Systems, methods, and apparatus for controlling turbine guide vane positions

Certain embodiments of the invention may include systems, methods, and apparatus for controlling turbine guide vane positions. According to an example embodiment of the invention, a method is provided for controlling at least one turbine guide vane. The method includes receiving a reference signal associated with the at least one turbine guide vane, measuring an actuator position and an angular position associated with the at least one turbine guide vane, generating a deadband signal based at least in part on the angular position, and manipulating the at least one turbine guide vane based at least in part on the deadband signal and the reference signal.

FIELD OF THE INVENTION

This invention generally relates to turbines, and in particular, to systems, methods, and apparatus for controlling turbine guide vane positions.

BACKGROUND OF THE INVENTION

Turbine compressors often utilize adjustable guide vanes in the inlet of the turbine to control air flow and pressure over a range of operation. The guide vanes are typically arranged in a row in the stationary (non-rotating) part of the compressor casing, and in some cases, 40 to 60 or more vanes are used on each turbine. The vane blade stem ends typically extend through a compressor casing, and may be attached to a linkage that simultaneously turns each individual vane blade. For example, a “uni-center ring” may be utilized to turn each individual blade as the ring is rotated circumferentially around the compressor inlet casing. Depending on whether one or more rows of these vanes are to be controlled, linkage elements may be ganged together to control the rows of vanes in unison.

To move the linkage, and in turn, adjust the guide vanes, a servo system including a hydraulic actuator is typically employed. For example, the position of the hydraulic actuator may be monitored and fed back to a controller in the servo system using transducers such as resolvers, linear variable differential transformers (LVDTs) or linear variable differential reluctance (LVDR) devices. One of the complications with such a system is that there may be a complex and non-linear relationship between the transducer measurement and the actual angle of the vane blades due not only to geometric and rotational transformations, but also to manufacturing tolerances and wear in the linkage. A lack of precision in the positioning of the guide vanes and/or variable stator vanes can result in a corresponding lack of precision in the control of flow through the machine, possibly resulting in a loss of output or efficiency or both.

BRIEF SUMMARY OF THE INVENTION

Some or all of the above needs may be addressed by certain embodiments of the invention. Certain embodiments of the invention may include systems, methods, and apparatus for controlling turbine guide vane positions, for instance, compressor inlet and variable stator vanes.

According to an example embodiment of the invention, a method is provided for controlling at least one turbine guide vane. The method includes receiving a reference signal associated with the at least one turbine guide vane, measuring an actuator position and an angular position associated with the at least one turbine guide vane, generating a deadband signal based at least in part on the angular position, and manipulating the at least one turbine guide vane based at least in part on the deadband signal and the reference signal.

According to another example embodiment, a system is provided for controlling air flow in a turbine. The system includes a gas turbine, at least one guide vane operable to control turbine axial air flow, and a controller. The controller is configured to receive a reference signal associated with the at least one guide vane, measure an actuator position and an angular position associated with the at least one guide vane, generate a deadband signal based at least in part on the angular position, and manipulate the at least one guide vane based at least in part on the deadband signal and the reference signal

According to another example embodiment, an apparatus is provided for controlling air flow in a turbine. The apparatus includes at least one guide vane operable to control turbine axial air flow and a controller. The controller is configured to receive a reference signal associated with the at least one guide vane, measure an actuator position and an angular position associated with the at least one guide vane, generate a deadband signal based at least in part on the angular position, and manipulate the at least one guide vane based at least in part on the deadband signal and the reference signal.

Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. Other embodiments and aspects can be understood with reference to the following detailed description, accompanying drawings, and claims.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may enable angular position control of compressor inlet and variable stator vanes, thus improving air flow control in a turbine. According to certain example embodiments, the use of rotary angle measurement devices such as resolvers or encoders and their use in a feedback control system may be used to provide direct sensing and control of the angular position for inlet guide vanes and variable stator vanes for axial compressors. In accordance with example embodiments, the invention may include a control algorithm combining the mechanisms of direct angular vane position measurement with the traditional linear actuator position measurement to mitigate any problems in direct feedback control of systems with hysteresis.

Example embodiments of the invention enable direct rotary angle measurements of the inlet or variable stator vanes for use in a compression system. According to an example embodiment, the measurements may be used in a feedback control system for positioning gas turbine or compression system guide vanes with improved accuracy and repeatability.

Various components, linkages, sensors, and servo system configurations for controlling the position of the guide vanes, according to example embodiments of the invention, will now be described with reference to the accompanying figures.

