Localised Demand Control for Improved Grid Integration of Renewable Energy and Electric Vehicles

Abstract

Reliable electricity supply is essential to the way of life in developed countries and of extreme importance when looking to raise the standard of living in developing countries. Unfortunately electricity generation is dominated by fossil fuels which cause significant pollution and emissions – a situation that due to climate change and environmental concerns should not continue. Most power systems also tend to show significant peaks in electricity demand for only a few hours per day. Since power systems are designed to handle the peak demand, peaking plants could be replaced with renewable generation if some demand were able to be shifted in time. This would be more cost effective and emissions would be reduced. Shifting demand in time can be achieved with Demand Side Management (DSM), and a new DSM scheme called Localised Demand Control (LDC) is introduced in this thesis. LDC is compared with a traditional DSM scheme called Dynamic Demand Control (DDC). A number of aspects that make DDC unsuitable are presented, and LDC is shown to improve on these while also providing additional benefits. LDC is designed to regulate power flow on a single distribution transformer, and the stability and transient response of LDC is presented. Simulations of transformers with controllable load and fluctuating local generation are presented and these show good results. A method of load scheduling is also demonstrated, which reduces electricity cost without impacting the end user. A lab-scale system has been created and its stability and transient response match those of the simulated system. Here a 3-phase power meter measures power flow and a centralised LDC controller determines a load control signal which is then distributed to controllable loads. Motor-generator sets are used to simulate fluctuating local generation sources and the system provides good power regulation with just a small number of controllable loads. A custom power-line communication system is used to distribute the load control signal, and the performance has been verified in the lab and in simulations with a large amount of signal noise. The proposed LDC system could be used to improve integration of renewable energy and electric vehicles in the power system, increasing efficiency and reducing emissions.