# The Impact of Distributed Energy Storage on Distribution and Transmission Networks' Power Quality
## 1 Introduction
### Literature Review  
In the overall electric power system, energy storage is critical. Batteries are used by Voltage Source Converters (VSC) for dynamic voltage management, which improves transmission voltage stability [11], except for filling occasional energy supply gaps. Furthermore, because of their huge ramping rates capabilities, Battery Energy Storage Systems (BESS) are often promoted as one of the viable solutions to solve the issues associated with reduced levels of system inertia [12]. Previously, network operators might improve network capacity by using fortification measures such as adding extra conductors or de-rating the network's equipment thermal and current limits. [PERSON] and [PERSON] [13] investigated the use of BESS to alleviate the constraints of thermally constrained transmission corridors. In radial networks, determining the optimal position for integrating and the appropriate amount of ESS in general, as described in [14], has the ability to ensure that power quality remains within expected limits as prescribed by regulators. Similarly, the research work in [15] found that integrating BESS at the optimal place within transmission and distribution networks improves power quality frequency regulation for reducing renewable energy generation unpredictability. The integration of BESS has demonstrated that the dynamic frequency response due to oscillating voltage changes in load conditions is significantly improved in a more interconnected power system, where power is dispatched or imported depending on the peculiar load requirements of these respective systems [16]. While interconnections and distributed grid architecture continue to offer benefits and show great promise in reducing reliance on fossil fuel generation, increasing efficiency, and increasing operational flexibility for all power system stakeholders, unintended consequences are new challenges that network operators must address. Energy storage is widely acknowledged as providing network operators, both transmission and distribution, with the capacity to manage volatility in generated energy and connects end users to power in the voltage characteristics they demand. Recent research suggests that the impacts on power quality performance are largely determined by where these systems are linked to the grid rather than their capacity [17, 18, 19, 20, 21], which is confirmed by analytical studies. In [22], two battery models for two different time resolutions (1 s and 1 min), as well as their respective operation models described in detail. The so-called degrees of freedom are employed in the operation strategy model for the primary control reserve to lower the energy required to recharge the battery. Because of the growing number of consumer-integrated distributed energy storage systems behind distribution networks in power systems that are increasingly adopting smart ideology, distribution network operators recognize that developing intelligent, active control of these energy storage systems is critical to minimizing the impact of their interaction with the grid. The issue of how to actively operate energy storage systems in response to changes in consumer demand is addressed in [23], which proposes the Grid Explicit Congestion Notification Mechanism, which is based on a unified control algorithm that relies on internet protocol (IP) technology between the distribution network and energy storage system. A recent work [24] proposes an energy management system for industrial microgrids connected to the grid, where a BESS can complement the intermittency of the available on-site renewable generation. The results show that the proposed energy management strategy effectively calculates the size of BESS and, at the same time, minimizes the cost of operation for the industrial microgrid. In [25], a control strategy for a BESS is formulated based on two intelligent decoupled controllers. The objective is the system's voltage and frequency restoration, considering a wide range of disturbances and leading to power quality degradation.