Control method and device of grid-connected converter, controller, storage medium and grid-connected converter

Abstract

The invention provides a grid-connected converter control method and device, a controller, a storage medium and a grid-connected converter. The method comprises the following steps: monitoring a power grid voltage of a common coupling point of a power grid and a grid-connected converter in real time; if the power grid voltage exceeds the rated voltage range but does not exceed the high-low penetration voltage range, obtaining an active current given value according to an active power given value and an active component of a target voltage; the target voltage is any voltage value in the rated voltage range; the high-low penetrating voltage range comprises the rated voltage range; and generating a control signal of the grid-connected converter according to the active current given value. According to the method, the situation that the power grid voltage is further deteriorated due to the fact that the active current given value deviates from the normal range due to continuous deterioration of the power grid voltage can be avoided, so that the reasonability of active power transmission can be maintained, and the operation stability of the grid-connected converter under the weak power grid under the voltage fluctuation working condition can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low voltage ride through control, and particularly relates to a control method and device of a grid-connected converter, a controller, a storage medium and the grid-connected converter. BACKGROUND

[0002] With the increasing proportion of renewable energy such as wind power and photovoltaic power in the power system, the dynamic control performance of power electronic converters as the core interface of the renewable energy and the power grid plays a decisive role in the stable operation of the power grid. Especially in the areas where the power grid structure is relatively weak, the grid impedance is large and the voltage support capacity is insufficient, the converter not only needs to complete the energy transmission, but also is required to have the ability to maintain grid connection stability and actively support the grid voltage under extreme conditions such as grid fault. The robustness and dynamic performance of the control have become a key link to ensure the safety and stability of the new power system.

[0003] Under the heavy load working condition of the grid-connected converter, the weak power grid is prone to shallow overvoltage or shallow undervoltage due to load mutation, power output fluctuation and the like. If the conventional grid-connected converter control method is used in this scenario, the grid voltage is easy to further deviate, eventually deteriorating into a high penetration or low penetration scenario, affecting the system stability and grid compliance. SUMMARY

[0004] The embodiments of the present application provide a control method, device, controller and storage medium of a grid-connected converter and the grid-connected converter to solve the problem that the grid voltage is further deteriorated due to the working of the grid-connected converter under the shallow overvoltage or shallow undervoltage condition.

[0005] In a first aspect, the embodiments of the present application provide a control method of a grid-connected converter, comprising: monitoring in real time the grid voltage at a common coupling point of a power grid and the grid-connected converter; if the grid voltage exceeds the rated voltage range but does not exceed the high-low penetration voltage range, obtaining an active current given value according to an active power given value and an active component of a target voltage; the target voltage is any voltage value in the rated voltage range; the high-low penetration voltage range includes the rated voltage range; generating a control signal of the grid-connected converter according to the active current given value.

[0006] In a second aspect, the embodiments of the present application provide a control device of a grid-connected converter, comprising: a grid voltage monitoring module, configured to monitor in real time the grid voltage at a common coupling point of a power grid and the grid-connected converter; The active current given value calculation module is configured to, if the grid voltage is out of the rated voltage range but not out of the high-low penetration voltage range, obtain an active current given value according to the active power given value and an active component of a target voltage; the target voltage is any voltage value in the rated voltage range; and the high-low penetration voltage range includes the rated voltage range. The grid-connected converter control module is configured to generate a control signal of the grid-connected converter according to the active current given value.

[0007] In a third aspect, an embodiment of the present application provides a controller, including a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the control method of the grid-connected converter according to any possible implementation manner of the first aspect.

[0008] In a fourth aspect, an embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program, when executed by a processor, implements the steps of the control method of the grid-connected converter according to any possible implementation manner of the first aspect.

[0009] In a fifth aspect, an embodiment of the present application provides a grid-connected converter, including the controller according to the third aspect.

