The increasing share of renewable-based electricity generation is having a negative impact on the voltage quality, due to its inherent intermittency. Distribution network operators have to keep the voltage quality within the standards, also with the maximum integration of distributed energy resources (DERs). In active networks, distributed voltage control (DVC) strategies are emerging with the introduction of smart grid technologies that are able to handle voltage fluctuations with the least latency. Moreover, in highly PV penetrated distribution networks, the hosting capacity (HC) enhancement studies, with the active usage of auxiliary equipment like the on-load tap changer (OLTC), grid-tied inverters (GTI), battery energy storage systems (BESS) and their technical-effectiveness, is an emerging topic. The first objective of this thesis is to develop a comprehensive DVC strategy based on the multi-agent system's (MAS) autonomous control capability. Primarily, it comprises a token transversal-based MAS architecture that is utilizing agents associated with the loads, DERs and OLTC transformer. The developed control architecture optimally coordinates among active and reactive power control droops of GTIs. Secondly, a voltage flicker mitigation scheme is proposed that will react to the fast voltage fluctuations in a sub-second timescale. Lastly, a comprehensive control strategy is proposed that can address the voltage quality paradigm with the minimum latency and computation, having three distinct control levels of flicker control, local voltage control and coordinated voltage control. The proposed methodologies are validated by their employment in the realistic Finnish distribution networks. The second objective is to formulate a stochastic framework that can assess the HC potential of the distribution networks and their limiting constraints. To achieve the goal, realistic Finnish low voltage networks for various geographical locations are planned and studied. Later, the HC enhancement potential of BESS, due to voltage unbalance reduction, is quantified. Lastly, the OLTC and reactive power support from GTIs are employed to improve the HCs of the grids having an overvoltage issue and is compared with the traditional cost-intensive network reinforcement approach. The BESS employment in the same phase as the single-phase PV and the OLTC or OLTC in tandem with reactive power support from GTIs are found to have great theoretical potential for HC enhancement.
|Julkaisun otsikon käännös||Voltage Control and Photovoltaic Hosting Capacity in Distribution Networks|
|Tila||Julkaistu - 2019|
|OKM-julkaisutyyppi||G5 Tohtorinväitöskirja (artikkeli)|