Abstract:
The invention relates to a method for controlling a turbine which is characterized by a hidden state at each point in time of the control. The dynamic behavior of the turbine is modeled using a recurrent neural network comprising a recurrent hidden layer. The recurrent hidden layer is formed by vectors of neurons which describe the hidden state of the turbine at the points in time of the control. For each point in time, two vectors are connected chronologically to a first connection which bridges one point in time, and two vectors are additionally connected chronologically to a second connection which bridges at least two points in time. Short-term effects can be corrected by means of the first connections, and long-term effects can be corrected by means of the second connections. Emissions and occurring dynamics can be minimized in the turbine by means of the latter. The invention further relates to a control device and a turbine comprising such a control device.

Description:
[0001]    This application is the National Stage of International Application No. PCT/EP2013/057307, filed Apr. 8, 2013, which claims the benefit of DE 10 2012 206 651.9, filed Apr. 23, 2012. The entire contents of these documents are hereby incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present embodiments relate to the control of a turbine (e.g., a gas turbine or a wind turbine). 
         [0003]    A turbine may assume a large number of successive different states during operation. In order to sense these different states, many different sensors are conventionally used to provide sensor values ascertained on the turbine. 
         [0004]    On account of the resultant complexity, many known control methods for turbines use neural networks. 
         [0005]    An example of such a known method for controlling a turbine using a neural network is described in the patent specification DE 10 2007 001 025 B4. 
         [0006]    The control of a turbine involves correcting short-term effects and long-term effects, for example. Short-term effects may be such effects as are based on short or short-term dependencies of the states of the turbine during operation. Control that is suitable for short-term effects in a turbine is known from WO 2011/110404 A1. By contrast, long-term effects may be such effects as are based on long or long-term dependencies of the states of the turbine during operation. 
         [0007]    For the example of a gas turbine, uncontrolled or less than optimally controlled long-term effects may cause increased emissions from the gas turbine and also occurring dynamics in the gas turbine. 
       SUMMARY AND DESCRIPTION 
       [0008]    The scope of the present invention is defined solely by the appended claims and is not affected to any degree by the statements within this summary. 
         [0009]    The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, control for a turbine that may correct short-term effects and long-term effects is provided. 
         [0010]    A method for controlling a turbine, such as a gas turbine or a wind turbine, is provided. The turbine has a number of sensors for providing sensor values ascertained on the turbine and a number of actuators for actuating the turbine. The turbine is characterized at each instant from a plurality of chronological instants of the control by a hidden state that may be derived by sensor values and a rating signal for the hidden state and may be influenced by alterable actuator values for the actuators. In act a) of the method, the dynamic behavior of the turbine is modeled with a recurrent neural network including an input layer, a recurrent hidden layer, and an output layer based on training data including sensor values, actuator values and rating signals. In this case, the input layer is formed from first vectors of neurons that describe sensor values and/or actuator values at the instants. In addition, the recurrent hidden layer is formed from second vectors of neurons that describe the hidden state of the turbine at the instants. Chronologically, for all the instants, two respective vectors from the second vectors are connected to a first connection that spans one instant, and, also chronologically, two respective vectors from the second vectors are connected to a second connection that spans at least two instants. In addition, the output layer is formed from at least one third vector of neurons that describes the rating signal or at least one portion of the sensor values and/or at least one portion of the actuator values at the instants. 
         [0011]    In act b) of the method, a learning and/or optimization method is performed on the hidden states in order to provide a set of rules having optimized actuator values for each hidden state. 
         [0012]    In act c) of the method, the current hidden state is ascertained the recurrent neural network and currently ascertained sensor values from the sensors. 
         [0013]    In act d) of the method, current actuator values are ascertained in order to actuate the actuators using the provided set of rules and the current hidden state. 
         [0014]    The first connections between the vectors from the second vectors may be used to correct short-term effects, and the second connections may be used to correct long-term effects. The second connections may minimize emissions and also occurring dynamics in the turbine. 
         [0015]    Examples of sensor values are the emission values for the turbine, the exhaust temperature for the turbine, and the ambient temperature and ambient pressure. 