[0010] The embodiments of the present application provide a control method, device, controller, storage medium, and grid-connected converter. When it is monitored that the grid voltage is out of the rated voltage range but not out of the high-low penetration voltage range, the active component of the target voltage is used as a calculation reference of the active current given value, and the active current given value is obtained according to the active power given value and the active component of the target voltage. Since the target voltage is limited in the rated voltage range, the situation that the active current given value deviates from the normal range due to continuous deterioration of the grid voltage when the grid voltage is used to calculate the active current given value, and the grid voltage is further deteriorated, can be avoided. Therefore, the rationality of active power transmission can be maintained, the operation stability of the grid-connected converter under voltage fluctuation conditions in a weak grid can be improved, and the grid compliance and system operation continuity can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative labor.

[0012] Figure 1is an application scenario diagram of the control method of the grid-connected converter provided by the embodiment of the present application; Figure 2 is an implementation flowchart of the control method of the grid-connected converter provided by the embodiment of the present application; Figure 3 is a control loop schematic diagram of the control method of the grid-connected converter provided by the embodiment of the present application; Figure 4 is a structural schematic diagram of the control device of the grid-connected converter provided by the embodiment of the present application; Figure 5 is a schematic diagram of the controller provided by the embodiment of the present application. DETAILED DESCRIPTION

[0013] In the following description, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art should understand that the present application can be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary details.

[0014] In order to make the objects, technical solutions and advantages of the present application clearer, the following will be described by specific embodiments in conjunction with the accompanying drawings.

[0015] Figure 1 is an application scenario diagram of the control method of the grid-connected converter provided by the embodiment of the present application. As shown in Figure 1 , taking a photovoltaic grid-connected system as an example, a photovoltaic device is connected to a power grid through a grid-connected converter, and the core of the grid-connected converter to realize high-low voltage ride-through is to maintain grid connection when the grid voltage is abnormal. Usually, by rapidly detecting voltage amplitude / phase mutation, dynamically adjusting the current control strategy, it is ensured that the grid is not disconnected and the requirements of the grid on power output during ride-through are met.

[0016] However, under typical working conditions such as heavy load of charging and discharging, weak grid, etc., when the grid appears shallow overvoltage (the grid voltage is higher than the upper limit value of the rated voltage but lower than the high ride-through threshold value) or shallow under-voltage (lower than the lower limit value of the rated voltage but higher than the low ride-through threshold value), the existing conventional control method will cause a vicious cycle of voltage and current because it adopts the logic calculation of active current given value by dividing the active power given value by the real-time grid voltage active component. When the shallow under-voltage, the active current increases with the decrease of the grid voltage, resulting in an increase in grid impedance voltage drop and further drop of the grid voltage; when the shallow overvoltage, the active current decreases with the increase of the grid voltage, resulting in a decrease in grid impedance voltage drop and further rise of the grid voltage, eventually leading to deterioration of the grid voltage and misentry into the high ride-through or low ride-through state, thereby affecting the operation stability of the grid-connected converter and the grid.

[0017] In order to avoid the above problems, the application provides a control method of a grid-connected converter. The execution subject of the method is a controller of the grid-connected converter. Referring to Figure 2 The figure shows the implementation flowchart of the control method of the grid-connected converter provided by the embodiment of the application, which is described in detail as follows: S101: Real-time monitoring of the grid voltage at the point of common coupling between the grid and the grid-connected converter.

[0018] In the embodiment, the point of common coupling is the point where the grid side of the grid-connected converter is connected to the grid. The voltage sensor can be arranged at the point where the grid-connected converter is connected to the grid to collect the grid voltage.

[0019] S102: If the grid voltage is out of the rated voltage range but not out of the high-low penetration voltage range, obtaining the active current given value according to the active power given value and the active component of the target voltage; the target voltage is any voltage value in the rated voltage range; and the high-low penetration voltage range includes the rated voltage range.

[0020] In the embodiment, the rated voltage range is the most standard voltage interval when the grid is normally operated. The center value of the rated voltage range is the rated voltage of the grid, which includes the upper limit value of the rated voltage and the lower limit value of the rated voltage, and is the reference voltage interval for the safe and stable operation of the power equipment.

[0021] The high-low penetration voltage range is the maximum voltage range interval when the grid is normally operated, the upper limit of which is the high penetration threshold value, and the lower limit of which is the low penetration threshold value; and the range covers the rated voltage range. When the grid voltage is higher than the high penetration threshold value, the grid-connected converter enters the high voltage penetration stage; and when the grid voltage is lower than the low penetration threshold value, the grid-connected converter enters the low voltage penetration stage.

