Abstract : A modular design method was adopted to design and implement an intelligent frequency converter with a PROFIBUS-DP communication interface. The frequency converter uses a DSP chip (TMS320/40) as the control core of the frequency conversion section, and also as the microprocessor for the PROFIBUS-DP interface. The frequency converter uses a dedicated communication interface chip SPC3 to form an intelligent slave station in the PROFIBUS-DP bus, and the intelligent PID control algorithm is discussed. Finally, the PROFIBUS-DP intelligent slave station was applied to an AC speed control system, achieving good control results. Keywords : Frequency converter; PROFIBUS-DP interface; DSP; SPC3; Intelligent PID 0 Introduction In recent years, with the progress and development of power electronics technology, computer technology, and power electronic semiconductor devices, variable frequency speed control technology has developed significantly. Variable frequency drives (VFDs) have been widely used in industrial control fields due to their advantages such as high speed control accuracy, fast response speed, comprehensive protection functions, strong overload capacity, significant energy saving, and convenient use and maintenance. Fieldbus adapts to the trend of industrial control systems towards decentralization, networking, and intelligence, and has become a global hot topic in industrial automation technology since its inception. With the advent of fieldbus, traditional analog instruments will gradually give way to intelligent digital instruments, equipped with PROFIBUS-DP digital communication capabilities. A number of transmitter controllers integrating detection, calculation, control, and communication functions have emerged, along with actuators with control modules and fault information displays, significantly changing existing equipment maintenance and management methods. PROFIBUS fieldbus is the world's most widely used fieldbus technology and has been listed as an IEC 61158 international standard. Therefore, developing frequency converters with PROFIBUS-DP interfaces has significant practical implications. [b][align=center]For details, please click: Implementation of Intelligent PID Frequency Converter Based on PROFIBUS-DP Interface[/align][/b]