This study reports the methodology and results of a renewables (REs) integration grid study for the 2030 Japanese power system. In light of the Japanese energy policy outlook for 2030, two scenarios were compared: the government's target scenario with 22–24% RE penetration (64 GW solar and 10 GW wind), and a scenario with higher RE penetration (100 GW solar and 36 GW wind). The impact of these two RE integration scenarios on the grid in terms of frequency stability and power flows were simulated and compared. The evaluation outcomes showed that a RE penetration more ambitious than the government's plan can be achieved without compromising the evaluated elements of grid security and without additional technical measures in situations with at least up to 62% variable REs, i.e. wind and solar, instantaneous penetration in western Japan and at least up to 36% in eastern Japan. Furthermore, technical solutions like soliciting fast frequency response from solar and wind power plants, and setting a system non-synchronous penetration limit for grid management can be applied to improve grid security for higher RE penetrations.

The North Sea region offers large amounts of investable offshore wind generation and several interconnection lines are located in the area, with more planned. Optimal transmission and generation investments are modelled in the region towards 2050. A project-based scenario, where each offshore wind power plant is connected individually, is first analysed. Then, an integrated offshore grid is modelled to investigate the viability of connecting future transmission and offshore wind generation investments. These two scenarios are then compared. It is shown that going towards an integrated solution can increase offshore wind investments by several GWs, with Germany seeing the biggest difference between the two scenarios. It is shown that the integrated solution leads to overall cost minimisation and shows somewhat higher variable renewable energy generation by 2050 compared to the project-based scenario.

The penetration of power electronic interfaced generation (PEIG) is expected to reach up to 65% in some parts of the European power system by 2030 (at least during some hours of the year). Under such grid conditions, system security challenges are observed with frequency stability, voltage stability and undamped converter control interactions being among the most important issues. This study presents a short-term voltage stability assessment of the Great Britain synchronous area under EMT modelling assumptions. The study provides a mapping of system stability and identifies the critical penetration level of PEIG that instabilities are observed. In addition, an application of a grid forming control scheme (namely the enhanced direct power control) is proposed as a mitigation option which is applied here on full-converter interfaced wind power plants (type-4). The simulation results reveal that the application of the grid forming control to a part of the total wind power generation fleet can mitigate the instabilities observed, while enabling the system operation with 100% PEIG.

Gotland is a Swedish island that is connected to the grid only by two high voltage direct current (HVDC) cables. The growth of installed wind power on Gotland has been temporarily stopped due to concerns regarding the reliability of the operations. This study investigates the capability of a centralised energy storage system along with or without wind curtailment to support the growth of installed wind power capacity. The energy storage system is tested for maintaining frequency stability during unintentional islanding through dynamic studies using power system simulator for engineering (PSS/E). The results assess the ability of energy storage to prevent frequency instabilities and provide primary frequency response albeit of the absence of any rotating inertia. The analysis determines the requirements for the power and energy capacity of the energy storage system in relation to the exported power from the HVDC cables at the instant of fault, which eventually relates to the wind power capacity. Moreover, the study examines wind power curtailment as primary and/or secondary frequency response and the impact on the energy capacity. Finally, the study did not explore the effect of fast power ramps on the energy storage to leave the door open for all types of inverter-based energy storage technologies.