[0022] When the controller monitors that the grid voltage exceeds the rated voltage range but does not exceed the high-low voltage ride-through range, it indicates that the grid voltage is in the shallow overvoltage / under-voltage stage, that is, the grid voltage is about to be overvoltage / under-voltage, but is still in the normal voltage range interval. In the conventional control strategy, when the grid voltage is in the normal voltage range, the controller usually determines the active power given value based on the power scheduling instruction issued by the upper level, and then divides the active power given value by the actual value of the grid voltage to obtain the active current given value, and then controls the grid-connected converter based on the active current given value. However, when the grid voltage is in the shallow under-voltage stage, if the actual value of the grid voltage is used to calculate the active current given value, the active current given value will increase when the active power given value remains unchanged and the grid voltage decreases, which will further reduce the grid voltage and lead to the low voltage ride-through stage. When the grid voltage is in the shallow over-voltage stage, if the actual value of the grid voltage is used to calculate the active current given value, the active current given value will decrease when the active power given value remains unchanged and the grid voltage increases, which will further increase the grid voltage and lead to the high voltage ride-through stage.

[0023] The controller provided in this embodiment avoids the above situation by calculating the active current given value based on the active power given value and the target voltage when the grid voltage is in the shallow over-voltage or shallow under-voltage state. Since the target voltage will not exceed the rated voltage range, the active current given value will not continue to deviate from the normal range, thereby ensuring the stability of the grid voltage.

[0024] Specifically, when the grid voltage is higher than the upper limit of the rated voltage and less than the high voltage ride-through threshold, the controller can use the upper limit of the rated voltage as the target voltage. When the grid voltage is lower than the lower limit of the rated voltage and greater than the low voltage ride-through threshold, the controller can use the lower limit of the rated voltage as the target voltage, which can avoid further deterioration of the grid voltage and the problem of large difference between the target voltage and the actual value of the grid voltage leading to the jump of the active current given value.

[0025] S103: generating a control signal of the grid-connected converter according to the active current given value.

[0026] In this embodiment, Figure 3 The control loop diagram of the control method of the grid-connected converter provided in this embodiment is shown, and the grid voltage is monitored Figure 3 , and the active power given value is divided by the target voltage U k to obtain the active current given value I k_d . d_ref After obtaining the active current given value , the reactive current given value may be determined based on the grid voltage.

[0027] Then the output current actual value Io of the grid-connected converter is obtained in the reactive current loop, and the output current actual value is converted from abc coordinate system to dq coordinate system to obtain the active current actual value I d_fdb and the reactive current actual value I q_fdb ; then the given value of the reactive current I q_ref is subtracted from the reactive current actual value I q_fdb to obtain the reactive current difference value, and the reactive current difference value is input into a PI controller to obtain the output of the reactive current loop. In the active current loop, the given value of the active current I is subtracted from the active current actual value I d_fdb to obtain the active current difference value; the active current difference value is input into a PI controller to obtain the output of the active current loop.

[0028] In the reactive voltage loop, the output of the reactive current loop is taken as the given value of the reactive voltage U q_ref , and the given value of the reactive voltage U q_ref is subtracted from the reactive voltage actual value U q_fdb to obtain the reactive voltage difference value, and the reactive voltage difference value is input into a PI controller to obtain the reactive control value. The reactive voltage actual value U q_fdb is obtained by converting the grid voltage with the negative sequence component removed from the abc coordinate system to the dq axis.

[0029] In the active voltage loop, the output of the active current loop is taken as the given value of the active voltage U , and the given value of the active voltage U is subtracted from the active voltage actual value U d_fdb to obtain the active voltage difference value, and the active voltage difference value is input into another PI controller to obtain the active control value. The active voltage actual value U d_fdb is obtained by converting the grid voltage with the negative sequence component removed from the abc coordinate system to the dq axis.

[0030] Finally, the active control value and the reactive control value are converted to the abc coordinate system to obtain the final control value, and then the final control value is used to generate the PWM (Pulse Width Modulation) signal for controlling the grid-connected converter.

[0031] As can be seen from the above embodiment, when it is monitored that the grid voltage exceeds the rated voltage range but does not exceed the high-low ride-through voltage range, the active component of the target voltage is used as the calculation reference of the active current given value, and the active current given value is obtained according to the active power given value and the active component of the target voltage. Since the target voltage is limited in the rated voltage range, the situation that the active current given value deviates from the normal range due to continuous deterioration of the grid voltage when the grid voltage is used to calculate the active current given value, so as to further deteriorate the grid voltage, can be avoided. Therefore, the rationality of active power transmission can be maintained, the operation stability of the grid-connected converter under voltage fluctuation working condition in a weak grid can be improved, and the grid compliance and system operation continuity can be ensured.

[0032] In a possible implementation, the rated voltage range includes a rated voltage lower limit value, and the high-low ride-through voltage range includes a low ride-through threshold value; and the low ride-through threshold value is less than the rated voltage lower limit value. The specific implementation process of S102 includes: If the grid voltage is lower than the rated voltage lower limit value and greater than the low ride-through threshold value, the active power given value is divided by the active component of the rated voltage to obtain the active current given value.

[0033] In this embodiment, the active component of the rated voltage is the d-axis component of the rated voltage in the dq synchronous rotating coordinate system, which is an effective voltage component of active power transmission.

[0034] When it is monitored that the grid voltage is lower than the rated voltage lower limit value and greater than the low ride-through threshold value, the controller determines that the grid voltage is in the shallow under-voltage interval. For the shallow under-voltage interval, the controller calculates the active current given value by dividing the active power given value by the active component of the rated voltage, instead of the active component of the actual value of the irregular grid voltage. This avoids the vicious cycle of “voltage reduction→current increase→voltage further drop” in the shallow under-voltage state, limits the excessive increase of the active current by fixing the calculation reference, and ensures that the grid voltage is stable in the shallow under-voltage interval, without triggering unnecessary low voltage ride-through mode.

[0035] In a possible implementation, the low ride-through threshold value can also be determined based on the grid short circuit ratio (SCR) in this embodiment, and the grid short circuit ratio and the low ride-through threshold value are positively correlated, that is, the greater the grid short circuit ratio, the higher the low ride-through threshold value. The grid short circuit ratio is the ratio of the grid short circuit capacity to the rated capacity of the converter, which is a core index for measuring the strength of the grid. The smaller the short circuit ratio, the weaker the grid.

[0036] Specifically, in order to improve the calculation efficiency, the embodiment divides the power grid into a weak power grid, a medium-intensity power grid and a strong power grid according to the size of the short circuit ratio (SCR) value of the power grid; wherein, when the SCR value is less than a first value, it is determined as a weak power grid, when the SCR value is greater than or equal to the first value and less than a second value, it is determined as a medium-intensity power grid, and when the SCR value is greater than or equal to the second value, it is determined as a strong power grid. The first value is less than the second value. Exemplarily, the first value can be 2, and the second value can be 3. The controller can determine the type of the current power grid according to the SCR value of the current power grid, and then determine the corresponding low penetration threshold value based on the type of the power grid. A higher low penetration threshold value is set in the strong power grid, because the voltage support capability is strong and the voltage fluctuation is small in the strong power grid, the voltage drop depth is shallow when low penetration, so a higher low penetration threshold value can be set to improve the sensitivity of low voltage penetration fault detection. A lower low penetration threshold value is set in the weak power grid, because the voltage support capability is weak and the voltage fluctuation is large in the weak power grid, so a lower low penetration threshold value is set to avoid non-fault false triggering of low voltage penetration fault.

[0037] From the above embodiment, it can be seen that the embodiment calculates the active current given value by dividing the active power given value by the active component of the rated voltage in the shallow under-voltage interval. The excessive increase of the active current is effectively limited, the grid voltage is avoided from being continuously pulled down, the problem of non-fault false entry into low penetration is fundamentally eliminated, the method not only guarantees the reasonable output of active power of the grid-connected converter under the shallow under-voltage condition, but also avoids the damage of current overshoot to the switching device such as IGBT (Insulated Gate Bipolar Transistor), improves the voltage support capability and operation robustness of the grid-connected converter under the weak power grid, and ensures that the system can still be stably connected to the grid when the grid is slightly under-voltage.

