Converter adaptive droop control method, device, medium and equipment

Abstract

The invention provides a converter adaptive droop control method and device, a medium and equipment. Determining a corresponding initial droop control coefficient according to the performance parameter of each first converter, determining the power margin of each first converter at the DC control end according to the actual working condition, and adjusting the initial droop control coefficient according to the power margin. According to the method, the adaptive droop control coefficient based on the system power regulation requirement and the power regulation capability of the first converter is obtained, so that the droop control equation based on the adaptive droop control coefficient is determined to realize the regulation of the first converter, and therefore, the control process of the first converter is associated with the dynamic requirement of the system and the performance of the first converter; self-adaptive adjustment is achieved, the risk that the control effect is poor and the power adjusting capacity of a direct current network is lost due to the fact that the droop coefficient is fixed is reduced, and the stability, flexibility and effectiveness of converter droop control are improved.

Description

Technical Field

[0001] The present application relates to the field of direct current grid control technology, and in particular to a method, device, medium, and equipment for adaptive droop control of a converter. Background Art

[0002] In DC power grids, droop control is an important control strategy used to achieve power distribution and voltage regulation between power sources. In traditional droop control methods, the droop coefficient is fixed, which results in poor system control flexibility and unsatisfactory voltage dynamic regulation when facing complex working conditions such as frequent power fluctuations.

[0003] Therefore, it is necessary to improve the stability of the system and the flexibility of control under the condition of ensuring the control effect of the droop controller of the converter. Specifically, in some implementations where the droop coefficient is determined according to the capacity of the converter and remains unchanged, when the system state changes, the converter may switch to a constant power mode during the adjustment process, and then lose the ability to respond to changes in the DC network flow. The corresponding converter loses the power regulation ability of the DC network, thereby affecting the effect of dynamic power distribution of each converter. Therefore, a converter adaptive droop control method is needed to solve the problem of poor stability and flexibility of the current DC grid droop control system. Summary of the invention

[0004] The purpose of the present application is to solve at least one of the above technical defects, especially the technical defect that the current DC grid droop control system in the prior art has poor flexibility.

[0005] In a first aspect, the present application provides a method for adaptive droop control of a converter, the method being applied to a target power grid, the target power grid comprising a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling a direct current voltage, the method comprising:

[0006] determining an initial droop control coefficient and a power margin of each of the first converters;

[0007] adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient;

[0008] The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid;

[0009] A droop control equation is determined according to the adaptive droop control coefficient, and each of the first converters is controlled according to the droop control equation.

[0010] As an optional implementation manner, the determining the initial droop control coefficient and the power margin of each of the first converters includes:

[0011] Determining an initial droop control coefficient of each of the first converters by a first formula according to the load capacity of each of the first converters;

[0012] Wherein, the load capacity includes the maximum value of the DC current and the maximum value of the DC voltage;

[0013] Wherein, the first formula includes:

[0014]

[0015] Wherein, k is the initial droop control coefficient, β is the first adjustment coefficient, and the value range is , used to adjust the initial droop control coefficient within the DC voltage fluctuation range, I dcmax is the maximum DC current of the first converter, U dcmax is the maximum DC voltage of the first converter, U dcref is the DC voltage command value of the first converter;

[0016] Determining a power regulation requirement of the target power grid according to an actual value of the DC current of each of the first converters and a DC current command value;

[0017] According to the power regulation requirement, a power margin indication value of each of the first converters is determined.

[0018] As an optional implementation manner, the power regulation requirement includes a power shortage and a power surplus, and determining the power margin indication value of each of the first converters according to the power regulation requirement includes:

[0019] If the power regulation requirement is a power shortage, the power margin indication value of each of the first converters includes the difference between the maximum value of the DC current of each of the first converters and the actual value of the DC current of each of the first converters. If the power regulation requirement is a power surplus, the power margin indication value of each of the first converters includes the actual value of the DC current of each of the first converters.

[0020] As an optional implementation manner, adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient includes:

[0021] According to the power margin, adjusting the initial droop control coefficient by a second formula to obtain an adaptive droop control coefficient;

[0022] Wherein, the second formula includes:

[0023]

[0024] Wherein, k is the initial droop coefficient determined by the first formula, k* is the adaptive droop control coefficient, α is the second adjustment coefficient, which is used to adjust the value range of k* to adapt to the working conditions, I dc is the actual value of the DC current of the first converter, I dcref is the DC current indication value of the first converter, the magnitude relationship between the absolute value of the DC current actual value of the first converter and the DC current indication value of the first converter is used to indicate the power regulation demand, and when Used to indicate that the power regulation requirement is a power shortage. Used to indicate that the power regulation requirement is a power surplus.

[0025] As an optional implementation, the method further includes:

[0026] According to the third formula, limiting the value of the adaptive droop control coefficient;

[0027] Wherein, the third formula includes:

[0028]

[0029] Among them, k* max and k* min are the upper and lower limits of k* respectively.

