In recent years, blockchain technology has developed rapidly. It is known from the above-mentioned literature that it is widely used in various industries. In this paper, blockchain technology is introduced into the field of power transactions, and the value of blockchain is extended to a wide range of services ranging from pure data storage (such as device configuration and governance, sensor data storage and management, and multi-access payment) [27]. In the field of power recycling transactions, this paper studies new transaction models based on blockchain credit consensus, and builds a distributed information storage method based on digital encryption and verification technology to provide power users with non-tampering and traceability for historical credit data. At the same time, this paper designs the application of user credit query method based on alliance blockchain, and elaborates on application architecture, information storage, credit query logic and so on.Firstly, combining with the technical characteristics of blockchain, the storage and query mechanism of information on the chain is described. Finally, according to the user's information on the chain, the risk assessment and analysis are carried out to determine the risk level, so as to implement the corresponding electricity bill settlement method.
1. Consortium chain application architecture
Blockchain technology was proposed by Satoshi Nakamoto in 2008. After continuous iterative evolution, it has formed five major technical features: distributed, trustless, time stamping, asymmetric encryption and smart contracts. Compared with the operating space and efficiency of the private chain, the value of the alliance chain is greater. Compared with the uncontrollable and privacy security issues of the complete decentralization of the public chain, the alliance chain is more flexible and more maneuverable.According to the transaction characteristics of electricity companies, power supply companies and financial institutions, this paper abstracts the regulatory agencies such as companies and financial institutions as nodes on the alliance chain for research.
Blockchain data is timestamped, so it can be used as a reliable tool for data traceability of power and energy transactions. Based on blockchain technology, this paper establishes a distributed and decentralized credit data storage mechanism, and obtains the consensus of banks and financial institutions, government regulatory agencies, large power supply and sales companies, and power users, and forms a joint management by the three parties. The blockchain data architecture is mainly divided into six levels: data layer, network layer, consensus layer, incentive layer, contract layer, and application layer, which jointly complete transaction verification, judgment, storage, and backup [9].
2. Risk assessment of arrears based on alliance chain technology
Alliance chain is a relatively new way to apply blockchain to enterprises, which can be applied to collaborative services between various enterprises. In the alliance, a number of nodes are pre-designated for accounting, and the nodes that join later need to apply and verify, and join the alliance chain after approval. This paper introduces volunteer nodes [19] as the lower-level virtual members of power supply enterprise nodes in the blockchain to help power supply companies complete data analysis and risk assessment.
The form of alliance chain is used for the traceability and sharing of power consumption data information of power companies, which can ensure that all parties to the transaction share information with each other. At the same time, the non-fully decentralized structure guarantees the relative leadership of power supply companies, bank governments and other regulatory agencies in the entire organization, and the transaction speed of the alliance chain can also handle various transaction information data generated during the transaction process[20 ].
(1) Division and role of institutions on the alliance chain
In the entire alliance node, the institutions and functions are as follows:
①Power supply enterprise node
Containing institutions:a supply node that receives transaction requests and provides electricity and energy services.
Information data:The information provided includes power energy quality, stock quantity, energy production time, power plant location, energy transportation routes, power energy purchase and transportation price and other basic energy information.
②User Enterprise Node
Containing institutions:The demand-side unit composition of electric energy includes high-voltage non-resident users and low-voltage non-resident users.
Information data:The information provided includes basic information such as the number of electricity transactions, expected prices, and historical payment records.
③Bank financial node
Containing institutions:The composition of banking institutions undertaking corresponding financial transfer tasks.
Information data:The information provided includes basic information such as user company registered capital, financial loan status, other energy transaction status (such as water charges), historical electricity payment records, etc.
④Government regulator node
Containing institutions:Unit nodes responsible for power energy operations and trading tasks.
Information data:Provides energy policy updates and access to information about the energy trading process.
⑤Volunteer node
Containing institutions:The nodes included in the power supply company’s subordinates are used to calculate and evaluate the risk level of power users, and assist in completing calculations and transmitting information.
Information data:This node is a virtual node, which does not need a secret key. It is only used to receive the information transmitted by the power supply node, perform the corresponding calculation, and then pass the calculation result to the power supply node.
The energy and power information database is jointly maintained and operated by all nodes, and each node has equal rights to exchange and store information. At the same time, data is uploaded through consensus mechanism and P2P network diffusion, and a traceable and tamper-free block is formed by relying on hash algorithm and linked to form a block chain in turn.
