Method and arrangement for determining measurement locations in an energy grid

Abstract

A method determines measurement locations in an energy grid. In the energy grid, use is made of a controllable device for wide-range voltage control. A model of the energy grid is provided which specifies a voltage distribution within the energy grid by a system of equations and/or a system of inequalities depending on the control position of the controllable device. A simulation for minimizing the number of measurement locations is carried out on the basis of the model, and in that as a result of the simulation a minimum number and the respective position of measurement locations and also the control position of the controllable device are specified in order that the energy grid complies with a predefined voltage band during operation.

Claims

1. A method for determining measurement locations in an energy grid having a heterogeneous energy generator and an energy consumer structure, wherein in the energy grid use is made of a controllable device for wide-range voltage control, which comprises the steps of: providing a model of the energy grid specifying a voltage distribution within the energy grid by means of at least one of a system of equations or a system of inequalities depending on a control position of the controllable device; carrying out a simulation for minimizing a number of the measurement locations on a basis of the model, and as a result of the simulation a minimum number and a respective position of the measurement locations and also the control position of the controllable device are specified in order that the energy grid complies with a predefined voltage band during operation, wherein during the simulation for all control positions of the controllable device and in each case for all nodes in the energy grid, the following steps are repeated: cancelling a condition in at least one of the system of equations or the system of inequalities that the predefined voltage band must be complied with, for a respective node; carrying out the simulation; and adding the respective node to a set of the measurement locations required at a minimum, if a result of the simulation reveals that the predefined voltage band was violated at the respective node; and carrying out above steps via a computer.

2. The method according to claim 1, which further comprises installing voltage measuring devices at the respective position of the measurement locations determined in the energy grid.

3. The method according to claim 1, which further comprises setting the controllable device to the control position which requires the minimum number of the measurement locations in accordance with the result.

4. The method according to claim 1, which further comprising providing a controllable substation transformer as the controllable device.

5. The method according to claim 1, which further comprises providing a grid controller as the controllable device.

6. The method according to claim 1, which further comprises providing a controllable local grid transformer as the controllable device.

7. A configuration for determining measurement locations in an energy grid, wherein in the energy grid use can be made of a controllable device for wide-range voltage control, the configuration comprising: a computer configured for providing a model of the energy grid, wherein the model specifies a voltage distribution within the energy grid by means of at least one of a system of equations or a system of inequalities depending on a control position of the controllable device, and a simulation for minimizing a number of the measurement locations is carried out on a basis of the model, and said computer specifying as a result of the simulation a minimum number and a respective position of the measurement locations and also the control position of the controllable device in order that a predefined voltage band can be complied with for the energy grid during operation, wherein during the simulation for all control positions of the controllable device and in each case for all nodes in the energy grid, the following steps are repeated: cancelling a condition in at least one of the system of equations or the system of inequalities that the predefined voltage band must be complied with, for a respective node; carrying out the simulation; and adding the respective node to a set of the measurement locations required at a minimum, if a result of the simulation reveals that the predefined voltage band was violated at the respective node.

8. A configuration, comprising: a controllable device; an energy grid having nodes, wherein in said energy grid use can be made of said controllable device for wide-range voltage control; a computer configured for providing a model of said energy grid, wherein the model specifies a voltage distribution within said energy grid by means of at least one of a system of equations or a system of inequalities depending on a control position of said controllable device, and a simulation for minimizing a number of measurement locations is carried out on a basis of the model, and said computer specifying as a result of the simulation a minimum number and a respective position of the measurement locations and also the control position of said controllable device in order that a predefined voltage band can be complied with for said energy grid during operation, wherein during the simulation for all control positions of said controllable device and in each case for all said nodes in said energy grid, the following steps are repeated: cancelling a condition in at least one of the system of equations or the system of inequalities that the predefined voltage band must be complied with, for a respective node; carrying out the simulation; and adding said respective node to a set of the measurement locations required at a minimum, if a result of the simulation reveals that the predefined voltage band was violated at said respective node; and voltage measuring devices disposed at the respective position of the measurement locations determined in said energy grid.

9. The configuration according to claim 8, wherein said controllable device is set to the control position, the control position requires a minimum number of the measurement locations in accordance with the result.

10. The configuration according to claim 8, wherein said controllable device has a controllable substation transformer.

11. The configuration according to claim 8, wherein said controllable device has a grid controller.

12. The configuration according to claim 8, wherein said controllable device has a controllable local grid transformer.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is an illustration showing an example of an energy grid; and

(2) FIG. 2 is an illustration showing an overview of measurement locations evaluated by a method according to the invention in the energy grid in accordance with FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown an example of an energy grid with a medium-voltage source 1 (a grid connection) and a low-voltage transformer 3, which is controllable in stages from −8% to +8% of the nominal voltage of a low-voltage level 4U a simulation device 70, and a further controllable device 71.

(4) The exemplary grid has nodes N at which e.g. outgoing sections—marked by arrows—as loads and feeding devices 11 for electrical energy, which are represented by solar modules, are present.

(5) The illustration shows six grid branches 5, 6, 7, 8, 9, 10 having different characteristic loadings.

(6) Grid branch 5: Outgoing section having heterogeneous composition of generation and consumption.

(7) Grid branch 6: Outgoing section having heterogeneous composition of generation and consumption.

(8) Grid branch 7: Outgoing section having homogeneous loading.

(9) Grid branch 8: Outgoing section having homogeneous feeding.

(10) Grid branch 9: Outgoing section having small homogeneous loading.

(11) Grid branch 10: Outgoing section having small homogeneous generation.

(12) The voltage measurement locations 12 determined by means of the optimization are marked by nodes depicted with greater thickness in the grid plan. These are the nodes N28, N40, N57, N59, N46, N50.

(13) For the grid branches 9 and 10, therefore, the application of the optimization yields no required measurement locations, since here evidently the voltage conditions cannot be violated owing to the smallness of the connected loads and generators and the nodes in these branches can be monitored implicitly by observation of nodes in the other branches.

(14) In the case of the grid branches 7 and 8, owing to the homogeneity of the connected loads and feeding arrangements, the monitoring of the respective last grid node in the path section suffices also for monitoring all other grid nodes of the path section.

(15) In the case of the grid branches 5 and 6 the situation is somewhat more difficult: the sizes of the load and generator symbols represent the magnitude of the respective currents. In this regard, in the grid branch 6 it can happen that the node N59 must be observed on account of the voltage rise. By contrast, the node N57 may have the lowest node voltage if low load and high feeding occur simultaneously at the node N59. Consequently, the voltage must be monitored at this node as well.

(16) The opposite situation prevails in the grid branch 5: here the node N40 must be monitored on account of the load. However, the case may also occur where, with predominant load at N40 and predominant feeding at N28, the upper voltage limit is exceeded, such that this node must likewise be monitored.

(17) FIG. 2 illustrates an overview of the measurement locations evaluated by the method according to the invention in the energy grid in accordance with FIG. 1. On the horizontal axis, a respective vertical line is imagined for the nodes N. The vertical axis indicates, for each control position R of the substation transformer, by how many percent the nominal voltage was decreased or increased. In this case, for each stage (percentage deviation R) a horizontal line is imagined along which arises a grid of crossing points which can be either implicitly or explicitly observable. Explicitly observable load voltages are present if a crossing point is marked by a dot. These nodes must be monitored by measurement locations. The fewer dots there are on a horizontal line, the fewer measurement locations are thus required.

(18) If the controllable device such as e.g. a controllable substation transformer is operated with a neutral tap position, that is to say a deviation of R=0% from the nominal current, then this results in the six measurement locations N28, N40, N57, N59, N46, N50 already depicted in FIG. 1.

(19) The overview shows that in the case of a set stage in the substation transformer of −1% to −4%, only four measurement locations must be observed by measuring devices, namely N28, N40, N50 and N57. In the exemplary grid it would thus be optimal to set the substation transformer from −1% to −4%. By virtue of saving two measurement locations in the exemplary grid, it is possible to save corresponding costs for installation, maintenance and monitoring.

(20) The different character of the grid nodes N46 and N50 is shown clearly here: On account of the load character of N46 no measurement is required at relatively high voltage setpoint values (negative control stages), while in the outgoing section N50, characterized by generators, monitoring is necessary precisely in such cases. Consequently, a total of 6 nodes must be monitored if the intention is to pass through a control range of 94% to 106% (−6% to 6%). The minimum number of four measurement locations is required in the case of a voltage control range of 101% to 104%.

(21) If appropriate, in the context of feeding management, it is necessary to limit feeders in the path sections of the nodes N28, N46, N50 and N59 if the upper limit values are reached in these path sections.

(22) Further dynamic voltage control devices such as controllable local grid transformers (CLGT) can be taken into account approximately by virtue of the fact that, for all nodes in the region in proximity to these elements, not only is the voltage condition relinquished, but also the penalization term is set to zero. This corresponds to the assumption that the control device can fulfill the control task to the greatest possible extent independently of the tap switch position in the substation.

