Inverter control method and device, electronic equipment and medium

Abstract

The invention discloses a control method and device of an inverter, electronic equipment and a medium, and relates to the field of inverter control, when a power grid voltage drop condition exists in a power system connected with the inverter, given parameters input into a control loop of the inverter are adjusted according to different fault levels caused by the power grid voltage drop; meanwhile, whether feedforward compensation needs to be carried out on a control loop of the inverter or not is judged according to whether the inverter is overloaded or not, and finally operation of the inverter is controlled based on the determined given parameters and the feedforward compensation amount. In the control process of the inverter, if the power system breaks down and / or the load of the inverter is overloaded, the control parameters can be adjusted in time according to the change condition of the voltage of the power grid and the load state of the inverter so as to control the inverter to be always kept in a stable operation state; therefore, the operation of the inverter is prevented from being influenced by abnormal conditions such as power grid voltage drop and load switching, and the transient stability of the grid-connected inverter is improved.

Description

Technical Field

[0001] The present invention relates to the field of inverter control, and in particular to an inverter control method, device, electronic equipment and medium. Background Art

[0002] Grid-connected inverters mainly exist in new power systems with new energy as the main body. They can provide inertia, damping and active support for new power systems, and can be used as an independent AC source to build microgrids, realizing flexible switching and black start of off-grid / grid-connected control. However, with the continuous increase of new energy power generation equipment and installed capacity, users have put forward higher requirements for the stability of inverter control in power systems, especially when load switching, power fluctuations, grid voltage flicker and other situations occur. It is hoped that the inverter can provide reactive current to the grid connection point without stopping the equipment itself. This requires the inverter to always maintain transient stability. Therefore, how to ensure the transient stability of the inverter has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to provide a control method, device, electronic device and medium for an inverter. During the control process of the inverter, if a power system failure occurs and / or the load of the inverter is overloaded, the control parameters can be adjusted in time according to the changes in the grid voltage and its own load state to control the inverter to always maintain a stable operating state, thereby preventing the operation of the inverter from being affected by abnormal conditions such as grid voltage drops and load switching, thereby improving the transient stability of the grid-connected inverter.

[0004] In order to solve the above technical problems, the present invention provides a control method of an inverter, comprising:

[0005] Determining the fault level of the power system according to the voltage drop depth of the power grid of the power system to which the inverter is connected;

[0006] Determining given parameters input to a control loop of the inverter based on a fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient, and a damping coefficient;

[0007] Determining whether the inverter is currently in an overload state;

[0008] If so, a feedforward compensation amount for the control loop of the inverter is calculated, and a voltage amplitude control value and a phase control value of the inverter are generated based on the given parameters and the feedforward compensation amount.

[0009] Optionally, the fault level includes no fault, minor fault and major fault; and determining the fault level of the power system according to the grid voltage drop depth of the power system to which the inverter is connected includes:

[0010] Obtain the d-axis voltage component of the current grid voltage;

[0011] filtering the d-axis voltage component to extract a DC component from the d-axis voltage component;

[0012] Using the amplitude of the DC component as the voltage drop depth of the power grid of the power system into which the inverter is incorporated;

[0013] The fault level is determined according to the relationship between the grid voltage drop depth, a first preset value and a second preset value; the first preset value is smaller than the second preset value.

[0014] Optionally, the obtaining of the d-axis voltage component of the current grid voltage includes:

[0015] If the three-phase voltage of the power system is asymmetric, select one phase voltage of the current grid voltage as the target phase voltage;

[0016] Calculating the differential of the target phase voltage, and reconstructing based on the target phase voltage and the differential of the target phase voltage to obtain other two-phase voltages except the target phase voltage;

[0017] The target phase voltage and the reconstructed other two-phase voltages are subjected to coordinate transformation to obtain a d-axis voltage component of the current grid voltage.

[0018] Optionally, determining a given parameter input to a control loop of the inverter based on a fault level of the power system includes:

[0019] If the power system is in a fault-free state, the given parameters input to the control loop of the inverter are all rated values;

[0020] If the power system is in a minor fault state, the given parameters of the control loop input to the inverter are determined according to the grid voltage drop depth; wherein the active power given value, the reactive power regulation coefficient and the damping coefficient are positively correlated with the grid voltage drop depth, and the reactive power given value and the inertia coefficient are negatively correlated with the grid voltage drop depth.

[0021] Optionally, the determining whether the inverter is currently in an overload state includes:

[0022] Acquiring a d-axis current and / or a q-axis current in the inverter;

[0023] Determining whether the d-axis current and / or the q-axis current is greater than a preset overcurrent value;

[0024] If so, it is determined that the inverter is in an overload state.

[0025] Optionally, the calculating a feedforward compensation amount for a control loop of the inverter includes:

[0026] If the power system is in a fault-free state, based on a first proportional-integral controller, and according to the active power given value in the given parameter and the current instantaneous active power of the inverter, a first feedforward compensation amount of the active power given value is obtained;

[0027] Based on the second proportional-integral controller and according to the reactive power given value in the given parameter and the current instantaneous reactive power of the inverter, a second feedforward compensation amount of the reactive power given value is obtained.

[0028] Optionally, the calculating a feedforward compensation amount for a control loop of the inverter includes:

[0029] If the power system is in a minor fault state, based on an integral controller and according to the angular frequency currently output by the inverter and the rated angular frequency, a third feedforward compensation amount of the active power given value is obtained;

[0030] A fourth feedforward compensation amount of the reactive power set value is determined according to a difference between the reactive power set value and a preset reactive compensation value.

