Discussion on turbine control issues

Our factory is currently using Hilscher’s products

Main functions of the DEH system: Turbine speed control； Automatic synchronization control ； Load control ； Participate in a frequency modulation session ； Coordinated control of machine and furnace ； Rapid load reduction ； Main steam pressure control ； Single-valve control, multi-valve decoupled control ； Valve testing ； Engine programmed start ； OPC control ； Control under load rejection and loss of magnetization conditions ； Dual-machine fault tolerance ； Achieve data sharing with the DCS system ； Manual control.

DEH systems are generally installed in units with a capacity of 300MW or more. A key aspect is the selection of actuators; typically, pressure switches are used, as they need to be suitable for working with high-pressure oil. Additionally, a 3-to-2 configuration is employed in such systems.

The main functions of the DEH control system include: remote automatic reset, tripping, speed control (automatic rapid critical point crossing, automatic synchronization), load control (initial load during grid connection, load circuit control), main steam pressure limitation, extraction steam control, overspeed protection, control of EH equipment, and control of extraction steam check valves

Digital Electro-Hydraulic Control System for Turbines DEH-ⅢA 　　 Section 1: General Introduction 　　 DEH-ⅢA is a next-generation, advanced digital electro-hydraulic control system for turbines, developed by Xinhua Control Engineering Co., Ltd. in 1997, building on nearly a decade of experience in DEH control systems. Since 1997, the DEH-ⅢA control system has been successfully installed in various types of units both domestically and internationally, and has operated safely and reliably for a long time. The power ranges of units equipped with DEH-ⅢA include steam turbines of 600, 300, 200, 125, and 50 MW capacities. The unit types encompass condensing, single-suction, double-suction, and extraction-backpressure types. The startup methods for these units include startup using the high-pressure cylinder, startup using the medium-pressure cylinder, and combined startup using both the high- and medium-pressure cylinders. 　　 The hardware and system design of DEH-ⅢA are primarily based on the original DEH—Ⅲ developed by Ding Xinhua Control Engineering Co., Ltd.; for instance, the principles and main circuits of various specialized cards (valve control card, speed measurement card, overspeed protection card) are identical to those of DEH—Ⅲ. At the same time, DEH-ⅢA incorporates the advantages of several major foreign DCS systems and keeps up with the development trends of DCS. In terms of the selection of the main control computer and the design of the communication network, it uses standard industrial control PCs with PCI/ISA bus architectures, along with mature Ethernet communication. Thanks to the use of standard hardware, the main control computer and network communication of DEH-ⅢA can keep up rapidly with the trends in computer development. With each upgrade of a computer’s CPU, higher-grade host cards become available on the market that can be purchased directly for use in DEH-ⅢA. The various dedicated card assemblies and other I/O cards are entirely produced by Xinhua Control Engineering Co., Ltd., ensuring stability. It ensures the advancement and reliability of DEH-ⅢA. 　　 The DEH-ⅢA mainboard has been upgraded from a 486 CPU at the time of its initial operation to a Pentium III/IV CPU. The speed of Ethernet has increased from 10M to the current 100M. 　　 Before 2000, turbine DEH systems generally used dedicated hardware and were independent of other thermal control systems in the power plant. With the widespread use of Distributed Control Systems (DCS) in power plants and various industries, as well as the rapid advancement of computer technology, people’s understanding of computer-based control techniques has improved further, and the concept of using dedicated control systems for DEH systems has been challenged. More and more users are opting for an integrated design of DEH and DCS, that is, by using the same hardware platform and system software. The DEH serves as one station within the plant’s DCS, responsible for controlling the turbine, with full data sharing between the DEH and the DCS. 　　 DEII-ⅢA is a system with strong versatility and good system openness, making it easy to expand. By adding additional DPU and I/O stations, components such as feedwater pump turbines and bypass control systems can be established, thereby forming an integrated control system for the power plant’s turbine island. This system can also be combined with the XDPS—400 DCS system from Xinhua Control Engineering Co., Ltd. to create an integrated control system for the entire power plant. It can also be connected to other manufacturers’ DCS systems over the network, serving as a station within the DCS system to share data with them. 　　 Section 2: Characteristics of DEH—ⅢA 　　 DEH is specialized equipment for the regulation and control of steam turbines, and it serves as a key control system in the thermal control system of Volcano Power Plant. The reliability of the DEH system is key to the proper operation of the entire power plant. In DEH design, system reliability is given top priority. DEH-ⅢA adopts various reliability assurance measures such as redundant configuration, hardware backup, and anti-interference techniques. Page 204: DEH-IIIA is a system that has been further optimized on the basis of summarizing the operational experience with DEH systems and the control requirements for various types of turbines. Its functions and logical design take into full account the reliable operation of the turbines, as well as the plant’s turbine, boiler, and power generation systems under different operating conditions. For the various functional operations performed by the operator on DEH-Ilia 1, there are corresponding logical interlocks and operation guidelines; any incorrect operation commands will not be executed by the system. The DEH-111A system boasts unique advantages in terms of its sophistication and reliability, as well as its ability to adapt well to the control functions, operation modes, and requirements of domestic power plants. 　　 The DEH-IIIA system is a electro-hydraulic control system for steam turbines that uses high-pressure fire-resistant oil. Its computer system utilizes the XDPS—400 distributed control system platform developed by Xinhua Control Engineering Co., Ltd., featuring advanced functionality and ease of use. The hydraulic system employs a high-pressure fire-resistant fuel electro-hydraulic servo control system, offering fast and precise operation. 　　 DEH-IIIA is further expanded to form the control system for the power plant’s turbine island. Its functions cover the turbine control system DEH, the feedwater pump and turbine control system MEH, the turbine bypass control system BP(2), the turbine emergency shutdown protection system ETS, the turbine auxiliary equipment control system SCS, and more. 　　 The DEH-IlIA hardware features a distributed control system architecture. It has communication interfaces with other systems such as the DCS system, GPS clocks, and MIS systems, enabling data sharing with systems like DCS. 　　 The control system uses a Chinese Windows operating system with a fully Chinese-based human-machine interface. The software configuration is carried out in a graphical manner, in compliance with the 1KC—1131 standard; by simply connecting the inputs and outputs of various functional blocks graphically, the configuration of the control system can be completed ； After a dedicated drawing software for screen configuration is dynamically connected to a database, it is easy to create rich display and operation interfaces. 　　 The basic control of the turbine (including basic control functions such as speed control, power control, valve management, valve testing, and overspeed protection) and the automatic start-stop control ATC of the turbine (including turbine parameter monitoring, stress calculation, life management, and automatic start-stop control of the turbine based on stress calculation and condition monitoring) each utilize redundant DPU units. It features various control modes such as operator-automatic OA control, boiler-turbine coordinated CCS control, ATC control, and combined CCS-ATC control. 　　 In DEH-Ilia, the OPC overspeed control and overspeed protection are separated from the basic control and are handled by independent hardware that does not rely on the DPU, which ensures the speed and reliability of the OPE. The system uses six speed measurement cards to separate the basic control speed measurement and overspeed control from the speed measurement for the overspeed protection OPC. Three of the speed measurement cards are used for basic speed control with a 3-to-2 selection, while the other three are used for OPC speed control with a 3-to-2 selection. OPC functions include 103% overspeed control at the rated speed, pre-valve closing upon load rejection, 110% overspeed protection, and online overspeed testing. It can be shut down via ETS at 110% overspeed. 　　 The control of steam valves in the turbine is achieved using an intelligent valve servo control card (vCC). One servo control card corresponds to a set of valve servo mechanisms and valves, forming a servo control loop that precisely controls each valve to the desired opening degree in accordance with the DEH control commands, thereby meeting the control requirements under various operating conditions of the turbine. 　　 The position measurement of the valve servo actuator uses dual-redundant linear differential displacement sensors (LVDTs). LVDTs enable contactless measurement, ensuring the reliability of long-term monitoring of valve operation. The two redundant LVIYFs, in combination with the dual LVDTs on the intelligent VCC card, eliminate potential safety hazards such as accidental full-opening of the valve caused by a failure of a single LVDT. 　　 DEH-IIIA benefits from years of design experience, and its functions can better meet the needs of domestic users. For valve testing, there are both full-stroke testing and partial-stroke testing. It features a well-developed interface with the bypass system, enabling operation modes such as startup of the turbine’s high-pressure cylinder, medium-pressure cylinder, or both high and medium pressure cylinders; operation with or without a bypass; island operation; and operation with plant electricity. The system employs multi-variable, multi-stage feedback control loops to ensure dynamic response and static performance, and it participates in both primary and secondary frequency regulation of the power grid. It enables complete decoupled control of power and extraction pressure in the extraction turbine unit. 　　 DEH-IIIA has an emulator interface. The simulator can mimic boilers, steam turbines, motors, and electrical systems. It connects to DEH-IIIA via hardware signal interfaces to simulate real-world signals, enabling full-functional closed-loop hardware simulation. It can also be used with EH system actuators for physical simulations, allowing for comprehensive closed-loop simulation tests of plant startup, speed increase, load operation, valve control, load shedding, and more. 　　 This post was last edited by Mobei Yihai on 2009-1-18 at 19:31.]

