Method for Selecting Frequency Signals for Hydropower Turbine Speed ​​Control System

Abstract

A method for selecting the frequency signal of a hydro-turbine speed control system is disclosed. This method collects the PT speed signal at the turbine end and two gear disk speed signals, considering the low accuracy of the PT speed when excitation is not engaged and the speed selection logic under channel fault conditions. Based on the unit's operating status, a suitable signal from the three speed signals is selected as the overall speed of the unit's governor. This invention effectively improves the reliability of the overall speed of the hydro-turbine governor, avoids unit speed fluctuations, and enhances the stability of hydro-turbine unit operation.

Description

Technical Field

[0001] This invention belongs to the field of water turbine speed control technology, and relates to a method for selecting frequency signals in a water turbine speed control system. Background Technology

[0002] In the control of hydro-generator units, the unit speed signal plays a crucial role, and its stability directly affects the safe and stable operation of the unit. Currently, there are relatively mature and effective methods for ensuring the stability and redundancy of the speed measurement signal in the hydro-turbine governor control system. However, there is still room for optimization in the selection logic of the speed measurement signal. When the governor outputs an inappropriate overall speed signal, it can easily lead to uncontrolled unit regulation, power and speed fluctuations, and other problems.

[0003] The speed measurement of hydro-generator units mainly includes two methods: residual pressure speed measurement and gear disc speed measurement. The residual pressure speed measurement method calculates the unit speed by collecting the PT signal at the turbine end. The lower the unit speed, the lower the amplitude of the PT at the turbine end, and the lower the accuracy of the signal measurement. Some units can only accurately measure the PT speed after excitation is put into operation. The gear disc speed measurement method uses a speed probe such as a proximity switch to scan the gear disc fixed on the main shaft of the hydro-generator unit. When the teeth of the gear disc device sweep past the probe, the probe emits a pulse. Its accuracy is independent of the unit speed, but it is limited by the machining accuracy of the gear disc and the installation position of the probe.

[0004] Currently, most hydropower station governor control systems use residual pressure speed measurement and gear disc speed measurement to integrate the overall speed using a computer group, with redundancy between the two. The typical selection method prioritizes the PT speed, followed by sequential selection of the two gear disc speeds. However, when selecting the optimal speed signal as the integrated speed signal, there is a lack of consideration for the low accuracy of the PT speed when excitation is not engaged, and for speed selection logic under channel failure conditions. This may lead to inaccurate integrated speed, reduced unit operational reliability, and other issues that are detrimental to the normal operation of the unit. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a frequency signal selection method for a turbine speed control system, which uses one PT speed signal and two gear disk speed signals, combined with the unit operating status and speed signal channel status, to automatically select the optimal speed signal as the comprehensive speed signal of the governor.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a frequency signal selection method for a turbine speed control system, which collects the PT speed signal and two gear disk speed signals at the turbine end, considers the speed selection logic when the excitation is not engaged, and combines the unit operating status, uses one PT speed signal and two gear disk speed signals, and combines the unit operating status and the speed signal channel status to automatically select the optimal speed signal as the comprehensive speed signal of the governor.

[0007] The operating status transition relationships of the unit speed control system include: Status=1 (shutdown standby) transitions to status=2 (startup process) upon receiving a start-up command; Status=2 (startup process) transitions to status=6 (shutdown process) upon startup failure or receiving a stop command; Status=3 (idle) transitions to status=3 (idle) upon reaching 48Hz; Status=6 (shutdown process) upon receiving a stop command; Status=4 (no-load) transitions to status=4 (no-load) upon receiving a stop command; Status=3 (idle) transitions to status=3 (idle) upon de-excitation; Status=5 (load) transitions to status=4 (no-load) upon circuit breaker opening.

[0008] When the machine is in standby mode, the overall speed output is 0.

[0009] During startup or idling, if both gear speeds are faulty, the overall speed output will be 0, and the speed controller will issue an emergency stop signal. If one gear speed is faulty, the overall speed output will be the speed of the fault-free gear. If both gear speeds are fault-free, the overall speed output will be the higher of the two gear speeds.

[0010] Under no-load or load conditions, if the PT speed is fault-free and either of the two gear disk speeds is faulty, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free, and the difference between the PT speed and either gear disk speed is within 0.5Hz, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free, and the difference between the PT speed and the two gear disk speeds is greater than 0.5Hz, the higher of the two gear disk speeds is selected.

[0011] Under no-load or load conditions, if the PT speed is faulty and both gear speeds are fault-free, the combined speed output will be the higher of the two gear speeds. If the PT speed is faulty and one gear speed is faulty, the combined speed output will be the speed of the fault-free gear. If both the PT speed and both gear speeds are faulty and the unit is under no-load conditions, the combined speed output will be 0, and the governor will issue an emergency shutdown signal. If both the PT speed and both gear speeds are faulty and the unit is under load conditions, the combined speed output will be 50Hz, and the governor will switch to pure manual mode.

[0012] The main beneficial effects of this invention are as follows:

[0013] By utilizing one PT speed signal and two gear disk speed signals, combined with the unit's operating status and the speed signal channel status, the optimal speed signal is automatically selected as the governor's comprehensive speed signal, avoiding speed fluctuations during unit operation and improving the accuracy of hydropower unit control and operational stability.

[0014] Based on the unit's operating status, the appropriate speed signal from the three speed signals is selected as the overall speed of the unit's governor, which effectively improves the reliability of the overall speed of the hydropower unit's governor. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 This is a state transition diagram of the speed regulation system of the present invention.

