S. Masoud Barakati

Design of a fractional order PID controller using GBMO algorithm for load–frequency control with governor saturation consideration

Load-frequency control is one of the most important issues in power system operation. In this paper, a Fractional Order PID (FOPID) controller based on Gases Brownian Motion Optimization (GBMO) is used in order to mitigate frequency and exchanged power deviation in two-area power system with considering governor saturation limit. In a FOPID controller derivative and integrator parts have non-integer orders which should be determined by designer. FOPID controller has more flexibility than PID controller. The GBMO algorithm is a recently introduced search method that has suitable accuracy and convergence rate. Thus, this paper uses the advantages of FOPID controller as well as GBMO algorithm to solve load-frequency control. However, computational load will higher than conventional controllers due to more complexity of design procedure. Also, a GBMO based fuzzy controller is designed and analyzed in detail. The performance of the proposed controller in time domain and its robustness are verified according to comparison with other controllers like GBMO based fuzzy controller and PI controller that used for load-frequency control system in confronting with model parameters variations.

Reliability evaluation of stand-alone hybrid microgrid using Sequential Monte Carlo Simulation

Adequacy assessment of a stand-alone microgrid including diesel generator (DG), Micro Gas Turbine(MGT), Wind Turbine Generator(WTG), and Photovoltaic(PV) with different configurations is carried out using Sequential Monte Carlo Simulation(SMCS) method. To obtain the output power of WTG and PV, some atmospheric data such as wind speed, solar irradiation, and ambient temperature data are needed. Weibull distribution is used to obtain these data. To obtain the adequacy model of DG and MGT a two-state reliability model is employed. A combination of the two-state reliability model and output power can be also used to build the generation model of WTG and PV. In addition, the generation model of system compares with IEEE Reliability Test System (IEEE RTS) load model and adequacy indices are then achieved. Simulation results corroborate the flexibility of SMSC in risk evaluation of both stable and unstable resources.

Position control of an electro-pneumatic system based on PWM technique and FLC

In this paper, modeling and PWM based control of an electro-pneumatic system, including the four 2-2 valves and a double acting cylinder are studied. Dynamic nonlinear behavior of the system, containing fast switching solenoid valves and a pneumatic cylinder, as well as electrical, magnetic, mechanical, and fluid subsystems are modeled. A DC-DC power converter is employed to improve solenoid valve performance and suppress system delay. Among different position control methods, a proportional integrator derivative (PID) controller and fuzzy logic controller (FLC) are evaluated. An experimental setup, using an AVR microcontroller is implemented. Simulation and experimental results verify the effectiveness of the proposed control strategies.

Voltage sag and swell compensation with DVR based on asymmetrical cascade multicell converter

This paper deals with a dynamic voltage restorer (DVR) as a solution to compensate the voltage sags and swells and to protect sensitive loads. In order to apply the DVR in the distribution systems with voltage in range of kilovolts, series converter as one of the important components of DVR should be implemented based on the multilevel converters which have the capability to handle voltage in the range of kilovolts and power of several megawatts. So, in this paper a configuration of DVR based on asymmetrical cascade multicell converter is proposed. The main property of this asymmetrical CM converter is increase in the number of output voltage levels with reduced number of switches. Also, the pre-sag compensation strategy and the proposed voltage sag/swell detection and DVR reference voltages determination methods based on synchronous reference frame (SRF) are adopted as the control system. The proposed DVR is simulated using PSCAD/EMTDC software and simulation results are presented to validate its effectiveness.

Power quality improvement and mitigation case study using distributed power flow controller

According to growth of electricity demand and the increased number of non-linear loads in power grids, providing a high quality electrical power should be considered. In this paper, voltage sag and swell of the power quality issues are studied and distributed power flow controller (DPFC) is used to mitigate the voltage deviation and improve power quality. The DPFC is a new FACTS device, which its structure is similar to unified power flow controller (UPFC). In spite of UPFC, in DPFC the common dc-link between the shunt and series converters is eliminated and three-phase series converter is divided to several single-phase series distributed converters through the line. The case study contains a DPFC sited in a single-machine infinite bus power system including two parallel transmission lines, which simulated in MATLAB/Simulink environment. The presented simulation results validate the DPFC ability to improve the power quality.

