Modeling and Control of a Three Phase Voltage Source Inverter with an LCL Filter by Aratrik Sarkar A Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science ARIZONA STATE UNIVERSITY May 2015
This thesis addresses the design and control of three phase inverters. Such inverters are used to produce three-phase sinusoidal voltages and currents from a DC source. They are critical for injecting power from renewable energy sources into the grid. This is especially true since many of these sources of energy are DC sources (e.g. solar photovoltaic) or need to be stored in DC batteries because they are intermittent (e.g. wind and solar). Two classes of inverters are examined in this thesis. A control-centric design procedure is presented for each class. The first class of inverters is simple in that they consist of three decoupled subsystems. Such inverters are characterized by no mutual inductance between the three phases. As such, no multivariable coupling is present and decentralized single-input single-output (SISO) control theory suffices to generate acceptable control designs. For this class of inverters several families of controllers are addressed in order to examine command following as well as input disturbance and noise attenuation specifications. The goal here is to illuminate fundamental tradeoffs. Such tradeoffs include an improvement in the in-band command following and output disturbance attenuation versus a deterioration in out-of-band noise attenuation. A fundamental deficiency associated with such inverters is their large size. This can be remedied by designing a smaller core. This naturally leads to the second class of inverters considered in this work. These inverters are characterized by significant mutual inductances and multivariable coupling. As such, SISO control theory is generally not adequate and multiple-input multiple-output (MIMO) theory becomes essential for controlling these inverters.
LINK COMPLETE THESIS