Fault ride-through method of inverter and related equipment

Abstract

The embodiment of the invention discloses a fault ride-through method of an inverter and related equipment, and the method comprises the steps: constructing a grid-connected system fault equivalent model through a first amplitude and a first phase angle, a second amplitude and a second phase angle, and the total resistance and total inductance of a filtering loop between the inverter and a power grid; based on the grid-connected system fault equivalent model, the third amplitude, the third phase angle, the first impedance angle and the second impedance angle, a third output voltage during the inverter fault period is obtained, and a second active power of the inverter is obtained by using the third output voltage and a first active power output by the inverter under a normal condition; and the inverter is controlled by using the third output voltage and the second active power, so that the inverter is controlled by using the third output voltage and the second active power during low-voltage ride-through, the coupling problem of the active power and the reactive power is reduced, and the stability of inverter fault ride-through is enhanced. And the power grid can be ensured to obtain enough reactive power support under the low-voltage condition.

Description

[Technical field]

[0001] The present invention relates to the technical field of inverter fault ride-through, and in particular to an inverter fault ride-through method and related equipment. [Background technology]

[0002] As the proportion of renewable energy in the power system increases, the stability of traditional power grids faces new challenges. Renewable energy grid-connected inverters usually lack the rotational inertia of traditional synchronous generators, which makes it difficult for the power grid to remain stable when frequency fluctuations and short-circuit faults occur. When the grid voltage fluctuates downward, the traditional low-voltage ride-through strategy is not fully applicable to power systems with a high proportion of renewable energy. In particular, when the impact of short-circuit current is ignored, the inverter may not be able to continue to connect to the grid under low-voltage conditions, which will not only lead to unstable power supply, but also trigger a series of chain reactions, exacerbating the volatility and instability of the power grid.

[0003] Virtual synchronous machine (VSG) control technology is introduced to compensate for the lack of rotational inertia of renewable energy grid-connected inverters, and enhances the stability of the grid by simulating the inertia and damping characteristics of traditional synchronous generators. However, during the inverter low voltage ride-through, the operating conditions of the inverter become more complicated, especially when the short-circuit current has an impact on the grid. Traditional VSG control strategies may not be able to fully cope with these complex situations, making it difficult to maintain the grid frequency and voltage within a stable range. [Summary of the invention]

[0004] In view of this, the present invention provides a fault ride-through method for an inverter and related equipment.

[0005] The specific technical scheme of the first embodiment of the present invention is: a fault ride-through method of an inverter, applied to a power system, the method comprising: using the first amplitude and first phase angle of the first output voltage of the inverter, the second amplitude and second phase angle of the second output voltage of the power grid in the power system, and the total resistance and total inductance of the filter loop between the inverter and the power grid to construct a grid-connected system fault equivalent model; based on the grid-connected system fault equivalent model, the third amplitude and third phase angle of the power grid output voltage after the fault occurs, obtaining a second impedance model between the inverter and the power grid after the fault occurs; bringing the first impedance angle of the inverter under normal circumstances and the second impedance angle of the inverter after the fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period; using the third output voltage and the first active power output by the inverter under normal circumstances to obtain the second active power of the inverter; using the third output voltage and the second active power to control the inverter.

[0006] Preferably, the grid-connected system fault equivalent model is obtained using the following formula:

[0007]

[0008] in, is the first output voltage, V i is the first amplitude, θ is the first phase angle, For the second output voltage, V g is the second amplitude, δ is the second phase angle, Z L is the total impedance, R i is the equivalent resistance between the inverter outlet and the grid connection point, L i is the equivalent inductance between the inverter outlet and the grid connection point, R linel is the equivalent resistance between the left side of the line and the fault point, L linel is the equivalent inductance between the left side of the line and the fault point, R liner is the resistance from the fault point to the right side of the line, L liner is the inductance from the fault point to the right side of the line, R L is the total resistance, L L is the total inductance, ω is the angular velocity of the power system, and t is the time of the power system.