[0031] In order to solve the above technical problems, the present invention further provides a control device for an inverter, comprising:

[0032] A fault determination unit, configured to determine a fault level of the power system according to a voltage drop depth of a power grid of the power system to which the inverter is connected;

[0033] A given parameter determination unit, configured to determine given parameters input to a control loop of the inverter based on a fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient, and a damping coefficient;

[0034] An overload judgment unit, used to judge whether the inverter is currently in an overload state; if so, triggering a feedforward compensation unit;

[0035] The feedforward compensation unit is used to calculate the feedforward compensation amount for the control loop of the inverter, and generate the voltage amplitude control value and the phase control value of the inverter based on the given parameters and the feedforward compensation amount.

[0036] In order to solve the above technical problems, the present invention further provides an electronic device, comprising:

[0037] Memory for storing computer programs;

[0038] A processor is used to implement the steps of the inverter control method as described above.

[0039] In order to solve the above technical problem, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the inverter control method as described above are implemented.

[0040] The present invention provides a control method for an inverter. When a power system to which the inverter is connected has a grid voltage drop, given parameters input into a control loop of the inverter are adjusted according to different fault levels caused by the grid voltage drop; at the same time, whether feedforward compensation is required for the control loop of the inverter is determined according to whether the inverter is overloaded, and finally the operation of the inverter is controlled based on the determined given parameters and feedforward compensation amount; in the process of controlling the inverter, if a fault occurs in the power system and / or the load of the inverter is overloaded, the control parameters can be adjusted in time according to the change of the grid voltage and its own load state, so as to control the inverter to always maintain a stable operating state, thereby preventing the operation of the inverter from being affected by abnormal conditions such as grid voltage drop and load switching, and improving the transient stability of the grid-connected inverter.

[0041] The present invention also provides a control device for an inverter, an electronic device and a computer-readable storage medium, which have the same beneficial effects as the above-mentioned control method for the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A schematic flow chart of a control method for an inverter provided by the present invention;

[0044] Figure 2 A schematic diagram of the structure of a control system of an inverter provided by the present invention;

[0045] Figure 3 A schematic diagram of the structure of a given parameter adjustment loop of an inverter provided by the present invention;

[0046] Figure 4 A schematic diagram of the structure of a control device for an inverter provided by the present invention;

[0047] Figure 5 The present invention provides a schematic structural diagram of an electronic device. DETAILED DESCRIPTION

[0048] The core of the present invention is to provide a control method, device, electronic device and medium for an inverter. During the control process of the inverter, if a power system failure occurs and / or the load of the inverter is overloaded, the control parameters can be adjusted in time according to the changes in the grid voltage and its own load state to control the inverter to always maintain a stable operating state, thereby preventing the operation of the inverter from being affected by abnormal conditions such as grid voltage drops and load switching, thereby improving the transient stability of the grid-connected inverter.

[0049] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Please refer to Figure 1 , Figure 1 A flow chart of a control method for an inverter provided by the present invention; To solve the above technical problems, the present invention provides a control method for an inverter, comprising:

[0051] S11: determining a fault level of the power system according to a voltage drop depth of the power grid of the power system to which the inverter is connected;

[0052] It is not difficult to understand that in order to ensure the transient stability of the inverter, it is first necessary to avoid the influence of the disturbance of the power system in parallel with the grid-connected inverter on the stable operation of the inverter. Since the inverter will maintain connection with the power grid through the grid connection point, it is mainly the drop of the grid voltage in the power system that will seriously affect the stable operation of the inverter. The drop of the grid voltage is manifested as a sudden drop in voltage, which will cause the voltage of the grid connection point connected to the inverter to drop abnormally, thereby causing transient instability of the inverter. Considering that the grid voltage will drop to different degrees, corresponding to different fault levels of the power system, the control strategy of the inverter at different fault levels will also be different. Therefore, before regulating the inverter, it is necessary to first determine the specific fault situation according to the current grid voltage drop depth of the power system, so as to perform different parameter adjustment processes according to different fault levels. There may be multiple implementation methods for the corresponding relationship between the grid voltage drop depth and the fault level due to factors such as application scenarios, and this application does not make any special restrictions here. The voltage drop of the power grid refers to the process in which the voltage suddenly drops from the rated value to a certain potential point. The voltage drop depth refers to the voltage drop amplitude of the power grid when it drops, that is, the voltage amplitude reduced when the voltage drops suddenly.

[0053] S12: Determine given parameters of a control loop input to the inverter based on the fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient, and a damping coefficient;

[0054] It can be understood that transient stability refers to the ability of a device to transition to a new or return to its original stable operating state after being disturbed. In the event of a fault in the power system, the inverter may be at risk of instability. The present invention adjusts the control process of the inverter by automatically adjusting the given parameters in the control loop of the inverter when the inverter is at risk of instability, so that the inverter can transition to a new stable operating state, thereby ensuring its continuous and stable operation. The given parameters refer to the control parameters of the inverter control system when controlling the inverter operation, and are control parameters that can directly affect the voltage and phase of the inverter when it is running. The specific type and implementation method of the given parameters can be selected and adjusted according to the specific structure of the control loop in the inverter control system. This application does not make any special restrictions here. In general, the given parameters can include active power given values, reactive power given values, reactive adjustment coefficients, inertia coefficients, and damping coefficients.

[0055] S13: Determine whether the inverter is currently in an overload state;

[0056] Furthermore, in addition to the sudden drop in grid voltage, load switching, power fluctuations, and other conditions may occur on the load side of the inverter. These abnormal conditions may cause overload on the load side of the inverter. When the inverter is overloaded, the frequency or voltage of the inverter will drop more seriously, affecting the normal operation of the inverter and the power system. Therefore, it is necessary to determine whether the inverter control process needs to be further adjusted based on whether the inverter is overloaded. There are many ways to determine whether the inverter is overloaded, and this application does not make any special restrictions here.

[0057] S14: If yes, then calculate the feedforward compensation amount for the control loop of the inverter, and generate the voltage amplitude control value and phase control value of the inverter based on the given parameters and the feedforward compensation amount.

