1 Introduction The emergence of control networks has led to profound changes in the structure of traditional control systems. The rapid development of information technology has enabled control systems to gradually evolve into fully distributed network-integrated control systems, namely fieldbus control systems (FCS). PROFIBUS-DP bus technology is a new technology in FCS, and applying PROFIBUS-DP bus technology to power electronics products is in line with this new trend. This paper introduces the implementation and application of solid-state soft starters for medium and high voltage motors in the PROFIBUS-DP bus. The medium and high voltage solid-state soft starter is developed into an intelligent slave station in the PROFIBUS-DP bus, completely solving the problem of traditional medium and high voltage solid-state soft starters controlling medium and high voltage motors independently, where information cannot be fed back to the host computer, thus forming an "information island." 2 Introduction to PROFIBUS-DP Technology PROFIBUS-DP is an important part of the PROFIBUS (FMS, DP, PA) three-part system. The PROFIBUS protocol is based on the ISO/OSI network reference model. PROFIBUS-DP does not have layers 3 to 7; the Direct Data Link Map (DDLM) provides a layer 2 functional map for the user interface. The physical layer (layer 1) uses EIARS-485 twisted pair or optical fiber, and the connector uses a 9-pin D-type socket specified according to the RS 485 standard [1]. The data link layer (layer 2) provides media access control functions, data integrity checks and the protocol for transmission execution is called FDL, which adopts a hybrid media access protocol, corresponding to DIN(E)19245, and supports single master or multi-master systems, master or slave devices. In PROFIBUS-DP, the token ring method is used between master stations and the master-slave method is used between slave stations. The token method of the master station allows the station that obtains the token to obtain bus control within a pre-defined time period [2]. Data exchange between the master station and the slave station is required to be as fast as possible and can communicate with the slave station when it has bus control. Each master station can send and retrieve information from the slave station. This configuration provides the shortest bus cycle, the system has good openness, third-party systems can also connect to the PROFIBUS-DP fieldbus, modular expansion is possible, it can be adapted to the scale and requirements of various production equipment, and ensures high flexibility. The comprehensive diagnostic function of PROFIBUS-DP can quickly locate faults. The fault of the slave station on the bus does not affect the data communication of other stations. During operation, I/O stations and other field devices can be activated or deactivated. The medium and high voltage solid-state soft starter in this article is an intelligent slave station in the PROFIBUS-DP bus. 3 Introduction to medium and high voltage soft starter In the medium and high voltage motor solid-state soft starter [3], the weak current part uses DSP as the control chip, microcontroller as the management chip, and SPC3 as the communication chip; the high voltage part consists of several sets of series/parallel thyristors, vacuum contactors, voltage transformers and current transformers. The PWM trigger pulse generated in the DSP is transmitted through the optical fiber to the energy storage tube and short-circuit transformer to trigger the thyristor on the high voltage side pulse transformer; in order to ensure the voltage division balance of multiple sets (a pair of anti-parallel thyristors in series) of thyristors in each phase, each set of thyristors is connected in parallel with a set of dynamic and static equalizing plates. When the soft starter starts, the controller DSP activates the vacuum contactor, controlling the conduction angle of the thyristor to gradually increase the voltage to the motor at a certain slope for smooth starting. When the rated speed is reached, full voltage is applied, the bypass vacuum contactor activates, and then the thyristor trigger signal is turned off to stop thyristor power supply. The motor starting is complete. Afterward, the soft starter continues to monitor the motor's operating status and provides various fault protections. It is primarily suitable for the control and protection of starting, running, and stopping squirrel-cage asynchronous medium- and high-voltage motors. Its loads mainly include fans, centrifugal pumps, air compressors, belt conveyors, crushers, and mixers. The start, run, and stop of the soft starter can all be controlled and displayed by a host computer via the PROFIBUS-DP bus. In the PROFIBUS-DP bus, the medium- and high-voltage solid-state soft starter participates in the system configuration as an intelligent slave station. 4 System Hardware Configuration The QB-H series high-voltage soft starter organically connects the thyristor, DSP, and PROFI-BUS-DP bus. Its control system block diagram is shown in Figure 1[3]. [IMG=Control System Block Diagram]/uploadpic/THESIS/2007/12/20071218132430152545.jpg[/IMG] The hardware structure block diagram of the DP head of the high-voltage soft starter developed using SPC3 and P89C52 is shown in Figure 2. [IMG=DP Head Hardware Structure Block Diagram]/uploadpic/THESIS/2007/12/2007121813243789324T.jpg[/IMG] Specific Analysis: P89C52 communicates with the TMS320F2407 chip for control and display signals through the UART port, and at the same time communicates with the P0 port of the SPC3 chip and reads and writes the DG-2064 display module. The SPC3 chip uses Intel mode and synchronous mode. Because it has an internal address decoding circuit, an external address latch is not needed. SPC3's AB0-AB4 pins are connected to the P2 port of the P89C52, with AB4 connected to P2.7 to avoid conflict with the P89C52's internal RAM. P89C52's P1.6 and P1.7 pins are used for chip selection of the SPC3 and DG2064. A 7705 chip is used as a watchdog timer to prevent program crashes. The SPC3 forms a PROFIBUS-DP header via optocouplers and an RS485 bus. 5. System Software Design Since the PROFIBUS-DP communication protocol is handled by the SPC3 chip, the system program mainly includes the SPC3 initialization program, interrupt program, status display program, and DSP communication program. The SPC3 initialization program mainly includes [4]: ​​setting the SPC3 allowed interrupts, slave address identification number, mode register, diagnostic buffer, parameter buffer, configuration buffer, address buffer, PRM message, CFG message, SSA message, initial data length, initial user data length, setting input and output buffer pointers, diagnostic buffer pointers, CFG buffer pointers, PRM buffer pointers, etc. All programs communicating with SPC3 are implemented using interrupts, which is more practical for systems with high real-time communication requirements. 6 Application Analysis In the development of the DP head of the medium and high voltage soft starter, in terms of hardware design, due to the large number of control quantities, fast calculation speed, and strong real-time performance, TMS320F2407 is used as the control chip, P89C52 microcontroller is used as the management chip, and SPC3 is used as the PROFIBUS-DP protocol conversion chip. The dual CPU (DSP, P89C52) is used to separate control and management, which improves the stability and reliability of the system. In terms of software design, considering the high real-time requirements of system communication, all programs related to SPC3 communication are implemented using interrupts. At the Changsha Auto Technology Development Center, a PLC was used as the master station, a PC (using WinCC monitoring software) as the monitoring machine, and a solid-state soft starter for medium- and high-voltage motors as the slave station. The motor model was an increased-safety brushless excitation synchronous motor (6000V, 445.5A, 4000kW capacity, 300r/min), and the exciter (181V, 192A, 60kVA capacity, 300r/min). The waveform of the motor current during the soft start (no-load) process of the medium- and high-voltage motor was obtained through the PROFIBUS-DP bus on the WinCC monitoring interface, as shown in Figure 3. [IMG=Waveform of motor current]/uploadpic/THESIS/2007/12/2007121916551615129M.jpg[/IMG]