[0009] Preferably, the second impedance model is obtained using the following formula:

[0010]

[0011] Among them, Z' L is the impedance between the inverter and the grid after a fault occurs, R' L is the total resistance between the inverter and the grid after a fault occurs, L' L is the total inductance between the inverter and the grid after a fault occurs, V i is the first amplitude, ω is the angular velocity of the power system, t is the time of the power system, V' g is the amplitude of the output voltage of the power grid in the power system after the fault occurs, and δ' is the phase angle of the output voltage of the power grid after the fault occurs or the phase angle of the output voltage of the power system after the fault occurs.

[0012] Preferably, the step of bringing the first impedance angle of the inverter under normal circumstances and the second impedance angle of the inverter after a fault occurs into the second impedance model to obtain the third output voltage during the inverter fault period includes: bringing the first impedance angle of the inverter under normal circumstances and the second impedance angle of the inverter after a fault occurs into the second impedance model to obtain an output current model during the inverter fault period; obtaining a first power angle of the power system under normal circumstances, and obtaining a second power angle of the power system after a fault occurs; and obtaining the third output voltage according to the output current model, the first power angle, and the second power angle.

[0013] Preferably, after obtaining the third output voltage during the inverter fault period, it also includes: optimizing the third output voltage using a preset per-unit value to obtain a reference output voltage value of the inverter; then using the third output voltage and the first active power output by the inverter under normal circumstances to obtain the second active power of the inverter includes: using the reference output voltage value and the first active power output by the inverter under normal circumstances to obtain the second active power of the inverter; using the third output voltage and the second active power to control the inverter includes: using the reference output voltage value and the second active power to control the inverter.

[0014] Preferably, the reference output voltage value is obtained using the following formula:

[0015]

[0016] Among them, V s is the reference output voltage value, V sn is the amplitude of the inverter output voltage under normal conditions, V i is the first amplitude, V g is the second amplitude, ω is the angular velocity of the power system, L L is the total inductance between the inverter outlet and the grid under normal conditions, I i is the output current amplitude of the inverter under normal conditions, V' g is the third amplitude, is the per unit value of the grid output voltage, and k is the preset coefficient.

[0017] Preferably, the second active power is obtained by using the following formula:

[0018]

[0019] Among them, P ref is the second active power, V sn is the amplitude of the inverter output voltage under normal conditions, V s is the reference output voltage value, P refn It is the active power output by the inverter under normal conditions.

[0020] The specific technical scheme of the second embodiment of the present invention is: a fault ride-through system of an inverter, the system comprising: a grid-connected system fault equivalent model construction module, a model conversion module, an output voltage acquisition module, an active power acquisition module and a control module; the grid-connected system fault equivalent model construction module is used to use the first amplitude and first phase angle of the first output voltage of the inverter, the second amplitude and second phase angle of the second output voltage of the power grid in the power system, and the total resistance and total inductance of the filter loop between the inverter and the power grid to construct a grid-connected system fault equivalent model; the grid-connected system fault equivalent model includes a first impedance model between the inverter and the power grid; the model conversion module is used to construct a grid-connected system fault equivalent model based on the first amplitude and first phase angle of the first output voltage of the inverter, the second amplitude and second phase angle of the second output voltage of the power grid in the power system, and the total resistance and total inductance of the filter loop between the inverter and the power grid. The second impedance model between the inverter and the grid after the fault occurs is obtained based on the grid-connected system fault equivalent model, the third amplitude and the third phase angle of the grid output voltage after the fault occurs; the output voltage acquisition module is used to bring the first impedance angle of the inverter under normal circumstances and the second impedance angle of the inverter after the fault occurs into the second impedance model to obtain the third output voltage during the inverter fault period; the active power acquisition module is used to use the third output voltage and the first active power output by the inverter under normal circumstances to obtain the second active power of the inverter; the control module is used to control the inverter using the third output voltage and the second active power.

[0021] The specific technical solution of the third embodiment of the present invention is: a fault-crossing device of an inverter, comprising a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method described in any one of the first embodiments of the present application.

[0022] The specific technical solution of the fourth embodiment of the present invention is: a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to perform the steps of the method described in any one of the first embodiments of the present application.

