Journal of Operation and Automation in Power Engineering
Volume:13 Issue: 2, Summer 2025

Microgrid operators (MGOs) try to restore as much demand as possible when they are faced with electrical power outages corre-sponding to extreme events. This work suggests an outage management strategy (OMS) to improve microgrid resilience by using two optimal actions that are distribution feeder reconfiguration (DFR) and scheduling of the distributed energy resources (DERs). Later happening a line fault, the radial network topology is determined by the proposed model using an evaluation of the inci-dence matrix. The presented work handles the uncertain behavior of non-dispatchable DERs and the electrical loads which model by the robust optimization approach. To expand the flexibility of the proposed model, the demand response program (DRP) is treated as the curtailed demand. The aim of optimization is the minimization of the total cost for dispatchable DER operation and electrical load decrease. The recommended robust linear problem (RLP) model is simulated by the CPLEX solver in GAMS software. Applying the suggested model in the 69-bus unbalanced test system demonstrate that the proposed model averagely decreases total operation cost and execution time by 10.62% and 22.23% on all scenarios in comparison with the de-terministic model.

The widespread adoption of microgrids in electric power systems has brought numerous advantages such as decentralized control, reliability, cost-effectiveness, and environmental benefits. However, one of the most critical challenges faced by islanded microgrids is ensuring frequency and voltage stability. This paper addresses these stability issues that arise when microgrids operate independently, disconnected from the main network through the point of common coupling (PCC). These microgrids rely on renewable resources like photovoltaic (PV) systems, wind turbines, and energy storage systems, which often require DC to AC conversion through inverters to simulate synchronous generators. To overcome the frequency and voltage stability challenges, this research utilizes the droop control technique to regulate the active and reactive power of distribution generators (DGs). The droop control technique is implemented and simulated using MATLAB software, specifically employing a multi-DC bus-based inverter. The simulation results demonstrate that the DGs successfully supply the required total power to meet load demands while maintaining frequency and voltage stability. Through the droop control technique, active and reactive power sharing is achieved, ensuring stability at nominal values. The DGs can effectively maintain a constant power profile at desired values, even in the presence of static and dynamic loads.

The microgrid (μG) is an integration of distributed generation and local loads with energy storage system. Cost minimization is one of the main objectives in modern power systems.Economic dispatch(ED) is a fundamental problem related to μG and the conventional grid. Economic dispatch(ED) provides the optimal output of generators in order to reduce the total operating cost. Emission dispatch (EMD) is one of the other major problems associated with CG. The emission dispatch (EMD) solution provides the optimal generator operation to reduce harmful pollutants for a specific load demand. Multi-objective economic emission dispatch (MEED) provides a compromise between ED and EMD. In this paper, two test systems have been proposed. Test system one consists of Six CG. Static ED, EMD, and MOEED analysis has been provided for test system one. Test system two consists of four CG, One wind turbine generator (WTG), and one photovoltaic module (PVM).This paper intends to provide sensitivity analysis and uncertainty regarding the curtailment cost of RES. CPLEX solver in GAMS has been proposed to optimize the three fundamental problems. Comparative study and sensitivity analysis show optimal results, and the GAMS solver provides a more comprehensive framework. Reduction in cost due to uncertainty in ED is 9.58% as compared to 9.7% for test system two. The cost has been reduced in MEED by 9.33% as compared to 9.46%. MEED comparison shows the increment in cost of 2.66 %, but the emission is reduced by 18.98 % for test system two.

Low Switching-based  v/f -controlled induction motor (IM) drives are incredibly susceptible to torque harmonics and their Vibrations. These consequences lead to intensifying losses, damage drive, and can even turn out into shaft failure of high power/speed drives. In literature, numerous control algorithm based on pulse width modulation (PWM) has been reported for low switching-based IM drive. Nowadays, standard PWM techniques (Sinusoidal PWM (S-PWM), selective harmonic elimination (SHE) PWM) are being used as the solution in low-switching IM drives. In this manuscript, the proposed synchronous reference frame (SRF) based P-PWM scheme is analytically evaluated to minimise the torque harmonics and its vibration in low switching IM drive. In this paper, a specific case of four switching angles per quarter cycle (Sq=4) is considered in which the optimized switching angles are obtained while maintaining the quarter wave symmetry (QWS) and half wave symmetry (HWS) nature of the waveform. The proposed approach is validated on 1hp IM drive and compared with S-PWM and SHE-PWM with respect to torque spectrum and vibration under No Load and different loading conditions. Real-time waveforms are recorded using the SRF-based P-PWM technique and the TYPHOON-HIL hardware setup to demonstrate the superior performance of the SRF-based P-PWM in comparison to S-PWM and SHE-PWM, in terms of lower torque harmonics and their vibrations.

