load flow

Power-flow (PF) solution is a basic and powerful tool in power system analysis. Distribution networks (DNs), compared to transmission systems, have many fundamental distinctions that cause the conventional PF to be ineffective on these networks. This paper presents a new fast and efficient PF method which provides all different models of Distributed Generations (DGs) and their operational modes (P-V and P-Q nodes) in DNs. This study uses voltage-dependent load model instead of traditional load model (constant P-Q) which is modelled as the combination of a current source in parallel with a constant admittance. This kind of load model is closer to reality and makes the power-flow equations closer to linear conditions. To calculate the angles of the P-V buses, the numerical method (Newton-Raphson method) is applied by separating the PF equations for P-V and P-Q buses. Considering a series of approximations on the angles of these buses, the non-diagonal elements of the Jacobin matrix in Newton-Raphson method are fixed. Hence, the proposed numerical method converges toward an appropriate response in a very low number of iterations and high speed. The voltages of other buses (P-Q buses) are calculated linearly without needing any numerical methods. The presented method proves to be robust and reliable against reconfigured structures and meshed networks. Simulations have been carried out on 14-, 33- and 70-node IEEE test systems and large scale networks such as 6118-buses. The results show that the proposed method is at least 100 and 10 times faster than Gauss-Seidel and Newton-Raphson methods, respectively.

This paper present honey bee mating optimization (HBMO) for optimal power flow (OPF) problems to aim the minimum cost as an objective function and satisfying other constrain such as generation capacity limits, power balance, line flow limits, bus voltage and operating limits of power system and dependent variables. The proposed method has been examined and tested the standard IEEE 30 bus test system. The HBMO method has been demonstrated and compared with the other intelligence heuristic algorithm such as Particle Swarm Optimization (PSO), Shuffle frog leaping algorithm (SLFA) Modified Differential Evolution OPF (MDE-OPF), Simulated Annealing (SA), Improved Evolutionary Programing (IEP), for 30 bus test system. At the end by comparing the results, superiority of presented method has been demonstrated over the mentioned method.

In this paper, a novel algorithm for the load flow analysis problem in an islanded microgrid is proposed. The problem is modeled without any slack bus by considering the steady state frequency as one of the load flow variables. To model different control modes of DGs, such as droop, PV and PQ, in an islanded microgrid, a new formula for load flow equations is proposed. A hybrid optimization algorithm, named (ICGA), is developed, based on imperialist competitive algorithm (ICA) and genetic algorithm (GA) thinking, to minimize the total active and reactive power mismatch in the islanded microgrid. The performance of the proposed algorithm is compared with the GA, Newton-trust and time domain methods. The results provide support for the validity of the paper algorithm.

This paper present honey bee mating optimization (HBMO) for optimal power flow (OPF) problems to aim the minimum cost as an objective function and satisfying other constrain such as generation capacity limits, power balance, line flow limits, bus voltage and operating limits of power system and dependent variables. The proposed method has been examined and tested the standard IEEE 30 bus test system. The HBMO method has been demonstrated and compared with the other intelligence heuristic algorithm such as Particle Swarm Optimization (PSO), Shuffle frog leaping algorithm (SLFA) Modified Differential Evolution OPF (MDE-OPF), Simulated Annealing (SA), Improved Evolutionary Programing (IEP), for 30 bus test system. At the end by comparing the results, superiority of presented method has been demonstrated over the mentioned method.

Conventional passive distribution networks are changing to modern active distribution networks which are not radial.Conventional load flow methods should be modified for new distribution networks analysis. In modern distribution networksdistributed generation (DG) units are embedded with conventional and/or renewable resources. DG units are generally modeledas PV or PQ nodes which inject active power electricity to the network. Modeling of a DG unit is dependent on the operation andits type of connection to the grid. This paper considers the most important new load flow methods for DG integrated distributionnetworks. The methods are analyzed and compared with each other. Every method has advantages and disadvantages in differentconditions. So, comparison of these methods can be useful to select the best method for a typical network. As a result, somesuggestions are proposed to apply the new methods.