Fault ride-through control method and device and grid-connected inverter

Abstract

The invention discloses a fault ride-through control method and device and a grid-connected inverter, and relates to the technical field of power generation. The fault ride-through control method comprises the following steps: acquiring an output voltage phase angle and a first control signal of a grid-connected inverter, wherein the first control signal is used for adjusting reactive power output of the grid-connected inverter; determining a reset signal according to the preset voltage ride-through signal and the current limiting signal; determining a reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal; according to the output voltage phase angle and the reactive voltage reference, a target pulse width modulation signal is generated so as to control fault ride-through of the grid-connected inverter, and the target pulse width modulation signal is used for controlling on-off of a power device. According to the embodiment of the invention, the method facilitates the improvement or elimination of the deviation voltage caused by the lag when the fault state is switched to the normal working state, and can improve the stability of a power system.

Description

Technical Field

[0001] The present application belongs to the field of power generation technology, and specifically relates to a fault ride-through control method, device and grid-connected inverter. Background Art

[0002] The control strategy of the virtual synchronous generator (VSG) based on the inverter has attracted widespread attention due to its functions such as frequency and voltage regulation, inertia support and fault ride-through. During the process of achieving fault ride-through, the output current on the inverter side increases sharply due to the voltage drop on the grid side. Limited by the overcurrent capacity of the inverter, the inverter is prone to safety accidents such as disconnection from the grid during the fault ride-through process. An effective current limiting strategy is the key to achieving fault ride-through.

[0003] In the prior art, the current limiting strategies mainly include virtual impedance and voltage limiter. However, the adjustment of virtual impedance may take a certain amount of time to respond to system changes, especially under rapidly changing load conditions. This response lag may cause deviation voltage problems; when the voltage limiter returns to normal state, its process of releasing the limit may be delayed, which in turn causes deviation voltage problems during the voltage recovery process.

[0004] In summary, the current limiting strategy in the prior art has the problem of deviation voltage, resulting in the stability of the power system to be improved. Summary of the invention

[0005] The technical problem to be solved by the present application is to provide a fault ride-through control method, device and grid-connected inverter in view of the above-mentioned deficiencies in the prior art. The use of this method is conducive to improving or eliminating the deviation voltage caused by the lag in switching from a fault state to a normal working state, thereby improving the stability of the power system.

[0006] In a first aspect, an embodiment of the present application provides a fault ride-through control method, including: obtaining an output voltage phase angle and a first control signal of a grid-connected inverter, the first control signal being used to adjust the reactive power output of the grid-connected inverter; determining a reset signal according to a preset voltage ride-through signal and a current limiting signal, the reset signal being used to determine whether to reset an integral link of a reactive loop of the grid-connected inverter; determining a reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal; generating a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference to control the fault ride-through of the grid-connected inverter, the target pulse width modulation signal being used to control the on and off of power devices.

[0007] In some embodiments of the first aspect, a reset signal is determined based on a preset voltage crossing signal and a current limiting signal, including: when the preset voltage crossing signal is a first level and the current limiting signal is a first level, determining the reset signal to be a second level, wherein the first level is opposite to the second level; or, when the preset voltage crossing signal is a second level and the current limiting signal is a first level, determining the reset signal to be a first level; or, when the preset voltage crossing signal is a first level and the current limiting signal is a second level, determining the reset signal to be a first level; or, when the preset voltage crossing signal is a second level and the current limiting signal is a second level, determining the reset signal to be a second level.

[0008] In some embodiments of the first aspect, the reactive voltage reference corresponding to the first control signal is determined according to a preset voltage crossing signal and a reset signal, including: when the preset voltage crossing signal is a first level and the reset signal is a second level, the reactive voltage reference corresponding to the first control signal is determined to be a preset reference voltage, wherein the first level and the second level are opposite; or, when the preset voltage crossing signal is a second level and the reset signal is a first level, the reactive voltage reference corresponding to the first control signal is determined to be the preset reference voltage; or, when the preset voltage crossing signal is a first level and the reset signal is a first level, the reactive voltage reference corresponding to the first control signal is determined to be the preset reference voltage; or, when the preset voltage crossing signal is a second level and the reset signal is a second level, the reactive voltage reference corresponding to the first control signal is determined to be a first value, the first value being the sum of the integral of the first control signal and the preset reference voltage.

[0009] In some embodiments of the first aspect, obtaining the output voltage phase angle of the grid-connected inverter includes: obtaining the active power and the active power reference of the grid-connected inverter; determining the difference between the active power reference and the active power as the active power deviation; determining the target active power according to the active power deviation when the preset voltage crossing signal is at a first level; determining the target angular frequency according to the target active power; and determining the output voltage phase angle of the grid-connected inverter according to the target angular frequency.

[0010] In some embodiments of the first aspect, the target active power is determined based on the active power deviation, including: when the active power deviation is greater than the deviation threshold, determining the target active power as the deviation threshold; or, when the active power deviation is less than or equal to the deviation threshold, determining the target active power as the active power deviation.

[0011] In some embodiments of the first aspect, a target pulse width modulation signal is generated according to an output voltage phase angle and a reactive voltage reference, comprising: obtaining a grid-side d-axis current, a grid-side q-axis current, and a d-axis voltage and a q-axis voltage of a common connection point; determining a d-axis voltage reference and a q-axis voltage reference of an outer voltage loop according to the output voltage phase angle and the reactive voltage reference; determining a d-axis current reference and a q-axis current reference of an inner current loop according to the grid-side d-axis current, the grid-side q-axis current, the d-axis voltage, the q-axis voltage, the d-axis voltage reference, and the q-axis voltage reference; determining a target d-axis current reference and a target q-axis current reference according to the d-axis current reference and the q-axis current reference; determining a q-axis modulation voltage and a q-axis modulation voltage of a modulation wave according to the target d-axis current reference and the target q-axis current reference; and generating a target pulse width modulation signal according to the q-axis modulation voltage and the q-axis modulation voltage.

[0012] In some implementations of the first aspect, determining a target d-axis current reference and a target q-axis current reference according to a d-axis current reference and a q-axis current reference comprises: determining the target d-axis current reference and the target q-axis current reference based on the d-axis current reference, the q-axis current reference and formula (1); formula (1) comprises:

[0013]

[0014] Among them, i ref ' represents the target d-axis current reference or the target q-axis current reference; i ref Indicates the d-axis current reference or the q-axis current reference; I M represents the current threshold; φ represents the current phase angle; j represents the imaginary inertia.

