## 1 Introduction  
Electric power distribution system with multifarious topologies, configurations, and characteristics is one of the salient components of a power system. In most developing countries, increasing demand for electrical energy enforces distribution systems for an increasingly expansion and broadening. For any expansion, power energy quality and efficiency require special attention of control, improvement,and management. One of the most effective factors in an electric power energy quality is voltage deviation and stability. Extension of a network length and expansion of topology can be associated with the risk of statutory and standard limit [1]. Kabul is a densely populated and capital city of Afghanistan that distribution networks suffer unstable-rated operation. These networks are extended without length limitation consideration, which demonstrates unstable voltage beyond the statutory range with huge technical and economic losses. In recent years, the government of Afghanistan bounded to retain environmental protection and sustainable development in accordance with the Paris Agreement 2015 (combat climate change), and Sustainable Development Goals (SDGs) 2030. Reform of the energy sector has been part of this endeavor. Afghanistan's distribution networks are the least developed and old-fashioned part of the power system. In addition to the technical and financial losses, shortage of access to electric energy has led to increased utilization of primary energy resources and fossil fuel with high environmental impact. Meanwhile, distribution systems to remote areas are extended without expandability capacity (in local and regional networks) consideration. In priority, it must seriously consider and adopt appropriate solutions. The effective delivery of power to the end users can be achieved by improving reliability, efficiency, cost-effectiveness, and sustainability measures of production and distribution [2]. Various investigations using different optimization techniques, methods, and solutions are conducted to regulate voltage and reduce energy losses in a distribution system. In [3], multiobjective optimization of auto-tap-changer pole transformer with respect to minimizing the voltage deviation of a 16-bus distribution network was tested. In [4], a coordinated control of distributed energy storage system (ESS) with traditional voltage regulators including on-load tap changer transformers (OLTC) and step voltage regulators (SVR) was applied. Authors of [5] proposed data fusion theory to develop a comparative diagnostic method to determine the operation status of on-load tap changers mechanism. A study was carried out in [6] to enhance power quality with automatic tap change in transformer in a smart grid distribution system. In [7], an implementation of a prototype electronic tap-changer instead of mechanical tap-changer was proposed. This method was demonstrated with some shortcomings, such as low operating speed, short lifetime, and heavy size. In [8], the authors employed a nonlinear dynamic model of OLTC, impedance loads, and decoupled reactive power voltage relations to reconstruct the voltage collapse phenomenon. This method aims to determine operation status of on-load tap changers mechanism. Likewise, in [9], a network reconfiguration was carried out over two domains simultaneously: Re-switching strategies and transformer tap-changer adjustments. Similarly, several techniques and strategies for voltage stability enhancement and regulation have been applied, using several case studies under different conditions [10; 11; 12; 13; 14; 15]. This study aims to present a fully solid-state tap-changer solution with a new control strategy and optimal configuration. Over the past decades, power system blackouts due to voltage instability were repeatedly reported; namely, Tokyo blackout on 23 July 1987 and United Kingdom, Sweden, Canada, Denmark, Italy, and the United States blackouts in 2003 [16]. Power system voltage stability has been discussed enough over the past decades.