Micro-grid distributed secondary control method and storage medium

Abstract

The invention discloses an independent micro-grid distributed secondary control method, which supports stable tracking of an energy storage negative power reference value through power per unit value mapping (ranging from [-1, 1] to [0, 2]) and reconstruction of a frequency / voltage correction item formula, and combines adaptive parameters K1 and i (suppression of sudden destabilization and instability) and K2 and i (dynamic acceleration distribution), thereby realizing the distributed secondary control of an independent micro-grid. Unification of stability and rapidness of frequency / voltage recovery and accurate power distribution is realized. Aiming at the problem that the negative power reference value cannot be executed by the traditional strategy, the executable power reference value range is expanded, the system can normally execute the negative power reference value, and the system stability is improved while the regulation speed is reduced by changing the power range. Through the adaptive parameters K1, i and K2, i, system instability under the working condition that the power set value is suddenly changed or unreasonably set can be avoided, and the process of distributing the system power according to the set value can be accelerated.

Description

Technical Field

[0001] This invention relates to the field of power system control technology, specifically to a distributed secondary control method for microgrids and a computer-readable storage medium, which is particularly applicable to frequency / voltage recovery and power distribution control of independent microgrids containing distributed generation (DG). Background Technology

[0002] With the rise of new energy sources and distributed power generation, independent microgrids have attracted attention due to their engineering application value. In the engineering application of independent microgrids, to efficiently execute and study each control link, a three-layer control architecture can be established: primary, secondary, and tertiary control. The secondary control function includes frequency and voltage recovery and precise power allocation. To avoid the risk of centralized single-point failures, independent microgrids often incorporate distributed secondary control. Currently, secondary control based on consensus algorithms can achieve frequency and voltage recovery and precise power allocation. However, in actual execution, situations such as negative power setpoints for energy storage and sudden changes in power setpoints can affect algorithm execution. Furthermore, traditional consensus algorithms cannot handle situations with negative power setpoints for energy storage, and sudden changes in power setpoints can affect system stability and even lead to system instability. Summary of the Invention

[0003] In view of the technical defects and drawbacks existing in the prior art, embodiments of the present invention provide a microgrid distributed secondary control method and storage medium to overcome or at least partially solve the above problems, the specific solution of which is as follows:

[0004] As a first aspect of the present invention, a distributed secondary control method for a microgrid is provided, comprising:

[0005] S1, Data Acquisition:

[0006] The controllers of each distributed generation (DG) exchange real-time operating data through a communication network to obtain: the local DG's frequency ω. i Voltage V i Active power per unit value P i Reactive power per unit value Q i ; Corresponding data ω of the neighborhood DG j V j P j Q j， where j∈N i N i In order to cooperate with DG i The set of DG numbering for communication; the local DG power reference per-unit value P issued by the upper layer. iref and Q iref and the corresponding reference value P of the neighborhood DG jref and Q jref ;

[0007] S2, Correction term generation:

[0008] Frequency correction term Ω is generated based on the consensus algorithm. i and voltage correction term Ψ i

[0009] The frequency correction term Ω i The calculation formula is:

[0010]

[0011] The voltage correction term Ψ i The calculation formula is:

[0012]

[0013] Among them, all power per unit values ​​P i Q i P iref Q iref The values ​​of are all in the range of [-1, 1];

[0014] S3, control output:

[0015] Frequency correction term Ω i and voltage correction term Ψ i The droop control fed back to the local DG enables frequency / voltage recovery and power distribution.

[0016] Furthermore, since the role of the power supply's active power in the secondary control has been changed, it is necessary to analyze the impact of the improved strategy on the power supply's active power allocation.

[0017] The objective of steady-state active power allocation is:

[0018]

[0019] Combining the real-time power balance formula, the expression for the actual active power output of each DG is calculated as follows:

[0020]

[0021] There is no power deficit in the three power setting values, that is... At that time, the actual active power output of each DG can be calculated from the expression of the active power output. That is, the actual power is equal to the power setting value;

[0022] When a power deficit occurs, let the power deficit be... ,Right now At this point, the power distribution is as follows:

[0023]

[0024] That is, in steady state, the power deficit is calculated according to ( The +1) proportional ratio is automatically distributed among the power sources.

[0025] Furthermore, the method also includes, in the frequency correction term Ω i The first adaptive parameter K is introduced in the calculation. 1,i ;

[0026] Updated frequency correction term Ω i for:

[0027]

[0028] Among them, K 1,i Used to suppress system instability caused by a sudden drop in the power reference per unit value (K 1,i The same applies to reactive power control (K). 1,i It decreases synchronously when the power reference per-unit value suddenly decreases, by reducing the equivalent control gain. Suppress the risk of system instability.