[0030] As an optional implementation manner, the voltage source converter type high voltage direct current power transmission system further includes at least one second converter at a non-DC voltage control end, and the method further includes:

[0031] According to the system control performance parameter, conditionally constraining the adaptive droop control coefficient to obtain a constrained target droop control coefficient, and controlling each of the first converters according to the target droop control coefficient;

[0032] The system control performance parameters include a steady-state error, and the steady-state error is determined according to the adaptive droop control coefficient, the DC current and DC voltage of each of the first converters, and the DC current and DC voltage of each of the second converters.

[0033] As an optional implementation, the method further includes:

[0034] The parameters of the target control link are adjusted according to the determined adaptive droop control coefficient and system control performance parameters.

[0035] In a second aspect, the present application provides a converter adaptive droop control device, the device is applied to a target power grid, the target power grid includes a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling a direct current voltage, the device includes:

[0036] A determination module, used to determine an initial droop control coefficient and a power margin of each of the first converters;

[0037] A processing module, configured to adjust the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient;

[0038] The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid;

[0039] The processing module is further used to determine a droop control equation according to the adaptive droop control coefficient, and control each of the first converters according to the droop control equation.

[0040] In a third aspect, the present application provides a computer device comprising one or more processors and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method described in the first aspect are performed.

[0041] In a fourth aspect, the present application provides a storage medium storing computer-readable instructions, which, when executed by one or more processors, causes the one or more processors to perform the steps of the method described in the first aspect.

[0042] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0043] Based on any of the above embodiments, the present application determines the corresponding initial droop control coefficient through the performance parameters of each first converter, and determines the power margin of each first converter at the DC control end through the actual operating conditions, and adjusts the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient based on the system power regulation requirements and the power regulation capability of the first converter, thereby determining a droop control equation based on the adaptive droop control coefficient to achieve regulation of the first converter. As a result, the control process of the first converter is associated with the dynamic requirements of the system and its own performance, achieving adaptive regulation, reducing the risk of poor control effect and loss of power regulation capability of the DC network due to fixed droop coefficients, and improving the stability, flexibility and effectiveness of converter droop control. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Figure 1 A schematic diagram of a power grid structure of a method for adaptive droop control of a converter provided in one embodiment of the present application;

[0046] Figure 2 A schematic diagram of the control effect of a converter adaptive droop control method provided by an embodiment of the present application;

[0047] Figure 3 A schematic flow chart of a method for adaptive droop control of a converter provided in one embodiment of the present application;

[0048] Figure 4 A schematic diagram of a control system of a converter adaptive droop control method provided by an embodiment of the present application;

[0049] Figure 5 A schematic diagram of a control system of a converter adaptive droop control method provided by an embodiment of the present application;

[0050] Figure 6 This is a diagram of the internal structure of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] The adaptive droop control method considering the converter power margin is a control strategy for DC power grids, which aims to improve the stability of the system and its ability to cope with power fluctuations. The technical background of this control method stems from the traditional setting method of the droop control coefficient in the DC power grid, which is usually based on empirical values ​​or given according to the converter capacity, and rarely considers the real-time operating conditions and stability of the system. Therefore, in order to solve this problem, a feasible implementation method is to use an adaptive droop control strategy considering the real-time power margin of the converter.

[0052] Specifically, in DC power grids, droop control is an important control strategy used to achieve power distribution and voltage regulation between power sources. In traditional droop control methods, the droop coefficient is fixed, which leads to poor flexibility of system control and unsatisfactory voltage dynamic regulation effect when facing complex working conditions such as frequent power fluctuations. Therefore, an adaptive droop control method based on power margin can be used to solve such problems.

[0053] The core idea of ​​this type of method is to adjust the droop coefficient according to the real-time power margin of the converter, so as to achieve reasonable distribution of system power and stable voltage control. Specifically, when the power margin of a converter station in the system is large, the converter station can bear more unbalanced power, while the converter station with a smaller power margin can share less unbalanced power. In this way, by adaptively adjusting the droop coefficient, it can ensure that the system can still maintain stable operation in the face of power fluctuations, thereby improving the overall stability and reliability of the system.

[0054] In addition, this type of control method also takes into account the real-time operating conditions of the system and introduces the concept of power margin to make the control strategy more intelligent and adaptive. Through simulation verification, this method can effectively achieve the reasonable distribution of unbalanced power and ensure the stable operation of the system, especially in the case of frequent power fluctuations, showing good control effect and improved system stability.

[0055] Current research on droop control focuses on achieving power flow optimization and other purposes, while the stability analysis of the system under droop control does not consider the real-time working conditions. How to make the droop controller fully play its regulatory role while ensuring system stability is an urgent problem to be solved.

[0056] The adaptive droop control strategy considering power margin provided in this application enables the converter with larger power margin to undertake more regulation tasks, establishes a state space model of a multi-terminal voltage source converter type high voltage direct current transmission system, analyzes the action mechanism of droop control on this basis, and proposes a droop coefficient steady-state error constraint considering the influence of disturbance on system voltage stability to limit the value range of the adaptive droop coefficient. The proposed method can make full use of the real-time power margin of the converter and can effectively improve the system stability.

