Speed regulation redundancy control system for low-pressure turbine oil steam turbine and control method of speed regulation redundancy control system

Abstract

The invention provides a low-pressure turbine oil steam turbine speed regulation redundancy control system which comprises an electro-hydraulic converter A, an electro-hydraulic converter B, a shuttle valve, a quick-closing electromagnetic valve, a regulation air valve hydraulic servo-motor and a DCS control system. Secondary control oil pressure PA and secondary control oil pressure PB output by the electro-hydraulic converter A and the electro-hydraulic converter B respectively pass through a control oil way A and a control oil way B and are subjected to high-selection logic selection through a shuttle valve, then an adjusting air valve hydraulic servo-motor is driven to act through a quick-closing electromagnetic valve, and a servo card A and a servo card B are respectively in communication connection with a DCS (Distributed Control System). According to the control method based on the control system, for the low-pressure turbine oil steam turbine, a shuttle valve is used as a selection element of a redundancy control loop, the fault conditions that components such as a servo card, an electro-hydraulic converter and an LDT displacement sensor break down, signal interference occurs or an oil way of the electro-hydraulic converter is blocked are fully considered, and stable operation and undisturbed switching of the system are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbine redundant control, and particularly relates to a speed regulation redundant control system for a low-pressure turbine oil steam turbine and a control method thereof. Background Art

[0002] In recent years, major generator enterprises have continuously raised the requirements for the operation safety and reliability of steam turbine units, aiming to reduce the number of unplanned or unnecessary shutdowns of the units. Many different ideas have emerged for the exploration and research of multi-device redundant control of steam turbine DEH / MEH systems. There are low-level redundant designs for a certain control device or feedback instrument, such as dual LVDT redundancy. When one LVDT (displacement sensor) fails, it can be immediately switched to a standby LVDT device. There are also high-level redundant control systems in which two sets of DEH / MEH control systems operate independently and are backup to each other.

[0003] The existing steam turbine DEH / MEH redundant control systems mainly target high-pressure fire-resistant oil or medium-pressure oil systems with servo valves as the core control components, and there are significant differences in control methods from low-pressure turbine oil systems that use electro-hydraulic converters (electronically controlled pressure regulating valves) as the core control components to drive hydraulic mechanical feedback actuators (oil motors). Moreover, there is currently no corresponding research on redundant systems in the field of low-pressure turbine oil DEH / MEH control.

[0004] In addition, the redundant systems of the existing technology also have the following defects: The existing technology uses two servo valves to drive the actuator simultaneously. When a single-channel system has a problem, it is necessary to cut off the faulty channel through a solenoid valve. The time interval for issuing the cut-off command depends on the system scan cycle and fault operation time. If this delay time is too large, it may cause a large displacement deviation of the actuator, resulting in abnormal steam turbine power or speed and triggering a shutdown; The cut-off solenoid valve is an electro-hydraulic control component, and its failure rate is higher than that of general mechanical hydraulic components. If any one of the two cut-off solenoid valves fails, the redundant system fails, resulting in no available backup system or directly causing a shutdown; The existing technology requires that each of the two control loops in the redundant system be equipped with a servo card with redundant control functions. The two servo cards need special connecting wires for data exchange, and the servo card needs to be switched after a failure, resulting in a narrow selection range and high cost of the servo card. In addition, as an electronic device, the servo card also has problems of increased functions and reduced reliability. Summary of the Invention

[0005] The purpose of the present invention is to provide a speed regulation redundant control system for a low-pressure turbine oil steam turbine and a control method thereof, which are applicable to the low-pressure turbine oil DEH / MEH system, can achieve high-reliability and low-cost redundant transformation, fully consider faults, maintain stable operation, perform seamless switching, and have the ability to be overhauled.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions: A low-pressure turbine oil turbine speed regulation redundant control system, including an electro-hydraulic converter A, an electro-hydraulic converter B, a shuttle valve, a fast-closing solenoid valve, a regulating valve oil motor and a DCS control system, wherein the electro-hydraulic converter A and the electro-hydraulic converter B respectively output a secondary control oil pressure P A and P B The high selection logic is selected through the control oil circuit A and the control oil circuit B through the shuttle valve, and then the air valve oil motor is driven and adjusted through the fast closing solenoid valve. The electro-hydraulic converter A and the electro-hydraulic converter B are controlled by the servo card A and the servo card B respectively, and the servo card A and the servo card B are respectively connected to the DCS control system for communication.

[0007] Furthermore, the regulating air valve oil motor is installed with LVDT displacement sensor A and LVDT displacement sensor B corresponding to control oil circuit A and control oil circuit B respectively, and the displacement feedback signals of LVDT displacement sensor A and LVDT displacement sensor B are respectively connected to servo card A and servo card B, and the displacement feedback signal is connected to the DCS control system through the displacement output node of the servo card.

[0008] Furthermore, pressure sensor A and pressure sensor B are installed on the control oil circuit A and the control oil circuit B respectively, and pressure sensor A and pressure sensor B respectively send the collected secondary control oil pressure signals of electro-hydraulic sensor A and electro-hydraulic sensor B to the DCS control system.

[0009] Furthermore, the control oil circuit A and the control oil circuit B are respectively installed with a stop valve A and a stop valve B, which are used to close the control oil circuit A and the control oil circuit B by manual intervention.

[0010] A redundant control method for speed regulation of a low-pressure turbine oil steam turbine uses two independent electro-hydraulic converters A and B to control the regulating valve oil motor. The P generated by the electro-hydraulic converter A and the electro-hydraulic converter B A and P B Enter the A port and B port of the shuttle valve respectively; When P A The pressure is equal to P B When the pressure is , the valve core of the shuttle valve is in the middle position, and the three ports of the shuttle valve are all connected. At this time, the pressure oil of the regulating valve oil motor is provided by the control oil circuit A and the control oil circuit B at the same time; when P A The pressure is higher than P B When the valve core of the shuttle valve moves toward port B and closes port B under the action of pressure difference, the control oil circuit A provides driving oil pressure, P B Cut-off; when P B The pressure is higher than P AWhen the time comes, the spool of the shuttle valve moves towards port A and closes port A under the action of the pressure difference. At this time, the driving oil pressure is provided by the control oil circuit B, and P A is cut off.

[0011] Furthermore, the servo card A and the servo card B send the collected signals to the DCS control system for fault diagnosis and processing; the LVDT displacement sensor A and the LVDT displacement sensor B corresponding to the control oil circuit A and the control oil circuit B respectively send the collected displacement feedback signals to the DCS control system for monitoring and fault diagnosis; the pressure sensors arranged on the control oil circuit A and the control oil circuit B output by the electro-hydraulic converter A and the electro-hydraulic converter B send the collected oil pressure signals to the DCS control system for fault diagnosis.

[0012] Furthermore, the DCS control system can send a zeroing command to the servo card A or the servo card B, commanding the servo card A or the servo card B to cut off the faulty circuit and ensure the single-circuit operation of the normal circuit.

[0013] Furthermore, the stop valve A or the stop valve B installed on the control oil circuit A or the control oil circuit B can manually cut off the faulty circuit.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention relates to a low-pressure turbine oil steam turbine speed regulation redundant control system and its control method, which aims at the low-pressure turbine oil DEH / MEH system, can realize the redundant transformation with high reliability and low cost, fills the market gap, uses the shuttle valve as the selection element of the redundant control loop, fully considers the failure of components such as servo cards, electro-hydraulic converters, and LDT displacement sensors, signal interference, or the blockage of the electro-hydraulic converter oil circuit, etc., realizes the stable operation of the system, seamless switching, and has the ability of on-line maintenance.

[0015] Specifically, as the selection element of redundant control, the shuttle valve, due to being a pure mechanical part, has a much lower failure rate than electronic and electrical parts. The MTTF can reach 150 - 1200 years, and there is basically no maintenance pressure. Even under the condition that the cleanliness of the oil source is guaranteed, it is maintenance-free for life.

[0016] The shuttle valve can shield the faulty circuit and make the normal circuit work alone without any external intervention. Due to the characteristics of the low-pressure turbine oil electro-hydraulic control system, the electro-hydraulic conversion device outputs hydraulic oil pressure to control the oil motor, which determines that in most fault situations (such as spool wear, open or short circuit of the control electromagnetic coil, spool jamming, etc.), the control oil pressure of a single circuit is lower than the normal working condition. When a single-circuit fault occurs, the shuttle valve can quickly make a corresponding selection, select the circuit with high oil pressure, that is, the normal output oil pressure, and cut off the faulty circuit. This process does not require the DCS system or the servo card to judge and issue commands. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of the hydraulic principle of the present invention.

