With the dramatic increase in electricity demand and the need to tackle climate change by reducing greenhouse gas emissions such as CO₂, renewable generation has been increased in recent years in power systems. However, highly integrating renewable generation in distribution systems raises several issues and challenges that need to be addressed and some of these issues are investigated in this thesis. This research focuses on investigating the fault ride through, the system transient stability, the system frequency response and the grid power factor of distribution systems with high renewable energy penetration based on wind and solar-photovoltaic (PV). Several proposed control techniques for wind generators and PVs are introduced in this research to solve these issues and mitigate the negative impact of these units on distribution systems. A modified control system of DGs based on wind and PV in different distribution systems is used to help to ride through faults and meet the low voltage ride through (LVRT) grid code requirements for voltage recovery. A three phase two stage transformerless PV grid connected system is proposed with a new technique to ride through faults and protect the power electronic converters. A DC chopper is added to the DC link of wind generators to enable wind generating units to ride through faults and protect their converters from overvoltages. The Transient Stability Index method is used to assess the impact of such renewable sources on the system transient stability of various distribution networks. Different frequency control methods published in literature are used for various DGs based on wind and PV to investigate the frequency response of different distribution networks with high renewable energy penetration, and a new frequency control technique is proposed for wind generators based on Doubly Fed Induction Generator (DFIG) to improve the system frequency response. The impact of high renewable energy penetration based on wind and PV with different power factor settings on grid power factor of various distribution systems is discussed in this research. A three phase two stage transformerless PV grid connected system with reactive power capability is proposed to operate under different solar irradiance conditions and improve the utility grid power factor. Simulation results validate the proposed systems in various distribution systems, including IEEE 13 bus, IEEE 37 bus and IEEE 123 bus systems.
|Date of Award||14 Feb 2016|
- University Of Strathclyde