FIG. 1illustrates an example block diagram of equipment used in a direct vane angle control system, according to an example embodiment of the invention. According to example embodiments of the invention, the components shown inFIG. 1may be utilized to control the inlet guide vanes (IGV's) and variable stator vanes (VSV's) of an axial flow compressor on a gas turbine. According to an example embodiment of the invention, a hydraulic servo102may be used to manipulate a guide vane actuator110. The guide vane actuator may be connected to any number of components (such as turnbuckles, torque tubes, unison ring, lever arms, etc.) collectively referred to as the guide vane linkage system114. According to an example embodiment of the invention, components of the guide vane linkage system114may be utilized to translate the linear motion of the actuator110into the rotary motion of a guide vane actuation ring116. Individual vanes may be connected via lever arms to vane actuation ring116, and the vanes may rotate according to the motion of the vane actuation ring116. In accordance with example embodiments of the invention, and as indicated inFIG. 1, a linear translation sensing device112, such as a linear variable differential transducer (LVDT), may be utilized to monitor the linear position of the guide vane actuator110ram or piston. In accordance with example embodiments of the invention, a rotary angle sensing devices118(such as resolver, rotational variable differential transducer (RVDT), or encoder, for example) may also be used to directly measure the rotation of an individual guide vane.

FIG. 2depicts a block diagram of an illustrative direct vane control system200according to an example embodiment of the invention. The control system200may include a controller202. According to an example embodiment, the controller202may include a memory204, one or more processors206, and one or more input/out (I/O) interfaces208. Certain embodiments of the invention may include one or more network interfaces210. The memory204may include an operating system (OS)212and data214. According to example embodiments of the invention, the memory204may be configured or programmed with one or more special purpose modules for controlling the guide vane actuator, such as110inFIG. 1, based on input received from the linear translation sensing device, such as112, and the rotary angle sensing devices, such as118. For example, the memory204may include a servo module216and a deadband module218, which will be further described below.

FIG. 3depicts a typical control system block diagram. This diagram is included to illustrate an issue that may be overcome by using certain embodiments of the invention. The control system300ofFIG. 3may be utilized, for example, in a hydraulic servo system acting through a mechanical linkage for position control of inlet guide vanes or variable stator vanes on a gas turbine compressor. For example, a position command or position reference302may be summed with feedback304to produce an error306. A control gain308may be applied to the error306to provide input to a servo310, which may control an actuator312. The actuator position320may be measured by a linear position sensor318(for example by an LVDT position sensor) and used for feedback304. The guide vane position324, in this case, may be adjusted based on the linear position sensor318, which may be separated from the actual guide vanes by linkage314. This control system300may be used to adjust the output of the linkage314, to match the output of the position reference302. Assuming that the linkage314is suitable and that linear position sensor318is suitably calibrated, then the output of the linear position sensor318may be sufficient to predict the guide vane position for feedback control purposes.

FIG. 4depicts the ideal situation described above, where the guide vane linkage system, such as114inFIG. 1, is suitable (for example, without hysteresis or play) and the linear translation sensing device, such as112inFIG. 1, is suitably calibrated.FIG. 4, for example, shows an ideal tracking line406that is plotted as a function of guide vane angle402vs. the guide vane command404. The ideal tracking line406follows the ideal response408in this hypothetical perfect system, and in such a case, a simple control system, such as300inFIG. 3, may be adequate to control such a suitable system.

However, with any real mechanical linkage used to translate the linear motion of the hydraulic actuator ram to the rotary motion of the individual guide vanes, there may inevitably be a small but non-zero amount of slop or play present, arising due to the accumulation of manufacturing tolerances in the various fittings between the linkage components. This slop or play may result in two undesirable effects on the vane positioning system: (1) there may be a loss in absolute positioning accuracy, and (2) there may be a loss in repeatability, due to effects such as hysteresis. Example embodiments of this invention may alleviate both of these effects.

FIG. 5depicts a graph of an illustrative guide vane angle vs. command with linkage hysteresis500according to an example embodiment of the invention. In this figure, the guide vane angle502is plotted as a function of the guide vane command504. As inFIG. 4, the ideal tracking line506is shown as a linear relationship between the two variables (502,504). However, if the guide vane linkage system, such as114inFIG. 1, is imperfect, the actual guide vane angle508may not follow the ideal tracking line506, but instead, may have positioning error510.

In a departure from existing control methods, and according to example embodiments of the invention, error in positioning of the guide vanes due to play, non-linearities, etc., in the guide vane linkage system, such as114inFIG. 1, may be at least partially compensated or reduced by combining measurements taken at the guide vane actuator, such as110inFIG. 1, using the linear translation sensing device, such as112inFIG. 1, and measurements taken at the guide vanes using a rotary angle sensing device, such as118inFIG. 1.

FIG. 6illustrates a combined deadband control system block diagram600, according to an example embodiment of the invention, which may utilize guide vane actuator position622and guide vane angular position624as feedback, and additionally utilize a deadband process620or module to improve positioning accuracy and repeatability in the guide vane control.

