A Mobile Target Defense Method, System and Storage Medium with Measurement Encoding Enhancement

Abstract

The present invention provides a method, a system and a storage medium for measurement coding enhanced moving target defense. The method includes the following steps: constructing a measurement coding enhanced moving target defense model for power grid data injection attacks; analyzing the detection conditions of power grid data injection attacks; analyzing the deficiencies of the moving target defense model in detecting power grid data injection attacks according to the special case of solely adopting moving target defense; determining the design criterion of the coding matrix when the coding matrix is a diagonal matrix; constructing an optimization problem of measurement coding enhanced moving target defense; designing a heuristic solution algorithm to reduce the comprehensive cost and improve the detection ability of power grid data injection attacks; and performing state estimation and attack detection on the received power grid data according to the optimized measurement coding and moving target defense strategy to detect potential power grid data injection attacks in the data transmission process.

Description

Technical Field

[0001] The present invention relates to the field of power cyber-physical system network attack defense, and in particular, to a mobile target defense method with enhanced measurement coding, a mobile target defense system with enhanced measurement coding, and a computer-readable storage medium. Background Art

[0002] With the continuous progress of communication, control, and computing technologies, intelligent components, sensor measurement units, and communication technologies have been widely applied to the power system, making the power grid a typical power cyber-physical system. When the Supervisory Control And Data Acquisition System (SCADA) in the power system was designed, network security issues were not fully considered, lacking security protection such as access control and authentication. Therefore, the measurement data in the power grid is easily tampered with by attackers during the transmission in the SCADA system, resulting in an increase in the operating cost of the power grid and even causing the problem of "blackout" of the power grid.

[0003] Network attacks in the power system can be divided into stealth attacks, availability attacks, and integrity attacks. Among them, integrity attacks mislead the operation of the power system secretly by tampering with power grid measurement data or control instructions, and have the most serious impact on the power grid. For example, False Data Injection Attacks (FDIAs), as a typical integrity attack, can mislead the result of power grid state estimation without triggering the bad data detection alarm in state estimation by collaboratively tampering with measurement data such as branch power flow and node injection power, causing the control center to misjudge the current state of the power grid and affecting the safe and stable operation of the power system. Given that the existing bad data detection mechanism is difficult to detect false data injection attacks in the power grid, it is of great significance to study effective attack detection methods to timely discover potential network attack threats and ensure the security of the power system.

[0004] Regarding the detection of false data injection attacks, some scholars have conducted relevant research and proposed various attack detection methods. Among them, the moving target defense method utilizes the dependence on the power grid measurement matrix information during the construction of data injection attacks, and with the help of the ability of distributed flexible AC transmission systems (D-FACTS) to adjust branch impedance, actively changes the power grid measurement equation, increases the uncertainty of the power system, and improves the detection ability against data injection attacks. Since the detection ability of the moving target defense against attacks is limited by the topology of the power grid itself, for some power grid topologies, the attack detection ability of the moving target defense method is limited. Therefore, aiming at the deficiency of the existing moving target defense method in the detection ability of data injection attacks, designing a moving target defense method with enhanced measurement coding to improve the detection ability against data injection attacks is an urgent problem to be solved by those skilled in the art.

[0005] To overcome the above-mentioned defects existing in the prior art, the present invention provides a moving target defense technology with enhanced measurement coding, which can make up for the deficiencies of the existing moving target defense method in data injection attack detection, gives a method for enhancing the attack detection ability of the moving target defense by using measurement coding, constructs an optimization problem for the moving target defense with enhanced measurement coding, designs a heuristic algorithm to achieve efficient solution, reduces the number of measurements required for coding and the power grid losses caused by the moving target defense, and enhances the detection ability against data injection attacks at the lowest cost. Summary of the Invention

[0006] A brief overview of one or more aspects is given below to provide a basic understanding of these aspects. This overview is not an exhaustive survey of all contemplated aspects, and is neither intended to identify key or decisive elements of all aspects nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to a more detailed description to follow.

[0007] To overcome the above-mentioned defects existing in the prior art, the present invention provides a moving target defense technology with enhanced measurement coding, which can make up for the deficiencies of the existing moving target defense method in data injection attack detection, gives a method for enhancing the attack detection ability of the moving target defense by using measurement coding, constructs an optimization problem for the moving target defense with enhanced measurement coding, designs a heuristic algorithm to achieve efficient solution, reduces the number of measurements required for coding and the power grid losses caused by the moving target defense, and enhances the detection ability against data injection attacks at the lowest cost.

