G. Tulasi Ram Das

Comparison of PI and ANN control strategies of unified shunt series compensator

This paper presents the compensation principle using PI and ANN control strategies of the USSC in detail. The USSC is an active filter (AF) and it compensates the reactive power, harmonics in both the voltage and current caused by loads. The USSC makes use of two back to back connected IGBT based voltage source inverters (VSIs) with a common DC bus. One inverter is connected in series and the other one is placed in shunt with the load. The shunt inverter works as a current source and it compensates the current harmonics. The series inverter works as a voltage source and it helps in compensating the voltage harmonics. Previous works presented a control strategy for shunt active filter with PI control. Then, this control strategy was extended to develop the two controllers for shunt and series active filters. The simulation results of these control strategies are listed for comparison and verification of results

A structural & operational comparative study of converter topologies & analysis of MMC for high voltage applications

This paper presents the structural and operational comparison of line commutated converter (LCC), voltage source converter (VSC) and Modular Multi level converter(MMC) for High voltage applications and also presents the simulation model of modular multilevel converter (MMC) which is one of the most promising converter topologies for high voltage applications, especially for high-voltage direct-current (HVDC) transmission systems. The converter is characterized by a modular arm structure, formed by a cascaded connection of a large number of simple chopper cells with floating DC capacitors. These cells are called Sub-Modules (SM) and can be easily assembled into a converter for high-voltage or medium-voltage power conversion systems. A control scheme also presented for voltage balancing control and a leg total voltage control in order to achieve a stable behavior in all operating conditions. The validity and the effectiveness of the voltage control strategy are confirmed by numerical simulations. Simulations are done by using MATLAB/Simulink software.

Design of robust intelligent coordinated controller for power systems problems

This paper describes the design of an observer-based intelligent coordinated controller using fuzzy logic system and sliding mode observer. This concept prevents an electric power system losing synchronism after a large sudden fault and their by achieves good post-fault voltage level. The developed controller has a fuzzy logic unit, which accepts change in terminal voltage and speed deviation from an observer as its inputs which generates the required weightage for the transient controller and voltage controller. An observer is designed through sliding mode, to estimate the states of the system. The performance of the proposed controller is compared with the existing global control scheme. The simulation study is carried out for the configuration of a single machine infinite bus power system.

Comparison of Conventional, Fuzzy Logic and Neural Based HBPWM Current Controllers

This paper presents intelligent approach and model based approach for implementation of hysteresis band PWM current controller, a voltage source inverter. Current controlled voltage source inverters offer substantial advantages in improving motor system dynamics for high performance ac drive systems. This paper compares the performance of conventional, fuzzy and neural networks methods by simulating an indirect vector control of induction motor.

Analysis of Medium Voltage BTB System by Using Half Bridge Modular Multilevel Converter Topology

The modular multilevel converter topology (MMC) became potential converter topology for various high power applications. These are high voltage DC power transmission and other intertie connections of renewable energy sources to grid. The other application of MMC topology is variable speed drives, for controlling these variable speed drives a sine wave technique and square wave technique will be used. Particularly for high voltage direct current (HVDC) transmission applications, modular topology of voltage source converter gained attention because of its modularity, uniform modules connected in series or parallel. The other considerable advantage of MMC is their high efficiency because of low losses and the filtering requirements for harmonics are very less compared to other topologies. MMC gives increasing converter reliability and reduction of maintenance cost. This paper gives the simulation study of design of 50 Hz BTB system with 200 V and 10 kW. Two MMC-based converters connected back to back and control signals generated by using phase-shifted modulation. The main advantage of this DSC–MMC-based BTB intertie is the DC link capacitor and sensor for voltage is eliminated. The simulation study carried out for the DSC-based MMC for a 200 V, 10 kW, 50 Hz model with phase-shifted PWM. Simulation results of DSC–MMC-based BTB study and transient states are presented in this paper. Simulation carried by using MATLAB/Simulink software.

