Saher Albatran's research while affiliated with Jordan University of Science and Technology and other places

In internal combustion engines, adjusting the air-fuel ratio is essential to control the speed and minimize the burnt fuel. The throttle opening is the actuator to control the air-fuel. A better design for the used/conventional controller can give a better response without additional cost. In this work, the proposed controller gains of the proportional-integral (PI) controller are tuned to enhance the speed in constant and variable drive cycle modes. The tuning process is conducted based on two of the most efficient performance indices used in this field. The performance indices are integral absolute error (IAE) and integral time absolute error (ITAE). The optimization problem is solved using three reliable stochastic optimization algorithms to ensure mature convergence of the solutions, to avoid local optima solutions, and to ensure effective shrinking of the search space. The optimization algorithms are teaching-learning-based optimization (TLBO), particle swarm optimization (PSO), and genetic algorithm (GA). Different simulations are conducted to validate the results. The results are compared with conventional tuning methods regarding the system's time response.

In recent years, several research works have addressed and developed the phase-locked loop (PLL) in single-phase grid-connected converters with different structures and properties. Each has merits and demerits, such as a complex structure, high computational burden, and slow transient response. This paper aims to comprehensively review advanced single-phase PLLs based on transport delay operators to realize signal orthogonality. A deep insight into the PLLs’ small-signal modeling, main characteristics, stability analysis, and loop filter design are provided in this paper. The main advantages and drawbacks are explained for each type of PLL in terms of different performance indexes, such as settling time, estimation error, and ripples in the estimated grid information. This paper also aims to provide optimal tuning and design of the loop filter gains from the large-signal model point of view, including all the nonlinearities, adopting the stochastic optimization method. All simulations are implemented using the MATLAB/Simulink 2018b environment to validate all theoretical analyses of this paper. The sampling and nominal frequencies are set to be 100 kHz and 50 Hz throughout all the simulation studies.

The utility grid disturbances like dc offset and harmonic components can severely affect the estimated variables from the phase-locked loop (PLL), resulting in poor performance of the system relying on it. Therefore, there is an emerging need for well-designed PLL algorithms ensuring robust response against different operating conditions. This paper proposes a simple single-phase PLL algorithm with inherent dc offset and specific harmonic orders rejection capability. Utilizing adaptive time-delay fictitious signal generation. A full mathematical model of the proposed PLL has been provided. The proposed PLL is compared with other filter-based single-phase PLLs, to validate its simplicity and excellent performance.

p>Controlling weak grid-connected systems is very challenging. In transient, frequency and voltage oscillations may lead to voltage and/or frequency stability problems and finally lead to system collapse. During steady-state operation and at the point of common coupling (PCC), voltage degradation and grid voltage background harmonics restrict the inverter's functionality, reduce the power flow capability and cause poor power quality. With weak grid connection, grid impedance variance will contaminate the voltage waveform by harmonics and augment the resonance, destabilizing the inverter operation. In this paper, complete mathematical modeling is carried out and state feedback-plus-integral control is implemented to support the stabilization of the system. The proposed controller is adopted to provide a smooth transient under sudden load change by controlling the injected grid current under different grid inductance values. Furthermore, the proposed control is used to reduce the order and size of the inverter output filter while maintaining system stability. The proposed control has been compared with the conventional proportional integral (PI) controller under different scenarios to validate its effectiveness and to strengthen its implementation as a simple controller for distributed generator applications.</p

This paper investigates the effect of integrating Renewable Energy Sources (RESs) into a system on the Critical Clearing Time (CCT) as a direct transient stability measure. The developed methodology quantifies the stability margin based on the fault clearing time. Moreover, the methodology considers the dynamic system performance under fault conditions as a worst-case scenario to determine the CCT. The proposed technique is a novel numerical methodology presented to study the transient stability of a multi-machine power system with the existence of a RES. Different from the typical solution of the swing equation of a two-machine power system, the proposed methodology numerically solves the swing equation of a multi-machine system. From this, accurate solutions are obtained to determine the optimal penetration level of the RES. Moreover, this work aims to derive an explicit relationship between the rotor angle deviation of the synchronous generator and the penetration level of the RES. Consequently, the CCT associated with the maximum power angle deviation can be determined. The proposed methodology is validated by comparing the results with dynamic simulations using the power-system-simulator (PSS®E) software package developed by Siemens. The IEEE 9-bus system is considered as a benchmark, with the results exhibiting great agreement with the PSS®E results, thus confirming the effectiveness of the proposed methodology.

