Papers by Abdulrahman Alolah
International Journal of Photoenergy
The hexagram multilevel converter (HMC) is composed of six conventional two-level voltage source ... more The hexagram multilevel converter (HMC) is composed of six conventional two-level voltage source converters (VSCs), where each VSC module is connected to a string of PV arrays. The VSC modules are connected through inductors, which are essential to minimize the circulating current. Selecting inductors with suitable inductance is no simple process, where the inductance value should be large to minimize the circulating current as well as small to reduce an extra voltage drop. This paper analyzes the utilization of a multiwinding (e.g., two, three, and six windings) coupled inductor to interconnect the six VSC modules instead of six single inductors, to minimize the circulating current inside the HMC. Then, a theoretical relationship between the total impedance to the circulating current, the number of coupled inductor windings, and the magnetizing inductance is derived. Owing to the coupled inductors, the impedance on the circulating current path is a multiple of six times the magneti...
IEEE Transactions on Energy Conversion, 1990
Dependency of the output voltage and frequency of the isolated self-excited induction generator o... more Dependency of the output voltage and frequency of the isolated self-excited induction generator on the speed, load, and terminal capacitance causes certain limitations on its performance. In this study, the performance of the induction generator under a wide range of operating conditions is examined. It is found that the machine operates only in certain element ranges and that all generated currents and voltages are bounded. It is also shown that a combination of these elements exists that is optimal for maximum power generation
IEEE Transactions on Energy Conversion, 1995
New Developments in Renewable Energy, 2013
Iee Proceedings C Generation, Transmission and Distribution, 1991
A direct method to find the capacitance requirements for a three phase self-excited reluctance ge... more A direct method to find the capacitance requirements for a three phase self-excited reluctance generator under any load or speed is introduced. Expressions for the load angle as well as for the minimum value of the excitation capacitance are derived. It has been found that there is a cut off speed, above which no excitation is possible no matter what the terminal capacitance value. Expressions for the value of this speed under open circuit, resistive and pure inductive loads are also derived and presented.
A novel, simple and reliable digital firing scheme has been implemented for soft starting and spe... more A novel, simple and reliable digital firing scheme has been implemented for soft starting and speed control of three-phase induction motor using ac voltage controller. The system consists of three-phase supply connected to the three-phase induction motor via three triacs and its control circuit. The ac voltage controller has three modes of operation depending on the shape of supply current. The performance of the induction motor differs in each mode where the speed is directly proportional with firing angle in two modes and inversely in the third one. So, the control system has to detect the current mode of operation to choose the correct order for the firing angle of triacs. Three sensors are used to feed the line currents to control system to detect the mode of operation. The control strategy is implemented using a low cost Xilinx Spartan-3E field programmable gate array (FPGA) device. Three PI-controllers are designed on the FPGA to control the system for the three-modes. Simulation of the system is carried out using PSIM computer program. The simulation results show stable operation for different loading conditions especially in mode 2/3. The simulation results have been compared with the experimental results from laboratory prototype.
There is a growing interest in increasing the penetration rate of renewable energy systems due to... more There is a growing interest in increasing the penetration rate of renewable energy systems due to the drawbacks associated with the use of fossil fuels. However, the grid integration of renewable energy systems represents many challenging tasks for system operation, stability, reliability, and power quality. Small hybrid renewable energy systems (HRES) are small-scale power systems consisting of energy sources and storage units to manage and optimize energy production and consumption. Appropriate real-time monitoring of HRES plays an essential role in providing accurate information to enable the system operator to evaluate the overall performance and identify any abnormal conditions. This work proposes an internet of things (IoT) based architecture for HRES, consisting of a wind turbine, a photovoltaic system, a battery storage system, and a diesel generator. The proposed architecture is divided into four layers: namely power, data acquisition, communication network, and application layers. Due to various communication technologies and the missing of a standard communication model for HRES, this work, also, defines communication models for HRES based on the IEC 61850 standard. The monitoring parameters are classified into different categories, including electrical, status, and environmental information. The network modeling and simulation of a university campus is considered as a case study, and critical parameters, such as network topology, link capacity, and latency, are investigated and discussed.
