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We present an out-of-equilibrium thermodynamics method for lithium-ion batteries' (LIB) state-of-charge (SOC) assessment during ultra-fast charging using the non-linear voltammetry (NLV) algorithm. NLV consists of applying short constant voltage pulses followed by a very short relaxation period. The out-of-equilibrium open-circuit voltage during the relaxation period is addressed to as pseudo-open-circuit voltage (p-OCV). From the p-OCV temperature dependence, pseudo-entropy and pseudo-enthalpy are determined, denoted as p- Δ S and p- Δ H , respectively. It is found that the SOC follows the "Yazami theorem", which theorizes that SOC is a linear function of p- Δ S and p- Δ H. Out-of-equilibrium p- Δ S and p- Δ H together with incremental capacity (IC) analysis reveal different steps during the charging process, which are assigned to phase transitions in the LIB's anode and cathode materials. • Estimation of out-of-equilibrium thermodynamics during the fast charging process. • Analysis of non-linear voltammetry fast charging under various operating conditions. • High accuracy SOC assessment from out-of-equilibrium thermodynamics. • Battery temperature prediction during NLV ultra-fast charging. [ABSTRACT FROM AUTHOR]

Due to the scarcity of measurement devices, distribution systems often suffer from unobservability. The recent expansion of smart meters (SMs) provides the means to enable system observability. To ensure continuous situational awareness of distribution grids, strategic planning of advanced metering infrastructure (AMI) is crucial. However, conventional AMI planning approaches only consider the economically optimal placement of communication devices without considering the need for observability even in case of failures. To address this challenge, this paper proposes a wireless AMI network planning framework that guarantees the observability of distribution grids in the face of potential communication failures. Specifically, given the failure scenario, a closed-form observability criterion is formulated and its observability fortification strategy is derived, based on which the AMI network planning problem is formulated as an integer linear programming (ILP) problem. In addition, a heuristic decomposition technique is applied to the ILP problem in order to address the scalability issues of large-size networks. Finally, case studies demonstrate the robustness and effectiveness of the proposed AMI system planning framework. The findings of this work assist distribution utilities in developing a reliable and economical AMI, while providing guaranteed situational awareness of their assets. • A wireless AMI network planning framework to ensure observability of distribution grids against communication failures. • A closed-form observability criterion is formulated to assist the fortification strategy. • The fortification strategy provides communication routes with flexible redundancy. • A heuristic decomposition technique is proposed to address scalability issues of large networks. [ABSTRACT FROM AUTHOR]

• Develop a detailed power model of a GFM system for P-δ and P-ω droop controls. • Study the detail features of the power coupling and stability of GFM under both droop controls. • Reveal the critical power coupling and stability difference between P-δ and P-ω droop controls. • Propose a novel scheme for improvement in stability and power coupling issues of GFM system. The power coupling issue in grid-forming converters (GFMs) is an emerging concern within power systems dominated by inverter-based resources. Specifically, the phase difference between two rotational frames, i.e., system/grid and controller frames, has not been associated with the power coupling effect. It is demonstrated that such phase difference causes interaction between the inner and power control loops. To this end, we first developed a detailed power model of a GFM system to study the sensitivity of control parameters against coupling issues. In particular, we found that the inner voltage control loop could impact the system's stability. In addition, the controller-generated virtual inductance and the cut-off frequency of the low-pass filter trigger a destabilizing effect for GFM using P-δ control compared to P-ω droop control. This is due to the phase difference and control loops interaction. As a result, the typical virtual inductance becomes inadequate in suppressing the coupling for P-δ droop control. Subsequently, a q-axis-based virtual impedance combined with phase difference compensation is proposed. It extends the range of stable control parameters and minimizes the power coupling for both types of droop controls. Experiments were conducted to verify the theoretical analysis and the proposed scheme. [ABSTRACT FROM AUTHOR]