[0008] Specifically, the measurement coding enhanced mobile target defense method provided by the first aspect of the present invention includes the following steps: constructing a measurement coding enhanced mobile target defense model for power grid data injection attacks; analyzing the detection conditions of the power grid data injection attacks to determine the requirements for the number of transmission line impedances for the required coded measurements and controls; analyzing the deficiencies of the mobile target defense model in detecting power grid data injection attacks according to the special case of solely adopting mobile target defense; determining the design criteria of the coding matrix when the coding matrix is a diagonal matrix; constructing an optimization problem of measurement coding enhanced mobile target defense, and reducing the comprehensive cost of measurement coding and mobile target defense on the premise of ensuring the detection ability of power grid data injection attacks; designing a heuristic solution algorithm, and optimizing the measurement coding and mobile target defense strategies by iteratively coding a new measurement or changing the impedance of a new transmission line, so as to reduce the comprehensive cost and improve the detection ability of the power grid data injection attacks; and performing state estimation and attack detection on the received power grid data according to the optimized measurement coding and mobile target defense strategies to detect potential power grid data injection attacks during the data transmission process.

[0009] Preferably, in an embodiment of the present invention, the measurement coding enhanced mobile target defense model is defined as:

[0010]

[0011] Wherein, is the true measurement data in the power grid state estimation, including the branch active power and the node active injection power, is the reversible coding matrix in the measurement coding, is the change amount of the true measurement data caused by the power grid data injection attack, is the measured value tampered by the attacker in the power grid state estimation,

[0012] When the measurement matrix in the power grid state estimation is , the change amount of the true measured value satisfies:

[0013]

[0014] Wherein, is the change amount of the node voltage phase angle expected by the attacker,

[0015] When the mobile target defense changes the impedance values of some branches, the measurement data under the mobile target defense is expressed as:

[0016]

[0017] Wherein, The measurement matrix corresponding to changing the impedance values of some branches for moving target defense, and the node voltage phase angle characterizes the power grid system state, and the measurement noise satisfies a zero-mean Gaussian distribution,

[0018] The steps of constructing the measurement coding enhanced moving target defense model for power grid data injection attack include:

[0019] In response to the moving target defense changing the measurement matrix from to , the measurement coding enhanced moving target defense model is expressed as:

[0020]

[0021] where, and are the measurement matrices before and after the moving target defense changes the impedance values of some branches, respectively.

[0022] Preferably, in an embodiment of the present invention, in the case of no measurement noise, the measurement coding enhanced moving target defense model is expressed as:

[0023]

[0024] The detectability of the power grid data injection attack is defined as:

[0025]

[0026] where, are two different power grid system state values. When and only when

[0027]

[0028] is the matrix rank operation, is the number of system states in the power grid,

[0029] The set of measurement data processed in the measurement coding enhanced moving target defense satisfies:

[0030]

[0031] where, is the cardinality operation of the set.

[0032] Preferably, in an embodiment of the present invention, when only the moving target defense strategy is adopted, the detectable condition of the power grid data injection attack is expressed as:

[0033]

[0034] For a power grid where the active power of branch circuits and the injected active power of nodes are both measured, the rank of the combined matrix of matrix and matrix satisfies

[0035]

[0036] where and are sub - matrices composed of the rows corresponding to the active power measurements of branch circuits in matrix and matrix respectively, is the number of branch circuits in the power grid, , and are sub - matrices composed of the rows corresponding to the injected active power measurements of nodes in matrix and matrix respectively.

[0037] Preferably, in an embodiment of the present invention, in the measurement - coding - enhanced moving target defense, it is assumed that the rank of the current combined matrix satisfies:

[0038]

[0039] For the encoded measurement set , when using a coding factor that is neither 0 nor 1 to code the th measurement, , the rank of the encoded combined matrix does not depend on the specific value of the coding factor . Thus, the design criterion is determined to enhance the detection ability of the moving target defense against the power grid data injection attack, where is the th diagonal element in the coding matrix .

[0040] Preferably, in an embodiment of the present invention, the measurement - coding - enhanced moving target defense is represented as the following optimization problem:

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048] Among them, is the change amount of the branch impedance in moving target defense, and are the weight coefficients of the measurement coding and the cost related to moving target defense respectively. PLIS is the reactance sensitivity parameter, indicating the influence of reactance change on the grid loss. is the measurement arrangement matrix, indicating the branch power flow and node injection power to be measured. is the incidence matrix determined by the grid topology, characterizing the connection relationship between nodes. is the feasible region of the branch impedance change.