[0015] In some implementations of the first aspect, before determining the reset signal according to the preset voltage ride-through signal and the current limiting signal, the method further comprises: od , q-axis voltage V oq and preset reference voltage V ref When formula (2) is satisfied and a delay link is passed, a preset voltage ride-through signal is triggered;

[0016] Formula (2) includes:

[0017]

[0018] After the preset voltage crossing signal is triggered, a reset signal is triggered after a delay link; or, when the grid-side d-axis current I gd , grid-side q-axis current I gq and the current threshold I M When the formula (3) is satisfied, the current limiting signal is triggered;

[0019] Formula (3) includes:

[0020]

[0021] Based on the same inventive concept, in a second aspect, an embodiment of the present application also provides a fault ride-through control device, including: a first acquisition module, used to acquire the output voltage phase angle and a first control signal of the grid-connected inverter, the first control signal being used to adjust the reactive power output of the grid-connected inverter; a first determination module, connected to the first acquisition module, used to determine a reset signal according to a preset voltage ride-through signal and a current limiting signal, the reset signal being used to determine whether to reset the integral link of the reactive loop of the grid-connected inverter; a second determination module, connected to the first determination module, used to determine a reactive voltage reference corresponding to the first control signal according to a preset voltage ride-through signal and a reset signal; a first generation module, connected to the second determination module, used to control the fault ride-through of the grid-connected inverter according to the output voltage phase angle and the reactive voltage reference, and generate a target pulse width modulation signal, the target pulse width modulation signal being used to control the on and off of the power device.

[0022] In some embodiments of the second aspect, the first determination module is specifically used to: when the preset voltage crossing signal is a first level and the current limiting signal is a first level, determine that the reset signal is a second level, wherein the first level is opposite to the second level; or, when the preset voltage crossing signal is a second level and the current limiting signal is a first level, determine that the reset signal is a first level; or, when the preset voltage crossing signal is a first level and the current limiting signal is a second level, determine that the reset signal is a first level; or, when the preset voltage crossing signal is a second level and the current limiting signal is a second level, determine that the reset signal is a second level.

[0023] In some implementations of the second aspect, the second determining module is specifically configured to:

[0024] When the preset voltage crossing signal is a first level and the reset signal is a second level, the reactive voltage reference corresponding to the first control signal is determined to be a preset reference voltage, wherein the first level and the second level are opposite; or, when the preset voltage crossing signal is a second level and the reset signal is a first level, the reactive voltage reference corresponding to the first control signal is determined to be the preset reference voltage; or, when the preset voltage crossing signal is a first level and the reset signal is a first level, the reactive voltage reference corresponding to the first control signal is determined to be the preset reference voltage; or, when the preset voltage crossing signal is a second level and the reset signal is a second level, the reactive voltage reference corresponding to the first control signal is determined to be a first value, and the first value is the sum of the integral of the first control signal and the preset reference voltage.

[0025] In some embodiments of the second aspect, the first acquisition module is specifically used to: obtain the active power and active power reference of the grid-connected inverter; determine the difference between the active power reference and the active power as the active power deviation; when the preset voltage crossing signal is a first level, determine the target active power according to the active power deviation; determine the target angular frequency according to the target active power; and determine the output voltage phase angle of the grid-connected inverter according to the target angular frequency.

[0026] Based on the same inventive concept, in a third aspect, an embodiment of the present application further provides a grid-connected inverter, comprising a grid-connected inverter body and a fault-crossing control device as described in any one of the second aspects.

[0027] According to the fault ride-through control method, device and grid-connected inverter provided in the embodiments of the present application, a reset signal is determined according to a preset voltage ride-through signal and a current limiting signal to determine whether to reset the integral link of the reactive loop of the grid-connected inverter, which is beneficial to resetting the integral link of the reactive loop after the fault is cleared, thereby improving or eliminating the hysteresis existing in switching from the fault state to the normal working state, thereby improving or eliminating the deviation voltage caused by the hysteresis to improve the stability of the power system; according to the preset voltage ride-through signal and the reset signal, a reactive voltage reference corresponding to the first control signal is determined, and a target pulse width modulation signal is generated according to the output voltage phase angle and the reactive voltage reference, that is, during the fault ride-through period, the grid-connected inverter can control the on and off of the power device through the target pulse width modulation signal, adjust the phase angle and reactive power, so as to ensure the phase synchronization between the grid-connected inverter and the power grid, so as to realize the fault ride-through control of the grid-connected inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The schematic diagram of the control architecture of the traditional grid-connected inverter based on virtual synchronous machine control is shown;

[0029] Figure 2 A schematic diagram showing a flow chart of a fault ride-through control method provided in an embodiment of the present application;

[0030] Figure 3 A schematic diagram of the power ring principle provided by an embodiment of the present application is shown;

[0031] Figure 4 A schematic diagram of control logic signals provided by an embodiment of the present application is shown;

[0032] Figure 5 A schematic diagram showing a control architecture of a fault ride-through control method provided in an embodiment of the present application is shown;

[0033] Figure 6 An overview of a comprehensive fault ride-through strategy based on reactive loop reset in a fault ride-through control method provided in an embodiment of the present application is shown;

[0034] Figure 7 A schematic diagram showing simulation results of active power and reactive power in the prior art;

[0035] Figure 8 A schematic diagram showing simulation results of active power and reactive power provided in an embodiment of the present application is shown;

[0036] Fig. 9 A schematic diagram showing a simulation result of grid-side current in the prior art;

[0037] Fig.10 A schematic diagram showing a simulation result of the grid-side current provided in an embodiment of the present application;

[0038] Fig.11 A phase plane diagram in the prior art is shown;

[0039] Fig.12 A schematic diagram showing a power angle curve in the prior art;

[0040] Fig.13 The phase plane diagram provided by the embodiment of the present application is shown;

[0041] Fig.14 A schematic diagram showing a power angle curve provided in an embodiment of the present application;

[0042] Fig.15 A structural schematic diagram of a fault-ride-through control device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0044] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application and are not configured to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0045] 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 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 device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0046] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0047] In order to better understand the fault ride-through control method provided in the embodiment of the present application, the prior art that may be involved in the embodiment of the present application is described below.

