Current control method, system and converter

Abstract

This application discloses a current control method, system, and converter, belonging to the field of substation control technology. The method includes: determining the current deviation based on the initial current command value and current sample value of the converter in the current operating mode; determining the command correction state based on the current deviation and a preset current threshold value; determining the target current command value based on the command correction state and the current deviation; and controlling the converter current based on the target current command value and the current sample value. This application achieves the goal of balancing current tracking speed and transient stability in the converter by adaptively adjusting the target current command value according to the current tracking state.

Description

Technical Field

[0001] This application relates to the field of power substation control technology, specifically to a current control method, system, and converter. Background Technology

[0002] Converters are widely used in new energy power generation, flexible DC transmission, and energy storage, typically achieving power conversion and regulation through current control. Due to delays in current sampling, control calculations, and switching modulation, the actual current of the converter lags behind the response to current commands. When current commands change, or when external operating conditions such as the power grid or load are disturbed, the actual current may struggle to keep up with the current commands in a timely manner.

[0003] In the transient control of converters, it is often difficult to balance improving the current response speed and suppressing current overshoot. A slow response will affect the converter's ability to quickly support the grid or load, while current overshoot may trigger protection actions and even increase the risk of power device damage and converter shutdown. Summary of the Invention

[0004] This invention provides a current control method, system, and converter, aiming to solve the problem of balancing the improvement of current response speed and the suppression of current overshoot in the transient control process of related converters.

[0005] Firstly, a current control method is provided, comprising the following steps: The current deviation is determined based on the initial current command value and current sample value of the converter in the current operating mode; The command correction state is determined based on the current deviation and the preset current threshold value; The target current command value is determined based on the command correction status and the current deviation; The current of the converter is controlled according to the target current command value and the current sample value.

[0006] In some embodiments, the preset current threshold value includes a first current threshold value and a second current threshold value, both of which are positive numbers, and the first current threshold value is greater than the second current threshold value. The step of determining the command correction state based on the current deviation and the preset current threshold value includes: If the absolute value of the current deviation is greater than or equal to the first current threshold value, the command correction state is set to the correction state. If the absolute value of the current deviation is less than or equal to the second current threshold value, the command correction state is set to the non-correction state. If the absolute value of the current deviation is greater than the second current threshold value and less than the first current threshold value, the command correction state of the previous control cycle is maintained.

[0007] In some embodiments, the preset current threshold value is a third current threshold value, and the third current threshold value is a positive number; The step of determining the command correction state based on the current deviation and the preset current threshold value includes: If the absolute value of the current deviation is greater than or equal to the third current threshold value, the command correction state is set to the correction state. If the absolute value of the current deviation is less than the third current threshold value, the command correction state is set to the non-correction state.

[0008] In some embodiments, determining the target current command value based on the command correction state and the current deviation includes: When the command correction state is in the correction state, a correction amount is generated based on the current deviation; the initial current command value is corrected using the correction amount to determine the target current command value; When the command correction state is in the non-correction state, the initial current command value is determined as the target current command value.

[0009] In some embodiments, generating the correction amount based on the current deviation includes: The first correction amount is generated based on the product of the current deviation and the preset current deviation correction coefficient; The current deviation correction coefficient is a positive number, and the value of the current deviation correction coefficient is determined based on at least one of the current response speed of the converter, the current deviation, the sampling and control delay, and the allowable overshoot.

[0010] In some embodiments, generating the correction amount based on the current deviation includes: When the current deviation is greater than zero, a second correction amount is determined based on a preset first current compensation factor, wherein the first current compensation factor is a positive number, and the value of the first current compensation factor is determined based on at least one of the current response speed of the converter, the current deviation, the allowable overshoot degree, and the positive response characteristics of the converter. When the current deviation is less than zero, the second correction amount is determined based on a preset second current compensation factor, wherein the second current compensation factor is a negative number, and the absolute value of the second current compensation factor is determined based on at least one of the current response speed of the converter, the current deviation, the allowable overshoot, and the negative response characteristics of the converter.

[0011] In some embodiments, the target current command value and the current sample value are current quantities in a target coordinate system, wherein the target coordinate system is an abc coordinate system, an αβ coordinate system, or a dq coordinate system. The step of controlling the current of the converter based on the target current command value and the current sample value includes: In the target coordinate system, the control quantity is determined based on the target current command value and the current sample value; The three-phase modulation signal is determined based on the control quantity, and the converter is modulated according to the three-phase modulation signal.

[0012] In some embodiments, determining a control quantity based on the target current command value and the current sample value includes: The current control deviation is obtained by subtracting the target current command value from the current sample value. The current control deviation is subjected to proportional and integral calculations respectively, and the sum of the proportional and integral calculation results is determined as the control quantity; Alternatively, proportional and resonant calculations can be performed on the current control deviation, and the sum of the proportional and resonant calculation results can be determined as the control quantity.

