Power system stability enhancement in the presence of renewable energy resources and HVDC lines based on predictive control strategy M. Darabian ⇑ , A. Jalilvand, M. Azari Department of Electrical Engineering, University of Zanjan, Zanjan, Iran article info Article history: Received 23 August 2015 Received in revised form 5 January 2016 Accepted 27 January 2016 Keywords: Generalized Predictive Control BAT search algorithm High-voltage direct-current (HVDC) Permanent-magnet synchronous generator (PMSG) Stability abstract The renewable energy resources are increasingly employed as new electric power sources. However, their stochastic and uncertain behavior negatively influences the power system stability. In this paper, a hybrid system composed of PMSG-based wind farm, marine-current farm, and PV has been used to supply the network’s load. These resources have been connected to a nine-bus power system through a line- commutated HVDC link. A new control method has been proposed to enhance the damping characteris- tics of power system. This method is based on Generalized Predictive Control (GPC) for design of inverter current regulator (ICR) of HVDC link. In this regard, the BAT search algorithm has been employed for obtaining the best solution for the GPC’s objective function. In order to demonstrate the effectiveness of the proposed GPC-BAT method, the simulations using eigenvalue analysis and root-loci technique are presented. For further investigating the efficiency of conducted approach, a PID controller has been designed for controlling the ICR of HVDC link, and the results have been compared with those of GPC-BAT method. The comparisons have been made through a three-phase short circuit fault on the multi-machine power system in MATLAB software. The evaluations clearly show the effectiveness and superiority of the proposed approach. Ó 2016 Elsevier Ltd. All rights reserved. Introduction Along with the worldwide concerns about the completion of fossil fuels and their greenhouse pollutions, the use of renewable power generations, such as photovoltaic systems [1], wind and marine current farms [2–5] is rapidly increasing. Although these generations are non-polluting and they do not have fuel cost, but, due to the stochastic behavior of their primary energy source, their output power faces some unpredictable fluctuations. If these renewable energy-based power generations are highly penetrated into the power system, they can influence the whole power system stability. A major part of the earth’ surface has been covered with the oceans and seas. In addition, there is powerful wind energy above the seas. To capture the potential energy of the wind above the sea and the tides within the sea, a combination of offshore wind farm (OWF) and marine current farm (MCF) will be advantageous. Both of the OWF and MCF systems are designed to capture the kinetic energy from a kind of flowing mass; therefore, their working prin- ciples are similar to each other. At present, both of the wind and ocean energies are utilized together in several countries [6,7]. However, the integration of high-capacity renewable-energy resources such as OWFs and MCFs may face some problems such as power fluctuations. To settle this problem, a HVDC link which has high power and fast modulation control capability can be used [8,9]. The other renewable energy-based resource which is increas- ingly growing worldwide is the photovoltaic (PV) system. Unlike the OWFs and MCFs, the PV system is located on the land. Due to the potential benefits of the PV system, such as quietness, non- polluting, safety, and low maintenance cost, it is becoming com- petitive with conventional generating units [10,11]. An integrated system composed of large-scale wind, wave, and PV sources can be used to reliably supply part of the required energy in the world. This hybrid system will offer significant advantages such as cost reduction, energy security, and reduction of pollutants [12]. By emerging of these integrated large-scale systems into the power system, some useful strategies are needed for damping of the resulted power fluctuations. For this aim, the PID damping con- troller using a pole placement technique has been regarded as the first choice [13,14]. This technique tries to tune the parameters of http://dx.doi.org/10.1016/j.ijepes.2016.01.050 0142-0615/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: m.darabian@znu.ac.ir (M. Darabian). Electrical Power and Energy Systems 80 (2016) 363–373 Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes