High-bandwidth droop-based controllers for DC and AC microgrids

Due to the reduction in the transmission and distribution losses, the overall system costs and the CO2 emissions, distributed power generation based on sustainable and green resources, such as photovoltaic and wind have been exploited over the past decades. Grouping several mentioned power resources together with some loads as well as some energy storage systems is so-called a microgrid environment. Also, in microgrids, as the sources are near the loads, the power quality, efficiency, and reliability will be significantly increased. Microgrids are also a smart choice for remote locations that are not reachable by the main grid. Microgrids have three different architectures, DC, ac, and hybrid. DC microgrids bring some advantages over their AC counterpart. For instance, the inductive voltage drop is removed in a DC system. But still, AC microgrid is more compatible with the nature of many DERs such as wind and electric motors load. These facts make it valuable to consider both AC and DC microgrids for research activities. Sharing loads automatically between parallel resources in microgrids is an important aspect. A primary level control like the droop control solution can be used to share the power among parallel resources without any communication. Droop control is a simple approach that mostly applies to parallel DERs to ensure their stability. In AC systems, it generates the output reference voltage magnitude and voltage frequency of the DG units based on their reactive (Q–V) and active power (P–F) values and in DC systems, It functions by introducing virtual resistance in line to equalize current sharing or by controlling voltage magnitude based on active power (P–V). This dissertation focuses on performance improvement of droop-controlled converters, mainly in the following three aspects: i) a novel Dual-Edge (DE) PWM suitable for DC/AC and DC/DC converters with reduced modulation delay, and a graphical-based analysis for its dynamic behavior, and its effect on output impedance and stability; ii) reduction of DC bus capacitance while maintaining tight DC bus voltage regulation in DC microgrids; iii) Per-Phase Power Controller in AC Microgrids with smooth transfer from the power flow control to droop control, allowing AC microgrids to seamlessly disconnect from upstream grids.