Privacy-preserving distributed economic dispatching method for isolated microgrids based on encryption strategy

Abstract

The present invention discloses a privacy-protected distributed economic dispatching method for an isolated microgrid based on an encryption strategy, and constructs a confidentiality interaction protocol and a privacy protection consistency algorithm for ciphertext interaction between microgrid generator sets, which belongs to the field of microgrid economic dispatching. Each generator set in the microgrid of the present invention obtains the weighted difference between its own information and the information of other generator sets adjacent to it in the communication network through a confidentiality interaction protocol, thereby updating the privacy protection consistency algorithm, and optimizing the total power generation cost under the premise of satisfying the power balance of the power system. In addition, the present invention realizes the ciphertext transmission of information between each generator set on the basis of ensuring the effective completion of the economic dispatching task, avoids privacy leakage, and ensures the safe and stable operation of the power system.

Description

Technical Field

[0001] The present invention belongs to the field of microgrid economic dispatch, and in particular, relates to an isolated microgrid privacy protection distributed economic dispatch method based on encryption strategy. Background Art

[0002] Microgrids are considered to be an effective solution for integrating multiple distributed energy sources, which can improve the resilience, scalability and efficiency of traditional power systems. For power systems, a microgrid is a single controllable entity with multiple loads and multiple power sources, operating in grid-connected mode or isolated mode. Isolated microgrids are often used to supply power in remote areas with power shortages, which requires the system to operate stably under various operating uncertainties. The economic dispatch problem is one of the basic problems of energy management. Its goal is to meet the power demand at the lowest operating cost while meeting the constraints of the system and distributed generators. In the past, many centralized methods had high implementation costs and required a control center to collect the status and parameters of all generators and process a large amount of data, which was prone to single point failures. In addition, for future power grids with variable communication networks, the effectiveness of centralized methods may be weakened. Distributed methods have the advantages of robustness, flexibility and scalability, and are more suitable for solving economic dispatch problems.

[0003] The implementation of existing consensus-based distributed economic dispatch algorithms requires that adjacent units exchange information in plain text through a communication network. This directional transmission inevitably leads to privacy leakage, which in turn increases the security risk of the microgrid. Malicious attackers and eavesdroppers can infer the variables in the generation cost function by eavesdropping on sensitive information. Once these variables are disclosed, malicious adversaries can design attacks to increase the power generation cost of the microgrid or even destroy the grid system. Attackers can also infer consumers' behavior and habits through their electricity consumption information and sensitivity to electricity prices, and predict their future activities. In addition, the leakage of energy consumption data may also increase the risk of malicious adversaries stealing energy.

[0004] As mentioned earlier, in the future power system environment, many internal and external malicious adversaries will attempt to reveal privacy and launch attacks, which poses severe challenges to the power grid system. The transmission of plaintext information will lead to privacy leakage and increase security risks, and may lead to the failure of the entire economic dispatch, seriously affecting the stability and security of the power system. There is currently a lack of effective solutions to such problems. Summary of the invention

[0005] In response to the above-mentioned problems, the present invention provides an isolated microgrid privacy protection distributed economic dispatching method based on encryption strategy, which optimizes the total power generation cost under the premise of satisfying the power supply and demand balance of the microgrid, and realizes the ciphertext transmission between each generator set on the basis of ensuring the effective completion of the economic dispatching task, avoids privacy leakage, and ensures the safe and stable operation of the power system.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A privacy-preserving distributed economic dispatch method for an isolated microgrid based on an encryption strategy is provided for an isolated microgrid with an undirected connected communication network topology between generator sets. The method comprises the following steps:

[0008] Step 1: Set parameters and initialization, including the number of buses N in the microgrid and the load P of each bus Di 、Generator power generation cost coefficient α i , β i , γ i , the upper and lower bounds of the generator output power P imin and P imax , and the convergence parameter λ stop , P Mstop , ΔP stop , initialize the incremental cost λ of each generator set at time k = 0 i (0), where k is the number of iterations, i represents the i-th bus, i = 1, 2, ..., N;

[0009] Step 2: Each generator interacts with its neighboring generators according to a confidential interaction protocol to obtain the weighted difference in incremental cost. And update the incremental cost λ according to the privacy-preserving consensus algorithm i (k+1), then update k=k+1;

[0010] Step 3: Determine the convergence condition of the incremental cost, and go to step 4 if it is satisfied, and go to step 2 if it is not satisfied;

[0011] Step 4: Each generator set sets an initial value of average power mismatch;

[0012] Step 5: Each generator interacts with its neighboring generators according to the confidential interaction protocol to obtain the weighted difference of the average power mismatch information. And update the average power mismatch P according to the privacy-preserving consistency algorithm Mi (k+1), then update k=k+1;

[0013] Step 6: Determine the convergence condition of the average power mismatch, and go to step 7 if it is satisfied, and go to step 5 if it is not satisfied;

[0014] Step 7: The total power calculated by each generator set does not match;

[0015] Step 8: Determine the convergence condition of total power mismatch, end the program when it is met, and update the incremental cost λ when it is not met i (k+1) and update k=k+1, then go to step 4.