[0048] The control system structure diagram of the traditional grid-type inverter based on virtual synchronous machine is as follows: Figure 1 As shown. The control system includes a main circuit, an outer loop power control (i.e., reactive loop and active loop) and an inner loop voltage and current control (i.e., voltage outer loop and current inner loop). The outer loop power control adjusts the active power and reactive power to output a voltage amplitude given signal and a voltage phase given value (synchronization signal). Then, the voltage amplitude and phase are used as given values ​​for the inner loop voltage and current control. The inner loop voltage and current control can effectively improve the dynamic response performance of the output voltage and current, and limit the current under inverter faults. Finally, the modulation signal output by the inner loop voltage and current control generates a drive signal for the power device through a space vector pulse width modulation (SVPWM) generator to achieve normal operation of the inverter.

[0049] Among them, R f Represents parasitic resistance; L f Represents filter inductance; C f Indicates filter capacitor; L g Represents the grid-side inductance; R g represents the grid-side resistance; e represents the output voltage of the inverter; V g represents the grid-side voltage; P represents the output active power; Q represents the output reactive power; P ref Indicates the output active power command (i.e. active power reference), Qref Indicates the output reactive power instruction (i.e. reactive power reference); v o Represents the voltage at the point of common connection (PCC); i o Represents the current at the common connection point; i g Indicates the grid-side current; V od Indicates v o The d-axis component after Park transformation; V oq Indicates v o The q-axis component after Park transformation; I od Indicates i o The d-axis component after Park transformation; I oq Indicates i o The q-axis component after Park transformation; I gd Indicates i g The d-axis component after Park transformation; I gq Indicates i g The q-axis component after Park transformation; V odref Represents the d-axis reference of the voltage outer loop; V oqref Represents the q-axis reference of the voltage outer loop; I odref Indicates the d-axis reference of the inner current loop; I oqref represents the q-axis reference of the inner current loop; E dref Indicates the d-axis reference of the modulated wave; E qref represents the q-axis reference of the modulated wave; i o The symbol on the right represents i o The direction of the current; i g The symbol on the right represents i g The direction of current.

[0050] Example 1

[0051] The fault ride-through control method provided in the embodiment of the present application can be used in the process of solar photovoltaic power generation. The fault ride-through control method can be executed by a fault ride-through control device and a grid-connected inverter, etc. The following takes the execution of the fault ride-through control method by a grid-connected inverter as an example for explanation.

[0052] like Figure 2 As shown, the fault ride-through control method provided in the embodiment of the present application may include steps S110 to S140.

[0053] S110, obtaining an output voltage phase angle and a first control signal of the grid-connected inverter, where the first control signal is used to adjust the reactive power output of the grid-connected inverter.

[0054] S120. Determine a reset signal according to a preset voltage ride-through signal and a current limiting signal, where the reset signal is used to determine whether to reset an integral link of a reactive loop of the grid-connected inverter.

[0055] S130. Determine a reactive voltage reference corresponding to the first control signal according to a preset voltage ride-through signal and a reset signal.

[0056] S140, generating a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference to control the fault ride-through of the grid-connected inverter, wherein the target pulse width modulation signal is used to control the on and off of the power device.

[0057] According to the fault ride-through control method provided in the embodiment of the present application, a reset signal is determined according to a preset voltage ride-through signal and a current limiting signal to determine whether to reset the integral link of the reactive loop of the grid-connected inverter, which is beneficial to resetting the integral link of the reactive loop after the fault is cleared, thereby improving or eliminating the hysteresis existing in switching from the fault state to the normal working state, thereby improving or eliminating the deviation voltage caused by the hysteresis to improve the stability of the power system; according to the preset voltage ride-through signal and the reset signal, a reactive voltage reference corresponding to the first control signal is determined, and according to the output voltage phase angle and the reactive voltage reference, a target pulse width modulation signal is generated, that is, during the fault ride-through period, the grid-connected inverter can control the on and off of the power device through the target pulse width modulation signal, adjust the phase angle and reactive power, so as to ensure the phase synchronization between the grid-connected inverter and the power grid, so as to realize the fault ride-through control of the grid-connected inverter.

[0058] The specific implementation methods of the above steps are introduced below.

[0059] In step S110, the grid-connected inverter may be any inverter that needs to perform fault ride-through control.

[0060] In some examples, such as Figure 3 As shown, obtaining the first control signal may include: obtaining reactive power Q, reactive power reference Q ref and reactive power droop coefficient D q , the reactive power reference Q ref The difference between the reactive power Q and the reactive power droop coefficient D q The product of is determined as the first control signal. That is, the first control signal is (Q ref -Q)*D q Among them, reactive power Q, reactive power reference Q ref and reactive power droop coefficient D q All of them can be stored in the grid-connected inverter in advance for subsequent direct call.

[0061] In other examples, the first control signal may be pre-stored in the grid-connected inverter for subsequent direct call.

[0062] In some implementations, obtaining the output voltage phase angle of the grid-connected inverter includes:

[0063] Get the active power and active power reference of the grid-connected inverter;

[0064] determining a difference between the active power reference and the active power as an active power deviation;

[0065] When the preset voltage ride-through signal is at a first level, determining a target active power according to the active power deviation;

[0066] According to the target active power, the target angular frequency is determined;

[0067] According to the target angular frequency, the output voltage phase angle of the grid-connected inverter is determined.

[0068] In this implementation, the target active power is determined according to the active power deviation, providing a basis for improving the current limiting capability during a fault.

[0069] Exemplarily, the preset voltage ride-through signal may be a low voltage ride-through signal (LVRT). The low voltage ride-through signal may be an energy that enables the grid-connected inverter to continue to operate normally and maintain output power when a short-term low voltage fault occurs in the power grid. The low voltage in the low voltage ride-through signal may be 50% to 80% of the rated voltage.

[0070] Exemplarily, the first level may be an enable level of a preset voltage crossing signal, and the second level hereinafter may be a non-enable signal of the preset voltage crossing signal. In the embodiment of the present application, the first level is a high level and the second level is a low level as an example. Of course, in other embodiments, the first level may also be a low level and the second level may also be a high level.

