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In this article, a novel pulsewidth modulation (PWM) technique is proposed for an existing space vector hysteresis current controller (SVHCC) scheme. A three-level neutral-point-clamped (NPC) inverter is used for dual purpose of shunt active power filtering and solar photovoltaic (PV) power integration to a distribution grid. This dual-purpose NPC inverter utilizes the proposed PWM technique for solving the neutral-point voltage-balancing issue in a unique way. Due to the inherent advantages of the SVHCC, the current control is characterized by fast action and optimal switching. A single reference current required for both filtering and maximum PV power integration is generated using instantaneous power theory, where a diode bridge rectifier load is considered to demonstrate the controller performance while compensating nonlinear current components. Thus, not only a unique space-vector-based PWM technique is adopted for fast-tracking of currents, but also a sliding current error boundary is used for the first time. This sliding technique tackles the dc-link balance issue of the NPC inverter while controlling the output currents simultaneously. The simulation and hardware results prove the aforementioned performance and demonstrate the efficacy of the proposed PWM current controller. [ABSTRACT FROM AUTHOR]

Optimal placement of protective devices and switches in the distribution system improves the system reliability at the cost of increased investment. In this study, a new bi‐directional analytical model has been developed to solve the problem of optimal placement of protective devices and switches in various zones of a distribution system with distributed generation (DG). The model determines the optimal number and locations of reclosers, switches, 'fuse‐save fuses' and 'fuse‐blow fuses' for increasing the system reliability while reducing the investment and outage costs, considering system data uncertainties. For considering uncertainties in load data, failure rates (temporary and permanent) and repair rates, the model utilises three‐point estimate method. The formulated problem has been solved for 69‐bus distribution system and radial distribution system connected to bus 4 of the reliability busbar test system, using genetic algorithm optimisation technique. After analysing the test results, it is concluded that considerable profit to the utility is achieved by optimal placement of protective devices and switches in various zones of the distribution system with DG units. [ABSTRACT FROM AUTHOR]

• Sensitivity analysis has been conducted to address the frequency issue observed during weighted least squares -based state estimation with noisy measurements. • The islanded microgrids state estimation is formulated as a constrained non-linear optimization problem and solved using interior point method. • The low real measurement observability (use of pseudo measurements) issue in islanded AC microgrids is addressed for static state estimation. • The optimization-based state estimation method performance was validated on radial and weakly meshed islanded AC microgrids. Microgrid (MG) with Distributed Generation (DG) increases reliability and resilience of distribution systems (DS). The MGs operating in islanded (standalone) mode are necessary to maintain critical loads during natural calamities and emergencies. The power-sharing between the DGs is achieved with the help of frequency in the absence of main grid. Therefore, in an islanded AC microgrid (IMG), the frequency must be estimated along with bus voltages. This paper initially uses the weighted least squares (WLS) method for state estimation (SE) of IMG, which includes frequency as a state variable along with voltage magnitudes and angles. However, it is observed that the performance of WLS with measurement noises is unsatisfactory; hence, the Sensitivity Analysis has been done to identify the root cause, and the SE problem is reformulated as a constrained non-linear optimization problem. This optimization model is subsequently solved by Interior Point method. The performance of the proposed optimization approach for SE has been validated through extensive simulations on both radial and meshed IMGs. In addition, the estimated frequency of IMG SE has been validated on a daily load curve. Further, the low observability issue of DS has been extended and addressed for IMGs. [ABSTRACT FROM AUTHOR]