[0058] It is not difficult to understand that, considering the overload situation of the inverter, there will mainly be abnormal situations of frequency or voltage drop. Therefore, the present application avoids the situation of frequency or voltage drop by adding a certain amount of feedforward compensation to the control loop of the inverter when overloaded. At this time, the control system of the inverter not only needs to generate the voltage amplitude control value and phase control value of the inverter through given parameters to control the inverter, but also needs to take the feedforward compensation into account, adjust the voltage amplitude control value and phase control value of the inverter, and comprehensively consider the disturbance of the operation caused by the grid fault and its own load state to ensure the dynamic stability of the inverter and the power system. The present application does not make any special restrictions on the specific type and value of the feedforward compensation, which is usually achieved by feedforward compensation for a given power.

[0059] It should be noted that in order to avoid the inverter's current out of control, the feedforward compensation amount needs to be set within a certain preset range. Therefore, after calculating the feedforward compensation amount, it needs to be limited according to the preset range, and then it is fed forward. At the same time, this application sets different feedforward compensation amounts for overloads under different fault conditions. By switching the feedforward compensation amount and the limiting process, the instantaneous current overcurrent situation is avoided to ensure the safety of the equipment. The given value of the inverter's output current can also be limited to suppress instantaneous overcurrent.

[0060] If the inverter is not overloaded, a voltage amplitude control value and a phase control value of the inverter are generated based on given parameters.

[0061] It is understandable that if the inverter is not overloaded, the given parameters determined according to the fault level can be directly used to generate the voltage amplitude control value and phase control value of the inverter to control the inverter. At this time, only the disturbance of the grid fault to the operation needs to be considered. Therefore, it is only necessary to adjust the given parameters of the inverter control loop according to different fault conditions.

[0062] It should be noted that the present application does not make any special limitations on the specific types and implementation methods of the power system, inverter, and inverter control system. The inverter control method provided in the present application is not only applicable to devices such as grid-connected inverters, but also to other APF (Active Power Filter) and other power conversion devices or converters. When a fault occurs in the power system and / or the equipment is overloaded, parameter switching and / or power feedforward can be performed in a timely manner by switching between different modes, thereby effectively suppressing the instantaneous overcurrent of the equipment and improving the transient stability of the equipment itself and the power system.

[0063] As a specific embodiment, please refer to Figure 2 , Figure 2 A schematic diagram of the structure of a control system of an inverter provided by the present invention; the control loop of the inverter first obtains the active power given value as the control target and reactive power setpoint , and obtain the feedforward compensation for active power and feedforward compensation for reactive power On the one hand, the active power given value is subtracted from the active power P currently output by the inverter, and then the difference is made between it and the feedforward compensation of the active power given value. The final result is input into the first integral control link. , the inertia coefficient of the first integral control link is J, the damping coefficient is D, and the deviation value is obtained through the first integral control link. The deviation value and the rated angular frequency Superimpose each other to obtain the final angular frequency control value The angular frequency control value is input into the current outer loop and the current inner loop, and finally passes through the second integral control link. Get the phase control value of the inverter On the other hand, the reactive power given value is subtracted from the reactive power Q currently output by the inverter, and then the difference is made from the feedforward compensation of the reactive power given value, and finally multiplied by the reactive power regulation coefficient. The final result is superimposed on the ideal rated voltage U0 of the inverter to be output, and then subtracted from the effective value U of the actual output voltage of the inverter, and then passes through the third integral control link. Get the voltage amplitude control value E of the inverter m Then the inverter control system constructs the phase control value and the voltage amplitude control value into a three-phase voltage, and performs coordinate transformation on the three-phase voltage, and then generates a drive signal wave to control the inverter through the voltage outer loop and the current inner loop control, and finally outputs the drive signal wave to the inverter circuit through modulation and wave transmission to control the inverter operation.

[0064] The control method of the inverter provided in the present application is a control method for improving the transient stability of the inverter VSG (virtual synchronous generator). A parameter switching module in case of fault and a power feedforward compensation module in case of overload are added to the grid-connected inverter, and parameter design adjustment and power feedforward are performed to reduce the overcurrent caused by the grid voltage sag, and improve the transient stability of the grid-connected inverter. A multi-mode switching fault crossing method is provided, which can be used for operation when the power system fails and / or the equipment is overloaded, and is used for the control of the grid-connected inverter, which can reduce the transient impact current and effectively improve the transient stability of the system. The stably operating inverter can also provide the reactive power required for fault crossing for the power system, thereby helping the power system to achieve fault crossing, which can effectively improve the transient stability of the inverter of large-scale power generation equipment and the fault crossing capability of the power system.

[0065] The present invention provides a control method for an inverter. When a power system to which the inverter is connected has a grid voltage drop, given parameters input into a control loop of the inverter are adjusted according to different fault levels caused by the grid voltage drop; at the same time, whether feedforward compensation is required for the control loop of the inverter is determined according to whether the inverter is overloaded, and finally the operation of the inverter is controlled based on the determined given parameters and feedforward compensation amount; in the process of controlling the inverter, if a fault occurs in the power system and / or the load of the inverter is overloaded, the control parameters can be adjusted in time according to the change of the grid voltage and its own load state, so as to control the inverter to always maintain a stable operating state, thereby preventing the operation of the inverter from being affected by abnormal conditions such as grid voltage drop and load switching, and improving the transient stability of the grid-connected inverter.

[0066] Based on the above embodiments:

[0067] As an optional embodiment, the fault level includes no fault, light fault and heavy fault; the fault level of the power system is determined according to the grid voltage drop depth of the power system to which the inverter is connected, including:

[0068] Obtain the d-axis voltage component of the current grid voltage;

[0069] filtering the d-axis voltage component to extract a DC component from the d-axis voltage component;

[0070] The magnitude of the DC component is taken as the grid voltage drop depth of the power system to which the inverter is connected;

[0071] The fault level is determined according to the relationship between the grid voltage drop depth, the first preset value and the second preset value; the first preset value is smaller than the second preset value.