[0013] Secondly, this application provides a current control system, comprising: The current acquisition module is used to determine the current deviation based on the initial current command value and the current sample value of the converter in the current operating mode; The status determination module is used to determine the command correction status based on the current deviation and the preset current threshold value; The instruction correction module is used to determine the target current instruction value based on the instruction correction status and the current deviation. The current control module is used to control the current of the converter according to the target current command value and the current sample value.

[0014] Thirdly, this application provides a converter including a power conversion circuit and a controller, the controller being configured to perform the current control method described in any of the preceding claims.

[0015] Fourthly, a computer-readable storage medium is also provided, on which a computer program is stored, the computer program being loaded by a processor to execute the steps in any of the above-mentioned current control methods.

[0016] Beneficial effects: This application determines the current deviation based on the initial current command value and the current sampled value of the converter in the current operating mode. It can characterize the tracking degree of the actual current relative to the current control target in real time, and determine the command correction state by comparing the current deviation with a preset current threshold value, so that the target current command value is adaptively adjusted according to the current tracking state. Therefore, when the deviation between the actual current and the initial current command value is large, it can enhance the effect of driving the actual current to approach the control target, and improve the converter's response speed to command changes, grid disturbances, or load changes. At the same time, when the actual current is close to the control target, it can reduce unnecessary command corrections and reduce the risk of current overshoot caused by continuous regulation, thereby achieving a balance between current tracking speed and transient stability in the converter. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart of a current control method provided by an exemplary embodiment of this disclosure; Figure 2 This is a block diagram of an adaptive acceleration control signal interaction provided by an exemplary embodiment of this disclosure; Figure 3 This is a schematic diagram of current control logic provided by an exemplary embodiment of this disclosure; Figure 4 This is another schematic diagram of current control logic provided by an exemplary embodiment of this disclosure; Figure 5 This is a schematic diagram of the ABC coordinate system; Figure 6 This is a schematic diagram of the αβ coordinate system; Figure 7 This is a schematic diagram of the dq coordinate system; Figure 8 This is a schematic diagram of the control logic of a PI controller provided in an exemplary embodiment of this disclosure; Figure 9 This is a schematic diagram of the control logic of a PR controller provided in an exemplary embodiment of this disclosure; Figure 10 This is a schematic diagram of the overall flow of a current control method provided by an exemplary embodiment of this disclosure; Figure 11 This is a schematic diagram of a current control system provided by an exemplary embodiment of the present disclosure. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to needs to have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0021] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0022] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not preclude applicability to or configuration to devices performing additional tasks or steps. Furthermore, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more conditions or values ​​may in practice be based on additional conditions or values ​​beyond those conditions.

[0023] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0024] On the one hand, this embodiment provides a current control method; please refer to [link / reference]. Figure 1 This includes the following steps: Step 100: Determine the current deviation based on the initial current command value and current sample value of the converter in the current operating mode.

[0025] Specifically, the initial current command value, adapted to the current operating condition of the converter, is first read from the upper layer. Simultaneously, the actual operating current sample value on the converter output side is acquired in real time via a hardware sampling circuit. The current operating mode characterizes the current control target or operating condition of the converter. The initial current command value is the current setpoint in this operating mode before undergoing the command correction processing of this embodiment. The current sample value is the feedback value obtained by sampling the actual current of the converter. Then, the initial current command value and the current sample value are compared using the same current representation format to obtain the current deviation, which characterizes the degree and direction of their difference.

[0026] Step 200: Determine the command correction status based on the current deviation and the preset current threshold value.

[0027] Specifically, the current deviation is compared with a preset current threshold value, and the command correction state is determined based on the comparison result. The preset current threshold value characterizes the allowable deviation range between the initial current command value and the current sample value. If the current deviation indicates that the deviation of the current sample value from the initial current command value has reached a level requiring command adjustment, the command correction state is determined to be in a correction state; if the current deviation indicates that the deviation is within the range where no command adjustment is needed, the command correction state is determined to be in a non-correction state. Thus, whether to intervene in command correction can be dynamically determined based on the actual current tracking situation.

[0028] Step 300: Determine the target current command value based on the command correction status and current deviation.

[0029] Specifically, when the command correction state indicates that the current command needs adjustment, the initial current command value can be corrected accordingly based on the direction and degree of deviation reflected by the current deviation. This corrected current command enhances the driving effect of the actual current changing towards the desired current. When the command correction state indicates that no command adjustment is needed, the target current command value can be kept consistent with or substantially consistent with the initial current command value. Through this process, the target current command value can be adaptively determined according to the tracking status of the actual current of the converter.

[0030] Step 400: Control the current of the converter according to the target current command value and the current sampling value.

[0031] Specifically, the target current command value is used as the setpoint for current control, and the sampled current value is used as the feedback value for current control. The difference between these two values ​​forms the control action used to adjust the converter current, causing the actual converter current to change towards the target current command value. Since the target current command value is determined by combining the command correction state and the current deviation, it can improve the speed at which the actual current follows the command change when the current deviation is large, and reduce unnecessary command adjustments when the current deviation is small, thus balancing current response speed and current control stability.