[0023] Implementing the embodiments of the present invention will have the following beneficial effects:

[0024] The present invention constructs a grid-connected system fault equivalent model through a first amplitude and a first phase angle, a second amplitude and a second phase angle, and a total resistance and a total inductance of a filter loop between an inverter and a power grid, and obtains a third output voltage during an inverter fault based on the grid-connected system fault equivalent model, a third amplitude and a third phase angle, a first impedance angle, and a second impedance angle, and obtains a second active power of the inverter by using the third output voltage and a first active power output by the inverter under normal conditions, and controls the inverter by using the third output voltage and the second active power, thereby reducing the coupling problem of active power and reactive power by controlling the inverter by using the third output voltage and the second active power during low voltage ride-through, thereby enhancing the stability of the inverter fault ride-through and ensuring that the power grid can obtain sufficient reactive support under low voltage conditions.

Brief Description of the Drawings

[0025] 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.

[0026] Figure 1 A flowchart of a fault ride-through method for an inverter;

[0027] Figure 2 It is a structural diagram of the fault equivalent model of the grid-connected system;

[0028] Figure 3 A flow chart of steps for obtaining a third output voltage;

[0029] Figure 4 A flow chart of steps for optimizing the third output voltage using the per-unit value;

[0030] Figure 5 It is a schematic diagram of the control strategy model of the grid-connected inverter;

[0031] Figure 6a is the output current of the inverter controlled by VSG during voltage sag;

[0032] Figure 6b The output current of the inverter controlled by the VSG using the low voltage ride-through of the present application during the voltage drop period;

[0033] Figure 6c is the output voltage of the inverter controlled by VSG during voltage sag;

[0034] Figure 6dThe output voltage of the inverter controlled by the VSG using the low voltage ride-through of the present application during the voltage drop period;

[0035] Figure 6e is the output power of the inverter controlled by VSG during voltage sag;

[0036] Figure 6f The output power of the inverter controlled by the VSG using the low voltage ride-through of the present application during the voltage drop period;

[0037] Figure 7 is a structural schematic diagram of a fault ride-through system of an inverter;

[0038] Among them, 401 is a grid-connected system fault equivalent model building module; 402 is a model conversion module; 403 is an output voltage acquisition module; 404 is an active power acquisition module; 405 is a control module. [Specific implementation method]

[0039] 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.

[0040] The terms "first", "second", etc. in the specification, claims and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but optionally includes steps or modules that are not listed, or optionally includes other steps or modules that are inherent to these processes, methods, products or devices.

[0041] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0042] See also Figure 1 , is a flowchart of a fault ride-through method of an inverter in the first embodiment of the present application, which ensures that the power grid can obtain sufficient reactive power support under low voltage conditions, and the method includes:

[0043] Step 101: construct a grid-connected system fault equivalent model using a first amplitude and a first phase angle of a first output voltage of an inverter, a second amplitude and a second phase angle of a second output voltage of a power grid in a power system, and a total resistance and a total inductance of a filter loop between the inverter and the power grid; the grid-connected system fault equivalent model includes a first impedance model between the inverter and the power grid;

[0044] Step 102: Based on the grid-connected system fault equivalent model, a third amplitude and a third phase angle of the grid output voltage after the fault occurs, obtain a second impedance model between the inverter and the grid after the fault occurs;

[0045] Step 103: Substitute the first impedance angle of the inverter in a normal situation and the second impedance angle of the inverter after the fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period;

[0046] Step 104: Obtain a second active power of the inverter by using the third output voltage and the first active power output by the inverter under normal conditions;

[0047] Step 105: Control the inverter using the third output voltage and the second active power.

[0048] For details, please refer to Figure 2 , the grid-connected system fault equivalent model includes: 1) the new energy on the left and its grid-connected inverter based on virtual synchronous generator control, whose output voltage and current vectors are 2) The vector of the output voltage and current of the right grid system power supply is 3) The equivalent resistance and inductance between the inverter outlet and the grid connection point PCC is R i , L i . 4) The internal resistance and inductance of the power supply of the power grid system are R g , L g 5) A fault occurs on the line between the grid connection point and the power system. The fault type is a short circuit fault. After the fault occurs, the resistance and inductance from the left side of the line to the fault point are R linel , L linel , the resistance and inductance from the fault point to the right side of the line are R liner , L liner .