[0029] Furthermore, the first adaptive parameter K 1,i The implementation includes the following steps:

[0030] Obtaining the per-unit reference value for neighborhood power:

[0031] Obtaining Distributed Power Generation (DG) i Power reference per unit value P iref and its communication neighborhood DG j Power reference per unit value P jref ;

[0032] Parameter calculation: K is determined through minimization. 1,i Value:

[0033]

[0034] The K 1,i By dynamically reducing the equivalent control gain, the risk of system instability caused by a sudden decrease in the power reference per unit value is suppressed.

[0035] When the power reference value suddenly decreases, K 1,i Synchronous reduction, by lowering the equivalent control gain The sudden increase in equivalent gain caused by a sudden decrease in the power reference value is achieved by K 1,i attenuation.

[0036] Furthermore, the method further includes: in the frequency correction term Ω i A second adaptive parameter K is further introduced in the calculation. 2,iUpdate the frequency correction term to:

[0037]

[0038] in, k is a configurable coefficient, k S,i These are the normalized parameters.

[0039] when When K increases, 2,i Increase K to improve the adjustment speed; when the difference decreases, K 2,i Reduce to suppress overshoot.

[0040] Furthermore, the second adaptive parameter K 2,i By normalizing parameter k S,i Dynamically adjust the normalized parameter k S,i The formula is:

[0041]

[0042] This parameter represents the ratio of the actual weighted power sum to the reference weighted power sum;

[0043] When the actual power deviates from the reference value As K2,i increases, the equivalent gain increases. Increase the power convergence speed; when the deviation decreases, K2,i decreases to reduce the equivalent gain and avoid system oscillation.

[0044] Furthermore, the K 2,i The value of is in the range [1, e], and the value of k satisfies lnK. 2,i ∈[0,1], ensuring a balance between system stability and dynamic response speed.

[0045] Furthermore, the adaptive parameter K 1,i and K 2,i The same applies to reactive power control, and its calculation method is symmetrical to that of active power control.

[0046] Furthermore, the adaptive parameter K 1,i and K 2,i The same applies to reactive power control, and its calculation method is symmetrical to that of active power control, specifically including:

[0047] In the calculation of the correction term, variables involving active power are replaced with corresponding reactive power variables, including P. i Replace with Q i P j Replace with Q j P iref Replace with Qiref P jref Replace with Q jref ;

[0048] The adaptive parameter K 1,i and K 2,i After being applied to the reactive power control stage, the updated voltage correction term Ψ i for:

[0049] ;

[0050] Updated voltage correction term Ψ i for:

[0051]

[0052] K 1,i The variable in the calculation is replaced with reactive power, that is:

[0053]

[0054] K 2,i In the calculation, the variable is replaced with reactive power, that is:

[0055]

[0056]

[0057] Q i Q j Q is the per-unit value of reactive power, ranging from [-1, 1]. i,n For DG i The reactive capacity has a nominal value (optional is apparent capacity).

[0058] The replacement ensures that reactive power control and active power control are logically consistent in the application of adaptive parameters.

[0059] As a second aspect of the present invention, a computer-readable storage medium is also provided, wherein a computer program is stored therein, and when executed by a computer, the computer program causes the computer to perform the microgrid distributed secondary control method as described above.

[0060] The present invention has the following beneficial effects:

[0061] The improved strategy addresses the problem that traditional strategies cannot execute negative power reference values ​​by expanding the range of executable power reference values, enabling the system to execute negative power reference values ​​normally. Furthermore, by changing the power range method, the system stability is improved while reducing the adjustment speed.

[0062] Through adaptive parameter K 1,iand K 2,i This can prevent system instability under conditions of sudden changes in power setpoints or unreasonable settings, and can accelerate the process of system power distribution according to the setpoint. Since the two parameters are independent of the algorithm's internal logic, they can be considered to affect system performance by controlling the adjustment speed under different conditions. Therefore, the two adaptive parameters do not affect the system's steady-state control objective, and can also be applied in the same way to reactive power control or other algorithms. Theoretically, the frequency K... 2,i Since there is no abrupt change in power setpoints with voltage, adaptive parameters are not suitable for frequency and voltage recovery. However, the adaptive parameter K... 2,i The design method can also be applied to frequency and voltage regulation, accelerating the recovery of system frequency and voltage, and providing a new approach for the design of adaptive parameters for secondary control. Attached Figure Description

[0063] Figure 1 A flowchart illustrating the distributed secondary control method for microgrids provided in an embodiment of the present invention;

[0064] Figure 2 This is a schematic diagram of a four-node independent microgrid structure provided in an embodiment of the present invention;

