Abstract
Voltage stability margin is ensured through the reactive power resources. In order to generate the reactive power references and ensure the low-voltage ride-through (LVRT) control of a wind farm system based on squirrel cage induction generator, this paper proposed an optimal control approach based on fractional-order (FO) PI-fuzzy-PI (FOPI-fuzzy-FOPI) controller. The proposed control method ensures, also, the demand for active and reactive power predetermined by the transmission system operator (TSO) and satisfies the grid code recommendations. In order to achieve a faster tracking of state variables of the system, the FO operators are optimized using the particle swarm optimization algorithm (PSOA). Using FO operator and PSOA, the responses of the system can be improved. The proposed controller provides additional parameters for better tracking performance and faster convergence can be achieved. Numerical simulation results are presented to analyze the advantages of the proposed control approach to design a physically, realizable controller. The present results are compared with various control methods to show the superiority of the method proposed in this paper.
Highlights
IntroductionThe increased integration of wind energy sources in the grid [1] is leading to the establishment of grid codes.e wind farms (WFs) are more demanded to control the active and reactive power and to participate in the service system. erefore, the research in the field of wind energy conversion systems (WECSs) is oriented towards designing supervision systems with the aim of distributing references of active and reactive powers among wind turbines using the supervision algorithm [2,3,4,5,6].e central and local units of the supervision system are set up for controlling and injecting active and reactive power into the grid. ese powers are produced according to one of the control modes [5].For stable and reliable operation of WECS, most grid codes impose for the grid connected WFs to inject the reactive power during faults (for voltage support) and stipulate that WFs must keep connected to the grid [7, 8].In weakly grids connected WFs, it is not efficient to transfer reactive power over a long-distance transmission line. e reactive power shortage should be compensated locally to avoid losses
The European Network of Transmission System Operators for Electricity (ENTSOE) (Policy 3: Operational Security) indicates that the measurements must be taken to maintain reactive power near the point of consumption to ensure the minimal transfer of reactive power through the network [8]. e reactive power is required for voltage stability of power systems and satisfies the Gird Code Requirements (GCRs) [5]
In recent decades, considerable interest has been shown in fractional calculus through the application of these concepts in different fields of physics and engineering, and the idea of employing fractional calculus in system control loops has Mathematical Problems in Engineering appeared. e fractional-order controller (FOC) [12, 13], such as fractional-order PID controller (FOPID), are used in many applications to overcome the problem related to the dynamic system response and performances. is controller type can be used for renewable system control [14, 15], and it can be used for designing observer-based control [16] and intelligent control system
Summary
The increased integration of wind energy sources in the grid [1] is leading to the establishment of grid codes.e wind farms (WFs) are more demanded to control the active and reactive power and to participate in the service system. erefore, the research in the field of wind energy conversion systems (WECSs) is oriented towards designing supervision systems with the aim of distributing references of active and reactive powers among wind turbines using the supervision algorithm [2,3,4,5,6].e central and local units of the supervision system are set up for controlling and injecting active and reactive power into the grid. ese powers are produced according to one of the control modes [5].For stable and reliable operation of WECS, most grid codes impose for the grid connected WFs to inject the reactive power during faults (for voltage support) and stipulate that WFs must keep connected to the grid [7, 8].In weakly grids connected WFs, it is not efficient to transfer reactive power over a long-distance transmission line. e reactive power shortage should be compensated locally to avoid losses. E wind farms (WFs) are more demanded to control the active and reactive power and to participate in the service system. Erefore, the research in the field of wind energy conversion systems (WECSs) is oriented towards designing supervision systems with the aim of distributing references of active and reactive powers among wind turbines using the supervision algorithm [2,3,4,5,6]. E central and local units of the supervision system are set up for controlling and injecting active and reactive power into the grid. For solving the problem of WF reactive power control at Point of Common Coupling (PCC), various control methods are proposed recently in the literature, such as hierarchal fuzzy controller [9], nonlinear fuzzy controller [10], and fractional-order controller (FOC) [11]. In recent decades, considerable interest has been shown in fractional calculus through the application of these concepts in different fields of physics and engineering, and the idea of employing fractional calculus in system control loops has Mathematical Problems in Engineering appeared. e FOCs [12, 13], such as fractional-order PID controller (FOPID), are used in many applications to overcome the problem related to the dynamic system response and performances. is controller type can be used for renewable system control [14, 15], and it can be used for designing observer-based control [16] and intelligent control system
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