High reliability is the first requirement of the process control system. Redundancy technology is a technology often used in computer system reliability design, and it is one of the most effective methods to improve computer system reliability. In order to achieve the unification of high reliability and low failure rate, we usually adopt redundancy technology in the design and application of the control system. A reasonable redundant design will greatly improve the reliability of the system, but at the same time it will increase the complexity of the system and the difficulty of the design. The application of the redundant configuration system also increases the user's investment. 1. Redundant technology The purpose of the redundant design of the control system: the system operation is not affected by local failures, and the maintenance of the faulty components has no effect on the realization of the function of the entire system, and online maintenance can be realized, so that the faulty components can be repaired in time. Redundant design will increase the difficulty of system design, redundant configuration will increase the investment of the user system, but this investment in exchange for the reliability of the system, it increases the mean time between failures (MTBF) of the entire user system, and shortens the average Fault repair time (MTTR), therefore, redundancy is necessary for control systems used in important occasions. Compared with a single component, a parallel system composed of two components (redundant for each other) has a mean time between failures of 1.5 times. The availability index of the system can be simply described by two parameters, one is the mean time between failures (MTBF) and the other is the mean time to repair (MTBR). The availability of the system can be expressed by the following formula: System availability = MTBF/(MTBF+MTBR) When the availability reaches 99.999%, the system will stop service for only 6 minutes per year. 2. The key technology of control system redundancy Redundancy is an advanced reliability design technology. 1:1 thermal redundancy is also called dualization. It is one of the effective redundancy methods, but it is not a simple parallel operation of two components, but requires Hardware, software, communication, etc. work together to achieve. The two components that are redundant to each other form an organic whole, which usually includes the following technical points: 1) Information synchronization technology It is the prerequisite for the realization of bumpless switching technology between working and spare parts. Only by implementing high-speed and effective information synchronization according to the real-time control requirements and ensuring that the working and spare parts work in unison, can the redundant parts be realized. Bumpless switching. In the hot standby mode, one of them is in working state (work card) to realize the system's data collection, calculation, control output, network communication and other functions; while the other is in standby state (standby card), it tracks the work card in real time Internal control state (ie state synchronization). The positive/negative logic between the working/standby cards is mutually exclusive, that is, one is the working card, and the other must be the standby card; and there are redundant control circuits (also known as working/standby control circuits) and information between them The communication circuit can coordinate the two cards to operate simultaneously and in an orderly manner to ensure the identity of the external input and output characteristics, that is, for the user's use, it can be considered as only one component. Generally, in the design, high-speed redundant communication channels (serial or parallel) are used between working and standby components to achieve mutual inspection of operating status and synchronization of control status (such as configuration information, output valve positions, control parameters, etc.). 2) Fault detection technology In order to ensure that the redundant part of the system is put into work in time when a fault occurs, a highly accurate online fault detection technology must be available to realize fault discovery, fault location, fault isolation and fault alarm. Fault detection includes power supply, microprocessor, data communication link, data bus and I/O status, etc. The fault diagnosis includes fault self-diagnosis and fault mutual inspection (mutual inspection between working and spare cards) 3) Fault arbitration technology and switching technology After the fault is found accurately and in time, it is necessary to determine the location of the fault in time, analyze the severity of the fault, and rely on the redundant control circuit mentioned above to analyze, compare and arbitrate the working and standby fault states to determine whether work is needed. Status switch between/standby. The switching of control rights to redundant spare parts must also be fast, safe, and disturbance-free. When a component in the working state fails (power failure, reset, software failure, hardware failure, etc.) or the failure of the working component is more serious than the backup component, the backup component must quickly and undisturbed take over all the control tasks of the working component. Control does not cause any impact. At the same time, it is required that the switching time should be milliseconds or even microseconds, so that the failure of the component will not cause the external control object to lose control or detect information failure, etc. In addition, it is also necessary to give an alarm via network communication or local LED display as soon as possible to notify users of faulty components and fault conditions for timely maintenance. 4) Hot swap technology In order to ensure the high reliability of the fault-tolerant system, the mean time to repair MTBR of the system must be minimized. To achieve this, efforts should be made to improve the independence, repairability, and fault maintainability of the unit in design. Realizing the online maintenance and replacement of faulty components is also an important part of the redundancy technology, and it is the key to realizing the rapid repair technology of the faulty components of the control system. The hot-swappable function of components can add or replace components without interrupting the normal control function of the system, so that the system can run smoothly. 5) In the redundant design of fault isolation technology, it is necessary to consider that the faults between the working and standby components should be as non-influencing as possible or the probability of impact is quite small (0.01%), that is, the fault is considered to be isolated. This can ensure that when a component in the standby state fails, the normal operation of the redundant working component or other associated components will not be affected, and the effectiveness of the redundancy is guaranteed. 