[0049] Preferably, in an embodiment of the present invention, the steps of the design heuristic solution algorithm for optimizing the measurement coding and the moving target defense strategy by iteratively coding a new measurement or changing the impedance of a new transmission line include: Let the currently encoded measurement set be , the coding matrix be , and the measurement matrix after the moving target defense changes the impedance of some branches be . Respectively search for the costs corresponding to improving the rank of the combined matrix by coding a new measurement or changing the impedance of a certain branch newly; in the process of improving the rank of the combined matrix by coding a new measurement, use the design criterion of the diagonal matrix to design a heuristic search algorithm, and obtain the coding method for increasing the rank of the combined matrix with the lowest coding cost by trying measurements outside the set of non-0 and non-1 and testing the rank of the new combined matrix. The process is expressed in the following form:

[0050]

[0051] Among them, indicates that the newly encoded measurement can increase the rank of the combined matrix, indicates that the newly encoded measurement cannot increase the rank of the combined matrix, is the measurement required to increase the rank of the combined matrix with the minimum cost, is the increase amount of the coding cost, is the new coding matrix;

[0052] In the process of increasing the rank of the combined matrix by newly changing the impedance of a branch, a method of increasing the rank of the combined matrix with the minimum grid loss is obtained by attempting to modify the impedance of the target branch to any value different from the current value and checking the rank of the new combined matrix. The process is expressed in the following form:

[0053]

[0054] Wherein, represents that newly changing the impedance of a branch can increase the rank of the combined matrix, represents that newly changing the impedance of a branch cannot increase the rank of the combined matrix, l is the impedance of the branch that needs to be changed to increase the rank of the combined matrix at the minimum cost, is the corresponding minimum grid loss increment, is the new branch impedance change amount, is the new measurement matrix, is the set of branches whose impedance has not been changed;

[0055] In response to and , when , the measurement coding method is used to increase the rank of the combined matrix and update the relevant parameters:

[0056]

[0057] Otherwise, the moving target defense method is used to increase the rank of the combined matrix and update the relevant parameters:

[0058]

[0059] In response to and only one of which is 1, the corresponding method with a value of 1 is used to increase the rank of the combined matrix and update the relevant parameters; and if and , or the rank of the combined matrix reaches , terminate and output the encoded measurement set and the change amount of the branch impedance .

[0060] Preferably, in an embodiment of the present invention, the step of performing state estimation and attack detection on the received grid data according to the optimized measurement coding and moving target defense strategy to detect potential grid data injection attacks during data transmission includes: updating the coding matrix required for state estimation application in control and the new measurement matrix in moving target defense; decoding the received measurement data:

[0061]

[0062] Based on the weighted least squares method, perform state estimation and solution on the decoded data to determine the optimal system state:

[0063]

[0064] In response to the optimal value of the state estimation satisfying the following formula, it is considered that the measurement data transmission process has not been tampered with by false data injection attacks

[0065]

[0066] where is the attack detection threshold set according to the degrees of freedom and detection confidence level in the chi-square distribution.

[0067] In addition, the above-mentioned measurement coding enhanced mobile target defense system provided according to the second aspect of the present invention includes a memory and a processor. Computer instructions are stored on the memory. The processor is connected to the memory and is configured to execute the computer instructions stored on the memory to implement the measurement coding enhanced mobile target defense method provided by any one of the above embodiments.

[0068] In addition, computer instructions are stored on the above-mentioned computer-readable storage medium provided according to the third aspect of the present invention. When the computer instructions are executed by a processor, the measurement coding enhanced mobile target defense method provided by any one of the above embodiments is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] After reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings, the above features and advantages of the present invention can be better understood. In the drawings, the components are not necessarily drawn to scale, and components with similar related characteristics or features may have the same or similar reference numerals.

[0070] Figure 1 Shows a schematic flow chart of a measurement coding enhanced mobile target defense method provided according to some embodiments of the present invention.

[0071] Figure 2 Shows an architecture diagram of a measurement coding enhanced mobile target defense system provided according to some embodiments of the present invention.

[0072] Figure 3 Shows a schematic diagram of the rank of the combined matrix in a measurement coding enhanced mobile target defense method provided according to some embodiments of the present invention.

[0073] Figure 4Shows a schematic diagram of measurement coding and the protection cost of moving target defense in the measurement coding enhanced moving target defense method provided according to some embodiments of the present invention.

[0074] Figure 5 Shows the detection success rate of the measurement coding enhanced moving target defense method provided according to some embodiments of the present invention against data injection attacks in the IEEE 14 - node test system.

[0075] Figure 6 Shows the detection success rate of the measurement coding enhanced moving target defense method provided according to some embodiments of the present invention against data injection attacks in the IEEE 57 - node test system. Detailed implementation manners

[0076] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Although the description of the present invention will be introduced in conjunction with preferred embodiments, this does not mean that the features of this invention are limited to this implementation manner. On the contrary, the purpose of introducing the invention in conjunction with the implementation manner is to cover other alternatives or modifications that may be extended based on the claims of the present invention. To provide a deep understanding of the present invention, many specific details will be included in the following description. The present invention can also be implemented without using these details. In addition, to avoid confusing or obscuring the focus of the present invention, some specific details will be omitted in the description.