[0032] This embodiment determines the current deviation based on the initial current command value and the current sample value of the converter in the current operating mode. It can characterize the tracking degree of the actual current relative to the current control target in real time, and determine the command correction state by comparing the current deviation with a preset current threshold value, so that the target current command value is adaptively adjusted according to the current tracking state. Therefore, when the deviation between the actual current and the initial current command value is large, it can enhance the effect of driving the actual current to approach the control target, and improve the converter's response speed to command changes, grid disturbances or load changes. At the same time, when the actual current is close to the control target, it can reduce unnecessary command corrections and reduce the risk of current overshoot caused by continuous adjustment, thereby achieving a balance between current tracking speed and transient stability in the converter.

[0033] In some embodiments, the preset current threshold values ​​include a first current threshold value and a second current threshold value, both of which are positive numbers, and the first current threshold value is greater than the second current threshold value. Step 200, determining the command correction state based on the current deviation and the preset current threshold value, includes: Step 210: If the absolute value of the current deviation is greater than or equal to the first current threshold value, set the command correction state to the correction state.

[0034] Specifically, the absolute value of the current deviation obtained in the current control cycle is compared with a first current threshold value. When the absolute value of the current deviation is greater than or equal to the first current threshold value, it indicates that the deviation between the initial current command value and the current sample value has reached a large range, and the actual current is significantly insufficient in tracking the expected current. At this time, the command correction state is set to correction state, and the preset current adaptive acceleration control logic is enabled, so that the magnitude of the target current command value can be processed accordingly based on the correction state and the current deviation, thereby improving the converter current's response capability to changes in the expected value.

[0035] Step 220: If the absolute value of the current deviation is less than or equal to the second current threshold value, set the command correction state to the non-correction state.

[0036] Specifically, the absolute value of the current deviation obtained in the current control cycle can be compared with the second current threshold value. When the absolute value of the current deviation is less than or equal to the second current threshold value, it indicates that the deviation between the initial current command value and the current sample value has been reduced to a small range, and the actual current is close to the expected current in the current operating mode. At this time, the command correction state is set to the non-correction state, so there is no need to adjust the initial current command value, thereby reducing the risk of over-adjustment caused by continuing to correct when the current is close to the expected value.

[0037] Step 230: If the absolute value of the current deviation is greater than the second current threshold value and less than the first current threshold value, maintain the command correction state of the previous control cycle.

[0038] Specifically, when the absolute value of the current deviation in the current control cycle is greater than the second current threshold value but less than the first current threshold value, it can be determined that the current deviation is within the transition range between the first and second current threshold values. Since this transition range neither meets the conditions for entering nor exiting the correction state, the current command correction state is not changed again; instead, the command correction state of the previous control cycle is used as the command correction state for the current control cycle. This maintains state continuity when the current deviation is near the threshold, avoiding frequent switching of the command correction state due to current sampling fluctuations or small changes in deviation.

[0039] For example, the initial current command value of the converter is set to... The real-time current sampling value of the converter is Calculate the current deviation between the initial current command value and the current sample value. ,Right now: (1); Set the first current threshold value. Set a second current threshold value ,and .

[0040] Real-time computing absolute value ,Right now: (2); Set the flag of the trigger current adaptive acceleration control logic to and according to and , Size relationship, comprehensive control The possible values ​​of include: exist Greater than or equal to In this case, let .

[0041] exist Less than or equal to In this case, let .

[0042] exist Greater than and less than In this case, detect the previous control cycle. Value. In the previous control cycle. If the value is 1, then the current control cycle continues to allow In the previous control cycle If the value is 0, then the current control cycle continues. This example demonstrates how to set two current threshold values ​​and reference the previous control cycle. Value, which can reduce the impact on Adjusting the frequency helps improve the stability of converter control.

[0043] Then, in In this case, the current adaptive acceleration control logic is triggered. In this case, the current adaptive acceleration control logic is exited.

[0044] Please see Figure 2 , Figure 2 This is a block diagram of the adaptive acceleration control signal interaction. This module is located at the front end of the converter's current closed-loop controller and has two input signals and one output signal, one of which is an input signal. Another input is provided to adapt the initial current command value issued by the upper layer to the current operating conditions of the converter. This refers to the sampled value of the actual output current of the converter, acquired in real time by the controller. (The last part, "in the actual output current sample value," appears to be a separate, unrelated sentence fragment.) Compared with the original initial current command value Current deviation In cases of significant deviation, the module will apply corresponding compensation to accelerate the correction of the current deviation. After scaling down, the original initial current command value is directly output. Finally, the target current command, after adaptive acceleration processing, is output to the outside. The data is then sent to the back-end closed-loop control system. It is evident that this module only performs preprocessing of the target current command, without altering the existing closed-loop control, coordinate transformation, and modulation drive control chain. It achieves improved current tracking speed and suppressed current overshoot solely by adding compensation adjustments at the command source.

