Abstract:
The invention relates to methods and systems for optimizing the distribution of electrical energy in an electrical power supply system (I) which comprises autonomous supply system regions ( 5, 6, 7, 8, 9 ), comprising the method steps of:—receiving input data (II) by at least two dispatcher instances ( 5   a,    7   a ), wherein the input data (II) represents energy intervals ( 5   i,    6   i,    7   i,    8   i,    9   i ) which are requested by the autonomous supply system regions ( 5, 6, 7, 8, 9 );—calculating at least one solution ( 5   s,    7   s ) of the distribution of electrical energy to the supply system regions ( 5, 6, 7, 8, 9 ) by each of the at least two dispatcher instances (5 a,    7   a );—selecting one of the calculated solutions (5 s,    7   s ) for the distribution of electrical energy in the power supply system (I) by means of a leader election. The invention relates to the technical field of distributing electrical energy and can be used, for example, for smart grids.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Application No. PCT/EP2014/074177, having a filing date of Nov. 10, 2014, based off of DE Application No. 102014201555.3 having a filing date of Jan. 29, 2014, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The following relates to the technical field of the distribution of electrical energy. 
       BACKGROUND 
       [0003]    Algorithms regarding the leader election are known: http://en/wikipedia/org/wiki/Leader_election. DE 10 2011 078 045 A1 additionally discloses methods and devices for allocating quantities of energy. 
         [0004]    New energy grids, also referred to as soft grids, are composed of autonomous regions, which are also referred to as islands or grid regions and which are balanced among one another by means of the mutual distribution of the energy. This balancing can be realized by a node, which is also referred to as a dispatcher or optimizer and which, on the basis of energy intervals requested by the autonomous regions, collects all the required information by means of a generic interface and/or to which this information is transmitted. Required information may comprise, depending on the island, for example, a forecast energy demand, a forecast energy output and/or flexibility with regard to the forecast energy demand and/or energy output of the island. 
         [0005]    The dispatcher then attempts to calculate the optimum distribution of the available energy over the autonomous regions and assigns energy transfers to the latter. 
         [0006]    There are various possible approaches for optimizing the distribution of the available energy. The energy flows can be controlled centrally by means of an external dispatcher/optimizer or by one of the peers, that is to say one of the islands, being chosen as a node for the dispatcher/optimizer which calculates the transmissions of energy by means of an algorithm having low complexity. 
         [0007]    However, an individual central management node configured as a dispatcher entails disadvantages such as communication bottlenecks, load spikes at one of the peer nodes or a single point of failure. Moreover, it is possible for the central management node to yield only suboptimal results on account of limited time available to it, limited computing power and limited memory space. 
         [0008]    In order to alleviate these disadvantages, the following approaches may be employed:
       provisioning the dispatcher with increased resources, e.g. a better CPU;   passing on the dispatcher role among the available nodes, e.g. always to the node having the fullest battery;   a central dispatcher with redundant or overprovisioned communication connections;   concepts for failsafe protection, such as e.g. hot backup of the dispatcher;   heartbeat monitoring of the dispatcher and selection procedure for replacement in the case of a malfunction.       
 
         [0014]    However, these approaches only alleviate individual disadvantages, and moreover require an increased outlay for their implementation. 
       SUMMARY 
       [0015]    An aspect relates to optimizing the distribution of electrical energy in an electrical power grid comprising autonomous grid regions. 
         [0016]    In accordance with one aspect, a method for optimizing the distribution of electrical energy in an electrical power grid is presented. The power grid comprises autonomous grid regions. The method comprises the following method steps: In one method step, input data are received by at least two dispatcher entities. The input data represent energy intervals requested by the autonomous grid regions. In a further method step, at least one solution of the distribution of electrical energy among the grid regions is calculated by each of the at least two dispatcher entities. In a further method step, one of the calculated solutions for the distribution of electrical energy in the power grid is selected. 
         [0017]    In accordance with a further aspect, a system for optimizing the allocation of electrical energy in an electrical power grid is presented. The electrical power grid comprises autonomous grid regions. The system comprises at least two dispatcher entities and a selection means or device. Each of the at least two dispatcher entities comprises an interface means or device and a calculation means or device. The interface means or device of the at least two dispatcher entities are in each case adapted to receive input data representing energy intervals requested by the autonomous grid regions. The calculation means or device of the at least two dispatcher entities are in each case adapted to calculate a solution of the distribution of electrical energy among the grid regions. The selection means or device is adapted to select one of the calculated solutions for the distribution of electrical energy in the power grid. 
     
    
     
       BRIEF DESCRIPTION 
         [0018]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0019]      FIG. 1  shows a block diagram of a power grid controlled by a data network, in accordance with one exemplary embodiment of the invention; 
           [0020]      FIG. 2  shows a block diagram of a system in accordance with one exemplary embodiment of the invention for optimizing the allocation of electrical energy in the power grid from  FIG. 1 ; and 
           [0021]      FIG. 3  shows a flow diagram of a method in accordance with one exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Elements having an identical function and effect are provided with the same reference signs in the figures. 
