An integrated wind-photovoltaic-battery system with reduced power-electronic interface and fast control for grid-tied and off-grid applications Hamidreza Ghoddami a , Mohammad B. Delghavi a , Amirnaser Yazdani b, * a Department of Electrical and Computer Engineering, Western University, London, Ontario, N6A 3K7, Canada b ECE Department, Room ENG 326, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada article info Article history: Received 17 August 2011 Accepted 23 February 2012 Available online 27 March 2012 Keywords: Control Photovoltaic (PV) systems Power-electronics Pulse-width modulation (PWM) Voltage-mode control Wind power abstract This paper proposes an integrated wind-photovoltaic-battery hybrid system that features a simple power management strategy, requires a lower number of power-electronic converters, and eliminates the need for dump loads. Thus, it is expected to offer a lower cost and higher efficiency, and to enable easier integration with distribution networks, as compared with a set of three stand-alone system. The power management strategy of the proposed hybrid system enables (1) rapid control of the wind and photo- voltaic (PV) power outputs for tightly regulating the battery current, (2) off-grid operation with black- start capability, (3) grid-connected operation, and (4) safe transition from the grid-connected mode to the off-grid mode, and vice versa, without a need for communications with the host grid. Further, the proposed hybrid system is expected to have plug-and-play and power sharing capabilities and, therefore, suited for multi-generator remote electrification systems. The effectiveness of the proposed hybrid system is demonstrated through time-domain simulation studies in the PSCAD/EMTDC software environment. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction In the past three decades, considerable effort has been dedicated to developing the so-called hybrid energy systems which utilize renewable energy resources such as wind, solar, and hydro, to partially or entirely substitute diesel-based electric power genera- tion for remote communities and islands. Amongst various configurations proposed [1], wind-photovoltaic-storage hybrid systems [2e6], are very attractive. The main reason is that wind and photovoltaic (PV) energies exhibit complementary daily and seasonal patterns [7]. Further, their modern power-electronic platforms have risen to considerable maturity and are expected to become less costly as the developments continue. Even though various energy storage technologies can potentially be employed for wind-PV-storage hybrid systems, the majority of the proposed configurations exclusively utilize batteries [2e5]. Batteries are widely available, have a proven track record, and are independent of the site geography. The option seems even more appealing due to decline in battery costs anticipated in view of initiatives led by the electric/hybrid vehicles industry. This paper proposes an integrated wind-PV-battery hybrid system which, as compared to the other configurations [2e5], or a set of three stand-alone systems, features a reduced number of power-electronic converters. Moreover, the proposed configuration employs an integrated power management strategy that enables off-grid operation as well as the operation in the grid-connected mode. This capability, not featured by the configurations proposed thus far, makes the proposed system an option for many communities and islands. The proposed power management scheme enables (1) rapid control of wind and PV power outputs for tight battery charging, (2) off-grid operation with black-start capability, (3) grid-connected operation, and (4) safe transitions from the grid-connected mode to the off-grid mode, and vice versa, without a need for communications with the host grid. The fast control offered by the proposed system also mitigates the need for dump loads. Thus, the proposed hybrid system is expected to bring about lower costs and higher efficiencies, and to enable easier integration with the host distribution network. Further, the proposed hybrid system is expected to possess plug-and-play and power sharing capabilities and, therefore, can be employed in multi-generator remote electrification systems. 2. Structure of the hybrid system Fig. 1 illustrates a schematic diagram of the proposed wind-PV- battery hybrid system consisting of a PV subsystem, a wind subsystem, and an interface subsystem. The three subsystems, detailed in Section 4, share their dc ports with a battery bank which serves as the energy storage medium for the hybrid system. * Corresponding author. Tel.: þ1 416 979 5000; fax: þ1 416 979 5280. E-mail address: yazdani@ryerson.ca (A. Yazdani). Contents lists available at SciVerse ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene 0960-1481/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2012.02.016 Renewable Energy 45 (2012) 128e137