[0045] This embodiment uses a first current threshold value and a second current threshold value to partition and judge the command correction state. This allows the system to enter the correction state in a timely manner when the current deviation is large, thereby enhancing the current tracking capability. When the current deviation decreases to a smaller range, the system can exit the correction state, thereby reducing unnecessary command corrections and lowering the risk of over-adjustment. When the current deviation is between the two threshold values, the system maintains the command correction state of the previous control cycle, giving the state switching hysteresis characteristics. This can suppress frequent switching of the correction state caused by sampling fluctuations, disturbances, or repeated changes in deviation near the threshold, thereby improving the response smoothness and operational stability of the converter current control.

[0046] In some embodiments, the preset current threshold value is a third current threshold value, and the third current threshold value is a positive number. Step 200, determining the command correction state based on the current deviation and the preset current threshold value, includes: Step 240: If the absolute value of the current deviation is greater than or equal to the third current threshold value, set the command correction state to the correction state.

[0047] Specifically, the absolute value of the current deviation obtained in the current control cycle can be taken and compared with the third current threshold value. When the absolute value of the current deviation is greater than or equal to the third current threshold value, it indicates that the deviation between the initial current command value and the current sample value has reached the range requiring command correction, and the actual current is significantly insufficient in tracking the expected current under the current operating mode. At this time, the command correction state is set to correction state, so that when determining the target current command value later, the initial current command value can be processed accordingly based on the current deviation, thereby improving the converter's response capability to changes in the actual current to the expected current.

[0048] Step 250: If the absolute value of the current deviation is less than the third current threshold value, set the command correction state to the non-correction state.

[0049] Specifically, the absolute value of the current deviation obtained in the current control cycle can be compared with the third current threshold value. When the absolute value of the current deviation is less than the third current threshold value, it indicates that the deviation between the initial current command value and the current sample value has not reached the range requiring command correction, and the actual current is within the allowable deviation range relative to the expected current in the current operating mode. At this time, the command correction state is set to the non-correction state, which reduces unnecessary command adjustments when determining the target current command value, thereby reducing the possibility of over-adjustment while ensuring the current tracking effect.

[0050] For example, the initial current command value of the converter is set to... The real-time current sampling value of the converter is Calculate the current deviation between the initial current command value and the current sample value. Set a unique current threshold value, called the third current threshold value. The two current threshold values ​​in the example above are equal (i.e.) (The situation is as follows.)

[0051] Set the flag of the trigger current adaptive acceleration control logic to and according to absolute value and Size relationship, control The possible values ​​of include: exist Greater than or equal to In this case, let .

[0052] exist Less than In this case, let .

[0053] Then, in In this case, the current adaptive acceleration control logic is triggered. In this case, the current adaptive acceleration control logic exits without referencing the previous control cycle. value.

[0054] This embodiment sets a positive third current threshold value and determines the command correction state based on the comparison between the absolute value of the current deviation and the third current threshold value. This allows the converter to enter the correction state when the current deviation reaches the threshold, thereby improving the tracking ability of the actual current to the desired current. When the current deviation does not reach the threshold, it enters the non-correction state, reducing unnecessary command adjustments and mitigating the risk of over-adjustment. Compared to continuous command correction, this embodiment can selectively intervene in correction based on the magnitude of the current deviation, thus balancing current response speed and control stability while maintaining relatively simple implementation logic.

[0055] In some embodiments, step 300, determining the target current command value based on the command correction state and current deviation, includes: Step 310: When the command correction state is in the correction state, generate a correction amount based on the current deviation; use the correction amount to correct the initial current command value and determine the target current command value.

[0056] Specifically, when the command correction state is in correction mode, a correction amount can be generated based on the current deviation to adjust the initial current command value. This correction amount characterizes the magnitude of the current command adjustment that needs to be increased or decreased based on the initial current command value within the current control cycle, and its direction and magnitude correspond to the actual current tracking situation represented by the current deviation. Then, this correction amount is used to correct the initial current command value to obtain the target current command value, causing an adaptive change in the target current command value relative to the initial current command value. This enhances the driving effect of the actual current towards the desired current change in the current operating mode.

[0057] Step 320: When the command correction state is in the non-correction state, determine the initial current command value as the target current command value.

[0058] Specifically, when the command correction state is in the non-correction state, the current current deviation can be considered to be within the range where command correction is not required. Therefore, the initial current command value is no longer adjusted based on the current deviation, but is directly determined as the target current command value. Through this process, when the actual current is already close to the expected current in the current operating mode, it is possible to avoid introducing additional command changes, reduce unnecessary adjustments, and thus help maintain the stability of the current control process.