[0038] In one possible implementation, the rated voltage range includes an upper limit value of the rated voltage, and the high-low penetration voltage range includes a high penetration threshold value; and the high penetration threshold value is greater than the upper limit value of the rated voltage; The specific implementation process of S102 includes: If the grid voltage is greater than the upper limit value of the rated voltage and less than the high penetration threshold value, the active current given value is obtained by dividing the active power given value by the active component of the rated voltage.

[0039] Specifically, when the grid voltage is higher than the upper limit of the rated voltage and less than the high penetration threshold, the embodiment determines that the grid voltage is in the shallow overvoltage interval. For the shallow overvoltage interval, the controller calculates the active current given value by dividing the active power given value by the active component of the rated voltage, instead of the active component of the actual grid voltage. This avoids the vicious cycle of "voltage rising → current decreasing → voltage further rising" in the shallow overvoltage interval, limits the excessive decrease of the active current by fixing the calculation reference, and ensures that the grid voltage is stable in the shallow overvoltage interval and does not trigger unnecessary high voltage penetration mode.

[0040] In one possible implementation, the embodiment can also determine the high penetration threshold based on the grid short circuit ratio (SCR), and the grid short circuit ratio is negatively correlated with the high penetration threshold, that is, the larger the grid short circuit ratio, the smaller the high penetration threshold.

[0041] Specifically, when calculating the high penetration threshold, the grid strength type can also be distinguished based on the SCR value. The controller can determine the type to which the current grid belongs according to the SCR value of the current grid, and then determine the corresponding high penetration threshold based on the grid type. A lower high penetration threshold is set in a strong grid, because the voltage support capability is strong and the voltage fluctuation is small in a strong grid, so a lower high penetration threshold can be set to improve the sensitivity of high voltage penetration fault detection. A higher high penetration threshold is set in a weak grid, because the voltage support capability is weak and the voltage fluctuation is large in a weak grid, so a higher high penetration threshold is set to avoid non-fault triggering of high voltage penetration fault.

[0042] As can be seen from the above embodiment, for the shallow overvoltage interval, the active component of the rated voltage is used as the calculation reference of the active current given value, so that the active current given value remains stable, the voltage deterioration caused by excessive current reduction is avoided, and the grid voltage is ensured to be stable in the shallow overvoltage interval without reaching the high penetration threshold. This method not only protects the switching devices of the grid-connected converter from overvoltage stress damage, but also avoids unnecessary high penetration mode start, improves system operation continuity, and at the same time maintains reasonable active power output.

[0043] In one possible implementation, the specific implementation process of S102 includes: If the grid voltage exceeds the rated voltage range but does not exceed the high-low penetration voltage range, and the grid short circuit ratio is less than a first preset threshold, the active current given value is obtained according to the active power given value and the active component of the target voltage.

[0044] Specifically, in a weak grid, the grid impedance is large, the coupling effect of voltage and current is stronger, and the voltage deterioration problem caused by the conventional control is more prominent when the voltage is slightly overvoltage or slightly under-voltage. The embodiment is targeted at the weak grid scenario, and the target voltage active component is used to calculate the active current given value, which not only avoids the interference of real-time voltage fluctuation on current control, but also suppresses the dramatic change of grid impedance voltage drop through stable active current, effectively blocks the voltage deterioration path, and improves the operation stability of the grid-connected converter in the weak grid.

[0045] In one possible implementation, in the under-voltage scenario, the specific implementation process of S102 includes: if the grid voltage is lower than the lower limit of the rated voltage but not lower than the low penetration threshold, and the grid short-circuit ratio is less than the first preset threshold, the active current given value is obtained according to the active power given value and the active component of the target voltage; at the same time, the reactive current given value is generated according to the difference between the grid voltage and the low penetration threshold, and the smaller the difference between the grid voltage and the low penetration threshold, the greater the reactive current given value.