[0049] The method in this embodiment constructs a grid-connected system fault equivalent model through the first amplitude and the first phase angle, the second amplitude and the second phase angle, the total resistance and the total inductance of the filter loop between the inverter and the power grid, and obtains the third output voltage during the inverter fault based on the grid-connected system fault equivalent model, the third amplitude and the third phase angle, the first impedance angle and the second impedance angle, and obtains the second active power of the inverter by using the third output voltage and the first active power output by the inverter under normal conditions, and controls the inverter by using the third output voltage and the second active power, so that when performing low voltage ride-through, the inverter is controlled by using the third output voltage and the second active power, reducing the coupling problem of active power and reactive power, thereby enhancing the stability of the inverter fault ride-through and ensuring that the power grid can obtain sufficient reactive support under low voltage conditions.

[0050] In a specific embodiment, the grid-connected system fault equivalent model is obtained using the following formula:

[0051]

[0052] in, is the first output voltage, V i is the first amplitude, θ is the first phase angle, For the second output voltage, V g is the second amplitude, δ is the second phase angle, Z L is the total impedance, R i is the equivalent resistance between the inverter outlet and the grid connection point, L i is the equivalent inductance between the inverter outlet and the grid connection point, R linel is the equivalent resistance between the left side of the line and the fault point, L linel is the equivalent inductance between the left side of the line and the fault point, R liner is the resistance from the fault point to the right side of the line, L liner is the inductance from the fault point to the right side of the line, R L is the total resistance, L L is the total inductance, ω is the angular velocity of the power system, and t is the time of the power system.

[0053] In a specific embodiment, the second impedance model is obtained using the following formula:

[0054]

[0055] Among them, Z' L is the impedance between the inverter and the grid after a fault occurs, R' L is the total resistance between the inverter and the grid after a fault occurs, L' L is the total inductance between the inverter and the grid after a fault occurs, V iis the first amplitude, ω is the angular velocity of the power system, t is the time of the power system, V' g is the amplitude of the output voltage of the power grid in the power system after the fault occurs, and δ' is the phase angle of the output voltage of the power grid after the fault occurs or the phase angle of the output voltage of the power system after the fault occurs. Specifically, after a fault occurs on the grid-connected line, the expression for the inverter fault current is written according to the grid-connected equivalent system. At this time, the grid voltage amplitude and phase angle become V' g and δ', the impedance between VSG and the grid is given by Z L becomes Z' L .

[0056] In the specific embodiments, see Figure 3 , bringing the first impedance angle of the inverter in a normal situation and the second impedance angle of the inverter after a fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period, including:

[0057] Step 201: Substitute a first impedance angle of the inverter in a normal situation and a second impedance angle of the inverter after a fault occurs into the second impedance model to obtain an output current model during the inverter fault period;

[0058] Step 202: obtaining a first power angle of the power system in a normal situation, and obtaining a second power angle of the power system after a fault occurs;

[0059] Step 203: Obtain the third output voltage according to the output current model, the first power angle, and the second power angle.

[0060] Specifically, the output current model is obtained using the following formula:

[0061]

[0062] in, is the decay time constant, and is the impedance Z before the fault L and the impedance Z' after the fault L ;

[0063] Kirchhoff's expression is written based on the grid-connected equivalent system under normal conditions:

[0064] in, is the current vector output from the power grid during normal system operation;

[0065] based on Calculate the power angle θ-δ of the system during normal operation:

[0066] Among them, I iis the magnitude of the current vector output by the inverter during normal system operation;

[0067] Write Kirchhoff's expression based on the grid-connected equivalent system under normal conditions

[0068] in, is the voltage vector output by the inverter during system fault, is the voltage vector of the power grid output during the system fault, L' L is the total inductance between the inverter and the grid during a system fault, is the current vector output by the inverter during system fault;

[0069] based on Calculate the power angle θ-δ' of the system during normal operation.

[0070] Among them, V if is the magnitude of the voltage vector output by the inverter during system fault, V' g is the magnitude of the voltage vector output by the power grid during the system fault;

[0071] The output current model, the first power angle and the second power angle are combined to obtain the third output voltage, and the expression of the third output voltage is:

[0072]

[0073] In the formula, β represents the depth of grid voltage drop.