[0071] For example, Figure 3 As shown, the active power reference P ref The difference between the active power P and the active power P is determined as the active power deviation ΔP; when the preset voltage crossing signal is at the first level, that is, when the enable level of the preset voltage crossing signal is detected, the target active power ΔP′ is determined according to the active power deviation ΔP; the target active power ΔP′, the active damping coefficient D, the virtual inertia J, and the grid voltage angular frequency ω are converted into the target active power ΔP′. ref Substitute the operation factor s into formula (4) to calculate the target angular frequency ω; integrate the target angular frequency ω to obtain the output voltage phase angle θ of the grid-connected inverter. Wherein, formula (4) includes:

[0072] Exemplarily, the active power reference, active power, operation factor, grid voltage angular frequency, active damping coefficient, and virtual inertia can all be pre-stored in the electronic device for subsequent direct call.

[0073] It should be noted that, when the preset voltage ride-through signal is at the second level, the output voltage of the grid-connected inverter is the preset reference voltage V ref .

[0074] In some examples, determining the target active power according to the active power deviation includes:

[0075] When the active power deviation is greater than the deviation threshold, determining the target active power as the deviation threshold;

[0076] or,

[0077] When the active power deviation is less than or equal to the deviation threshold, the target active power is determined to be the active power deviation.

[0078] In this example, when the enable level of the low voltage crossing signal is detected and the active power deviation is greater than the deviation threshold, the target active power is determined to be the deviation threshold, that is, the active power deviation is limited to the deviation threshold to control the power deviation saturation and prevent the problem of continuous imbalance between active power input and output.

[0079] For example, the value of the deviation threshold can be set according to actual conditions and is not limited here. For example, the deviation threshold can be 0.04 pu. This means that the deviation threshold can be pre-set in the grid-connected inverter for subsequent direct call.

[0080] That is, the target active power ΔP′ satisfies formula (5), which includes:

[0081]

[0082] Among them, ΔP max Indicates the deviation threshold.

[0083] In step S120, after acquiring the output voltage phase angle of the grid-connected inverter and the first control signal, the grid-connected inverter may also determine a reset signal according to a preset voltage ride-through signal and a current limiting signal.

[0084] Exemplarily, the current saturation algorithm (CSA) may be a signal used for current detection and limiting. The first level is an enable level of the current limiting signal, and the second level is a disable signal of the current limiting signal.

[0085] Exemplarily, the reset signal is used to determine whether to reset the integral link of the reactive loop of the grid-connected inverter. The first level is a non-enable level of the reset signal, and the second level is an enable level of the reset signal.

[0086] In some implementations, determining a reset signal according to a preset voltage ride-through signal and a current limiting signal includes:

[0087] When the preset voltage crossing signal is at a first level and the current limiting signal is at a first level, determining that the reset signal is at a second level, wherein the first level is opposite to the second level;

[0088] or,

[0089] When the preset voltage crossing signal is at the second level and the current limiting signal is at the first level, determining that the reset signal is at the first level;

[0090] or,

[0091] When the preset voltage crossing signal is at the first level and the current limiting signal is at the second level, determining that the reset signal is at the first level;

[0092] or,

[0093] When the preset voltage crossing signal is at the second level and the current limiting signal is at the second level, it is determined that the reset signal is at the second level.

[0094] That is, when the preset voltage crossing signal and the current limiting signal are at the same level, the reset signal is determined to be at the second level, and when the preset voltage crossing signal and the current limiting signal are at different levels, the reset signal is determined to be at the first level.

[0095] Exemplarily, when the reset signal is at the first level, the grid-connected inverter can be considered to be in a non-fault recovery stage, at which time the integral link is no longer enabled, that is, the input of the integral link is "0"; when the reset signal is at the second level, the grid-connected inverter can be considered to be in a fault recovery stage, at which time the output of the integral link needs to be reset.

[0096] For example, Figure 3 As shown in FIG. 1 , when the low voltage ride-through signal LVRT is at a high level 1 and the current limiting signal CSA is at a high level 1, the reactive power droop coefficient D q Connected to Y, the reset signal reset is low level 0; when the low voltage ride-through signal LVRT is low level 0 and the current limiting signal CSA is high level 1, the reactive droop coefficient D q Connected to N, the reset signal reset is high level 1; when the low voltage ride-through signal LVRT is high level 1 and the current limiting signal CSA is low level 0, the reactive droop coefficient D q Connected to N, the reset signal reset is high level 1; when the low voltage ride-through signal LVRT is low level 0, and the current limiting signal CSA is low level 0, the reactive droop coefficient D q Connected to N, the reset signal reset is low level 0.

[0097] In some embodiments, before determining the reset signal according to the preset voltage ride-through signal and the current limiting signal, the method further includes:

[0098] The d-axis voltage V at the common connection point od , q-axis voltage V oq and preset reference voltage V ref When formula (2) is satisfied and a delay link is passed, a preset voltage ride-through signal is triggered;

[0099] Formula (2) includes:

[0100]

[0101] After the preset voltage crossing signal is triggered, a reset signal is triggered after a delay period.

[0102] or,

[0103] On the grid side, the d-axis current I gd , grid-side q-axis current I gq and the current threshold I M When the formula (3) is satisfied, the current limiting signal is triggered;

[0104] Formula (3) includes:

[0105]

[0106] In this embodiment, by triggering a preset voltage crossing signal, or triggering a current limiting signal, a basis is provided for subsequent determination of a reset signal; triggering the reset signal provides a basis for subsequent determination of a reactive voltage reference corresponding to the first control signal.

[0107] For example, the current threshold I M It can be determined based on the inverter type, rated capacity, and fault type, or it can be set based on experience, and is not limited here. M The value can be 1.2A, 1.3A, etc.

[0108] For example, Figure 4 As shown, when the line voltage is When the grid-side current is , the CSA signal is triggered.

[0109] In step S130, after determining the reset signal according to the preset voltage ride-through signal and the current limiting signal, the grid-connected inverter may also determine a reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal.

[0110] In some implementations, determining a reactive voltage reference corresponding to the first control signal according to a preset voltage ride-through signal and a reset signal includes:

[0111] When the preset voltage crossing signal is at a first level and the reset signal is at a second level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage, wherein the first level and the second level are opposite;

[0112] or,

[0113] When the preset voltage crossing signal is at the second level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is the preset reference voltage;

[0114] or,

[0115] When the preset voltage crossing signal is at the first level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage;

[0116] or,

[0117] When the preset voltage crossing signal is at the second level and the reset signal is at the second level, the reactive voltage reference corresponding to the first control signal is determined to be a first value, which is the sum of the integral of the first control signal and the preset reference voltage.