         [0016]    Examples of actuator values are the inlet guide vane position, the total gas stream and mix ratios that are to be set for the gases. 
         [0017]    In one embodiment, the recurrent neural network used is a deployed recurrent neural network. 
         [0018]    In a further embodiment, in act a), the output layer is formed from at least one third vector of neurons that describes the rating signal or, exclusively, such sensor values and/or actuator values as influence the rating signal at the instants. 
         [0019]    In a further embodiment, apart from the current hidden state at the current instant, all the hidden states at the past and future instants are spanned by a second connection. 
         [0020]    In a further embodiment, the second connections are arranged symmetrically about the current hidden state. 
         [0021]    In a further embodiment, the recurrent neural network is divided into two subnetworks that are connected by the current hidden state, where the first subnetwork describes the hidden states for past instants, and the second subnetwork describes the hidden states for future instants. 
         [0022]    In a further embodiment, the first connections and the second connections are formed by neural structures (e.g., by matrices of weights or neural connections) including matrices and further vectors of neurons. 
         [0023]    In a further embodiment, the hidden states in the recurrent hidden layer are connected by weights such that the weights for the future instants differ from the weights for the past instants. 
         [0024]    In a further embodiment, a respective length L is set for the second connections, so that a predetermined number N of instants is spanned (N≧2). 
         [0025]    In a further embodiment, the length of the second connections is set by a heuristic, where the length L of the second connections is chosen such that the total number of necessary steps for reaching the current hidden state from the hidden states of the past instants is minimal. 
         [0026]    In a further embodiment, during the modeling of the dynamic behavior of the turbine, act a) involves the recurrent neural network being trained based on the training data such that the neurons of the third vectors of the output layer are forecast for one or more future instants from one or more past instants. 
         [0027]    In a further embodiment, act a) involves the use of a nonlinear activation function for the recurrent neural network. 
         [0028]    In a further embodiment, the learning and/or optimization method in act b) is a computer learning method (e.g., a strengthening learning method). 
         [0029]    In a further embodiment, the learning and/or optimization method includes dynamic programming and/or prioritized sweeping and/or Q learning and/or a recurrent control neural network (RCNN). By way of example, RCNN is described in the patent specification DE 10 2007 001 025 B4. 
         [0030]    In a further embodiment, the rating signal is represented by a rating function that is dependent at least on a portion of the sensor values and/or actuator values. 
         [0031]    In a further embodiment, the learning and/or optimization method in act b) uses the rating signals in order to implement the actuator values for an optimum rating signal. 
         [0032]    In a further embodiment, the turbine is a gas turbine or a wind turbine. 
         [0033]    In a further embodiment, the turbine is a gas turbine. The rating signal is determined at least by an efficiency and/or a pollutant emission of the gas turbine and/or the alternating pressures and/or the mechanical and/or thermal loads on the combustion chamber of the gas turbine. 
         [0034]    In a further embodiment, the turbine is a wind turbine, where the rating signal is determined at least by the force loading and/or alternating loading on one or more rotor blades of the wind turbine. 
         [0035]    In a further embodiment, in act a), also chronologically, two respective vectors from the second vectors are connected to a third connection that spans at least three instants. 
         [0036]    In addition, a computer program product that prompts the performance of the method as explained above on a program-controlled device is provided. The program-controlled device is a computer, for example. 
         [0037]    A computer program product such as a computer program device may be provided or supplied by a server in a network, by way of example, as a storage medium, such as a memory card, a USB stick, a CD-ROM, a DVD or else in the form of a downloadable file. This may be accomplished, for example, in a wireless communication network by the transmission of an appropriate file with the computer program product or the computer program device. 
         [0038]    In addition, an apparatus for controlling a turbine is provided. The turbine includes a number of sensors for providing sensor values ascertained on the turbine and a number of actuators for actuating the turbine. The actuators are actuated by actuator values. The turbine is characterized at each instant from a plurality of chronological instants of the control by a hidden state. The hidden state may be derived from the sensor values and a rating signal for the hidden state. The hidden state may be influenced by alterable actuator values for the actuators. 