[0017] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0018] like Figures 1-2 In this paper, a frequency signal selection method for a turbine speed control system is proposed. By collecting the PT speed signal and two gear disk speed signals at the turbine end, considering the speed selection logic when the excitation is not engaged, and combining the unit operating status, the optimal speed signal is automatically selected as the comprehensive speed signal of the governor by using one PT speed signal and two gear disk speed signals, combined with the unit operating status and the speed signal channel status.

[0019] The operating status transition relationships of the unit speed control system include: Status=1 (shutdown standby) transitions to status=2 (startup process) upon receiving a start-up command; Status=2 (startup process) transitions to status=6 (shutdown process) upon startup failure or receiving a stop command; Status=3 (idle) transitions to status=3 (idle) upon reaching 48Hz; Status=6 (shutdown process) upon receiving a stop command; Status=4 (no-load) transitions to status=4 (no-load) upon receiving a stop command; Status=3 (idle) transitions to status=3 (idle) upon de-excitation; Status=5 (load) transitions to status=4 (no-load) upon circuit breaker opening.

[0020] In the preferred configuration, the overall speed output is 0 when the machine is in standby mode.

[0021] In the preferred scheme, during the start-up process or idling state, if both gear speeds are faulty, the overall speed output is 0, and the speed controller issues an emergency stop signal; if one gear speed is faulty, the overall speed output is the speed of the fault-free gear; if both gear speeds are fault-free, the overall speed output is the higher of the two gear speeds.

[0022] In the preferred scheme, under no-load or load conditions, if the PT speed is fault-free and either of the two gear disk speeds is faulty, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free and the difference between the PT speed and either gear disk speed is within 0.5Hz, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free and the difference between the PT speed and the two gear disk speeds is greater than 0.5Hz, the higher of the two gear disk speeds is selected.

[0023] In the preferred scheme, under no-load or load conditions, if the PT speed fails and both gear speeds are functioning correctly, the overall speed output is the higher of the two gear speeds. If the PT speed fails and one gear speed fails, the overall speed output is the speed of the fault-free gear. If both the PT speed and both gear speeds fail, and the unit is in no-load condition, the overall speed output is 0, and the governor issues an emergency shutdown signal. If both the PT speed and both gear speeds fail, and the unit is in load condition, the overall speed output is 50Hz, and the governor switches to pure manual mode.

[0024] In the above method, one PT speed signal and two gear disk speed signals are used, combined with the unit's operating status and the speed signal channel status, to automatically select the optimal speed signal as the governor's comprehensive speed signal, thereby avoiding speed fluctuations during unit operation and improving the accuracy of hydropower unit control and operational stability.

[0025] Based on the unit's operating status, the appropriate speed signal from the three speed signals is selected as the overall speed of the unit's governor, which effectively improves the reliability of the overall speed of the hydropower unit's governor.

[0026] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for selecting a frequency signal in a turbine speed control system, characterized in that: By collecting the PT speed signal and two gear disk speed signals at the generator end, considering the speed selection logic when the excitation is not engaged, and combining the unit's operating status, the optimal speed signal is automatically selected as the governor's comprehensive speed signal using one PT speed signal and two gear disk speed signals, combined with the unit's operating status and the speed signal channel status. The operating status transition relationship of the unit speed control system includes: from the standby state status=1 to the start-up process state status=2 after receiving the start-up command; The startup process status (status=2) switches to the shutdown process status (status=6) after startup failure or receiving a shutdown order; it switches to the idling state (status=3) when the frequency reaches 48Hz; the idling state (status=3) switches to the shutdown process status (status=6) after receiving a shutdown order; it switches to the no-load state (status=4) after excitation is applied; the no-load state (status=4) switches to the shutdown process status (status=6) after receiving a shutdown order; it switches to the idling state (status=3) after de-excitation; it switches to the load state (status=5) after the circuit breaker is closed; and the load state (status=5) switches to the no-load state (status=4) after the circuit breaker is opened. During startup or idling, if both gear speeds are faulty, the overall speed output will be 0, and the speed controller will issue an emergency stop signal. If one gear speed is faulty, the overall speed output will be the speed of the fault-free gear. If both gear speeds are fault-free, the overall speed output will be the higher of the two gear speeds.

2. The frequency signal selection method for a turbine speed control system according to claim 1, characterized in that: When the machine is in standby mode, the overall speed output is 0.

3. The frequency signal selection method for a turbine speed control system according to claim 1, characterized in that: Under no-load or load conditions, if the PT speed is fault-free and either of the two gear disk speeds is faulty, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free, and the difference between the PT speed and either gear disk speed is within 0.5Hz, the combined speed output is the PT speed; if both the PT speed and the two gear disk speeds are fault-free, and the difference between the PT speed and the two gear disk speeds is greater than 0.5Hz, the higher of the two gear disk speeds is selected.

4. The frequency signal selection method for a turbine speed control system according to claim 1, characterized in that: Under no-load or load conditions, if the PT speed fails and both gear speeds are functioning correctly, the combined speed output will be the higher of the two gear speeds. If the PT speed is faulty, and one of the gear disk speeds is also faulty, the overall speed output will be the speed of the fault-free gear disk. If both the PT speed and the two gear disk speeds are faulty, and the unit is in an unloaded state, the overall speed output will be 0, and the speed controller will issue an emergency shutdown signal. If both the PT speed and the two gear disk speeds are faulty, and the unit is in a loaded state, the overall speed output will be 50Hz, and the speed controller will switch to pure manual mode.

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