Abstract : This paper introduces the application of SINAMICS S120 frequency converter in vector control on Anfeng 150T converter, discusses basic issues including system configuration, network planning, and control ideas, and briefly introduces the advantages of Siemens Starter software for visual debugging.
Keywords: frequency converter, converter, vector control, visualization, debugging, VC Starter
SINAMICS S120 converter in Converter drive Research and Application
Liu Zheng
(Shandong Steel Group laigang automated department
(laiwu Shandong 271104)
Abstract: This paper introduces the SINAMICS S120 converter with vector control mode in AnFeng of 150T converter application, discussed includes system configuration, network planning, as well as the control of such basic questions, and a simple introduction of the Siemens Starter software visualization debugging advantages.
Keyword: Converter Vector Control VC Visualization and debugging Starter
1. Introduction
The construction and commissioning of the No. 2 150-ton converter steelmaking project at the No. 3 steelmaking plant of Qinhuangdao Anfeng Iron and Steel Co., Ltd. was undertaken by Laiwu Steel Electronics Co., Ltd., and was successfully put into operation on September 1, 2011.
All frequency converters used in this project are from the Siemens SINAMICS series. In particular, the converter tilting mechanism utilizes the SINAMICS CSS120 frequency converter with active feedback, a multi-axis drive system integrating V/F control, vector control, and servo control, featuring a modular design. The modules are interconnected via the high-speed drive communication interface drive-cliq, enabling rapid data exchange and meeting the process requirements for electrical drive equipment.
2. Communication method between S120 and PLC
This project uses a Siemens S7-400 series PLC system, extended with ET200M via ProfibusDP, and communicates with the SINAMICSS120 frequency converter via ProfibusDP to control the converter's start and stop and monitor its operating status. During converter commissioning, accessories such as CP5512, CP5513, or CP5613 can be used for direct communication with the host computer. The CU320-2 selected in this project has a LAN port, allowing direct connection to the frequency converter via network cable. The basic configuration of the project is shown in Figure 1.
3. Characteristics of the S120 frequency converter
The S120 frequency converter was chosen as the control device for the converter tilting mechanism due to both its excellent performance and the characteristics of the converter process. According to the converter's process requirements, the furnace body needs to be able to tilt ±360°. Normally, the converter operates in a balanced torque state, meaning the weight of the furnace body is concentrated in the lower part, where the molten steel is located. This ensures that the furnace body can achieve self-reset in the event of an accident. The tilting mechanism can balance the inertial potential energy load. Under normal production conditions, when the converter tilts to several fixed positions (iron charging position, blowing position, tapping position, etc.), the converter is required to be stationary. The transition from stationary to moving and from moving to stationary must be smooth, without significant impact. Therefore, the controlled object has certain dynamic and static performance requirements.
The core control unit CU320 (V2.2 version) of the SINAMICS S120 can control 4 vector axes or 6 servo axes. The S120 boasts excellent vector control capabilities. Vector control involves measuring and controlling the stator current vector of an asynchronous motor, and based on the principle of field orientation, controlling the excitation current and torque current of the asynchronous motor separately, thereby controlling the motor torque. Specifically, the stator current vector of the motor is decomposed into excitation current and torque current through a 3/2 coordinate transformation, and controlled separately. The amplitude and phase between the two components are also controlled simultaneously, i.e., controlling the stator current vector; hence, this control method is called vector control. Simply put, vector control decouples flux linkage and torque, designing separate adjustment mechanisms for each to achieve high-performance speed regulation of the motor. Using vector control, a three-phase asynchronous motor can be controlled as an equivalent DC motor, thus achieving the same static and dynamic performance as a DC speed control system. The figure shows the principle diagram of vector control, where ω is the actual speed value, ω* is the speed command value, and ψrd is the stator-rotor flux linkage conversion value. ψ rd * represents the estimated value of stator and rotor flux linkage; isq represents the stator and rotor current conversion value, and isq * is the corresponding calculated value.
4. Visual debugging process
The S120 offers a rich variety of control methods and modes, providing strong support for meeting various process requirements of converter tilting. The S120 provides three control methods: torque control, speed control, and position control. It also offers three control modes: servo control, vector control, and V/F control. In this project, we selected the vector control mode (P0107). We configured the four frequency converters in the tilting system as master-slave control units, with the master unit using speed loop control and the slave units using torque loop control. In an empty furnace, the master-slave control of the four frequency converters driving four motors performed well. Then, we added counterweights in batches while simultaneously adjusting the frequency converter parameters. We used DP communication to read the actual torque and speed of the frequency converters into the PLC, which then generated the brake signal based on the readings. Because converter tilting is a heavy-duty operation, and the magnitude and direction of the actual torque are constantly changing during tilting, it was necessary to repeatedly adjust the frequency converter's PI parameters, ramp time, and brake parameters. Initially, with a large counterweight, the furnace body experienced significant shaking during operation. After several attempts, we added a variable proportional adjustment to the frequency converter parameters, which ultimately solved the problem of furnace body shaking and enabled the converter tilting system to achieve the expected results.
During commissioning, we used Starter software to configure the S120 parameters. Starter software is an important component of the Siemens SCOUT platform, enabling seamless integration with Step7 via DriveES, allowing the integration of drive equipment into the automation system. Commissioning the SINAMICS S120 inverter using Starter allows for quick and convenient communication by directly connecting a PC to the LAN port of the CU320-2 using a network cable and the TCP/IP protocol. After setting the DP address in Starter, the DP DIP switch position is automatically displayed. Furthermore, communication messages must use the same settings for a proper connection. The "Transfer to HWconfig" function allows direct transfer of the message settings configured in Starter to the PLC configuration. Utilizing the graphical interface of Starter, inverter parameters can be modified online, and the commissioning effect and inverter operating status can be observed at any time, greatly facilitating our commissioning work, significantly shortening commissioning time, and effectively ensuring the project's progress.
5. Summary of Actual Results
The SINAMICS S120 frequency converter was used in a converter steelmaking project. Commissioning was conducted using a combination of the Starter commissioning tool and a PLC, shortening the project construction cycle and improving commissioning results. Because the SINAMICS S120 employs a combination of ALM and AIM, it can automatically adjust the DC bus voltage, effectively preventing downtime caused by excessive DC bus voltage. Furthermore, the combination of ALM and AIM includes energy feedback, significantly reducing the converter's braking time. This results in energy savings and improved utilization of the tilting mechanism, achieving significant economic benefits and demonstrating clear advantages over traditional frequency converters.
References:
- Siemens Automation Drives Group Customer Support Department "Drive Unit Commissioning Starter" 2009
- SINAMICS S120 Debugging Manual 2010
- SINAMICS S120 Specification Manual 2010
- Feng Duosheng, ed., *Principles and Practice of Sensorless Vector Control*, Machinery Industry Press, 2001.
About the author: Liu Zheng (1983-10), male, from Jinan, Shandong Province, graduated from Dezhou University in 2007 with a major in Computer Science and Applications. He is currently an assistant engineer in the Automation Department of Laiwu Steel, specializing in automation control.
Contact information: 15863405530, [email protected]
Mailing Address: Room 507, Building 19, Beizhaoyuan, Gangcheng District, Laiwu City, Shandong Province
