (2) to get

[0064]

[0065] That is, for each inverter, the zero-sequence voltage can be independently adjusted to adjust the zero-sequence current through a certain droop control relationship.

[0066] For the case of two inverters connected in parallel, there is the following relationship:

[0067]

[0068] △u z =u 1z -u 2z (6)

[0069] Figure 3 The figure shows the structure diagram of the circulating current droop control of multiple inverters in parallel. d1 、i q1 、i d1_ref 、i q1_ref are the d-axis component and q-axis component of the grid-connected current of the first inverter and their reference values, i dn 、i qn 、i dn_ref 、i qn_ref are the d-axis component and q-axis component of the grid-connected current of the nth inverter and their reference values, △u z The zero-sequence voltage compensation value output by the droop circulating current controller.

[0070] Figure 4 The schematic diagram of the circulating current droop controller for parallel inverters. d 、e qare the d-axis and q-axis components of the three-phase grid voltage, u dref 、u qref are the d-axis and q-axis components of the three-phase voltage reference value output by the current controller, ω represents the grid current angular frequency, and L represents the filter inductance.

[0071] Figure 5 Figure 1 is a schematic diagram of the droop characteristic curve of the circulating current. Ignoring the influence of resistance, from equations (4) and (5), the slope of the droop curve between the zero-sequence voltage and the zero-sequence current is largely determined by the inductance. The larger the value of the three-phase filter inductance, the larger the slope of the droop curve. When the actual value of the circulating current is not equal to the given value, it is necessary to adjust the zero-sequence voltage to make the actual value of the circulating current tend to the given value. For the same size of circulating current change, for a large inductor, the voltage change on the inductor is greater, so a larger zero-sequence compensation voltage is required to adjust, which corresponds to a larger slope of the droop curve.

[0072] Similarly, when the inductance is relatively small, the slope of the corresponding droop curve is relatively small. zref After that, the reference value of the circulation is determined, which is generally 0. Collect the circulation in the actual system z , when i z1 zref , the points on the sag curve need to be moved up along the curve to approach i zref , then at this time △u z Also increases along the curve, the corrected zero-sequence voltage increases, and is added to the output of the main controller as an additional amount; similarly, when i z2 >i zref , at this time, the point on the sag curve needs to move down along the curve, △u z becomes smaller, and the corrected zero-sequence voltage becomes smaller.

[0073] Since the differences in hardware parameters of multiple parallel inverters are not considered, the slope of the circulating current droop curve of each inverter is consistent. When the circulating current reference value is given, the operating point of each inverter will converge to the same point on the droop curve. Therefore, if the circulating current droop curve is selected appropriately, the correction amount of the zero-sequence voltage can be directly obtained from the droop curve, while avoiding the controller from performing a large amount of calculations, and the circulating current between parallel inverters can be effectively suppressed by changing the zero-sequence voltage.

[0074] S4. Output the first control parameter and the second control parameter to the pulse width modulation controller.

[0075] ​That is, the pulse width of the output pulse width signal of the pulse width modulation controller is adjusted based on the first control parameter and the second control parameter. That is, the zero-sequence compensation voltage or zero-sequence voltage action time required for compensation is added as an additional amount to the output signal of the pulse width modulation controller that controls the operation of the inverter, and after superposition, it is used as a given signal of the SPWM or SVPWM modulation module to achieve the suppression of the zero-sequence circulating current of the parallel inverter.

[0076] The superimposed three-phase modulation wave is input to the SPWM or SVPWM modulation module, and the output pulse sequence directly controls the inverter.

[0077]

[0078] It can be seen from the above technical solution that this embodiment provides a method for suppressing zero-sequence circulating current between parallel inverters with a common DC bus. The method is applied to any of the inverters in the parallel inverters with a common DC bus, specifically collecting the three-phase current output by the inverter; obtaining a first control parameter according to the three-phase current and a given current value; obtaining a second control parameter according to the three-phase current and the reference instruction value; and controlling the pulse width modulation controller output to the inverter based on the first control parameter and the second control parameter to suppress the zero-sequence commutation. Obviously, when the present application performs suppression control on the zero-sequence commutation of the inverter, there is no need to communicate with other inverters, thereby solving the problem of control failure caused by communication failure in the prior art.

