Method for operating an electrical energy supply network, and control device for controlling devices of an electrical distribution network

Abstract

For providing system services reliably for an energy supply network, measured values indicating an electrical state of the supply network and/or of a distribution network are recorded. A deviation of the operational state of the supply network from a required operational state is determined and control measures are defined for restoring the required operational state. Control data which indicate a part of the control measures to be carried out by devices of the distribution network are transmitted to the control device, and control commands are determined for the devices of the distribution network with which the devices are controlled such that the distribution network carries out the required control measures. Estimated control data are defined and the communication connection to a network controller is monitored. In the event of a fault in the communication connection, the control commands are defined using the estimated control data instead of the control data.

Claims

1. A method for operating an electrical energy supply network connected to a connection station having a lower-level distribution network, an operation of the electrical energy supply network is controlled by means of a network controller, which method comprises the following steps of: recording measured values indicating an electrical state of the electrical energy supply network and/or the lower-level distribution network at the connection station with a local controller of the lower-level distribution network; determining a deviation of a current operational state of the electrical energy supply network from a required operational state and defining control measures which are suitable for restoring the required operational state with the network controller; transmitting control data from the network controller to the local controller, the control data indicating at least a part of the control measures which are intended to be carried out by devices of the lower-level distribution network; determining control commands for at least one device of the lower-level distribution network by means of the local controller using the control data received, wherein the control commands are suitable for controlling the devices in such a way that the lower-level distribution network carries out a required part of the control measures in relation to the electrical energy supply network; defining estimated control data by means of the local controller using the measured values, the estimated control data being defined by a self-learning system; monitoring a communication connection between the local controller and the network controller; and determining the control commands using the estimated control data instead of the control data received in an event of a fault in the communication connection.

2. The method according to claim 1, which further comprises selecting the measured values from the group of measured quantities consisting of an AC electric current, AC electric voltage, a frequency of the AC electric current, a temperature, solar radiation and wind strength.

3. The method according to claim 1, which further comprises using training data which contains pairs of the measured values and associated parts of the control data received to train a behavior of the self-learning system.

4. The method according to claim 3, which further comprises carrying out a training of the self-learning system by the local controller.

5. The method according to claim 3, which further comprises: transmitting the training data to an external data processing device for training the self-learning system; and generating system parameters with the external data processing device in a learning process, the system parameters being transmitted to the self-learning system following a learning process and being adopted by the self-learning system.

6. The method according to claim 3, which further comprises comparing the control data received with the estimated control data by means of the local controller and in an event of an unacceptable difference, a behavior of the self-learning system is retrained.

7. The method according to claim 1, which further comprises transmitting the measured values from the local controller to the network control system of the electrical energy supply network.

8. The method according to claim 1, which further comprises recording a frequency of a current on an energy supply network side of the connection station by means of the local controller; and wherein in the event of the fault in the communication connection, fixed, predefined control data are used instead of the estimated control data if the frequency lies outside a predefined frequency band.

9. The method according to claim 8, wherein: in a case of the frequency lying above the predefined frequency band, the predefined control data effect control commands which cause an increase in an active power consumption by the lower-level distribution network; and in a case of the frequency lying below the predefined frequency band, the predefined control data effect the control commands which cause a reduction in the active power consumption by the lower-level distribution network.

10. A local controller for controlling devices of an electrical distribution network, the local controller comprising: a measured value recording device to record measured values; a communication device to receive control data from a network controller of an energy supply network at a higher level than the electrical distribution network, wherein the control data indicate at least a part of control measures which are intended to be carried out by devices of the electrical distribution network; a controller for determining control commands for at least one of the devices of the electrical distribution network using the control data received, wherein the control commands are suitable for controlling the devices in such a way that the electrical distribution network carries out the control measures; an estimation device for defining estimated control data using the measured values, said estimation device having a self-learning system for deriving the estimated control data; a monitor for monitoring a communication connection between said communication device and the network control system; and said controller configured to determine the control commands using the estimated control data instead of the control data received if there is a fault in the communication connection.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a schematic view of an energy supply network to which a distribution network is connected at a connection station according to the invention;

(2) FIG. 2 is a schematic view of a connection station; and

(3) FIG. 3 is a schematic view of a local control device.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown a schematic view of an energy supply network 10, indicated purely by way of example, which may, for example, be a medium-voltage network. The energy supply network is connected at a connection station 11, for example a local network station, to a lower-level distribution network 12. Devices such as consumers, generators, storage devices, but also inverters, inductors and capacitors as well as switching devices and transformers with step switches can be connected to the distribution network.

(5) Along with the distribution network 12, further distribution networks 12a can be connected at connection stations 11a to the energy supply network 10.

(6) The operation of the energy supply network 10 is controlled via a network control system 13. This serves, in particular, to maintain the operational state of the energy supply network 10 within predefined limits. Such limits may, for example, be voltage and frequency ranges which are adhered to during the operation of the energy supply network. The performance of system services entails adherence to these predefined limits. Measures for carrying out the system services are, for example, the feed-in or removal of active and/or reactive power in order to influence the voltage and/or frequency of the energy supply network.