Engineering Science and Technology, an International Journal, 2021
Many studies have analysed the steady-state of the isolated self-excited induction generator (SEI... more Many studies have analysed the steady-state of the isolated self-excited induction generator (SEIG) under balanced/unbalanced conditions. The parallel operation of SEIGs has also been widely studied. However, these analyses have the hidden assumption of an equal number of poles in all the parallel-connected machines. The necessity for expanding the already established power system in addition to integrate different renewable energy sources requires the parallel operation of SEIGs with different numbers of poles. This paper presents a steady-state analysis of parallel-operated SEIGs with different numbers of poles. A mathematical derivation is performed to obtain an equivalent circuit model considering different numbers of poles for each machine. The model is also valid for the case of an equal number of poles. The feasibility of the operation is proven, and the steady-state performance under different conditions are outlined. The analysis is experimentally verified. The computed val...
IECON 2017 - 43rd Annual Conference of the IEEE Industrial Electronics Society, 2017
Cascaded multilevel inverter (MLI) topologies have received an attractive solution for grid conne... more Cascaded multilevel inverter (MLI) topologies have received an attractive solution for grid connected PV system. In this paper, two-cascaded MLI topologies are presented for grid connected PV system. These are seven level cascaded H-bridge multilevel inverter and three phase cascaded voltage source multilevel inverter. In both presented MLI configurations, each PV module is connected to one DC-DC isolated Ćuk converter to achieve best MPPT as well as used for galvanic isolation in order to improve system efficiency. The DC-DC isolated Ćuk converters are cascaded to amplify the DC voltage in order to be used for medium and high voltage systems. On the other hand, the operation of H-bridge switches is that the two upper switches are operating at line frequency while the two lower switches are operating at switching frequency in order to reduce the switching losses. Simulation results show that both system are well functioning in improving the grid power quality. The three phase grid c...
2019 International Conference on Power Generation Systems and Renewable Energy Technologies (PGSRET)
To avoid the environmental impact of the hazardous waste of conventional power generation, green ... more To avoid the environmental impact of the hazardous waste of conventional power generation, green renewable energy sources have been introduced as alternative clean-energy sources. One of these remarkable, exploited sources is wind energy. Self-excited reluctance generators (SERG) are used to convert wind power into electric power. Extensive research studies have analyzed the dynamic, transient, and steady-state performance of SERG. In most of these studies, core loss was neglected. However, different methods have been developed that take the core loss into consideration by adding a resistance (Re) to the model of the generator. The value of Re is considered as either (i) fixed, (ii) linearly proportional to the direct axis magnetizing reactance (Xd), or (iii) a polynomial function of Xd. This paper presents a comparative study of the above-mentioned methods under different operation conditions. The effect of neglecting the core loss on the analysis of the generator is also included.
IEEE Access
The sizing problem of the hybrid energy system (HES) is a crucial issue especially in rural commu... more The sizing problem of the hybrid energy system (HES) is a crucial issue especially in rural communities because any wrong results can mislead the decision makers for building the new HES. Due to the intermittent nature of the renewable energy sources (RES) such as wind and PV, there will be a need for a high storage system and/or a standby diesel engine, which increase the investment, required, and increases the cost of energy (CoE). The use of smart grid concepts like the demand response (DR) using dynamic tariff can improve the system performance, enhance the stability, reduces the size and investments of HES components, reduces the customers' bills, and increases the energy providers' profits. The DR strategy will allow the customers to share the responsibility of the HES stability with the energy providers to maintain the stability of the HES. The DR strategies should be selected to ensure the balance between the available RES and the load requirements. In this article, a novel DR strategy is introduced to model the required change in the tariff with the battery state of charge and its charging/discharging power. The novel DR strategy is used in the sizing of the HES based on techno-economic objectives using three different soft computing optimization techniques. This article introduces modeling and simulation of the smart grid integrated with hybrid energy systems to supply a standalone load for a rural site in the north of Saudi Arabia. The sizing of the HES is built based on minimizing the CoE and the loss of load probability. The novel DR strategy introduced in this article reduced the size of the HES compared to the fixed load technique by 20.66%. The results obtained from this novel strategy proved its superiority in the sizing and operation stage of the HES.
