Application and Analysis of Distributed Database Technology in Electric Power Enterprises Liu Qiong, Lü Su, Li Lin (School of Electrical Engineering, Wuhan University, Wuhan, Hubei 430072) As an example, the application of distributed database technology in various systems of power companies Detailed analysis, and based on this proposed to build a distributed database of power systems.

1 The business departments of Yin Bai Power Company established relatively independent systems and realized mutual network communications. To obtain information sharing is an important symbol for the acceleration of the automation and informationization process in the current power system. This is also planned as a power sector. produce. The basis for decisions such as planning. The use of distributed object communication mechanism is a relatively advanced information management technology. It is based on the concept of layered components "brick and tile" 131. The combination of centralized database technology and computer network technology. Since the mid-1970s, this technology has developed rapidly. From the 1990s to the present, distributed databases have begun to enter the practical stage. The field of distributed databases is not only at the level of research and prototyping, but also at the level of industrial products and real-life applications.

2 Distributed Database (DDB) Technology 2.1 Concepts A so-called distributed database system divides a database into logically related subsets, stores them on computers in different locations, and provides data access capabilities to fully operate these subsets. Database system.

The data distribution is designed for the locality of processing, availability and reliability of distributed data, workload distribution, storage costs, and availability. Several specific indicators are: distribution transparency, distributed units, data replication, remote database access, remote process-to-process communication, and recovery of distributed transactions.

The design of a distributed database consists of four phases: the design of the global model, the design of the segment, the design of the location allocation, and the design of the physical structure of each site. The global mode and physical structure can be designed in the same way as the design concept mode and physical mode in the centralized database. Therefore, the uniqueness of distributed database design lies in segmented design and distribution design.

2.2 Based on the characteristics of distributed database systems Reliability Through redundant replication between nodes, the entire system can still guarantee data integrity when a single node is destroyed, and the reconstruction of nodes can be reliably implemented. By applying logic replication, after a single node is destroyed, its task can be smoothly taken over by other nodes until the node is restored. At the same time, since each child node is an autonomous system, the child node can still achieve most of the functions when the child node loses contact with the center node.

The distributed data distribution target of the distributed database is the optimization of node autonomy and cooperation. Through appropriate data redundancy replication, most applications can obtain data from the remote node, improve processing efficiency, and reduce network overhead.

The modern application system will inevitably face the problem of system expansion and adjustment during its operation. Since the distributed database system provides a consistent expansion interface and a dynamically scalable system architecture, the system can be smoothly upgraded and reconfigured. At the same time, the distributed database system also provides the load balancing function to achieve reasonable and full utilization of the system resources.

Distributed database systems provide data site independence. For applications, DDB shields the distribution of data and accesses all data in the same way. The operational support for heterogeneous databases is achieved by providing a unified data model and its API to applications.

Through GRID-based distributed computing technology, the entire system can distribute a large-scale computational application (such as the optimal analysis of the power grid) to each sub-node for processing, making full use of the processing capacity of the sub-node and significantly shortening it. calculating time.

Support and integration of data warehouse and data mining The distributed system architecture provides the foundation for building a large-scale data warehouse, and it provides further data mining, namely Online Application Process (OLAP) and Decision Support System (DSS). Simple and transparent development interface. These aspects can be easily integrated into an overall system.

On the basis of a distributed database, applications such as expert systems, geographic information systems, and virtual enterprise networks can be seamlessly integrated.

3 Application status of distributed database in power system 3.1 Particularity of power system automation technology The database application technology of power system has its special industrial characteristics: the real-time requirements of Supervisory Control And Data Acquisition System (SCADA) and The data availability problem of the traditional Management Information System (MIS) requires the improvement of its underlying database technology. At this point, the distributed database can complete the task of converting data into information and providing it to the power system management users in a timely manner to achieve decision support.

3.2 Grid dispatch automation system The grid dispatch automation system was founded in the 1960s and is a new computer-based power grid control technology. It has become the pillar to ensure the safety, stability, and economic operation of the power system and the foundation for its management modernization. After nearly 40 years of development, the grid dispatching automation system has evolved from the initial centralized SCADA to the distributed SCADA/EMS/DMS, and the Jingzhou Electric Power Bureau’s power grid has been used for the normal operation of the power grid, enhanced power management, and providing accident handling and decision-making basis. The updated mainframe system of grid dispatch automation is taken as an example to discuss its database construction.

Adaptive network interconnection of application subnets in enterprise networks. In this way, different nodes or heterogeneous networks of different applications in the same network can establish a relative client/server communication system by treating each other as an external logic application environment. That is, based on different applications, the application object communication process can be transparently customized, thereby realizing the openness. Tasks and network interconnections.

Based on the design requirements of the Power Grid Dispatch Automation System Technical Function Specification, MSSQLSever, a large commercial relational database management system, is used to store and manage system information and data in the database, and provides database access interfaces for various non-real-time information systems. In order to meet the system's requirements for openness and real-time database expansion, the following measures have been taken: introduction of hierarchy and object-oriented concepts, definition of data according to their respective characteristics and storage according to their types; classification of data in the same table and establishment of IDs for their identification , primary key and index.