Topologies and Control Strategies of Multilevel Converters

Multilevel converters have been continuously developed in recent years due to the necessity of increase in power level of industrial applications especially high power applications such as high power AC motor drives, active power filters, reactive power compensation, FACTS devices, and renewable energies [1-9]. Multilevel converters include an array of power semiconductors and capacitor voltage sources which generate step-waveform output voltages. The commutation of the switches permits the addition of the capacitors voltages and generates high voltage at the output [8, 10, 11]. The term multilevel starts with the three-level converter introduced by Nabae [12]. By increasing the number of levels in the converter, the output voltage has more steps generating a staircase waveform which has a reduced harmonic distortion [13]. However, a high number of levels increases the control complexity and introduces voltage unbalance problems [10].

Power quality improvement in stand-alone microgrid including fixed-speed wind farm: Role of dynamic voltage restorer

According to the growth of power generated by wind farms and the increased number of non-linear loads, providing a high quality electrical power, should be considered. This paper is addressed the issue of application and analysis of a Dynamic Voltage Restorer (DVR) to enhance the quality of power flows in a stand-alone microgrid, including wind energy conversion systems and the sensitive loads. The wind farm is consist of fixed-speed wind turbines coupled with synchronous machines which the role of DVR in voltage sag mitigation of such a system is simulated in well-known electromagnetic transient simulation program PSCAD/EMTDC version 4.2. The DVR is an effective device to protect the sensitive loads from any disturbance. The regulation of load terminal voltage against any sag/swell distortion is the main purpose of the DVR. The comprehensive results are illustrated to assess the application of DVR as a custom power solution.

Impact of Distributed Power Flow Controller to Improve Power Quality Based on Synchronous Reference Frame Method

Modern power utilities have to respond to a number of challenges such as growth of electricity demand specially in non-linear loads in power grids, consequently, some policies about the power with a higher quality should be considered. In this paper, distributed power flow controller (DPFC) which is similar to unified power flow controller (UPFC) in structure, is used to mitigate the voltage sag and swell as a power quality issue. Unlike UPFC, the common dc-link in DPFC, between the shunt and series converters is eliminated and three-phase series converter is divided to several single-phase series distributed converters through the transmission line. Also to detect the voltage sags and determine the three single-phase reference voltages of DPFC, the synchronous reference frame method is proposed. Application of DPFC in power quality enhancement is simulated in Matlab/Simulink environment which show the effectiveness of the proposed structure.

Fuzzy energy management in electrical vehicles with different hybrid energy storage topologies

In this paper, a hybrid energy storage system (HESS) included a supercapacitor (SC) is proposed for reducing the battery current stress in hybrid electric vehicles. The battery and SC sizes will be optimized based on a desired minimal mileage and a power demand profile, respectively. The proposed energy management strategy will be implemented by fuzzy logic controller (FLC). The proposed strategy offers some advantages, such as less pressure on battery and higher lifetime for it. The proposed strategy is employed for three different topologies of HESS. The simulation results are compared from different points of view, such as current and voltage profiles of topologies, battery current fluctuations, and SC voltage.

Online ANFIS controller based on RBF identification and PSO

Adaptive neuro-fuzzy inference system (ANFIS) is combining a neural network with a fuzzy system results in a hybrid neuro-fuzzy system, capable of reasoning and learning in an uncertain and imprecise environment. In this paper online training of ANFIS is done using radial basis function (RBF) neural network. In this online approach, identification of controlled plant is done, and based on this identification, the weights and coefficients are adjusted timely. Finally, to overcome initialization problem, using Particle swarm optimization (PSO) as an evolutionary algorithm is proposed.