Loop Break Points Research Articles

Three-Phase Distribution Power Flow Calculation for Loop-Based Microgrids

This paper introduces an efficient method for calculating the three-phase power flow in a loop-based microgrid. The proposed method incorporates the conventional Newton-Raphson (NR) iterative approach in a backward/forward sweep (BFS) algorithm for power distribution network analyses. Conventional compensation-based approaches are commonly used to account for loop breakpoints (LBPs) and PV nodes. However, the efficiency and the convergence of traditional solutions deteriorate as the number of loops and PV nodes increases. In this paper, we convert microgrid loops into radial structures by breaking up LBPs, when PV nodes connected to distributed generators (DGs) are regulated with scheduled constant voltage magnitudes. Then, we apply a three-phase BFS-based power flow method with an acceptable convergence for radial distribution networks. Next, we use the NR method for power mismatch corrections at LBPs and PV nodes. Finally, the proposed method is extended to islanded microgrids by introducing the system frequency as a variable. We label the proposed loop-based method an NR-BFS power flow calculation scheme, which combines NR and BFS methods for microgrid solutions. The solution of the proposed algorithm, which signifies the application of the improved BFS method, is applicable to active distribution systems with several loops and DGs. The simulation results demonstrate the efficiency of the proposed method in the loop-based microgrid applications.

Efficient load flow method for distribution systems with radial or mesh configuration

The paper proposes a new and efficient method of solving the load flow problem of a distribution system. The method can be applied to both radial and mesh networks. A mesh network is converted to a radial network by breaking the loops through adding some dummy buses. The power injections at the loop break points (LBP) in the equivalent radial network are computed through a reduced order node impedance matrix. Unlike other methods, the shunt admittances are considered in the proposed load flow algorithm and the effect of load admittances is also incorporated in the calculation of power injections at the LBPs. Because of the inclusion of shunt admittances, the method can also be used to solve the load flow problem of some special transmission networks. Two different networks with various configurations were used to demonstrate the efficiency and convergence pattern of the method. The results obtained by the proposed method were also compared with some other methods.

Plant directionality, coupling and multivariable loop-shaping

We study the multivariable loop-shaping problem when the plant is ill-conditioned and feedback properties at both plant input and output are of interest. Directionality and coupling are described, using the singular value decomposition and principal angles between high- and low-gain subspaces. Our first results are new first-order approximations to feedback properties at one loop-breaking point in terms of the open loop transfer function at that point. Secondly, we study the relation between feedback properties at different loop-breaking points in the event that the plant is ill-conditioned. The nominal relation is studied first. Then robustness is studied, using a first-order approximation to feedback properties at one point with respect to uncertainty at the other. This analysis yields conditions that must be satisfied by feedback properties at one point to prevent poor feedback properties at the other. Finally, these two sets of results are combined to show how feedback properties at both points may be...