[0074] In the specific embodiments, see Figure 4 , after obtaining the third output voltage during the inverter fault period, the method further includes:

[0075] Step 301: Optimize the third output voltage using a preset per-unit value to obtain a reference output voltage value of the inverter;

[0076] Then, using the third output voltage and the first active power output by the inverter in a normal situation, obtaining the second active power of the inverter comprises:

[0077] Step 302: Obtain a second active power of the inverter by using the reference output voltage value and the first active power output by the inverter under normal conditions;

[0078] The controlling the inverter by using the third output voltage and the second active power comprises:

[0079] Step 303: Control the inverter using the reference output voltage value and the second active power.

[0080] Specifically, refer to the national regulations on low voltage ride-through for new energy grid-connected power plants; and considering that the inductance between the inverter and the grid will not be very large, L' L Use L L Instead, control the inverter fault current to not exceed 1.4 times of normal operation, and obtain the value of the inverter reference output voltage. Change the inverter output voltage during the fault period.

[0081] In a specific embodiment, the reference output voltage value is obtained using the following formula:

[0082]

[0083] Among them, V s is the reference output voltage value, V sn is the amplitude of the inverter output voltage under normal conditions, V i is the first amplitude, V g is the second amplitude, ω is the angular velocity of the power system, L L is the total inductance between the inverter outlet and the grid under normal conditions, I i is the output current amplitude of the inverter under normal conditions, V' g is the third amplitude, is the per unit value of the grid output voltage, and k is the preset coefficient.

[0084] Specifically, the preset coefficient is preferably 7.84, and the formula for obtaining the reference output voltage value is:

[0085]

[0086] In a specific embodiment, the second active power is obtained by using the following formula:

[0087]

[0088] Among them, P ref is the second active power, V sn is the amplitude of the inverter output voltage under normal conditions, V s is the reference output voltage value, P refn It is the active power output by the inverter under normal conditions.

[0089] In the specific embodiments, see Figure 5 , is a schematic diagram of a grid-connected inverter control strategy model applied to virtual synchronous generator control in this application; by using Figure 5The control strategy model described, specifically, first is the power calculation module, which obtains the active and reactive power of the grid connection point PCC point; second is the active power-frequency calculation module, which sends the active power obtained by the power calculation module into the module, calculates and controls the frequency and angular velocity of the inverter; then is the reactive power-voltage module, which sends the reactive power obtained by the power calculation module into the module, calculates and controls the voltage amplitude of the inverter; the angular velocity obtained by the active power-frequency calculation module and the voltage amplitude obtained by the reactive power-voltage module are combined into an electromotive force. Then is the virtual impedance control module, which sends the above electromotive force into the virtual impedance control module, decouples the synthesized electromotive force to a certain extent, and obtains the reference value of the voltage in the dq0 coordinate system; finally, the above reference value is sent to the voltage and current double closed-loop control to control the output voltage and current of the inverter. By adjusting the virtual synchronous generator terminal voltage reference value, the current output during the fault period can be effectively limited, avoiding the problem of equipment protection removal caused by excessive current, especially in the case of a deep voltage drop, the stability and safety of the system can be maintained. In addition, by adding the constraint that the power angle remains unchanged before and after the fault, this method can maintain the stable operation of the VSG during the fault and prevent the system from becoming unstable, so that the VSG can still provide inertial support and voltage support to the grid under fault conditions. This strategy not only ensures that the grid can obtain sufficient reactive power support under low-voltage conditions and prevent the voltage from further dropping, but also improves the overall stability of the grid. This method significantly improves the application effect of VSG in the access of a high proportion of renewable energy to the grid, improves the fault response capability of VSG, reduces the coupling problem of active power and reactive power, and improves the accuracy of overall control. When a fault occurs in the grid and the grid connection point voltage drops to 0.3pu, the output current of the VSG inverter that does not adopt this low-voltage ride-through strategy is as follows: Figure 6a When a fault occurs at 1.0s, the output current amplitude of the inverter increases significantly, exceeding the current limit value of 490A and reaching more than 550A. When a fault occurs in the power grid and the voltage drops, the output current of the VSG inverter using this low voltage ride-through strategy is as follows: Figure 6b When a fault occurs at 1.0s, the output current amplitude of the inverter remains almost unchanged, which can prevent the inverter from being cut off by the protection device due to excessive current. When a VSG inverter that does not adopt this low voltage ride-through strategy fails in the grid and the voltage drops by 0.3pu, the output voltage is as follows Figure 6c . A fault occurs at 1.0s. After the inverter's VSG control strategy is adjusted, the inverter's output voltage only drops to 255V, about 0.8pu. It plays a supporting role in the grid voltage. When a fault occurs in the grid, the output voltage of the VSG inverter using this low voltage ride-through strategy drops by 0.3pu. Figure 6d. A fault occurred at 1.0s. After the improved VSG control strategy was adjusted, the output voltage of the inverter dropped to 182V, about 0.58pu. It is still higher than the voltage drop amplitude (0.3pu), which plays a supporting role for the grid voltage. When a fault occurs in the grid and the voltage drops by 0.3pu, the output active and reactive power of the VSG inverter that does not adopt this low voltage ride-through strategy is as follows: Figure 6e At this time, the active power and reactive power output are disordered because the original control link of the inverter has failed after the voltage drops, and the active power and reactive power are coupled and cannot be controlled by opening the control link. When the VSG inverter using this low voltage ride-through strategy fails in the power grid and the voltage drops by 0.3pu, the output active and reactive power are as follows: Figure 6f Active power and reactive power output are still coupled at the beginning, but they can be controlled separately. Finally, after the grid voltage drops, the inverter can still generate stable reactive power to support the grid voltage.

