Variable fractional power‐least mean square based control algorithm with optimized PI gains for the operation of dynamic voltage restorer

Abstract The operation of Dynamic Voltage Restorer has been studied for the mitigation of supply voltage disturbances like sag, swell, distortions, and unbalances. A Dynamic Voltage Restorer with three single‐phase Voltage Source Converters has been implemented for this purpose. Dynamic Voltage Restorer's compensation capability has been evaluated while introducing the above‐said voltage related disturbances in the supply by different means. A control algorithm named Variable Fractional Power‐Least Mean Square has been proposed for generating the load reference voltage for Dynamic Voltage Restorer. Variable Fractional Power‐Least Mean Square extracts the fundamental active and reactive component out of non‐ideal supply voltage and is thus, used in generating reference load voltage. This algorithm is more robust with respect to disturbance due to variable step size and is computationally less expensive. In addition, an optimization‐based approach has been proposed to estimate the approximate values of PI control gains. For this reason, a population‐based optimization method known as Sine Cosine Optimization has been used. The added feature of the optimization method is the reduction of computational time as compared to conventional PI controller tuning. A model of Dynamic Voltage Restorer using Variable Fractional Power‐Least Mean Square control algorithm with Sine Cosine Optimization tuned PI gains has been built in MATLAB Simulink as well as a reduced scale experimental prototype and their results have been presented with discussion

Studies of Simultaneous Observation of Spread-F Occurrence on Oblique & Vertical Incidence Records

248-249Results of simultaneous observation of spread-F irregularities on vertical and oblique incidence are presented, The vertical incidence data relate to Kakinada while the oblique incidence data relate to CW transmissions recorded from All India Radio, Hyderabad, at 4.8 MHz during 1800-2230hrs 1ST.Comparison of these data revealed that in a majority of the cases, there is no time delay in the spread-F occurrences on vertical and oblique incidence data indicating that the agency causing spread-F irregularities has an extent greater than 200 km in the east-west plane

Co-ordinated observations of VHF scintillations in India during February-March 1993

22-29The VHF scintillation observations made at a chain of stations in India during February-March 1993 under AICPITS (third campaign), using the 244 MHz radio beacon from FLEETSAT, and analysed jointly by all participating investigators at a workshop held at Raj kot are described. The occurrence features of scintillations during the third campaign were similar to those observed during the first campaign of March-April 1991. The maximum occurrence was, however, reduced to some extent due to the lower solar activity. The latitudinal variations showed an increased occurrence in the region of about 17-18o latitude. The data during the night of 19-20 Feb. 1993 when an extensive ‘Ionisation Hole Campaign’ was undertaken showed scintillations marked by earlier onset and longer duration at stations Waltair and Nuzvid than at the stat ions close to the magnetic equator. However, based on the average variations during February-March 1993 the onset at Tiruchendur, Anantpur and Walt air was at nearly the same time. The vertical rise velocity of the plasma depletions, estimated from the time delays in the onset of scintillations at latitudes away from the dip equator, was found to range from 40 m/s to 420 m/s in the altitude region 300-1350 km