Optimal Reactive Power Control to Improve Stability of Voltage in Power Systems

Abstract

The current power systems have works near to the marginal voltage stability due to the market performance as well as their weightier operation loadings along with consideration of environmental constraints of transmission as well as generation capacity enlargement. In other words, at the present time wind power has confirmed to be one of the most efficient and competitive renewable resources and therefore, its use is indeed continually growing. Little wind power infiltration planes are generally contained in the current grid networks in view of that it is passively controlled and operated. On the other hand, this statement is no more suitable for immediately after the wind power energy infiltration commences growing, a broad scope of scientific issues can come out, namely: voltage rise, bi-directional power flow, improved power quality issues as well as distorted voltage stability. The additional improvement of electricity construction from renewable resources in a trustworthy as well as consistent system performance is driving transmission as well as distribution control utilizers to employ novel working models that are not presently extant. A serious subject of the demanding status described in the foregoing is the reactive power managing that involves the planning as well as operation deeds that are asked for to be executed to get better voltage profile as well as stability in the power networks. For this reason, voltage stability is a major issue of current power systems. It signifies the capableness of a power system to keep voltage when the required load is boosted. Researches about this kind of instability fact proceed with its control as well as evaluation. The first one designates if a power system runs in the safe operational area, while the second one will carry out essential control actions if a power system gets close to unsafe operational zone. Diverse approaches put forth in the chapter deal with offline and online purposes. The center of attention of this chapter is the second part; it means control of voltage stability. Three major methods have been utilized for voltage stability which are reactive power management, load shedding and active power re-dispatch. Reactive power management signifies the ways designating the place of novel VAR sources and/or settings of the VAR sources that are installed currently and the settings of facilities including on-load tap changers (OLTCs) . Reactive power sources ordinarily consist of synchronous generators/condensers, reactor/capacitor banks, as well as flexible AC transmission systems (FACTS) controllers. It can be classified into two subjects as reactive source programming as well as reactive power dispatch. For reactive programming, the concerned temporal duration is the coming few months or years, and besides considering the optimum milieu of facilities that are installed currently, installation of novel reactive power sources is contemplated. It is performed in offline and online ways. The main purposes of offline reactive dispatch can be found in the duration of the coming few days or weeks, while, another model is carried out in the coming few minutes or hours. Opposing the reactive planning, both online and offline reactive power dispatches only designate the optimum settings of extant facilities. Optimal reactive power flow (ORPF) which is a specific instance of the optimal power flow (OPF) issue is an utterly significant instrument with regard to assured and gainful utilization of power systems. The OPF’s control parameters have a proximate connection with the reactive power flow, including shunt capacitors/reactors, voltage magnitudes of generator buses, output of static reactive power compensators, transformer tap-settings. In the ORPF problem, the transmission power falloff is brought to a minimum and the voltage profile is modified and the operating and physical constraints are satisfied. Note that shunt capacitors/reactors and tap-settings of transformers are discrete variables while and except other variables are continuous. Hence, the reactive power dispatch issue is nonlinear, non-convex has equality and inequality limitations and has discrete and continuous variables.