[0090] In the specific embodiments, see Figure 7 , is a structural diagram of a fault ride-through system of an inverter in the second embodiment of the present application, the system comprising: a grid-connected system fault equivalent model building module 401, a model conversion module 402, an output voltage acquisition module 403, an active power acquisition module 404 and a control module 405;

[0091] The grid-connected system fault equivalent model construction module 401 is used to construct a grid-connected system fault equivalent model using the first amplitude and first phase angle of the first output voltage of the inverter, the second amplitude and second phase angle of the second output voltage of the power grid in the power system, and the total resistance and total inductance of the filter loop between the inverter and the power grid; the grid-connected system fault equivalent model includes a first impedance model between the inverter and the power grid; the model conversion module 402 is used to obtain a second impedance model between the inverter and the power grid after the fault occurs based on the grid-connected system fault equivalent model and the third amplitude and third phase angle of the power grid output voltage after the fault occurs; the output voltage acquisition module 403 is used to bring the first impedance angle of the inverter in normal conditions and the second impedance angle of the inverter after the fault occurs into the second impedance model to obtain the third output voltage during the inverter fault period; the active power acquisition module 404 is used to obtain the second active power of the inverter using the third output voltage and the first active power output by the inverter in normal conditions; the control module 405 is used to control the inverter using the third output voltage and the second active power.

[0092] In a specific embodiment, a fault ride-through device of an inverter in the third embodiment of the present application includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method as described in any one of the first embodiments of the present application.

[0093] In a specific embodiment, a computer-readable storage medium in the fourth embodiment of the present application stores a computer program, and when the computer program is executed by a processor, the processor executes the steps of the method described in any one of the first embodiments of the present application. The technical features of the above embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A fault ride-through method for an inverter, applied to a power system, characterized in that: The method comprises: Constructing a grid-connected system fault equivalent model using a first amplitude and a first phase angle of a first output voltage of the inverter, a second amplitude and a second phase angle of a second output voltage of the power grid in the power system, and a total resistance and a total inductance of a filter loop between the inverter and the power grid; Based on the grid-connected system fault equivalent model, a third amplitude and a third phase angle of the grid output voltage after the fault occurs, obtaining a second impedance model between the inverter and the grid after the fault occurs; Substituting a first impedance angle of the inverter in a normal situation and a second impedance angle of the inverter after a fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period; Obtaining a second active power of the inverter by using the third output voltage and a first active power output by the inverter under normal conditions; The inverter is controlled by using the third output voltage and the second active power.

