Which companies in China currently offer relatively good fully digital systems for caustic soda rectification units?

Fully digital control systems are now highly mature; we have been using them for several years now, and the results are excellent. As for the manufacturers, it’s not easy for them to say so; this essentially serves as free advertising for those manufacturers on the forum.

I currently have Corey, Sifang, Xi’an, and Zuzheng – I’m not sure which one is stronger. It doesn’t really matter if we just discuss it casually. I have one more question: nowadays, aren’t all microcontroller flip-flops digital flip-flops? It was Corey who made a mistake just now. Last edited by mu99899 on 2008-1-23 11:04.]

Personally, I think Sifang is okay; I have worked with Sifang and Xi’an Zhenzheng, but not with NARI. NARI’s microcomputer-based protection systems are excellent, but I’m not sure how good their rectification control systems are. The digital regulation trigger controller consists of an RICS-5 type control board and a power transformer. The RICS-5 type control board is mainly composed of a DC regulated power supply, current feedback buffer amplification and analog-to-digital conversion circuits, digital input/output interfaces, communication interfaces, synchronization circuits, dual CPU control chips, pulse power amplifiers, and other circuits. 】This is information from all four parties.

Kuzushin has gone bankrupt and no longer exists; Shihou and Kori both originated from the original Kuzushin