[0065] Figure 3 This is a schematic diagram of the equivalent topology for the secondary control and communication of three energy storage units provided in an embodiment of the present invention;

[0066] Figure 4 is a schematic diagram of the energy storage negative power execution condition test provided in an embodiment of the present invention. Figure 4a This is a diagram illustrating a traditional strategy. Figure 4b A diagram illustrating the improved strategy;

[0067] Figure 5 is a schematic diagram of the active power response under the adaptive parameter test condition provided in an embodiment of the present invention, wherein... Figure 5a This is a schematic diagram illustrating the default operating condition without adaptive parameters. Figure 5b To add adaptive parameters A schematic diagram, Figure 5c To add adaptive parameters and A schematic diagram;

[0068] Figure 6 The addition of adaptive parameters provided in the embodiments of the present invention Comparison of the energy storage power response process before and after. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] To enable those skilled in the art to better understand the technical solutions of the present invention, exemplary embodiments of the present invention are described below in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to aid understanding. These should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0071] Where there is no conflict, the various embodiments of the present invention and the features thereof may be combined with each other.

[0072] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0073] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded. Terms such as “connected” or “linked” are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect.

[0074] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meaning in the context of the relevant art and the invention, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein.

[0075] In the technical solution of this invention, the collection, storage, use, processing, transmission, provision, and disclosure of user personal information all comply with relevant laws and regulations and do not violate public order and good morals. The use of user data in this technical solution follows relevant national laws and regulations (e.g., the "Information Security Technology - Personal Information Security Specification"). For example: appropriate measures are taken for personal information access control; restrictions are imposed on the display of personal information; the purpose of using personal information does not exceed the scope of direct or reasonable association; and explicit identity targeting is eliminated when using personal information to avoid precisely locating a specific individual.

[0076] The technical terms related to the technical solutions in the embodiments of this invention are explained as follows:

[0077] Distributed power: DG

[0078] Number of distributed power sources: N

[0079] The actual frequency of the DG numbered i:

[0080] Microgrid frequency reference values:

[0081] The actual voltage of DG numbered i:

[0082] Microgrid voltage reference values:

[0083] The actual output (per unit value) of the DG numbered i:

[0084] Power reference value (per unit) for DG number i:

[0085] The actual output (per unit value) of the DG numbered i:

[0086] Power reference value (per unit) for DG number i:

[0087] The set of DG numbers from which the information source for the DG controller numbered i is located:

[0088] Frequency control gain calculated by secondary control:

[0089] Active power control gain calculated by secondary control:

[0090] Voltage control gain calculated for secondary control:

[0091] Reactive power control gain calculated by secondary control:

[0092] Total active power required by load and network losses:

[0093] The DG capacity with ID i has a named value:

[0094] As the basis of this invention and to aid in understanding the known technical content of this invention, the underlying theory of distributed secondary control dependency (graph theory, consensus algorithm) is defined as follows:

[0095] (1) Graph Theory

[0096] The distributed secondary control communication graph can be viewed as a directed graph, where DGs are directed graph nodes and the communication lines between DGs are directed graph edges.

[0097] Let the nodes in the directed graph be... , Let the edge from node j to node i be denoted as . Representing an edge The weight of the edge. If there is no edge from node j to node i in the directed graph, then =0; otherwise >0. (Note) Let be the adjacency matrix of a directed graph.

[0098] Define the set of communication nodes for node i as follows: When node j has an edge to node i, ;otherwise .

[0099] The degree matrix D of a directed graph is defined as follows: ,in The Laplace matrix L of a directed graph is defined as L = DA.

[0100] For a directed graph, if there exists a node from which there is a directed path to any other node in the graph, then the directed graph is said to have a spanning tree, and that node is the root node.

[0101] (2) Consensus Algorithm

[0102] Set nodes The real-time control information status is The trend of change is Through distributed collaborative control using a consensus algorithm, each node receives control information from the communication node, updates its own state by performing information updates and iterative calculations based on its own information and the information of the communication node. The adjustment and synchronization control mechanism is shown in equation (1).

[0103] (1)

[0104] in For node i information, To communicate node information with node i (j=1, 2, …, ), The number of nodes communicating with node i. This represents the communication weight between node i and node j, where node i can receive information from node j. Regarding the adjustment synchronization mechanism (2-14), when the system communication topology includes a spanning tree, the state of all nodes can be synchronized to a common value through control. For states such as frequency and voltage, it is necessary to return them to the set values. Therefore, a consistent reference value is added to them, and control is performed through tracking synchronization, as shown in equation (2).

[0105] (2)

[0106] in For consistent reference values, This represents the weight of node i receiving the consistent reference value. In a system communication topology graph containing a spanning tree, and with at least one root node... If the value is not 0, the system can adjust the state of all nodes to [a certain value]. .