[0046] Specifically, while avoiding the active current given value from continuously increasing to cause the grid voltage to drop into the low voltage ride-through stage, the embodiment can also support the grid voltage by increasing the reactive current given value, thereby avoiding the grid voltage from dropping into the low voltage ride-through stage.

[0047] In one possible implementation, the further implementation process of S102 includes: If the grid voltage exceeds the rated voltage range but does not exceed the high-low penetration voltage range, and the grid short-circuit ratio is less than the first preset threshold, and the grid load rate is greater than the first load rate threshold, the active current given value is obtained according to the active power given value and the active component of the target voltage.

[0048] Specifically, the grid load rate is the ratio of the actual load of the grid to the rated load, and the higher the load rate, the greater the power pressure of the grid, and the worse the voltage stability.

[0049] In the embodiment, in the heavy load working condition, the active power given value of the grid-connected converter is at a high level, and the influence of current change on the grid voltage is significantly amplified; and the low voltage support capability of the weak grid further aggravates the coupling deterioration. The embodiment only uses the target voltage active component to calculate the active current given value in this high-risk scenario, which fixes the current control reference, avoids the excessive change of active current with real-time voltage, and suppresses the cumulative increase of grid impedance voltage drop through stable current, thereby blocking the deterioration path from slight overvoltage / slight under-voltage to high-low penetration from the root, and ensuring the stable operation of the system in complex and severe working conditions. At the same time, in other non-severe grid scenarios, the conventional grid voltage actual value is continued to be used to calculate the active current given value, so as to ensure the power tracking accuracy and improve the control accuracy.

[0050] In one possible implementation, the method provided in this embodiment further includes: If the grid voltage does not exceed the rated voltage range, the active power given value is divided by the active component of the grid voltage to obtain the active current given value. If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then before obtaining the active current setpoint based on the active power setpoint and the active component of the target voltage, the method provided in this embodiment further includes: The first voltage is gradually adjusted from the grid voltage to the target voltage, and the active power setpoint is divided by the active component of the first voltage to obtain the active current setpoint.

[0051] In this embodiment, the first voltage is an intermediate voltage variable during the transition process, used to achieve a smooth transition of the grid voltage from the current actual value to the target voltage, and to avoid current oscillations caused by voltage sudden changes.

[0052] Specifically, this embodiment uses conventional logic to ensure power point tracking accuracy when the grid voltage is within the rated voltage range. When the grid voltage is in a slightly over-voltage / slightly under-voltage range, a transition mechanism is added to gradually adjust the first voltage to the target voltage. During the transition, the active current setpoint is calculated based on the active component of the first voltage. This method not only solves the voltage degradation problem under special operating conditions, but also avoids current surges and system oscillations during range switching through gradual transition, achieving multi-objective optimization of control accuracy, stability, and smoothness.

[0053] In this embodiment, the controller can also determine the transition time based on the rate of change of the grid voltage and the deviation from the rated voltage. The greater the rate of change of the grid voltage, the longer the transition time; the greater the deviation from the rated voltage, the longer the transition time. Finally, the calculated transition time is limited by a preset time limit to obtain a limited transition time. When the controller detects that the grid voltage exceeds the rated voltage range but does not exceed the high / low voltage range, it linearly adjusts the first voltage from the grid voltage to the target voltage within the limited transition time to avoid sudden current changes during interval switching.

[0054] As can be seen from the above embodiments, this embodiment achieves adaptive switching of control logic by distinguishing between different operating conditions: "the grid voltage does not exceed the rated voltage range" and "it exceeds the rated voltage range but does not exceed the high-low voltage range". Under normal operating conditions, the current setpoint is calculated using the active component of the real-time grid voltage to ensure power tracking accuracy. Under special operating conditions, a transition mechanism of "gradually adjusting the first voltage from the grid voltage to the target voltage" is added, and the active current setpoint is calculated based on the active component of the first voltage. This solves the voltage degradation problem of conventional control under special operating conditions, and avoids system oscillations caused by sudden changes in the active current setpoint through gradual transition, thus improving control smoothness. At the same time, locking the target voltage within the rated voltage range ensures the rationality of the active current setpoint and effectively prevents accidental high-low voltage crossing.

[0055] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0056] The following are device embodiments of the present invention. For details not described in detail, please refer to the corresponding method embodiments described above.