[0072] Determining the fault level according to the relationship between the grid voltage drop depth, the first preset value and the second preset value specifically includes:

[0073] When the grid voltage drop depth is less than a first preset value, it is determined that the power system is in a fault-free state;

[0074] When the grid voltage drop depth is not less than a first preset value and not greater than a second preset value, it is determined that the power system is in a minor fault state;

[0075] When the grid voltage drop depth is greater than a second preset value, it is determined that the power system is in a serious fault state;

[0076] It can be understood that the stable DC component of the d-axis component in the grid voltage can directly reflect the drop depth of the grid voltage, so the current d-axis voltage component of the grid voltage can be directly obtained, and then the high-frequency component can be filtered out by filtering to obtain the DC component, and the grid voltage drop depth can be determined directly according to the amplitude of the DC component. The deeper the grid voltage drops, the more serious the fault of the power system. Therefore, the fault level of the power system can be directly determined according to the depth of the grid voltage drop. The specific implementation method of filtering is not particularly limited in this application, and it can be implemented by low-pass filtering and other methods. It can be implemented by using a second-order low-pass filtering module. There are also many ways to obtain the d-axis voltage component of the current grid voltage. The three-phase voltage currently output by the power system can be obtained by a voltage detection device, and the d-axis voltage component can be extracted by park transformation. The specific values ​​of the first preset value, the second preset value and the third preset value are not particularly limited in this application, and can be set and adjusted according to the actual application scenario.

[0077] Specifically, the grid voltage drop depth can be determined by acquiring the grid voltage in real time. The drop depth can be acquired in time, and the grid voltage drop depth acquisition process can be realized without delay. This is simple, effective, and easy to implement, thereby improving the accuracy and timeliness of the inverter control process.

[0078] As an optional embodiment, obtaining the d-axis voltage component of the current grid voltage includes:

[0079] If the three-phase voltage of the power system is asymmetric, select one phase voltage of the current grid voltage as the target phase voltage;

[0080] Calculating the differential of the target phase voltage, and reconstructing based on the target phase voltage and the differential of the target phase voltage to obtain other two phase voltages except the target phase voltage;

[0081] The target phase voltage and the reconstructed other two-phase voltages are transformed into coordinates to obtain the d-axis voltage component of the current grid voltage.

[0082] It is not difficult to understand that the grid voltage drop is divided into two cases: symmetrical drop and asymmetrical drop. When the grid voltage drops symmetrically, the grid drop depth can be directly obtained by calculating the d-axis voltage component after the three-phase voltage coordinate transformation. However, when the grid voltage drops asymmetrically, due to the asymmetry of the three-phase drop, when determining the drop depth, the acquisition of the d-axis voltage component needs to be achieved by reconstructing the grid voltage calculation. Reconstruction refers to the process of determining the drop depth by constructing the other two phases of the three-phase voltage when a certain phase voltage drops, and then obtaining the voltage amplitude through coordinate transformation.

[0083] As a specific embodiment, taking the a-phase voltage drop, that is, the target phase voltage is the a-phase voltage as an example, the reconstruction needs to first calculate the differential of the a-phase voltage , and then by the formula The reconstructed b-phase voltage and c-phase voltage are calculated to obtain the reconstructed three-phase voltage. Then, the d-axis voltage component is calculated by coordinate transformation of the three-phase voltage. The calculated d-axis voltage component is filtered through a second-order low-pass filter to obtain the grid voltage drop depth. .in, is the phase a voltage of the power grid, is the b-phase voltage of the power grid, is the c-phase voltage of the power grid, is the angular frequency of the power grid, t is the time, is the peak value of the phase voltage of the power grid.

[0084] Furthermore, when the grid voltage drops asymmetrically, since the voltage hardware sampling circuit usually obtains the target phase voltage by sampling the line voltage when obtaining the target phase voltage, and then calculates the three-phase voltage, this method is more accurate in calculating the voltage amplitude only when the three-phase grid voltage is balanced. When the three-phase grid voltage is unbalanced or the single-phase voltage drops deeply, there will be certain errors in the calculation of the amplitude that finally represents the depth of grid voltage drop, resulting in errors in the final grid voltage drop depth. Therefore, at this time, the calculated grid voltage drop depth can be corrected by querying the preset table online. Specifically, the corrected grid voltage drop depth is obtained by multiplying the grid voltage drop depth by the preset coefficient, that is, ,in, is the corrected grid voltage drop depth, K is a preset coefficient, and the preset coefficient may be a correction coefficient summarized through experience and / or repeated experiments. This application does not make any special limitation on its value and determination method.

[0085] Specifically, in the case of an asymmetric drop in the grid voltage, the d-axis voltage component that can accurately characterize the depth of the grid voltage drop can be determined by reconstructing the three-phase voltage and actively correcting it. The drop depth can be quickly and accurately obtained through active correction methods based on the reconstructed three-phase voltage, thereby improving the accuracy and reliability of the final d-axis voltage component and the grid voltage drop depth.

[0086] As an optional embodiment, determining a given parameter of a control loop input to an inverter based on a fault level of the power system includes:

[0087] If the power system is in a fault-free state, the given parameters of the control loop input to the inverter are all rated values;

[0088] If the power system is in a minor fault state, the given parameters of the control loop input to the inverter are determined according to the depth of the grid voltage drop; among them, the active power given value, reactive power regulation coefficient and damping coefficient are positively correlated with the depth of the grid voltage drop, and the reactive power given value and inertia coefficient are negatively correlated with the depth of the grid voltage drop.

