Large Penetration Of Renewable Energy Sources Research Articles

Role of pumped-storage hydroelectric power plants and large penetration of electric vehicles in increasing power system flexibility with large share of renewable sources

The European Union's (EU) goals of reducing energy dependence and reducing greenhouse gas emissions (GHG) are to be achieved primarily by increasing production from renewable energy sources (RES). However, due to the features of renewable sources such as unpredictability and lack of availability, it is necessary to increase the flexibility of the systems themselves. In other words, large penetration of RES into the power system requires a substantial increase in the capacity of various energy storage technologies. Pumped storage hydroelectric power plants (HPPs) represent 99% of global installed capacity of energy storage and are widely spread, providing energy storage capacity and transmission grid ancillary benefits in the US and Europe since 1920s, as well as in the rest of the world. Besides, new technologies are considered worldwide, and as one of the most prominent options considered today is the penetration of electric vehicles (EVs) into the power systems. The use of EVs reduces air pollution while connecting them to the smart grids creates the possibility of increasing the flexibility of the power system since vehicle batteries could be used as storage but also as sources of electricity. Using the PLEXOS energy market simulation software, the power system of the Republic of Croatia was modelled in this paper and based on the results of different scenarios, the role of pumped-storage power plants and large penetration of electric vehicles in increasing the power system flexibility with a large share of renewable sources was observed.

Effect of inertia heterogeneity on frequency dynamics of low‐inertia power systems

Based on fundamental dynamic simulation principles and illustrative case studies, this study aims to identify key changes in the dynamic behaviour of the system due to the high penetration of renewable energy sources (RES) affecting frequency dynamics and provide guidelines for performing frequency stability analysis in low-inertia power systems with a large penetration of RES. First, a critical comparison of the frequency responses obtained using a system equivalent model and a detailed dynamic model following an active power disturbance are presented. It is then demonstrated, using detailed dynamic models of two multi-area systems, such that when the proportion of RES prevails over the share of synchronous generator (SG), the dynamic coupling among areas (even separated by short-medium length lines) reduces and the inertia of the system should be considered as heterogeneous instead of a global parameter. Following this, the study discusses how frequency dynamics may be strongly and complexly affected by the physical characteristics of converter-connected generation leading to increased frequency and voltage interactions when the proportion of converter connected RES becomes greater than SG. The resulting changes in the system's dynamic behaviour due to frequency and voltage interactions can increase the actual active power imbalance size following a credible contingency so that careful considerations to protect the system against an excessively high rate of change of frequency should be made. In order to evaluate the extent of this change in system dynamic behaviour, an appropriate dynamic model of the network should be used with adequate multi-area representation of RES and loads.

電力系統における需給解析・シミュレーションの動向について

The stable electric power supply requires to maintain the system frequency within a specified band by matching the supply and demand constantly with the help of Economic load Dispatching Control (EDC) or Load Frequency Control (LFC). On the other hand, recently the penetration of renewable energy sources (RESs) such as photovoltaic generations (PVs) and wind turbines (WTs) are rapidly increasing due to the introduction of feed-in tariff (FIT) and growing environmental awareness. However, the output power generated by these RESs depends on the climatic conditions, and as such the output may not always be available when required. As a result, it would be more difficult to ensure the stable power supply by balancing the supply and demand in view of the uncertain outputs of RESs at all the time. In order to grasp the influences and to verify the effectiveness of countermeasures for various issues such as the frequency deviation caused by a large penetration of RESs, the analysis and simulation technologies for the electric power supply and demand control are becoming more important. Hence in this paper, the recent trends of these technologies are reviewed.