Abstract
One of the main constraints for Renewable Energy Sources (RES) integration in LV networks are overvoltages caused by changing the normal power flow of the network. In favourable weather conditions high voltages may lead to overvoltage trips thus preventing the injection of renewable energy into the grid. An optimized management of power injection from controlled RES to keep the grid voltage within regulatory limits enables a larger energy output and deployment of distributed generation. The SuSTAINABLE project developed a centralized algorithm based on a hierarchical methodology to control distributed power injection and solve the identified issue. A decentralized algorithm based on a coordinated droop control embedded in the inverters was developed as well. In order to evaluate the proposed algorithms a controllable PV µG and batteries were installed at the end of the feeder of a real LV network operated by EDP Distribuicao. The obtained results are presented in this paper and show that a hierarchical methodology to control power injection could optimize RES energy production while maintaining voltages within bounds, thus enabling a larger deployment of RES at the LV levels.

Abstract
It is demonstrated that in grid-tied-inverter control, resonant integrators can be moved from the current loop to the input voltage filter allowing for better accuracy of voltage rms and frequency measurements whithout compromising controlability. Design of the input filter is discussed to ensure good performance and phase compensation and a robust feed-forward is built upon this filter that, together with the elimination of output distortion, results in a fair open-loop control response. By closing the loop with a PI controller and by turning off supposedly non-conducting IGBTs, a current transient results that competes with state-of-the-art control strategies and is only limited by output filter inductance while allowing for a fast and accurate estimator of grid parameters such as voltage rms and frequency, essential for fast droop control.

Abstract
Renewable energy sources are environmentally appealing in electrical power grids. However, distributed energy resources (DER) are typically connected to the grid through converters that do not have the same properties as synchronous generators which have high participation in power generation. Some of these properties like inertial response are important and must not be lost with higher DER penetration. The present paper analyses two converter control algorithms that are capable of emulating inertial response in DER: the Virtual Synchronous Generator control (VSG) and the Synchronverter. Both algorithms are described, implemented and tested in a practical experiment and a comparison of both algorithms is assessed in terms of frequency nadir achieved, settling time and implementation complexity. The findings can give useful insights to help decide which algorithm should be implemented in a future real application.

Abstract
Using power-hardware-in-the-loop is a solution for testing the behavior of devices on an emulated grid, with greater flexibility and avoiding the introduction of disturbances or critical operating conditions in the utility grid. This paper highlights the implementation of such a setup, its challenges and the solutions to cope with its limitations. The emulated grid is then used for the experimental validation of a 10kVA converter, regarding fault-ride-through, dynamic reactive current support and frequency and voltage based droop control, leading to the identification of design improvement recommendations.