[0089] It can be understood that, generally when the grid voltage drop depth is relatively small, the power system and the inverter can maintain transient stability by themselves. At this time, it can be determined that the power system is in a fault-free state and no additional control is required; after the grid voltage drop depth reaches a certain value, it is necessary to adopt the control method provided in the present application to help the inverter maintain transient stability. At this time, the inverter can be kept transiently stable by adjusting parameters and other methods, and the parameters can be adjusted to different degrees for grid voltage drop depths of different sizes; when the grid voltage drop depth is too large, the fault in the power system is already serious, and parameter adjustment is difficult to control the inverter to maintain transient stability. At this time, the fault can be directly reported and the inverter can be shut down without continuing to control the inverter.

[0090] As a specific embodiment, the fault level can be judged according to the different drop depths of the grid voltage, and the switching in and out of different given quantities can be controlled. The drop degree of the grid voltage can be divided into three levels, namely, no fault, light fault, and heavy fault. When the system is in a no-fault state (>0.85pu), the given quantity and control parameters of the power loop can be implemented with rated values, that is, the active / reactive power given value is the rated active / reactive power, the reactive adjustment coefficient is the initialized reactive adjustment coefficient, and the inertia coefficient and damping coefficient are the initialized inertia and damping parameters; when the system is in a light fault state (0.2pu-0.85pu), according to the grid drop depth, the given value of active / reactive power, the reactive adjustment coefficient, the inertia and the damping coefficient are set by establishing a corresponding relationship table in advance. When the system is in a heavy fault state (<0.2pu), the system directly reports a fault and shuts down.

[0091] It should be noted that pu is a representation method of the per-unit value of the d-axis voltage component. Under normal circumstances, the grid voltage is 1pu, for example, 0.2pu means that the grid voltage drops to 0.2pu. For example, taking the phase voltage of 220V as an example, 0.2pu means that the grid voltage has become 44V. The specific implementation method of the preset corresponding relationship table is not particularly limited in this application. Generally, it is a corresponding relationship table between the grid voltage drop depth and the given parameters that support the stable operation of the inverter obtained through theoretical analysis and experiments. When the grid fails, an instantaneous current impact will occur at the connection between the equipment and the grid. Therefore, when the grid fails, the purpose of switching the given active / reactive power, reactive adjustment coefficient, inertia coefficient and damping coefficient is mainly to reduce the instantaneous current, thereby improving the transient stability of the inverter. The adjusted inertia coefficient and reactive power given value are negatively correlated with the voltage drop depth, that is, the deeper the drop depth, the smaller the inertia coefficient and reactive power given value should be set, so that the control system can adjust the output frequency in time to reduce the impact current. The adjusted active power set value, reactive power adjustment coefficient and damping coefficient are positively correlated with the drop depth, that is, when the grid voltage drops, the deeper the drop depth, the larger the active power set value, reactive power adjustment coefficient and damping coefficient should be set. By switching the state at the transient moment, the impact current is reduced and the transient stability of the system is improved. That is: .

[0092] Specifically, the faults of the power system can be divided into no fault, minor fault and major fault according to the drop depth. In different states, different control variables are switched as given parameters of the control system. The values ​​of the specific given parameters can also be determined according to the specific drop degree, thereby effectively reducing the impact current, improving the transient stability of the inverter, and enhancing the fault ride-through capability of the power system.

[0093] As an optional embodiment, determining whether the inverter is currently in an overload state includes:

[0094] Obtaining a d-axis current and / or a q-axis current in the inverter;

[0095] Determine whether the d-axis current and / or the q-axis current is greater than a preset overcurrent value;

[0096] If yes, it is determined that the inverter is in an overload state.

[0097] It is not difficult to understand that whether the inverter is overloaded will be directly reflected in the magnitude of its current. Therefore, it is possible to directly detect the actual value of the dq axis current in the inverter and the amplitude of the dq axis current to determine whether the inverter is in an overload state, so as to calculate and select the feedforward compensation amount later. If the d axis current / or q axis current is greater than the preset overcurrent value, the inverter is in an overload state; if the d axis current / or q axis current is not greater than the preset overcurrent value, the inverter is not overloaded. In general, a current exceeding 1.4 times the rated current is defined as an overload. In actual applications, the preset overcurrent value is not limited to this definition and can be adjusted according to the actual application and load conditions. This application does not make any special restrictions here. Overload essentially means that the current flowing through the inverter has increased. The inverter hardware itself has the maximum power or current that it can withstand. If the overload is too much, the inverter hardware cannot withstand it and it is difficult to maintain normal and stable operation. Therefore, it is necessary to perform feedforward compensation on the control loop according to whether the inverter is overloaded or not.

[0098] Specifically, whether the device is overloaded can be directly judged according to the actual amplitude of the current in the inverter. The current acquisition method is simple and easy to implement, which is conducive to the simple implementation of the control method of the entire inverter.

[0099] Please refer to Figure 3 , Figure 3 A schematic diagram of a given parameter adjustment loop of an inverter provided by the present invention; the area formed by a single-dash line is a compensation loop 1, and the area formed by a double-dash line is a compensation loop 2. As an optional embodiment, calculating the feedforward compensation amount for the control loop of the inverter includes:

[0100] If the power system is in a fault-free state, based on the first proportional-integral controller, and according to the active power given value in the given parameters and the current instantaneous active power of the inverter, a first feedforward compensation amount of the active power given value is obtained;

[0101] Based on the second proportional-integral controller and according to the reactive power given value in the given parameters and the current instantaneous reactive power of the inverter, a second feedforward compensation amount of the reactive power given value is obtained.