[0016] The confidentiality interaction protocol is based on the Paillier cryptographic system, the basic functions and characteristics of which are:

[0017] 1) Generate a key: Select two large prime numbers p and q of the same bit length, then calculate n = pq and u = (p-1)(q-1), v = u -1 modn; where n is the public key and (u, v) is the private key;

[0018] 2) Encryption: A number r is randomly selected from the ciphertext m, and the operation of encrypting the ciphertext c is c = E(m) = (n+1) m r n modn 2 , where m∈Z n , Z n ={z|z∈Z, 0≤z<n}, gcd means greatest common divisor;

[0019] 3) Decryption: The operation of decrypting ciphertext c into plaintext m is m = D(c) = L(c u modn 2 )vmodn, where

[0020] Additive homomorphism property: For ciphertext E(m1), E(m2), E(m) and plaintext a, E(m1+m2)=E(m1)·E(m2) and E(am)=E(m) d

[0021] When there is a communication link between two generators for information exchange, the two generators are called neighbors of each other. Assume that the state of generator i is x i , the state of its adjacent generator set j is x j ;

[0022] Furthermore, the confidentiality interaction protocol described in step 2 and step 5 is specifically as follows: for adjacent generator sets i and j, the specific interaction steps at time k are as follows:

[0023] Step a: Generators i and j generate key pairs (k pi(k), k si (k)) and (k pj (k), k sj (k));

[0024] Step b: Generator i uses public key k pi (k) Encrypt the negative state value, i.e. E i (-x i (k)), generator j uses public key k pj (k) Encrypt the negative state value, i.e. E j (-x j (k));

[0025] Step c: Generator i sends its public key k pi (k) and the ciphertext E i (-x i (k)) to generator j and receives the public key k of generator j pj (k) and the ciphertext E j (-x j (k));

[0026] Step d: Generator i uses the public key k of generator j pj (k) Encrypted state value, i.e. E j (x i (k)), generator j uses the public key k of generator i pi (k) Encrypted state value, i.e. E i (x j (k));

[0027] Step e: Generator set i is within the allowable range Random Selection Using the additive homomorphic property of the Paillier cryptosystem, we first calculate E j (x i (k)-x j (k)) = E j (x i (k))E j (-x j (k)), and then calculate The encrypted result is sent to generator set j; if generator set j is within the allowable range Random Selection Then calculate And send the ciphertext result to generator group i;

[0028] Step f: Generator i uses its private key k si (k) Decryption, i.e.

[0029] Step g: Generator i uses plain text Multiply Get the weighted difference

[0030] Step h: According to step fg, generator set j obtains the weighted difference

[0031] Then, in step 2, we refer to λ i , and obtain the weighted difference in incremental cost In step 5, refer to P Mi , and obtain the weighted difference of the average power mismatch information

[0032] Furthermore, the privacy protection consistency algorithm in step 2 is:

[0033]

[0034] The privacy-preserving consensus algorithm in step 5 is:

[0035]

[0036] Among them, Select the allowable range satisfy ε>0, N i is the number of neighboring generators communicating with generator i.

[0037] Furthermore, the specific operation of setting the initial value of the average power mismatch in step 4 is:

[0038] P Mi (k) = ΔP i (k)

[0039] ΔP i (k) is the power mismatch of the ith bus at time k, which is calculated as follows:

[0040] ΔP i (k) = P i (k)-P Di -P Li (k)

[0041] Where P i (k) is the output power of generator set i at time k, which is calculated as follows:

[0042]

[0043] is the transmission loss of the i-th bus at time k.

[0044] Furthermore, the specific operation of calculating the total power mismatch in the generator set i in step 7 is:

[0045] Furthermore, the convergence conditions in step 3, step 6, and step 8 are respectively:

[0046] |λ i (k)-λ i (k-1)|<λ stop ;

[0047] |P Mi (k)-P Mi (k-1)|<P Mstop ;

[0048]

[0049] Further, in step 8, the incremental cost λ of generator set i is updated i The specific operation of (k+1) is:

[0050]

[0051] Where κ>0.