         [0023]      FIG. 1  shows a power grid  1 , which is controlled by a data network  19 , in accordance with one exemplary embodiment of the invention. 
         [0024]    The power grid  1  is highlighted in  FIG. 1  by the elements depicted using bold lines and comprises the autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9  and electrical connections that connect the autonomous grid regions to one another. As illustrated in  FIG. 1 , not all of the autonomous grid regions need be connected to all of the other autonomous grid regions. Rather, there are diverse possibilities for interconnecting the autonomous grid regions. In reality, in a large power grid generally not all grid regions are connected to all grid regions, for cost reasons and on account of geographical conditions. 
         [0025]    The data network  19  is highlighted in  FIG. 1  by the elements depicted using lines of normal thickness and comprises the entities  5   a,    6   a,    7   a,    8   a,    9   a  and data connections that connect said entities  5   a,    6   a,    7   a,    8   a,    9   a  to form the network  19 . The data network  19  need not have the same topology as the power grid  1 , rather it can have its own topology. Each of the autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9  of the power grid comprises at least one entity  5   a,    6   a,    7   a ,  8   a,    9   a  which controls the respective autonomous grid region. At least two of the entities  5   a,    6   a ,  7   a,    8   a,    9   a  are configured as dispatcher entity. These are the entities  5   a  and  7   a  in the exemplary embodiment illustrated in  FIG. 1  and  FIG. 2 . 
         [0026]      FIG. 2  shows a system  2  for optimizing the allocation of electrical energy in an electrical power grid  1  comprising autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9 . The system  2  comprises at least two dispatcher entities  5   a,    7   a  and a selection means or device  3 . Each of the at least two dispatcher entities  5   a,    7   a  comprises an interface means or device  5   b,    7   b  and a calculation means or device  5   c,    7   c.  Each of the interface means  5   b,    7   b  of the at least two dispatcher entities  5   a,    7   a  is adapted to receive input data  11 . The input data represent energy intervals  5   i,    6   i,    7   i,    8   i,    9   i  requested by the autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9 . Each of the calculation means  5   c,    7   c  of the at least two dispatcher entities  5   a,    7   a  is adapted to calculate a solution  5   s,    7   s  of the distribution of electrical energy among the grid regions  5 ,  6 ,  7 ,  8 ,  9 . The selection means  3  is adapted to select one of the calculated solutions  5   s,    7   s  for the distribution of electrical energy in the power grid  1  by means of a leader election. 
         [0027]      FIG. 3  shows a method for optimizing the distribution of electrical energy in the power grid  1  in accordance with one preferred exemplary embodiment of the invention. Method step  31  involves determining, for each of the grid regions  5 ,  6 ,  7 ,  8 ,  9 , its expected energy demand in the form of a respective energy interval  5   i,    6   i,    7   i,    8   i,    9   i;  also see  FIG. 1 . These energy intervals  5   i,    6   i,    7   i,    8   i,    9   i  are received as input data  11  by two dispatcher entities  5   a,    7   a  in method step  32 . The input data  11  thus represent the energy intervals  5   i,    6   i,    7   i,    8   i,    9   i  requested by the autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9 . In this case, in  FIG. 3  the reception of the input data I by dispatcher entity  5   a  is represented by method substep  32   a,  while the reception of the input data I by dispatcher entity  7   a  is represented by method substep  32   b.  In method step  33 , each of the at least two dispatcher entities  5   a,    7   a  calculates a solution  5   s,    7   s  of the distribution of electrical energy among the grid regions  5 ,  6 ,  7 ,  8 ,  9 . In  FIG. 3  the calculation of the solution  5   s  by the dispatcher entity  5   a  is represented by method substep  33   a,  while the calculation of the solution  7   s  by the dispatcher entity  7   a  is represented by method substep  33   b.  In method step  34 , one of the calculated solutions  5   s,    7   s  for the distribution of electrical energy in the power grid  1  is selected by means of a leader election. For this purpose, for example, the selection means  3  may be adapted to evaluate the calculated solutions  5   s,    7   s  by a target value function  3   z  and to compare them with one another in the leader election. In this case, the target value function yields for each of the solutions  5   s,    7   s,  for example a scalar value which represents the quality of the solution, and thus enables the comparison. Instead of scalar values, however, the target value function  3   z  may for example also yield vectors which enable a comparison. 
         [0028]    In accordance with preferred exemplary embodiments, all of the at least two dispatcher entities  5   a,    7   a  receive the same input data  11 . 