(2) Blockchain information storage and sharing
According to the different participants in the transaction alliance chain, the alliance node in the blockchain can be divided into banking and financial node, power supply enterprise node, user node, government regulator, volunteer node and other auxiliary nodes. After each node is verified, it will get the corresponding ID IP of its own node.In order to protect the privacy of corporate information and data of power users, this paper adopts asymmetric encryption method, and the public key and private key of each node are generated by the elliptic curve algorithm. Public and private keys appear in pairs, which can not only protect the basic information privacy of electricity users, but also complete the storage and sharing of information and data. After the public and private keys are generated, they broadcast their own information and public keys to the entire network, and obtain and save information from other nodes to form an alliance transaction chain.
Analogous to the blockchain data storage and sharing scheme adopted by Kang in the field of vehicle interaction [21], in the power information sharing blockchain, the steps of generating and storing the user's original information in the blockchain are as follows:
1: Both parties of power supply and demand, as well as banks and governments, jointly form alliance nodes. The identity of enterprise nodes needs to be verified by government regulatory agencies.Each node uses elliptic curve algorithm and asymmetric cryptographic algorithm to obtain public key K and private key k as identity IP identification, and generates its own digital signature sig, and at the same time confirms the authority of each node;
2: Each node uses the DPOS consensus mechanism to vote for the authorized node, which is generally voted by all enterprises on the alliance chain. Each unit uploads its own information through the P2P network, which is packaged and uploaded to the block chain by the authorized node to store the original data of information;
3: When the user company needs to purchase energy, the node Xi sends the transaction request to the authorized node with the time stamp and digital signature sig, and the node verifies its identity and then feeds back Xi. After that the node Xi will send the transaction history information data of the most recent year (Such as: current default situation, historical payment information, corporate credit, etc.)to the authorized node with public key Ki , that is
Vi→AN:request (sig)
Message{data|Ki|sig|timestamp}
Block
4: The authorized node broadcasts the ciphertext information M to other ordinary nodes for review and verification.After confirming its authenticity, the information will be packaged and added to the block chain for permanent storage.
Credit information mainly includes two parts:
1. Normal performance (average monthly electricity consumption, frequency of electricity purchase, etc.)
2. Information on breach of contract (number of breaches, amount of breach, delay in payment of penalties, etc.)
Therefore, the encrypted information of historical data verified by users is stored in the alliance chain, which has the characteristics of non-tampering and traceability. In order to simplify the storage space, the recording adopts the method of data indexing. The other nodes of the blockchain can only store the hash value of the data.
After the authorized node verifies the information submitted by the user,it sends its transaction request to the power supply node Yj, Yj queries the user’s information data based the blockchain before the transaction, and the volunteer node calculates the risk level according to the index.(The credit index evaluation will be explained in detail in 3 Part).The corresponding electricity fee recovery method will be adopted. The P2P data sharing query steps are as follows:
1: The power supply node Yj sends the identity ip and digital signature to the authorized node when receiving the transaction request. After receiving the response, it queries the data block about Xi according to the information index in the blockchain, and sends a data access request to Xi including its own number signature
Yj → Xi request (sig|timestamp)
2: After receiving it, Xi verifies the identity of YJ according to the digital signature. The permission opening authorization is sent to the authorized node, and the private key of the queryer and the public key of the queryer Yj are attached for query.
Xi → AN message (authority|ki|Kj|timestamp)
3: Upon receiving the information, the authorized node has the right to open query to Yj .Yj queries Xi’s historical transaction and financial record raw data according to the bank node data pool and the information index in the blockchain, and sends it to volunteer nodes for data analysis after verification to determine the user’s credit rating (detailed in the next section), so that the corresponding electricity fee transaction measures can be implemented under the control of the government supervision node.
1. The architecture consists of user module, access control strategy module, data analysis module,and transaction module.
2. Electricity supply and use companies obtain their own public and private keys through key handling.
3. Electricity companies set access policies, power supply nodes verify their identities, and obtain permissions
4. If the identity of the power supply node matches the access control policy set by the power user, the encrypted shared data can be obtained through the blockchain and the bank data node, and the data will be sent back to the power supply company after being processed by the key center
5. The volunteer nodes subordinate to the power supply company judge the credit rating of the power supply company according to the data sent back. The power company then transacts power with customers through smart contracts under the supervision of government nodes and uploads it to the blockchain.
(4) Analysis of the alliance chain transaction and verification process
The power transaction alliance chain established in this article is developed around the historical information and data of user companies. It is a tool for the power supply company to verify transactions. Combined with the blockchain system, it can further increase the ability of tamper-proof, transparent transaction processing and privacy protection[27] .
Among them, the power transaction smart contract is formulated by the nodes in the alliance chain. The power supply company, the bank supervisory agency and the power user respectively make transaction guarantees. This commitment stipulates the rights and obligations of the parties to the transaction, and is generated after both parties' private keys are signed.