In accordance with an example embodiment of the invention, a nominal guide vane reference signal602may be used as an input to the control system600. The nominal guide vane reference signal602may be summed with a deadband signal621in summing junction604to produce a guide vane reference signal606. In an example embodiment, a measured guide vane actuator position feedback signal619may be subtracted from the guide vane reference signal606, and the resulting error signal may be utilized in an inner feedback loop626. According to an example embodiment, the inner feedback loop626may include control gain608, a servo610a hydraulic actuator (with position limits)612and a guide vane actuator position sensor618. In accordance with an example embodiment of the invention, the guide vane actuator position sensor618may provide the guide vane actuator position feedback signal619for use within both the inner feedback loop626, and an outer feedback loop628, which will be described below.

In accordance with an example embodiment of the invention, the outer feedback loop628may receive the guide vane actuator position622, which may be utilized to control the linkage system (with hysteresis)614, resulting in a guide vane angular position624that may be measured by a guide vane angular position sensor616. In an example embodiment, the resulting measured guide vane angular position feedback signal617may be subtracted from the measured guide vane actuator position feedback signal619(generated via the inner feedback loop626), and the resulting error may be fed into a deadband process620or module. According to an example embodiment, the deadband process620or module may produce a deadband signal621that may be added to the nominal guide vane reference signal602.

According to an example embodiment, the deadband process620may produce a deadband signal621that is about zero unless an associated input signal to the deadband process620exceeds a predetermined magnitude. In accordance with an example embodiment, the deadband signal621may linearly relate to the deadband process620input signal when the input signal exceeds the predetermined magnitude. For example, the deadband signal621may comprises an output signal of about zero unless the associated input signal exceeds about 0.05 percent of full scale. If the input signal exceeds about 0.05 percent of full scale, then the deadband output signal621may linearly relate to the deadband process620input signal. In accordance with example embodiments of the invention, the predetermined limit may be set or adjusted as necessary, and may range, for example, from about 0.01 percent of full scale to about 10 percent of full scale, depending on the condition of the linkage system and other factors. According to example embodiments, the deadband signal621may be based on a difference between the guide vane actuator (linear) position622and the guide vane angular position624.

FIG. 7is a graph of illustrative guide vane reference positions as a function of time, and according to an example embodiment of the invention. The solid curve in this graph represents an example nominal guide vane reference position702, which may be used as input to the control system, such as guide vane leakage system602inFIG. 6. When the mechanical linkage, such as guide vane leakage system114inFIG. 1, includes play and/or hysteresis, and when the control system, such as300inFIG. 3, is utilized where only feedback from the linear actuator is used, such as feedback304inFIG. 3, then a guide vane position may not accurately follow the nominal guide vane reference position702. Such a case is depicted in the curve labeled704inFIG. 7. However, for a relatively similar mechanical system (with hysteresis), when the combined deadband control system600, such as inFIG. 6, is utilized, the actual guide vane position with linear and angular actuator feedback706may more accurately follow the nominal guide vane reference position702.

An example method800for controlling at least one turbine guide vane will now be described with reference to the flow diagram ofFIG. 8. The method800starts in block802, where, according to an example embodiment of the invention, the method includes receiving a reference signal associated with at least one turbine guide vane. In block804, the method800includes measuring an actuator position and an angular position associated with the at least one turbine guide vane. In block806, the method800includes generating a deadband signal based at least in part on the angular position. And in block808, the method800includes manipulating the at least one turbine guide vane based at least in part on the deadband signal and the reference signal. The method800ends after block808.

Accordingly, example embodiments of the invention can provide the technical effects of creating certain systems and methods that provide positioning gas turbine or compression system guide vanes with improved accuracy. Example embodiments of the invention can provide the further technical effects of providing systems and methods for positioning gas turbine or compression system guide vanes with improved repeatability.

In example embodiments of the invention, the direct vane control systems100,200and the combined deadband control system600may include any number of software and/or hardware applications that are executed to facilitate any of the operations.

In example embodiments, one or more I/O interfaces may facilitate communication between the direct vane control systems100,200and the combined deadband control system600, and one or more input/output devices. For example, a universal serial bus port, a serial port, a disk drive, a CD-ROM drive, and/or one or more user interface devices, such as a display, keyboard, keypad, mouse, control panel, touch screen display, microphone, etc., may facilitate user interaction with the direct vane control systems100,200and the combined deadband control system600. The one or more I/O interfaces may be utilized to receive or collect data and/or user instructions from a wide variety of input devices. Received data may be processed by one or more computer processors as desired in various embodiments of the invention and/or stored in one or more memory devices.

One or more network interfaces may facilitate connection of the direct vane control systems100,200and the combined deadband control system600inputs and outputs to one or more suitable networks and/or connections; for example, the connections that facilitate communication with any number of sensors associated with the system. The one or more network interfaces may further facilitate connection to one or more suitable networks; for example, a local area network, a wide area network, the Internet, a cellular network, a radio frequency network, a Bluetooth™ enabled network, a Wi-Fi™ enabled network, a satellite-based network, any wired network, any wireless network, etc., for communication with external devices and/or systems.

As desired, embodiments of the invention may include the direct vane control systems100,200and the combined deadband control system600with more or less of the components illustrated inFIGS. 1,2and6.