[0107] (3) Distributed secondary control

[0108] In a three-layer hierarchical control architecture for microgrids, the frequency and voltage of the microgrid under primary control are usually not at their rated values, and power is often difficult to allocate precisely according to demand. Therefore, the basic function of secondary control is to restore the frequency and voltage to their rated values ​​and to precisely adjust the power to the set values. By measuring, communicating, and calculating the line frequency, voltage, and active and reactive power of the distributed generation (DG), secondary control can obtain feedback quantities. This feedback quantity is then fed back to a portion of the primary control to correct the primary control, adjust the deviation, and regulate the frequency, voltage, active and reactive power to their rated or set values.

[0109] Centralized secondary control requires a central hub for data collection and computation, which carries the risk of single-point failure. To mitigate this risk, distributed secondary control is proposed. In distributed secondary control, controllers are located at the corresponding strain gauge units and can operate independently. Each controller communicates and performs calculations with the others via a communication network, outputting control signals to its local controller. The distributed control structure is relatively flexible and highly scalable.

[0110] For complex distributed communication systems, if the controller of a single distributed generation (DG) can obtain information from all other DGs, the control method is relatively simple, but the requirements for the communication system are high. Therefore, to simplify the communication system and improve performance and reliability, each DG's controller only communicates with a subset of other controllers, eliminating the need for a microgrid communication bus. This lowers the requirements for the communication system and improves the reliability of the microgrid. In this case, the secondary controller typically employs a consensus algorithm or other control system.

[0111] The secondary control method based on consensus algorithms can currently achieve frequency and voltage recovery and precise active and reactive power allocation under simple communication system conditions. For a DG with node number i (referred to as DGi for simplicity), its secondary controller calculation method is as follows:

[0112] (3)

[0113] (4)

[0114] in and These are the frequency and voltage correction terms for DGi, which are fed back to the frequency and voltage droop control of DGi for adjustment.

[0115] The steady-state objective of control equation (3) is:

[0116] (5)

[0117] (6)

[0118] That is, the frequency is restored to the rated value, and the active power is distributed in the same proportion as the reference value.

[0119] The steady-state objective of control equation (4) is:

[0120] (7)

[0121] (8)

[0122] That is, the voltage is restored to the rated value, and the reactive power is distributed in the same proportion as the reference value.

[0123] Based on the data requirements of this calculation method, the following can be listed: the real-time input data of the DGi secondary controller, as shown in Table 1; and the preset parameters of the DGi secondary controller, as shown in Table 2. The tertiary control-related data is determined by the tertiary control and then sent to the secondary controller for reception. The specific process of the tertiary control is not considered; this invention only considers the power reference value that the secondary controller can receive.

[0124] Table 1 Real-time input data of DGi's secondary controller

[0125]

[0126] Table 2 Preset Parameters for DGi Secondary Controller

[0127]

[0128] The aforementioned distributed quadratic control theory has the following characteristics:

[0129] (1) The secondary control based on the consensus algorithm cannot execute the negative power reference value.

[0130] In the above-mentioned secondary control based on the consensus algorithm, if only the power calculation part is considered and the frequency and voltage calculation parts are ignored, the corresponding consensus algorithm principle is Equation (1). When the power setpoint is negative ( When ), the corresponding consensus algorithm principle becomes:

[0131] (9)

[0132] It is easy to prove that the characteristic matrix of the system in equation (9) must have positive eigenvalues, that is, the system must be unstable.

[0133] Since the calculation methods for reactive power and active power are completely symmetrical, the following explanation will only use active power as an example. In reality, reactive power can also be analyzed or solved using the exact same methods. In actual microgrids, energy storage systems sometimes need to absorb power, in which case their... However, existing methods cannot handle cases where the power setpoint is negative. To address this issue, the controller algorithm mentioned above is improved to expand its acceptable power reference value range.

[0134] (2) A sudden decrease in the power setpoint will reduce system stability and may even lead to system instability.

[0135] The secondary control frequency active power control formula (3) is written in the following form:

[0136] (10)

[0137] Assuming a fixed active power control gain is used For steady state, we can consider the form of control equation (3), but after three control actions, new control signals are issued to each DG. Considering the form of equation (10), the power reference value The control gain will be affected during the transient process. This has an impact. When the active power reference value of the distributed generation DGi suddenly decreases, it will be equivalent to the control gain during the transient process. Sudden increase, due to control gain Excessive levels can cause system instability, so if The sudden increase is relatively large (i.e., the power reference value) A sudden and large decrease will still leave the system at risk of instability.

