Abstract
The deviation of the demand levels of the modern LV distribution systems due to the more loads and distributed generations connected in the same grid leads to the loss of acceptable quality of voltage. These voltage quality problems occur in case of the high difference between the power of the loads and distributed generations in the same area. Accordingly, the high loading conditions lead to the bus voltage decrease while the bus voltage increment occurs in scenarios with the excess of generation. In this condition, the successful voltage stabilization in MV/LV substation can effectively suppress the deviations of the grid voltage values and increase the hosting capacity of the network. There are different custom power devices introduced in the literature which can provide the stabilization of voltage in the grids. In this paper, among the available tools, the application of Open-UPQC is examined in hosting capacity improvement maintaining a desired power quality level; this capability is provided through the successful voltage regulation in the different probable high/low loading scenarios in the grid. According to the results, while the uncoordinated operation of the series and shunt devices does not have the capability of stabilization of the base grid, the Open-UPQC has successfully maintained the voltage profile inside the limits in both the base case and in the presence of high load and PV penetration levels. It should be emphasized that the services of the Open-UPQC are provided in an economical and effective way making the solution strategy applicable in real-world cases. © 2023 IEEE.

Abstract
The increasing number of Power-Electronic (PE) interfaced devices in the new generation of distribution systems results in concerns about the power quality of modern grids. Besides the loads, the harmonic-injecting devices are increasingly penetrating the generation, storage, and delivering levels of energy dispatch systems in the microgrids and the LV networks which can be easily reflected in the primary distribution systems. As an economic, applicable, and efficient solution, the passive filters can be optimized and added to the grid to absorb the harmonics. Furthermore, in the presence of controllable devices such as PE-interfaced DGs and storage units, a coordination strategy can be implemented to actively decrease the effect of the nonlinear loads. Accordingly, the idea of a virtually-hybrid filter can be developed by the use of passive filters and the coordinated active harmonic filtering strategy. In this paper, by providing an explanation for the developed coordination strategy of active filters, the probabilistic techno-economic planning of virtually-hybrid filters is studied considering the different combinations of the linear and nonlinear loads in a modern primary distribution system. Simulation results have proved that the proposed method is capable of minimizing harmonic distortions and grid loss by the use of the optimal passive filters and the suggested coordination strategy of the active devices. © 2023 IEEE.

Abstract
The growing concern about global climate change has led the European Union and the Portuguese Government to set targets for the percentage of electricity to be produced from renewable sources. In order to achieve the defined targets, Distributed Generation (DG) is expected to be increasingly integrated into networks. However, the intermittency of some of those DGs (such as wind energy) may enhance network operating costs or decrease network security. Thus, Network Operators started to concern about these effects and in order to avoid them, new wind parks were required to provide ancillary services to the network. These ancillary services include the ride-through-fault capability. Although some wind parks can already supply ride-through-fault capability to the distribution network (i.e. wind parks with Double Fed Induction Generators (DFIG)), most of them are still largely unable to do so due to the current DG protection scheme. This work concentrates on the development of new settings for the DG protection scheme which aims at allowing DG to provide ride-through fault capability to the distribution network. A DFIG with ride-through-fault capability was modeled on PSCAD/EMTDC and tested under the Portuguese Distributed Generation Protection Scheme Regulation Code. New relay settings for the DG protection scheme are advanced and simulated on PSCAD/EMTDC software in order to permit DGs providing ride-through fault capability to the distribution network. Conclusions of the new relay settings performance are withdrawn and commented on.

Abstract
The integration of larger and larger amounts of wind power is a major target of the European Union, however it represents a challenge for power system planning and operation. The paper analyses stability aspects concerning the operation of Multi-Terminal HVDC networks connecting offshore wind farms to the AC systems. Modelling issues are tackled, relevant to control schemes needed for a secure operation of the overall AC-DC system in case of contingencies both on the AC side and on the DC side. First, power flow control principles are described for the "backbone" HVDC grid topology (consisting of point-to-point connections between offshore wind farms and mainland grid, linked by a DC connection). Second, dynamic converter models suitable to investigate electromechanical transients are illustrated and some stability issues connected to the network performance under contingencies/disturbances are pointed out. The need both to survive severe disturbances and to provide ancillary services calls for the adoption of advanced control schemes. Some simulations are described to illustrate the behaviour of the mixed AC-DC network under contingencies concerning both faults on DC cables and faults on AC lines. The work has been carried out within Working Package 5 of EU co-founded Project TWENTIES.

Abstract
This paper addresses the problem of providing frequency control services, including inertia emulation and primary frequency control, from offshore wind farms connected through a multiterminal HVDC network. The proposed strategy consists of a cascading control mechanism based on dc voltage regulation at the onshore converters and frequency regulation at the offshore converters. The control scheme involves only local measurements and actions avoiding security and reliability issues of control structures based on remote information. The effectiveness of the proposed strategy is illustrated in a test system that consists of two nonsynchronous areas linked by a multiterminal HVDC grid where two offshore wind farms are also connected.

Abstract
The massive interconnection of offshore Wind Farms (WF) brings challenges for the operation of electric grids. The predicted amount of offshore wind power will lead to a smaller ratio of conventional units operating in the system. Thus, the power system will have less capability to provide fast dynamic regulation. Despite of offshore WF being able to inject power on the AC grid through High Voltage Direct Current (HVDC) convertors, they cannot participate on frequency support by the intrinsic decoupling that DC adoption brings. This paper proposes a control methodology, based on local controllers, to enable the participation of offshore WF in primary frequency control. Additionally, enhancements were made on the Wind Energy Converters (WEC) controller to make them capable of emulating inertial behaviour. Tests were performed in a multi-terminal DC network with two off shore wind farms to assess the feasibility and effectiveness of the concept in a communication-free framework.