[0118] In this embodiment, when the reset signal is at the second level, it can be considered that the grid-connected inverter is in the fault recovery stage, and therefore the output of the integral link needs to be reset; the reactive voltage reference corresponding to the first control signal is a preset reference voltage, that is, the reactive loop output is a constant voltage (that is, the preset reference voltage), which is conducive to fault recovery to prevent the access of the integral link from causing oscillations in the system power; the integral link is delayed after the fault is cleared, and when the preset voltage crossing signal is at the first level or the reset signal is at the second level, that is, when the preset voltage crossing signal or the reset signal is entered, the integral link cuts off the reactive loop; when the preset voltage crossing signal is at the second level and the reset signal is at the first level, that is, when the preset voltage crossing signal and the reset signal are exited, the integral link is cut into the reactive loop.

[0119] For example, Figure 3 As shown, when the low voltage ride-through signal LVRT is at a high level 1 and the reset signal is at a low level 0, 1 / s is connected to "1" to determine the reactive voltage reference E corresponding to the first control signal. ref The preset reference voltage V ref When the low voltage ride-through signal LVRT is low level 0 and the reset signal is high level 1, 1 / s is connected to "1" to determine the reactive voltage reference E corresponding to the first control signal ref The preset reference voltage Vref When the low voltage ride-through signal LVRT is high level 1 and the reset signal is low level 0, 1 / s is connected to "1" to determine the reactive voltage reference E corresponding to the first control signal ref The preset reference voltage V ref When the low voltage ride-through signal LVRT is low level 0 and the reset signal is low level 0, 1 / s is connected to "0" to determine the reactive voltage reference E corresponding to the first control signal ref It is the first value Vref+Dq(Q-Qref) / s.

[0120] That is, when the low voltage ride-through signal and the reset signal are both at the first level, the reactive voltage reference E corresponding to the first control signal is determined. ref is the first value Vref+Dq(Q-Qref) / s; in other cases, the reactive voltage reference E corresponding to the first control signal is determined ref The preset reference voltage V ref .

[0121] In S140, after determining the reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal, the grid-connected inverter may also generate a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference.

[0122] It should be noted that the fault-crossing strategy in the prior art controls the on-off of power devices and generates a deviation voltage. The embodiment of the present application controls the on-off of power devices by resetting the integral link of the reactive loop of the grid-connected inverter through the fault-crossing strategy to eliminate the deviation voltage.

[0123] In some implementations, generating a target pulse width modulation signal according to an output voltage phase angle and a reactive voltage reference includes:

[0124] Obtaining the grid-side d-axis current, the grid-side q-axis current, the d-axis voltage and the q-axis voltage of the common connection point;

[0125] Determine the d-axis voltage reference and the q-axis voltage reference of the voltage outer loop according to the output voltage phase angle and the reactive voltage reference;

[0126] Determine a d-axis current reference and a q-axis current reference of the current inner loop according to the grid-side d-axis current, the grid-side q-axis current, the d-axis voltage, the q-axis voltage, the d-axis voltage reference and the q-axis voltage reference;

[0127] Determine a target d-axis current reference and a target q-axis current reference according to the d-axis current reference and the q-axis current reference;

[0128] determining a d-axis voltage modulation and a q-axis voltage modulation of a modulation wave according to a target d-axis current reference and a target q-axis current reference;

[0129] According to the q-axis voltage modulation and the q-axis voltage modulation, a target pulse width modulation signal is generated.

[0130] In this implementation, a target d-axis current reference and a target q-axis current reference are determined according to the d-axis current reference and the q-axis current reference, thereby providing a possibility for limiting overcurrent generated during a fault of the grid-connected inverter.

[0131] Exemplarily, the point of common connection (PCC) may be a connection point between the grid-tied inverter and the grid.

[0132] For example, Figure 5 As shown, the output voltage phase angle θ and reactive voltage reference E ref Voltage synthesis may include: combining the output voltage phase angle θ and the reactive voltage reference E ref Substitute into formula (6) to calculate and obtain the d-axis voltage reference V odref and q-axis voltage reference V oqref ; Formula (6) includes: Figure 3 V * Represents the d-axis voltage reference V odref and q-axis voltage reference V oqref The resultant voltage.

[0133] It should be noted that according to the grid-side d-axis current I gd (i.e., i in the above text g d-axis component after Park transformation), grid-side q-axis current I gq (i.e., i in the above text g q-axis component after Park transformation), d-axis voltage V od (That is, v in the above text o d-axis component after Park transformation), q-axis voltage V oq (That is, v in the above text o The q-axis component after Park transformation), the d-axis voltage reference V odref (i.e., the d-axis reference of the voltage outer loop mentioned above) and the q-axis voltage reference V oqref (i.e., the q-axis reference of the voltage outer loop mentioned above), determines the d-axis current reference I of the current inner loop odref (i.e., the d-axis reference of the current inner loop mentioned above) and the q-axis current reference I oqref (i.e., the q-axis reference of the current inner loop in the above text) is the prior art, i.e. Figure 3 The voltage and current double closed loop in the circuit will not be elaborated here.

[0134] In some examples, determining a target d-axis current reference and a target q-axis current reference according to a d-axis current reference and a q-axis current reference includes:

[0135] Determine a target d-axis current reference and a target q-axis current reference based on the d-axis current reference, the q-axis current reference and formula (1);

[0136] Formula (1) includes:

[0137]

[0138] Among them, i ref ' represents the target d-axis current reference or the target q-axis current reference; i ref Indicates the d-axis current reference or the q-axis current reference; I M represents the current threshold; φ represents the current phase angle; j represents the imaginary inertia.

[0139] In this example, by limiting the target d-axis current reference and the target q-axis current reference to a current threshold, or within the current threshold, the current limiting capability of the grid-connected inverter during a fault can be improved, thereby facilitating the stability of the power system.

[0140] For example, Figure 5 As shown, the current limiter may be a priority current limiter. More specifically, the current limiter may be a d-axis priority current limiter, so φ = 0. Of course, other types of current limiters may also be used, which are not limited here.