[0059] This embodiment generates a correction amount based on the current deviation when the command correction state is in the correction state, and uses the correction amount to correct the initial current command value. This allows the target current command value to be adaptively adjusted according to the deviation of the actual current from the desired current. This enhances the driving effect of the actual current changing towards the desired current when the current deviation is large, and improves the current tracking response speed. At the same time, when the command correction state is in the non-correction state, the initial current command value is directly used as the target current command value, avoiding the continuous introduction of additional command changes when the current deviation is small. This reduces the risk of over-adjustment, current overshoot, or control fluctuations, thus balancing the speed and stability of converter current control.

[0060] In some embodiments, generating the correction amount based on the current deviation in step 310 includes: Step 311: Generate a first correction amount based on the product of the current deviation and the preset current deviation correction coefficient; wherein the current deviation correction coefficient is a positive number, and the value of the current deviation correction coefficient is determined based on at least one of the current response speed of the converter, the current deviation, the sampling and control delay, and the allowable overshoot.

[0061] Specifically, a preset current deviation correction coefficient can be determined first, and this coefficient should be positive. This current deviation correction coefficient characterizes the proportional relationship when the current deviation is converted into a first correction amount, and its value can be determined based on at least one of the converter's current response speed, current deviation, sampling and control delay, and allowable overshoot. Then, the current deviation obtained in the current control cycle is multiplied by the current deviation correction coefficient to obtain the first correction amount used to correct the initial current command value. Since the current deviation correction coefficient is positive, the generated first correction amount can maintain the same direction as the current deviation; when the current deviation is large, the first correction amount is correspondingly large to enhance the adjustment effect of the current command, and when the current deviation is small, the first correction amount is correspondingly small to reduce over-adjustment of the current command.

[0062] For example, please refer to Figure 3 Set the current deviation correction coefficient .exist In the case of current deviation and The first correction amount for real-time calculation of the current command value , (3); Then according to and the initial current command value is The target current command value is calculated in real time. ,Right now: (4); exist In this case, the current command value is the initial current command value. .

[0063] In summary, the target current command value It can be represented as: (5).

[0064] This embodiment generates a first correction amount by multiplying the current deviation by a positive current deviation correction coefficient. This first correction amount maintains the same direction as the current deviation and changes accordingly with the magnitude of the current deviation. This provides a stronger command correction effect and improves the current tracking response speed when the actual current deviates significantly from the expected current, while providing a weaker command correction effect and reducing the risk of over-adjustment when the deviation is small. At the same time, the value of the current deviation correction coefficient can be determined based on at least one of the converter current response speed, current deviation, sampling and control delay, and allowable overshoot, so that the first correction amount can adapt to the dynamic characteristics of different converters or different operating conditions, improving the current response speed while taking into account current overshoot suppression and control stability.

[0065] In some embodiments, generating the correction amount based on the current deviation in step 310 includes: Step 312: When the current deviation is greater than zero, determine the second correction amount based on the preset first current compensation factor, wherein the first current compensation factor is a positive number, and the value of the first current compensation factor is determined according to at least one of the current response speed of the converter, the current deviation, the allowable overshoot degree, and the positive response characteristics of the converter.

[0066] Specifically, when the current deviation is greater than zero, it can be determined that the current sampled value is in a state requiring forward compensation relative to the initial current command value. In this case, a second correction amount is determined based on a preset first current compensation factor. The first current compensation factor is a positive number, and its value can be determined based on at least one of the following: the converter's current response speed, current deviation, allowable overshoot, and the converter's forward response characteristics. For example, when it is necessary to improve the forward current response speed and the allowable overshoot is large, the value of the first current compensation factor can be increased accordingly; when it is necessary to suppress forward overshoot or the converter's forward response is fast, the value of the first current compensation factor can be decreased accordingly. Thus, the obtained second correction amount is a forward correction amount, used to positively correct the initial current command value.

[0067] Step 313: When the current deviation is less than zero, determine the second correction amount based on the preset second current compensation factor, wherein the second current compensation factor is a negative number, and the absolute value of the second current compensation factor is determined based on at least one of the current response speed of the converter, the current deviation, the allowable overshoot degree, and the negative response characteristics of the converter.

[0068] Specifically, when the current deviation is less than zero, it can be determined that the current sampled value is in a state requiring negative compensation relative to the initial current command value. In this case, a second correction amount is determined based on a preset second current compensation factor. The second current compensation factor is a negative number, and its absolute value can be determined based on at least one of the following: the converter's current response speed, current deviation, allowable overshoot, and the converter's negative response characteristics. For example, when it is necessary to improve the negative current response speed and the allowable overshoot is large, the absolute value of the second current compensation factor can be increased accordingly; when it is necessary to suppress negative overshoot or the converter's negative response is fast, the absolute value of the second current compensation factor can be decreased accordingly. Thus, the obtained second correction amount is a negative correction amount, used to negatively correct the initial current command value.

[0069] For example, please refer to Figure 4 Set the first current compensation factor Second current compensation factor ,in, It is a positive number. It is a negative number.

