Application of OPC Technology in Monitoring System of Wind Farm

At present, there are about 40 companies engaged in the development and development of wind turbines in China. The wind turbines and monitoring systems in large-scale wind farms are generally provided by multiple manufacturers. The monitoring systems of each manufacturer are incompatible with each other and different types of wind farms. The unified monitoring and management of wind turbines lacks effective research and it is difficult to conduct unified maintenance and management. In view of the coexistence of many wind turbine control systems and power monitoring systems in wind farms, OPC technology was introduced to achieve a seamless connection between the wind turbine control system and the electrical control system in the wind farm, which solved the problem of multi-system interconnection of wind farms.

1. The key technology of OPC OPC (OLE for Process Control) is the application of object linking and embedding technology in process control, and provides a unified standard for the development of industrial automation software. The purpose of OPC technology is to provide a unified transmission standard for communication between a large number of data sources in a field device or database, making system integration more convenient. OPC technology is also a technology that Microsoft has jointly launched with the control community in order to apply Windows to control systems. It is based on Microsoft's Component Object Model/Distributed Component Object Model (COM/DCOM) technology, which defines a set of standard objects, interfaces, and attributes for industrial control software. Through these object interfaces, applications are implemented. The standardization of data exchange greatly improves the openness and interoperability between automation devices.

A. COM and DCOM technology With the rapid development of software technology, traditional program upgrades can no longer meet the needs of technological development. The solution to this problem is to divide the application into small applications or components, and then assemble these components at runtime. Get up and form an application. There are two major standards in the component specification, one of which is the Component Object Model (COM) technology introduced by Microsoft. This technology provides frameworks and technical specifications for the various software components working together in a standard mode. This specification can be used to ensure that some of the binary and network standards that can be interoperable, the client, and the component follow. Communication in an operating environment, even using components developed in different development languages, can be achieved. COM is an effective way to exchange data between software components.

The most important part of the COM specification of the COM interface, the core content of the COM specification is the definition of the interface, and COM is in the form of an interface. Components interact with components and components and client programs interact through interfaces. The interface member function will be responsible for providing services to other components. For COM, the interface is a memory structure that contains an array of function pointers. For the client, a component is a set of interfaces, and any component with the same interface can have transparent replacement of the component with respect to other components.

B. The emergence of COM technology based on OPC client/server data exchange model provides a technical basis for the simplification of data exchange between control devices and control management systems. However, if different standardized COM interfaces are not provided, the interconnection between COM components of various control equipment manufacturers is still not possible.

With the popularization and popularization of control components based on the OPC standard, it not only makes the addition and subtraction of the control system functions and the replacement of components simpler, but also makes it easier to access the process data. For example, a process control program that conforms to the OPC specification can be directly connected to a data analysis software package or a spreadsheet application.

2. OPC data acquisition system design In traditional data acquisition systems, applications such as supervisory control and data acquisition systems (SCADA), human-machine interfaces (HMI), and configuration software communicate with the field devices via drivers, but the drivers Has its own limitations, such as the same device to adapt to different client applications need to develop different drivers, causing labor to repeat. Once the hardware device is upgraded, the previously developed driver should also be modified accordingly. Drivers generally take the form of dynamic link libraries (DLLs). Dynamic data exchange (DDE) is the main method of data exchange, but this method does not allow multiple applications to access a device at the same time.

A. Wind farm front-end data acquisition system design Because OPC defines a set of interface access methods based on Microsoft OLE/COM or DCOM, applications that conform to or support OPC protocols can exchange with each other via the OPC protocol as long as they can access each other based on the TCP/IP protocol. data. To install multiple network cards on the wind farm front interface machine, it is necessary to connect with the engineer station of the monitoring system provided by the fan manufacturer. The IP address is set to be in the same network segment as the engineer.

Due to the current openness of each fan manufacturer, Denmark's Vestas fan has developed an OPC interface for access by third-party manufacturers. The Spanish Gemesa fan is provided with its database interface software (DLL), Dongqi, and Huarui. Such domestically produced fans are polled with the fan controller, forwarded to the MODBUS communication protocol, provided to a third party, and completed by a third party.

B. Wind farm OPCSever interface software design This paper takes Huarui fan 1500 as an example to introduce the wind farm OPCSever interface software design.

Huarui Fan is a MODBUS data communication server software that provides communication with the fan controller. The software implements real-time data exchange with the on-site fan. We design the MODBUS/TCP package as OPC Sever. When using the MODBUS/TCP protocol specification, a connection-oriented method is adopted. During communication, three steps are required to establish a connection, transmit data, and release a connection.

a. MODBUS/TCP message parsing (1) The first seven bits of a MODBUS/TCP request message are the MBAP headers, which are the transaction handler identifier high (1 bit), the transaction handler identifier low (1 bit), and the protocol identifier (2 Bit), length identifier (2 bits), unit identifier (1 bit). The last seven bits are MODBUS request messages, 03 is the function code, which is the contents of the read holding register, 0001 is the starting address, 0078 is the number of registers, 1631 is the check code, and the check method is the CRC cyclic redundancy check.

(2) MODBUS/TCP receive message F30103F0000040E0...

Starting from the tenth bit, a single floating point float is used. Each two packets is a register response data, with the high byte first and the low byte second.

b. The realization of OPCSever data access The main function of the OPC data access server is to complete the number of accesses. There are four data access methods for OPCSever: synchronous data access, asynchronous data access, refresh access, and subscription method access. In this design scheme, access is performed using a subscription method, and the accessed data actively notifies the client program to refresh the data when the status changes.

Message parsing The Sockect communication module performs read and write operations with the MODBUS/TCP server and parses the received message.

The OPC interface module is mainly used to define, connect, add, and delete OPCSever, OPCGroup, and OPCItem. It defines the subscription method for data access, and the OPC Foundation provides standard interface functions for customers to access in a uniform manner.

The program management module is mainly the on-site data monitoring, the management of measurement point information and the item information received from the OPC interface module, including the time stamp and data quality.

3. Conclusion This article first introduced the key technologies of OPC - COM and DCOM technologies, and then described the client/server data exchange model based on OPC technology. Finally, the application of OPC technology in wind farm monitoring system was described in detail - OPC Data acquisition system design. The OPC technology application and the wind farm monitoring system fundamentally solve the communication problems between different types of fan equipment, making the wind farm cluster management more convenient. In addition, the wind power enterprise's production information management platform was improved and the level of informatization was improved.