In this study a new technique of Direct power Control (DPC) is proposed to connect distributed generation sources to the nationwide grid. This technique not only adds power of distributed generation sources to the grid, but also is capable to compensate the reactive and harmonic power of non-linear loads as well. In this study, converters’ voltage references for generating compensation current are directly calculated in synchronous rotating coordinate system in each period of sampling; then, a proper pulse width modulation (PWM) generates the used voltages. The proposed DPC technique has some advantages including simple algorithm of fast dynamic as well as fixed switching frequency and small sampling frequency. The performance of the proposed direct control technique is confirmed by simulation results.

In this paper, a novel risk-based, two-objective (technical and economical) optimal reactive power dispatch method in a wind-integrated power system is proposed which is more consistent with operational criteria.  The technical objective includes the minimization of the new voltage instability risk index. The economical objective includes cost minimization of reactive power generation and active power loss. The proposed voltage instability risk employs a hybrid possibilistic (Delphi-Fuzzy)-probabilistic approach that takes into consideration the operator’s experience, the wind speed and demand forecast uncertainties when quantifying the risk index. The decision variables are the reactive power resources of the system. To solve the problem, the modified multi-objective particle swarm optimization algorithm with sine and cosine acceleration coefficients is utilized. The method is implemented on the modified IEEE 30-bus system. The proposed method is compared with those in the previously published literature, and the results confirm that the proposed risk index is better at estimating the voltage instability risk of the system, especially in cases with severe impact and low probability. In addition, according to the simulation results compared to typical security-based planning, the proposed risk-based planning may increase the security and economy of the system due to better utilization of system resources.

One of the critical components for the efficient operation of single-phase grid-connected converters is the synchronization unit. This paper presents a fast and adaptive phase-locked loop (PLL) structure that ameliorates the dynamic response of the estimated frequency and amplitude for grid-connected single-phase power systems. The second-order generalized integrator (SOGI) with a novel frequency-locked loop (FLL) is utilized which contains a DC offset rejection loop. The proposed method not only eliminates the transient response of the estimated frequency which is produced by FLL in grid voltage phase angle jumps, but also improves the PLL dynamic characteristics. The whole system has been simulated in MATLAB Simulink environment where a very small settling time for the estimated frequency of the FLL has been achieved. Therefore, it will improve the whole dynamic parameters of the system. Based on the simulation results, the settling time for the estimated frequency and amplitude are 22 ms and 10 ms, respectively.

The development of high power grid-connected photovoltaic (PV) systems and their adaptability with grid conditions is a crucial issue. In fault conditions, it can be considered with two sides, first being connected with the grid due to economical problems, second minimizing damages into the grid due to technical problems. The improvement of grid-connected PV systems performance under grid voltage sag (which is the most probable faults) is proposed in this paper. In point of common coupling in case of voltage sag, the active power will oscillating and the grid synchronization system would not work properly, which both are detrimental for unbalanced grid. In order to improve the performance of the exchanged power between the converter and the unbalanced grid, method of Positive-Negative-Sequence Control (PNSC: able to remove oscillation of active power) is suggested. This method is also effective to reduce the oscillations in DC voltage that can be detrimental for DC-link capacitor. In order to track the desired unbalanced reference current generated by PNSC, a proportional–resonant (PR) current controller has been designed. Furthermore, instead of Synchronous Reference Frame Phase Locked Loop (SRF-PLL) which suffers the distorted response in polluted grid, a Double Second-Order Generalized Integrator-Frequency Locked Loop (DSOGI-FLL) is used to synchronize inverter with the grid. Finally, to validate the proposed approach, the whole system is simulated via MatLab/Simulinkâ and simulation results have been compared with conventional method. Results verify the grid condition has improved in comparison with implementing the conventional method.