(23) The equations underlying the solution according to the invention are listed below. In this case, the numbering of the equations corresponds to the numbering in the description above.

(24) Equations:

(25) $\begin{array}{cc}\begin{array}{c}{\underset{\_}{i}}_{G,i}-{\underset{\_}{i}}_{L,i}=\left(u_{w,i}+j{u}_{b,i}\right)\left(g_{i,i}+{\mathrm{jb}}_{i,i}\right)+\\ \underset{j\ne i}{.Math.}\left(g_{i,i}+{\mathrm{jb}}_{i,i}\right)\left(u_{w,j}+{\mathrm{ju}}_{b,j}\right)\\ =u_{w,i}{g}_{i,i}-u_{b,i}{b}_{i,i}+j\left(u_{b,i}{g}_{i,i}+u_{w,i}{b}_{i,i}\right)-\left(2\right)\\ \underset{j\ne i}{.Math.}\left(\left(g_{i,j}{u}_{w,j}-b_{i,j}{u}_{b,j}\right)+j\left(b_{i,j}{u}_{w,j}+g_{i,j}{u}_{b,j}\right)\right)\\ =u_{w,i}{g}_{i,i}-u_{b,i}{b}_{i,i}+\underset{j\ne i}{.Math.}\left(g_{i,j}{u}_{w,j}-b_{i,j}{u}_{b,j}\right)+\left(3\right)\\ j\left(u_{b,i}{g}_{i,i}+u_{w,i}{b}_{i,i}\right)+\underset{j\ne i}{.Math.}j\left(b_{i,j}{u}_{w,j}+g_{i,j}{u}_{b,j}\right)\end{array}& \left(1\right))\\ i_{w,G,i}-i_{w,L,i}=u_{w,i}{g}_{i,i}-u_{b,i}{b}_{i,i}+\underset{j\ne i}{.Math.}j\left(g_{i,j}{u}_{w,j}-b_{i,j}{u}_{b,j}\right)& \left(4\right)\\ i_{b,G,i}-i_{b,L,i}=u_{b,i}{g}_{i,i}-u_{w,i}{b}_{i,i}+\underset{j\ne i}{.Math.}j\left(b_{i,j}{u}_{w,j}-g_{i,j}{u}_{b,j}\right)& \left(5\right)\\ \begin{array}{c}.Math.u_{w,i}+{\mathrm{ju}}_{b,i}.Math.=\sqrt{u_{w,i}^2+u_{b,i}^2}\\ =f\left(u_{w,i},u_{b,i}\right)\left(7\right)\\ =\sqrt{u_{w,i,o}^2+u_{b,i,o}^2}+\frac{\delta f}{\delta u_{w,i}}{\mathrm{du}}_{w,i}+\frac{\delta f}{\delta u_{b,i}}{\mathrm{du}}_{b,i}\left(8\right)\\ =\frac{\begin{array}{c}\sqrt{u_{w,i,o}^2+u_{b,i,o}^2}+\\ u_{w,i,o}\end{array}}{\sqrt{u_{w,i,o}^2+u_{b,i,o}^2}}\left(u_{w,i}+u_{w,i,0}\right)+\left(9\right)\\ \frac{u_{b,i,o}}{\sqrt{u_{w,i,o}^2+u_{b,i,o}^2}}\left(u_{b,i}-u_{b,i,0}\right)\end{array}& \left(6\right)\\ {\underset{\_}{i}}_{j,\mathrm{maxLoad}}\le {\underset{\_}{i}}_j\le 0& \left(10\right)\\ 0\le {\underset{\_}{i}}_j\le {\underset{\_}{i}}_j,\max \mathrm{generation}& \left(11\right)\\ 90\le .Math.{\underset{\_}{u}}_i.Math.\le 110& \left(12\right)\\ p_i=\{\begin{array}{cc}1& \mathrm{for}.Math.{\underset{\_}{u}}_i.Math.\le 90+ϵ\\ 1& .Math.{\underset{\_}{u}}_i.Math.\ge 110+ϵ\\ 0& \mathrm{otherwise}\end{array}& \left(13\right)\\ O_{\min }=\mathrm{Min}\underset{i}{.Math.}{p}_i& \left(14\right)\\ O_{\max }=\mathrm{Max}\underset{i}{.Math.}{p}_i& \left(15\right)\end{array}$