| With the rapid development of microelectronics technology, embedded system has penetrated into every corner of our life. It has the advantages such as good real-time, strong specificity, high reliability and performance-to-price, etc. Soft PLC technology, is to use software to realize the basic functions of standard traditional PLC (hard PLC). Soft PLC provides the same function of hard PLC, but also has various advantages of PC/MCU, and it has been widely applied in all kinds of control fields. Embedded soft PLC as a combinative product of soft PLC and embedded system, not only inherits the soft PLC's functions, also incorporates the advantages of embedded system. It has open architecture, stronger real-time and data processing capabilities, and will have more space for development in the area of industrial control.Relay protection system usually adopts microcomputer relay protection device. It is a digital relay protection with more flexibility and better protection performance. But it is the high cost and poor anti-interference ability. Its protection software adopts the assembly and high-level language to program, and doesn't have uniform standard, has a long development cycle, goes against the technical personnel's master and maintenance.Based on the above analysis, this paper has designed an embedded soft PLC that is dedicated to the power system relay protection (short title EEPLC). It has the simple, understandable logic programming language and powerful logic control ability, also can compensate for the shortage about that the relay protection technical personnel cannot skilled grasp assemble language and the lack of microcomputer device on logic control. EEPLC system is made up by development system and operation system.Development system runs on the PC platform, which includes three parts of editor, compiler and debugger. The editor has a friendly interface, supports customers to use the LD, FBD and ST three standardized language programming. The compiler converts application program by user writing into object code for the virtual machine identification and processing. Virtual machine system runs on the embedded platform that operating system isμC/OS-II and processor is S3C2410. It consists of interpreter, task scheduling module, the power system-specific program library and communication interface and other components. The interpreter is responsible for explanation and implementation of the object code, and is the core part of the virtual machine. The power system-specific program library is used to store various algorithms of the relay protection which is prewritten, and form module for direct call when the system needs.In the first part of this paper has studied the building of the embedded system hardware platform and the customization process ofμC/OS-II after introducing the relay protection and EEPLC system. The latter part has expounded the implementation process of the EEPLC development system and operation system. In the development system, it has decided to use ladder diagram as the research object of this paper through studying the three standardized programming language, and has introduced the design process of the ladder editor. In the virtual machine, the main design is the realization of interpreter, has given part of the main code, and also introduced the process that added algorithm module to the special program library of power system.Through examples validating of the operation system, proved to the correctness and the feasibility of the running system. |
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