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Mawan Power Plant #5 and #6 units are domestically-received 300 MW coal-fired generating units. The main engine is the products of Harbin Sanda Power Plant. The boiler is a forced-cycle drum boiler, and the pulverizing system is equipped with six medium-speed coal mills. Milling System. The unit is equipped with two 50% capacity steam-powered feed pumps and one 50%-capacity electric feed pump.
The DCS system of the second stage project adopts the XDPS-400 distributed control system produced by Shanghai Xinhua Control Engineering Co., Ltd. The functional coverage includes DAS system (data acquisition system), MCS system (analog control system), FSSS system (burner management) System), SCS system (sequential control system), DEH system (turbine digital electro-hydraulic control system), MEH system (small turbine control system) and ECS system (electrical control system).
The software configuration and on-site commissioning of the MCS system are undertaken by Guodian Thermal Engineering Institute, including a simple configuration of the electric bypass control system.
The control range of the MCS system in the #5 and #6 units is the same as that of the hardware and software. In the following description, only the #5 unit that has already been put into operation will be described.
The MCS system occupies three DPUs (Decentralized Processing Units) of No.16, No.17 and No.18 of the DCS system. The No.16 DPU mainly completes the automatic adjustment of the main control system, fuel system, primary air system and pulverizing system of the unit, No.17. The DPU mainly completes the automatic adjustment of the air supply system, pilot air system, auxiliary air, fuel air, and fuel air control system. The No. 18 DPU mainly completes the main steam temperature, reheat steam temperature, main boiler feedwater control, deaerator water level and pressure. Control, condenser water level control, #1-#3 high pressure heater and #5-#8 low pressure heater water level control system and automatic adjustment of high and low pressure bypass. Other simple single-loop control systems are scattered in DPUs 16 and 17. The entire unit has only 6 base-type control systems.
Mawan Power Plant #5 unit passed the 168-hour full-load test run on November 1, 2002. At the start of the 168-hour trial run of the unit, the machine-furnace coordinating control system including the highest level of automation on behalf of the unit has been delivered to the normal operation of the operating personnel. The input rate of the automatic adjustment system has reached 100%, and the adjustment quality has reached the “fundamental construction project of the thermal power plantâ€. Startup and completion acceptance procedures. During the entire trial run of the unit, there was no unplanned shutdown and furnace shutdown accident. The early and reliable investment in the MCS system played an important role in the safe and stable operation of the unit. The authors will discuss some of the experiences of the XDPS-400 distributed control system during the process of software configuration and on-site commissioning of the #5 unit MCS system.
1. High reliability of hardware Starting from the DCS system's on-site cabinet power, each DPU and I/O module has been in working condition until the 168-hour trial run of the unit is completed. The hardware used in the MCS system is only In the output modules used in the #2 high-add and #3 high-add hydrophobic trap control loops, three analog output channels were damaged (probably caused by intrusion of the local junction box into strong electricity). All other hardware works. normal. The accuracy of some of the I/O modules had been spot-checked at the site and all were in compliance with Xinhua's factory regulations and the contractual requirements with the owners. In general, the threat to the security of the hardware of the DCS system during the construction of the infrastructure is much greater than that during normal production. The XDPS-400 distributed control system can achieve such reliability and prove its system hardware. It is trustworthy.
2. Short control cycle Before using the decentralized control system, the MCS system is actually an uninterrupted continuous process control. After the decentralized control system is adopted, since the computer has multiple tasks that need to respond, and each control function module needs to be calculated in a certain order, this creates a problem of a control cycle. In theory, the shorter the control cycle, the closer it is to continuous control, the easier the accuracy of the control system can be guaranteed. In general decentralized control systems, the majority of the control period for the MCS system is 250 milliseconds, and 500 milliseconds or even 1000 milliseconds are used. XDPS-400 distributed control system can set the control cycle according to the page, and there are multiple control cycles to choose from. In this project, we have set the control period of the MCS system to 200 milliseconds. Considering that all the analog control systems of each 300 MW unit are all concentrated in three pairs of DPUs, such a short control cycle can be achieved until the unit hands over production. No exception was found. The author thinks it is very satisfactory.
3. The function of the control module is more fully within the decentralized control system. It is a series of control function blocks (ie, function codes) to realize the intended control function of the designer. The original function code of the XDPS-400 distributed control system has been able to basically meet the control requirements of large-scale thermal power units. However, in order to realize some special design ideas, the author proposed several functions on behalf of the owner in the design liaison meeting of this project. The requirements for modification and improvement of the code were renewed as required by Xinhua, meeting the requirements of the owner, and taking the opportunity to upgrade the function code. These upgraded function codes play a predictable role in the coordinated control of the furnace and main steam temperature and reheat steam temperature control system, enabling certain unconventional predictive control functions to be completed. In contrast, if the introduction of distributed control systems to achieve the requirements to modify the function code is almost impossible, it also reflects the competitiveness of the domestic distributed control system.