[0057] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0058] See also Figure 1 , Figure 1 A schematic diagram of a power grid structure of a converter adaptive droop control method provided by an embodiment of the present application, such as Figure 1As shown, the method provided in the present application can be used for a voltage source converter based high voltage direct current transmission system (VSC-HVDC for short). Specifically, the method provided in the present application is applied to a target power grid, wherein the target power grid includes a voltage source converter based high voltage direct current transmission system having a plurality of first converters for controlling a DC voltage. A typical structure of such a system can be as follows Figure 1 The four-terminal VSC-HVDC system shown in FIG. wherein converters VSC1 and VSC2 are connected to offshore wind farms WF1 and WF2 respectively; and converters VSC3 and VSC4 are connected to AC systems AC1 and AC2 respectively.

[0059] In steady-state operation, VSC1 and VSC2 use fixed frequency control and fixed AC voltage control, and the converters VSC3 and VSC4 connected to the AC system are DC voltage control terminals. When the DC voltage control terminal is greater than or equal to the two terminals, a certain coordinated control strategy is required to allocate the DC voltage control task. In multi-terminal VSC-HVDC systems, droop control is the most widely used inter-station coordinated control method. Taking VI droop control as an example, when Figure 1 When VSC3 and VSC4 in the system adopt droop control, Figure 2 The characteristic curve is used to analyze the operating status of the converter.

[0060] The VI droop control law is:

[0061]

[0062] Among them, i dc * The DC current command value assigned by the droop controller to the inner loop controller, I dcref is the DC current indication value of the first converter; K1 is the droop coefficient; U dc , U dcref and U dcmin They are respectively the actual value, the command value and the minimum value allowed of the DC voltage of the first converter.

[0063] See also Figure 2 , Figure 2 A schematic diagram of the control effect of the converter adaptive droop control method provided by an embodiment of the present application is shown in FIG. Figure 2 As shown in the figure, the steady-state operating point of the converter under different conditions is given.

[0064] The droop control coefficient determines how much of the power imbalance in the DC network is distributed to the converter. When the droop coefficient is large, the converter will share more power imbalance, and vice versa. The droop coefficient is usually determined by the converter capacity and is fixed, but this method has certain problems. Assuming that the system initially operates in state 1, the stable operating point of VSC3 and VSC4 is and When unbalanced power appears in the DC network, after the action of the droop controller, VSC3 and VSC4 finally stabilize in state 2, and their stable operating point becomes and It is not difficult to see that the DC current of VSC3 in state 2 will reach Limit value , indicating that the converter switches to the constant power control mode due to full load, and at this time VSC4 still has some power margin.

[0065] If the droop coefficient is determined according to the capacity of the converter and remains unchanged, when the system state changes, the converter may switch to the constant power mode during the regulation process, and then lose the ability to respond to the changes in the DC network power flow. To avoid this situation, an adaptive droop control method considering the converter power margin is proposed.

[0066] The technical concept of the present application is to determine the corresponding initial droop control coefficient through the performance parameters of each first converter, and determine the power margin of each first converter at the DC control end through the actual operating conditions, adjust the initial droop control coefficient according to the power margin, and obtain an adaptive droop control coefficient based on the system power regulation demand and the power regulation capability of the first converter, so as to determine the droop control equation based on the adaptive droop control coefficient to achieve regulation of the first converter. As a result, the control process of the first converter is associated with the dynamic demand of the system and its own performance, to achieve adaptive regulation, reduce the risk of poor control effect and loss of power regulation capability of the DC network due to fixed droop coefficient, and improve the stability, flexibility and effectiveness of converter droop control.

[0067] See also Figure 3 , Figure 3 is a flow chart of a method for adaptive droop control of a converter provided by an embodiment of the present application, wherein the method is applied to a target power grid, wherein the target power grid includes a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling a direct current voltage, such as Figure 3 As shown, the method includes:

[0068] S101, determining an initial droop control coefficient and a power margin of each of the first converters;

[0069] In the present application, the initial droop control coefficient is determined based on electrical parameters related to the load capacity of the first converter, and can be directly used to perform droop control in some feasible implementations. However, in the present application, the indicator is mainly adaptively optimized based on the power margin and the regulation requirements of the target power grid to improve the flexibility, stability and effectiveness of the control.

[0070] S102, adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient;

[0071] The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid;

[0072] In a specific implementation, the power margin can be calculated by the power of the current load of the first converter and the power under rated conditions, or it can be described by electrical parameters that are easier to calculate or detect, such as the current of the first converter.

[0073] S103: Determine a droop control equation according to the adaptive droop control coefficient, and control each of the first converters according to the droop control equation.

[0074] As mentioned above, the droop control equation can be referred to Figure 1 The VI droop control law proposed during the description is determined, wherein the droop coefficient K1 in the present application can be replaced by the determined adaptive droop control coefficient.