[0138] To address this issue, an adaptive parameter determined by the power reference value was designed. When the power reference value suddenly drops, the power control gain value can be reduced synchronously, effectively limiting the sudden change in control gain and greatly enhancing the system stability when the power reference value suddenly decreases.

[0139] (3) The dynamic adjustment speed of the consensus algorithm system is limited.

[0140] The four control gains directly determine the adjustment speed of the corresponding data. However, there is an upper limit to the fixed control gains. Exceeding the upper limit will lead to system instability, and approaching the upper limit will cause the system to oscillate continuously. Therefore, to comprehensively consider system stability, the magnitude of the control gains needs to be limited, which restricts the system adjustment speed. In particular, the higher the communication latency, the worse the system stability and the lower the upper limit of the system adjustment speed. Therefore, for a fixed control gain, under the premise of ensuring system stability, the fastest system adjustment speed that can be achieved may still not meet the speed requirements due to the negative effects of communication latency and other factors.

[0141] Therefore, an adaptive parameter related to the actual power and the power reference value was designed. This parameter accelerates the system's adjustment speed when the actual power differs significantly from the power reference value, and reduces the system's adjustment speed when the actual power is close to the power reference value, thereby reducing overshoot and system oscillation. This enhances the system's dynamic adjustment speed without weakening system stability. This adaptive parameter can also be applied to frequency and voltage regulation, but since frequency and voltage regulation speeds usually meet basic requirements, this invention only discusses its application in power distribution.

[0142] Figure 1 The flowchart of the microgrid distributed secondary control method provided in the embodiments of the present invention mainly includes:

[0143] (1) Data collection

[0144] After the controller starts, it prioritizes collecting local DG data and communication neighborhood data. Power data uses per-unit values ​​(range [-1, 1]) to lay the foundation for negative power processing; reference values ​​come from the upper-level tertiary control (such as P). iref ).

[0145] (2) Calculation of correction items

[0146] Parallel computation of frequency correction term (dΩ) i / dt) and voltage correction term (dΨ) i / dt), each item is broken down into consistency calculation (recovery frequency / voltage) and power item calculation (precise allocation).

[0147] The power term adopts an improved form ((P) i +1) / (P iref +1), supports negative reference values.

[0148] (3) Adaptive parameter processing

[0149] K 1,i Calculation: Generated based on the minimum value of the neighborhood reference value, used to suppress the risk of sudden power reduction.

[0150] K 2,i Calculation: First calculate the normalization parameter k S,i This reflects the power balance of the entire network; then K is dynamically adjusted based on the deviation. 2,i This achieves a balance between acceleration and vibration suppression.

[0151] K 1,i and K 2,i Independent computation but synergistic effect, K 2,i The range is limited to [1, e] to ensure stability.

[0152] (4) Control output

[0153] Correction term Ω i Ψ i The output is sent to the local DG for primary droop control, achieving closed-loop frequency / voltage recovery and power distribution. It supports negative power operation (such as power absorption in energy storage) and stability under abrupt changes in operating conditions. See the performance verification reference. Figure 5c : Fast convergence after adding adaptive parameters.

[0154] The technical solution of this invention is described in detail below:

[0155] (1) An improved secondary control method based on consensus algorithm (with executable negative power setpoint)

[0156] It has been pointed out that the original control strategy cannot be set. To control the power absorbed by energy storage, this invention proposes an improved control strategy to solve this problem. Firstly, to facilitate unified consideration or calculation of data, all data from secondary control links (frequency, voltage, active power, reactive power) are expressed in per-unit values ​​during calculations; therefore, the power range is... The problem arises because changes in the sign of the coefficients alter the system characteristics. Therefore, the improvement objective is to ensure that the signs of all numerators and denominators remain constant during the secondary control calculation.

[0157] Therefore, it is possible to design all power data to be incremented by 1 before being included in the calculation, thus adjusting the power range. Mapped to .

[0158] Taking active power improvement (and reactive power improvement similarly) as an example, the improvement algorithm is introduced. In the improvement algorithm, equation (3) is updated as follows:

[0159] (11)

[0160] In equation (11), since Therefore, all denominators in the power calculation are greater than 0, thus avoiding the system instability problem caused by changes in the control strategy when the denominator is less than 0.

[0161] Since the role of the power supply's active power in secondary control has been altered, it is necessary to analyze the impact of the improved strategy on the power supply's active power allocation.

[0162] The steady-state active power allocation target of equation (11) is:

[0163] (12)

[0164] Combining the real-time power balance formula, the actual active power output of each DG can be calculated as follows:

[0165] (13)

[0166] There is no power deficit in the three power setting values, that is... At that time, it can be calculated from equation (13) That is, the actual power is equal to the power setting value.

