Control of power converter for grid integration of renewable energy conversion and STATCOM systems
Investment in renewable energy is rapidly increasing worldwide. This is in response to a number of global challenges and concerns, including climate change, increasing energy demand, and energy security. The investment is widely spread over the leading renewable energy technology sectors: wind, solar, biofuels, biomass, and fuel cells. Among those, wind, solar photovoltaic, and fuel cells require power electronic converters for grid integration. This thesis investigates advanced control technology for grid integration control of renewable energy sources and STATCOM systems. First, the conventional control mechanism of power converters applied in renewable energy conversion and STATCOM systems is studied. Through both theoretical and simulation studies, a deficiency of the conventional control mechanism is identified. It is found that malfunctions of traditional power converter control techniques may occur when the controller output voltage exceeds the converter linear modulation limit. Then, the thesis proposes a novel control mechanism consisting of a current control loop and a voltage control loop. The proposed control mechanism integrates PID, adaptive, and fuzzy control techniques. An optimal control strategy is developed to ensure effective active power delivery and to improve system stability. The behaviors of conventional and proposed control techniques are compared and evaluated on both simulation and laboratory hardware testing systems, which demonstrates that the proposed control mechanism is effective for grid integration control over a wide range of system operating conditions while the conventional control mechanism may behave improperly, especially when the converter operates beyond its linear modulation limit and under variable system conditions.