Utility integration of PV-wind-fuel cell hybrid distributed generation systems under variable load demands

This paper presents modeling, control and performance of a DC micro-grid connected to the utility under variable load demand and different environmental conditions. This micro-grid consists of 60 kW wind turbine (WT) energy conversion system, 40 kW photovoltaic (PV) panel and 40 kW fuel cell (FC) module, in addition to, DC and AC loads. The WT energy conversion system is controlled by the indirect field orientation control (FOC) method to extract maximum power from the wind. The PV module is controlled to generate the available maximum power using P&O MPPT control considering environmental conditions. The fuel cell, with a current controlled DC/DC boost converter, supplies power only when the load demand exceeds the total power of the WT and PV systems. A bidirectional 6-pulse PWM converter connects the micro-grid to utility using the natural frame control (NFC) technique. It controls the DC bus voltage, power and reactive power transfer to/from the utility according to the available power from the DG units and the total load demand. The various control algorithms are presented to harness the maximum power from the renewable energy sources at different operating modes. In addition, voltage stability and smooth power transfer between the micro-grid and utility are maintained. (C) 2014 Elsevier Ltd. All rights reserved.