Introduction to the HPRC-6 Rectification Control System Preface: To meet the requirements of the technological advancements in modern power electronic equipment as well as those in industrial production processes, our company has drawn on past experience with rectification control systems used in industrial settings. Taking into account both the advancement and maturity of such control systems, and while ensuring high reliability of the system, we have successfully developed the HPRC-6 rectification control system based on PLCs (Programmable Logic Controllers) and DSPs (High-Performance Digital Processors). This system can meet the technical performance requirements of control systems for rectifier equipment in industries such as electrochemistry, metal smelting, and metal electrolysis, and it can adapt well to the process requirements of these industries. The system overview is as follows: 11.1 System design: The system consists of a PLC unit and master/slave controller units. The PLC unit is connected to the master/slave controller units via communication, allowing for real-time monitoring of their operational status. In the event of a failure of the main controller, the PLC unit takes over the functions associated with the slave controller. The control system panel diagram and system control diagram are as follows: 11.2 PLC Unit: PLC units generally use well-known international brands (such as SEIMENS, AB, Mitsubishi, etc.). The PLC serves as the monitoring and management unit of the control system, and it features industrial control bus communication interfaces that allow it to communicate with devices such as touch screens, industrial control computers, and human-machine interfaces, thereby enabling remote and intelligent device management. The PLC unit can collect the real-time operating parameters of auxiliary equipment (such as rectifier transformers, coolers, DC isolators, DC current sensors, etc.), and utilize software within the PLC to implement functions such as interlocking and protection that are required by electrical regulations and process specifications. The PLC also exchanges information through communication interfaces and touch screens, allowing for real-time monitoring and control of the operation of on-site equipment via the touch screen. Control buses generally employ the internationally standardized PROFIBUS or MODBUS field bus technologies. A field bus is a serial, digital, multi-point communication data bus that connects field devices/instruments located in the production area with the automatic control devices/systems situated in the control room. The main advantages of fieldbus technology are as follows: 11.2.1 Enhanced capability for information integration at the field level. Fieldbuses can obtain a large amount of valuable information from field devices, thereby better meeting the requirements for information integration in factory automation and CIMS systems. Fieldbus is a digital communication network that not only replaces 4-20mA signals but also enables the transmission of device status, fault, and parameter information. In addition to remote control, the system can also perform remote parameterization. 11.2.2 Openness, interoperability, interchangeability, and integrability: As long as products from different manufacturers use the same bus standard, they are interoperable and interchangeable; therefore, the devices have good integrability. The system is open, allowing other manufacturers to integrate their specialized control technologies, such as control algorithms, process flows, and formulas, into the general system. As a result, there will be many monitoring systems tailored to specific industry requirements in practical applications. 11.2.3 High system reliability and good maintainability: The automation monitoring system based on field buses uses bus connections instead of one-to-one I/O wiring, which reduces the factors of unreliability caused by wiring points in large-scale I/O systems. At the same time, the system features online fault diagnosis, alarm, and recording functions for field-level devices; it enables remote parameter setting and modification of these devices, thereby enhancing the system’s maintainability. 11.2.4 Reduced system and engineering costs For distributed systems with large-scale I/O operations, it eliminates the need for numerous cables, I/O modules, and related cable installation work, thereby reducing the system and engineering costs. 11.3 Master and slave controller units: 11.3.1 Controller structure The controller is a standard 3U electromagnetic chassis that can be flexibly equipped with various plug-ins, making it suitable for both 6-pulse rectification systems and 12-pulse rectification systems. Fiber transmission boards can also be used as needed by the system. The following system is the control structure of a 12-pulse rectifier system. The master and slave controller units feature dual-machine hot backup, with all input signals fed into both sets of controllers. In normal operation, the main controller is active while the slave controller is in standby mode (with its output signals blocked) ； When the PLC unit detects that the main controller is in a faulty state, it will issue an unlock signal from the controller within 100 ms, simultaneously shutting down the operation of the main controller. The layout diagram of the controller chassis is as follows: Front view of the controller, Top view of the controller, Rear view of the controller. 11.3.2 Hardware design of the control system: All components of the system use standard 3U size and are placed in a standard 3U×84R electromagnetic compatibility chassis to cope with the harsh electromagnetic environment in the field. The functions of the main plug-ins in the chassis are described as follows: There are three power supply plug-ins, one of which provides the 5V and ±15V powers required by the CPU ； A +24 V power supply that provides the isolation required for digital signals ； A power supply that provides +48V and +15V required for pulse power amplification modules. Digital IO plugin: A DI type that can use an internal +24V power supply, and is a plugin for receiving external passive digital switch signals ； An external power supply can also be used to receive active digital signals. The number of input points is 5; they are used to collect information such as the on/off status of the device, faulty nodes, as well as remote and local control signals, which is then sent to the CPU board for processing. The DO points are 3 in number, with AC relay output, and can be used for fault alarm, tripping, or other output functions. The voltage analog input module is used to detect the zero crossing of external AC voltage, and converts it into a level signal that is used by the CPU board as a synchronization signal for generating pulses. The current analog input module is used to acquire external current signals and send them to the CPU for processing. The high-level analog input board plug-in can be used to acquire 0-10V, 0-5V, or 4-20mA voltage and current signals, which are then sent to the CPU for processing. It is often used as an input board for feedback signals. The CPU plugin uses TI’s 32-bit digital signal processor (DSP, TMS320F2812) as the main CPU, and a CPLD (EPM1270T144) as the auxiliary control chip; together they carry out functions such as address decoding, phase-locked loop operation, pulse train generation, signal acquisition and processing, as well as protection interface handling. The pulse power amplification module amplifies the six pulse signals sent by the CPU module, thereby generating 6 trigger pulse signals. The various plugins are connected to each other through a backplane. The back panel can be flexibly configured according to the requirements of the system plugins. The system is equipped with a voltage-to-frequency conversion board: it features 3 high-speed fiber optic inputs, and in systems with high voltage or where fiber optic isolation is required, the VFC320 chip is used to convert direct current and voltage signals into frequency signals for transmission to the CPU board for processing. 11.3.3 Control system software design: The software that runs on the CPU of the control system is entirely written in the C language, which ensures good portability. The main workflow is shown in the figure below: Figure 5: Main control flow diagram. First, the central control system sends the required load curve to the power supply system controller via communication. Upon receiving the start command, the system controller activates the rectification device. At the same time, the output current is sampled, and PI control is performed based on the command curve and the feedback current. The adjusted command determines the load condition based on the voltage sampling results and current sampling results. If the load fails, it will stop working ； If the load is operating normally, a trigger signal is generated based on the PI regulation result to adjust the input voltage, thereby achieving the goal of regulating the output DC current. 11.3.4 Human-machine interaction interface and communication (optional): The control system is equipped with a simple human-machine interface; input is carried out via 12 membrane keys, of which 6 are primary keys and 6 are secondary keys. In the event that any of the primary keys are damaged, it is possible to use the 6 secondary keys to carry out all functions through appropriate settings. The output is displayed on a green LCD screen with a 240×128 pixel resolution, which can show data such as the output voltage, current, and waveforms set from the upper-level system. In the event of a system failure, the LCD screen can clearly indicate the cause of the failure and the location of the problem. Since this system operates in an environment with significant electromagnetic interference, fiber optic communication can be used for communication between this control system and the higher-level control system. The baud rate can be freely selected between 9600 and 1M. 12 Main technical features of the system: 12.1 The digital processor uses a 32-bit DSP chip, which is among the fastest chips of its kind in the domestic industry. 12.2 Functions such as steady-state closed-loop control, trigger pulse generation, and system protection are all implemented by the DSP chip. 12.3 The controller chassis uses specially imported electromagnetic shielding chassis from Germany, capable of withstanding harsh field conditions. The synchronization signal processing uses a bandpass filter to acquire the signal, and phase locking is performed via a DSP, thereby improving the anti-interference performance of the synchronization signal. 13 The above characteristics are reflected in: a) System availability: The system’s design takes into account various factors within the overall engineering environment, ensuring that it can be put into use immediately after installation and commissioning and operate stably and reliably, with an annual availability rate of over 99.9%. b) System maintainability: The system’s hardware and software components are easy to maintain, with each part having the capability for self-checking and online diagnostic verification. The software comes with backups, which facilitates installation and startup by engineers. The application is easy to expand, and the database provides interfaces for user programs as well as database data that enables further development, allowing users to incorporate their own programs into the system for execution. c) System reliability: The system exhibits high reliability when operating in engineering sites, with an average time between failures MTBF of ≥50,000 hours. d) System fault tolerance: The software and hardware devices possess good fault tolerance; errors in the communication between various software and hardware functions and the data acquisition and processing system, as well as common mistakes made by operators or engineers during operations, do not disrupt the normal operation of the system. The system has the capability to recover from failures caused by unexpected situations. e) System safety: Under normal conditions, the operation of hardware and software devices does not pose a threat to the safe and stable operation of the rectifier substation nor to the safety of the staff.

In the caustic soda industry in China, the main players include Jiujiang, Laitai, Zhuzhou **Rectifier Research Institute, Xi’an, etc., among which Jiujiang has the highest performance in terms of production volume

I’m sorry to ask, but what is this thing used for? Where is it used? Those who sell frequency converters should know how to sell them, right?

This is the control system for the rectifier cabinet; it has nothing to do with frequency conversion!