[0070] exist In the case of current deviation , and The second correction factor for real-time calculation of the current command value , (6); Then according to and initial current command value The target current command value is calculated in real time. ,Right now: (7); exist In this case, the current command value is the initial current command value. .

[0071] In summary, the target current command value It can be represented as: (8).

[0072] This embodiment determines a second correction amount based on a first current compensation factor and a second current compensation factor when the current deviation is greater than zero and less than zero, respectively. This allows the second correction amount to compensate positively or negatively according to the direction of the current deviation, thereby enhancing the adaptability of the target current command value to the actual current tracking deviation. At the same time, the values ​​of the first current compensation factor and the second current compensation factor are determined in combination with factors such as the positive and negative response characteristics of the converter, so that different compensation amplitudes can be used for positive and negative current changes. This adapts to the dynamic differences of the converter in different current change directions. Therefore, while improving the current response speed, it can reduce the risk of overshoot, under-regulation, or unbalanced response in a certain direction caused by a single compensation amplitude, thereby improving the precision and stability of the converter current control.

[0073] In some embodiments, the target current command value and the current sample value are the current quantities in the target coordinate system, which is the abc coordinate system, the αβ coordinate system, or the dq coordinate system.

[0074] Step 400, which controls the converter current based on the target current command value and the current sample value, includes: Step 410: In the target coordinate system, determine the control quantity based on the target current command value and the current sample value.

[0075] Specifically, the target current command value and the current sampled value can be processed in a target coordinate system, which can be an abc coordinate system, an αβ coordinate system, or a dq coordinate system. Both the target current command value and the current sampled value are current quantities in this target coordinate system. In practice, the target current command value and the current sampled value can be correlated in the same target coordinate system, and the control quantity used to adjust the converter current is determined based on the difference between them. This control quantity is used to characterize the adjustment action that needs to be applied to make the current sampled value approach the target current command value. Since the target current command value and the current sampled value are compared and processed in the same coordinate system, the consistency of the current control basis can be guaranteed, and deviations in the control quantity due to inconsistencies in coordinate representation can be avoided.

[0076] Step 420: Determine the three-phase modulation signal based on the control quantity, and modulate the converter according to the three-phase modulation signal.

[0077] Specifically, a three-phase modulation signal can be determined based on the control quantity, and the converter can be modulated according to this three-phase modulation signal. Specifically, when the control quantity obtained in the target coordinate system directly corresponds to the voltage or modulation reference quantity required for three-phase modulation, a three-phase modulation signal can be formed based on this control quantity; when the control quantity obtained in the target coordinate system is not in three-phase form, it can be converted into a form that matches three-phase modulation to form a three-phase modulation signal. By applying the three-phase modulation signal to the converter during the modulation process, the converter output current can be changed, causing the current sampling value to change towards the target current command value, thereby achieving control of the converter current.

[0078] For example, in the abc coordinate system (see...) Figure 5 In the control process, the control quantity can be superimposed on the three-phase sinusoidal modulation wave signals A, B, and C, and the converter can be modulated based on the superimposed three-phase sinusoidal modulation wave signals A, B, and C.

[0079] In the αβ coordinate system (see also...) Figure 6 In the control, the α-axis and β-axis are two mutually perpendicular stationary virtual coordinate axes. The α-axis coincides with the axis of the A-phase winding of the three-phase system, and the β-axis lags the α-axis by 90° electrical angle. The control quantity can be superimposed onto the sinusoidal voltages corresponding to the equivalent voltage components Uα and Uβ of the α-axis to represent the vector information of the three-phase voltages in the three-phase abc coordinate system through Uα and Uβ. Then, through the inverse transformation of the αβ coordinates, the three-phase sinusoidal modulation wave signal is obtained, and the converter is modulated based on this three-phase sinusoidal modulation wave signal.

[0080] In the dq coordinate system (see also...) Figure 7In the control, the d-axis is the active power oriented axis, typically aligned with the direction of the three-phase grid voltage vector; the q-axis is perpendicular to the d-axis and lags behind it by 90° electrical angle, serving as the reactive power oriented axis. Control quantities can be superimposed onto the DC voltage components Ud and Uq on the d-axis to represent the vector information of the three-phase voltages in the three-phase abc coordinate system. Ud is used to adjust the active current and active power output of the converter, while Uq adjusts the reactive current and reactive power. Then, through inverse dq coordinate transformation, a three-phase sinusoidal modulation wave signal is obtained, and the converter is modulated based on this signal.

[0081] Based on the above analysis, it can be seen that the current command correction logic of this embodiment can be applied to abc coordinate system control, αβ coordinate system control, and dq coordinate system control.