Our company uses Woodward’s 505E for the control of its turbines. The 505E electronic governor is a microprocessor-based device for controlling the speed of turbines; it can be programmed to be used for controlling the speed of generators and turbines. It can be controlled manually or automatically, features stable performance, and allows for the configuration of alarm signals and shutdown signals. The main inputs of 505E are as follows: Analog signals: speed signal (pulse), power signal (4–20mA), and extraction steam signal (4–20mA). Digital signals: main steam valve open, startup, speed increase, speed decrease, extraction steam increase, extraction steam decrease, generator switch (electrical supply), grid switch, speed up/pause, manual shutdown signal, low safety oil pressure, ETS trip signal, CPC1 overload signal, and CPC2 overload signal. Out of range: The given value does not match the feedback. The main outputs are: analog signals: two 4‑20mA current signals (CPC1 and CPC2): rotational speed (100‑4500 n/min), extraction steam pressure setpoint (0-2 MPa) (fed to the DCS). The digital signals include: 505 for shutdown/alarm/OK, power limit alarm, extraction/power/frequency activation, the opening degrees of the two valves, and power signals. TSI is the Bentley 3500 system.

Here, we will use an AB 1756 PLC together with a Bentley 3300; as for the electro-hydraulic servos, it’s not yet decided. These components will form a small steam turbine generator set! It is currently in design!

Reply to 4# shd163207: I think what you said, brother, isn’t very reasonable. As far as I know, DEH is more commonly used in units with a capacity of less than 300MW! I would be grateful for your advice!

Could someone tell me the control principle of a turbo-generator?