         [0039]    The apparatus has a modeling device, a provision device, an ascertainment device and an output device. The modeling device is set up to model the dynamic behavior of the turbine with a recurrent neural network including an input layer, a recurrent hidden layer, and an output layer based on training data including sensor values, actuator values and rating signals. In this case, the input layer is formed from first vectors of neurons that describe sensor values and/or actuator values at the instants. In addition, the recurrent hidden layer is formed from second vectors of neurons that describe the hidden layer of the turbine at the instants. Chronologically, for all the instants, two respective vectors from the second vectors are connected to a first connection that spans one instant. Also chronologically, two respective vectors from the second vectors are connected to a second connection that spans at least two instants. The output layer is formed by the modeling device from at least one third vector of neurons that describe the rating signal or at least one portion of the sensor values and/or at least one portion of the actuator values at the instants. 
         [0040]    The provision device is set up to perform a learning and/or optimization method on the hidden states in order to provide a set of rules having optimized actuator values for each hidden state. 
         [0041]    The ascertainment device is set up to ascertain the current hidden state using the recurrent neural network and currently ascertained sensor values from the sensors of the turbine. 
         [0042]    The output device is set up to ascertain current actuator values for actuating the actuators using the provided set of rules and the current hidden state, and to output the current actuator values to the actuators of the turbine. 
         [0043]    The respective devices may be implemented in hardware. Alternatively, the devices may be implemented in software. In the case of a hardware implementation, the respective device may be in the form of an apparatus or in the form of part of an apparatus (e.g., in the form of a computer or in the form of a microprocessor). In the case of a software implementation, the respective device may be in the form of a computer program product, in the form of a function, in the form of a routine, in the form of part of a program code, or in the form of an executable object. 
         [0044]    A turbine that includes an apparatus, as explained above, for controlling the turbine is provided. 
         [0045]    In addition, a controller that includes a turbine and an apparatus as explained above, for controlling the turbine is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0046]      FIG. 1  shows a schematic diagram to illustrate the dynamic behavior of a turbine; 
           [0047]      FIG. 2  shows a schematic flowchart for one embodiment of a method for controlling a turbine; 
           [0048]      FIG. 3  shows a schematic illustration of one embodiment of a recurrent neural network for modeling the dynamic behavior of a turbine; and 
           [0049]      FIG. 4  shows a schematic diagram of one embodiment of an apparatus for controlling a turbine. 
       
    
    
     DETAILED DESCRIPTION 
       [0050]    In the figures, elements that are the same or have the same function have been provided with the same reference symbols, unless indicated otherwise. 
         [0051]      FIG. 1  schematically shows the dynamics of one embodiment of a turbine T. In this case, the turbine T is described at a respective instant t by an observable state z t , which is defined by sensor values ascertained on the turbine T, and an action a t  that is performed on the turbine T. The action a t  on the turbine T is determined by actuator values a t  that the actuators use to actuate the turbine T. The turbine T is determined by internal or hidden states s t  that are not directly observable. In this case, the hidden state s t  changes as a result of changing actuator values a t  and proceeds to the state s t+1 . The state s t+1  is dependent on the actuator values a t  and also on the preceding state s t . In addition, the turbine T is specified by a suitable rating signal r t  (not evident from  FIG. 1 ) that defines the extent to which the action performed in a state of the turbine T may be classified as good by the actuator values a t  with respect to optimum operation of the turbine T. Examples of such rating signals are the pollutant emission of the turbine or the mechanical alternating loading on the turbine during operation. The aim of control of the turbine T is low emission and/or low mechanical loading. 
         [0052]    In the present case, suitable modeling of the dynamic behavior of the turbine T is performed taking account of the rating signal r t  based on training data including sensor values, actuator values and rating signals at a plurality of instants t. Details in this regard are discussed with reference to  FIGS. 2 and 3  below. 
         [0053]    In the text below, the rating signal considered is also a remuneration signal, which may also be a reward and may be as large as possible during operation of the turbine T. It is assumed that the description of the turbine based on the states, sensor values and actuator values is what is known as a Markow decision process, but only the remuneration signal r t  is a relevant piece of information for this decision process. Markow decision processes are described in more detail in documents DE 10 2007 001 025 B4 and WO 2011/110404 A1, for example. 