(7) An increasing number of active devices (PV installations, wind power installations, storage devices, etc.) in the distribution networks increases the need to provide system services of this type at least partially in the distribution network also and therefore to contribute to the stability of the operation of the energy supply network and the distribution network.

(8) For this purpose, inter alia, a local control device 14 is present at the connection station 11. The local control device 14 ensures in a manner described in detail below that the required system services are provided by the distribution network.

(9) Corresponding local control devices 14a are also provided at the further connection stations 11a.

(10) The operational state of the energy supply network 10 is monitored with the network control system 13. If changes from a predefined operational state occur, e.g. a modification of the frequency or the voltage in the energy supply network, control measures which are suitable for restoring the required operational state of the energy supply network are determined by the network control system. The network control system normally performs complex load flow calculations for this purpose. In the event of a detected voltage deviation, for example, such control measures can indicate a value of the reactive power which is to be fed into the energy supply network 10 in order to readjust the voltage to the setpoint value.

(11) The network control system 13 furthermore defines a part of the control measures which is to be carried out by the distribution network 12. This system service requirement is transmitted in the form of control data SD from the network control system via a communication connection 15 to the local control device 14 (and, where appropriate, the further control devices 14a). Control commands SB are determined by means of the local control device 14 using the received control data SD and are forwarded to at least one of the devices of the distribution network, e.g. via a Power Line Communication. These control commands SB cause the corresponding unit to modify its operational state in such a way that at least a part of the control measures required by the control data SD is carried out. An inverter, for example, can be controlled in such a way that it feeds a specific quantity of reactive power into the distribution network 12.

(12) As a result of the execution of all control commands SB transmitted to the devices of the distribution network, the distribution network carries out the control measures required by the energy supply network 10 at the connection station 11 in order to perform the system service.

(13) This procedure is shown in detail in FIG. 2 for a connection station 11. Measured values of measured quantities, such as e.g. electric currents I.sub.1, I.sub.2, I.sub.3 and voltages U.sub.1, U.sub.2, U.sub.3 and also the frequency f, are recorded with the local control device 14 at different measuring points in the vicinity of the connection station, e.g. with sensors of the local network station. Along with electrical measured quantities, measured quantities which indicate the weather in the vicinity of the connection station 11, e.g. ambient temperature, solar radiation, wind strength, and which can have an influence on renewable energy generators present in the distribution network 12 can also be recorded. These measured values M can be transmitted to the network control system 13 so that the local control device acts in this respect as a merging unit, remote terminal unit or data concentrator.

(14) The network control system 13 transmits the control data SD with the control measures for performing the required system services to the local control device 14. Control commands SB are generated by the local control device 14 on the basis of the received control data SD and are forwarded to actuators 20 with which the devices of the distribution network 12 are controlled.

(15) FIG. 3 shows a detailed view of a local control device 14. The local control device 14 contains a measured value recording device 30 with which measured values for current I, voltage U, frequency f and temperature T, solar radiation and wind strength v can be recorded. The local control device 14 furthermore has a communication device 32 which is connected via a communication connection 15 to the network control system 13 and via which, on the one hand, measured values M can be transmitted to the network control system 13 and, on the other hand, control data SD can be received from the network control system 13.

(16) The local control device 14 furthermore has a control unit 33, e.g. a microprocessor or a processing module with hardware-programmed control (e.g. FPGA, ASIC) which is connected to a storage device 34. An output interface 35 for emitting control commands SB to actuators which can have a controlling effect on the devices of the distribution network is furthermore provided. Finally, the control device 14 also has an estimation device 36 with a self-learning system 37 in the form of an artificial neural network.

(17) The local control device 14 operates as follows: During the ongoing operation of the distribution network, the control device 14 records measured values of at least one of the above-mentioned measured quantities via the measured value recording device 30. These may, for example, be electrical engineering measured quantities on the overvoltage and undervoltage side of a transformer in the connection station (cf. e.g. FIG. 2), for example current, voltage (in each case three-phase) and frequency. Alternatively or additionally, exogenous measured quantities such as temperature, solar radiation and wind speed can also be recorded either through direct local measurements or through an interface to a central IT service in order to receive either measured values or forecasts there. The measured values are stored in the storage device 34. They can be retrieved from there by means of the control unit 33 and can be transmitted via the communication device 32 to the network control system 13. This can be done cyclically or spontaneously. The measured values can be transmitted as raw data or after a preprocessing to the network control system. In this respect, the control device 14 performs the function of a merging unit, a remote terminal unit or a data concentrator.