3. Analysis of the application of redundancy technology in the control system Through the detailed analysis of control system redundancy principles and methods, it can be seen that the availability of the system depends to a large extent on those components that have a low MTBF value and can have a significant impact on the normal operation of the system, such as the main control card, network, and power supply. , Communication forwarding card, etc. Redundant design of key components in the system design can greatly improve the availability of the system. According to the different functional positioning of each component in the control system, the specific methods are different. The specific strategies are as follows: 1) Redundancy of the main control card The main control card is the core control unit of the whole system, which completes the control tasks of the system. The various design points of redundancy technology are fully applied here. The software and hardware of the two main control cards that are redundant to each other are completely the same. They execute the same system software and application programs. Under the control of the working/standby redundant logic circuit, one of them is running in the working state (working card), and the other One is running in standby state (standby card). There is a common redundant logic control circuit and a dedicated high-speed peer-to-peer redundant communication channel between the working card and the standby card. At the same time, information interaction or fault diagnosis can be performed through the I/O bus and the process control network. The mutually redundant main control cards can access the I/O and process control network. The main control card in standby mode executes the diagnostic program, monitors the status of the work card, queries the data memory in the work card periodically, and accepts the work card Real-time control operation information sent. The standby processor can save the latest control data at any time to ensure the disturbance-free switching of work/standby, but the main control card in the work mode plays a decisive role in control, output, and real-time process information release (with the right to speak). The key of redundancy technology is to achieve information synchronization, and the ultimate goal of information synchronization is to achieve disturbance-free switching between redundant components. We divide the information synchronization method into "natural synchronization" and "forced synchronization". The two main control cards that are redundant to each other exchange information (network communication, I/O communication) with the outside world as a whole, and share the input information that enters the whole. This is the identity of the redundant components (also called singularity). ). When outputting information to the outside world, the work card holds the initiative and speaks on behalf of the whole, that is, redundant coordination. In layman's terms, two mutually redundant components can be regarded as a whole for users and external control objects. In order to ensure that the two redundant cards have equal access to external information (I/O communication, network communication), the redundant components have the same communication interface to ensure that the input information in the card is consistent. The two redundant cards have their own communication paths. As long as the same input information is transmitted on the two communication paths at the same time, the two cards can obtain the same information. This kind of synchronization of input information by external devices is called "natural synchronization". "Natural synchronization" occurs between the redundant system and external equipment. The work card holds the initiative, speaks on behalf of the whole, and transmits various status information to the standby card through redundant communication to achieve synchronization of control tasks, which is "forced synchronization". "Forced synchronization" makes the internal control state of the standby card consistent with the working card through redundant communication, and it occurs between the mutually redundant cards. Depending on the characteristics of the variables, the specific synchronization methods used are also different. 2) Power system redundancy The power source is the source of power for the entire control system to work normally. Once the power supply unit fails, the work of the entire control system will often be interrupted, causing serious consequences. To enable the control system to operate safely, reliably, long-term, and stably, first of all, a stable power supply must be guaranteed. The JX-300X DCS adopts hot-swappable redundant power supplies. During normal operation, the two power supplies each output half of the power, so that each power supply works in a light load state, which is conducive to the stable operation of the power supply. When one of them fails, the other will take over for a short time and give an alarm. It is designed as a hot-swappable redundant power supply, so that the failed power supply can be replaced without affecting the normal operation of the system during system maintenance. 3) Network system redundancy adopts redundant network card and redundant network interface. During normal operation, the two redundant data high-speed channels run in parallel at the same time, automatically apportion network traffic, and consider the redundant design of load balancing to increase the system network communication bandwidth. When one of them fails (the network card is damaged or there is a line failure), the other automatically bears all the communication load to ensure normal communication. 4) The cooling system redundancy utilizes the automatic switchable redundant fan in the control cabinet to monitor the temperature of the fan and the cabinet in real time. When the working fan fails or the temperature in the cabinet is too high, it will automatically alarm and automatically start the backup fan. 5) Information Redundancy Information redundancy technology refers to the use of additional redundant information bits to provide error detection and even error correction capabilities during communication or when storing configuration information (important information). Both SBUS bus communication and SCnet control network in this system adopt cyclic redundancy check (CRC) method. The storage of important configuration information (such as system configuration) in the main control card adopts 1:1 redundant storage, so that important information has the ability to self-recover from failure (error), and ensure the safety of important information during system operation. Over time, battery cables have to be replaced due to corrosion or damage. 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May 17, 2023