[0141] Please note that Figure 1 and Figure 5 The difference between the embodiment of the present application and the traditional network control strategy is that: in order to improve the comprehensive fault ride-through capability, the embodiment of the present application adds power deviation saturation control to the active loop and adds a reset link to the reactive loop. Figure 3 As shown in Figure 1, a current limiter is added to improve the current limiting capability during a fault. In other words, Figure 5 The part in the middle gray box is the difference between the embodiment of the present application and the prior art.

[0142] It is understandable that the inventors have discovered through research that in the prior art, there is no step for resetting the integral link of the reactive loop after the fault is cleared, resulting in a lag in switching from the fault state to the normal working state, and then resulting in a deviation voltage, which leads to poor stability of the power system; while the embodiment of the present application improves or eliminates the lag in switching from the fault state to the normal working state by adding the step of resetting the integral link of the reactive loop, and then improves or eliminates the deviation voltage, thereby improving the stability of the power system.

[0143] In some more specific implementations, the reactive power reference Q ref is 100kVAR, reactive power Q is 70kVAR, reactive power droop coefficient D q is 0.1, then the first control signal (Qref -Q)*D q =3kVAR; active power reference P ref is 0.1 pu, and the active power P is 0.08 pu, then the active power deviation ΔP in step S110 is 0.02 pu; ΔP max is 0.04pu, then according to formula (5) in step S110, the target active power ΔP′ is determined to be 0.02pu; the active damping coefficient D is 0.1, the virtual inertia J is 5s, and the operation factor s is 1; when the low voltage ride-through signal is high level 1, the target angular frequency ω is calculated using formula (4) in step S110 to be 0.0025rad / s; t=1s, then the output voltage phase angle θ of the grid-connected inverter in step S110 is 0.0025rad. Figure 3 As shown, the preset reference voltage V ref is 2V. In step S120, when the low voltage ride-through signal LVRT is at a high level 1 and the current limiting signal CSA is at a high level 1, the reactive power droop coefficient D q Connected to Y, at this time the reset signal reset is low level 0; in step S130, when the low voltage ride-through signal LVRT is high level 1 and the reset signal is low level 0, 1 / s is connected to "1" to determine the reactive voltage reference E corresponding to the first control signal ref is 2V; in step S140, according to the reactive voltage reference E ref A target pulse width modulation signal is generated for 2V and the output voltage phase angle θ of the grid-connected inverter is 0.0025rad to achieve fault ride-through control of the grid-connected inverter.

[0144] It should be noted that the inventors have found that the current current limiting strategies mainly include current limiters, virtual impedances and voltage limiters. Among them, the current limiter can limit the current better, but the recovery ability is poor after the fault is cleared; the virtual impedance has excellent recovery ability after the fault is cleared, but there will be a short-term overcurrent, and the fault current depends on the virtual impedance parameters and the grid parameters; the voltage limiter has excellent recovery ability after the fault is cleared, but there will be a short-term overcurrent, and the fault current depends on the voltage limiter parameters and the grid parameters.

[0145] Based on this, the comprehensive fault ride-through strategy based on reactive ring reset in the fault ride-through control method provided in the embodiment of the present application is summarized as follows: Figure 6As shown. The embodiment of the present application improves the fault ride-through capability of the inverter on the basis of the classic VSG control architecture: first, the power deviation saturation position control is used to limit the power deviation during the fault to within a given threshold to prevent power angle instability; a priority current limiter is used to limit the overcurrent generated during the fault process; and an anti-saturation link is added to the reactive loop to prevent saturation of the integral link. The fault recovery capability of the inverter is improved: the integral link of the reactive loop is reset after the fault is cleared to eliminate the deviation voltage caused by the lag in switching from the fault state to the normal working state; during the fault and fault recovery process, the reactive loop is output as a constant voltage to prevent the access of the integral link from causing oscillation of the system power. In summary, the embodiment of the present application can solve the following problems to be solved: 1. Power angle instability; 2. Fault overcurrent; 3. Saturation of the integral link; 4. Deviation voltage; 5. Oscillation of the access of the integral link.

[0146] It should be noted that the fault ride-through control method provided in the embodiment of the present application can significantly improve the transient stability of the inverter compared with the existing network fault ride-through strategy, and is only implemented at the power control algorithm level. The solution is simple and does not require additional sensors or controllers, saving production costs. Compared with the existing network fault recovery strategy, the embodiment of the present application focuses on the interaction between the reactive loop and the voltage and current inner loop, and can quickly and stably exit the current limiting state. Moreover, the proposed strategy only uses the most basic logical judgment and loop switching, and the control strategy is simple and effective, with strong feasibility.

[0147] In order to verify the effectiveness and superiority of the proposed strategy, a corresponding simulation model was built in matlab / simulink, and the fault ride-through characteristics with and without the control strategy proposed in the embodiment of the present application were compared. Table 1 shows the simulink simulation parameters.

[0148] Table 1

[0149] parameter Numeric DC side voltage 1350V Grid-side voltage effective value 461.74V <![CDATA[P ref ]]> 330kW <![CDATA[Q ref ]]> 0kvar Grid side inductor 0.617mH(0.1pu) Grid side resistance 0.0019Ω(0.01pu) Reactive power integral coefficient 200*6.53e-5 Switching frequency 16000Hz J 40.12 D 797.71

[0150] It should be noted that the above numerical values ​​are only used for simulation examples and are not intended to limit the present application.

[0151] Figure 7 is the simulation result of active power and reactive power in the prior art, such as Figure 7 As shown in the figure, before t = 1.8s, it is in normal working state; at t = 1.8s, the grid voltage drops to 0.2pu. According to the relevant standards of the State Grid, the fault duration is 625ms. It can be seen that when the fault ride-through control method in the prior art is used, there will be a large reactive overshoot at the beginning of the fault, and a large active overshoot after the fault is cleared.

[0152] Figure 8 is the simulation result of active power and reactive power provided by the embodiment of the present application. Figure 8 As shown, before t = 1.8s, it is in normal working state; at t = 1.8s, the grid voltage drops to 0.2pu. According to the relevant standards of the State Grid, the fault duration is 625ms. It can be seen that by adopting the fault ride-through control method provided in the embodiment of the present application, a short current limiting state is entered after the fault is cleared, but the reactive loop output is a constant voltage, so that the current limiting state is switched to a normal working state.

