K. Chandra Sekhar

A novel five-level inverter topology for DTC induction motor drive

A novel multilevel control structure for induction motor based on the Direct Torque Control (DTC) strategy using a Five-level Multi Point Clamped (MPC) Voltage Source Inverter (VSI) is presented. It is shown that the multilevel topology presents enough degrees of freedom to control both electromagnetic torque and stator flux with very low ripple and high dynamics on other side. From the simulation results shows that feeding electrical drive with multi level inverter can greatly improves the drive performance. The performance of this control method has been demonstrated by simulations performed using a versatile simulation package, Matlab/Simulink.

Five-level SPWM Inverter for an Induction Motor with Open-end Windings

This paper presents a five-level inverter for an open-end winding induction motor. Five-level inversion is achieved by feeding an open-end winding induction motor with a 3-level inverter from one end and a 2-level inverter from the other end of the motor. The 3-level inverter used in the proposed drive, is realized by cascading two 2-level inverters. The combined inverter system with open-end winding induction motor produces voltage space phasor levels identical to a conventional 5-level inverter. In the multilevel carrier based sinusoidal pulse width modulation (spwm), used for the proposed drive, a progressive discrete DC bias depending upon the speed range is given to the reference wave so that the drive can operate in the k-level modes (k = 2, 3, ... 5) depending on the speed range. The inverter with the higher DC-link voltage is switching less frequently, compared to the inverter with the lower DC-link voltage.

Performance analysis of a hybrid power system with three phase interleaved bidirectional converter

A utility interface converter is one of the key components in the hybrid power systems. This Paper addresses a novel three phase interleaved bi directional power converter circuit for economical solar, wind & battery hybrid power system (HPS). HPS consists of both AC and DC networks connected together by three phase interleaved bi directional converter in combination with 3phase pulse width modulation controlled converter. Here PWM controlled converter switches are used for smooth power transfer between AC and DC links and to maintain stable operation with various renewable sources (Both AC and DC), different loads. The addressed hybrid architecture is very flexible to decrease the required power conversions stages and hence the system cost and efficiency. The HPS is simulated in MATLAB/Simulink Environment and the simulation results show that the system can maintain stable operation with three phase interleaved bi directional converter both in the grid tied, autonomous modes.

Variable Structure Controller for Generator Side Converter of Variable Speed PMSG Wind Energy Conversion System

paper presents a novel control strategy based on variable structure theory (VST) for the generator side converter to regulate the dc link voltage of a direct driven PMSG wind energy conversion system (WECS). The validity of the technique is theoretically analyzed, and the design procedure is presented. The primary merit of the proposed technique is that it does not require an anemometer or prior knowledge of a system, but has an accurate and fast dynamic response to wind speed fluctuations. Modeling of Wind turbine, PMSG, controlling of generator side switch mode converter and Simulation results are presented. Simulation is done in MATLAB/POWERSYSTEM environment. Index terms Variable-speed wind turbine, PMSG, VSCS, SMC and switch-mode rectifier (SMR).

A novel five-level SPWM Inverter system for dual-fed induction motor drive

In this paper, a new five-level inverter system for dual-fed induction motor drive is described. The dual-fed structure is realized by opening the neutral-point of the conventional squirrel cage induction motor. The five-level inversion is obtained by feeding the dual-fed induction motor with four-level inverter from one end and two-level inverter from the other end. The four-level inverter used in this proposed topology is obtained by connecting three 2-level inverters with equal DC link voltage in cascade. This inverter scheme does not experience neutral point fluctuations and uses a lesser number of DC sources compared to the series H-bridge topology. A multilevel carrier based Sinusoidal Pulse Width Modulation is implemented for the proposed drive where a progressive discrete DC bias depending upon the speed range is given to the reference wave to reduce the inverter switchings.

Design and Implementation of Hybrid Active Power Filter

This paper deals with a hybrid active power filter with injection circuit (IHAPF). This paper concluded that the stability of the IHAPF based on detection supply current is superior to that of others. To minimize the capacity of IHAPF, an adaptive fuzzy dividing frequency-control method,.The generalized integrator is used for dividing frequency integral control, while fuzzy arithmetic is used for adjusting proportional-integral coefficients timely. The simulation results shows that the new control method is not only easy to be calculated and implemented, but also very effective in reducing harmonics.

A simplified model for load frequency control in deregulated power systems

This paper presents a simplified model for load frequency control (LFC) in deregulated power systems. LFC in deregulated power system is modeled by modifying conventional model with inclusion of bilateral contracts. Bilateral contracts will allow DISCOs in one area to get power from another area. This inclusion complicates the design of the controller by adding the contracted power also along with the disturbance power. New LFC model facilitates us to design the controller without considering bilateral contracts which works for power system with bilateral contracts also. And concentrates only the load disturbances not on the contracted loads. The proposed new AGC model is simulated in MATLAB environment and results were presented.

Effective Mitigation of Voltage Flicker in Power System using 12-Pulse Converter based Statcom

A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure of end user equipments. Voltage flicker is considered as one of the most severe power quality problems caused by large time-varying loads like arc furnaces. To reduce this kind of disturbances, Static Var Compensators (SVC) has been used so far which have a limited flicker mitigation capability. In the paper, 12-pulse converter based STATCOM has been proposed for effective mitigation of Voltage flicker and reduction of total harmonic distortion in the system. All the simulations have been performed using MATLAB Software. The obtained results show that 12-pulse converter based STATCOM is very efficient and effective for the mitigation of voltage flickering and THD reduction.

Optimal Re-Scheduled Generation using Participation Factors

The objective of power systems operation and planning in the interconnected power system is to maximize the social welfare through minimizing total generation costs. This paper presents a novel approach for optimal generation considering stability limits. The paper examines two approaches for optimal generation. The first approach is based on analyzing their shares in increased load on system. The second approach is based on voltage stability consideration. An IEEE-6 bus test system is used to demonstrate the results. One of the modern power system analyzer MiPower software is used to model and solve the optimization problems involved and the MATLAB software is used to perform graphical representations through an interface between both programs.

Multi-level inverter for Induction Motor Drive

In this paper space vector modulation and multi level carrier based PWM for the 4-level inverter fed induction motor drive are presented. Four-level inversion can be achieved by connecting three two-level inverters in cascade. Three isolated power supplies with DC link voltages are required for the proposed circuit topology. The voltages constitute one third of that of a conventional 2-level inverter topology. This scheme is capable of producing 512 voltage space phasor combinations distributed over 37 space phasor locations. The proposed four-level inverter configuration requires lesser number of switching devices as compared to the conventional four-level inverter scheme. Similarly, lesser-isolated power supplies are required when compared to the cascaded H-bridge configuration. This inverter scheme does not experience neutral-point fluctuations.