[0079] In addition, the circulating current suppression method of multiple parallel inverters based on the droop control strategy of the present application is mainly characterized in that for the circulating current problem between multiple parallel inverters, control strategies such as PI control or deadbeat control are usually adopted. Here, a circulating current droop control strategy is proposed. By detecting the zero-sequence circulating current size of each inverter, according to the set droop characteristic curve, the compensation corrected zero-sequence voltage or the action time of the redundant zero vector can be directly obtained from the curve, and there is no need for communication between the inverters. On the one hand, if a suitable circulating current droop curve can be obtained according to the characteristics of the inverter and the external circuit, the compensated zero-sequence voltage output can be controlled by simply looking up the points on the curve, which is similar to looking up a table, eliminating tedious calculation steps, and requiring low calculation and processing capabilities of the controller, which can greatly save the cost of the controller.

[0080] This method is also applicable when multiple inverters are connected in parallel. For example, when three inverters are connected in parallel, the first two parallel inverters can suppress the circulating current as if there are only two inverters connected in parallel. When controlling the circulating current of the third inverter, the first two parallel modules can be regarded as a virtual whole module, and the droop control of the circulating current is independent of each other, and there is no need for the parallel inverters to communicate with each other, so the circulating current between multiple parallel inverters can be effectively suppressed.

[0081] Embodiment 2

[0082] Figure 6 A block diagram of a device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus according to an embodiment of the present application.

[0083] The suppression device provided in this embodiment is applied to any inverter in an environment where multiple inverters are connected in parallel. The relationship between the multiple inverters here is that they share a common DC bus and are connected in parallel at the AC output end. Figure 2 shown.

[0084] like Figure 6 As shown, the suppression device in this embodiment includes a current acquisition module 10 , a first calculation module 20 , a second calculation module 30 and a control execution module 40 .

[0085] The current acquisition module is used to collect the three-phase current output by the inverter.

[0086] Specifically, the three-phase current i outputted from the AC output terminal of the corresponding inverter is collected by the current sensor of each inverter. abc .

[0087] The first calculation module is used to obtain a first control parameter according to the three-phase current and a given current value.

[0088] The first control parameter can be used alone to control the current of the inverter. The module specifically includes a first calculation unit and a second calculation unit.

[0089] The first calculation unit is used for calculating the three-phase current signal i of the inverter abc After Clark transformation and Park transformation, the current component i in the two-phase synchronous rotating coordinate system is obtained. dq .

[0090] The second calculation unit is used to calculate the current component i dq The difference between the current reference command value dq and the given current is calculated to obtain a current control parameter, which is then output to the inverter's current controller via the current loop PI controller, so that the current controller outputs a first control parameter to the inverter's pulse width modulation controller.

[0091] The second calculation module is used to calculate the second control parameter according to the three-phase current and the reference command value. The module specifically includes a third calculation unit and a fourth calculation unit.

[0092] The third calculation unit is used to calculate the zero-sequence circulating current i according to the three-phase current output by the inverter. z .

[0093] In step 3, the zero-sequence circulating current i z Generally defined as

[0094] i z =i a +i b +i c (1)

[0095] Zero sequence voltage definition is the same as above

[0096] u z =u a +u b +u c (2)

[0097] The fourth calculation unit is used to feed back the zero-sequence circulating current i z The reference command value i of the zero-sequence circulating current zref By comparison, a search is performed on the circulating current control droop curve corresponding to the corresponding inverter according to the magnitude of the measured circulating current and the reference command value to obtain a second control parameter, which may be a zero-sequence compensation voltage or a redundant zero vector action time.

[0098] When multiple inverters are connected in parallel, each inverter has an independent circulating current control droop curve. Here, the droop function between the circulating current and the corrected zero-sequence voltage is taken as an example. zref , when the actual circulating current i z with i zref When they are not equal, the corrected zero-sequence voltage that needs to be compensated will change along the set circulating current droop curve. The corrected zero-sequence voltage that needs to be compensated output by the droop controller is used as an additional value, which is superimposed with the output of the main controller as the control quantity of the inverter, which can achieve the effect of suppressing the circulating current.

[0099] For the first inverter, the following relationship exists:

[0100]

[0101] Under the condition of balanced voltage of three-phase power grid, add the three equations and substitute them into equation (1) and (2) to get

[0102]

[0103] That is, for each inverter, the zero-sequence voltage can be independently adjusted to adjust the zero-sequence current through a certain droop control relationship.