Comparative Study of Controllers for an Isolated Full Bridge Boost Converter Topology in Fuel Cell Applications

Received May 21, 2018 Revised Aug 30, 2018 Accepted Sep 13, 2018 This paper presents a novel Stator Current based Model Reference Adaptive System (SC_MRAS) speed observer for high-performance Six Phases Induction Motor (SPIM) drives using linear neural network. The article aim is intended to improve performance of an SC_MRAS observer, which were presented in the literature. In this proposed scheme, the measured stator current components are used as the reference model of the MRAS observer to avoid the use of a pure integrator and reduce the influence of motor parameter variation. The adaptive model uses a two-layer Neural Network (NN) to estimate the stator current, which has been trained online by means of a Least Squares (LS) algorithm instead of uses a nonlinear Back Propagation Network (BPN) algorithm to reduce the complexity and computational burden, it also help to improve some disadvantages cause by the inherent nonlinearity of the BPN algorithm as local minima, two heuristically chosen parameters, initialization, and convergence problems, paralysis of the neural network. The adaptive model of the proposed scheme is employed in prediction mode, not in simulation mode as is usually the case in the literature, this made the proposed observer operate better accuracy and stability. In the proposed observer, stator and rotor resistance values are estimated online, these values thereafter were updated for the current observer and rotor flux identifier to enhance the accuracy, robustness and insensitivity to parameters variation for the proposed observer. The proposed LS SC_MRAS observer has been verified thought the simulation and compared with the BPN MRAS observer. The simulation results have proven that the speed is estimated a consequent quicker convergence, do not need the estimated speed filter, lower estimation errors both in transient and steady state operation, better behavior in low and zero speed operation. Keyword:Received Jun 7, 2018 Revised Jul 8, 2018 Accepted Sep 13, 2018 Experiments confirmed that Transformerless Inverters (TIs) deliver more reliability and higher energy efficiency. Nonetheless, one of the shortcomings of TIs is the leakage current that occurs between the photovoltaic (PV) string terminals and the ground. Such a drawback is justified by the non-galvanic isolation caused by the transformer being omitted. As such, this study is intended to develop a novel TI inverter topology for solar PV systems. The latter is meant to remove the leakage current and enhance the operating system of the entire PV conversion as well. Added to its null zero-crossing distortion and capability regarding energy efficiency, the developed TI, being validated by simulation and experiment, eradicated the leakage current. Keyword:Now a day’s renewable energy sources became an interesting area of research of which fuel cells are emerged as an alternative source for producing electricity to meet the energy crisis. This led to a research on power conditioning systems through which fuel cell is interfaced to the utility. Of the different converter topologies Isolated full bridge boost converter (IFBC) topology is most suitable for fuel cell applications. In this paper a Predictive Switching Modulator (PSM) Control is proposed for the converter topology and its performance is compared with Linear Peak Current Mode control (LPCM), Non-Linear Carrier Control (NLC).Received May 2, 2018 Revised Aug 23, 2018 Accepted Sep 14, 2018 Recently of the main topic of research is the sensorless vector control of induction motor drive, In this paper presents the predictive model reference adaptive system (PMRAS) rotor speed observer, This observer developed from the classical MRAS rotor flux scheme associated with predictive adaptation mechanism designed from the Finite Control Set Model Predictive Control (FCS–MPC) by using a search optimization algorithm for calculate the rotor position which guarantee a minimum speed tuning error signal at each sampling period. The effectiveness of the proposed observer proved with the simulation results, show high dynamic performance speed and position observed in sensorless vector control process at low and zero speed as well robustness against motor parameter variation with different loading conditions. Keyword:

Torque and flux ripple minimisation in direct torque control of induction motor using space vector modulation

This paper explains the application of Space Vector Modulation (SVM) technique to reduce torque and flux ripple in an induction motor employing Direct Torque Control (DTC). The effective time is determined using imaginary time vector, thereby the lengthy procedure of using reference voltage vector is eliminated, and also the sector identification and angle determination are not used. Simulation studies are carried out for the proposed method and results are compared with the classical DTC. The results show that the torque, current and flux ripple are less to that of classical DTC. The proposed algorithm is implemented using Spartan 3A DSP Field Programmable Gate Array (FPGA) to validate the simulation results.