Golam Sarowar

An optimization methodology of susceptance variation using lead-lag controller for grid connected FSIG based wind generator system

Abstract In wind power system, low frequency oscillations are observed due to imbalance between mechanical input and electrical output. Hence, variable susceptance controllers are being adopted to mitigate these oscillations. However, improper modulation of control parameters also leads to system instability. Therefore, we propose an optimization methodology for mitigating low frequency oscillations in wind power generation system. To visualize our methodology, we use a lead-lag type variable susceptance controller for fixed speed induction generator (FSIG) based wind generation system. Then, we optimize gain and time constants of lead-lag controller using three optimization algorithms: particle swarm optimization (PSO), genetic algorithm (GA), and flower pollination algorithm (FPA). Later, we perform non-linear time domain simulation and quantitative analysis to find average fitness, standard deviation, run time, and iteration number for these optimization algorithms. Moreover, non-parametric statistical analysis, such as Kolmogorov–Smirnov and Wilcoxon signed-rank tests are employed for identifying statistically significant differences among these algorithms.

High Gain Non Isolated DC-DC Step-up Converters Integrated with Active and Passive Switched Inductor Networks

Efficiency, reliability, high power quality and continuous operation are important aspects in electric vehicle attraction system. Therefore, quick fault detection, isolation and enhanced fault-tolerant control for open-switches faults in inverter driving systems become more and more required in this filed. However, fault detection and localization algorithms have been known to have many performance limitations due to speed variations such as wrong decision making of fault occurrence. Those weaknesses are investigated and solved in this paper using currents magnitudes fault indices, current direct component fault indices and a decision system. A simulation model and experimental setup are utilized to validate the proposed concept. Many simulation and experimental results are carried out to show the effectiveness of the proposed fault detection approach.The inverter with critical loads should be able to provide critical loads with a stable and seamless voltage during control mode change as well as clearing time. The indirect current control has been proposed for providing stable voltage with critical load during clearing time and seamless control mode transfer of inverters. However, the islanding detection is difficult since with the indirect current control the magnitude and frequency of voltage do not change when the islanding occurs. The conventional anti-islanding method based on the magnitude and frequency of voltage variation cannot apply to the indirect current control. This paper proposes an islanding detection method for the indirect current control. The proposed islanding detection method can detect the islanding using reactive power perturbation and observation when the frequency and magnitude of voltage don’t vary during clearing time. In order to verify the proposed anti-islanding method, the experimental results of a 600W three-phase inverter are provided.

Non-isolated single stage PFC based LED driver with THD minimization using Cúk converter

This paper proposes a utility supply driven single stage PFC based LED driver using Cúk converter. For low DC voltage output requirement of LED driver, Cúk converter is a convenient choice due to its topological suitability for PFC application and stepping the voltage down at a desired level unlike the Boost Converter. A hysteresis current control scheme is adopted to operate the converter in Continuous Conduction Mode (CCM) and fast enough to follow the current reference causing power factor to approach near unity. Although the converter operates at variable switching frequency, the response is very fast and independent of the converter dynamics. At the same time the converter ensures a constant current drive at the output side to operate the LED. Theoretical analysis, design calculation and simulation results confirm that the proposed single stage control scheme operates with an improved THD and performs better compared to the commercially available controller because the same converter is used for both PFC and LED Driver. As it diminishes one stage of power conversion, the efficiency of the driver is increased whereas the complexity in controller design and implementation is decreased.