Load Flow Analysis of Rural Islanded Hybrid Microgrid

Abstract

Extension of the utility grid to rural villages is not a viable option due to the high cost involved, coupled with low population density and low electrical energy demand. Isolated power systems such as rural hybrid microgrids based on renewables could be a potential solution. Several factors influence the development of these rural hybrid microgrids such as technical and economic issues. Motivated by these facts, the target of this study is to propose an operational load flow algorithm for rural hybrid microgrids by developing a steady state analysis tool for rural islanded hybrid microgrid systems. To achieve this, the root causes of hybrid system design failures were first investigated and identified through field and literature survey. A generalized load flow algorithm was then developed to monitor the steady state performance of the small rural hybrid power systems. Conventional load flow tools found in literature are generally not suitable for the rural islanded hybrid microgrid operating mode. The reason is that none of these tools reflect the rural islanded hybrid microgrid special philosophy of operation. The proposed load flow algorithm adopts the actual characteristics of the rural islanded hybrid microgrid operation where distributed generation units are controlled using droop control methods and, their generated active and reactive powers are dependent on the power flow variables and cannot be pre-specified. Also, the steady-state system frequency is not constant and is considered as one of the power flow variables. The proposed load flow algorithm is generic, where features of the distribution system such as feeder models and load models have been taken into consideration. Simulation studies show that with drooping coefficients, mp and nq at 3% and 2% respectively, the system bus voltages are optimized with a maximum at bus 5 with a p.u voltage of 0.963015 and minimum at bus 3 with p.u voltage of 0.92361 which are comparatively higher than other variations of the drooping coefficients. Also simulation proved that, with a slight increase in the line parameters, there was a further increased in the buses voltage drops. The proposed hybrid system design framework and load flow algorithm can facilitate the successful implementation of hybrid systems for rural electrification