Modelling and control of single VSI leading experimental hybrid power system integrating a wind turbine simulator
This paper discusses a hybrid wind diesel system aims to validate wind powered section of the experimental system. The experimental system proposed consists of a wind turbine simulator, a permanent magnets generator, a diode bridge rectifier, a step down converter, a bank of battery, a load and a control unit. An other operation of three-phase, four-wire voltage source inverter (VSI) under unbalanced voltage conditions is also investigated.
Research on control strategies for distributed inverters in low voltage micro-grids
Taking into account the configuration of low voltage distributed grids. The micro-grid that is consisted of three-phase four-leg inverters is proposed in this paper. Then, a decomposing sequence control strategy and a droop control method are explored. Positive, negative and zero sequence components can be controlled by the decomposing sequence control method independently. The decomposing sequence control algorithm is implemented in dq0 reference frame, which can achieves voltage regulation with low THD and fast transient response, and inverters can output a set of symmetric ac voltages under various loads. Meanwhile, inverter' output impedance is fixed through a virtual impedance scheme. The droop-control method is applied to regulate the frequency and amplitude of inverters output voltages, which only use local measurements of the inverter. These control strategies can improve the modularity, reliability and flexibility of the distributed power supplies. The total loads are shared among inverters by the propose control strategies. Simulation results are provided from two 6KVA parallel-connected inverters in an island micro-grid, which verifies the validity of method proposed.
Comparison of a Radiometric Procedure with Conventional Methods for Identification of Neisseria
A radiometric procedure was compared with the conventional cystine tryptic agar (CTA) sugar fermentation method for identification of Neisseria species. Four different ATCC cultures of Neisseria were identified by both procedures with identical results. The only difference noted was that the radiometric procedure required 3 h for completion, whereas the conventional CTA sugar method required overnight incubation. The radiometric procedure was also compared with the fluorescent antibody (FA) and CTA methods for identification of Neisseria gonorrhoeae. The organisms examined were gram-negative, oxidase-positive diplococci isolated from 49 clinical specimens sent to the laboratory for bacteriological analysis. Results obtained by both CTA and FA procedures were comparable. However, the radioisotope method appeared to be superior to the other two methods in that only one isolate identified as positive by both the CTA and FA methods was not identified radiometrically, whereas four isolates positive by the radiometric method were not identified by the other two procedures. Thus, a total of seven more positive identifications were made radiometrically than by either of the two other methods. All positive identifications were confirmed by a reference laboratory. These results indicate that the radiometric procedure is more rapid and reliable as compared with both the CTA and direct FA methods and, thus, may serve as a valuable addition to the methodology available for diagnostic microbiology.