Dynamic control and power management of converter fed microgrids

The subject of this thesis is modeling and control of voltage source converter (VSC) fed microgrids. These microgrids are powered by modern distributed generators that require VSCs as part of their grid interface circuitry. This thesis develops two supervisory control schemes that allow VSCs with standard inductor interface and the ubiquitous dq-frame current control to operate in both grid connected and islanded modes. Both of these supervisory control schemes are based on a dynamic model of a VSC fed islanded microgrid, which reveals that the microgrid voltage depends on the real power balance between the VSCs and the load while reactive power balance determines the frequency. Thus, both control schemes set the real and reactive power references of the VSCs to regulate the microgrid voltage and frequency respectively.; The Voltage-Power Droop/Frequency-Reactive Power Boost (VPD/FQB) control scheme acts as a supervisory control over the dq-frame current control of a VSC. It allows parallel operating VSCs to jointly regulate a common microgrid voltage and frequency. A VPD/FQB controller droops its voltage reference against the VSC real power output for joint regulation of the microgrid voltage and autonomous real power sharing among the VSCs. Similarly, a frequency-reactive power boost characteristic is employed to achieve joint frequency regulation and autonomous reactive power sharing. A systematic method of coordinating the parameters of parallel operating VPD/FQB controllers is also presented to guarantee damping of inter-controller modes and provide instantaneous load sharing.; The second supervisory control scheme, called the Voltage-Power/Frequency-Reactive Power Cross Droop (VP/FQ Cross Droop) control scheme, allows a current controlled VSC to share a common load with synchronous generators as well as other VSCs. A VP/FQ Cross Droop controller droops its frequency reference against the VSC real power output and voltage reference against the reactive power output to share a common real and reactive load respectively.; Despite its versatility, the VP/FQ Cross Droop control scheme does not replace the VPD/FQB control scheme in purely VSC fed microgrids due to the former's comparatively poorer inter-controller dynamics.