[0075] This implementation method determines the corresponding initial droop control coefficient through the performance parameters of each first converter, and determines the power margin of each first converter at the DC control end through the actual operating conditions, and adjusts the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient based on the system power regulation requirement and the power regulation capability of the first converter, thereby determining a droop control equation based on the adaptive droop control coefficient to achieve regulation of the first converter. As a result, the control process of the first converter is associated with the dynamic requirements of the system and its own performance, achieving adaptive regulation, reducing the risk of poor control effect and loss of power regulation capability of the DC network due to fixed droop coefficients, and improving the stability, flexibility and effectiveness of converter droop control.

[0076] See also Figure 4 , Figure 4 A schematic diagram of a control system of a converter adaptive droop control method provided by an embodiment of the present application, through Figure 4 The corresponding block diagram describes the corresponding scheme of this application.

[0077] As an optional implementation manner, the determining the initial droop control coefficient and the power margin of each of the first converters includes:

[0078] Determining an initial droop control coefficient of each of the first converters by a first formula according to the load capacity of each of the first converters;

[0079] Wherein, the load capacity includes the maximum value of the DC current and the maximum value of the DC voltage;

[0080] The present application provides a specific implementation method for indicating load capacity. In actual application scenarios, the load capacity may not be limited to the maximum DC current and the maximum DC voltage, depending on specific needs.

[0081] Wherein, the first formula includes:

[0082]

[0083] Wherein, k is the initial droop control coefficient, β is the first adjustment coefficient, and the value range is , used to adjust the initial droop control coefficient within the DC voltage fluctuation range, I dcmax is the maximum DC current of the first converter, U dcmax is the maximum DC voltage of the first converter, U dcref is the DC voltage command value of the first converter;

[0084] In some implementations, the first adjustment coefficient may be approximately 0.75, which has a wide range of applicability in specific working conditions.

[0085] Determining a power regulation requirement of the target power grid according to an actual value of the DC current of each of the first converters and a DC current command value;

[0086] According to the power regulation requirement, a power margin indication value of each of the first converters is determined.

[0087] This embodiment uses the first formula to determine the initial droop control coefficient based on the performance parameters of each first converter related to the load capacity, and introduces the first adjustment coefficient to adjust the amplitude of the initial droop control coefficient based on the DC voltage fluctuation, thereby improving the effectiveness of the initial droop control coefficient. In addition, this embodiment also determines the current power regulation demand of the target power grid by comparing the current actual DC current value of each first converter and the DC current indication value of the response control, and then determines the power adjustment direction and the power margin indication value of each first converter. In a specific implementation method, the power margin can be indicated by the current situation of the first converter, thereby providing a data basis for the subsequent determination of the adaptive droop control coefficient, thereby improving the effectiveness of the adaptive droop control coefficient, and then improving the stability, flexibility and effectiveness of the converter droop control.

[0088] As an optional implementation manner, the power regulation requirement includes a power shortage and a power surplus, and determining the power margin indication value of each of the first converters according to the power regulation requirement includes:

[0089] If the power regulation requirement is a power shortage, the power margin indication value of each of the first converters includes the difference between the maximum value of the DC current of each of the first converters and the actual value of the DC current of each of the first converters. If the power regulation requirement is a power surplus, the power margin indication value of each of the first converters includes the actual value of the DC current of each of the first converters.

[0090] Specifically, considering the direction of the actual value of the DC current, it can be realized by the absolute value in the application. When considering the real-time power margin of the converter, it is necessary to introduce an adaptive rule. When the DC current of the converter is greater than the command value, it means that the system has a power shortage and the DC current of the converter needs to be increased to make up for the shortage. At this time, the power margin of the converter corresponds to the difference between the DC current and the maximum value. ; When the converter DC current is less than the command value, it means that the system has a power surplus and needs to reduce the converter DC current to share the surplus. At this time, the converter power margin corresponds to the absolute value of the DC current .

[0091] This implementation method determines the expression of the power margin indicator value of each first converter according to the power demand situation of the target power grid, thereby determining the current physical quantity related to the power margin according to different power demand situations, and then calculating and obtaining the corresponding adaptive droop control coefficient, thereby improving the effectiveness of the adaptive droop control coefficient, and then improving the stability, flexibility and effectiveness of the converter droop control.

[0092] Further, as an optional implementation manner, adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient includes:

[0093] According to the power margin, adjusting the initial droop control coefficient by a second formula to obtain an adaptive droop control coefficient;

[0094] Wherein, the second formula includes:

[0095]

[0096] Wherein, k is the initial droop coefficient determined by the first formula, k* is the adaptive droop control coefficient, α is the second adjustment coefficient, which is used to adjust the value range of k* to adapt to the working conditions. In a specific implementation, the second adjustment coefficient can be about 3 to improve the applicability of the method. dc is the actual value of the DC current of the first converter, I dcref is the DC current indication value of the first converter, the magnitude relationship between the absolute value of the DC current actual value of the first converter and the DC current indication value of the first converter is used to indicate the power regulation demand, and when Used to indicate that the power regulation requirement is a power shortage. Used to indicate that the power regulation requirement is a power surplus.