[0167] When a power deficit occurs, let the power deficit be... ,Right now At this point, the power distribution is as follows:

[0168] (14)

[0169] That is, in steady state, the power deficit can be calculated according to ( The +1) proportional ratio is automatically distributed among the power sources.

[0170] Therefore, when the load power changes, all available DGs can be mobilized to share the power deficit, and the allocation amount is related to ( The +1 ratio is directly proportional and will not lead to distorted power distribution or excessive power in individual DGs.

[0171] (2) Adaptive parameters to enhance system stability

[0172] As mentioned above, when the power reference value is sent down from the upper layer, if the new power reference value is much smaller than the previous power reference value, it will lead to a decrease in the dynamic stability of the system or even instability. Therefore, in order to suppress the system instability problem caused by the control gain being too large when the active power setpoint suddenly decreases, a new adaptive parameter is introduced into equation (3). Equation (3) becomes:

[0173] (15)

[0174] in The adaptive parameters introduced are calculated as follows:

[0175] (16)

[0176] Assuming that the active power setpoint of a certain power source is the lowest among all power sources, and assuming that its node number is i, considering the secondary controller of this power source, then equation (16) is:

[0177] (17)

[0178] Substituting equation (17) into equation (15), we get:

[0179] (18)

[0180] This parameter effectively changes the power during calculation and does not affect the final parameter allocation. Because per-unit values ​​are used, Therefore, considering the expression of equation (15), the adaptive parameter can also be considered as... By reducing the control gain This slows down the system's adjustment speed, thereby increasing system stability.

[0181] If the improved quadratic control strategy, i.e., the control algorithm of equation (11), is adopted, then The expression (16) needs to be adjusted accordingly and becomes:

[0182] (19)

[0183] (3) Adaptive parameters to enhance the dynamic power distribution speed of the system

[0184] when and When the difference is significant, this adaptive parameter can effectively suppress system instability caused by excessive gain. However, this parameter can only suppress the system adjustment speed when the power setpoint changes abruptly. Furthermore, due to communication delays, the control parameter settings are limited, thus significantly restricting the system adjustment speed. To meet the requirements of dynamic system response, accelerate the system power adjustment speed, and maintain system stability, this adaptive parameter method is improved by introducing a new adaptive parameter. To enhance the system's adjustment speed, the calculation methods for the two adaptive parameters are as follows:

[0185] ( - )

[0186] ( - )

[0187] ( - )

[0188] ( - )

[0189] Where k is a parameter that can be flexibly set; k S,i is the normalization parameter of DGi.

[0190] If the proposed improved algorithm is adopted, then changes are required. The expression is shown in equation (19); for The calculation method can transform the normalized parameter expression into:

[0191] ( - )

[0192] Adaptive parameters Then, with max{P - k p P ref Positive correlation, meaning it is positively correlated with the system power difference; the larger the power difference, the stronger the adaptive parameter. The larger the value, the more flexible the system's power regulation speed can be. Setting k to be approximately inversely proportional to the power difference controls ln. The range is approximately [0, 1], and it is mapped by exponentiation. The value range of is approximately [1, e]. The upper limit of the parameter is limited so that excessively high parameters can affect system stability. Therefore, adaptive parameters are used. It can accelerate the system power regulation speed during dynamic changes and quickly adjust the adaptive parameters when the power of each DG approaches the power set value. The overshoot is subsequently reduced, which, in turn, enhances the tendency of the DG power to approach the power setpoint. Therefore, unlike increasing the constant control gain, this method does not directly reduce system stability.

[0193] (4) Explanation of the effects of the method of the present invention:

[0194] The test scenario is a four-node independent microgrid system, containing three controllable distributed generation (DG) systems, and the overall structure of the microgrid is as follows: Figure 2 As shown

[0195] Set up the equivalent topology for secondary control communication of the three DGs as follows: Figure 3 As shown.

[0196] The test is divided into three phases: 0-10s, no secondary control is executed; at 10s, secondary control is activated to restore frequency and voltage, and the energy storage power is allocated according to capacity by default, i.e., the per-unit power values ​​are equal; at 35s, a new power reference value is issued. Different power setpoints will be given for different tests to test the proposed method for enhancing the dynamic stability and power allocation speed of the system. Since power is used in the calculation in per-unit form in the design method, both the nominal and per-unit waveforms of active power are provided.

[0197] Test 1:

[0198] The reference values ​​for the power of the three energy storage units are shown in Table 3.

[0199] Table 3 Power Reference Values ​​for Test 1

[0200]

[0201] The active power of the test results is shown in Figure 4.

