To reduce the frequency deviation and the rate of change of frequency (RoCoF) in a low inertia power system, some converters are required to provide the frequency response (FR) power normally associated with the frequency deviation and/or the RoCoF, by droop/inertia/PD control. In this article, a rapid power compensation (RPC) based FR strategy is developed to optimize the ability to compensate grid imbalance power, by fully exploiting the converter idle capacity. To this end, first, mathematical proof demonstrated the improved performance of the RPC strategy in terms of frequency deviation suppression versus droop control, and in terms of RoCoF suppression versus inertia control, with identical converter capacity limit. Moreover, it is proved that the RPC strategy can achieve consistent FR performance with respect to the optimal PD control, i.e. it can maximize the suppression of frequency deviation and RoCoF simultaneously, yet avoiding the limitations due to unknown grid parameters. Finally, by analyzing the operation modes and identifying the pertinent switching logic, the detailed implementation of the proposed RPC strategy is developed. Its superb FR performance is verified by the experiment results in a twoconverter low-inertia system, and simulation results in an IEEE four-machine two-area system.Index Terms-Frequency deviation, frequency response (FR), grid-tied converter, low inertia power system, rate of change of frequency (RoCoF), rapid power compensation (RPC). Parameter Value Parameter Value Rated line-to-line voltage E0 380 Vrms Zg 0.12 Ω / 0.2 mH Rated grid frequency 50 Hz Passive filter 0.01 Ω / 0.1 mH Rated grid active power Pref 20 kW DC voltage UDC 800 V Rated grid reactive power Qref 0 kVar Current loop: Kp 0.24 Load power 36 kW Current loop: Ki 2.5 Active power loop: KP 7.6E-5 Voltage loop: Kp 0.2 Reactive power loop: KQ 3.1E-3 Voltage loop: Ki 280
Amplitude-phase information of the voltage/current phasor, which is the prerequisite for grid-tied converter control and protection, can change almost instantaneously in lowvoltage distribution systems with small X/R ratios. However, the equivalent impedances of high-voltage power systems are usually inductive (with large X/R ratios), and the power flow of pertinent grids generates decaying DC (DDC) components with large amplitude and long duration during large disturbances. Therefore, the X/R ratios and DDC components must be fully considered in amplitude-phase detection to achieve effective converter control and protection. To this end, the main components present in the transient voltage/current of a high-voltage power system after unbalanced disturbance are first analyzed, and the general transient model is obtained by synthesizing multi-mode DDC components. Then, by resorting to waveform characteristics of different components, an amplitude-phase detection algorithm is proposed based on the multi-component parallel-detection structure. Compared to existing techniques, the detection time is reduced to half grid cycle. Finally, an iterative variable-interval integral algorithm is developed, improving the anti-noise ability of detection algorithm, and overcoming the computational burden issue. This enables the direct integration of algorithm into the converter's embedded processor. Experiment results verified the effectiveness and superiority of the proposed technique.
We utilize the supramolecular self-assembling peptide of Nap-GFFYK to construct chemically programmed, self-assembling and self-adjuvant MUC1-based antitumor vaccines. The vaccines, with antigen and adjuvant conjugation through covalent bonds, elicited both humoral and cellular immune responses.
Background: Therapeutic tumor vaccines are one of the most promising strategies and have attracted great attention in cancer treatment. However, most of them have shown unsatisfactory immunogenicity, there are still few available vaccines for clinical use. Therefore, there is an urgent demand to develop novel strategies to improve the immune efficacy of antitumor vaccines. Purpose: This study aimed to develop novel adjuvants and carriers to enhance the immune effect of MUC1 glycopeptide antigen-based antitumor vaccines. Methods: An antitumor vaccine was developed, in which MUC1 glycopeptide was used as tumor-associated antigen, α-GalCer served as an immune adjuvant and AuNPs was a multivalent carrier. Results: Immunological evaluation results indicated that the constructed vaccines enabled a significant antibody response. FACS analysis and immunofluorescence assay showed that the induced antisera exhibited a specific binding with MUC1 positive MCF-7 cells. Moreover, the induced antibody can mediate CDC to kill MCF-7 cells. Besides stimulating B cells to produce MUC1-specific antibodies, the prepared vaccines also induced MUC1-specific CTLs in vitro. Furthermore, the vaccines significantly delayed tumor development in tumor-bearing mice model. Conclusion: These results showed that the construction of vaccines by presenting α-GalCer adjuvant and an antigen on gold nanoparticles offers a potential strategy to improve the antitumor response in cancer immunotherapy.
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