Dynamic and Transient study in Mid Voltage networks in relation to Distributed Generations

Dynamic and Transient study in Mid Voltage networks in relation to Distributed Generations

Sokromo, I.S.

Paap, G.C. (mentor)
Wiercx, F. (mentor)

Continuon

Electrical Engineering, Mathematics and Computer Science

2008-10-16

By increasing numbers of distributed generation, that moreover also become larger individually, the need arises for a better picture of the behavior of such generators during transients like short circuits, load changes, synchronizing faults, island operation, phase opposition, etc. In this thesis simulations of short circuits, load changes and synchronizing faults will be carried out in a network with distributed generation by using RTDS. The purpose of this thesis is to find out if a network remains a stable system after a disturbance and what happens with the generators if a disturbance occurs. For an existing power system the interest went out to the private network of Agriport A7 which is owned by the local farmers. Agriport A7 is a modern project for large-scale greenhouse activities and a company for agribusiness. Agriport A7 lies in the north of the Netherlands. The generator units in this network are CHP units (Combined Heat and Power) of approximately 3 to 8 MW. The heat and CO2 produced is used for the plants in the greenhouses. The electricity generated is used for the lighting of the greenhouses. When there is excess of electrical energy or when there is no lighting needed, the electrical energy is delivered to the Dutch grid. For normal operation generators of the farmers in Agriport A7 are connected to the system. Disturbances can take place in the 150 kV distribution grid or in the Agriport network itself. During disturbances it is likely that high currents flow through the system, resulting in protection operating, which can lead to disconnection of one or more generators. This is very unpleasant for the farmers. However, protection is implemented in each power system, because high currents through a power system component during disturbances put high stress on the construction of power system component. The component will be damaged when the stress is larger than the strength of the component. This is also not what the farmers want. Disturbances that will be simulated in this research are three phase short circuits in the 150 kV grid and on different locations in the 20 kV network of Agriport A7. Further more voltage dips in the power system will be simulated. Voltage dips can be caused by short circuits (far) away from the Agriport network. Also disturbances like generator outage, for example when there is an error in the fuel supply for the prime mover, will be simulated and a situation where the load (lighting) at the farmers changes drastically. Also fault synchronizing of a generator will be observed. For each disturbance the behavior of the generators within one farmer and between neighbors farmers are studied. The results show that the Agriport network is strong to withstand voltage dips of 0.4pu, fault synchronizing of one generator and sudden load changes. For a short circuit in the Agriport network the generators get disconnected from the network. This is not always necessary and the system can be improved by changing the protection time settings. For this study, not the whole Agriport network is modeled in the RTDS, but only a part of the network. Based on findings of this network part, conclusions are drawn for the larger network.

distributed generation
dynamic and transient
mid voltage networks

http://resolver.tudelft.nl/uuid:774bf8c6-8ded-4a98-9b6a-77454262a548

TU Delft, Electrical Engineering, Mathematics and Computer Science, Electrical Power Engineering

Student theses

master thesis

(c) 2008 I.S. Sokromo