Real-time simulation based analysis of Fast Active Power Regulation strategies to enhance frequency support from PE interfaced Multi-Energy system

Abstract

Until recent times, electrical power grids have been dominated by conventional power plants run by fossil or nuclear fuels in order to cater to the electrical load demand. These power plants employ large generators that operate in synchronous with each other to maintain a stable frequency and voltage across the power grid. The frequency and voltage stability, which are respectively linked to active and reactive power serves as a backbone for a secure operation of the power system. Furthermore, since these classical generation sources promised support of ancillary services during unstable conditions, along with power generation, they were characterized as a reliable solution for maintaining the security of the power system. But, due to the high emission of carbon by-products from these fossil-fuelled generators, challenges of global warming and climate change have made it inevitable to decommission them. And more emphasis has been embarked on the adaptation of renewable energy sources (RES) which offer minimum carbon footprint. Geothermal heat, wind, sunlight, and tides constitute some of the Renewable energy sources since their availability are unlimited and involve the least emission of greenhouse gasses, hence Renewable Energy Sources have a minimal impact on the environment compared to traditional energy sources and can effectively tackle the problems which arise with fossil fuel usage. For all these reasons, during the last decades, there is fierce research on finding ways to produce the needed energy in a sustainable fashion. Synchronous Generators, which are dominant in the existing power grid, have the inherent characteristics to relate system’s frequency with load balance. This considerable advantage is found missing from Power Electronic interfaced renewable energy resources due to the following reasons. Firstly, since active power support was earlier the main purpose of using these devices, they were operated at Maximum power point tracking (MPPT). Secondly, in wind energy technology, isolation between electrical and mechanical circuits had to be introduced due to their variable behavior of energy production, and this has led to no inertia backing from the synthetically produced frequency. So with high penetration of RES in the future grids, the aforementioned problems pose huge risks for grid stability and reliability. The current research mainly focuses on the development, implementation, testing, and validation of frequency regulation strategies under the umbrella of Fast Active Power Regulation controllers specifically to support during large load frequency variation in low inertia power system grid. These controllers developed are very generic and can be implemented with slight modifications in all the renewable energy devices with ease. In order to simulate more real-time behavioral conditions, dynamic simulation studies are performed in RSCAD software interfaced with a Real-Time Digital Simulator (RTDS). Two Test benches have been considered in this thesis, one being an IEEE 9 bus system modified with 52% wind share and another is the North of Netherlands Network. In the first stage of the project, FAPR controller’s proof of concept has been tested on a Type-4 Wind generator setup connected to the modified IEEE 9 bus system. Here wind penetration is scaled up to 52% and a low inertia grid have been simulated. Later, the results obtained here were validated by Hardware in Loop setup utilizing a mock-up grid side converter. The next stage of the project aims at making FAPR controllers more generic. For this the North of Netherlands network was modified by adding FAPR integrated 300MW solar farm, FAPR integrated 82MW full converter based Type-4 Wind Turbine and lastly, a responsive load (Electrolyser) was modified to accommodate FAPR controllers. All together formed a Multi-Energy Hub and simulations were performed to check the practical feasibility and boundaries of operation of FAPR controllers in the future power grid. The results prove that the proposed topology and control strategies can effectively provide frequency ancillary services to the grid by providing support during dynamic load frequency variations.