Abstract:
A method determines a cabling of a unit of a photovoltaic system. The unit includes a number of solar components and a transfer point. The method includes generating a cabling chart with paths between a connection of each solar component and the transfer point according to cable routing regulations, determining preferred paths of each solar component to the transfer point based on the cabling charts, and selecting one of the determined paths for each solar component such that the cabling complexity for the unit is minimized. In the process, the cabling complexity is determined based on the sum of the lengths of the selected paths and the length of a cable channel in which the cables run individually or in a bundled manner.

Description:
[0001]    The present patent document is a §371 nationalization of PCT Application Serial Number PCT/EP2014/052771, filed Feb. 13, 2014, designating the United States, which is hereby incorporated by reference in its entirety. This patent document also claims the benefit of DE 10 2013 203 647.7, filed on Mar. 4, 2013, which is also hereby incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    The disclosed embodiments relate to a cabling method and to a method for the determination of an optimum routing of cables in a photovoltaic installation. 
       BACKGROUND 
       [0003]    A photovoltaic installation is divided into one or more units. Each unit includes a number of solar components and a transfer point. The solar components may be configured e.g. as solar modules, each of which includes a number of solar cells with a glazed cover panel and a mounting frame. In other forms, the solar components may be configured differently, for example in the form of a number of solar modules or a number of solar cells. The solar components may be secured rigidly in a predetermined orientation, or may be arranged to track the position of the sun, either individually or in combination. In the case of a stationary arrangement of solar components, the transfer points of units observe a uniform pattern, and there is no variation in the design of units, such that the routing of cables within each unit may be arranged in a uniform manner. 
         [0004]    However, where solar components track the sun, a grouping of solar components is governed, not only by electrical criteria, but also by mechanical criteria. The object, for example, is that as many solar components as possible should track the sun via a common drive system. Tracking involves the rotation of solar components around an axis. 
         [0005]    Accordingly, the grouping of solar components in the units of a photovoltaic installation may pose a complex problem. The routing of cables between the solar components and a transfer point in each unit also poses a subsidiary problem. In general, the solar components of each unit are arranged individually, and an individual transfer point is provided. The laying of cables is governed by rules, for example, solar components may be quadrilateral, whereby cables are only to be laid parallel to the edges of solar components. Accordingly, the edges of solar components are arranged in parallel pairs, such that cables may only be routed in two directions, at right-angles to each other. A further rule may dictate that cables are only to be laid outside the perimeter of solar components. In a large photovoltaic installation, horizontally-routed cable sections are embedded in the ground. To this end, cable ducts are provided, for the accommodation of one or more cables, running from one of the solar components to the transfer point. 
         [0006]    For electrical reasons, the cables between the individual solar components and the transfer point of each unit are kept as short as possible. At the same time, expenditure for the provision of cable ducts is kept as low as possible, in order to save costs. 
         [0007]    For an individual unit in the photovoltaic installation, this problem is resolved forthwith by the execution of a first act, in which all potential cabling options are constituted in accordance with existing rules, and a second act for the selection of those cabling options that provide the optimum fulfillment of the criteria specified. An exhaustive optimization of all the cable routing options constituted may be executed, for example, via a mixed-integer program, which identifies an optimum solution. 
         [0008]    However, the workload associated with the determination of optimum cable routes for several tens, several hundred or even several thousand units may be so great that even a state-of-the art computing facility is not capable of defining optimized solutions for all units within an acceptable time. Accordingly, a run-through of multiple planning variants for a planned photovoltaic installation, or a rapid response to a change in project requirements, is not possible. 
       SUMMARY AND BACKGROUND 
       [0009]    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. 
         [0010]    The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, the disclosed embodiments may provide a method for the determination of a cabling of a unit in a photovoltaic installation, which permits the rapid identification of an optimum solution using modest resources. 
         [0011]    A method for the determination of a cabling of a unit in a photovoltaic installation, in which the unit includes a number of solar components and a transfer point, includes generating a cabling chart with paths between a connection of each solar component and the transfer point, in accordance with specified cable routing regulations, and determining, based on the cabling chart, of preferred paths between each solar component and the transfer point, and selecting one of the paths thus determined for each solar component such that a workload associated with the cabling of the unit is minimized to the greatest possible extent. To this end, the cabling workload is determined based on a sum of the lengths of the selected paths and the length of a cable duct in which the cables are routed, either individually or in a bundled arrangement. 
         [0012]    By considering both cable lengths and the length of the cable duct, a successful compromise for optimization, in both technical and economic terms, may be defined. The definition of preferred paths provides (e.g., ensures) that, from the large number of potential paths available, the preferred paths chosen are those likely to be applied in an effective solution. In the interest of reducting the complexity of the optimization process, less probable paths may be discarded at an early stage, thereby permitting the definition of cabling with an acceptable workload. Specifically, if the method is to be executed for multiple units in the photovoltaic installation, the efficiency of this method may contribute to the improvement of the planning of the photovoltaic installation as a whole, for example, with respect to variations or changing requirements, and may also be executed a number of times. 