[0077] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0078] In addition, the "upper", "lower", "left", "right", "top", "bottom", "horizontal", and "vertical" used in the following description should be understood as the orientations shown in this paragraph and the related drawings. This relative term is only for the convenience of description, and it does not mean that the device described needs to be manufactured or operated in a specific orientation, so it should not be understood as a limitation to the present invention.

[0079] It is understood that although terms such as "first", "second", "third", etc. may be used herein to describe various components, regions, layers, and / or parts, these components, regions, layers, and / or parts should not be limited by these terms, and these terms are only used to distinguish different components, regions, layers, and / or parts. Therefore, the first component, region, layer, and / or part discussed below may be referred to as the second component, region, layer, and / or part without departing from some embodiments of the present invention.

[0080] As described above, the power system faces serious network security. Existing bad data detection mechanisms are difficult to detect false data injection attacks in the power grid. Studying effective attack detection methods to timely discover potential network attack threats is of great significance for ensuring the security of the power system. Since the attack detection ability of moving target defense is limited by the topology of the power grid itself, for some power grid topologies, the attack detection ability of the moving target defense method is limited. Therefore, aiming at the deficiency of the existing moving target defense method in detecting data injection attacks, designing a moving target defense method with enhanced measurement coding to improve the detection ability of data injection attacks is an urgent problem for those skilled in the art to solve.

[0081] To overcome the above-mentioned defects existing in the prior art, the present invention provides a moving target defense technology with enhanced measurement coding, which can make up for the deficiency of the existing moving target defense method in detecting data injection attacks, gives a method to enhance the attack detection ability of moving target defense by using measurement coding, constructs an optimization problem for enhancing moving target defense with measurement coding, designs a heuristic algorithm to achieve efficient solution, reduces the number of measurements of the required coding and the power grid loss caused by moving target defense, and enhances the detection ability of data injection attacks at the lowest cost.

[0082] In some non-limiting embodiments, the above-mentioned moving target defense method with enhanced measurement coding provided by the first aspect of the present invention can be implemented via the above-mentioned moving target defense system with enhanced measurement coding provided by the second aspect of the present invention. Specifically, the moving target defense system with enhanced measurement coding is configured with a memory and a processor. The memory includes but is not limited to the above-mentioned computer-readable storage medium provided by the third aspect of the present invention, on which computer instructions are stored. The processor is connected to the memory and is configured to execute the computer instructions stored on the memory to implement the moving target defense method with enhanced measurement coding provided by the first aspect of the present invention.

[0083] Please refer to Figure 1 and Figure 2 , Figure 1 which shows a schematic flowchart of a moving target defense method with enhanced measurement coding provided by some embodiments of the present invention. Figure 2The architecture diagram of a measurement coding enhanced mobile target defense system provided according to some embodiments of the present invention is shown.

[0084] As Figure 1 , Figure 2 shown, the measurement coding enhanced mobile target defense system provided by the present invention first constructs a measurement coding enhanced mobile target defense model for power grid data injection attacks. By constructing the measurement coding enhanced mobile target defense model, the capabilities of existing mobile target defense methods in data injection attack detection are evaluated to make up for their deficiencies. Here, the measurement coding enhanced mobile target defense model is defined as:

[0085]

[0086] where, is the true measurement data in power grid state estimation, including branch active power and node active injection power, is the reversible coding matrix in measurement coding, is the change amount of the true measurement data caused by the power grid data injection attack, is the measured value tampered by the attacker in power grid state estimation.

[0087] Here, since there is a bad data detection module arranged in power grid state estimation, the change amount of the true measured value caused by the power grid data injection attack needs to meet the concealment condition to avoid being discovered by the above detection mechanism. Therefore, when the measurement matrix in power grid state estimation is , the change amount of the true measured value satisfies:

[0088]

[0089] where, is the change amount of the node voltage phase angle expected by the attacker.

[0090] Then, since the measurement matrix is related to the branch impedance value, after the mobile target defense changes the impedance values of some branches, the measurement matrix changes from to . Therefore, when the mobile target defense changes the impedance values of some branches, the measurement data under the mobile target defense is expressed as:

[0091]

[0092] where, is the measurement matrix corresponding to the change of the impedance values of some branches by the mobile target defense, the node voltage phase angle characterizes the power grid system state, the measurement noise Satisfies the zero-mean Gaussian distribution.

