Black start on a medium voltage grid with storage and PV
03 HYB24-18
Presented by: Adolfo Anta
The ongoing replacement of fossil fuel-based power plants by inverter-based generation is posing severe challenges to system planning and operation in power grids. Novel sources are supposed to take the responsibility of maintaining grid stability and providing adequate services. In particular, black start is one functionality that, as of today, still relies on the presence of conventional power plants, to the extent that some of these need to be kept online for the sole purpose of providing black start capabilities if needed. In comparison with conventional power plants, inverter-based resources are very flexible and controllable, but are characterized by their limited ratings.
In this work we focus on the restoration of MV grids, under the assumption that a top-down restoration is not possible, given that the high voltage grid is not available. The MV grid aims at restoring the power using the generation units present in its grid. We consider the case of a MV grid in the Austrian province of Styria, equipped with a storage unit and distributed photovoltaic (PV) units, forming a hybrid power plant. These types of configurations are as of lately gaining popularity, as the different dynamic characteristics of each asset can be leveraged to provide a wide range of services, considering all time scales. As a by-product, in this work the minimum required rating of said battery will be explored. While PV plus storage for black start has already been explored, the focus has been on the unit behaviour and long-term feasibility. Instead, here we focus on the system-wide transient aspects that occur during the early (and critical) phase of the grid restoration process. Long term, the MV grid is supposed to be resupplied by the transmission grid once this is re-energized. We assume the presence of a central controller that is able to receive the status of the grid and send commands to the storage unit and the PV systems.
In our proposed strategy, the storage unit first soft energizes the medium voltage lines and some of the MV/LV transformers (as many as possible), and afterwards connects the PV unit to leverage its reactive power capabilities. Given the smaller ratings of inverters (compared to conventional generation), it is expected that the collaboration of inverter-based resources would be needed to properly black start a grid of a decent size. This would drastically augment the amount of reactive power available for the black start. Then, the rest of the transformers can be connected in a sequentially manner. Finally, critical loads can be connected.
The proposed ideas have been evaluated against a medium voltage grid in Austria, equipped with a battery and a large PV facility with adequate performance of the grid and the inverter-based generation. The starting model is provided by the distribution system operator (DSO), namely Energienetze Steiermark. The model corresponds to a MV grid with 174 transformers, 323 lines, 1465 switches and 469 loads. Next to the planned storage unit, a solar plant rated at 1MW is to be installed. The connection to the transmission grid is assumed to be open, as the initial status corresponds to a system wide blackout. Simulation results show the adequate response of the inverter-based resources and the successful grid restoration, despite the large number of transformers to be energized.
In this work we focus on the restoration of MV grids, under the assumption that a top-down restoration is not possible, given that the high voltage grid is not available. The MV grid aims at restoring the power using the generation units present in its grid. We consider the case of a MV grid in the Austrian province of Styria, equipped with a storage unit and distributed photovoltaic (PV) units, forming a hybrid power plant. These types of configurations are as of lately gaining popularity, as the different dynamic characteristics of each asset can be leveraged to provide a wide range of services, considering all time scales. As a by-product, in this work the minimum required rating of said battery will be explored. While PV plus storage for black start has already been explored, the focus has been on the unit behaviour and long-term feasibility. Instead, here we focus on the system-wide transient aspects that occur during the early (and critical) phase of the grid restoration process. Long term, the MV grid is supposed to be resupplied by the transmission grid once this is re-energized. We assume the presence of a central controller that is able to receive the status of the grid and send commands to the storage unit and the PV systems.
In our proposed strategy, the storage unit first soft energizes the medium voltage lines and some of the MV/LV transformers (as many as possible), and afterwards connects the PV unit to leverage its reactive power capabilities. Given the smaller ratings of inverters (compared to conventional generation), it is expected that the collaboration of inverter-based resources would be needed to properly black start a grid of a decent size. This would drastically augment the amount of reactive power available for the black start. Then, the rest of the transformers can be connected in a sequentially manner. Finally, critical loads can be connected.
The proposed ideas have been evaluated against a medium voltage grid in Austria, equipped with a battery and a large PV facility with adequate performance of the grid and the inverter-based generation. The starting model is provided by the distribution system operator (DSO), namely Energienetze Steiermark. The model corresponds to a MV grid with 174 transformers, 323 lines, 1465 switches and 469 loads. Next to the planned storage unit, a solar plant rated at 1MW is to be installed. The connection to the transmission grid is assumed to be open, as the initial status corresponds to a system wide blackout. Simulation results show the adequate response of the inverter-based resources and the successful grid restoration, despite the large number of transformers to be energized.