Pulswidth modulation (PWM) methods were developed to grant the voltage source inverter (VSI) output signal better quality measures. The PWM method that VSI relies on must consider the utilization of the direct current (DC) source, especially when the drive system works in the overmodulation region. In this paper, different zero-sequence harmonic injection PWM methods are proposed. Two essential objectives are optimized by minimizing total harmonic distortion and maximizing the DC bus utilization. All schemes’ results are compared with each other and with some of the commonly used PWM schemes. This paper concludes the usage of third, ninth, and fifteenth harmonic injections and any combination of them to reach a new PWM method that overtakes the disadvantages of other methods. Meanwhile, it provides a handy tool to operate VSI optimally. Ultimately, this work concludes to what extent is the zero-sequence injection is helpful. The work is evaluated experimentally, and the practical results match the simulation outcomes.

A two-step efficiency optimization of a three-phase voltage source inverter with series R damped LCL filter is proposed. The first optimization step aims to find the optimal parameters of the series R damped LCL filter at rated load conditions. The objective function of step-one is to minimize the values of the passive elements of the filter-stage. Afterward, the magnetic cores of inductors are thoroughly designed using soft magnetic powder materials. This design is proposed to specify the smallest core-size required based on the value of the inductance found in step-one of the optimization. The second optimization step aims to optimally select the switching frequency of the inverter-stage considering load variations. This optimization is based on the optimized filter-stage parameters. The proposed objective function of step-two aims to minimize the power losses in the inverter-stage and filter-stage while limiting the harmonic-levels at the point of common coupling. Detailed loss-formulation including filter-stage core and copper losses is thoroughly presented. Teaching-learning-based optimization algorithm is adopted to perform the optimization problem. Experiment and simulation are done to justify the proposed optimization procedure.

Interfacing a weak grid imposes challenges on distributed generators (DGs). These challenges include transient frequency and voltage dynamics that can destabilize the system. Accordingly, this paper investigates the grid stiffness based on different scenarios and the dynamics of a grid feeding DG connected to a weak grid. Moreover, the dynamic effects of the physical and control parameters on the system’s stability are deeply analyzed and evaluated. Specifically, complete mathematical models and graphical representation are carried out to precisely examine the impact of the system parameters on the stability and performance of the DG. Therefore, stable deployment of renewable energy resources into power networks can be achieved as well as an efficient and robust performance of DGs can be ensured when connected to weak grids. The obtained results show the importance of the performed study in optimal sizing and designing the output filter of the inverter and the impact of tuning the control parameters on the system dynamics. As a result, a proper design of system physical and control parameters can be accurately achieved considering all factors affect the system performance. The paper also conducts detailed and elaborated analyses and simulations to evaluate the performance of a PI-controlled RC damped inverter connected to a weak grid. The proposed filter design of the interfacing inverter can significantly extend the integration of DGs into microgrids without requiring complex control schemes or oversized components.

This paper proposes an effective way to eliminate the reactive power-sharing errors that is compatible with droop control. The virtual synchronous generator technique was employed to estimate and compensate reactive power-sharing error. The basic idea is to inject a disturbance at active power loop for all parallel inverters from the central controller simultaneously. At the same time, the resultant signal from active power loop is processed through an integral term to fix reactive power errors. This method, in contrary to the virtual impedance method, doesn't depend on the microgrid parameters or configurations. Consequently, it supports the "plug-and-play" trait of modern microgrids. Moreover, stability and fast response are guaranteed using the proposed strategy. To ensure the applicability, comparisons with state of the art research are made in terms of six common scenarios. The comparison study considers the time of compensation, impact of active power change during compensation, frequency robustness, the effect of feeder impedances mismatch, the effect of local load, and the impact of having inverters with different capacities. Ultimately, the standard deviation, the approximation error, and the range are the performance indices used to have a fair comparison.

Model order reduction simplifies the understanding of a given system and minimizes the simulation studies computational burden. A new order reduction method that depends on a predetermined normalized error of the transient performance indices is introduced. Ten percent and five percent error criteria in modeling and analyzing the transient performance of the third-order system are considered to have an accurate study. All sufficient special conditions and general rules required to achieve precise order reduction are determined. This work focuses on underdamped third-order systems without zeros. Third-order systems with three real poles are also analyzed for the study completeness. The relationships between the characteristic equation parameters are identified and the range in which the reduction is accurately valid is clearly specified. Each approximation or order reduction is studied separately in terms of the transient response characteristics: rise time, settling time and percentage overshoot. The comparison shows the effectiveness of the proposed method.