[0097] This embodiment uses the second formula to determine the corresponding adaptive droop control coefficient expression under different power regulation demand conditions, thereby improving the effectiveness and physical interpretability of the adaptive droop control coefficient. The power regulation demand is indicated by the relationship between the absolute value of the actual value of the DC current of the first converter and the DC current indication value of the first converter, making the power regulation demand more physically intuitive. A second adjustment coefficient is introduced to adjust the value range of the adaptive droop control coefficient to adapt to specific working conditions, thereby further improving the effectiveness of the adaptive droop control coefficient, thereby improving the stability, flexibility and effectiveness of the converter droop control.

[0098] When determining the second adjustment coefficient After that, the adaptive droop control coefficient The value of is determined by the converter power margin. The first converter with a larger power margin corresponds to The first converter with a smaller power margin corresponds to The smaller the , the less unbalanced power is shared. It is easy to cause the DC voltage to exceed the limit value This will cause the system to become unstable. This means that the converter is extremely insensitive to power imbalance, which is not conducive to coordinated control between converters. Therefore, according to the actual working conditions, the limiting condition can be added. As an optional implementation, the method also includes:

[0099] According to the third formula, limiting the value of the adaptive droop control coefficient;

[0100] Wherein, the third formula includes:

[0101]

[0102] Among them, k* max and k* min are the upper and lower limits of k* respectively.

[0103] This implementation limits the adaptive droop control coefficient according to actual operating conditions, thereby improving the stability and effectiveness of the adaptive droop control coefficient, thereby improving the stability, flexibility and effectiveness of the converter droop control.

[0104] The adaptive droop control coefficient in the control system also determines the impact of the non-DC voltage control end disturbance on the system stability. In order to enable the system to maintain a certain stability while achieving unbalanced power distribution, the adaptive droop control coefficient can be constrained by the steady-state error based on the droop control mechanism.

[0105] As an optional implementation manner, the voltage source converter type high voltage direct current power transmission system further includes at least one second converter at a non-DC voltage control end, and the method further includes:

[0106] According to the system control performance parameter, conditionally constraining the adaptive droop control coefficient to obtain a constrained target droop control coefficient, and controlling each of the first converters according to the target droop control coefficient;

[0107] The system control performance parameters include a steady-state error, and the steady-state error is determined according to the adaptive droop control coefficient, the DC current and DC voltage of each of the first converters, and the DC current and DC voltage of each of the second converters.

[0108] See also Figure 5 , Figure 5 A schematic diagram of a control system of a converter adaptive droop control method provided by an embodiment of the present application is shown in FIG. Figure 5 As shown, under the target grid architecture provided in the present application, combined with the aforementioned control principle description, the closed-loop system with droop control added is determined by the topology of the DC part.

[0109] The present application can perform modeling based on automatic control principles or modern control theories through the mechanism of the equivalent circuit of the target power grid. In this embodiment, the specific modeling process is omitted, and the constraints of the steady-state error on the adaptive droop control coefficient are explained based on the modern control principle.

[0110] The control variable is u and the disturbance variable is , e is the steady-state error of the system, U dcmin is the minimum value of the DC voltage of each first converter, y is the output participating in the closed-loop feedback, z is the output not participating in the closed-loop feedback, and the subscript G is the transfer function from the input quantity to the output quantity of each link, for example is the transfer function from the disturbance variable to the target output.

[0111] In the present application, the control variable u may specifically be the DC current of each first converter, and the disturbance variable Specifically, it may be the DC current of each second converter, y may specifically be the DC voltage of each first converter, and z may specifically be the DC voltage of each second converter.

[0112] And, the matrix expression of the droop controller is:

[0113]

[0114] Wherein, k3 is the droop coefficient of converter VSC3, k4 is the droop coefficient of converter VSC4. When the droop control end is the power outflow converter, the droop coefficient is positive, otherwise it is negative. The droop coefficient here can be an adaptive droop control coefficient determined according to the above-mentioned related implementation methods.

[0115] The error variable is the difference between the output variable and its reference variable. In this application, its physical meaning can be the degree to which the DC voltage at each end deviates from the minimum voltage. Since the voltage stability of the DC voltage control end is more likely to attract attention, the steady-state error here can refer to the steady-state error of the y channel, that is, the influence of the input variable on the DC voltage at the voltage control end.

[0116] The steady-state error expression is:

[0117]

[0118] Where: are input variables, including disturbance variables and minimum values ​​of control variables; is the narrowly controlled object G yu The sensitivity function of .

[0119] In addition, the concept of norm can be introduced to evaluate the gain of energy transfer between variables, and the ratio of the second norms of the variables can be used to evaluate the impact of the input variables on the output variables and the control variables, that is, to evaluate the size of the steady-state error.

[0120] Since the maximum gain of a MIMO system in any direction is equal to the maximum singular value, that is:

[0121]

[0122] In the formula: d is the input variable; y is the output variable; is the transfer function from d to y.

[0123] Thus, the steady-state error can be converted into the singular value of the transfer function matrix, and the steady-state error constraint in the droop coefficient domain is then converted into the singular value constraint of the transfer function. In this embodiment, the transfer function matrix is part.

