AC/DC Smart Control and Power Sharing of DC Distribution Systems

摘要

The purpose of this research is to develop a grid connected DC distribution system to ensure efficient integration of different alternate sources to the power system. An investigation of different AC and DC converter topologies and their control is conducted. A new converter topology for sharing DC power was developed to enhance the efficiency and stability of the alternate sources connected to the DC Distribution System. Mathematical model and control system design of the developed converters were included in the thesis.A novel smart-PID controller for optimal control of DC-DC converter was used as voltage controller in PV systems. This controller maximizes the stable operating range by using genetic algorithm (GA) to tune the PID parameters ultimately at various loading conditions. A fuzzy logic approach was then used to add a factor of intelligence to the controller such that it can move among different values of proportional gain, derivative gain, and integral gain based on the system conditions. This controller allows optimal control of boost converter at any loading condition with no need to retune the parameters or possibility of failure. Moreover, a novel technique to move between the PI and PID configurations of the controller such that the minimum overshoot and ripple are achieved. This increases the controller applicability for utilization of PV systems in supplying sensitive loads.An effective algorithm for optimizing distribution system operation in a smart grid, from cost and system stability points of view, was developed. This algorithm mainly aims to control the power available from different sources so they satisfy the load demand with the least possible cost while giving the highest priority to renewable energy sources. Moreover, a smart battery charger was designed to control the batteries and allow them to discharge only when there is a small load predicted. During the period they become available, they act as a buffer for the predicted large load to increase the stability of the system and reduce voltage dips.