[0082] This embodiment ensures consistency between the coordinate representation of the current command and the current sample value by limiting both to the same target coordinate system and determining the control quantity within that system. This avoids inaccurate current deviation judgments or control quantity calculations due to coordinate system mismatch. Furthermore, the target coordinate system can be an abc, αβ, or dq coordinate system, allowing the current control method to adapt to different converter control architectures and current representation methods. Moreover, by determining the three-phase modulation signal based on the control quantity and modulating the converter, the current regulation result in the target coordinate system can be implemented in the actual modulation process of the converter, thereby improving the applicability, flexibility, and reliability of the current control method.

[0083] In some embodiments, determining the control quantity based on the target current command value and the current sample value in step 410 includes: Step 411: Subtract the target current command value from the current sample value to obtain the current control deviation.

[0084] Specifically, based on the target current command value and the current sample value being in the same current representation form, the difference between the target current command value and the current sample value is calculated to obtain the current control deviation. This current control deviation is used to characterize the difference between the target current command value and the actual current sample value in the current control cycle. The sign of the current control deviation reflects the direction of deviation of the actual current relative to the target current command value, and the magnitude of the current control deviation reflects the degree of deviation of the actual current relative to the target current command value. Therefore, control quantities for adjusting the converter current can be generated based on the current control deviation.

[0085] Step 412: Perform proportional and integral calculations on the current control deviation, and determine the control quantity by summing the proportional and integral calculation results; or, perform proportional and resonant calculations on the current control deviation, and determine the control quantity by summing the proportional and resonant calculation results.

[0086] Specifically, the current control deviation can be calculated to determine the control quantity. Please refer to [link / reference]. Figure 8 In one implementation, a PI controller performs proportional (P) and integral (I) calculations on the current control deviation, and the sum of the proportional and integral calculation results is used to determine the control quantity. The proportional operation is used to generate an immediate adjustment based on the current current control deviation, while the integral operation is used to generate an adjustment to eliminate steady-state deviation based on the accumulation of the current control deviation. Please refer to [link / reference]. Figure 9 In another implementation, the current control deviation is calculated using a proportional (P) and resonant (R) operation by a PR controller, and the sum of the proportional and resonant operation results is used to determine the control quantity. The proportional operation is used to provide immediate adjustment based on the current control deviation, while the resonant operation is used to provide enhanced adjustment for current control deviations at specific frequencies. Therefore, the appropriate operation method can be selected according to the current control requirements, so that the obtained control quantity can cause the actual converter current to approach the target current command value.

[0087] For example, the converter can be a two-level converter, a three-level converter, a five-level converter, a multi-level converter, a modular multi-level converter, or other converters derived from the above converters, or other converters suitable for current control. In this embodiment, the instruction correction process is located on the current instruction side. The corrected target current instruction value can still be input into the original current closed loop for control, so there is no need to change the underlying control architecture or increase additional hardware costs.

[0088] This embodiment obtains the current control deviation by subtracting the target current command value from the current sample value, and determines the control quantity based on this deviation. This allows the converter current regulation to directly correspond to the direction and degree of deviation of the actual current from the target current command value. The use of proportional and integral operations for summation balances rapid response to current deviations and suppression of steady-state deviations. The use of proportional and resonant operations for summation enhances the current deviation regulation capability at specific frequencies, making it suitable for AC current tracking scenarios. Therefore, this embodiment can generate corresponding control quantities according to different current control requirements, improving the accuracy, speed, and adaptability of the converter's actual current tracking of the target current command value.

[0089] Please see Figure 10 , Figure 10 This describes a current adaptive acceleration control process based on dual threshold values. Specifically, it involves setting an initial current command value, then acquiring real-time current samples from the converter's actual output, and calculating the absolute value of the difference between the initial current command and the sampled current values. Then, the hysteresis state is determined by three logic branches. The first branch determines whether the absolute value of the difference is greater than or equal to the first current threshold value. If the condition is met, the flag bit is set directly. 1. Enable the current adaptive acceleration control logic and generate the corrected target current command value through acceleration correction instructions. ,use Update the current command value; the third path checks whether the absolute value of the difference is less than or equal to the second current threshold value. If the condition is met, the flag bit will be set. Set to 0, exit the current adaptive acceleration control logic, and directly use the original initial current command value. When the absolute value of the difference between the intermediate branch judgments is between the two thresholds, read the previous control cycle. The state remains unchanged. If the flag from the previous control cycle is 1, the acceleration correction instruction is maintained; if the flag from the previous cycle is 0, the acceleration correction instruction is maintained. If the value is 0, the original instruction is maintained. After completing the status determination, regardless of whether the final output is a corrected instruction or the original instruction, the target current instruction value will be set. With real-time current sampling value The current is fed into the backend for closed-loop current control. This adaptive current acceleration control logic can avoid system oscillations caused by frequent switching of control modes when the difference fluctuates slightly at the threshold, achieving a balance between dynamic current tracking speed and steady-state overshoot-free operation of the converter.