The contract is translated into the corresponding code, broadcast to the entire chain via the P2P network, and after verification by all parties, it is transmitted to the blockchain by the authorized node to form an energy transaction smart contract.During the execution of the smart contract, the status information always records the energy status of the power supply company. After the transaction is completed, the grid unit, bank and supervisory unit verify the transaction completion data information.After the verification is passed, the authorized node on the chain temporarily stores the information in the transaction database and disseminates it to the entire chain. After the entire chain is verified, the transaction information can be packaged on the chain (the process is similar to the second part: data storage on the chain ) to ensure the authenticity and traceability of transaction information.
Before the transaction, the electricity user first verifies the identity through the "registered account" of the alliance chain node.Relying on the alliance chain technology platform, the node initiates a transaction request in the blockchain, stamps a time stamp and digital signature, forms the transaction cipher text through the hash function and publishes it to the entire network. After receiving the transaction request, the authorized node determines the user's identity information and receives the original data uploaded by the user by checking the digital signature in the transaction request. At the same time, the power supply company packages its own identity and credit information and sends it to the corresponding authorized node, and broadcasts it to all chain.and with the help of authorized nodes, query the user's basic data, electricity bill information, historical payment records and other historical data and current financial conditions, and send them to the entire network for verification.
In the transaction process, both parties of the transaction trigger the power and energy transaction smart contract deployed on the chain by setting the transaction quantity, transaction price and other data.The specific terms of the transaction contract and the incentive reward sharing for authorized nodes are pre-set in the smart contract. After the smart contract is over, the transaction information is stamped with time stamp and the digital signature of both parties to the transaction is packaged into the block, and the entire transaction is declared complete .
Grid companies can make detailed explanations on the quality and inventory of electric energy and set prices on their own, and they have the right to change the pricing. Through the deployment of smart contracts, users can initiate transactions with power companies and pay a certain fee, which can achieve the purpose of as-used as needed. The grid company will immediately carry out energy transmission, which reduces the risk of energy users in arrears to a certain extent.
3. Information extraction and risk level assessment
This paper adopts the analytic hierarchy process model to analyze and score the indicators. This model is a mature forecasting method. First, the analysis method is used to construct the indicator system, and then the indicator weight is calculated through the expert scoring system, thereby establishing an evaluation model for power customers in arrears. [24]
1. Use analytical methods to build an index system
Table 1. Index table
Total target layer
|
Sub-goal layer
|
Criterion layer
|
Credit
Evaluation
Rating
Model
|
Business ability
|
Business structure
|
Scale efficiency
|
Equipment level
|
technical skills
|
Management ability
|
Management quality
|
Net asset profit margin
|
Roe
|
Financial strength
|
Net sales profit margin
|
Assets and liabilities
|
sales growth rate
|
Integrity record
|
Number of breaches
|
Default amount
|
Credit repayment history
|
Electricity contribution rate
|
2. Calculate the weights through the pairwise comparison matrix indicators
The matrix form is
The matrix satisfies the conditions:
According to the ratio scale of the judgment matrix, the experts score to determine the mutual importance of different indicators, and the survey opinion form will be statistically analyzed
(Among them: Mij is the arithmetic square root of the importance score of the i-th index and the j-th index, sij is the sum of the scores, and n represents the number of experts)
After completing this judgment matrix, perform a random consistency test and calculate the weights
The random consistency test formula is:
In the analytic hierarchy process, it is generally believed that when CR<0.1, the judgment matrix has acceptable consistency; when the CR is smaller, the judgment matrix is close to complete consistency, otherwise, the degree of deviation is greater.
RI is a random consistency index, this paper directly borrows from Xu Shubo's RI value of the first 1-8 steps obtained by repeating the RI of 1-15 steps:
N steps
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
RI
|
0
|
0
|
0.52
|
0.89
|
1.12
|
1.26
|
1.36
|
1.41
|
After the expert opinions are collected, the score matrices of the sub-target layer and each criterion layer are constructed through statistical analysis. Then, the consistency test is carried out, and the weight value is calculated after the consistency test. The weight value is the proportion in the evaluation system.The calculation method is as follows:
At the same time, the eig function in MATLAB was used to calculate the value of the matrix, and then the consistency test was carried out. This time, a total of 30 questionnaires and 30 valid questionnaires were issued.
Through investigation and statistics, this paper obtains the weight distribution of the total target and sub-targets
Table2. Total target level index weight table
According to the table 2 , the CR value of the total target and the sub-target is 0.068, and the result is less than 0.1, which passes the consistency test.