Generation expansion planning is one of the major modules of power system planning studies, normally performed for the next 10-30 years. Optimal generation expansion planning is a non-linear and limited optimization problem. All solutions are compared to each other in order to reach final optimal solution. Some simplifications are made to reduce the problem dimensions which will not lead to unreal results. In this paper, WASP software package, one of the well known power expansion planning softwares, is used to optimize Iran generation expansion planning. For modeling the power system, WASP uses the probabilistic simulation, while for optimization the dynamic programming method is used. In this paper, the generation system expansion planning is performed from 2009 till 2024 (a duration of 16 years). Finally, the sensitivity analysis is performed on the capital cost and the fuel cost of power plants.

Transient stability in interconnected power systems remains a pivotal concern for operators, particularly amidst the ever-expanding and intricate nature of modern power grids. This study delves into a novel approach to bolstering power grid stability by proposing the implementation of dual-excited synchronous generators (DESGs). Unlike conventional synchronous generators, DESGs feature dual windings on the rotor, strategically positioned to optimize performance and stability. This paper presents a thorough assessment of synchronous generators and DESGs under varying fault conditions, including three-phase to ground, two-phase to ground, and more. Leveraging advanced simulation techniques in Matlab/Simulink, the dynamic behavior and stability of these generators are meticulously analyzed. The results unveil a paradigm shift: DESGs exhibit superior stability and dynamic performance compared to their conventional counterparts across diverse fault scenarios. By harnessing the advantages of DESGs, including enhanced efficiency, the overall stability and reliability of power grids can be significantly augmented. In summary, this study not only sheds light on the critical importance of power grid stability but also presents a promising solution in the form of DESGs. By pushing the boundaries of traditional generator technology, this research paves the way for a more resilient and efficient electrical infrastructure.

Solar panels exhibit non-linear current–voltage characteristics producing maximum power at only one particular operating point. The maximum power point changes with temperature and light intensity variations. Different methods have been introduced for tracking the maximum power point based on offline and online methods. In this paper a new method is presented to improve the performance of maximum power point tracking in off-grid solar panels. The proposed algorithm is a combination of two loops, set point calculation and fine tuning loops. First the set point loop approximates the maximum power using offline calculation of the open circuit voltage. The exact amount of the maximum power will, then, be tracked by the fine tuning loop which is based on perturbation and observation (P&O) method. The proposed method is simulated in Matlab/Simulink environment and experimentally verified using a laboratory prototype. In maximum power point tracking, the effects of frequency variation and disturbance amplitude on dynamic response and steady state performance are examined. Simulation and experimental results are compared with other methods and the effectiveness of the proposed method is evaluated.

In this paper, the operation of hybrid grid-connected inverter has been improved by changing the control scheme. Hybrid grid-connected inverter -HGCI-, which injects active power and compensates power quality problems, needs low DC link voltage because of thyristor-controlled LC filter in the output branch. This structure uses instantaneous reactive power theory which doesn’t perform well in distorted grid voltage condition. Hence, in these conditions, HGCI can’t inject active power and improve power quality. In this paper, Recursive digital filter method is used to improve HGCI in a way that operates in weak grid voltage. Instantaneous reactive power theory and recursive digital filter are both simulated in MATLAB/SIMULINK and the results are presented. Simulation results prove the satisfactory operation of HGCI in weak grid conditions.

Energy management changes the electricity consumption pattern of customers. This change is done to achieve the optimal consumption curve. Using energy management, by reducing consumption in periods, besides the appropriate load curve, it reduces the cost of operation and planning. Electricity supply in traditional networks is done by large power plants that are concentrated in certain places. The generated energy must be transferred to consumption points by transmission and distribution networks. The above-mentioned power system has many problems, among which we can mention the decrease in reliability and availability due to the wear and tear of the electrical system infrastructures and the imposition of high costs of losses in the energy transmission to the load points. In other words, management includes a set of activities that affect the pattern and amount of consumer load. Basically, consumption management programs aim to achieve various goals, the most important of which are improving the efficiency of energy systems, increasing the load factor, reducing the need for investment to build and postponing the construction of new power plants, reducing the effects harming the environment, reducing the cost of electricity supply to customers, compensating for the shortage of supply and reducing the excess demand for electricity, improving the reliability and quality of power, promoting the development of energy economy, creating a culture of saving and effective support for customers pointed out.