[0090] On the other hand, this embodiment provides a current control system, such as Figure 11 As shown, the current control system 11 includes: The current acquisition module 111 is used to determine the current deviation based on the initial current command value and the current sample value of the converter in the current operating mode. The status determination module 112 is used to determine the command correction status based on the current deviation and the preset current threshold value; The instruction correction module 113 is used to determine the target current instruction value based on the instruction correction status and current deviation. The current control module 114 is used to control the current of the converter according to the target current command value and the current sampling value.

[0091] This embodiment also provides a converter, including a power conversion circuit and a controller, the controller being configured to execute the current control method of any of the above embodiments.

[0092] This embodiment also provides a computer-readable storage medium having a computer program stored thereon, the computer program being loaded by a processor to execute the steps of the current control method in any of the above embodiments.

[0093] In the embodiments of this application, the storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0094] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0095] The foregoing has provided a detailed description of a current control method, system, and converter provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A current control method, characterized in that, Includes the following steps: The current deviation is determined based on the initial current command value and current sample value of the converter in the current operating mode; The command correction state is determined based on the current deviation and the preset current threshold value; The target current command value is determined based on the command correction status and the current deviation; The current of the converter is controlled according to the target current command value and the current sample value.

2. The current control method according to claim 1, characterized in that, The preset current threshold values ​​include a first current threshold value and a second current threshold value, both of which are positive numbers, and the first current threshold value is greater than the second current threshold value. The step of determining the command correction state based on the current deviation and the preset current threshold value includes: If the absolute value of the current deviation is greater than or equal to the first current threshold value, the command correction state is set to the correction state. If the absolute value of the current deviation is less than or equal to the second current threshold value, the command correction state is set to the non-correction state. If the absolute value of the current deviation is greater than the second current threshold value and less than the first current threshold value, the command correction state of the previous control cycle is maintained.

3. The current control method according to claim 1, characterized in that, The preset current threshold value is a third current threshold value, and the third current threshold value is a positive number; The step of determining the command correction state based on the current deviation and the preset current threshold value includes: If the absolute value of the current deviation is greater than or equal to the third current threshold value, the command correction state is set to the correction state. If the absolute value of the current deviation is less than the third current threshold value, the command correction state is set to the non-correction state.

4. The current control method according to any one of claims 1 to 3, characterized in that, The step of determining the target current command value based on the command correction state and the current deviation includes: When the command correction state is in the correction state, a correction amount is generated based on the current deviation; the initial current command value is corrected using the correction amount to determine the target current command value; When the command correction state is in the non-correction state, the initial current command value is determined as the target current command value.

5. The current control method according to claim 4, characterized in that, The step of generating a correction amount based on the current deviation includes: The first correction amount is generated based on the product of the current deviation and the preset current deviation correction coefficient; The current deviation correction coefficient is a positive number, and the value of the current deviation correction coefficient is determined based on at least one of the current response speed of the converter, the current deviation, the sampling and control delay, and the allowable overshoot.

6. The current control method according to claim 4, characterized in that, The step of generating a correction amount based on the current deviation includes: When the current deviation is greater than zero, a second correction amount is determined based on a preset first current compensation factor, wherein the first current compensation factor is a positive number, and the value of the first current compensation factor is determined based on at least one of the current response speed of the converter, the current deviation, the allowable overshoot degree, and the positive response characteristics of the converter. When the current deviation is less than zero, the second correction amount is determined based on a preset second current compensation factor, wherein the second current compensation factor is a negative number, and the absolute value of the second current compensation factor is determined based on at least one of the current response speed of the converter, the current deviation, the allowable overshoot, and the negative response characteristics of the converter.

7. The current control method according to claim 1, characterized in that, The target current command value and the current sample value are the current quantities in the target coordinate system, which is the abc coordinate system, the αβ coordinate system, or the dq coordinate system. The step of controlling the current of the converter based on the target current command value and the current sample value includes: In the target coordinate system, the control quantity is determined based on the target current command value and the current sample value; The three-phase modulation signal is determined based on the control quantity, and the converter is modulated according to the three-phase modulation signal.

8. The current control method according to claim 7, characterized in that, Determining the control quantity based on the target current command value and the current sample value includes: The current control deviation is obtained by subtracting the target current command value from the current sample value. The current control deviation is subjected to proportional and integral calculations respectively, and the sum of the proportional and integral calculation results is determined as the control quantity; Alternatively, proportional and resonant calculations can be performed on the current control deviation, and the sum of the proportional and resonant calculation results can be determined as the control quantity.

9. A current control system, characterized in that, include: The current acquisition module is used to determine the current deviation based on the initial current command value and the current sample value of the converter in the current operating mode; The status determination module is used to determine the command correction status based on the current deviation and the preset current threshold value; The instruction correction module is used to determine the target current instruction value based on the instruction correction status and the current deviation. The current control module is used to control the current of the converter according to the target current command value and the current sample value.

10. A converter, characterized in that, It includes a power conversion circuit and a controller, the controller being configured to perform the current control method according to any one of claims 1 to 8.

Images