The recent deployment of distributed battery units in prosumer premises offer new opportunities for providing aggregated flexibility services to both distribution system operators and balance responsible parties. The optimization problem presented in this paper is formulated with an objective of cost minimization which includes energy and battery degradation cost to provide flexibility services. A decomposed solution approach with the alternating direction method of multipliers (ADMM) is used instead of commonly adopted centralised optimization to reduce the computational burden and time, and then reduce scalability limitations. In this work we apply a modified version of ADMM that includes two new features with respect to the original algorithm: first, the primal variables are updated concurrently, which reduces significantly the computational cost when we have a large number of involved prosumers; second, it includes a regularization term named Proximal Jacobian (PJ) that ensures the stability of the solution. A case study is presented for optimal battery operation of 100 prosumer sites with real-life data. The proposed method finds a solution which is equivalent to the centralised optimization problem and is computed between 5 and 12 times faster. Thus, aggregators or large-scale energy communities can use this scalable algorithm to provide flexibility services.

The paper proposes an algorithm for active and reactive power management in large PV power plants. The algorithm is designed in order to fulfil the requirements of the most demanding grid codes and combines the utilisation of the PV inverters, fixed switched capacitors and STATCOMs. The control algorithm is simulated as required by the grid codes and validated on a real 9.4 MW photovoltaic power plant.

In meshed High Voltage Direct Current (HVDC) grids, the current of each line cannot be controlled independently, since it depends on the resistances between nodes. Additional devices, such as Current Flow Controllers (CFCs), may be needed to avoid bottlenecks or line overloads. This work presents a multi-port DC/DC based CFC topology to be connected to lines with unidirectional current flows. The device is able to control the DC lines' currents to the desired value by inserting variable voltage sources in series. First, the modelling of the generic -port topology is presented and then, its modulation and control strategy are described. In the first case study, the concept is validated considering a 5-port CFC by means of dynamic simulations using different control methods. Finally, in the second case study, a 3-port CFC prototype is built and tested in an experimental platform in the laboratory considering different control modes.

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