[0018] Figure 2 It is a schematic diagram of the logic principle of the present invention.

[0019] Reference numerals: 1, electro-hydraulic converter; 2, shuttle valve; 3, fast-closing solenoid valve; 4, regulating air valve oil motor; 5, pressure sensor; 6, LVDT displacement sensor; 7, stop valve. Detailed implementation manners

[0020] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] The speed control system of the small turbine of the feed water pump in a certain power plant is a typical low-pressure turbine oil control system. The feed water pump has a single capacity of 100%. If a failure occurs in the small turbine of the feed water pump, it will directly affect the main generating unit and may lead to an unscheduled shutdown. Therefore, it is necessary to perform a redundant transformation of the dual control on the existing MEH system of the small turbine of the feed water pump to improve the reliability of the entire generating unit.

[0022] The small turbine of the feed water pump adopted by this power plant is a 2H32-01 unit. The hydraulic system is a low-pressure turbine oil system. The speed regulation of the steam turbine is controlled by two regulating steam valve oil motors, namely a high-pressure one and a low-pressure one. The DCS control system is EDPF-NT+.

[0023] Since the low-pressure regulating valve has been used to meet the feed water capacity requirement since the small turbine of the feed water pump in this power plant was put into operation, and the high-pressure regulating valve has not been used, a second control system for the low-pressure regulating valve oil motor is added in this transformation to form a redundant system. Two Voith electro-hydraulic converters 1 are both installed on the 2oo3 overspeed protection module, as Figure 1 shown, the pipeline of the low-pressure regulating valve oil motor is transformed. On the side of the low-pressure regulating valve oil motor, the original oil inlet module is removed and replaced with a redundant oil inlet module installed with a shuttle valve 2 and a fast-closing solenoid valve 3. The original low-pressure regulating air valve oil motor 4 is installed with a single LVDT displacement sensor 6. A double-branch LVDT mounting bracket is designed and manufactured so as to add a LVDT displacement sensor 6. One LVDT is used for each single path of the redundant system. The added LVDT is connected to the servo card that originally controls the high-pressure regulating air valve oil motor 4, and the LVDT of the original high-pressure regulating air valve oil motor 4 is disconnected. Two independent hydraulic control systems are formed according to the design scheme, and the redundant module installed with the shuttle valve 2 and the fast-closing solenoid valve 3 is used to drive the low-pressure regulating steam valve oil motor 4.

[0024] Preferably, pressure sensors 5 are respectively installed on the two control oil circuits, and the pressure sensors 5 send the secondary control oil pressure signals collected into the DCS control system.

[0025] Preferably, stop valves 7 are respectively installed on the two control oil paths to manually intervene and close the corresponding control oil paths.

[0026] During this transformation of the power plant, full consideration was given to failure situations such as servo cards, electro-hydraulic converters, LVDTs and other components malfunctioning, signal interference, or the oil path of the electro-hydraulic converter being blocked. By adding fault judgment and handling, and alarm logics such as large instruction feedback deviation, comprehensive servo card failure, and large deviation between the two oil pressures, when a component such as a servo card, electro-hydraulic converter, or LVDT malfunctions or the oil path of the electro-hydraulic converter is blocked, the system can maintain stability, can achieve seamless switching through logical OR or closing the oil supply valve, etc., and has the ability of on-line maintenance.

[0027] Specifically, as Figure 2 shown, the MEH control system is provided with a fault alarm system. When faults such as comprehensive servo card failure (including LVDT failure, servo card input instruction failure, servo card self-failure or power loss), large deviation between the two oil pressures, large A-channel instruction feedback deviation, and large B-channel instruction feedback deviation occur, it will trigger a luminous alarm to remind the monitoring personnel, and at the same time automatically switch to the manual operation mode of the small steam turbine to maintain the system problem. The MEH fault alarm system fully considers the characteristics of the shuttle valve high-select oil pressure to prevent the oil pressure entering the oil motor from abnormally increasing and the valve from abnormally opening when a fault occurs. The MEH fault alarm system is provided with a control loop that clears the corresponding servo card instruction when the A-channel instruction feedback deviation is large and the B-channel instruction feedback deviation is large, preventing the valve from abnormally opening and ensuring the safe and reliable operation of the system.

