Control-Loop-Based Impedance Enhancement of Grid-Tied Inverters for Harmonic Suppression: Principle and Implementation

Abstract

To understand different control loops that have been proposed to improve the quality of current into grid from the perspective of output impedance, control-loop-based output impedance enhancement of grid-tied inverters for harmonic suppression is proposed in this paper. The principle and generalized control loop deduction are presented for reshaping the output impedance. Taking a traditional LCL (Inductor-Capacitor-Inductor)-type inverter with dual-loop control as an example, different kinds of control loop topologies are derived step by step and further optimized for the implementation of the proposed principle. Consequently, the improved control consists of a filtering-capacitor voltage loop, and a grid current loop is found which can remove the existing inner capacitor current loop and therefore simplify the control. Finally, the effectiveness of the proposed control method is compared with the existing method and both are verified by simulations and experiments.

Ultrahigh Resolution Pixelated Top‐Emitting Quantum‐Dot Light‐Emitting Diodes Enabled by Color‐Converting Cavities

“…By simply photopatterning the IZO phase tuning layers, our cavity can selectively convert the unpatterned QD white emission as color‐saturated and color‐stable red, green, and blue emission with a brightness of 22 170, 51 930, and 3064 cd m −2 at 5.5 V, respectively. Compared with previously demonstrated techniques including ink‐jet printing, [ 11–16 ] transfer printing, [ 17–22 ] and QD photopatterning, [ 23–27 ] our method avoids the patterning of QDs, offers ultrahigh resolution of ≈1700 ppi (that can be improved to over 8000 ppi) and is compatible with large area manufacturing. Compared with “white + CF” techniques, [ 28 ] our scheme cancels the expensive CF arrays and eliminates the energy losses caused by the CFs.…”

“…Recently, by manipulating the ligands, the QDs can be cross‐linked when exposed under ultra‐violet illumination, thereby suggesting a promising way to pattern the QDs using mature photolithography technique. [ 23–27 ] Although the resolution of the QD arrays can be higher than 1400 ppi, [ 26 ] the performance of the resultant QLEDs could be degraded due to the introduction of the photochemical additives and the damage of the QDs when patterned several times. Instead of patterning the QDs directly, the red, green, and blue emission can also be obtained by filtering the white emission with a pixelated color filter (CF) array; [ 28 ] although this method has been adopted to manufacture large area OLED televisions and high resolution OLED microdisplays, the introduction of CF not only reduces over 70% of the brightness, but also increases the material cost of the displays, thus rendering this method not ideal for energy efficient and low‐cost displays.…”

A Bioinspired Stretchable Sensory‐Neuromorphic System

“…Green‐emitting CdSe/CdZnS QDs were prepared via the reported procedure with minor modification the method used by Yang et al. [ 57 ] As a typical synthesis, 16 mmol of Zn(OA) 2 solution and 1.6 mmol of Cd(OA) 2 , and 4 mL of ODE were loaded into a flask followed by degassing at 110 °C. The flask was backfilled with nitrogen, and the reaction temperature was heated up to 300 °C.…”

High Performance Inkjet‐Printed Quantum‐Dot Light‐Emitting Diodes with High Operational Stability

“…The lifetime under different brightness was estimated by the function of , where C is a constant, and n is the acceleration factor. According to the previous report, [ 8,14,36 ] n = 1.80 was widely adopted. Accordingly, the T 50 of Device A is 1 588 649 h @ 100 cd m −2 , and 25 178 h @1000 cd m −2 , which is about five orders longer compared to Device C based on the control ink, whose lifetime is 33 h @1000 cd m −2 .…”