[0052] The technical solution of the present invention can produce the following technical effects:

[0053] 1. The privacy-protected distributed economic dispatching method for isolated microgrids based on encryption strategy of the present invention optimizes the total power generation cost while meeting the power balance requirement of the power system; at the same time, on the basis of ensuring the effective completion of the dispatching task, the incremental cost information and power mismatch information of each generator set in the system are communicated with its adjacent generator sets according to the prescribed confidentiality interaction protocol, which can effectively protect the privacy of each node and ensure the safety and stable operation of the isolated microgrid;

[0054] 2. The execution of the privacy-preserving consistency update algorithm based on the confidentiality interaction protocol of the present invention only requires ciphertext interaction between generators, and finally the weighted difference of the updated consistency algorithm can be obtained, which can effectively resist honest and curious opponents in the communication network and eavesdroppers who eavesdrop on the communication link. The overall design method is based on a distributed control architecture, has the characteristics of strong scalability and high robustness, and is suitable for the future smart grid environment with a large number of distributed power sources connected. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A topological diagram of a communication network between the generator sets of the present invention;

[0056] Figure 2 is a graph of incremental cost changes for each generator set of the present invention;

[0057] Figure 3 It is the output power and transmission loss variation diagram of the present invention;

[0058] Figure 4 is a weighted difference graph of ciphertext received by the confidential interaction between generators of the present invention;

[0059] Figure 5 It is a flow chart of the privacy-preserving distributed economic dispatching method of an isolated microgrid based on encryption strategy of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present application and the corresponding drawings. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0061] This embodiment takes an isolated island microgrid system consisting of five generator sets as an example, and its communication network topology is as follows: Figure 1 The specific implementation steps are as shown in Figure 2 As shown:

[0062] 1) Set system parameters

[0063] Given an isolated microgrid system with N=5 buses, each bus has a group of generators and a load; the power requirements of each bus are P D1 =50, P D2 =150, P D3 =50, P D4 =150, P D5 =100; the convergence parameters are set to λ stop =P Mstop =0.001, ΔP stop =0.1, the initial values ​​of incremental cost are set to λ1(0)=80, λ2(0)=45, λ3(0)=70, λ4(0)=65, λ5(0)=55;

[0064] At the same time, the cost function of the i-th generator set is:

[0065]

[0066] Among them, P i is the output power of the ith generator set, parameter αi , β i , γ i As shown in Table 1;

[0067] Table 1 Generator power generation cost coefficient α in the isolated island microgrid system of this embodiment i , β i , γ i

[0068]

[0069] 2) Each generator interacts with its neighboring generators according to a confidential interaction protocol to obtain the weighted difference in incremental cost. And update the incremental cost λ according to the following privacy-preserving consensus algorithm i (k+1):

[0070]

[0071] And update k = k + 1; where ε = 0.2, The length of the key generated by the node in the confidentiality interaction protocol is set to 512 bits. i→j The upper and lower limits of the randomly selected allowable range are set to a =0.6,

[0072] 3) Determine the convergence condition of the incremental cost. For all generator sets i, |λ i (k)-λ i (k-1)|<λ stop If satisfied, go to step 4), if not satisfied, go to the above step 2).

[0073] 4) Set the initial value of the average power mismatch iteration: P Mi (k) = ΔP i (k), where ΔP i (k) = P i (k)-P Di -P Li (k) is the power mismatch of the ith bus at time k, P i (k) is the output power of generator set i at time k, which is calculated as follows:

[0074]

[0075] is the transmission loss of the i-th bus at time k.

[0076] 5) Each generator set interacts with the adjacent generator set according to the confidential interaction protocol to obtain the weighted difference of power mismatch information And update the average power mismatch P according to the following privacy-preserving consistency algorithm Mi (k+1):

[0077]

[0078] And update k = k + 1. Where ε = 0.2, The length of the key generated by the node in the confidentiality interaction protocol is set to 512 bits. i→j The upper and lower limits of the randomly selected allowable range are set to a =0.6,

[0079] 6) Determine the convergence condition of average power mismatch. For all generator sets i, |P Mi (k)-P Mi (k-1)|<P Mstop If satisfied, go to step 7), if not satisfied, go to the above step 5);

[0080] 7) The total power calculated by each generator set does not match

[0081] 8) Determine the convergence condition of total power mismatch. For all generator sets i, If it is satisfied, the program ends; if it is not satisfied, the incremental cost is updated And update k=k+1 and then go to the above step 4); where κ>0, κ=0.01.

[0082] like Figure 3-5 This is a simulation result diagram of an embodiment of the distributed economic dispatch of an isolated microgrid with privacy protection based on an encryption strategy of the present invention:

[0083] Figure 2 The figure shows the changes in the incremental costs of the five generating units. It can be seen that the incremental costs of all generating units tend to be consistent, which meets the requirements of economic dispatch to optimize the power generation cost.

[0084] Figure 3 It shows the changes in the output power and transmission loss of the five generator sets. The output power eventually tends to the sum of the microgrid system demand power and the transmission loss, achieving a balance between supply and demand.