[0057] Figure 4 A schematic diagram of the low-voltage ride-through control device provided in an embodiment of the present invention is shown. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below: like Figure 4 As shown, the control device 100 of the grid-connected converter includes: The grid voltage monitoring module 110 is used to monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time. The active current setpoint calculation module 120 is used to calculate the active current setpoint based on the active power setpoint and the active component of the target voltage if the grid voltage exceeds the rated voltage range but does not exceed the high and low breakdown voltage range; the target voltage is any voltage value in the rated voltage range; the high and low breakdown voltage range includes the rated voltage range. The grid-connected converter control module 130 is used to generate control signals for the grid-connected converter based on the given active current value.

[0058] In one possible implementation, the rated voltage range includes a lower limit of the rated voltage, and the high and low breakdown voltage range includes a low breakdown threshold; and the low breakdown threshold is less than the lower limit of the rated voltage. The active current setpoint calculation module 120 is specifically used for: If the grid voltage is lower than the lower limit of the rated voltage but greater than the low penetration threshold, the active power given value is divided by the active component of the rated voltage to obtain the active current given value.

[0059] In one possible implementation, the rated voltage range includes an upper limit value of the rated voltage, the high and low breakdown voltage range includes a high breakdown threshold value, and the high breakdown threshold value is greater than the upper limit value of the rated voltage. The active current setpoint calculation module 120 is specifically used for: If the grid voltage is greater than the upper limit of the rated voltage and less than the high penetration threshold, the active power given value is divided by the active component of the rated voltage to obtain the active current given value.

[0060] In one possible implementation, the active current setpoint calculation module 120 is specifically used for: If the grid voltage exceeds the rated voltage range but does not exceed the high and low breakdown voltage range, and the grid short-circuit ratio is less than the first preset threshold, then the active current setpoint is obtained based on the active power setpoint and the active component of the target voltage.

[0061] In one possible implementation, the active current setpoint calculation module 120 is further configured to: If the grid voltage exceeds the rated voltage range but does not exceed the high and low breakdown voltage range, and the grid short-circuit ratio is less than the first preset threshold, and the grid load rate is greater than the first load rate threshold, then the active current setpoint is obtained based on the active power setpoint and the active component of the target voltage.

[0062] In one possible implementation, the control device of the grid-connected converter further includes a conventional current setpoint calculation module, used for: If the grid voltage does not exceed the rated voltage range, the active power given value is divided by the active component of the grid voltage to obtain the active current given value. If the grid voltage exceeds the rated voltage range but does not exceed the high / low voltage range, then before obtaining the active current setpoint based on the active power setpoint and the active component of the target voltage, the active current setpoint calculation module is also used for: The first voltage is gradually adjusted from the grid voltage to the target voltage, and the active power setpoint is divided by the active component of the first voltage to obtain the active current setpoint.

[0063] Figure 5 This is a schematic diagram of the controller provided in an embodiment of the present invention. Figure 5As shown, the controller 5 in this embodiment includes a processor 50, a memory 51, and a computer program 52 stored in the memory 51 and executable on the processor 50. When the processor 50 executes the computer program 52, it implements the steps in the control method embodiments of the various grid-connected converters described above, for example... Figure 2 Steps S101 to S103 are shown. Alternatively, when the processor 50 executes the computer program 52, it implements the functions of each module / unit in the above-described device embodiments.

[0064] For example, the computer program 52 may be divided into one or more modules / units, which are stored in the memory 51 and executed by the processor 50 to complete the present invention. The one or more modules / units may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program 52 in the controller 5.

[0065] The controller 5 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. The controller 5 may include, but is not limited to, a processor 50 and a memory 51. Those skilled in the art will understand that... Figure 5 This is merely an example of controller 5 and does not constitute a limitation on controller 5. It may include more or fewer components than shown, or combine certain components, or different components. For example, the controller may also include input / output devices, network access devices, buses, etc.