[0153] Fig. 9 It is a schematic diagram of a simulation result of the grid-side current in the prior art. Fig.10 It can be seen that there will be a large current shock when a fault occurs and is cleared, which seriously endangers the stable and safe operation of the inverter.

[0154] Fig.10 Schematic diagram of a simulation result of the grid-side current provided in the embodiment of the present application. Fig.11 As shown in the figure, current limiting can be achieved during the fault process, and there is no current overshoot after the fault ends, thus achieving smooth mode switching.

[0155] Fig.11 is the phase plane diagram in the prior art, Fig.12 It is a schematic diagram of the power angle curve in the prior art. Fig.11 and Fig.12 It can be seen that although the fault ride-through control method in the prior art can return to the working point before the fault after the fault is cleared, the overshoot of active power has far exceeded the capacity of the inverter, which is easy to cause safety accidents such as disconnection from the grid.

[0156] Fig.13 is a phase plane diagram provided in the embodiment of the present application, Fig.14 Schematic diagram of the power angle curve provided in the embodiment of the present application. Fig.13 and Fig.14 It can be seen that the fault ride-through control method provided in the embodiment of the present application can stably operate during the fault process and can stably return to the working point before the fault after the fault is cleared.

[0157] in, Figure 7 and Figure 8 The horizontal axis is time, the unit is s, and the vertical axis is power, the unit is pu; Fig. 9 and Fig.10 The horizontal axis is time, the unit is s, and the vertical axis is current, the unit is A; Fig.11 and Fig.12 The horizontal axis is the phase angle, the unit is rad; the vertical axis is the angular velocity, the unit is rad / s; Fig.13 and Fig.14 The horizontal axis is the phase angle, the unit is rad, and the vertical axis is the power, the unit is pu. Fig. 9 and Fig.10 Iabc in represents three-phase current;

[0158] Example 2

[0159] like Fig.15 As shown, the fault ride-through control device provided by the embodiment of the present application may include a first acquisition module 210, a first determination module 220, a second determination module 230 and a first generation module 240. Among them, the first acquisition module 210 is used to acquire the output voltage phase angle and the first control signal of the grid-connected inverter, and the first control signal is used to adjust the reactive power output of the grid-connected inverter; the first determination module 220 is connected to the first acquisition module 210, and is used to determine the reset signal according to the preset voltage ride-through signal and the current limiting signal, and the reset signal is used to determine whether to reset the integral link of the reactive loop of the grid-connected inverter; the second determination module 230 is connected to the first determination module 220, and is used to determine the reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal; the first generation module 240 is connected to the second determination module 230, and is used to generate a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference, so as to realize the fault ride-through control of the grid-connected inverter, and the target pulse width modulation signal is used to control the on and off of the power device.

[0160] In some embodiments, the first determination module 220 is specifically used to: determine that the reset signal is a second level when the preset voltage crossing signal is a first level and the current limiting signal is a first level, wherein the first level is opposite to the second level; or, determine that the reset signal is a first level when the preset voltage crossing signal is a second level and the current limiting signal is a first level; or, determine that the reset signal is a first level when the preset voltage crossing signal is a first level and the current limiting signal is a second level; or, determine that the reset signal is a second level when the preset voltage crossing signal is a second level and the current limiting signal is a second level.

[0161] In some embodiments, the second determination module 230 is specifically used to: when the preset voltage crossing signal is the first level and the reset signal is the second level, determine that the reactive voltage reference corresponding to the first control signal is the preset reference voltage, wherein the first level and the second level are opposite; or, when the preset voltage crossing signal is the second level and the reset signal is the first level, determine that the reactive voltage reference corresponding to the first control signal is the preset reference voltage; or, when the preset voltage crossing signal is the first level and the reset signal is the first level, determine that the reactive voltage reference corresponding to the first control signal is the preset reference voltage; or, when the preset voltage crossing signal is the second level and the reset signal is the second level, determine that the reactive voltage reference corresponding to the first control signal is the first value, and the first value is the sum of the integral of the first control signal and the preset reference voltage.

[0162] In some embodiments, the first acquisition module 210 is specifically used to: obtain the active power and active power reference of the grid-connected inverter; determine the difference between the active power reference and the active power as the active power deviation; determine the target active power according to the active power deviation when the preset voltage crossing signal is at the first level; determine the target angular frequency according to the target active power; and determine the output voltage phase angle of the grid-connected inverter according to the target angular frequency.

[0163] The fault-crossing control device provided in the embodiment of the present application can be used to execute the fault-crossing control method, that is, it has the beneficial effects and implementation methods of the fault-crossing control method provided in Example 1 of the present application. For details, please refer to the specific description of the fault-crossing control method in the above Example 1, which will not be repeated in this embodiment.

[0164] Example 3

[0165] An embodiment of the present application also provides a grid-connected inverter, comprising a grid-connected inverter body and the fault ride-through control device of any one of Embodiment 2.

[0166] The grid-connected inverter provided in the embodiment of the present application includes the fault-crossing control device of any one of Embodiment 2, that is, it has the beneficial effects and implementation methods of the fault-crossing control device provided in Embodiment 2 of the present application. For details, please refer to the specific description of the fault-crossing control device in the above Embodiment 2, which will not be repeated in this embodiment.

[0167] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present application, but the present application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of the present application, and these modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A fault ride-through control method, characterized in that: include: Acquire an output voltage phase angle of the grid-connected inverter and a first control signal, wherein the first control signal is used to adjust the reactive power output of the grid-connected inverter; Determine a reset signal according to a preset voltage ride-through signal and a current limiting signal, wherein the reset signal is used to determine whether to reset an integral link of a reactive loop of a grid-connected inverter; Determining a reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal; A target pulse width modulation signal is generated according to the output voltage phase angle and the reactive voltage reference to control the fault ride-through of the grid-connected inverter, and the target pulse width modulation signal is used to control the on and off of power devices.