(18) During the operation of the energy supply network, the network control system defines control measures, i.e. requirements for system services which are intended to be provided via the distribution network, and transmits them in the form of control data to the local control device 14. They are received there with the communication device 32 and are forwarded to the control unit 33. Control commands which are forwarded to the output interface 35 are generated from the control data with the control unit 33. In this respect, the control device 14 performs the function of indirect control of the distribution network by evaluating requirements of the network control system and forwarding them to the corresponding devices of the distribution network.

(19) The received control data SD are furthermore stored in the storage device 34 so that pairs of measured values and associated control data are present there. Any time delay can be taken into account, since the control data normally represent a response to a previously occurring state of the energy supply network and/or the distribution network, the generation of which takes a certain time. Time slices, for example, can also be formed here, so that a pair consists in each case of a plurality of measured values and control data associated with the common time period and stored in the data storage device. Training datasets are formed in this way for the estimation device 36.

(20) The measured values are furthermore forwarded to the estimation device 36. In parallel with the reception of the control data SD from the network control system 13, the control device 14 defines control data estimated by means of the estimation device 36 from the present measured values. To do this, the estimation device 36 comprises a self-learning system 37, e.g. an artificial neural network, which is trained to establish a relationship between present measured values and the control data received from the network control system. To do this, it makes use of the training datasets stored in the storage device and uses them to train the self-learning system 37. Here, the estimation device 36 learns a relationship between the locally recorded measured values (electrical measured quantities and exogenous variables) and the control data indicating the system services required by the network control system. Alternatively, it can also be provided to allow this training to run in an external data processing device 38, for example in a data processing cloud. On completion of the training phase, the estimation method for defining the estimated control data runs in parallel with the normal operational processes described above. Estimated control data which indicate the expected requirements for system services are generated continuously by the estimation device 36 using the measured values. The control unit 33 continuously compares the control data received from the network control system 13 with the control data estimated by the estimation device. If substantial differences occur, a new training phase is instigated. In this way, the self-learning system 37 of the estimation device 36 is continuously trained to establish the required relationship between the system state indicated by the measured values and the system service requirements resulting therefrom.

(21) During operation, a monitoring device 39 of the control device 14 continuously monitors the communication with the network control system 13. This can be done, for example, through the regular transmission of messages (heartbeat signals) from the network control system 13 to the control device 14. As soon as these messages fail to appear, a communication fault is inferred. Alternatively, it can also be provided that the control device 14 regularly checks whether control data SD of the network control system 13 have been received in a user-parameterizable time period. If not, a communication fault is similarly inferred. As soon as a communication fault has been detected, the control device 14 switches to locally autonomous operation. During the locally autonomous operation, the estimated control data are used by the control unit 33 instead of the control data which are no longer receivable due to the communication fault in order to define the control commands SB. In this respect, the control device 14 performs a direct local control function for the distribution network until the communication with the network control system has been restored.

(22) In addition, the control device 14 can also monitor the frequency on the overvoltage side of the transformer of the connection station in this locally autonomous operating mode in order to detect whether the network is currently in a state of restart following a blackout (complete network outage). If the frequency lies outside a certain range, the control commands are not defined on the basis of the estimated control data but using fixed, predefined control data which have been determined with a heuristic method. The reason for this is that black start situations very rarely occur and therefore no or not enough data are present to train the self-learning system. The heuristics therefore attempt to increase the generation and reduce loads (increase active power feed-in) if the frequency is understepped; if the frequency is exceeded, the generation is reduced and the loads are increased accordingly (reduce active power feed-in).

(23) The control device described offers the following advantages: The control device 14 can organize the system services in the distribution network (local network), even if the communication with the network control system 13 is lost, in order to support the energy supply network (medium-voltage network) in its operational management. Locally autonomous continued operation is possible using the estimation device 36 in the event of a failure in the communication with the network control system 13. The estimation device 36 for the system service requirements requires no models whatsoever of the networks, neither of the energy supply network nor of the connected distribution network. The proposed control device 14 can therefore be put into operation in a very simple manner (plug-and-play) and can be operated efficiently with manageable processing power requirements. As already explained above, the current private communication networks of the network operators normally extend only as far as the substations upstream of the connection stations. The communication gap between the substations and the connection stations (e.g. local network stations) represents an obstacle to an active operational management of the distribution networks which will become increasingly necessary in future. The present control device 14 allows distribution networks to be actively managed even with an unreliable communication connection and thus bridges the gap in the future operational management concepts. It is thus possible to operate the distribution networks at the limits of their operating range without being concerned that the energy supply network will be overloaded or damaged by a lacking system service contribution of the distribution networks in the event of a failure of the communication between the network control system and the control device. The proposed solution can furthermore support the network operator in the reconstruction of the network following a blackout by using the flexibilities of the resources and end customer installations connected in the distribution network to reduce the power imbalances arising with the successive reconstruction of the network.

(24) Although the invention has been illustrated and described in detail above by means of preferred example embodiments, the invention is not limited by the disclosed examples and other variations may be derived herefrom by the person skilled in the art without departing the protective scope of the patent claims set out below.