[0066] The processor 50 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0067] The memory 51 can be an internal storage unit of the controller 5, such as a hard disk or memory of the controller 5. The memory 51 can also be an external storage device of the controller 5, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the controller 5. Furthermore, the memory 51 can include both internal storage units and external storage devices of the controller 5. The memory 51 is used to store the computer program and other programs and data required by the controller. The memory 51 can also be used to temporarily store data that has been output or will be output.

[0068] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0069] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0070] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0071] In the embodiments provided by this invention, it should be understood that the disclosed devices / controllers and methods can be implemented in other ways. For example, the device / controller embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0072] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0073] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0074] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the control method embodiments for each of the above-described grid-connected converters. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0075] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A control method for a grid-connected converter, characterized in that, include: Real-time monitoring of the grid voltage at the common coupling point between the power grid and the grid-connected converter; If the grid voltage exceeds the rated voltage range but does not exceed the high and low voltage range, the active current setpoint is obtained based on the active power setpoint and the active component of the target voltage. The target voltage is any voltage value within the rated voltage range; the high and low breakdown voltage range includes the rated voltage range. The control signal for the grid-connected converter is generated based on the given active current value.

2. The control method for a grid-connected converter according to claim 1, characterized in that, The rated voltage range includes a lower limit of the rated voltage, and the high and low breakdown voltage range includes a low breakdown threshold; and the low breakdown threshold is less than the lower limit of the rated voltage. If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then based on the active power given value and the active component of the target voltage, the active current given value is obtained, including: If the grid voltage is lower than the lower limit of the rated voltage but greater than the low penetration threshold, the active power given value is divided by the active component of the rated voltage to obtain the active current given value.

3. The control method for a grid-connected converter according to claim 1, characterized in that, The rated voltage range includes the upper limit of the rated voltage, and the high and low breakdown voltage range includes the high breakdown threshold; and the high breakdown threshold is greater than the upper limit of the rated voltage. If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then based on the active power given value and the active component of the target voltage, the active current given value is obtained, including: If the grid voltage is greater than the upper limit of the rated voltage and less than the high penetration threshold, the active power given value is divided by the active component of the rated voltage to obtain the active current given value.

4. The control method for a grid-connected converter according to claim 1, characterized in that, If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then based on the active power given value and the active component of the target voltage, the active current given value is obtained, including: If the grid voltage exceeds the rated voltage range but does not exceed the high and low breakdown voltage range, and the grid short-circuit ratio is less than the first preset threshold, then the active current setpoint is obtained based on the active power setpoint and the active component of the target voltage.

5. The control method for a grid-connected converter according to claim 1, characterized in that, If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then based on the active power given value and the active component of the target voltage, the active current given value is obtained, including: If the grid voltage exceeds the rated voltage range but does not exceed the high and low breakdown voltage range, and the grid short-circuit ratio is less than the first preset threshold, and the grid load rate is greater than the first load rate threshold, then the active current setpoint is obtained based on the active power setpoint and the active component of the target voltage.

6. The control method for a grid-connected converter according to claim 1, characterized in that, The method further includes: If the grid voltage does not exceed the rated voltage range, the active power given value is divided by the active component of the grid voltage to obtain the active current given value. If the grid voltage exceeds the rated voltage range but does not exceed the high / low breakdown voltage range, then before obtaining the active current setpoint based on the active power setpoint and the active component of the target voltage, the method further includes: The first voltage is gradually adjusted from the grid voltage to the target voltage, and the active power setpoint is divided by the active component of the first voltage to obtain the active current setpoint.

7. A control device for a grid-connected converter, characterized in that, include: The grid voltage monitoring module is used to monitor the grid voltage at the common coupling point between the grid and the grid-connected converter in real time. The active current setpoint calculation module is used to obtain the active current setpoint based on the active power setpoint and the active component of the target voltage if the grid voltage exceeds the rated voltage range but does not exceed the high and low voltage range. The target voltage is any voltage value within the rated voltage range; the high and low breakdown voltage range includes the rated voltage range. The grid-connected converter control module is used to generate control signals for the grid-connected converter based on the given active current value.

8. A controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the control method for the grid-connected converter as described in any one of claims 1 to 6.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the control method for the grid-connected converter as described in any one of claims 1 to 6.

10. A grid-connected converter, characterized in that, include: The controller as described in claim 8.

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