[0102] The process of obtaining the first feedforward compensation amount specifically includes: subtracting the active power given value in the given parameter input into the control loop of the inverter from the current instantaneous active power of the inverter;

[0103] The difference between the active power given value and the current instantaneous active power of the inverter is input as a deviation into the first proportional integral controller to obtain a first feedforward compensation amount for the active power given value in the control loop of the inverter; the first feedforward compensation amount is a feedforward compensation amount for the active power given value in the control loop of the inverter;

[0104] The process of obtaining the second feedforward compensation amount specifically includes: subtracting the reactive power given value in the given parameter input into the control loop of the inverter from the current instantaneous reactive power of the inverter;

[0105] The difference between the reactive power set value and the current instantaneous reactive power of the inverter is input as a deviation into the second proportional-integral controller to obtain a second feedforward compensation amount for the reactive power set value in the control loop of the inverter; the second feedforward compensation amount is a feedforward compensation amount for the reactive power set value in the control loop of the inverter.

[0106] It is understandable that in the case of inverter overload, the control system will also take into account the fault conditions of the power system to adjust the feedforward compensation of the control loop. Figure 3 The compensation loop 1 shown in the figure is used to perform feedforward compensation on the control loop. Considering the influence of overload on the stable operation of the inverter, the active power given value and reactive power given value in the given parameters can be further corrected. The loop design is that the corrected active power given value P2 is connected to the instantaneous active power P of the inverter after filtering. flt The difference is then obtained after the first PI controller and the limiter to obtain the compensated power, which is the feedforward compensation of the active power given value. ; The corrected reactive power given value Q2 and the instantaneous reactive power Q of the inverter after filtering flt The difference is then obtained after the second PI controller and the limiter to obtain the compensated power, which is the feedforward compensation of the reactive power given value. .

[0107] Specifically, under different fault conditions, the power loop implements different feedforward compensation amounts by switching into different compensation loops, thereby fully considering the impact of various different conditions of equipment overload and grid failure on the inverter control process, ensuring that the transient stability of the inverter under different fault conditions can be effectively improved.

[0108] As an optional embodiment, calculating a feedforward compensation amount for a control loop of an inverter includes:

[0109] If the power system is in a light fault state, based on the integral controller and according to the angular frequency currently output by the inverter and the rated angular frequency, a third feedforward compensation amount of the active power given value is obtained;

[0110] A fourth feedforward compensation amount of the reactive power set value is determined according to a difference between the reactive power set value and a preset reactive compensation value.

[0111] The process of obtaining the third feedforward compensation amount specifically includes: calculating the difference between the angular frequency currently output by the inverter and the rated angular frequency;

[0112] The difference between the angular frequency currently output by the inverter and the rated angular frequency is input as an error into an integral controller to obtain a third feedforward compensation amount for the given active power value in the control loop of the inverter; the third feedforward compensation amount is a feedforward compensation amount for the given active power value in the control loop of the inverter;

[0113] The process of obtaining the fourth feedforward compensation amount specifically includes: calculating the difference between the reactive power given value in the given parameters input into the control loop of the inverter and the preset reactive compensation value, and using the difference as the fourth feedforward compensation amount for the reactive power given value in the control loop of the inverter; the fourth feedforward compensation amount is the feedforward compensation amount for the reactive power given value in the control loop of the inverter.

[0114] It is not difficult to understand that when the inverter is in overload operation and a minor fault occurs in the power system, the feedforward quantity needs to be switched in time, and the control system will switch on. Figure 3 The compensation loop 2 shown in the figure is used to perform feedforward compensation on the control loop. Considering the influence of overload on the stable operation of the inverter, the active power given value and reactive power given value in the given parameters can be further corrected. The loop is designed as the angular frequency of the inverter output. With rated angular frequency Make a difference, after the integral link and the adjustment coefficient After multiplication, the feedforward active difference is obtained, that is, the feedforward compensation amount of the active power given value The reactive loop compensates by directly adjusting the given reactive power, and further subtracts the given reactive power from the preset value Q3 as the feedforward compensation of the given reactive power value. .

[0115] As a specific embodiment, the present invention determines the given parameters of the control loop input to the inverter according to the fault condition of the power system, and selects whether the inverter is overloaded to switch in or out the feedforward compensation amount, and can further adjust the determined given parameters. Figure 3 Selected active power setpoint , reactive power given value , reactive power regulation coefficient , inertia coefficient J and damping coefficient D are input to Figure 2 The inverter operation control is performed in the control loop of the inverter shown in FIG. When the power system has no faults and the inverter is not overloaded, the feedforward compensation amount is 0. At this time, the given parameters select the rated value. The active power given value adopts the rated value P0, the reactive power given value adopts the rated value Q0, and the reactive power adjustment coefficient adopts the rated value K. q0, the inertia coefficient adopts the rated value J0, and the damping coefficient adopts the rated value D0; when the power system is in a minor fault and the inverter is not overloaded, the feedforward compensation amount is 0, at this time, the active power set value is adjusted to P1, the reactive power set value is adjusted to Q1, and the reactive power adjustment coefficient is adjusted to K q1 , the inertia coefficient is adjusted to J1, and the damping coefficient is adjusted to D1; when the power system is fault-free and the inverter is overloaded, the power setting is dynamically compensated by switching into the power compensation loop 1. At this time, the active power setting value is adjusted to P2, the reactive power setting value is adjusted to Q2, and the reactive power adjustment coefficient adopts the rated value K q0 , the inertia coefficient adopts the rated value J0, and the damping coefficient adopts the rated value D0; when the power system is in a minor fault and the inverter is overloaded, it is necessary to switch into compensation loop 2 to dynamically compensate the power, and the current loop needs to limit the given value, so as to reduce the current impact at the moment of the fault and improve the dynamic stability of the system. At this time, the active power given value is adjusted to P2, the reactive power given value is adjusted to Q2, and the reactive power adjustment coefficient adopts the rated value K q0 , the inertia coefficient adopts the rated value J0, and the damping coefficient adopts the rated value D0. It should be noted that, in the case of a minor fault in the power system, the given parameters of the control loop input to the inverter can be determined according to the specific value of the grid voltage drop depth, so P1, Q1, K q1 , J1, and D1 can be a set of values ​​corresponding to different grid voltage drop depths and are not limited to a single value. Figure 3 P0, Q0, K in q0 , J0, D0, P1, Q1, K q1 , J1, D1, P2, Q2, and Q3 are all preset values ​​determined based on experience or repeated tests. Their specific values ​​can be selected and adjusted according to different actual application situations, and this application does not make any special limitations here.