[0202] from As shown in (a), both the traditional and improved strategies can achieve the function of adjusting the power to be allocated according to capacity (i.e., the power reference value is 1 by default). However, when the power reference value is negative, the power supply in the traditional strategy immediately becomes unstable and the system crashes directly; while the improved strategy can better execute the issued power reference value and adjust each DG to be near the power reference value, as shown in Figure 4(b).

[0203] Test 2:

[0204] The reference values ​​for the power of the three energy storage units are shown in Table 4.

[0205] Table 4 Power Reference Values ​​for Test 2

[0206]

[0207] In (1) no adaptive parameter is applied, and in (2) only the adaptive parameter K is used. 1,i (3) Using adaptive parameter K 1,i and K 2,i The system was tested under three settings. The results are shown in Figure 5.

[0208] As can be seen from Figure 5(a), without the addition of adaptive parameters, after the power reference value is issued, the equivalent control parameter increases due to the small power setpoint, and the system fails to recover to the stable point after severe oscillation.

[0209] Observe Figure 5(b), and add adaptive parameters. Afterwards, the system remained in a relatively stable state. After the power reference value was issued, the power supply slowly adjusted to the set value, greatly enhancing the system's stability. However, the adjustment speed was slow, exhibiting a slow exponential change trend, and its upper limit was constrained by communication delay.

[0210] Add adaptive parameters and Then, as shown in Figure 5(c), it can be seen that within a short period of time after the power reference value is issued, the actual power differs significantly from the power reference value. This enhances the system's adjustment speed. Once the power approaches the power reference value, The system reduces the tendency of the increased power to approach the reference value while maintaining system stability.

[0211] Will join The per-unit changes in the active power of energy storage before and after are compared in a single graph, such as... Figure 6 As shown. With the addition of adaptive parameters... Subsequently, whether in the default secondary control mode or under conditions of sudden power setpoint reduction, the adjustment speed within a certain time period is significantly faster than when no secondary control was applied. Furthermore, after the power quickly approaches a certain range of the reference value, it can switch to slow and precise adjustment to the reference value, ensuring system stability.

[0212] The improved strategy provided in this embodiment addresses the problem that traditional strategies cannot execute negative power reference values. It expands the range of executable power reference values, enabling the system to execute negative power reference values ​​normally. Furthermore, by changing the power range, it improves system stability while reducing the adjustment speed.

[0213] Through adaptive parameters and This can prevent system instability under conditions of sudden changes in power setpoints or unreasonable settings, and can accelerate the process of system power distribution according to the setpoint. Since the two parameters are independent of the algorithm's internal logic, they can be considered to affect system performance by controlling the adjustment speed under different conditions. Therefore, the two adaptive parameters do not affect the system's steady-state control objective, and can also be applied in the same way to reactive power control or other algorithms. Theoretically, frequency and voltage do not have problems similar to sudden changes in power setpoints, therefore the adaptive parameters... Not suitable for frequency and voltage recovery. However, adaptive parameters... The design method can also be applied to frequency and voltage regulation, accelerating the recovery of system frequency and voltage, and providing a new approach for the design of adaptive parameters for secondary control.

[0214] This invention also provides a computer-readable medium. The computer-readable medium stores a computer program, which, when executed by a processor, implements the steps of any of the microgrid distributed secondary control methods described in the above embodiments. The computer-readable storage medium can be volatile or non-volatile.

[0215] This invention also provides a computer program product, including computer-readable code, or a non-volatile computer-readable storage medium carrying computer-readable code. When the computer-readable code is run in the processor of an electronic device, the processor in the electronic device executes the microgrid distributed secondary control method described above.

[0216] Those skilled in the art will understand that all or some of the steps, systems, and apparatuses disclosed above, and their functional modules / units, can be implemented as software, firmware, hardware, or suitable combinations thereof. In hardware implementations, the division between functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed collaboratively by several physical components. Some or all physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit (ASIC). Such software can be distributed on a computer-readable storage medium, which may include computer storage media (or non-transitory media) and communication media (or transient media).

[0217] As is known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable program instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), static random access memory (SRAM), flash memory or other memory technologies, portable compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, it is known to those skilled in the art that communication media typically contain computer-readable program instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0218] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0219] The computer program instructions used to perform the operations of this invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing state information from the computer-readable program instructions. This electronic circuitry can execute the computer-readable program instructions to implement various aspects of the invention.

[0220] The computer program product described herein can be implemented specifically through hardware, software, or a combination thereof. In one alternative embodiment, the computer program product is specifically embodied in a computer storage medium; in another alternative embodiment, the computer program product is specifically embodied in a software product, such as a software development kit (SDK), etc.

[0221] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0222] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0223] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0224] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction, which contains one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0225] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in conjunction with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in conjunction with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of the invention as set forth in the appended claims.

