Improvement in Frequency Stability of Power Grids With High Penetration of Renewable Energy Sources: Market-Clearing and Pricing of Required Ancillary Services

In this article, a market-clearing (MC) and pricing method is proposed for ancillary services (ASs) that are needed for improvement in the frequency stability of power grids with high penetration of renewable energy sources (RESs). These ASs include primary frequency response (PFR) services for maintaining the rate-of-change-of-frequency and frequency nadir within the permissible ranges. Historically, the RESs did not provide the PFR services since there have been neither requirements nor incentives to do so. However, in this article, a pricing method is suggested to address the RESs' incentives providing the PFR services. As a result, higher penetration levels of RESs are facilitated from both technical and economical viewpoints. From the technical point of view, the RESs' participation in the PFR is necessary since the total inertial and governor responses of conventional generating units might not be sufficient for the frequency stability. In addition, from the economical point of view, with greater need for the PFR services and increase in their prices in long term, the ASs incomes might become a sizeable fraction of the RESs' total incomes. In the case study, the effectiveness of the proposed MC and pricing method is verified using the IEEE 30-bus test system by comparing the results with existing methods.