Demand-side resources (DSR) have been considered as flexible frequency reserve providers in power systems. Given their uncertain nature in the reserve deployment and the load recovery periods, it is necessary to consider these uncertainties in the frequency dynamic constrained unit commitment (FDUC) model. This paper proposes a two-stage distributionally robust FDUC model to minimize the worst-case cost expectation under a set of probability distributions of DSR uncertainties, which are restricted by the supports and moments generated from statistical information. In addition, the cumulative frequency deviation during the entire regulation period is exploited as a frequency dynamic criterion. Particularly, it can quantify the regulation efficacy of the reserve resources with diverse frequency response characteristics, such as the dead-band time and the reserve delivery time. Simulations based on the IEEE 118-bus and 300-bus systems validate the effectiveness of the proposed method in hedging against the DSR uncertainties. • A frequency dynamic unit commitment model considering uncertain demand-side resources (DSR). • The uncertainty of demand-side resources is captured by a moment-based ambiguity set. • A criterion reflecting the efficacy of different frequency regulation resources. • The load recovery property of demand-side resources diminishes their fast response advantage. • below is the edited version: • A frequency dynamic unit commitment model with uncertain demand-side resources. • The uncertainty of demand-side resources is captured by a moment-based ambiguity set. • A criterion reflecting the efficacy of different frequency regulation resources. • Load recovery diminishes the fast response advantage of demand-side resources. [ABSTRACT FROM AUTHOR]

• A method for microgrid decomposition into a set of equivalent two-bus systems was proposed. • The method proposed metrics graph for stability assessment is based on the network graph and applicable for any grid topology. • The addition of any line to the inverter-based microgrids or decreasing the impedance of any of the existing lines leads to stability margin reduction. • The method allows identifying parameters of the system that should be duly modified to drive the system back to the stability region. In this paper, we investigate the stability properties of inverter-based microgrids by establishing the possible presence of the so-called critical clusters - groups of inverters with their control settings being close to the stability boundary. For this, we consider the spectrum of the weighted admittance matrix of the network and show that its distinct eigenvalues correspond to inverter clusters, whose structure can be revealed by the corresponding eigenvector. We show that the maximum eigenvalue of the weighted admittance matrix corresponds to the cluster, closest to stability boundary. We also establish that there exists a boundary on the value of this eigenvalue, that corresponds to the stability of the overall system. Thus, we make it possible to certify the stability of the system and find the groups of inverters in which control settings are closest to the stability boundary. [ABSTRACT FROM AUTHOR]

A distributed economical coordinator is presented to maximize the social welfare for distributed generations, storage units, and consumers within a DC microgrid. This is realized through a two-layer control framework, which only requires information exchange among neighboring units. The economical coordination is then established using a consensus-based algorithm for computing the economical correction terms among the participants. Furthermore, power sharing among the distributed generations is achieved using a modified droop controller. The control parameters are determined based on the mathematical analysis of the two-layer control framework, ensuring the optimal power sharing among all participants. Finally, numerical case studies demonstrate the effectiveness of the proposed framework. • Proposed a consensus-based optimization approach to maximize the social welfare in a DC microgrid. • Proposed a two-layer control framework to achieve real-time optimal power sharing. • Demonstrated the superiority of the proposed approach from the perspective of number of required iterations. [ABSTRACT FROM AUTHOR]

Traditional virtual power plants (VPPs) with fixed resource composition and coordination strategies struggle to cost-effectively exploit the flexibility of large-scale resources for adapting variable regulation requirements and resources characteristics. To this end, this paper proposes a dynamic aggregation mechanism to flexibly select and coordinate individual resources for forming aggregators according to grids regulation requirements and resource characteristics. The proposed mechanism is operated through a two-stage dynamic aggregation model comprising resource selection and coordination. Considering the two-stage dynamic aggregation model is a combinational optimization problem with high computational complexity, the submodular optimization method is utilized to swiftly address this problem. First, the complementarity and submodularity of the dynamic aggregation process are formulated to elaborate how the aggregation regulation characteristics (ARCs) evolve with flexible resource composition and coordination. Next, a submodularity-based algorithm is developed to promptly solve dynamic aggregation model under three scenarios, where aggregation operators focus on the resources quantity, quality, and cost-effectiveness, respectively. The polynomial computational complexity of the proposed algorithm has also been evaluated. Simulations using the IEEE 39-bus (New England) system consists of 10,000 flexible resources were executed to assess the submodularity approach. The proposed algorithm demonstrates superior computing speed and better performance guaranteed results (90%, 97%, 90% in three scenarios) compared to other methods—making it more suitable for implementation in practice. • The complementarity and submodularity of dynamic aggregation process are revealed and proved. • A two-stage dynamic aggregation model consists of resources selection and coordination is established. • A dynamic aggregation algorithm is proposed to deal with different aggregation scenarios. • The approximate guarantees and polynomial computational complexity of algorithm are proved. [ABSTRACT FROM AUTHOR]