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Commutation failure (CF) threatens system safety with traditional HVDCs. To improve the recovery performance from CF, a novel recovery strategy is proposed, where a dynamic current ramp limiter is introduced to reduce the probability of current overshot during the recovery. The dynamic ramp limiter is designed based on the idea of judging the system recovery state by the dc current level, where a high level corresponds to a high risk of CF. The ramp limit is calculated by the frequency constraint of ac systems. Case studies based on a real-world system are used to verify the effectiveness of the proposed method, and the results show that the proposed method can improve the recovery performance and avoid the continuous CFs.

The large-scale new energy station transmission system is relatively weak, and long-distance transmission is prone to transient overvoltage. The hysteresis of the control loop of the Static Var Generator (SVG) can also contribute to the increase of transient overvoltage. Therefore, this article first establishes a photovoltaic power generation model, SVG model, and photovoltaic grid-connected system. Secondly, the transient overvoltage coupling mechanism of photovoltaic grid-connected systems under various faults such as commutation failure, DC blocking, and DC restart was analyzed through PSCAD simulation. At the same time, the changes in transient overvoltage before and after the installation of SVG were compared, and SVG’s reactive power dynamic behavior was analyzed. Finally, the mechanism of SVG assisting in increasing transient overvoltage was summarized.

Recent progress in quantum simulation and algorithms has demonstrated a rapid expansion in capabilities. The search continues for new techniques and applications to exploit quantum advantage. Here we propose an innovative method to investigate directly the properties of a time-dependent density operator ρ ˆ ( t ) . Using quantum commutation simulators, we can directly compute the expectation value of the commutation relation and thus of the rate of change of ρ ˆ ( t ) . The approach can be utilized as a quantum eigen-vector solver for the von Neumann equation and a decoherence investigator for the Lindblad equation, by using just the statistics of single-qubit measurements. A simple but important example is demonstrated in the single-qubit case and we discuss extension of the method for practical quantum simulation with many qubits, towards investigation of more realistic quantum systems.

Cet article présente la mise en oeuvre d’une nouvelle formation pratique pour la réalisation et la caractérisation électrique de cellules mémoires basées sur la commutation réversible entre deux états de résistance distincts dans le matériau diélectrique d’une structure MIM. L’enchaînement des étapes technologiques s’appuie sur les techniques élémentaires traditionnelles en microélectronique, et permet de donner une vue globale des problématiques actuelles dans le domaine de la fabrication des composants.

For the distance cost \\(c(x,y)=|x-y|\\), the set \\(O( )\\) of \\(W_1\\)-optimal plans is generally not a singleton. Under the classical absolute-continuity hypotheses in the Euclidean case, secondary variational selection by the quadratic energy \\(C_2\\) yields the ray-monotone \\(W_1\\)-optimal plan. We provide a counterexample to an open problem posed by Santambrogio that concerns the stability of this selector under weak convergence of the marginals. More precisely, we construct a fixed absolutely continuous source \\(\\) and absolutely continuous targets \\(_n\\) such that \\(^sel( _n)^hom\\), where \\(^homın O( )\\) but \\(^hom^sel( )\\). We also identify the narrow Kuratowski limit of the optimal-plan sets \\(O( _n)\\), derive the constrained \\(\\)-limit for secondary energies of the form \\(ınt (|x-y|)\\,d\\) with \\(ın C([0,2])\\), and deduce a non-commutation result for the additive perturbation \\(c_(x,y)=|x-y|+|x-y|^2\\).

An RGD system \\(\\mathcal{D}\\) is called \\emph{linear w.r.t. a root basis \\(\\mathcal{B}\\)} if the commutation relations between the root groups of \\(\\mathcal{D}\\) are `linear' in a certain sense. Moreover, \\(\\mathcal{D}\\) is called \\emph{linearizable}, if there exists a root basis \\(\\mathcal{B}\\) such that \\(\\mathcal{D}\\) is linear w.r.t. \\(\\mathcal{B}\\). For many examples of RGD systems it is easy to see that they are linear w.r.t. a concrete root basis. To the best of our knowledge, it was unclear whether RGD systems exist which are not linearizable. In this article we show that there exist uncountably many RGD systems which are not linearizable. In particular, we provide the first explicit example of such an RGD system. This expands the quote from R\\'{e}my that axiom (RGD\\(1\\))\\(_{\\mathrm{lin}}\\) is not only a strengthening of axiom (RGD\\(1\\)), but is in fact stronger than it. We show that non-linearizability appears in examples of universal type, and also in examples of \\(2\\)-spherical type. For the examples of universal type we construct an uncountable family of non-linearizable RGD systems, and for the examples of \\(2\\)-spherical type we show that the RGD systems of type \\((4, 4, 4)\\) recently constructed by the author provide uncountably many non-linearizable RGD systems.

In this paper, we introduce quantum root vectors for the quantum queer superalgebra \\( U_\\!v( q_n)\\) via a braid-group action, compute their complete commutation relations, and construct a PBW-type basis for the Lusztig integral form \\( U_v, Z\\). This yields an explicit presentation of \\( U_v, Z\\) and provides a way to understand the structure of the quantum queer superalgebra at roots of unity.

Due to the coupling effect between the DC/AC system as well as between different LCC-HVDC, the first commutation failure can cause a series of chain reactions, including successive commutation failure, overvoltage of the rectifier station, and subsequent commutation failure. The existing control methods for suppressing overvoltage or commutation failure cannot simultaneously meet the needs of the sending and receiving end grid of MIDC. It may expand the impact and scope of a single fault. Therefore, a commutation failure chain reaction suppression method is proposed based on the characterization of chain reaction boundary conditions. The effectiveness is verified by using the CIGRE standard test model.

To improve the ability of line-commutated converters (LCCs) to resist commutation failure (CF) when a fault occurs on the AC side, a novel sub-module-based LCC topology actively resistant to CF is proposed in this paper. The control strategy and the parameters of the proposed sub-module are elaborately designed. The proposed LCC topology can actively resist CF by providing an auxiliary commutation voltage to the AC side, and the sub-module is conducive to the rapid recovery of the thyristor’s forward blocking ability. Additionally, the initial capacitor voltage of the sub-module is designed optimally based on the commutation mechanism. The proposed LCC system can effectively improve the ability to resist CF by increasing the commutation margin of the LCC system. Furthermore, the capacitors are charged and discharged during fault time, so the capacitor voltages do not drop too low and, thus, are better at resisting CF. Matlab/Simulink simulation results verify that the proposed LCC quickens the commutation process, promotes commutation performance, and enhances the immunity of LCCs to CF.

Schemes of gravitationally induced decoherence are being actively investigated as possible mechanisms for the quantum-to-classical transition. Here, we introduce a decoherence process due to quantum gravity effects. We assume a foamy quantum spacetime with a fluctuating minimal length coinciding on average with the Planck scale. Considering deformed canonical commutation relations with a fluctuating deformation parameter, we derive a Lindblad master equation that yields localization in energy space and decoherence times consistent with the currently available observational evidence. Compared to other schemes of gravitational decoherence, we find that the decoherence rate predicted by our model is extremal, being minimal in the deep quantum regime below the Planck scale and maximal in the mesoscopic regime beyond it. We discuss possible experimental tests of our model based on cavity optomechanics setups with ultracold massive molecular oscillators and we provide preliminary estimates on the values of the physical parameters needed for actual laboratory implementations. Current hypotheses towards quantisation of gravity imply the presence of a minimal length scale, which may have a role in explaining quantum-to-classical transition. Here, the authors show how assuming the minimal length scale to be a fluctuating quantity leads to a possible universal decoherence mechanism.