The reliability of manufacturing systems modeling and analysis is a complex process. Usually, their behavior is similar to multi-state systems. The configurations of such systems, possibly with Load sharing and other structural dependencies, are designed to provide high reliability/availability. Consequently, this scheme can help companies to improve efficiency and reduce operating costs. Maintenance and part replacement are implemented during operation and utilization to keep their performance. Decision-making about spare ordering is difficult because of the interconnection between spare parts inventory and maintenance strategy. In this paper, the characteristic parameters of spare parts inventory management and maintenance policies are jointly considered for multi-machine systems (manufacturing systems) with different types of dependencies among them (economic, Load-sharing, and multi-state configuration). Two maintenance policies are considered: condition-based and preventive maintenance. The interactions between maintenance policies and spare parts management are considered for determining a manufacturing system’s cost and availability. The influence of these factors is investigated. Load sharing factor and ordering time are more important, and their influence is higher than others.

Increasing DC Loads along with DC nature of distributed energy resources (DERs) raises interest to DC microgrids. Conventional droop/non-droop power-sharing in microgrids suffers from Load dependent voltage deviation, slow transient response, and requires the parameters of the Loads, system and DERs connection status. In this paper, a new nonlinear decentralized back-stepping control strategy for voltage control and Load sharing of DC islanded microgrids is proposed. The proposed method is robust against the Load variations and uncertainty in microgrid parameters and has excellent dynamic and steady-state performance under different operating conditions. The major purpose of the proposed controller is to improve the transient performance of MG with Load variations and constant power Loads (CPLs). The local controller regulates the terminal voltage of DC-DC converter regarding the local quantities without needs to additional data of other system components. For simplicity, the proposed method is simulated with PSIM software on a DC microgrid with two DGs. Different scenarios are studied to present the performance of the proposed method under different operating conditions. The results indicate the capability of the proposed method for voltage control and Load sharing in DC microgrids.

In recent years, the use of photovoltaic (PV) systems has grown significantly in distribution systems and microgrids (MGs). The PV systems are connected to the MG through an interface inverter. However, when multiple PV inverters are paralleled in a MG, Load sharing among PV inverters and their coordinated control to compensate for voltage disturbances become critical challenges. This paper proposes a novel control strategy to guarantee power quality in PV-based islanded MGs. In the proposed strategy, each PV system has a primary control level and a secondary control level. The primary control level of PVs consists of fundamental and harmonic virtual impedance loops that improve fundamental power sharing and distortion power sharing among PV inverters, respectively. In the proposed strategy, the secondary control levels along with the primary controllers are implemented locally to reduce disturbances in the communication system. This control level includes voltage and frequency restoration units and a harmonic compensation unit that generates appropriate control signals and directs the compensation of voltage disturbances in the MG Load bus. The simulation results have confirmed the effectiveness of the proposed strategy for fundamental and non-fundamental power sharing among PVs and increasing power quality in islanded MGs with different resource capacities.

Islanded microgrids are prone to frequent fluctuations in power sharing among distributed generation (DG) units. This is primarily due to the microgrids inherent characteristics, such as Load uncertainty, the lack of accurate control methods, and the variable generation patterns of renewable energy sources. The droop control method combined with a Proportional-Integral (PI) anti-windup technique alone is insufficient for ensuring proper power sharing among DG units. It also struggles to maintain standard voltage and frequency levels. This research proposes a droop control approach based on real power and frequency, combined with higher-order sliding mode control and a single hidden layer feed-forward neural network. The higher-order sliding mode controller is responsible for regulating the voltage, while the single hidden layer feed-forward neural network is employed to control the current. The controllers are designed to ensure equal power sharing among DG units even as the Load varies. Experiments are conducted under three different Loading conditions to evaluate the stability of power sharing among the DG units. To verify the effectiveness of the proposed method, the real and reactive power sharing between DG1 and DG2 is compared using both the existing and proposed controllers across each case. Additionally, to assess the robustness of the controller, voltage and frequency comparisons are carried out under time-varying Load conditions against other controllers. The proposed microgrid is modeled and simulated in the MATLAB/Simulink environment. The simulation results demonstrate that the proposed controllers significantly enhance the performance of the droop controller and achieve equal power sharing among DG units despite Load variations.

This paper, using the signature technique and a generalized Farlie-Gumbel-Morgenstern (FGM) copula function, presents a generic mean residual lifetime (MRL) model for the reliability analysis of a Load-sharing coherent system. The present approach differs from earlier models in that in addition to Load-sharing phenomenon it simultaneously considers the effect of operating conditions on the system. Further, using the developed model and the renewal-reward argument, an age replacement policy is investigated. The proposed MRL model and the behavior of the optimal solution as the model parameters change are illustrated through numerical examples.

Load sharing, as an important challenge in microgrids (MGs), is realized commonly via a droop control method. Conventional droop control methods are not applicable in unpredictable renewable energy sources (RESs) like photovoltaic (PV) and wind turbines (WT) because their output power depends on the weather conditions and can be extracted only if these free sources are available. This paper, considers two operating modes for these types of sources as Maximum Power Point Tracking (MPPT) and DC-link Voltage Control (DCLVC). These power sources usually operate in the MPPT mode unless the Load of the MG drops to a lower level compared to the maximum power generation by RESs, in which case the sources switch to the DCLVC operating mode. This study proposed a method based on enhanced droop control, which helps RESs to choose its control mode locally without communication and share the demand of the AC MG with other dispatchable sources besides supplying its maximum power. The proposed method focused on supplying MG Load from RESs as much as possible and simplicity in implementation. MG frequency helps the proposed controller to select its operation mode. Enhanced control for DC link voltage control is offered for inverter based RESs. The validity of the proposed method is approved by simulations in the MATLAB/SIMULINK environment.