THE 12 th LATIN-AMERICAN CONGRESS ON ELECTRICITY GENERATION AND TRANSMISSION - CLAGTEE 2017 1 1 Abstract--Due to the increasing demand for electricity, the quest for cleaner sources of electrical power generation has grown too. Therefore, the study of electrical power systems with renewable energy sources included in transmission and distribution networks is a common interest. The increased penetration of these intermittent sources in the power system requires detailed studies, which access its impacts in the normal functioning of electrical grids. In addition, these integrated systems required improvements in operations and control techniques because the electrical demand satisfaction entails the systems to its load limits. This paper presents a research of voltage stability studies based in the determination of the maximum loading of the electrical power system. The continuation method is applied to the power flow problem to improve the simulations performance. The objective is modeling the system using the continuation power flow and computing the algorithm by parallel technology to decrease the simulation time. Index Terms— Continuation Power Flow, Maximum Loading Point, Parallel Processing, Power System Analysis Computing, Voltage Stability. I. INTRODUCTION ITH the growing demand for electricity, several studies related to the planning and operation of electrical systems have increased its importance to guaranty the system voltage security. In addition to the increased demand, some factors such as the transfer of large amounts of power in the transmission and distribution networks, combined with the economic and environmental requirements conduces the system to operate in stressful conditions. Recent trends towards scale penetration of intermittent renewable energy sources into the grid exacerbates this situation making power systems mucho more vulnerable to stability and security issues. This variability in generation, in addition to the existent load variability requires faster and efficient algorithms for monitoring of the power system. Voltage stability and security monitoring with continuation power flow (CPF) and methods based on the CPF are being incorporated in energy control centers. These methods allow the P-V curve drawing and the computation of the system’s maximum loading point (MLP). This is important for the knowledge of voltage stability margin and modal analysis studies; this point provides information for determining A.D. Vasquez is student of Master’s Degree at the Federal University of ABC, Santo André, SP, Brazil (e-mail: vasquez.daniela@ufabc.edu.br). T. Sousa is professor at the Federal University do ABC, Santo André, SP, Brazil (e-mail: thales.sousa@ufabc.edu.br). effective measures for strengthening the system, since the MLP defines the boundary between regions of stable and unstable operation [1]. The voltage stability has been considered a static phenomenon, due to slow variation of voltage over a long period until it reaches to the MLP and then it decreases rapidly to the voltage collapse. Static voltage stability can be analyzed by using saddle-node bifurcation theory [2]. This paper presents a methodology for voltage stability analysis and it is organized as follows. Section II presents the most relevant aspects about voltage stability and the selected theory to analyze it. The continuation power flow method and the technique used to identify the critical bus for the voltage stability margin calculation are exposed on sections III and IV respectively. On the other hand, Section V presents the test cases, simulations results and its voltage stability analysis. Finally, the conclusions are presented on section VII. II. THE VOLTAGE STABILITY Voltage stability is concerned with the ability of a power system to maintain acceptable voltages at all buses in the system under normal conditions and after being subjected to a disturbance. A system enters a state of voltage instability when a disturbance, increase in load demand, or change in system condition causes a progressive and uncontrollable decline in voltage. Voltage stability problems normally occur in heavily stressed systems. The disturbance leading to voltage collapse may be initiated by a variety of causes but the underlying problem is an inherent weakness in the power system. In addition to the strength of transmission network and power transfer levels, the principal factor contributing to voltage collapse are the generator reactive power/voltage control limits, load characteristics, characteristics of reactive compensation devices, and the action of voltage control devices such as transformer under-load tap changers [3]. There is a need for analytical tools capable of predicting voltage collapse in complex networks, accurately quantifying stability margins and power transfer limits, identifying voltage-weak points and areas susceptible to voltage instability; and identifying key contribution factors and sensitivities that provide insight into system characteristics to assist in developing remedial actions [4]. This information can be obtained from a voltage stability analysis. A. D. Vasquez, UFABC, and T. Sousa, UFABC Voltage Stability Analysis of Power Systems using the Continuation Method W