[0124] This implementation method can further impose conditional constraints on the determined adaptive droop control coefficient through system control performance requirements such as steady-state error, and modeling can be performed through classical control principles or modern control principles to obtain an expression based on system control performance and the adaptive droop control coefficient, thereby further implementing constraints on the adaptive droop control coefficient and improving the effectiveness and stability of droop control.

[0125] As an optional implementation, the method further includes:

[0126] The parameters of the target control link are adjusted according to the determined adaptive droop control coefficient and system control performance parameters.

[0127] The target control link may include any adjustable link in the control system except the controlled object, such as Figure 5 Any parameter or transfer function in the control system, this implementation uses the expected system performance and the droop control coefficient determined in any implementation as constraints, and takes the parameters of the target control link, that is, the part of the transfer function that needs to be adjusted in the control system as the constraint target. This implementation can also be implemented in combination with the previous implementation to achieve feedback until the control system performance is optimized to a preset degree.

[0128] According to the determined expression of the adaptive droop control coefficient, as well as the requirements of system control performance parameters such as stability, steady-state error, and dynamic error, they can be used together as constraints to optimize the transfer function of the adjustable part in the target control link, so that the performance of the control system can be optimized. Further, based on the optimized control system, a new indicator expression can be determined to achieve the next round of optimization. The optimization process can be implemented in combination with some feasible optimization algorithms based on artificial intelligence until the optimization goal is reached or until convergence, thereby further improving the practicality of the adaptive droop control coefficient in control.

[0129] This implementation can optimize the target control link in the control system through the determined adaptive droop control coefficient and the required system control performance parameters, thereby adjusting the transfer function of the overall control system, thereby determining the optimized control system index, and further optimizing the control system based on the optimized control performance index, thereby improving the performance of the control system and improving the effectiveness and stability of the droop control.

[0130] The embodiment of the present application further provides a converter adaptive droop control device to implement the above method, the device is applied to a target power grid, the target power grid includes a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling direct current voltage, the device includes:

[0131] A determination module, used to determine an initial droop control coefficient and a power margin of each of the first converters;

[0132] A processing module, configured to adjust the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient;

[0133] The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid;

[0134] The processing module is further used to determine a droop control equation according to the adaptive droop control coefficient, and control each of the first converters according to the droop control equation.

[0135] This implementation method determines the corresponding initial droop control coefficient through the performance parameters of each first converter, and determines the power margin of each first converter at the DC control end through the actual operating conditions, and adjusts the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient based on the system power regulation requirement and the power regulation capability of the first converter, thereby determining a droop control equation based on the adaptive droop control coefficient to achieve regulation of the first converter. As a result, the control process of the first converter is associated with the dynamic requirements of the system and its own performance, achieving adaptive regulation, reducing the risk of poor control effect and loss of power regulation capability of the DC network due to fixed droop coefficients, and improving the stability, flexibility and effectiveness of converter droop control.

[0136] As an optional implementation manner, the specific manner in which the determination module determines the initial droop control coefficient and the power margin of each of the first converters includes:

[0137] Determining an initial droop control coefficient of each of the first converters by a first formula according to the load capacity of each of the first converters;

[0138] Wherein, the first formula includes:

[0139]

[0140] Wherein, k is the initial droop control coefficient, β is the first adjustment coefficient, and the value range is , used to adjust the initial droop control coefficient within the DC voltage fluctuation range, I dcmax is the maximum DC current of the first converter, U dcmax is the maximum DC voltage of the first converter, U dcref is the DC voltage command value of the first converter;

[0141] Determining a power regulation requirement of the target power grid according to an actual value of the DC current of each of the first converters and a DC current command value;

[0142] According to the power regulation requirement, a power margin indication value of each of the first converters is determined.

[0143] This embodiment uses the first formula to determine the initial droop control coefficient based on the performance parameters of each first converter related to the load capacity, and introduces the first adjustment coefficient to adjust the amplitude of the initial droop control coefficient based on the DC voltage fluctuation, thereby improving the effectiveness of the initial droop control coefficient. In addition, this embodiment also determines the current power regulation demand of the target power grid by comparing the current actual DC current value of each first converter and the DC current indication value of the response control, and then determines the power adjustment direction and the power margin indication value of each first converter. In a specific implementation method, the power margin can be indicated by the current situation of the first converter, thereby providing a data basis for the subsequent determination of the adaptive droop control coefficient, thereby improving the effectiveness of the adaptive droop control coefficient, and then improving the stability, flexibility and effectiveness of the converter droop control.

[0144] As an optional implementation manner, the power regulation requirement includes a power shortage and a power surplus, and the processing module determines a specific manner of a power margin indication value of each of the first converters according to the power regulation requirement, including:

[0145] If the power regulation requirement is a power shortage, the power margin indication value of each of the first converters includes the difference between the maximum value of the DC current of each of the first converters and the actual value of the DC current of each of the first converters. If the power regulation requirement is a power surplus, the power margin indication value of each of the first converters includes the actual value of the DC current of each of the first converters.