Use of Battery in standalone system can offer number of benefits in terms of energy management, reduction of dependency on fossil source and voltage regulation. In this study, a power management technique considering conservation voltage reduction (CVR) along with droop control method is proposed for a standalone system supplied from Photovoltaic (PV) source and battery. The proposed power management scheme ensures that under all operating conditions, the battery is neither overcharged nor completely discharged. It further ensures that under no condition, the power limit of battery charging as well as battery discharging controller is exceeded. The proposed method also aims to minimize the size of overall Photovoltaic battery (PVB) system to reduce the total investment and operation cost considering energy saved achieved by CVR, while satisfying system operational constraints. The proposed method also reduces the number of charging/discharging operations of battery to enhance its life. The validity of the proposed power management scheme has been extensively tested on a European distribution system through PSCAD/EMTDC simulation studies as well as on real time digital simulator (RTDS). The simulation results indicate that the combination of CVR and Droop control can achieve appreciable energy savings. [ABSTRACT FROM AUTHOR]

In this paper, an optimum recloser and fuse coordination scheme is proposed in the presence of multiple distributed generators (DGs) in a radial distribution network. The proposed approach formulates the recloser and fuse coordination problem as an optimisation problem and applies interior point method (IPM) to solve this optimisation problem for obtaining the optimum recloser and fuse settings. The proposed scheme gives a single set of the recloser and fuse settings which is robust enough to be able to coordinate the operations of the recloser and fuses properly without and in the presence of single/multiple DGs in the system. The effect of fault current limiter (FCL) on recloser--fuse coordination has also been studied. The proposed approach has been tested on IEEE 33-bus system for three different scenarios: (i) no DG in the system, (ii) a single DG in the system, and (iii) multiple DGs in the system. Further, the optimum results obtained by IPM have been validated by comparing them with those obtained by modular in-core non-linear optimisation system solver, sequential quadratic programming, particle swarm optimisation, harmony search, genetic algorithm, and differential evolution techniques. The test results prove the robustness and effectiveness of the presented scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a small signal stability constrained distribution system reconfiguration (DSR) methodology under uncertainties associated with the load demand and the power output of the renewable energy based distributed generation. Further, the correlation among the uncertain load demand and among the uncertain DG power output has also been considered. This DSR problem is formulated for minimising real power loss, number of switching operations as well as maximizing the voltage stability margin. This formulation takes into consideration the system’s probabilistic operational constraints such as maximum limit on line current, minimum and maximum limits on bus voltage magnitude, radiality of distribution system and probabilistic small signal stability constraint. A KnEA-PE approach, consisting of a knee point driven method and 3 point estimation method, is then utilized to solve this DSR problem. The effectiveness and feasibility of presented formulation has been tested on IEEE 33-bus, 69 bus and 119-bus distribution systems. The obtained results are compared with those obtained by the multi-objective NSGA-II-based method. [ABSTRACT FROM AUTHOR]

The fault current contribution of inverter based DGs (IBDGs) may affect the operation of protective devices present in the system. Hence, it is necessary to consider the presence of IBDGs in short-circuit analysis of distribution system. A short-circuit analysis approach for unbalanced distribution system with IBDG, incorporating different voltage dependent control modes, is proposed in this paper. Comparison of the results obtained by the proposed method with those obtained by the time domain simulation studies carried out using PSCAD/EMTDC software, shows the accuracy of the proposed technique. [ABSTRACT FROM AUTHOR]

This study presents a methodology for distribution system (DS) reconfiguration in the presence of distributed generations with objectives of minimising real power loss, switching operations as well as maximising the voltage stability margin while maintaining the constraints of bus voltage, branch current carrying capacity and radiality of DS. Furthermore, small signal stability of the system has also been considered in the formulated reconfiguration problem. To obtain the pareto‐optimal solutions of this constrained multi‐objective optimisation problem, knee point‐driven evolutionary algorithm, is applied. In contrast to the non‐dominated sorting genetic algorithm‐II (NSGA‐II)‐based approach, preference is given to the knee points among non‐dominated solutions in selection and tournament mating. Therefore, it maintains better balance between the convergence of the method and the diversity in the population. The method has been tested on IEEE 33‐bus, 69‐bus and 119‐bus radial DSs to demonstrate its feasibility and effectiveness. The obtained results have also been compared with those obtained by the multi‐objective NSGA‐II‐based method. [ABSTRACT FROM AUTHOR]