4. On-line configuration and parameter debugging are more convenient In the XDPS-400 distributed control system used in this project, all monitored DPUs are dual redundantly configured. When an engineering workstation is used to connect an online DPU, its internal control configuration can be directly modified in the simplest way. The modified control configuration is executed immediately. There are no compiling steps and the work is completed. The instruction copies the modified control configuration to the backup DPU. Because of the frequent need to make certain modifications to the control configuration during on-site commissioning and maintenance of the MCS system, this feature is particularly convenient. For example, in the adjustment of the drum level control system, it was found that the actual high level of the drum water level signal fluctuates too much, and once the water level control system is still kept in the automatic control mode, a filtering function block is added to the water level measurement signal loop. Due to attention to the order of connection of various modules, there is no disturbance to the control system.
In addition, on the display screen of the engineer's workstation, in addition to the signal signal values ​​and trend diagrams of the control system similar to other distributed control systems, it is also possible to connect several small fixed-length trends in the configuration diagram. The function code, these minor trends and control configuration are on the same display screen, and will not be hidden along with the configuration modification or parameter adjustment of this screen. For some single loop control system dynamic parameter adjustment, the adjusted parameters can be observed at any time. The trend is dynamically modified to shorten the commissioning time.
5. All Chinese interface, easy to operate and maintain The display screens of the XDPS-400 distributed control system for the monitoring and control of the operating personnel are all in Chinese, which brings great convenience to the operation and maintenance personnel. Even on the control system configuration diagram, various Chinese comment characters can be configured to facilitate the understanding and memory of the thermal maintenance personnel. In the previous decentralized control system, after the infrastructure transfer phase was completed and transferred to the production operation, the thermal power plant maintenance personnel often found it difficult to understand the original design intent when looking at the control system configuration diagram. That is, the design commissioning personnel did not touch the drawings after several months. When you look back, you often have to work hard to understand drawings. In this project, we added a large number of Chinese comment characters to the configuration diagram. The function of each part can be said to be clear at a glance, which greatly facilitates the thermal power plant maintenance personnel and is highly praised by the power plant personnel.
6. The system is simple and easy to learn. Finding contact signals is convenient in the seven or eight decentralized control systems that the author has contacted. From the perspective of applications, the XDPS-400 distributed control system is the easiest to be familiar with and masters, and generally has WINDOWS applications. The basic personnel can learn the daily system software and hardware operation and maintenance through a week or so of training. In the division of thermal engineering overhaul of most power plants in the country, the teams are usually divided into groups according to the control system. When only a few thermal workers are on duty on holidays or nights, if there is an abnormal situation on the site, the thermal maintenance personnel often do not Being familiar with the control logic of the other team's jurisdiction, the cause of the failure could not be found within a short period of time, thereby delaying the handling of defects or failures and posing a threat to the safe operation of the unit. In the XDPS-400 distributed control system, if the operator finds a display, a chain, or a help screen on the display screen to be faulty, he or she can use the mouse to call up the DPU from which the fault signal comes from, and then any of the thermal maintenance personnel On the engineer's workstation, the cause of the fault signal can be easily identified by the name of the fault signal, time is given for troubleshooting, and convenience is given to the thermal maintenance personnel. At the same time, within the same DPU or between different DPUs, it is easy to jump through the inter-page connection signal of the system or find the connection signal through the signal name, which brings great convenience to system debugging and routine maintenance.
7. The system can be run on any computer in real time and can be simulated off-line. The XDPS-400 distributed control system can be installed on any general-purpose desktop or laptop computer to run in real time. It can simultaneously virtualize multiple DPUs in real-time running status, of course. At this time, all live signals and network connection signals will become bad quality. Even so, many open-loop and closed-loop simulations can be performed off-line via input and output signal forcing. For example, the action direction check of the closed-loop control system, the mathematical model fitting of the dynamic characteristic curve and the influence of the dynamic parameter adjustment on the transition curve of the control system can be completed off-line. On the one hand, the on-line debugging time is reduced and the unit's safe operation is favorable. On the other hand, an improved simulation of the closed-loop control system and training of maintenance personnel can also be performed offline.
To sum up, the XDPS-400 distributed control system of Xinhua Company is not only inferior to or even exceeds imported equipment in terms of hardware reliability and operability of software, but also can be used for large-scale generator sets of more than 300MW.
The planned installed capacity of Shenzhen Mawan Power Plant is 4 sets of 300MW coal-fired generating units, which is the continuation of the construction of Shenzhen Mawan Power Plant. The four-machine group was built in two phases. The unit number was extended to the #1 and #2 units in Mawan Power Plant. The #3 and #4 units in Phase I were put into operation in 1996 and 1997, respectively. The #5 generating unit in the second phase of the project has been put into production in November 2002. The #6 generating unit is scheduled to be put into production in 2003.