[0104] For the case of two inverters connected in parallel, there is the following relationship:

[0105]

[0106] △u z =u 1z -u 2z (6)

[0107] Figure 3 The figure shows the structure diagram of the circulating current droop control of multiple inverters in parallel. d1 、i q1 、i d1_ref 、i q1_ref are the d-axis component and q-axis component of the grid-connected current of the first inverter and their reference values, i dn 、i qn 、i dn_ref 、i qn_ref are the d-axis component and q-axis component of the grid-connected current of the nth inverter and their reference values, △u z The zero-sequence voltage compensation value output by the droop circulating current controller.

[0108] Figure 4 The schematic diagram of the circulating current droop controller for parallel inverters. d 、e q are the d-axis and q-axis components of the three-phase grid voltage, u dref 、u qref are the d-axis and q-axis components of the three-phase voltage reference value output by the current controller, ω represents the grid current angular frequency, and L represents the filter inductance.

[0109] Figure 5 Figure 1 is a schematic diagram of the droop characteristic curve of the circulating current. Ignoring the influence of resistance, from equations (4) and (5), the slope of the droop curve between the zero-sequence voltage and the zero-sequence current is largely determined by the inductance. The larger the value of the three-phase filter inductance, the larger the slope of the droop curve. When the actual value of the circulating current is not equal to the given value, it is necessary to adjust the zero-sequence voltage to make the actual value of the circulating current tend to the given value. For the same size of circulating current change, for a large inductor, the voltage change on the inductor is greater, so a larger zero-sequence compensation voltage is required to adjust, which corresponds to a larger slope of the droop curve.

[0110] Similarly, when the inductance is relatively small, the slope of the corresponding droop curve is relatively small. zref After that, the reference value of the circulation is determined, which is generally 0. Collect the circulation in the actual system z , when i z1 <izref , the points on the sag curve need to be moved up along the curve to approach i zref , then at this time △u z Also increases along the curve, the corrected zero-sequence voltage increases, and is added to the output of the main controller as an additional amount; similarly, when i z2 >i zref , at this time, the point on the sag curve needs to move down along the curve, △u z becomes smaller, and the corrected zero-sequence voltage becomes smaller.

[0111] Since the differences in hardware parameters of multiple parallel inverters are not considered, the slope of the circulating current droop curve of each inverter is consistent. When the circulating current reference value is given, the operating point of each inverter will converge to the same point on the droop curve. Therefore, if the circulating current droop curve is selected appropriately, the correction amount of the zero-sequence voltage can be directly obtained from the droop curve, while avoiding the controller from performing a large amount of calculations, and the circulating current between parallel inverters can be effectively suppressed by changing the zero-sequence voltage.

[0112] The control execution module is used to output the first control parameter and the second control parameter to the pulse width modulation controller.

[0113] That is, the pulse width of the output pulse width signal of the pulse width modulation controller is adjusted based on the first control parameter and the second control parameter. That is, the zero-sequence compensation voltage or zero-sequence voltage action time required for compensation is added as an additional amount to the output signal of the pulse width modulation controller that controls the operation of the inverter, and after superposition, it is used as a given signal of the SPWM or SVPWM modulation module to achieve the suppression of the zero-sequence circulating current of the parallel inverter.

[0114] The superimposed three-phase modulation wave is input to the SPWM or SVPWM modulation module, and the output pulse sequence directly controls the inverter.

[0115]

[0116] It can be seen from the above technical scheme that this embodiment provides a device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus. The device is applied to any of the inverters in the parallel inverters with a common DC bus, and is specifically used to collect the three-phase current output by the inverter; obtain a first control parameter according to the three-phase current and a given current value; obtain a second control parameter according to the three-phase current and the reference instruction value; and control the pulse width modulation controller output to the inverter based on the first control parameter and the second control parameter to suppress the zero-sequence commutation. Obviously, when the present application performs suppression control on the zero-sequence commutation of the inverter, there is no need to communicate with other inverters, thereby solving the problem of control failure caused by communication failure in the prior art.

