Bidirectional Power Control of Grid Connected Three-phase Inverter under Unbalanced Conditions
Type of DegreePhD Dissertation
Electrical and Computer Engineering
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This research explores bidirectional real and reactive power control of a 100kW threephase, grid-connected inverter under unbalanced grid conditions. Different unbalanced grid conditions are studied, including unbalanced three-phase load and unbalanced grid impedance. The new power control methods can simultaneously fulfill multiple goals, such as balancing grid currents, balancing point-of-common-coupling voltage, and grid power injection. Instability of real and reactive power is removed, and power control is achieved. Four control methods have been applied to satisfy the requirements. Such as a modified proportional-integral (PI) control and a modified proportional-resonant (PR) control; a time domain symmetrical component extraction method with a P controller; and a time domain symmetrical component extraction method with a PR controller. Simulation and experimental results confirm the effectiveness of these four control methods under different unbalanced conditions. Different simulation results have been obtained using MATLAB/SIMULINK simulation software, and different experimental results have been obtained using a real-time interface platform, dSPACE DS1202.