         [0054]    In the present case, the information relevant to the Markow decision process defined by the remuneration r t  is coded into the hidden state s t . Information that is not relevant to the Markow decision process is ignored. To achieve this, the recurrent neural network that is used for modeling the dynamic behavior of the turbine T is designed, for example, such that the recurrent neural network contains sensor values z t  and actuator values a t  that influence the remuneration signal r t  or exclusively the remuneration signal r t  in the output layer O, as will be described in more detail further below (see  FIG. 3 ). A recurrent neural network that may be used for controlling a turbine T is described in WO 2011/110404 A. This neural network may also be called a Markow decision process extraction network (MPEN network). 
         [0055]      FIG. 2  illustrates a flowchart for an exemplary embodiment of a method for controlling a turbine that has acts  201  to  204 . By way of example, the turbine is a gas turbine or a wind turbine. The turbine has a number of sensors for providing sensor values ascertained on the turbine and a number of actuators for actuating the turbine. The turbine is characterized at each instant from a plurality of chronological instants of the control by a hidden state that may be derived by sensor values and a rating signal for the hidden state, and may be influenced by alterable actuator values for the actuators. 
         [0056]    In act  201 , the dynamic behavior of the turbine is modeled with a recurrent neural network including an input layer, a recurrent hidden layer and an output layer based on training data including sensor values, actuator values and rating signals. In this case, the input layer is formed from first vectors of neurons that describe sensor values and/or actuator values at the instants. In addition, the recurrent hidden layer is formed from second vectors of neurons that describe the hidden state of the turbine at the instants. Chronologically, for all the instants, two respective vectors from the second vectors are connected to a first connection that spans a single instant. Also chronologically, two respective vectors from the second vectors are connected to a second connection that spans at least two instants. In addition, the output layer is formed from at least one third vector of neurons that describe the rating signal or at least one portion of the sensor values and/or at least one portion of the actuator values at the instants. 
         [0057]    In act  202 , a learning and/or optimization method is performed on the hidden states in order to provide a set of rules having optimized actuator values for each hidden state. 
         [0058]    In act  203 , the current hidden state is ascertained by the recurrent neural network and currently ascertained sensor values from the sensors. 
         [0059]    In act  204 , current actuator values for actuating the actuators are ascertained by the provided set of rules and the current hidden state. 
         [0060]    The recurrent neural network N described in act  201  is shown in excerpts in  FIG. 3 . The recurrent neural network in  FIG. 3  is a Markow decision process extraction network (MPEN network) with shortcuts C, K in the recurrent hidden layer V that are denoted by C and K in  FIG. 3  and may also be referred to as shortcuts. For this reason, the recurrent neural network N in  FIG. 3  may also be referred to as an MPEN-S network, the S standing for shortcuts. 
         [0061]    The input layer I of the MPEN-S network N in  FIG. 3  is denoted by I, the hidden layer is denoted by V, and the output layer is denoted by O. 
         [0062]    The input layer I includes sensor values z −1 , z 0  and also actuator values a −1 , a 0 , a 1 , a 2 . These are used in a suitable manner for the relevant hidden states s t  in the hidden layer V. The subscript indices in  FIG. 3  denote the respective instant t. Transition matrices are denoted by respective upper case letters A-E and G, H, J, K and L. 
         [0063]    In addition, the remuneration r t  already mentioned above, which is denoted by r 1  for the instant t=1 in  FIG. 3 , is coupled to a hidden state s t  and an action, described by the actuator values a t , that is executed in this hidden state s t . 
         [0064]    In this case,  FIG. 3  reproduces for the output layer O a remuneration r t  that is to be forecast at the current instant t. The remuneration r 1  is therefore valid for the instant t=1, whereas the remuneration r 2  is valid for the instant t=2. 
         [0065]    In the MPEN-S network N in  FIG. 3 , there are two different types of connections in the hidden layer V between the individual neurons. There are first connections B, E, G, H that span one instant t. In addition, there are second connections C, K that span at least two instants and represent the aforementioned shortcuts. The term shortcut arises from the circumstance that for an individual time step, a plurality of instants may be spanned using such a shortcut C, K. 