2. The method according to claim 1, characterized in that The step of determining a reset signal according to a preset voltage ride-through signal and a current limiting signal includes: When the preset voltage crossing signal is at a first level and the current limiting signal is at the first level, determining that the reset signal is at a second level, wherein the first level is opposite to the second level; or, When the preset voltage crossing signal is at the second level and the current limiting signal is at the first level, determining that the reset signal is at the first level; or, When the preset voltage crossing signal is at a first level and the current limiting signal is at a second level, determining that the reset signal is at the first level; or, When the preset voltage crossing signal is at the second level and the current limiting signal is at the second level, it is determined that the reset signal is at the second level.

3. The method according to claim 1, characterized in that The determining, according to the preset voltage ride-through signal and the reset signal, a reactive voltage reference corresponding to the first control signal comprises: When the preset voltage crossing signal is at a first level and the reset signal is at a second level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage, wherein the first level is opposite to the second level; or, When the preset voltage crossing signal is at the second level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage; or, When the preset voltage crossing signal is at a first level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage; or, When the preset voltage crossing signal is at the second level and the reset signal is at the second level, the reactive voltage reference corresponding to the first control signal is determined to be a first value, which is the sum of the integral of the first control signal and the preset reference voltage.

4. The method according to claim 1, characterized in that: The obtaining of the output voltage phase angle of the grid-connected inverter comprises: Get the active power and active power reference of the grid-connected inverter; Determining a difference between the active power reference and the active power as an active power deviation; When the preset voltage ride-through signal is at a first level, determining a target active power according to the active power deviation; Determining a target angular frequency according to the target active power; The output voltage phase angle of the grid-connected inverter is determined according to the target angular frequency.

5. The method according to claim 4, characterized in that Determining the target active power according to the active power deviation includes: When the active power deviation is greater than the deviation threshold, determining the target active power to be the deviation threshold; or, When the active power deviation is less than or equal to the deviation threshold, the target active power is determined to be the active power deviation.

6. The method according to claim 1, characterized in that The step of generating a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference comprises: Obtaining the grid-side d-axis current, the grid-side q-axis current, the d-axis voltage and the q-axis voltage of the common connection point; Determine a d-axis voltage reference and a q-axis voltage reference of a voltage outer loop according to the output voltage phase angle and the reactive voltage reference; Determine a d-axis current reference and a q-axis current reference of a current inner loop according to the grid-side d-axis current, the grid-side q-axis current, the d-axis voltage, the q-axis voltage, the d-axis voltage reference, and the q-axis voltage reference; Determining a target d-axis current reference and a target q-axis current reference according to the d-axis current reference and the q-axis current reference; Determining a q-axis modulation voltage and a q-axis modulation voltage of a modulation wave according to the target d-axis current reference and the target q-axis current reference; A target pulse width modulation signal is generated according to the q-axis modulation voltage and the q-axis modulation voltage.

7. The method according to claim 6, characterized in that The determining a target d-axis current reference and a target q-axis current reference according to the d-axis current reference and the q-axis current reference comprises: Determine a target d-axis current reference and a target q-axis current reference based on the d-axis current reference, the q-axis current reference and formula (1); The formula (1) includes: Among them, i ref ' represents the target d-axis current reference or the target q-axis current reference; i ref Indicates the d-axis current reference or the q-axis current reference; I M represents the current threshold; φ represents the current phase angle; j represents the imaginary inertia.

8. The method according to claim 1, characterized in that Before determining the reset signal according to the preset voltage ride-through signal and the current limiting signal, the method further includes: The d-axis voltage V at the common connection point od , q-axis voltage V oq and preset reference voltage V ref When formula (2) is satisfied and a delay link is passed, a preset voltage ride-through signal is triggered; The formula (2) includes: After the preset voltage crossing signal is triggered, a reset signal is triggered after a delay period. or, On the grid side, the d-axis current I gd , grid-side q-axis current I gq and the current threshold I M When the formula (3) is satisfied, the current limiting signal is triggered; The formula (3) includes:

9. A fault ride-through control device, characterized in that: include: A first acquisition module, used for acquiring an output voltage phase angle of the grid-connected inverter and a first control signal, wherein the first control signal is used for adjusting the reactive power output of the grid-connected inverter; A first determination module, connected to the first acquisition module, is used to determine a reset signal according to a preset voltage ride-through signal and a current limiting signal, wherein the reset signal is used to determine whether to reset an integral link of a reactive loop of a grid-connected inverter; a second determination module, connected to the first determination module, and configured to determine a reactive voltage reference corresponding to the first control signal according to the preset voltage ride-through signal and the reset signal; The first generating module is connected to the second determining module and is used to generate a target pulse width modulation signal according to the output voltage phase angle and the reactive voltage reference to control the fault ride-through of the grid-connected inverter, wherein the target pulse width modulation signal is used to control the on and off of the power device.

10. The device according to claim 9, characterized in that The first determining module is specifically configured to: When the preset voltage crossing signal is at a first level and the current limiting signal is at the first level, determining that the reset signal is at a second level, wherein the first level is opposite to the second level; or, When the preset voltage crossing signal is at the second level and the current limiting signal is at the first level, determining that the reset signal is at the first level; or, When the preset voltage crossing signal is at a first level and the current limiting signal is at a second level, determining that the reset signal is at the first level; or, When the preset voltage crossing signal is at the second level and the current limiting signal is at the second level, determining that the reset signal is at the second level; and / or, The second determining module is specifically used to: When the preset voltage crossing signal is at a first level and the reset signal is at a second level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage, wherein the first level is opposite to the second level; or, When the preset voltage crossing signal is at the second level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage; or, When the preset voltage crossing signal is at a first level and the reset signal is at the first level, determining that the reactive voltage reference corresponding to the first control signal is a preset reference voltage; or, When the preset voltage crossing signal is at a second level and the reset signal is at the second level, determining that the reactive voltage reference corresponding to the first control signal is a first value, the first value being a sum of an integral of the first control signal and a preset reference voltage; and / or, The first acquisition module is specifically used to: Get the active power and active power reference of the grid-connected inverter; Determining a difference between the active power reference and the active power as an active power deviation; When the preset voltage ride-through signal is at a first level, determining a target active power according to the active power deviation; Determining a target angular frequency according to the target active power; The output voltage phase angle of the grid-connected inverter is determined according to the target angular frequency.

11. A grid-connected inverter, comprising a grid-connected inverter body, characterized in that: It also includes the fault ride-through control device as described in claim 9 or 10.

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