Whether to consider transformer capacity when connecting energy storage power station to the grid

How to choose the rated power of a step-up transformer?

The selection of the rated power of the step-up transformer becomes more complex when considering a PV plant with energy storage capabilities, as an optimal solution must be detected taking also into account the features and the cost of the Energy Storage System (ESS) and their effects on the cost and efficiency of the whole system.

Should a transformer be rated near a PV plant peak power?

In fact, while selecting a transformer rated power close to the PV plant peak power makes theoretically possible to fully transfer the captured solar energy to the utility network, such a design criterion will in practice lead to oversize both the transformer, the inverter and the power line.

How to choose a step-up transformer in a PV plant?

In general, the selection of the step-up transformer in a PV plant is a quite complex task as several variables depending on the transformer rated power must be taken into account as: initial cost of the system, energy losses due to transformer efficiency, energy storage system efficiency and possible plant disconnections due to grid instability.

Do step-up transformers cause grid instabilities?

Abstract: - Step-up transformers are used to connect large PV plants to the utility network, their sizing being often accomplished only taking into account the PV plant peak power. However, a largely unpredictable power injection on the main grid is obtained if a too large rated power is selected, leading to grid instabilities.

What is a grid-tied PV system without energy storage?

Before untangling more puzzling windings decisions for isolation transformers, transformers with energy storage in microgrid scenarios, or PV systems supplying both three-phase and single-phase dedicated loads, let us consider a common case: a grid-tied PV system without storage. In this scenario, the PV system is exporting power to the grid.

How to evaluate energy loss due to transformer overloads?

In order to evaluate the energy loss due to transformer overloads a probabilistic approach is followed based on the LPPP (Loss of Produced Power Probability) index. Such an approach derives from the well-known LPSP (Lost of Power Supply Probability) technique used on PV plants operating in island mode [19-24].