According to the table 3-6 , the CR value of the total target and the sub-target is 0.068, and the result is less than 0.1, which passes the consistency test.
Through statistical analysis of the questionnaire, the weight distribution of the following sub-target items and various criteria is obtained.
Table 3.Weight Table of Business Ability Index
Table 4.Management Ability Index Weight Table
Table 5.Financial Strength Index Weight Table
Table 6.Integrity record index weight table
From the above table, It can be knowed that the above CR values have passed the consistency test, and then summarize the above matrix to obtain the weight table of each indicator of the credit evaluation model
Table 7.Credit Evaluation Model Index Weight Table
Target layer
|
Weights
|
Criterion layer
|
Weights
|
Business ability
|
0.103
|
Business structure
|
0.103
|
Scale efficiency
|
0.347
|
Equipment level
|
0.222
|
technical skills
|
0.328
|
Management ability
|
0.110
|
Management quality
|
0.141
|
Net asset profit margin
|
0.309
|
Roe
|
0.550
|
Financial strength
|
0.250
|
Net sales profit margin
|
0.228
|
Assets and liabilities
|
0.569
|
sales growth rate
|
0.202
|
Integrity record
|
0.537
|
Number of breaches
|
0.104
|
Default amount
|
0.137
|
Credit repayment history
|
0.271
|
Electricity contribution rate
|
0.487
|
After determining the final weight, it is to assign the score of each index, define each index, define and score the index according to the percentage system after determining the scoring principle
Table 8.Credit Evaluation Model Index Assignment Table
|
Reference value
|
Limit value
|
Full score
|
Grading
|
Business structure
|
|
|
1
|
1 point for the complete and complex business structure of the enterprise, 0 point otherwise
|
Scale efficiency
|
|
|
4
|
Score 0-4 points according to enterprise scale and production efficiency
|
Equipment level
|
|
|
2
|
2 points for more advanced equipment
1 point for holding
0 points for basically no equipment
|
technical skills
|
|
|
3
|
Divided into 0-3 points according to the advanced level of the company's technological capabilities
|
Management quality
|
|
|
2
|
Rich management experience, 2 points for significant performance, 1 point otherwise
|
Net asset profit margin
|
≥5%
|
<1%
|
3
|
Actual value/reference value*full score
|
Roe
|
≥12%
|
<1.5%
|
6
|
Actual value/reference value*full score
|
Net sales profit margin
|
≥8%
|
<1%
|
6
|
Actual value/reference value*full score
|
Assets and liabilities
|
≤50%
|
>80%
|
15
|
[1-(Actual value-reference value)/(reference value-limit value)]*Full score
|
sales growth rate
|
≥10%
|
<3%
|
5
|
Actual value/reference value*full score
|
Number of breaches
|
|
|
6
|
The number of defaults is 0, 6 points are awarded
5 points for 1-2 times
4 points for 3-4 times
And so on until the deduction is over
|
Default amount
|
|
|
7
|
3 points deducted for the monthly default amount greater than 50,000 yuan, until the deduction is complete
|
Credit repayment history
|
|
|
14
|
3 points will be deducted for each outstanding interest over 5 days until the deduction is complete
|
Electricity contribution rate
|
≤50
|
>70
|
26
|
[1-(Actual value-reference value)/(reference value-limit value)]*Full score
|
Divide the scoring results into five levels
Points
|
grade
|
81-100
|
A
|
61-80
|
B
|
41-60
|
C
|
21-40
|
D
|
0-20
|
E
|
- Excellent and trustworthy A-level users are regarded as the preferred users of the power supply company. The power company shall provide preferential services in terms of electricity charge policies, power dispatching, equipment calibration and other aspects, and may also reward them based on power consumption;
- Class B and C are generally trustworthy users with good credit awareness, good financial status and few times of arrears. Electric power companies should actively cooperate with them, give appropriate preferential policies, pay attention to their operation level and strive to cultivate high-quality customers;
- Electric power users of grade D and E are listed as trust-breaking users of the power supply company. Such users have a high risk of arrears and are not suitable for subsequent development and training. Power supply companies should carry out certain constraints on management, when necessary, to take a special policy of charge recovery of pay first and then use electricity, and cautiously sign electricity purchase contracts.
In this section, based on the principles of system, science, and stratification, the arrears of electricity users are divided into three levels , and then different electricity charge management strategies are formulated for the three levels of customers. While actively maintaining users with good risk levels, targeted measures should be taken to recover electricity charges for users with poor risk levels, so as to avoid operational risks of electric power enterprises, and improve the risk prevention ability of electricity charges recovery in time.