[0116] Specifically, the control system can switch different calculation loops of power feedforward components according to different working conditions of the power system to reduce overcurrent caused by grid voltage sag. Under different fault conditions, the power loop switches into different compensation loops to achieve different feedforward compensation amounts, thereby fully considering the impact of various different conditions of equipment overload and grid fault on the control process of the inverter, ensuring that the transient stability of the inverter under different fault conditions can be effectively improved.

[0117] Please refer to Figure 4 , Figure 4 A schematic diagram of the structure of a control device for an inverter provided by the present invention; To solve the above technical problems, the present invention also provides a control device for an inverter, comprising:

[0118] A fault determination unit 11, configured to determine a fault level of the power system according to a voltage drop depth of a power grid of the power system to which the inverter is connected;

[0119] A given parameter determination unit 12 is used to determine given parameters of a control loop input to the inverter based on the fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient and a damping coefficient;

[0120] An overload judgment unit 13 is used to judge whether the inverter is currently in an overload state; if so, the feedforward compensation unit is triggered;

[0121] The feedforward compensation unit 14 is used to calculate the feedforward compensation amount for the control loop of the inverter, and generate the voltage amplitude control value and the phase control value of the inverter based on the given parameters and the feedforward compensation amount.

[0122] As an optional embodiment, the fault determination unit 11 includes:

[0123] A voltage component acquisition unit, used to acquire the d-axis voltage component of the current grid voltage;

[0124] a filtering unit, configured to filter the d-axis voltage component to extract a DC component from the d-axis voltage component;

[0125] A drop depth determination unit, configured to use the amplitude of the DC component as a grid voltage drop depth of the power system into which the inverter is incorporated;

[0126] A fault determination unit is used to determine the fault level according to the relationship between the grid voltage drop depth, a first preset value and a second preset value; the first preset value is smaller than the second preset value.

[0127] As an optional embodiment, if the three-phase voltage of the power system is asymmetric, the voltage component acquisition unit includes:

[0128] A target phase selection unit, used for selecting a phase voltage of the current grid voltage as a target phase voltage;

[0129] A three-phase voltage reconstruction unit, configured to calculate the differential of the target phase voltage, and to reconstruct based on the target phase voltage and the differential of the target phase voltage to obtain other two-phase voltages except the target phase voltage;

[0130] The voltage component acquisition subunit is used to perform coordinate transformation on the target phase voltage and the reconstructed other two-phase voltages to obtain the d-axis voltage component of the current grid voltage.

[0131] As an optional embodiment, the given parameter determination unit 12 includes:

[0132] A first parameter determination unit, configured to, if the power system is in a fault-free state, use rated values ​​for given parameters input to a control loop of the inverter;

[0133] The second parameter determination unit is used to determine the given parameters of the control loop input to the inverter according to the grid voltage drop depth if the power system is in a minor fault state; wherein the active power given value, the reactive power regulation coefficient and the damping coefficient are positively correlated with the grid voltage drop depth, and the reactive power given value and the inertia coefficient are negatively correlated with the grid voltage drop depth.

[0134] As an optional embodiment, the overload judgment unit 13 includes:

[0135] A current acquisition unit, used to acquire a d-axis current and / or a q-axis current in the inverter;

[0136] An overload judgment subunit, used to judge whether the d-axis current and / or the q-axis current is greater than a preset overcurrent value; if so, triggering an overload judgment unit;

[0137] The overload determination unit is used to determine whether the inverter is in an overload state.

[0138] As an optional embodiment, the feedforward compensation unit 14 includes:

[0139] A first feedforward compensation amount determination unit, configured to obtain a first feedforward compensation amount of the active power given value based on a first proportional-integral controller and according to the active power given value in the given parameter and the current instantaneous active power of the inverter;

[0140] The second feedforward compensation amount determination unit is used to obtain the second feedforward compensation amount of the reactive power given value based on the second proportional-integral controller and according to the reactive power given value in the given parameters and the current instantaneous reactive power of the inverter.

[0141] As an optional embodiment, the feedforward compensation unit 14 includes:

[0142] A third feedforward compensation amount determination unit, configured to obtain a third feedforward compensation amount of the active power given value based on an integral controller and according to an angular frequency currently output by the inverter and a rated angular frequency;

[0143] The fourth feedforward compensation amount determining unit is used to determine the fourth feedforward compensation amount of the reactive power set value according to the difference between the reactive power set value and the preset reactive compensation value.

[0144] For an introduction to an inverter control device provided by the present invention, please refer to the embodiment of the inverter control method described above, and the present invention will not be described in detail here.

[0145] Please refer to Figure 5 , Figure 5 The present invention provides a schematic diagram of the structure of an electronic device. To solve the above technical problems, the present invention also provides an electronic device, including:

[0146] A memory 21, used for storing computer programs;

[0147] The processor 22 is used to implement the steps of the inverter control method as described above.

[0148] Among them, the processor 22 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 22 can be implemented in at least one hardware form of DSP (Digital Signal Processor), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). The processor 22 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also known as a central processing unit; the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 22 may integrate a GPU (graphics processing unit), which is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 22 may also include an AI (Artificial Intelligence) processor, which is used to process computing operations related to machine learning.

