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The ongoing efforts by many countries worldwide to increase the share of renewable energy sources in power generation has changed the nature of existing power grids and introduced numerous stability-related issues. To address these problems, more extensive and detailed stability analysis studies are therefore needed. Driven by this need, in this article, we present a passivity-based framework for stability analysis and control design that allows more accurate modeling of both the network and the power system components while facilitating the derivation of completely decentralized stability results. In particular, the proposed approach relies on the formulation of the network as a dynamical multivariable system, which is shown to be passive, even when the network’s dynamic and lossy nature are taken into account. The application of decentralized passivity conditions on bus dynamics is then further exploited, together with the incorporation of more accurate dynamical models for the power system components, to guarantee the asymptotic stability of the interconnected system. Moreover, we discuss the opportunities provided by the proposed approach regarding the incorporation of higher order dynamics, the derivation of significant stability results in a completely decentralized manner and the design of effective distributed control mechanisms. These opportunities are finally verified through the design of a demand-side voltage droop controller and several dynamic simulations on two typical test systems.

Nowadays, we have witnessed a significant increaseof renewable sources across the existing power grids, as aresult of the undeniable need to mitigate the effects of environmental pollution and assist the economic development of countries around the globe. However, due to the lack of rotational inertia and their intermittent nature, renewables have also increased the severity of the occurring disturbances and instability phenomena, which in turn place a demand for more accurate modeling of the network and the power system components. In this paper, we propose a novel network formulation for AC microgrids that allows the consideration of less conservative conditions for the network, while allowing the adoption of higher order inverter-based generation dynamicsand facilitating the stability analysis and control. In particular, we formulate the network as a dynamical multi-input/multi-output system, which we show is both stable and passive, even if the network’s dynamic and lossy nature is taken into account. We then briefly discuss the opportunities and the advantages offered by the proposed approach and provide useful guidelines for a more accurate modeling of power system components.Finally, we verify the proposed network formulation through a numerical application on the Four Machine Two Area Kundur test system and several simulations on typical Medium Voltage (MV) distribution lines.

The continuously increasing penetration of renewables in combination with the unbundling of electricity markets during the last years, introduced serious voltage-related issues across the existing Distribution Systems. In order to overcome these issues operators sought for new, more effective ways to support voltage across distribution feeders and thus to ensure the quality of the electricity supply. Driven by the aforementioned need, in this paper we introduce an effective, demand-side Volt/Var/Watt (VVW) regulation scheme that is able to provide significant voltage support and assist in maintaining acceptable voltage levels across distribution grids. In particular, by considering certain passivity conditions on bus (load) dynamics, we design a VVW control mechanism that is able to regulate the voltage of feeders through the utilization of the available controllable loads. The proposed mechanism can be used either in a centralized or decentralized fashion and its formulation is carried out taking into account both the lossy and the dynamic nature of the distribution network. Its effectiveness is verified through several dynamic simulations on the IEEE 37 Node Test Feeder when either VVW or VV control is employed.

Due to an increase in converter-interfaced renewable generation, power networks are becoming increasingly reliant on power converters, which have contrasting dynamical behaviour to rotating machines with large inertia. This results in new control challenges for the power grid. We focus in this paper on decentralized conditions that can provide stability guarantees for networks with grid-forming converters. In particular, we consider the dynamics of various grid-forming converter configurations and controllers, and show how these can be designed to satisfy an appropriately formulated local passivity condition that provides stability guarantees for the network. Simulations confirm that designs satisfying this property improve the stability and dynamic response of the power network.

During the last decades, significant advances have been made in the area of power system stability and control. Nevertheless, when this analysis is carried out by means of decentralized conditions in a general network, it has been based on conservative assumptions such as the adoption of lossless networks. In the current paper, we present a novel approach for decentralized stability analysis and control of power grids through the transformation of both the network and the bus dynamics into the system reference frame. In particular, the aforementioned transformation allows us to formulate the network model as an input-output system that is shown to be passive even if the network's lossy nature is taken into account. We then introduce a broad class of bus dynamics that are viewed as multivariable input/output systems compatible with the network formulation, and appropriate passivity conditions are imposed on those that guarantee stability of the power network. We discuss the opportunities and advantages offered by this approach while explaining how this allows the inclusion of advanced models for both generation and power flows. Our analysis is verified through applications to the Two Area Kundur and the IEEE 68-bus test systems with both primary frequency and voltage regulation mechanisms included.

Over the last decades, several techniques have been proposed for the optimal placement of FACTS devices across power systems. Although these techniques were shown to improve power system operation, they are usually computationally intractable while having serious inherent limitations. In this paper, we present a novel approach to guide the SVC location identification in order to enhance power system stability. Specifically, the proposed method exploits findings in passivity-based control analysis and design in order to address the most vulnerable-in terms of passivity-buses of the system and consequently the optimal locations for SVC installation. We then show how the incorporation of SVCs at the aforementioned buses can passivate the system and provide guarantees for increased stability. Furthermore, we provide a brief discussion regarding the sizing and the number of required SVC devices in order to guarantee such stability improvement. Finally, we illustrate our results with simulations on the IEEE 68 bus system and show that both the dynamic response and the damping of the system are significantly improved.