Abstract
Models of a low voltage distribution network using a typical tertiary-structure solid state transformer (SST) for the integration of distributed generations (DGs) and a conventional low voltage distribution network integrated with DGs were established to study the transient voltage stability issue, using the power system simulation software PSCAD. Effects on the transient voltage stability of the load bus and DC bus in the SST system are analyzed when grid-side cable line faults (such as short circuit and line disconnection) occur or the total output of DGs drops greatly. The results show that, comparing with the conventional system, the SST has apparent advantages on enhancing the transient voltage stability of load bus while facing different disturbances, even though SST has to regulate the voltage passively. Short circuit faults at different location of the grid-side line have different effects on the transient voltage stability, while the effect of disconnection fault is not related to fault location. Moreover, the DC bus voltage is easy to keep climbing continually when short circuit fault of the line occurs that is close to the SST input stage or disconnection fault occurs at any location of the line. If a battery energy storage station is installed, the transient voltage stability of DC bus and load bus will be improved effectively because of the regulation function of battery storage.
Highlights
With the technologies related to new energy generation being maturing day by day and the construction of the energy internet being pushed forward constantly [1,2,3], penetrations of distributed generations (DGs) in the distribution network are increasing gradually [4, 5]
A typical simulation model that a distributed photovoltaic power station is directly integrated into a low voltage distribution network was established in [12], and the effects were analyzed on the transient voltage stability of load bus when the faults such as short circuit and line disconnection occur or the output of distributed photovoltaic power plant drops greatly
It has practical significance to study on the transient voltage stability of the DGs grid-connected system and it is meaningful for realizing the change from a traditional fossil-fuel grid to a future green smart grid
Summary
With the technologies related to new energy generation being maturing day by day and the construction of the energy internet being pushed forward constantly [1,2,3], penetrations of distributed generations (DGs) in the distribution network are increasing gradually [4, 5]. A typical simulation model that a distributed photovoltaic power station is directly integrated into a low voltage distribution network was established in [12], and the effects were analyzed on the transient voltage stability of load bus when the faults such as short circuit and line disconnection occur or the output of distributed photovoltaic power plant drops greatly. In [13], the impacts of large-scale photovoltaic generation on the steady state voltage stability of distribution system were studied, and the conclusion that the photovoltaic modules have to operate in the reactive power support mode to improve the system voltage stability was obtained. A simulation model of a 0.38 kV low voltage distribution network which uses a typical SST for the integration of DGs was established using the power system simulation software PSCAD/EMTDC, and effects on the transient voltage stability of the system while facing various disturbances are studied. The advantages of the transient voltage stability using a SST for the integration of DGs are analyzed, and the differences between whether there is a battery energy storage station are discussed
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