[0149] The memory 21 may include one or more computer-readable storage media, which may be non-transitory. The memory 21 may also include a high-speed random access memory, and a non-volatile memory, such as one or more disk storage devices, flash memory storage devices. In this embodiment, the memory 21 is at least used to store the following computer program, wherein, after the computer program is loaded and executed by the processor 22, it can implement the relevant steps of the control method of the inverter disclosed in any of the aforementioned embodiments. In addition, the resources stored in the memory 21 may also include an operating system and data, etc., and the storage method may be temporary storage or permanent storage. Among them, the operating system may include Windows, Unix, Linux, etc. The data may include but is not limited to the data of the control method of the inverter, etc.

[0150] In some embodiments, the electronic device may further include a display screen, an input / output interface, a communication interface, a power supply, and a communication bus.

[0151] It can be understood by those skilled in the art that Figure 5 The structure shown in the figure does not constitute a limitation on the electronic device, and may include more or fewer components than shown in the figure.

[0152] For an introduction to an electronic device provided by the present invention, please refer to the embodiment of the inverter control method described above, and the present invention will not be described in detail here.

[0153] In order to solve the above technical problems, the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the inverter control method as described above are implemented.

[0154] It is understandable that if the method in the above embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium to execute all or part of the steps of the method described in each embodiment of the present application. Specifically, the computer-readable storage medium may include but is not limited to any type of disk, including a floppy disk, an optical disk, and a mobile hard disk, or any type of medium or device suitable for storing instructions, data, etc., and the present application does not make any special restrictions here.

[0155] For an introduction to a computer-readable storage medium provided by the present invention, please refer to the embodiment of the inverter control method described above, and the present invention will not be repeated here.

[0156] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0157] It should also be noted that, in this specification, 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 "comprise", "include" 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, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0158] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0159] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for an inverter, It is characterized in that include: Determining the fault level of the power system according to the voltage drop depth of the power grid of the power system to which the inverter is connected; Determining given parameters input to a control loop of the inverter based on a fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient, and a damping coefficient; Determining whether the inverter is currently in an overload state; If so, a feedforward compensation amount for the control loop of the inverter is calculated, and a voltage amplitude control value and a phase control value of the inverter are generated based on the given parameters and the feedforward compensation amount.

2. The control method of the inverter according to claim 1, It is characterized in that The fault levels include no fault, minor fault and major fault; the fault level of the power system is determined according to the grid voltage drop depth of the power system to which the inverter is connected, including: Obtain the d-axis voltage component of the current grid voltage; filtering the d-axis voltage component to extract a DC component from the d-axis voltage component; Using the amplitude of the DC component as the voltage drop depth of the power grid of the power system into which the inverter is incorporated; The fault level is determined according to the relationship between the grid voltage drop depth, a first preset value and a second preset value; the first preset value is smaller than the second preset value.

3. The inverter control method according to claim 2, It is characterized in that The step of obtaining the d-axis voltage component of the current grid voltage includes: If the three-phase voltage of the power system is asymmetric, select one phase voltage of the current grid voltage as the target phase voltage; Calculating the differential of the target phase voltage, and reconstructing based on the target phase voltage and the differential of the target phase voltage to obtain other two-phase voltages except the target phase voltage; The target phase voltage and the reconstructed other two-phase voltages are subjected to coordinate transformation to obtain a d-axis voltage component of the current grid voltage.

4. The inverter control method according to claim 2, It is characterized in that The step of determining a given parameter input to a control loop of the inverter based on a fault level of the power system comprises: If the power system is in a fault-free state, the given parameters input to the control loop of the inverter are all rated values; If the power system is in a minor fault state, the given parameters of the control loop input to the inverter are determined according to the grid voltage drop depth; wherein the active power given value, the reactive power regulation coefficient and the damping coefficient are positively correlated with the grid voltage drop depth, and the reactive power given value and the inertia coefficient are negatively correlated with the grid voltage drop depth.

5. The inverter control method according to claim 1, It is characterized in that The determining whether the inverter is currently in an overload state includes: Acquiring a d-axis current and / or a q-axis current in the inverter; Determining whether the d-axis current and / or the q-axis current is greater than a preset overcurrent value; If so, it is determined that the inverter is in an overload state.

6. The control method of the inverter according to any one of claims 1 to 5, It is characterized in that The calculating of a feedforward compensation amount for a control loop of the inverter includes: If the power system is in a fault-free state, based on a first proportional-integral controller, and according to the active power given value in the given parameter and the current instantaneous active power of the inverter, a first feedforward compensation amount of the active power given value is obtained; Based on the second proportional-integral controller and according to the reactive power given value in the given parameter and the current instantaneous reactive power of the inverter, a second feedforward compensation amount of the reactive power given value is obtained.

7. The inverter control method according to any one of claims 1 to 5, It is characterized in that The calculating of a feedforward compensation amount for a control loop of the inverter includes: If the power system is in a minor fault state, based on an integral controller and according to the angular frequency currently output by the inverter and the rated angular frequency, a third feedforward compensation amount of the active power given value is obtained; A fourth feedforward compensation amount of the reactive power set value is determined according to a difference between the reactive power set value and a preset reactive compensation value.

8. A control device for an inverter, It is characterized in that include: A fault determination unit, configured to determine a fault level of the power system according to a voltage drop depth of a power grid of the power system to which the inverter is connected; A given parameter determination unit, configured to determine given parameters input to a control loop of the inverter based on a fault level of the power system; the given parameters at least include an active power given value, a reactive power given value, a reactive power adjustment coefficient, an inertia coefficient, and a damping coefficient; An overload judgment unit, used to judge whether the inverter is currently in an overload state; If yes, the feedforward compensation unit is triggered; The feedforward compensation unit is used to calculate the feedforward compensation amount for the control loop of the inverter, and generate the voltage amplitude control value and the phase control value of the inverter based on the given parameters and the feedforward compensation amount.

9. An electronic device, It is characterized in that include: Memory for storing computer programs; A processor, configured to implement the steps of the inverter control method according to any one of claims 1 to 7.

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

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