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Smart Grid Automation System


At the In­sti­tute ie3, a new kind of smart grid automation system is developed. This system is meant to be installed in the medium voltage level and the developed functionalities are used to protect and control the medium and low voltage grid levels. The general overview is given in the picture below.

The devices of the smart grid automation system can be located at the local substations. The local devices monitor the local grid status in the low voltage grid and, if necessary, intervene with control measures. In addition, the measured values on the medium voltage side are transmitted to a central system, typically located at the primary substation, with which the network status in the medium voltage is determined. There, too, measures can be taken if necessary to correct the grid state.

Schematic view of the smart grid automation system © ie3

Functionalities

In the smart grid automation system, different functionalities are already implemented. More functionalities are continuously developed. Therefore, the following list makes no claim to completeness.

Consistent engineering, configuration and test process

For the engineering and automatic configuration of the system, a well-defined engineering toolchain based on data models according to IEC 61850-6 (Substation Configuration description Language, SCL) and IEC 61970-301 (Common Information Models, CIM) is available. Together with the functional modularity, this enables a flexible and fast adaptation of the system to changing requirements within the grid. In­no­va­tive application-oriented test procedures are available to verify the proper operation of configured systems and their functions as a whole.

Measurement and data com­mu­ni­cation

The system can measure up to five outgoing branches on the medium voltage level. The three-phase currents of the outgoing branches and the busbar voltage on medium voltage level are measured. For the measurements in the low voltage level, smart measurement devices are connected via Modbus RTU, which provide three-phase RMS current and voltage values for up to 16 branches at the low voltage busbar. The inter-system com­mu­ni­cation is realized via IEC 61850 MMS. The connection to the control center can be established via IEC 61850 MMS or IEC 60870-5-104.

Protection

The developed system provides automation function as well as protection and control functions. The included protection functions are over current protection and distance protection. The implementation of differential protection is in progress. Furthermore, fault direction detection algorithms (both for short circuit fault and earth fault) are being included. In the fu­ture, automatic fault clearance and power restoration will be possible, when suitable switchgear will be available.

State Estimation

The algorithm for network state estimation requires decentrally collected measurement values for the calculation of the network state. Using network equations, systems of equations are set up and solved to determine the network state. In contrast to the simple power flow calculation, additional methods are used in state estimation to reduce the influence of equally distributed measurement errors on the determined network state and improve the estimate's quality. The most widely used algorithm for optimizing the estimation quality is the weighted least squares (WLS) method, which is also used to estimate the network state in this case.

(Robust) Voltage Control

The implemented voltage regulation algorithm follows a centralized regulator approach. A prerequisite for such a voltage control is that the controller receives measured values from the measuring devices distributed in the network at specific intervals. For the com­mu­ni­cation of the values between the devices, a master-slave com­mu­ni­cation was used.

Although the central controller approach functions well, it places a high demand on the master's reliability and com­mu­ni­cation. For example, if com­mu­ni­cation with the master fails, the entire system goes into a critical operating state. For this reason, a new robust method for voltage regulation has been introduced. This implementation inserts a submaster between master and slave. The idea of such an implementation is that each branch has its own submaster and the slaves communicate only with the submaster.

Optimal Power Flow

The Optimal Power Flow (OPF) algorithm is well known in the field of optimized use of power plants for calculating minimum feed-in power to cover the entire load in the grid. In the area of Smart Grids, further use cases can be considered such as the avoidance of voltage violations and line overloads. Within the scope of re­search works, an OPF algorithm was developed which detects limit violations in medium-voltage grids based on estimated voltages from a state estimation and successful resolve them by optimal controlling of flexibilities such as renewable plants or controllable loads.

Model Predictive Control

The Model Predictive Control (MPC) Algorithm is specifically used in processes engineering such as power plant or rolling mill processes and has the outstanding property of considering technical boundary conditions. Optimal control commands will be set by taking fu­ture system states within a prediction horizon into account. For the Smart Grid Automation System, a linear MPC algorithm was developed which is able to control currents and voltages of an entire grid and under consideration of fu­ture system loads. The verification of the MPC has shown that it always has a special advantage when activation times or charge states of flexibilities have to be considered.

Calculation-supporting methods

In addition to the grid operation algorithms, Calculation-supporting methods (CSM) are necessary that either support them or provide the basis for the calculation. The focus is on processes that automatically recognize the correct grid topology and thus keep the input data of the state estimation up-to-date. A further focus is the reduction of the complexity of grids in cases of an insufficient measurement topology. For this purpose methods are used which carry out and continuously update an adaptive grid reduction while guaranteeing a high estimation quality of the state estimation.


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Location & approach

The campus of TU Dort­mund Uni­ver­sity is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dort­mund-Eichlinghofen" (closer to Cam­pus Süd), and from B 1 / A 40 "Dort­mund-Dorstfeld" (closer to Cam­pus Nord). Signs for the uni­ver­si­ty are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

To get from Cam­pus Nord to Cam­pus Süd by car, there is the connection via Vo­gel­pothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Cam­pus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

TU Dort­mund Uni­ver­sity has its own train station ("Dort­mund Uni­ver­si­tät"). From there, suburban trains (S-Bahn) leave for Dort­mund main station ("Dort­mund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The uni­ver­si­ty is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duis­burg.

You can also take the bus or subway train from Dort­mund city to the uni­ver­si­ty: From Dort­mund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dort­mund Uni­ver­sity leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop "Dort­mund Kampstraße". From there, take U43 or U44 to the stop "Dort­mund Wittener Straße". Switch to bus line 447 and get off at "Dort­mund Uni­ver­si­tät S".

The AirportExpress is a fast and convenient means of transport from Dort­mund Airport (DTM) to Dort­mund Central Station, taking you there in little more than 20 minutes. From Dort­mund Central Station, you can continue to the uni­ver­si­ty campus by interurban railway (S-Bahn). A larger range of in­ter­na­tio­nal flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the uni­ver­si­ty station.

The H-Bahn is one of the hallmarks of TU Dort­mund Uni­ver­sity. There are two stations on Cam­pus Nord. One ("Dort­mund Uni­ver­si­tät S") is directly located at the suburban train stop, which connects the uni­ver­si­ty directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Cam­pus Süd) Eichlinghofen. The other station is located at the dining hall at Cam­pus Nord and offers a direct connection to Cam­pus Süd every five minutes.

The facilities of TU Dort­mund Uni­ver­sity are spread over two campuses, the larger Cam­pus North and the smaller Cam­pus South. Additionally, some areas of the uni­ver­si­ty are located in the adjacent "Technologiepark".

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