Real-time database combined with commercial databases.

The backup of the real-time database is established in the commercial database, and the two are kept in sync. Using open database link (ODBC) and the developed universal "soft-bus" interface technology, historical and real-time data services are provided for each application.

The system's database service program uses a large commercial MSSQLServer, its functions include: create, modify the database, quickly access and manage data; define system parameters, plant stations and RTU data characteristics; online monitoring, modification, definition of data types and their structure, Expand the scale of the database; quickly copy, backup, failback, and automatically log in and restart the database; provide common database access and application program interfaces; support concurrent access to data, protect database security, consistency, and integrity.

It is not difficult to conclude from the above analysis that such a typical system structure adopts a distributed structure and a centralized database.

3.3 Power enterprise management information system The power enterprise information management system is a new database management system. Each business department's subsystem independent database is integrated with the customer's power enterprise network to build an architectural model, each database management system in addition to the management of the department's data In addition, the global shared data must be automatically uploaded to the core database, that is, data consolidation and aggregation.

Take Wuhan Power Supply Bureau as an example. The Wuhan Power Supply Bureau has jurisdiction over more than 700 square kilometers of transmission, transformation, distribution, and use of power facilities in the Wuhan area. It has jurisdiction over the Hankou, Hanyang, Wuchang, and Qingshan Branch Offices. Its purpose is to realize the processing of partitioned data in the four regions. Secure real-time data sharing. AM/FM (Automated Mapping/Facilities Management) is a computer graphics and text interactive system based on equipment and production technology management in geographic information, and it is also a computer application software system that combines graphic technology and database management technology. Due to the wide scope of its jurisdiction and the distribution of jurisdiction, it is determined that the Wuhan Power Supply Bureau AM/FMAGIS system must adopt a multi-level distribution structure: that is, the primary server is located in the municipal bureau, and the secondary server is located in each branch office; The secondary server can work independently from the primary server for each branch. Each server works in its own domain and implements cross-domain communication between the bureau and the bureau through the TCP/IP protocol. Each branch has its own graphics server and database server. It is not necessary to request a response from the remote server through the metropolitan area network of the power supply bureau, and the clients of each bureau only make input and modification requests to their respective servers. This will not only reduce the load of the metropolitan area network, but also reduce the burden on the servers for massive data processing.

In the actual construction of the system, the data distributed processing design idea is to install the SQL Server database server for the headquarters and the four branch offices separately, which constitutes a distributed database application system; the organization can query all the branch office data but cannot perform data maintenance. The system function is divided into two major modules: Each branch can and can only maintain the data of this branch. For each data table, create a conditional view in each branch office and generate a record set that belongs only to the local office; convert the maintenance of the local user data table to the maintenance of the view.

Each branch can query other offices' maintainable data in the local database (but cannot maintain it). Using the replication mechanism of SQL Server, a two-way replication mechanism is established between the branch office and the city office, and this replication mechanism is continuous (branch and branch offices). There is no replication relationship between them.) Create a database named WHPB on all five SQL Server servers. The data in each database is non-shared and shared. Shared data is maintained and consistent by the four regional offices in the WHPB database. The table that holds these data is the publication table. The specific implementation plan is: four branch offices have different and unique unit codes.

All published tables in the WWPB database have a primary key. The structure of the published table is the same on all servers. The information registered in the field data dictionary is also the same. The information in the table data dictionary is in addition to the "Publishing conditions."

The same applies to fields other than the field. The "Publishing Conditions" field describes the coding of the unit.

Create all publishing tables in the application data of the five distribution points, ensure that the "Publishing Conditions" field of all distribution points is set correctly, and then create a publication view in the application database of all distribution points.

Every time you modify the table structure you need to rebuild a single publication view.

After creating an ordinary user, you need to reassign the user right after modifying the structure of the table that the ordinary user can access or after reconfiguring the menu for the user.

Wuhan Power Supply Bureau Distributed AM/FMA) IS system has reached the expected technical specifications after nearly one year of trial operation. Inspect the process of automation of other power companies. This system is the first management information system based on the computer metropolitan area network and multi-level server distributed database technology in the domestic power system.

3.4 Development Recommendations Building a distributed database system in a power system requires the following considerations: (Conversion to page 153) / Fill in the schedule 插入 Insert, modify, and delete data in the database 狙 Insert the data above. Modify or delete data as long as the contents of the sqlstrirg modify the corresponding SQL statement.

5 Conclusion In the development process of Zhejiang Guoxuan Refrigeration Co., Ltd.'s air-conditioning design system, we used the method of accessing the database based on the ODBC API function, which not only ensured the integration with the AutoCAD environment, but also realized the database access function of the system using the ODBC API in the program. The function, on the one hand, will make the programming more difficult. On the other hand, because it is a direct call to the ODBC API function, it can improve the database access performance, but also has a higher flexibility. In practical applications, it can be used in conjunction with the interfaces and engines provided by the development tools, such as the CDatabase class in VC++, to improve performance and improve efficiency.

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