         [0013]    Solar components may be provided with a number of alternative connections. Accordingly, the cabling chart may be plotted between all these alternative connections and the transfer point. For example, a solar module that combines a number of solar cells in a manageable unit may be provided with two connections that are arranged opposite each other and may be used alternatively. By considering all the potential links between both connections and the transfer point, the structural freedom associated with the provision of multiple connections may be exploited in an optimum manner. Although the resulting increase in the number of potential paths from a solar component to the transfer point increases the complexity of the optimization process to be executed subsequently, the heuristic selection of preferred paths may result in a converse reduction in this complexity, thereby permitting optimization to be executed with an acceptable workload. 
         [0014]    In one embodiment, the edges of all paths are routed either in a first direction or in a second direction. These two directions are arranged at right angles to each other, and the directions run parallel to the edges of the quadrilateral solar components. The observation of these and other cable routing regulations generates a sustainable improvement in the serviceability of the unit. This restriction may also simplify the issue of cable routing. For the selection of preferred paths, various principles are available, which may be applied either individually or in combination. 
         [0015]    In one embodiment, the preferred paths are determined as the shortest path in relation to the predetermined edge weights of edges on the path. This allows Dijkstra&#39;s algorithm, or one of the further developments and variants thereof, to be applied for the determination of a shortest path in the cabling chart. 
         [0016]    Edge weights may be determined based on a Euclidian distance in respect of their end points or end nodes. By this method, a short cable length between a solar component and the transfer point may be achieved in a straightforward and easily determined manner. 
         [0017]    In one variant, in which the edges, as described above, are routed either in a first or in a second direction, the edge weights may additionally be determined based on edge lengths arranged in the first direction. By this method, for example, a north-south orientation of edges may be assigned a stronger value. 
         [0018]    In one embodiment, the edges oriented in the second direction may also be determined, rather than the edges oriented in the first direction. By this method, for example, an east-west orientation of edges may be assigned a stronger value. The edges oriented in both directions may also be evaluated, in order to achieve a realistic dimension for the length of cable between the solar components and the transfer point. 
         [0019]    The heuristics specified above may be applied in combination with an additional penalty for edge weights, where an edge lies within a specific area that borders the unit. In the case of multiple and adjoining units, the mutual influence of units associated with cables or cable ducts may therefore be excluded or prevented. However, such a cable routing may be permitted, if the resulting benefit is sufficiently great. 
         [0020]    In one embodiment, the selection of heuristically selected paths is achieved via mixed-integer optimization. Standard solutions are available for mixed-integer optimization, which run on conventional processing devices and are easily adapted to the issue under consideration. Mixed-integer optimization permits the execution of effective optimization using various methods and devices. 
         [0021]    In one embodiment, selection involves an exact optimization method such as branch-and-bound, the cutting-plane method, or branch-and-cut. An optimum solution may be achieved in each case. Ultimately, although the optimization method may involve a heavier workload than a pure optimization method only, this additional workload is acceptable, on the grounds that the fundamental sampling volume selected based on the the above-mentioned heuristic is sufficiently small. 
         [0022]    A computer program product according to one aspect of the disclosure incorporates program code for the execution of the methods described. The computer program product includes one or more non-transitory computer-readable storage media having stored thereon instructions executable by one or more processors of a computing system. Execution of the instructions causes the computing system to perform operations corresponding with the acts of the method described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  shows a schematic representation of a photovoltaic installation. 
           [0024]      FIG. 2  shows different forms of representation of a unit in the photovoltaic installation represented in  FIG. 1 . 
           [0025]      FIG. 3  shows a cabling chart for the photovoltaic installation represented in  FIG. 1 . 
           [0026]      FIG. 4  shows a flowchart representing a method for the determination of a cabling of a unit in the photovoltaic installation represented in  FIG. 1 . 
           [0027]      FIG. 5  shows various exemplary results of the method represented in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  shows a schematic representation of a photovoltaic installation  100 . On an available plot  105 , units  110  are arranged, each of which includes a number of solar components  115 . In the interests of clarity, only three units  110 , each of which includes six solar components  115 , are represented by way of an example. Each unit  110  is also associated with a transfer point  120 . 
         [0029]    In one form of embodiment, each solar component  115  includes one or more solar modules, each of which includes a manageable unit of solar cells, which are customarily arranged in a frame and are protected by a glazed cover panel. However, a solar component may also include a number of solar cells within a solar module or a number of solar modules. The function of the transfer point  120  is the hierarchical cascading of the units  110 . All the solar components  115  in a unit  110  are connected by cables  125  to the transfer point  120 . The transfer point  120  may be equipped with an electrical component for the conversion of the electrical energy generated by the unit  110 , for example an inverter. Cabling for the interconnection of the transfer points  120  and the connection of further electrical components in the photovoltaic installation  100  is not represented in  FIG. 1 . 
