Comparison of resonant current regulators for DFIG during grid voltage distortion

We investigate two different kinds of resonant current regulators for a doubly fed induction generator(DFIG) under distorted grid voltage conditions: proportional integral resonant(PIR) regulator with traditional resonant part and vector proportional integral(VPI) regulator with VPI resonant part. Based on the mathematical model of DFIG under distorted grid voltage, the transfer function and frequency response characteristics of the two current regulators are analyzed and compared. The superiority of the VPI current regulator over the PIR regulator is pointed out, and the influence of discretization methods on the performance of the resonant current regulator is studied. All the results are validated by MATLAB simulation and experiments.

Design,Implementation and Performance of Synchronous Current Regulators for AC Drives

Accurate,high bandwidth current control is a requirement for high performance vector controlled AC drives.Synchronous PI current regulators are the preferred solution for this purpose.Design and operation principles of synchronous PI current regulators are well established.However,there are a number of issues that must be considered,especially when the drive must operate at high synchronous frequencies,including regulator design,effects due to discretization and the associated delays,voltage constraints and current sampling issues among other.Inadmissible degradation of the current regulator performance and consequently of the drive can occur otherwise.

Endogenous bioelectric fields: a putative regulator of wound repair and regeneration in the central nervous system

Studies on a variety of highly regenerative tissues, including the central nervous system（CNS） in non-mammalian vertebrates, have consistently demonstrated that tissue damage induces the formation of an ionic current at the site of injury. These injury currents generate electric fields（EF） that are 100-fold increased in intensity over that measured for uninjured tissue. In vitro and in vivo experiments have convincingly demonstrated that these electric fields（by their orientation, intensity and duration） can drive the migration, proliferation and differentiation of a host of cell types. These cellular behaviors are all necessary to facilitate regeneration as blocking these EFs at the site of injury inhibits tissue repair while enhancing their intensity promotes repair. Consequently, injury-induced currents, and the EFs they produce, represent a potent and crucial signal to drive tissue regeneration and repair. In this review, we will discuss how injury currents are generated, how cells detect these currents and what cellular responses they can induce. Additionally, we will describe the growing evidence suggesting that EFs play a key role in regulating the cellular response to injury and may be a therapeutic target for inducing regeneration in the mammalian CNS.

Influence of the Electrical Vehicle Charging on the Grid Harmonic

This paper described the impact of the electrical vehicle（EV） charging on the grid harmonic. In view of the randomness of the EV charging process, the harmonic admittance matrix method and superposition method were used to build the single and multiple EVs charging simulation model. By using Matlab as a simulation tool, we analyzed harmonic currents of single and multiple EVs chargers. The results show that the harmonic ratio is beyond the scope of the national harmonic standard. Finally a parallel hybrid active filter（PHAPF） was introduced for governance of harmonic.The experimental results show that net side harmonic currents are significantly reduced by using the PHAPF and meet the national standard GB/Z17625.6-2003 regulations limit.

mproved Zone 1 Top-line Tilting Scheme for Polygonal Distance Protection in the Outgoing Line of Type-4 Wind Parks

The impedance element in distance protection equipment in the outgoing line of a wind park(WP)may be heavily affected by the fault response of the WP.During resistive grid faults,relay over-reach(or under-reach)may manifest,depending on the fault current regulating requirements in the specific grid code deployed in WP and the fault conditions.Aiming at potential solution,i.e.the existing zone 1(fast tripping zone,non-delayed)top-line tilting(Z-1-TLT)function in modern numerical relays,this paper first assesses its adaptability under the WP integrated background.Combining the principle of Z-1-TLT itself and fault modeling to the WP,an improved Z-1-TLT scheme is developed,which can actively compensate for the possible relay overreach or under-reach during resistive faults,utilizing relay side fault quantities only.Aiming at the needless action of the new Z-1-TLT scheme against certain faults,malfunction risk area detection and dead zone detection are introduced as auxiliary criteria to optimize protective efficiency.Simulation results prove the improved Z-1-TLT scheme can effectively improve reliability of distance protection deployed in the WP outgoing line.

Homogenous lithium plating/stripping regulation by a mass-producible Zn particles modified Li-metal composite anode

A stable lithium-metal anode is critical for high performance lithium-metal batteries. However, heterogeneous Li plating/stripping may induce lithium dendrites formation on bare lithium-metal anode, which lowers the cell Coulombic efficiency and weakens battery safety. We found that bare Li metal surface becomes bumpy and cratered with numerous pits formation during Li stripping. These pits enhance electric field distortion and heterogeneous ion distribution during plating. Li plating preferentially happens on the edge of the pits, intensifying the voltage variation and Li dendrites growth, which leads to the cell rapid death or separator piercing. Herein, we propose a facile and mass-producible method to homogenize Li plating/stripping via adding lithiophilic particles into Li metal. Zinc particles were uniformly pressed in Li metal by a facile and scalable physical strategy of “rolling”, and transformed into LiZn alloy in situ through Li-Zn alloying at room temperature in a few minutes. The critical role of modified LiZn/Li composite anode in stabilizing electrode surface was revealed by both electrochemical test and simulation. Compared with bare Li anode, the evenly dispersed LiZn alloy particles in Li metal can effectively regulate the Li plating/stripping on electrode surface, reducing deepness of pits during stripping and directionally inducing Li plating to maintain electrode surface stability. On this basis, the pits depth of LiZn/Li composite during Li stripping is reduced to ∼ 15 μm, which is much shallower than that of bare Li metal of ∼ 40 μm. The LiZn/Li composite electrode can stably cycle for 600 h under Li plating/stripping capacity of 1 mAh·cm−2 and current density of 1 mA·cm−2 without any short circuit. Furthermore, assembled LiZn/Li||LiFePO4 full cell presents better cycling stability and rate performances than that of based on bare Li anode.