[0093] Since it is difficult for an attacker to obtain accurate measurement matrix information in real time in the power grid state estimation, when the moving target defense changes the measurement matrix from to the measurement matrix information obtained by the attacker is still , the power grid data injection attack designed by the attacker can still satisfy formula (2). Here, the steps to construct the measurement coding enhanced moving target defense model (1) for power grid data injection attacks include:

[0094] In response to the moving target defense changing the measurement matrix from to , the measurement coding enhanced moving target defense model is expressed as:

[0095]

[0096] where and are the measurement matrices before and after the moving target defense changes the impedance values of some branches respectively.

[0097] After that, the measurement coding enhanced moving target defense system provided by the present invention analyzes the detection conditions of power grid data injection attacks to determine the requirements for the number of impedance of the encoded measurement and controlled transmission lines, so as to give a method for enhancing the attack detection ability of the moving target defense by measurement coding. In a preferred embodiment, in the case of no measurement noise, the measurement coding enhanced moving target defense model (4) is expressed as:

[0098]

[0099] For model (5), for any , and ∆θ, the detectability of the power grid data injection attack is defined as:

[0100]

[0101] where are two different power grid system state values. Then, according to the detectability condition (6), when and only when

[0102]

[0103] the power grid data injection attack can be detected, where is the matrix rank operation, is the number of system states in the power grid.

[0104] Let To measure the set of measurement data processed in measurement-coded enhanced moving target defense, the set of measurement data is either the coded measurement set or the measurement set with the impedance of the branch in the moving target defense changed. To meet the detection condition (7) of data injection attack, the set of measurement data processed in measurement-coded enhanced moving target defense shall satisfy:

[0105]

[0106] wherein, is the potential operation of the set.

[0107] Please continue to refer to Figure 1 and Figure 2 , and according to the special case of adopting moving target defense alone, analyze the deficiencies of the moving target defense model in detecting power grid data injection attacks.

[0108] Here, when adopting the moving target defense strategy alone, the detectable condition (7) of power grid data injection attack is expressed as:

[0109]

[0110] For a power grid where both the branch active power and the node injected active power are measured, the rank of the combined matrix of matrix and matrix satisfies

[0111]

[0112] wherein, and are respectively the sub-matrices composed of the rows corresponding to the branch active power measurements in matrix and matrix , is the number of branches in the power grid, , and are respectively the sub-matrices composed of the rows corresponding to the node injected active power measurements in matrix and matrix . Further, when the number of branches in the power grid, formula (9) cannot be satisfied. Therefore, for the above power grid, relying solely on moving target defense cannot effectively detect power grid data injection attacks that meet the stealth condition (2).

[0113] Furthermore, in the case where the coding matrix is a diagonal matrix, determine the design criterion of the coding matrix. By adopting a diagonal coding matrix, enhance the ability of moving target defense in attack detection. In measurement-coded enhanced moving target defense (5), assume that the rank of the current combined matrix satisfies:

[0114]

[0115] In the encoded measurement set when a non - zero and non - one encoding factor is used to encode the th measurement, the rank of the encoded combined matrix does not depend on the specific value of the encoding factor Thereby, the design criterion is determined to enhance the detection ability of the moving target defense against the power grid data injection attack. Here, is the th diagonal element in the encoding matrix .

[0116] After that, an optimization problem for enhancing the moving target defense with measurement encoding is constructed. Under the premise of ensuring the detection ability against the power grid data injection attack, the comprehensive cost of measurement encoding and moving target defense is reduced. Specifically, the moving target defense with enhanced measurement encoding is represented as the following optimization problem, so as to minimize the protection cost and the impact on the power grid operation while ensuring the detection ability against the data injection attack:

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124] where, is the change amount of the branch impedance in the moving target defense, is the set of encoded measurements, and are the weight coefficients of the costs related to measurement encoding and moving target defense respectively. PLIS is the reactance - sensitive parameter, indicating the impact of reactance change on the power grid loss, is the measurement layout matrix, indicating the branch power flow and node injection power to be measured, is the incidence matrix determined by the power grid topology, characterizing the connection relationship between nodes, is the feasible region of the branch impedance change.

[0125] Furthermore, constraint (13) ensures the detection ability of the measurement-coded enhanced moving target defense method against data injection attacks. Constraint (14) represents the relationship between the measurement equation and the branch impedance. (14)-(16) represent the association between the measurement matrix and the branch impedance. (17) and (18) give the constraints on the coding factors in the diagonal coding matrix.

[0126] Then, a heuristic solution algorithm is designed to optimize the measurement coding and the moving target defense strategy by iteratively coding a new measurement or changing the impedance of a new transmission line, so as to reduce the comprehensive cost and enhance the detection ability against power grid data injection attacks.