         [0030]    The photovoltaic installation  100  may include several tens, several hundred, or even several thousand units  110 . For the planning of the photovoltaic installation  100 , a number of different variants are run through, which are evaluated based on their technical properties and their associated construction and operating costs. In one phase, which will not be considered in greater detail here, the plot  105 , the location of the solar components  115 , the grouping thereof in units  110  and the location of the transfer points  120  are defined. Thereafter, the most advantageous cabling between the solar components  115  and the transfer points  120  for each unit  110  of the photovoltaic installation  100  is identified. In order to permit the run-through of different planning scenarios, the optimum routing of the cable  125  in each unit  110  is determined in the most efficient manner possible. 
         [0031]      FIG. 2  shows different forms of representation of a unit  110  in the photovoltaic installation  100  represented in  FIG. 1 .  FIG. 2A  shows a schematic representation of an exemplary unit  110 . Each solar component  115  is provided with two connections  205 , which may be used alternatively for the connection of the solar components  115  to the transfer point  120  by a cable  125 . The relative arrangement of the connections  205  on each solar component  115  is generally uniform and, in the example represented, the connections  205  are arranged opposite each other. 
         [0032]    For the routing of the cable  125  within the unit  110 , rules are provided. In the example represented, a first rule provides that the cable  125  is not to be routed below the solar components  115 , but only outside the perimeter of the latter. Moreover, sections of the cable  125  are to be consistently routed in parallel to a first direction  210  or a second direction  215 , the directions  210  and  215  being linearly independent. For example, the first direction  210  may follow a north-south orientation, and the second direction  215  may follow an east-west orientation. It may also be provided that the solar components  115 , with respect to their connections  205 , are to be oriented in the same direction, either all in the first direction  210 , as represented, or all in the second direction  215 . The solar components  115  are arranged with a specific clearance above the ground surface, in the interest of serviceability and the provision of sufficient mobility for the solar components  115  or units  110 , where provision is made for the tracking of the position of the sun. From the connections  205 , a cable  125  is routed vertically downwards to an embedded cable duct  220 , which may accommodate one or more cables  125 . As the provision of cable ducts  220  is associated with high costs, it is endeavored that the length of the cable ducts  220  is minimized to the greatest possible extent. In the interests of the minimization of line losses and cable costs, the cable  125  between each solar component  115  and the transfer point  120  is as short as possible. For the orientation of sections of the cable ducts  220 , the above-mentioned rules may be applied. 
         [0033]      FIG. 2B  shows the unit  110  represented in  FIG. 2A , excluding the representation of the connections  205 . In each case, the cable  125  is represented schematically up to the mid-point of the solar components  115 . The initial routing of the cable  125 , either upwards or downwards, indicates which connection  205  is to be used. The representation shown in  FIG. 2B  also forms the basis of that shown in  FIG. 1 . 
         [0034]      FIG. 3  shows a cabling chart  300  for a unit  110  of the photovoltaic installation  100  represented in  FIG. 1 . The dashed lines indicate the lateral boundaries of the solar components  115 . 
         [0035]    From each connection  205  of each unit  110 , one edge  305  runs in each direction permitted by the rules. Each edge  305  is assigned an edge weight  310 , which expresses the workload associated with the routing of the cable along the edge  305 . Each edge  305  runs between two nodes  315 . Between a source node  315  and an end node  315 , a path  320  runs, which incorporates one or more edges  305 . Hereinafter it is assumed that such a path  320  will be present in all cases (the cabling chart  300  is coherent), and only unlooped paths  320  are considered, such that each edge  305  in the cabling chart  300  occurs in one path  320  on no more than one occasion. 
         [0036]    The transfer point  120  and the connections  205  respectively form the end nodes  315  of a path  320  which, in each case, represents a cable  125  or a cable duct  220 . By known graph theory methods, a path  320  may be determined from the plurality of edges  305  for each solar component  115  that permits efficient cable routing between the solar component  115  and the transfer point  120 . Accordingly, the quality of cable routing is determined with reference to the edge weights  310 . 
         [0037]    One edge  305  may be employed in a number of paths  320 . This is also useful, on the grounds that a cable duct  220  routed along this edge  305  may be employed for a number of cables  125 . This multiple employment may give rise to more “good” paths  320  than may be identified by the consideration of each path  320  in isolation. On the grounds of this mutual interaction, for the purposes of an exhaustive analysis of all the relevant paths  320 , a substantial plurality of combinations of edges  305  are constituted and evaluated. By nature, this is an NP-incomplete problem, the resolution of which involves the application of a deterministic mechanism rather than polynomial processing capacity. According to one aspect, from the plurality of potential paths  320 , a heuristic is initially applied for the selection of those that are promising and that, from the paths  320  thus selected, an optimization method is then applied for the selection of those which are to be included in an optimized solution. 