         [0066]      FIG. 3  shows that the recurrent neural network N is split into two subnetworks N 1 , N 2 . This division of the neural network N in  FIG. 3  is shown by the dashed line. The two portions N 1  and N 2  are connected by the current hidden state s 0 . In this case, the first subnetwork N 1  describes the hidden states s −1  for past instants t −1 , whereas the second subnetwork N 2  describes the hidden states s 1 , s 2  for future instants s 1 , s 2 . Without restricting the general nature,  FIG. 3  shows only one past instant and two future instants. 
         [0067]    The second connections C, K are arranged symmetrically about the current hidden state s 0 . All the hidden states s t  at the past and future instants are spanned by a second connection C, K. The second connections C are used for the past instants, whereas the second connections K are used for the future instants. The current hidden state s 0  is not spanned by a second connection C, K. 
         [0068]    In addition,  FIG. 3  clarifies that in the present case the recurrent neural network N used may be a deployed recurrent neural network N. 
         [0069]    The first connections B, E, G, H and the second connections C, K are formed by neural structures (e.g., by matrices of mixed or neural connections). 
         [0070]    For example, a respective length L is set for the second connections C, K, so that a predetermined number of instants t is spanned (N≧2). 
         [0071]    The length L of the second connections C, K is set by a heuristic. In this case, the length L of the second connections C, K is chosen such that the total number of steps necessary in order to reach the current hidden state s 0  from the hidden states s −2 , s −1  of the past instants L 2 , L 1  is minimal. 
         [0072]    The matrices in the past A-E may be different from the matrices G, H, J, K, L of the future. 
         [0073]      FIG. 4  shows a schematic diagram of one embodiment of an apparatus  40  for controlling a turbine T. The turbine T includes a number of sensors for providing sensor values z t  ascertained on the turbine T and a number of actuators for actuating the turbine T (not shown). The actuators are actuated by actuator values a t  (cf.,  FIG. 1 ). The turbine T is characterized at each instant t from a plurality of chronological instants of the control by a hidden state s t . The hidden state s t  may be derived from the sensor values z t  and a rating signal r t  for the hidden state s t . The hidden state s t  may be influenced by alterable actuator values a t  for the actuators. 
         [0074]    The apparatus  40  has a modeling device  41 , a provision device  42 , an ascertainment device  43  and an output device  44 . The modeling device  41  is set up to model the dynamic behavior of the turbine T with a recurrent neural network N including an input layer I, a recurrent hidden layer V and an output layer O based on training data including sensor values z t  actuator values a t  and rating signals r t  (in this regard, cf.  FIG. 3 ). In this case, the input layer I is formed from first vectors of neurons that describe sensor values z t  and/or actuator values a t  at the instants t. In addition, the recurrent hidden layer V is formed from second vectors of neurons that describe the hidden state s t  of the turbine T at the instants t, where chronologically, for all the instants t, two respective vectors from the second vectors are connected to a first connection B, E, G, H that spans one instant t, and also chronologically, two respective vectors from the second vectors are connected to a second connection C, K that spans at least two instants. The output layer O is formed by the modeling device  41  from at least one third vector of neurons that describe the rating signal r t  or at least one portion of the sensor values z t  and/or at least one portion of the actuator values a t  at the instants t. 
         [0075]    The provision device  42  is set up to perform a learning and/or optimization method on the hidden states s t  in order to provide a set of rules R having optimized actuator values a t  for each hidden state s t . 
         [0076]    The ascertainment device  43  is set up to ascertain the current hidden state s t  using the recurrent neural network N and currently ascertained sensor values z t  from the sensors of the turbine T. 
         [0077]    The output device  44  is set up to ascertain current actuator values a t  for actuating the actuators using the provided set of rules R and the current hidden state s t , and to output the current actuator values a t  to the actuators of the turbine T. 
         [0078]    Although the invention has been illustrated and described in more detail by the exemplary embodiments, the invention is not restricted by the disclosed examples. Other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention. 
         [0079]    It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims can, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification. 
         [0080]    While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description.