2. The inverter fault ride-through method according to claim 1, characterized in that: The grid-connected system fault equivalent model is obtained using the following formula: in, is the first output voltage, V i is the first amplitude, θ is the first phase angle, For the second output voltage, V g is the second amplitude, δ is the second phase angle, Z L is the total impedance, R i is the equivalent resistance between the inverter outlet and the grid connection point, L i is the equivalent inductance between the inverter outlet and the grid connection point, R linel is the equivalent resistance between the left side of the line and the fault point, Llinel is the equivalent inductance between the left side of the line and the fault point, R liner is the resistance from the fault point to the right side of the line, L liner is the inductance from the fault point to the right side of the line, R L is the total resistance, L L is the total inductance, ω is the angular velocity of the power system, and t is the time of the power system.

3. The inverter fault ride-through method according to claim 1, characterized in that: The second impedance model is obtained using the following formula: Among them, Z' L is the impedance between the inverter and the grid after a fault occurs, R' L is the total resistance between the inverter and the grid after a fault occurs, L' L is the total inductance between the inverter and the grid after a fault occurs, V i is the first amplitude, ω is the angular velocity of the power system, t is the time of the power system, V g ' is the amplitude of the output voltage of the power grid in the power system after the fault occurs, δ' is the phase angle of the output voltage of the power grid after the fault occurs or the phase angle of the output voltage of the power system after the fault occurs.

4. The inverter fault ride-through method according to claim 1, characterized in that: The step of bringing the first impedance angle of the inverter in a normal situation and the second impedance angle of the inverter after a fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period includes: Substituting a first impedance angle of the inverter in a normal situation and a second impedance angle of the inverter after a fault occurs into the second impedance model to obtain an output current model during the inverter fault period; Obtaining a first power angle of the power system under normal conditions, and obtaining a second power angle of the power system after a fault occurs; The third output voltage is obtained according to the output current model, the first power angle, and the second power angle.

5. The inverter fault ride-through method according to claim 1, characterized in that: After obtaining the third output voltage during the inverter fault period, the method further includes: Optimizing the third output voltage using a preset per-unit value to obtain a reference output voltage value of the inverter; Then, using the third output voltage and the first active power output by the inverter in a normal situation, obtaining the second active power of the inverter comprises: Obtaining a second active power of the inverter by using the reference output voltage value and a first active power output by the inverter under normal conditions; The controlling the inverter by using the third output voltage and the second active power comprises: The inverter is controlled using the reference output voltage value and the second active power.

6. The inverter fault ride-through method according to claim 5, characterized in that: The reference output voltage value is obtained by the following formula: Among them, V s is the reference output voltage value, V sn is the amplitude of the inverter output voltage under normal conditions, V i is the first amplitude, V g is the second amplitude, ω is the angular velocity of the power system, L L is the total inductance between the inverter outlet and the grid under normal conditions, I i is the output current amplitude of the inverter under normal conditions, V g ' is the third amplitude, is the per unit value of the grid output voltage, and k is the preset coefficient.

7. The inverter fault ride-through method according to claim 1, characterized in that: The second active power is obtained by using the following formula: Among them, P ref is the second active power, V sn is the amplitude of the inverter output voltage under normal conditions, V s is the reference output voltage value, P refn It is the active power output by the inverter under normal conditions.

8. A fault ride-through system for an inverter, characterized in that: The system comprises: a grid-connected system fault equivalent model building module, a model conversion module, an output voltage acquisition module, an active power acquisition module and a control module; The grid-connected system fault equivalent model construction module is used to construct a grid-connected system fault equivalent model using a first amplitude and a first phase angle of a first output voltage of an inverter, a second amplitude and a second phase angle of a second output voltage of a power grid in a power system, and a total resistance and a total inductance of a filter loop between an inverter and a power grid; the grid-connected system fault equivalent model includes a first impedance model between an inverter and a power grid; The model conversion module is used to obtain a second impedance model between the inverter and the grid after the fault occurs based on the grid-connected system fault equivalent model, the third amplitude and the third phase angle of the grid output voltage after the fault occurs; The output voltage acquisition module is used to bring the first impedance angle of the inverter under normal conditions and the second impedance angle of the inverter after a fault occurs into the second impedance model to obtain a third output voltage during the inverter fault period; The active power acquisition module is used to obtain the second active power of the inverter by using the third output voltage and the first active power output by the inverter under normal conditions; The control module is used to control the inverter using the third output voltage and the second active power.

9. A fault ride-through device for an inverter, comprising a memory and a processor, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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