Grid Connected Wind Turbine-Fuel Cell Power System Having Power Quality Issues

By M Gaiceanu et al

This paper shows the topology of the hybrid gridconnected power system and the performances of the front-end three-phase power inverter. At the grid side a three-phase load is available. The renewable sources of the hybrid power system consist of a solid oxide fuel cell (SOFC) and a wind-turbine. This type of combination is the most efficient one. For wind-turbine power conversion an AC-AC back to back converter is employed. The proposed topology benefits of the one common DC-AC inverter which injects the generated power into the grid. The grid inverter maintains a constant DC-link voltage and assures a decoupling control between the active and reactive power. This architecture type diminishes the cost of the power conditioning system. Moreover, due to the power balance control of the power conditioning system (PCS) the bulk DC link electrolytic capacitor is replaced with a small plastic film one. Maintaining DC link voltage at a constant value, the DC current follows the load variations. In order to speed-up the response of the fuel cell DCDC converter current loop, a load feedforward component is added to the reference. A buffer battery must be introduced in order to compensate the slow dynamics of the fuel cell. Thanks to the current control of the DC-DC converter, a low DC link current ripple is obtained. The final power conditioning system has the following advantages: control of the reactive power, minimize harmonic current distortion (up to 5%) offering a nearly unity power factor operation (0,998) operation capability, DC link voltage regulation, fast disturbance compensation capability, high reliability, and low cost. The experimental test has been performed and the performances of the grid power inverter are shown.