[0117] In addition, the circulating current suppression method of multiple parallel inverters based on the droop control strategy of the present application is mainly characterized in that for the circulating current problem between multiple parallel inverters, control strategies such as PI control or deadbeat control are usually adopted. Here, a circulating current droop control strategy is proposed. By detecting the zero-sequence circulating current size of each inverter, according to the set droop characteristic curve, the compensation corrected zero-sequence voltage or the action time of the redundant zero vector can be directly obtained from the curve, and there is no need for communication between the inverters. On the one hand, if a suitable circulating current droop curve can be obtained according to the characteristics of the inverter and the external circuit, the compensated zero-sequence voltage output can be controlled by simply looking up the points on the curve, which is similar to looking up a table, eliminating tedious calculation steps, and requiring low calculation and processing capabilities of the controller, which can greatly save the cost of the controller.

[0118] This method is also applicable when multiple inverters are connected in parallel. For example, when three inverters are connected in parallel, the first two parallel inverters can suppress the circulating current as if there are only two inverters connected in parallel. When controlling the circulating current of the third inverter, the first two parallel modules can be regarded as a virtual whole module, and the droop control of the circulating current is independent of each other, and there is no need for the parallel inverters to communicate with each other, so the circulating current between multiple parallel inverters can be effectively suppressed.

[0119] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0120] It will be appreciated by those skilled in the art that the embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the embodiments of 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 embodiments of 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 codes.

[0121] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the 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 the combination of the 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 terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0122] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including 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.

[0123] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable terminal device. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0124] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0125] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0126] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for suppressing zero-sequence circulating current between parallel inverters with a common DC bus, applied to any of the inverters in the parallel inverters with a common DC bus, characterized in that: The inhibition method comprises the steps of: Collecting the three-phase current output by the inverter; Obtaining a first control parameter according to the three-phase current and a given current value, specifically, performing Clark transformation and Park transformation on the three-phase current in sequence to obtain current components of the three-phase current in a two-phase synchronous rotating coordinate system, performing calculation based on the current components and the given current value, and outputting the calculated current control parameter to a current controller of the inverter, so that the current controller outputs the first control parameter; Obtaining a second control parameter according to the three-phase current and the reference command value, specifically, calculating a zero-sequence circulating current according to the three-phase current, searching on a circulating current control droop curve of the inverter based on the zero-sequence circulating current and the reference command value, to obtain the second control parameter, wherein the second control parameter is a zero-sequence compensation voltage or a zero-sequence zero vector action time; The first control parameter and the second control parameter are controlled and output to a pulse width modulation controller of the inverter to suppress the zero-sequence circulating current.

2. The method of claim 1, wherein: The collecting of the three-phase current output by the inverter comprises the steps of: The current signal output by the current sensor of the inverter is acquired to obtain the three-phase current.

3. A device for suppressing zero-sequence circulating current between parallel inverters with a common DC bus, applied to any of the inverters in the parallel inverters with a common DC bus, characterized in that: The suppression device comprises: A current acquisition module is configured to acquire the three-phase current output by the inverter; A first calculation module is configured to obtain a first control parameter according to the three-phase current and a given current value; A second calculation module is configured to obtain a second control parameter according to the three-phase current and the reference command value; A control execution module is configured to control the first control parameter and the second control parameter to be output to a pulse width modulation controller of the inverter to suppress the zero-sequence circulating current; The first calculation module includes a first calculation unit and a second calculation unit, the first calculation unit is used to perform Clark transformation and Park transformation on the three-phase current in sequence to obtain current components of the three-phase current in a two-phase synchronous rotating coordinate system, and the second calculation unit is used to perform calculation based on the current components and a given current value, and output the calculated current control parameter to the current controller of the inverter, so that the current controller outputs a first control parameter; The second calculation module includes a third calculation unit and a fourth calculation unit, the third calculation unit is used to calculate the zero-sequence circulating current according to the three-phase current, and the fourth calculation unit is used to search on the circulating current control droop curve of the inverter based on the zero-sequence circulating current and the reference instruction value to obtain a second control parameter, wherein the second control parameter is a zero-sequence compensation voltage or a zero-sequence zero vector action time.

4. The suppression device according to claim 3, characterized in that The collecting of the three-phase current output by the inverter comprises the steps of: The current signal output by the current sensor of the inverter is acquired to obtain the three-phase current.

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