[0127] Furthermore, the steps of optimizing the measurement coding and the moving target defense strategy by iteratively coding a new measurement or changing the impedance of a new transmission line in the above-mentioned designed heuristic solution algorithm include:

[0128] Let the currently encoded measurement set be , the coding matrix be , and the measurement matrix after the moving target defense changes the impedance of some branches be , respectively search for the costs corresponding to improving the rank of the combined matrix by newly coding a measurement or newly changing the impedance of a certain branch;

[0129] In the process of improving the rank of the combined matrix by newly coding a measurement, use the design criterion of the diagonal matrix to design a heuristic search algorithm, and obtain a coding method that increases the rank of the combined matrix with the lowest coding cost by trying measurements outside the set of non-0 and non-1 and checking the rank of the new combined matrix. Its process is expressed in the following form:

[0130]

[0131] where, indicates that the newly coded measurement can increase the rank of the combined matrix, indicates that the newly coded measurement cannot increase the rank of the combined matrix, is the measurement to be coded to increase the rank of the combined matrix with the minimum cost, is the increase amount of the coding cost, is the new coding matrix;

[0132] In the process of improving the rank of the combined matrix by newly changing the impedance of a branch, obtain a method that increases the rank of the combined matrix with the minimum power grid loss increase by trying to modify the impedance of the target branch to any value different from the current value and checking the rank of the new combined matrix. Its process is expressed in the following form:

[0133]

[0134] Among them, indicates that newly changing the impedance of a branch can increase the rank of the combined matrix, indicates that newly changing the impedance of a branch cannot increase the rank of the combined matrix, l is the impedance of the branch that needs to be changed to increase the rank of the combined matrix at the minimum cost, is the corresponding minimum power grid loss increment, is the new branch impedance change amount, is the new measurement matrix, is the set of branches whose impedances have not been determined;

[0135] In response to and , when is true, the measurement coding method is adopted to increase the rank of the combined matrix and update the relevant parameters:

[0136] ,

[0137] Otherwise, the moving target defense method is adopted to increase the rank of the combined matrix and update the relevant parameters:

[0138]

[0139] In response to and only one of them is 1, the corresponding method with a value of 1 is adopted to increase the rank of the combined matrix and update the relevant parameters; and if and , or the rank of the combined matrix reaches , terminate and output the encoded measurement set and the change amount of the branch impedance .

[0140] By constructing a measurement coding enhanced moving target defense optimization problem and designing a heuristic solution algorithm for efficient solution, the measurement coding enhanced moving target defense method provided by the present invention can reduce the number of measurements required for coding and the power grid loss caused by moving target defense, and improve the detection ability against data injection attacks at a lower cost.

[0141] Please refer to Figure 3 and Figure 4 , Figure 3 shows a schematic diagram of the rank of the combined matrix in the measurement coding enhanced moving target defense method provided by some embodiments of the present invention, Figure 4 shows a schematic diagram of the protection cost of measurement coding and moving target defense in the measurement coding enhanced moving target defense method provided by some embodiments of the present invention.

[0142] In the test of a preferred embodiment, the weight coefficient for measuring the coding cost is set to , and the weight system for the moving target defense cost is set to . Referring to the reference average electricity price of $0.133 / kWh, the comprehensive cost within 10 years is ( ). As Figure 3 shows, the measurement coding enhanced moving target defense method provided by the present invention can significantly increase the rank of the combined matrix, thereby improving the attack detection ability. As Figure 4 shows, compared with the measurement coding method in the prior art, the cost of realizing the attack detection ability by the measurement coding enhanced moving target defense method provided by the present invention is significantly reduced.

[0143] Please continue to refer to Figure 1 and Figure 2 , the measurement coding enhanced moving target defense system provided by the present invention performs state estimation and attack detection on the received power grid data according to the optimized measurement coding and moving target defense strategy to detect potential power grid data injection attacks during the data transmission process. Specifically, update the coding matrix required for state estimation application in the update control and the new measurement matrix in the moving target defense; first, decode the received measurement data:

[0144]

[0145] After that, according to the weighted least squares method, perform state estimation solution on the decoded data to determine the optimal system state:

[0146]

[0147] Then, use the optimal value of the state estimation to detect potential false data injection attacks. According to the chi-square detection principle, in response to the optimal value of the state estimation satisfying the following formula, it is considered that the measurement data transmission process has not been tampered with by false data injection attacks

[0148]

[0149] where is the attack detection threshold set according to the degrees of freedom and detection confidence level in the chi-square distribution.

[0150] The following non-limiting preferred embodiments provided further elaborate on the measurement coding enhanced moving target defense system proposed by the present invention, verifying the improvement of the detection ability of the measurement coding enhanced moving target defense method provided by the present invention for data injection attacks.