[0146] This implementation method determines the expression of the power margin indicator value of each first converter according to the power demand situation of the target power grid, thereby determining the current physical quantity related to the power margin according to different power demand situations, and then calculating and obtaining the corresponding adaptive droop control coefficient, thereby improving the effectiveness of the adaptive droop control coefficient, and then improving the stability, flexibility and effectiveness of the converter droop control.

[0147] As an optional implementation manner, the processing module adjusts the initial droop control coefficient according to the power margin to obtain the adaptive droop control coefficient in a specific manner including:

[0148] According to the power margin, adjusting the initial droop control coefficient by a second formula to obtain an adaptive droop control coefficient;

[0149] Wherein, the second formula includes:

[0150]

[0151] Wherein, k is the initial droop coefficient determined by the first formula, k* is the adaptive droop control coefficient, α is the second adjustment coefficient, which is used to adjust the value range of k* to adapt to the working conditions, I dc is the actual value of the DC current of the first converter, I dcref is the DC current indication value of the first converter, the magnitude relationship between the absolute value of the DC current actual value of the first converter and the DC current indication value of the first converter is used to indicate the power regulation demand, and when Used to indicate that the power regulation requirement is a power shortage. Used to indicate that the power regulation requirement is a power surplus.

[0152] This embodiment uses the second formula to determine the corresponding adaptive droop control coefficient expression under different power regulation demand conditions, thereby improving the effectiveness and physical interpretability of the adaptive droop control coefficient. The power regulation demand is indicated by the relationship between the absolute value of the actual value of the DC current of the first converter and the DC current indication value of the first converter, making the power regulation demand more physically intuitive. A second adjustment coefficient is introduced to adjust the value range of the adaptive droop control coefficient to adapt to specific working conditions, thereby further improving the effectiveness of the adaptive droop control coefficient, thereby improving the stability, flexibility and effectiveness of the converter droop control.

[0153] As an optional implementation manner, the processing module is further used for:

[0154] According to the third formula, limiting the value of the adaptive droop control coefficient;

[0155] Wherein, the third formula includes:

[0156]

[0157] Among them, k* max and k* min are the upper and lower limits of k* respectively.

[0158] This implementation limits the adaptive droop control coefficient according to actual operating conditions, thereby improving the stability and effectiveness of the adaptive droop control coefficient, thereby improving the stability, flexibility and effectiveness of the converter droop control.

[0159] As an optional implementation manner, the voltage source converter type high voltage direct current power transmission system further includes at least one second converter at a non-DC voltage control end, and the processing module is further used for:

[0160] According to the system control performance parameter, conditionally constraining the adaptive droop control coefficient to obtain a constrained target droop control coefficient, and controlling each of the first converters according to the target droop control coefficient;

[0161] The system control performance parameters include a steady-state error, and the steady-state error is determined according to the adaptive droop control coefficient, the DC current and DC voltage of each of the first converters, and the DC current and DC voltage of each of the second converters.

[0162] This implementation method can further impose conditional constraints on the determined adaptive droop control coefficient through system control performance requirements such as steady-state error, and modeling can be performed through classical control principles or modern control principles to obtain an expression based on system control performance and the adaptive droop control coefficient, thereby further implementing constraints on the adaptive droop control coefficient and improving the effectiveness and stability of droop control.

[0163] As an optional implementation manner, the processing module is further used for:

[0164] The parameters of the target control link are adjusted according to the determined adaptive droop control coefficient and system control performance parameters.

[0165] This implementation can optimize the target control link in the control system through the determined adaptive droop control coefficient and the required system control performance parameters, thereby adjusting the transfer function of the overall control system, thereby determining the optimized control system index, and further optimizing the control system based on the optimized control performance index, thereby improving the performance of the control system and improving the effectiveness and stability of the droop control.

[0166] It should be noted that it should be understood that the division of the various modules of the above device is only a division of logical functions. In actual implementation, they can be fully or partially integrated into one physical entity, or they can be physically separated. And these modules can all be implemented in the form of software called by processing elements; they can also be all implemented in the form of hardware; some modules can also be implemented in the form of software called by processing elements, and some modules can be implemented in the form of hardware. For example, the determination module can be a separately established processing element, or it can be integrated in a chip of the above device. In addition, it can also be stored in the memory of the above device in the form of program code, and called and executed by a processing element of the above device. The implementation of other modules is similar. In addition, these modules can be fully or partially integrated together, or they can be implemented independently. The processing element here can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each module above can be completed by an integrated logic circuit of hardware in the processor element or instructions in the form of software.

[0167] Indicatively, if Figure 6 As shown, Figure 6 This is a schematic diagram of the internal structure of a computer device provided in an embodiment of the present application. The computer device 300 may be provided as a server. Figure 6 The computer device 300 includes a processing component 302, which further includes one or more processors, and a memory resource represented by a memory 301 for storing instructions executable by the processing component 302, such as an application. The application stored in the memory 301 may include one or more modules, each corresponding to a set of instructions. In addition, the processing component 302 is configured to execute the instructions to perform the text recognition method of any of the above embodiments.