         [0029]    In accordance with further preferred exemplary embodiments, the at least two dispatcher entities  5   a,    7   a  are adapted to calculate in each case different solutions  5   s,    7   s  of the distribution of electrical energy among the grid regions  5 ,  6 ,  7 ,  8 ,  9 . This may preferably be achieved for example by virtue of the fact that the at least two dispatcher entities  5   a,    7   a  are adapted to select, for the calculation of the respective at least one solution, different start populations within the energy intervals  5   i,    6   i,    7   i,    8   i,    9   i.  A further possibility, however, is for example that the at least two dispatcher entities  5   a,    7   a  are adapted to use different algorithms for the calculation of the respective at least one solution  5   s,    7   s.    
         [0030]    In accordance with further preferred exemplary embodiments, the grid regions  5 ,  6 ,  7 ,  8 ,  9  will be represented logically as a selection from energy producers, energy consumers and prosumers. In this case, prosumers constitute grid regions which can either produce or consume energy. This is the case for example with pumped-storage power plants. A further example of a prosumer may also constitute an electric vehicle or a group of electric vehicles whose battery, for stabilizing the power grid, depending on grid demand, can be charged or can make electricity available to the power grid. In the case of a prosumer, the requested energy interval can overlap zero, e.g. battery can be charged and discharged. 
         [0031]    As illustrated in  FIG. 2 , the system  2  may comprise only the dispatcher entities  5   a ,  7   a  and the selection means, or it may also comprise the power grid. The power grid  1  is or comprises a DC voltage grid or an AC voltage grid. 
         [0032]    In preferred embodiments the target value function  3   z  is defined for the dispatcher entity and represents the optimality of the solution calculated by the dispatcher entity for the distribution of electrical energy. This is a byproduct of the actual calculation of the optimum distribution of the energy. 
         [0033]    This may be achieved for example by virtue of the fact that, in a concrete implementation, the values of a cost function, as described in the German patent application DE102011078045 A1, are summed for the assigned energy coordinates. The cost function is transmitted in the input data  11  with the energy intervals  5   i,    6   i,    7   i,    8   i,    9   i  and expresses a preference within the energy interval, namely to optimize the costs. The optimization is intended to attempt always to achieve the minimum of the cost function. 
         [0034]    The required information for the respective dispatcher entity  5   a,    7   a  is preferably broadcast by each of the entities in order that the dispatcher entities have available a possible complete data set for the calculation of the distribution of the electrical energy. In this case, each entity embodied as node  5   a,    6   a,    7   a,    8   a,    9   a  receives the information and relays it as required in order to make a complete image available to all further entities  5   a,    6   a,    7   a,    8   a,    9   a.    
         [0035]    In accordance with a further preferred embodiment, all entities  5   a,    6   a,    7   a,    8   a,    9   a  function as dispatcher entity in order to calculate a solution configured as energy distribution using the broadcast information and randomly chosen initial starting states. After the calculation, or if the allotted time window for the calculation has elapsed, each entity  5   a,    6   a,    7   a,    8   a,    9   a  broadcasts the value of the target value function for its respectively calculated solution. 
         [0036]    The entities  5   a,    6   a,    7   a,    8   a,    9   a  compare their values in accordance with a bullying scheme. This means that a node broadcasts its resulting value of the target value function. If one dispatcher entity  5   a,    6   a,    7   a,    8   a,    9   a  receives a message from another dispatcher entity  5   a,    6   a,    7   a ,  8   a,    9   a  with a lower, that is to say less optimal, value, it broadcasts a message with its own higher value. If messages are no longer obtained within a given time after the last message, that solution having the last and thus highest value wins. By way of example, that dispatcher entity  5   a,    6   a,    7   a ,  8   a,    9   a  with the best solution wins and transmits its calculated solutions for the distribution of electrical energy to the other entities  5   a,    6   a,    7   a,    8   a,    9   a,  which then implement the calculated distribution of the electrical energy among the autonomous grid regions  5 ,  6 ,  7 ,  8 ,  9 . 
         [0037]    Other methods different than the bullying algorithm may also be used, such as, for example, a ring algorithm; see http://en.wikipedia.org/wiki/Leader_election. 
         [0038]    In accordance with preferred embodiments, instead of an individual dispatcher entity, the optimization of the distribution of electrical energy is performed in a manner distributed over two or more dispatcher entities  5   a,    6   a,    7   a,    8   a,    9   a.  As a result, the problem of a single point of failure is eliminated and the stability is increased. Moreover, the calculated solutions can be improved by the distributed calculation since these solutions of a plurality of dispatcher entities are compared and the best solution is selected. It also enables individual nodes  5   a,    6   a,    7   a,    8   a,    9   a  to function as a dispatcher entity and to participate in the calculation of the solution, or not to do this owing to limited resources. 
         [0039]    Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. 
         [0040]    For the sake of clarity, it is to be understood that the use of ‘a’ or ‘an’ throughout this application does not exclude a plurality, and ‘comprising’ does not exclude other steps or elements.