         [0038]      FIG. 4  shows a flowchart representing a method  400  for the determination of a cabling of a unit  110  in the photovoltaic installation  100  represented in  FIG. 1 . The method  400  may be executed for each of the units  110  in the photovoltaic installation  100 . The method  400  is designed to run on a programmable computer. 
         [0039]    In a first act  405 , positions of the solar components  405  are recorded. In one act  410 , positions of the connections  205  and of the transfer point  120  are recorded. In one act  415 , rules for cable routing are recorded, in accordance with the exemplary rules described above with reference to  FIG. 2 . Thereafter, in one act  420 , a cabling chart  300  is generated in accordance with the example shown in  FIG. 3 . 
         [0040]    In the following acts  425  to  470 , which may be executed for each of the solar components  115  in the unit  110 , based on the cabling chart  300  for each solar component  115 , one or more paths  320  between the solar component  115  and the transfer point  120  are selected that, according to a predetermined evaluation, are classified as promising. For each of the methods applied in conjunction with acts  425  to  470 , a promising path  320  of this type may be determined. For each connection between the transfer point  120  and each solar component  115 , one or more preferred paths  320  are determined. To this end, the approach described hereinafter for the determination of preferred paths  320  is purely exemplary and optional. 
         [0041]    In act  425 , the edge weights  310  of the edges  305  are determined based on the Euclidian distances of the points represented by the nodes  315 . The positions from acts  405  and  410  are applied for this purpose. Thereafter, in act  430 , a shortest path  320  between the solar component  115  and the transfer point  120  is determined by the application of Dijkstra&#39;s algorithm, or one of the variations or extensions thereof. This algorithm determines the shortest path  320  between specified nodes  315  in the cabling chart  300 , based on the specified edge weights  310 . 
         [0042]    In act  435 , the edge weights applied in act  425  are adjusted to the effect that, for each edge  305 , the distance from the latter to the transfer point  120  in the first direction  210  is considered in addition. The subsequent determination of a shortest path  320  based on these edge weights in act  440  proceeds in accordance with act  430 . 
         [0043]    In a similar manner, act  445  involves the adjustment of the edge weights from act  425  to incorporate the distances from the edges  305  to the transfer point  120  in the second direction  215 . The determination of the shortest path  320  in act  450  corresponds to that described in acts  430  or  440 . 
         [0044]    In act  455 , the adjustments from both act  435  and from act  445  are applied to the edge weights from act  425 . In act  460 , in the manner described, a shortest path  320  is then determined based on the combined edge weights  310 . 
         [0045]    In act  465 , the edge weights  310  determined in one of the previous acts  425  to  460  are adjusted by the application of an additional penalizing term (malus) to those edges  305  that lie in the vicinity of an adjoining unit  110 . In act  470 , a shortest path  320  is again determined by the application of Dijkstra&#39;s algorithm. 
         [0046]    In a concluding act  475 , for each solar component  115 , the number of paths  320  available for the routing of a cable  125  is at least equal to the number of heuristics applied in acts  425  to  470 . In one embodiment, from the quantity of paths  320  determined, duplicates and equivalents may be discarded. Thereafter, optimization is undertaken for the determination of one path  320  for each solar component  115 , based on the quantity of edges  305  determined. This optimization may be executed using linear integer optimization or mixed-integer programming. To this end, an exact solution method, such as branch-and-bound, the cutting-plane method, or branch-and-cut, or any other heuristic may be applied for the execution of non-exhaustive optimization. In the latter case, optimization may be interrupted after a specified time, such that at least a partially optimized solution is achieved. For each solar component  115  in the unit  110 , the solution determined includes one path  320  from one connection  205  on the solar component  115  to the transfer point  120 , in accordance with cable routing regulations. 
         [0047]    For the evaluation of the quality of a given combination of paths  320  during the optimization process in act  475 , different metrics may be applied. 
         [0048]      FIG. 5  shows various exemplary results of the method  400  described in  FIG. 4 , with the application of different metrics.  FIG. 5A  shows the result for a minimization of the length of cable ducts  220 .  FIG. 5B  shows one cable route, in which the sum of the lengths of the cable  125  between the solar component  115  and the transfer point  120  has been minimized.  FIG. 5C  shows the result of optimization with respect to both criteria in  FIGS. 5A and 5B . The criteria in  FIGS. 5A and 5B  may be combined in a weighted sum, in which a heavier weighting is applied to that criterion, the optimization of which is to be given higher priority. 
         [0049]    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 may, 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. 
         [0050]    While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications may 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.