Sustainability
There is a growing interest in increasing the penetration rate of renewable energy systems due to... more There is a growing interest in increasing the penetration rate of renewable energy systems due to the drawbacks associated with the use of fossil fuels. However, the grid integration of renewable energy systems represents many challenging tasks for system operation, stability, reliability, and power quality. Small hybrid renewable energy systems (HRES) are small-scale power systems consisting of energy sources and storage units to manage and optimize energy production and consumption. Appropriate real-time monitoring of HRES plays an essential role in providing accurate information to enable the system operator to evaluate the overall performance and identify any abnormal conditions. This work proposes an internet of things (IoT) based architecture for HRES, consisting of a wind turbine, a photovoltaic system, a battery storage system, and a diesel generator. The proposed architecture is divided into four layers: namely power, data acquisition, communication network, and application...
Control and Operation of Grid-Connected Wind Energy Systems
Energies
The grid integration of large scale photovoltaic (PV) power plants represents many challenging ta... more The grid integration of large scale photovoltaic (PV) power plants represents many challenging tasks for system stability, reliability and power quality due to the intermittent nature of solar radiation and the site accessibility issues where most PV power plants are located over a wide area. In order to enable real-time monitoring and control of large scale PV power plants, reliable two-way communications with low latency are required which provide accurate information for the electrical and environmental parameters as well as enabling the system operator to evaluate the overall performance and identify any abnormal conditions and faults. This work aims to design a communication network architecture for the remote monitoring of large-scale PV power plants based on the IEC 61850 Standard. The proposed architecture consists of three layers: the PV power system layer, the communication network layer, and the application layer. The PV power system layer consists of solar arrays, invert...
IEEE Access
There is a growing interest to increase the grid integration of large-scale wind power farms (WPF... more There is a growing interest to increase the grid integration of large-scale wind power farms (WPF). As most WPFs are located in remote areas where abundant wind resources are available, these sites are lacking communication infrastructures and network coverage which present major obstacles in enabling reliable data transmission between WPFs and their control centers. With the absence of unified communication network architecture, different vendors and manufacturers are developing their own monitoring and control solutions according to their needs. There is a knowledge gap related to the design of WPF communication networks, where the assumptions of available articles do not represent the complete monitoring data from WPF subsystems including wind turbines, meteorological towers and substations. This work aims to design a wireless network architecture for the grid integration of cyber physical wind energy system based on the IEC 61400-25 standard. The proposed architecture consists of four layers: a wind farm layer, a data acquisition layer, a communication network layer and an application layer. Wireless communication technologies outperform conventional wired-based solutions by offering lower costs, greater flexibility and easier deployment. Based on IEC 61400-25 standard, a wireless turbine area network is proposed for collecting sensing data from wind turbine parts, and connected to a wireless farm area network developed for communication between the remote control center and wind turbines. The network performance of the proposed wireless wind turbine internal network (includes the number of sensor nodes, data types and data size) is evaluated considering different wireless technologies (ZigBee, WiFi and WiMAX) in view of end-to-end delay, wireless channel capacity, and data loss. The simulation results show that wireless-based solutions can meet the delay requirements of the IEEE 1646 standard. This work contributes for building a redundant wireless communication infrastructure for remote monitoring of WPFs with scalable coverage and capacity.