[0151] Please refer to Figure 5 and Figure 6 , Figure 5Shows the detection success rate of the measurement coding enhanced moving target defense method provided according to some embodiments of the present invention against data injection attacks in the IEEE 14-node test system. Figure 6 Shows the detection success rate of the measurement coding enhanced moving target defense method provided according to some embodiments of the present invention against data injection attacks in the IEEE 57-node test system.

[0152] The measurement coding enhanced moving target defense system provided by the present invention is verified for direct current state estimation and alternating current state estimation applications respectively, and the detection effects of moving target defense, measurement coding, and measurement coding enhanced moving target defense methods against data injection attacks are compared. The data injection attacks constructed in the test are located in the undetectable space of the moving target defense to compare the enhancement of the attack detection ability of the measurement coding enhanced moving target defense method. The attack detection success rates of the measurement coding enhanced moving target defense method in the IEEE 14-node and IEEE 57-node systems are as Figure 5 、 Figure 6 shown. The designed measurement coding enhanced moving target method can significantly enhance the detection ability against data injection attacks and is applicable to direct current state estimation and alternating current state estimation scenarios, approaching the detection effect of measurement coding against data injection attacks at a lower cost.

[0153] Therefore, the measurement coding enhanced moving target defense method provided by the present invention can significantly improve the detection ability against data injection attacks at a lower cost and can be applied to direct current state estimation and alternating current state assault scenarios, with strong applicability.

[0154] In summary, the measurement coding enhanced moving target defense method provided by the present invention analyzes the detection conditions of data injection attacks in the measurement coding enhanced moving target defense, specifically designs the design criteria for the diagonal elements of the coding matrix in the coding matrix enhanced moving target defense method, and accordingly describes the attack detection problem of the measurement coding enhanced moving target defense as an optimization problem. Using the design criteria for the diagonal elements of the coding matrix, a heuristic search algorithm is designed to enhance the detection ability against data injection attacks at the lowest cost.

[0155] Although the above methods are illustrated and described as a series of actions for simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in a different order and / or concurrently with other actions not illustrated and described herein but understood by those skilled in the art.

[0156] Those skilled in the art will appreciate that information, signals, and data can be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips described throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0157] Those skilled in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, the various illustrative components, blocks, modules, circuits, and steps are described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and the design constraints imposed on the overall system. Skilled artisans may implement the described functionality in different ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

[0158] The foregoing description of the disclosure has been provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for measuring and encoding enhanced moving target defense, characterized in that Including the following steps: Construct a measurement coding enhanced moving target defense model for power grid data injection attacks; Analyze the detection conditions of the power grid data injection attack to determine the requirements for the number of transmission line impedances for the required coded measurements and controls; wherein, in the case of no measurement noise, the measurement coding enhanced moving target defense model is expressed as: Among them, is the measured value tampered by the attacker in the power grid state estimation, is the reversible coding matrix in the measurement coding, is the corresponding measurement matrix after the moving target defense changes the impedance values of some branches, is the node voltage phase angle, is the measurement matrix in the power grid state estimation, is the change amount of the node voltage phase angle expected by the attacker, The detectability of the power grid data injection attack is defined as: Among them, are two different power grid system status values, if and only if When the power grid data injection attack can be detected, where is the matrix rank operation, is the number of system states in the power grid A set of measurement data processed in the measurement-coding-enhanced moving target defense Satisfies: Among them, is the cardinality operation of the set; Based on the special case of solely adopting moving target defense, it is analyzed that the effective detection of power grid data injection attacks satisfying the concealment condition cannot be achieved solely relying on the moving target defense model; When the encoding matrix is a diagonal matrix, determine the design criterion of the encoding matrix, and the rank of the encoded combined matrix does not depend on the specific value of the encoding factor , where is the encoding matrix and the th diagonal element in Construct an optimization problem for measurement coding enhanced moving target defense to reduce the comprehensive cost of measurement coding and moving target defense on the premise of ensuring the detection ability of power grid data injection attacks; Design a heuristic solution algorithm to optimize the measurement coding and moving target defense strategies by iteratively coding a new measurement or changing the impedance of a new transmission line; and According to the optimized measurement coding and moving target defense strategies, perform state estimation and attack detection on the received power grid data to detect potential power grid data injection attacks during the data transmission process.

2. The mobile target defense method according to claim 1, wherein The measurement coding enhanced moving target defense model is defined as: Among them, is the true measurement data in the power grid state estimation, including branch active power and node active injection power, is the reversible coding matrix in the measurement coding, is the change amount of the true measurement data caused by the power grid data injection attack, is the measured value tampered by the attacker in the power grid state estimation, When the measurement matrix in the power grid state estimation is the change amount of the true measurement value satisfies: Among them, is the change in the node voltage phase angle expected by the attacker, When the mobile target defense changes the impedance values of some branches, the measurement data under the mobile target defense is expressed as: Among them, is the measurement matrix corresponding to the impedance value of some branches changed by moving target defense, and the node voltage phase angle represents the state of the power grid system, and the measurement noise satisfies zero-mean Gaussian distribution, The steps of constructing a measurement coding enhanced moving target defense model for power grid data injection attacks include: In response to the moving target defense, changing the measurement matrix from to , the measurement-encoded enhanced moving target defense model is expressed as: Among them, and are the measurement matrices before and after changing the impedance values of some branches in mobile target defense, respectively.

3. The mobile target defense method according to claim 1, characterized in that When solely adopting the moving target defense strategy, the detectable conditions of the power grid data injection attack are expressed as: For a power grid where both the active power of branches and the injected active power of nodes are measured, the rank of the combined matrix of matrix and matrix satisfies Among them, and are sub - matrices composed of the rows corresponding to the branch active power measurements in matrices and matrix respectively. is the number of branches in the power grid. , and are sub - matrices composed of the rows corresponding to the node injection active power measurements in matrices and matrix respectively.

4. The mobile target defense method according to claim 3, wherein In the measurement coding enhanced moving target defense, assume that the rank of the current combined matrix satisfies: For the set of encoded measurements When using a coding factor that is neither 0 nor 1 to encode the th measurement the rank of the encoded combined matrix does not depend on the specific value of the coding factor Based on this, the design criterion is determined to enhance the detection ability of mobile target defense against the power grid data injection attack.

5. The mobile target defense method according to claim 4, wherein The measurement coding enhanced moving target defense is expressed as the following optimization problem: Among them, is the change amount of the branch impedance in moving target defense, and are the weight coefficients of the measurement coding and the cost related to moving target defense respectively. PLIS is the reactance sensitivity parameter, indicating the impact of reactance change on the power grid loss. is the measurement arrangement matrix, indicating the branch power flow and node injection power to be measured. is the incidence matrix determined by the power grid topology, characterizing the connection relationship between nodes. is the feasible region of the branch impedance change.

6. The mobile target defense method according to claim 5, wherein The steps of designing a heuristic solution algorithm to optimize the measurement coding and moving target defense strategies by iteratively coding a new measurement or changing the impedance of a new transmission line include: Let the currently encoded measurement set be , the encoding matrix be , and the measurement matrix after moving target defense changes the impedance of some branches be , respectively search for the cost corresponding to improving the rank of the combined matrix by newly encoding a measurement or newly changing the impedance of a certain branch; In the process of increasing the rank of the combined matrix by new coding measurements, a heuristic search algorithm is designed using the design criteria of the diagonal matrix, and a coding method for increasing the rank of the combined matrix at the lowest coding cost is obtained by trying measurements outside the set other than 0 and 1 and checking the rank of the new combined matrix. The process is expressed in the following form: Among them, indicates that the measurement of the new code can increase the rank of the combined matrix, indicates that the measurement of the new code cannot increase the rank of the combined matrix, is the measurement of the code required to increase the rank of the combined matrix at the minimum cost, is the increase in coding cost, is the new coding matrix; In the process of increasing the rank of the combined matrix by newly changing the impedance of a branch, obtain a method to increase the rank of the combined matrix with the minimum increase in power grid loss by trying to modify the impedance of the target branch to an arbitrary value different from the current value and checking the rank of the new combined matrix. The process is expressed in the following form: Among them, indicates that newly changing the impedance of a branch can increase the rank of the combined matrix, indicates that newly changing the impedance of a branch cannot increase the rank of the combined matrix, and l is the impedance of the branch that needs to be changed to increase the rank of the combined matrix at the minimum cost, is the corresponding minimum increment of power grid loss, is the change amount of the new branch impedance, is the new measurement matrix, is the set of branches whose impedances have not been changed yet; In response to and , when , the rank of the combined matrix is increased by using a measurement coding method, and relevant parameters are updated: , Otherwise, adopt the moving target defense method to increase the rank of the combined matrix and update the relevant parameters: In response to and only one of which is 1, increase the rank of the combined matrix by using the corresponding method with a value of 1, and update the relevant parameters; and If and , or the rank of the combined matrix reaches , terminate and output the encoded measurement set and the change in the branch impedance .

7. A mobile target defense system with enhanced measurement coding, characterized in that Including: A memory storing computer instructions thereon; And A processor connected to the memory and configured to execute the computer instructions to implement the measurement coding enhanced moving target defense method according to any one of claims 1 to 6.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that, When the computer instructions are executed by the processor, the measurement coding enhanced moving target defense method according to any one of claims 1 to 6 is implemented.

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