A Wide-Range Active and Reactive Power Flow Controller for a Solid Oxide Fuel Cell Power Conditioning System

A wide-range active and reactive power flow controller is designed to operate the inverter in pure leading, pure lagging, and the mix with active and reactive power conditions. The key to achieving lagging power flow control is to ensure sufficiently high enough DC bus voltage to avoid duty cycle saturation. The key to achieving precision power flow control for a wide range of power level is to adopt the quasi-proportional resonant controller for the current loop and the admittance compensator to cancel the grid-voltage-induced negative power flow. In this paper, the current loop transfer function has been systematically derived for the controller design purpose. Phasor analysis was adopted to explain the need of dc bus voltage requirement. A 5-kVA grid-tie fuel cell inverter was used as the platform to show current loop controller design and admittance compensation. The proposed controller has been simulated, and the same parameters have been used for a DSP-based controller. Both simulation and hardware experimental results agree well with the theoretical analysis.