[0168] The computer device 300 may further include a power supply component 303 configured to perform power management of the computer device 300, a wired or wireless network interface 304 configured to connect the computer device 300 to a network, and an input / output (I / O) interface 305. The computer device 300 may operate based on an operating system stored in the memory 301, such as Windows Server TM, Mac OS X TM, Unix TM, Linux TM, Free BSD TM, or the like.

[0169] Those skilled in the art will understand that Figure 6 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0170] An embodiment of the present application provides a storage medium, in which computer-readable instructions are stored. When the computer-readable instructions are executed by one or more processors, the one or more processors execute a method provided in any embodiment.

[0171] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0172] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0173] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for adaptive droop control of a converter, characterized in that: The method is applied to a target power grid, the target power grid comprising a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling direct current voltage, the method comprising: determining an initial droop control coefficient and a power margin of each of the first converters; adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient; The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid; A droop control equation is determined according to the adaptive droop control coefficient, and each of the first converters is controlled according to the droop control equation.

2. The method according to claim 1, characterized in that The determining of the initial droop control coefficient and the power margin of each of the first converters comprises: Determining an initial droop control coefficient of each of the first converters by a first formula according to the load capacity of each of the first converters; Wherein, the load capacity includes the maximum value of the DC current and the maximum value of the DC voltage; Wherein, the first formula includes: Wherein, k is the initial droop control coefficient, β is the first adjustment coefficient, and the value range is , used to adjust the initial droop control coefficient within the DC voltage fluctuation range, I dcmax is the maximum DC current of the first converter, U dcmax is the maximum DC voltage of the first converter, U dcref is the DC voltage command value of the first converter; Determining a power regulation requirement of the target power grid according to an actual value of the DC current of each of the first converters and a DC current command value; According to the power regulation requirement, a power margin indication value of each of the first converters is determined.

3. The method according to claim 2, characterized in that The power regulation requirement includes a power deficit and a power surplus, and determining the power margin indication value of each of the first converters according to the power regulation requirement includes: If the power regulation requirement is a power shortage, the power margin indication value of each of the first converters includes the difference between the maximum value of the DC current of each of the first converters and the actual value of the DC current of each of the first converters. If the power regulation requirement is a power surplus, the power margin indication value of each of the first converters includes the actual value of the DC current of each of the first converters.

4. The method according to claim 3, characterized in that The adjusting the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient includes: According to the power margin, adjusting the initial droop control coefficient by a second formula to obtain an adaptive droop control coefficient; Wherein, the second formula includes: Wherein, k is the initial droop coefficient determined by the first formula, k* is the adaptive droop control coefficient, α is the second adjustment coefficient, which is used to adjust the value range of k* to adapt to the working conditions, I dc is the actual value of the DC current of the first converter, I dcref is the DC current indication value of the first converter, the magnitude relationship between the absolute value of the actual value of the DC current of the first converter and the DC current indication value of the first converter is used to indicate the power regulation demand, and when Used to indicate that the power regulation requirement is a power shortage. Used to indicate that the power regulation requirement is a power surplus.

5. The method according to claim 4, characterized in that The method further comprises: According to the third formula, limiting the value of the adaptive droop control coefficient; Wherein, the third formula includes: Among them, k* max and k* min are the upper and lower limits of k* respectively.

6. The method according to claim 1, characterized in that The voltage source converter type high voltage direct current power transmission system further comprises at least one second converter having a non-DC voltage control terminal, and the method further comprises: According to the system control performance parameter, conditionally constraining the adaptive droop control coefficient to obtain a constrained target droop control coefficient, and controlling each of the first converters according to the target droop control coefficient; The system control performance parameters include a steady-state error, and the steady-state error is determined according to the adaptive droop control coefficient, the DC current and DC voltage of each of the first converters, and the DC current and DC voltage of each of the second converters.

7. The method according to claim 1, characterized in that The method further comprises: The parameters of the target control link are adjusted according to the determined adaptive droop control coefficient and system control performance parameters.

8. A converter adaptive droop control device, characterized in that: The device is applied to a target power grid, the target power grid includes a voltage source converter type high voltage direct current transmission system having a plurality of first converters for controlling direct current voltage, and the device includes: A determination module, used to determine an initial droop control coefficient and a power margin of each of the first converters; A processing module, configured to adjust the initial droop control coefficient according to the power margin to obtain an adaptive droop control coefficient; The power margin is used to indicate the power margin that each of the first converters can currently load, and the adaptive droop control coefficient is used to indicate the performance of each of the first converters in adjusting electrical parameters according to the unbalanced power of the target power grid; The processing module is further used to determine a droop control equation according to the adaptive droop control coefficient, and control each of the first converters according to the droop control equation.

9. A computer device, characterized in that: The method comprises one or more processors and a memory, wherein the memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the method according to any one of claims 1 to 7 are performed.

10. A storage medium, characterized in that: The storage medium stores computer-readable instructions, and when the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the method according to any one of claims 1 to 7.

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