[0028] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A low-pressure turbine oil turbine speed regulation redundant control system, characterized in that: It includes an electro-hydraulic converter A, an electro-hydraulic converter B, a shuttle valve, a fast-closing solenoid valve, a regulating air valve oil motor and a DCS control system. The electro-hydraulic converter A and the electro-hydraulic converter B respectively output a secondary control oil pressure P A and P B The high selection logic is selected through the control oil circuit A and the control oil circuit B through the shuttle valve, and then the air valve oil motor is driven and adjusted through the fast closing solenoid valve. The electro-hydraulic converter A and the electro-hydraulic converter B are controlled by the servo card A and the servo card B respectively, and the servo card A and the servo card B are respectively connected to the DCS control system for communication.

2. A low-pressure turbine oil turbine speed regulation redundant control system according to claim 1, characterized in that: The regulating air valve oil motor is equipped with an LVDT displacement sensor A and an LVDT displacement sensor B corresponding to the control oil circuit A and the control oil circuit B respectively. The displacement feedback signals of the LVDT displacement sensor A and the LVDT displacement sensor B are respectively connected to the servo card A and the servo card B. The displacement feedback signals are connected to the DCS control system through the displacement output node of the servo card.

3. A low-pressure turbine oil turbine speed regulation redundant control system according to claim 1 or 2, characterized in that: The control oil circuit A and the control oil circuit B are respectively installed with a pressure sensor A and a pressure sensor B, and the pressure sensor A and the pressure sensor B respectively send the collected secondary control oil pressure signals of the electro-hydraulic sensor A and the electro-hydraulic sensor B to the DCS control system.

4. A low-pressure turbine oil turbine speed regulation redundant control system according to claim 1, characterized in that: The control oil circuit A and the control oil circuit B are respectively installed with a stop valve A and a stop valve B, which are used to close the control oil circuit A and the control oil circuit B by manual intervention.

5. A low-pressure turbine oil steam turbine speed regulation redundant control method, characterized in that: Two independent electro-hydraulic converters A and B are used to control the oil motor of the regulating gas valve. The P generated by the electro-hydraulic converter A and B A and P B Enter the A port and B port of the shuttle valve respectively; When P A The pressure is equal to P B When the pressure is , the valve core of the shuttle valve is in the middle position, and the three ports of the shuttle valve are all connected. At this time, the pressure oil of the regulating valve oil motor is provided by the control oil circuit A and the control oil circuit B at the same time; when P A The pressure is higher than P B When the valve core of the shuttle valve moves toward port B and closes port B under the action of pressure difference, the control oil circuit A provides driving oil pressure, P B Cut-off; when P B The pressure is higher than P A When the valve core of the shuttle valve moves toward port A and closes port A under the action of pressure difference, the control oil circuit B provides the driving oil pressure, P A Deadline.

6. A low-pressure turbine oil steam turbine speed regulation redundant control method according to claim 5, characterized in that: The servo card A and the servo card B send the collected signals to the DCS control system for fault diagnosis and processing; the LVDT displacement sensor A and the LVDT displacement sensor B corresponding to the control oil circuit A and the control oil circuit B respectively send the collected displacement feedback signal to the DCS control system for monitoring and fault diagnosis; the pressure sensor set on the control oil circuit A and the control oil circuit B output by the electro-hydraulic converter A and the electro-hydraulic converter B sends the collected oil pressure signal to the DCS control system for fault diagnosis.

7. A low-pressure turbine oil steam turbine speed regulation redundant control method according to claim 6, characterized in that: The DCS control system can issue a zeroing instruction to the servo card A or the servo card B, instructing the servo card A or the servo card B to cut off the faulty circuit to ensure the single-circuit operation of the normal circuit.

8. A low-pressure turbine oil steam turbine speed regulation redundant control method according to claim 6, characterized in that: The stop valve A or the stop valve B installed on the control oil circuit A or the control oil circuit B can manually cut off the faulty circuit.

Images