International Journal of Photoenergy
Photovoltaic (PV) module behavior is not linear in nature with respect to environmental condition... more Photovoltaic (PV) module behavior is not linear in nature with respect to environmental conditions and hence exhibits nonlinear PV curves. There is only a single point in the nonlinear PV curve at which the power is maximum. Therefore, special methods have been proposed to track this maximum power point (MPP). This paper proposed an intelligent method for MPP tracking (MPPT) based on adaptive neuro-fuzzy inference system (ANFIS) controller. The proposed system consists of a PV module connected to a DC-DC isolated Ćuk converter and load. A MATLAB/SIMULINK-based MPPT model is built to test the behavior of the proposed method. The proposed method is tested under different weather scenarios. Simulation results exhibit the successful tracking of the proposed method under all ambient conditions. Comparison of the tracking behavior of the proposed method with the perturb and observe method is also presented in the simulation results. In addition, a 220 W prototype with the help of dSPACE 1...
International Journal of Photoenergy
Cascaded multilevel inverter topologies have received a great deal of attention for grid-connecte... more Cascaded multilevel inverter topologies have received a great deal of attention for grid-connected PV systems. In this paper, three-cascaded multilevel inverter configurations are proposed for grid-connected PV applications. These are the three-phase cascaded H-bridge multilevel inverter topology, three-phase cascaded voltage-source inverter topology using inductors, and three-phase cascaded voltage-source inverter topology using coupled transformers. Distributed maximum power point tracking (MPPT) of PV modules using perturbation and observation algorithm is used for all presented topologies. In all presented configurations, each PV module is connected to one DC-DC isolated Ćuk converter for best MPPT achievement. Simulation is achieved by using the SIMULINK environment. The simulation results show that the three proposed topologies function well in improving the grid’s power quality. The grid currents are kept in phase with the grid voltage to ensure unity power factor, and the TH...
Energies
A three-phase multilevel inverter topology for use in various applications is proposed. The prese... more A three-phase multilevel inverter topology for use in various applications is proposed. The present topology introduces a combination of a cascaded H-bridge multilevel inverter with a cascaded three-phase voltage source inverter (three-phase triple voltage source inverter (TVSI)). This combination will increase the number of voltage levels generated when using fewer components compared with the conventional multilevel inverter topologies for the same voltage levels generated. The other advantage gained from the proposed configuration is the assurance of a continuous power supply to the grid in case of failure in one part of the proposed configuration. In addition, the voltage stresses on switches are reduced by half compared if each part in the proposed topology is working independently. The comparison of the proposed topology with some conventional multilevel inverter topologies is presented. The proposed topology is built in the SIMULINK environment and is simulated under various loads in addition to being connected to the grid. Phase-shifted pulse width modulation technique is used to generate the required switching pulses to drive the switches of the proposed topology. The inverter is experimentally implemented in the lab, and the switching pulses are generated with the help of MicroLabBox produced by dSPACE (digital signal processing and control engineering) company. The simulation and experimental results and their comparisons are presented to verify the proposed topology's effectiveness and reliability.
Energies
Steady-state, transient, as well as dynamic analyses of self-excited induction generators (SEIGs)... more Steady-state, transient, as well as dynamic analyses of self-excited induction generators (SEIGs) are generally well-documented. However, in most of the documented studies, core losses have been neglected or inaccurately modeled. This paper is concerned with the accurate modeling of core losses in SEIG analysis. The core loss is presented as a function related to the level of saturation. This relation is determined experimentally and integrated into a nonlinear model of the SEIG. The nonlinear model is solved using a mathematical optimization scheme to obtain the performance parameters of the SEIG. A new set of curves describing accurate behavior of the SEIG parameters is produced and presented in this paper. The computed parameters of the model are validated experimentally, and the agreement attained demonstrates the functionality and accuracy of the proposed core-loss model.
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Papers by Abdulrahman Alolah