[0085] Figure 4 It reflects the encrypted weighted difference of the interaction between generator sets. There is a big gap between the encrypted information and the real information, and the adversary without the corresponding private key cannot reveal the privacy by parsing the ciphertext. This shows that the method of the present invention can effectively protect the privacy of the generator set, avoid potential privacy leakage, and ensure the safe and stable operation of the power system.

[0086] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A privacy-preserving distributed economic dispatching method for isolated microgrids based on encryption strategy, characterized in that: The steps include: Step 1: Set parameters and initialization, including the number of buses N in the microgrid and the load P of each bus Di 、Generator power generation cost coefficient α i , β i , γ i , the upper and lower bounds of the generator output power P imin and P imax , and the convergence parameter λ stop , P Mstop , ΔP stop , initialize the incremental cost λ of each generator set at time k = 0 i (0), where k is the number of iterations, i represents the i-th bus, i = 1, 2, ..., N; Step 2: Each generator interacts with its neighboring generators according to a confidential interaction protocol to obtain the weighted difference in incremental cost. And update the incremental cost λ according to the privacy-preserving consensus algorithm i (k+1), then update k=k+1; Step 3: Determine the convergence condition of the incremental cost, and go to step 4 if it is satisfied, and go to step 2 if it is not satisfied; Step 4: Each generator set sets an initial value of average power mismatch; The specific operation of setting the initial value of the average power mismatch is: P Mi (k)=ΔP i (k); ΔP i (k) is the power mismatch of the ith bus at time k, which is calculated as follows: ΔP i (k)=P i (k)-P Di -P Li (k); Where P i (k) is the output power of generator set i at time k, which is calculated as follows: P Li (k) = B i P i 2 (k) is the transmission loss of the ith bus at time k; Step 5: Each generator interacts with its neighboring generators according to the confidential interaction protocol to obtain the weighted difference of the average power mismatch information. And update the average power mismatch P according to the privacy-preserving consistency algorithm Mi (k+1), then update k=k+1; Step 6: Determine the convergence condition of the average power mismatch, and go to step 7 if it is satisfied, and go to step 5 if it is not satisfied; Step 7: The total power calculated by each generator set does not match; The specific operation of calculating the total power mismatch in generator set i is: Step 8: Determine the convergence condition of total power mismatch, end the program when it is met, and update the incremental cost λ when it is not met i (k+1) and update k=k+1, then go to step 4; The convergence conditions are: |l i (k)-l i (k-1)|<λ stop ; |P Mi (k)-P Mi (k-1)|<P Mstop ; 2. The privacy-preserving distributed economic dispatching method for isolated microgrids based on encryption strategy according to claim 1 is characterized in that: The confidentiality interaction protocol is specifically: When there is a communication link between two generators for information exchange, the two generators are called neighbors of each other. Assume that the state of generator i is x i , the state of its adjacent generator set j is x j ,For adjacent generator groups i and j, the specific interaction steps at time k are as follows: Step a: Generators i and j generate key pairs (k pi (k), k si (k)) and (k pj (k), k sj (k)); Step b: Generator i uses public key k pi (k) Encrypt the negative state value, i.e. E i (-x i (k)), generator j uses public key k pj (k) Encrypt the negative state value, i.e. E j (-x j (k)); Step c: Generator i sends its public key k pi (k) and the ciphertext E i (-x i (k)) to generator j and receives the public key k of generator j pj (k) and the ciphertext E j (-x j (k)); Step d: Generator i uses the public key k of generator j pj (k) Encrypted state value, i.e. E j (x i (k)), generator j uses the public key k of generator i pi (k) Encrypted state value, i.e. E i (x j (k)); Step e: Generator set i is within the allowable range Random Selection Using the additive homomorphic property of the Paillier cryptographic system, first calculate E j (x i (k)-x j (k)) = E j (x i (k))E j (-x j (k)), and then calculate And send the ciphertext result to generator group j; Generator set j is within the allowable range Random Selection Then calculate And send the ciphertext result to generator group i; Step f: Generator i uses its private key k si (k) Decryption, i.e. Step g: Generator i uses plain text Multiply Get the weighted difference Step h: According to step fg, generator set j obtains the weighted difference In step 2, refer to λ i , and obtain the weighted difference in incremental cost In step 5, refer to P Mi , and obtain the weighted difference of the average power mismatch information 3. The privacy-preserving distributed economic dispatching method for isolated microgrids based on encryption strategy according to claim 2 is characterized in that: The privacy-preserving consensus algorithm in step 2 is: The privacy-preserving consensus algorithm in step 5 is: Among them, Select the allowable range satisfy ε>0, N i is the number of neighboring generators communicating with generator i.

4. The privacy-preserving distributed economic dispatching method for isolated microgrids based on encryption strategy according to claim 1 is characterized in that: Step 8: Update the incremental cost λ of generator i i The specific operation of (k+1) is: Where κ>0.

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