Recent grid codes require a high voltage direct current (HVDC) converter station remains connected and provide reliable operation under various faults. An improved clamp-double submodule (CD-SM) is introduced in this article, which belongs to the modular multilevel converter (MMC) topologies proposed for high voltage direct current (HVDC) systems. The proposed submodule (SM) topology features a reduced number of control switches, lower converter level faults, and DC fault-blocking capability compared to the conventional submodule topologies. A CD-SM consists of five $IGBT$s, two diodes, and two floating capacitors, where capacitor voltages are maintained according to the binary geometric propagation (GP) ratio which enables it to generate a maximum four-level output voltage. The hybrid pulse width modulation (PWM) technique is used to generate desired switching pulses for a converter and the associated voltage balancing control technique maintains the power exchange between the converters. In this article, the dimensioning of the proposed MMC converter, and its performance under different fault conditions is discussed in detail. Further, a quantitative comparison with other submodule topologies in terms of dc fault-blocking capability, output voltage level, and device count is discussed. Simulation in MATLAB/Simulink and their results validate the effectiveness of the proposed topology for MMC based HVDC system.

In recent years, due to rising social welfare, the reliability has become one of most important topics of modern power network and electricity companies try to provide the electric power to the consumers with minimal interruptions. For this purpose, the electricity companies to improve the reliability of the power system can utilize different techniques. In this paper, new developments occurred in electricity industry including integration of large-scale renewable resources, integration of large capacity energy storage systems, integration of combined heat and electricity units into power network and demand side response plans are taken into account, and these events impact on power network reliability is assessed. Power networks are affected with integration of renewable resources. Multi-state reliability models for renewable generation plants are obtained, in the paper. Suitable number of states in the proposed reliability model is selected by calculating XB index. Besides, fuzzy c-means clustering approach is utilized for determining probability of states. For study impact of energy storage systems with large capacity on power network reliability, load model is modified. To investigate effect of combined heat and power plants on power network reliability, failure of composed elements and produced thermal power are considered in reliability model of these plants. To evaluate demand side response impact on reliability of power network, the load model is modified. The effectiveness of the proposed techniques on the reliability enhancement of power network is satisfied using numerical results performed on reliability test systems based on the suggested methods.

Although the presence of clean energy resources in power systems is required to reduce greenhouse gas emissions, system security faces severe challenges due to its increased intelligence and expansion, as well as the high penetration of renewable energy resources. According to new operating policies, power systems should withstand subsequent single contingencies. Also, the effect of electrical and structural characteristics must be considered in power system security assessment. Thus, this paper introduces a comprehensive risk-based approach that quantifies the impact of contingency-induced variation in topology by using complex network theory metrics. Then, it identifies elements that surpass security limitations and eliminates them to execute cascading outage analysis via AC power flow. Lastly, wind power uncertainty and contingency probability are multiplied by the linear combination of electrical and structural consequences, and security status is assigned to each contingency based on its risk value. Additionally, simulations are carried out on modified 118 and 300 bus IEEE systems, and the extensive results are utilized to demonstrate the effectiveness of the proposed methodology.

Conventional overcurrent protection schemes may not be sufficient to provide the complete protection of microgrids, especially in the islanded mode (ISM) of operation. Directional overcurrent relays (DOCRs) in microgrid may malfunction due to significant changes in fault current level and change in topology from grid-connected mode (GCM) to ISM. The novel contribution of this study is to determine the optimal settings of time-voltage-current-based dual-setting DOCRs with mixed inverse characteristics, valid in both GCM and ISM, without any miscoordination of relay pairs. The relay coordination problem is formulated as a mixed integer non-linear programming (MINLP) problem and optimally solved using an improved environmental adaption method (IEAM). The proposed relay coordination scheme has been tested on a 7-bus microgrid, the low-voltage section of the modified IEEE-14 bus benchmark system. The performance of the proposed protection scheme has been compared with the existing schemes, considering conventional DOCRs, time-voltage-current-based DOCRs, and dual-setting DOCRs.