Voltage Control In Smart Grids Research Articles

Plug-and-Play Model Predictive Control for Load Shaping and Voltage Control in Smart Grids

This paper presents a predictive controller for handling plug-and-play charging requests of flexible loads in a distribution system. Two types of flexible loads are defined: 1) deferrable loads that have a fixed power profile but can be deferred in time and 2) shapeable loads that have flexible power profiles but fixed energy requests, such as plug-in electric vehicles. The proposed method uses a hierarchical control scheme based on a model predictive control formulation for minimizing the global system cost. The first stage computes a reachable reference that trades off deviation from the nominal voltage with the required generation control. The second stage uses a price-based objective to aggregate flexible loads and provide load shaping services, while satisfying system constraints and users’ preferences at all times. It is shown that the proposed controller is recursively feasible under specific conditions, i.e., the flexible load demands are satisfied and bus voltages remain within the desired limits. Finally, the proposed scheme is illustrated on a 55 bus radial distribution network.

Review of Challenges and Research Opportunities for Voltage Control in Smart Grids

In this paper, we review the emerging challenges and research opportunities for voltage control in smart grids. For transmission grids, the voltage control for accommodating wind and solar power, fault-induced delayed voltage recovery, and measurement-based Thevenin equivalent for voltage stability analysis are reviewed. For distribution grids, the impact of high penetration of distributed energy resources is analyzed, typical control strategies are reviewed, and the challenges for local inverter Volt–Var control is discussed. In addition, the motivation, state-of-the-art, and future directions of the coordination of transmission system operators (TSO) and distribution system operators (DSO) are also thoroughly discussed.

A Command Governor Approach for the Voltage Control in Smart Grids with Distributed Generation and Storage Devices

High penetration of Distributed Generation (DG) plants in Medium Voltage (MV) / Load Voltage (LV) power grids may lead to abrupt voltage raises. Typical critical scenarios are represented by either low demand conditions or high power production from renewable sources. Traditional approaches used to face such a situation involve both the disconnection of the distributed generators and the curtailment of the generated power leading to several disadvantages. However, new technologies allow an active orchestration between some controllable devices of the grid, e.g. distributed generators, MV/HV transformers, storage devices in order to maintain relevant system variables within prescribed operative constraints in response to unexpected adverse conditions. This work addresses the online management of distributed generators and storage devices. The approach is based on Command Governor (CG) ideas and is based on the resolution at each time instant of an optimization problem containing explicit constraints related to voltage bounds and operational limits of adopted devices.

Multicast Routing for Decentralized Control of Cyber Physical Systems with an Application in Smart Grid

In cyber physical systems, communication is needed for conveying sensor observations to controllers; thus, the design of the communication sub-system is of key importance for the stabilization of system dynamics. In this paper, multicast routing is studied for networking of decentralized sensors and controllers. The challenges of uncertain destinations and multiple routing modes, which are significantly different from traditional data networks, are addressed by employing the theories of hybrid systems and linear matrix inequalities, thus forming a novel framework for studying the communication sub-system in cyber physical systems. Both cases of neglible delay and non-negligible delay are discussed. The proposed framework is then applied in the context of voltage control in smart grid. Numerical simulations using a 4-bus power grid model show that the proposed framework and algorithm can effectively stabilize cyber physical systems.

Alternative ways for voltage control in smart grids with distributed electricity generation

SUMMARY In this paper, we have studied different strategies for managing voltage fluctuations in distribution networks originating from decentralized electricity generation systems (DEGS) or increased loads, which are highly important issues in the smart grid context. A starting point for system design when increasing load or local power production could be to limit the voltage fluctuations to ±5% from nominal voltage. Strategies to regulate voltage include cable improvement, transformer management, Demand side management, storage, and line interconnection. We present a mathematical model applicable for both a static and dynamic analysis to quantify effects from these measures, though the best solution will depend on local conditions and needs to be determined case by case. Combining several voltage control options simultaneously may lead to further positive effects. Strategies when doubling the load and increasing DEGS production to twice the electricity demand were analyzed here in detail. It also needs to be pointed out that other factors related to power quality besides voltage may need consideration when large amounts of DEGS are integrated to distribution networks. Copyright © 2011 John Wiley & Sons, Ltd.