[0226] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A distributed secondary control method for microgrids, characterized in that, include: S1, Data Acquisition: Obtain real-time operating data of the distributed generation (DG), including: the frequency ω of the local DG. i Voltage V i Active power per unit value P i Reactive power per unit value Q i ; Corresponding data ω of the neighborhood DG j V j P j Q j， where j∈N i N i In order to cooperate with DG i The set of DG numbering for communication; the local DG power reference per-unit value P issued by the upper layer. iref and Q iref and the corresponding reference value P of the neighborhood DG jref and Q jref ; S2, Correction term generation: Frequency correction term Ω is generated based on the consensus algorithm. i and voltage correction term Ψ i The frequency correction term Ω i The calculation formula is: ； The voltage correction term Ψ i The calculation formula is: ； Among them, all power per unit values ​​P i Q i P iref Q iref The values ​​of are all in the range of [-1, 1]; Let J be the edge weight from node j to node i. This is the root node identifier. For frequency control gain, For active power control gain, Voltage-controlled gain, For reactive power control gain; S3, control output: Frequency correction term Ω i and voltage correction term Ψ i The droop control fed back to the local DG enables frequency / voltage recovery and power distribution.

2. The microgrid distributed secondary control method according to claim 1, characterized in that, Since the role of the power supply's active power in the secondary control has been changed, it is necessary to analyze the impact of the improved strategy on the power supply's active power allocation. The objective of steady-state active power allocation is: ； Combining the real-time power balance formula, the expression for the actual active power output of each DG is calculated as follows: ； There is no power deficit in the three power setting values, that is... At that time, the actual active power output of each DG can be calculated from the expression of the active power output. That is, the actual power is equal to the power setpoint, where, The total load power, Let be the rated power of the i-th DG; When a power deficit occurs, let the power deficit be... ,Right now At this point, the power distribution is as follows: ； That is, in steady state, the power deficit is calculated according to ( The +1) proportional ratio is automatically distributed among the power sources.

3. The microgrid distributed secondary control method according to claim 1, characterized in that, The method further includes, in the frequency correction term Ω i The first adaptive parameter K is introduced in the calculation. 1,i ; Updated frequency correction term Ω i for: ； Among them, K 1,i Used to suppress system instability caused by a sudden decrease in the power reference per unit value.

4. The microgrid distributed secondary control method according to claim 3, characterized in that, The first adaptive parameter K 1,i The implementation includes the following steps: Obtaining the per-unit reference value for neighborhood power: Obtaining Distributed Power Generation (DG) i Power reference per unit value P iref and its communication neighborhood DG j Power reference per unit value P jref ; Parameter calculation: K is determined through minimization. 1,i Value: ； The K 1,i By dynamically reducing the equivalent control gain, the risk of system instability caused by a sudden decrease in the power reference per unit value is suppressed.

5. The microgrid distributed secondary control method according to claim 3, characterized in that, The method further includes: in the frequency correction term Ω i A second adaptive parameter K is further introduced in the calculation. 2,i Update the frequency correction term to: ； in, k is a configurable coefficient, k S,i These are the normalized parameters.

6. The microgrid distributed secondary control method according to claim 5, characterized in that, The second adaptive parameter K 2,i By normalizing parameter k S,i Dynamically adjust the normalized parameter k S,i The formula is: ； When the deviation between the actual power and the reference value increases, K 2,i Increase to accelerate adjustment; when the deviation decreases, K 2,i Reduce to suppress overshoot.

7. The microgrid distributed secondary control method according to claim 6, characterized in that, The K 2,i The value of is in the range [1, e], and the value of k satisfies lnK. 2,i ∈[0,1], ensuring a balance between system stability and dynamic response speed.

8. The microgrid distributed secondary control method according to claim 5, characterized in that, The adaptive parameter K 1,i and K 2,i The same applies to reactive power control, and its calculation method is symmetrical to that of active power control.

9. The microgrid distributed secondary control method according to claim 8, characterized in that, The adaptive parameter K 1,i and K 2,i The same applies to reactive power control, and its calculation method is symmetrical to that of active power control, specifically including: The adaptive parameter K 1,i After being applied to the reactive power control stage, the updated voltage correction term Ψ i for: ； The adaptive parameter K 2,i After being applied to the reactive power control stage, the updated voltage correction term Ψ i for: ； K 1,i The variable in the calculation is replaced with reactive power, that is: ； K 2,i In the calculation, the variable is replaced with reactive power, that is: ； ； The replacement ensures that reactive power control and active power control are logically consistent in the application of adaptive parameters.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a computer, causes the computer to perform the microgrid distributed secondary control method as described in any one of claims 1 to 9.

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