The Effect Of Switching Frequency On Switching

ABSTRACT- D.C. motors are seldom used in ordinary applications because all electric supply companies furnish alternating current. However, for special applications such as in steel mills, mines and electric trains, it is advantageous to convert low value of DC into high value of DC in order to use D.C. motors controlled by power electronic apparatus. Here the DC motor is controlled power electronic converters through RES system. Although the design of these converters has been presented at the operational level, some fundamental issues such as topologies, analyses, and control have not been thoroughly studied. In this paper, the basic HB TL topology is first presented. This is followed by the derivation of a systematic method of generating TL converter topologies, leading to the derivation of a family of TL converters with improvement and simplification for better functionality and practicality. This paper discusses wide range soft switching solutions to a pulse width

Fig. 11 shows a comparison of DPWM2O, DPWMLPF2 and GDPWMO at 0.4 modulation index. The inverter is operating with 160 Hz fundamental frequency and 7.68 kHz switching frequency. The output power factor angle is 45°. It can be seen that each strategy produces 32 pulses in one cycle. However, the clamping interval of the GDPWMO strategy is perfectly aligned with the line current peaks, whereas the DPWM2O and DPWMLPF2 strategies incurs switching instances around the current peaks.

Referring to Fig. 1(ii), consider in region II, the reference voltage vector is following the arc x1x2 at a particular modulation index m. The position of the reference voltage vector is shown in Table 1. It shows that, depending on modulation index value, the duration of stay within subsector 1 and subsector 2 changes. Similarly, consider in region III, the reference voltage vector is following the arc y1y2 at aparticular modulation index. The position of the reference voltage vector is shown in Table 1 and it shows that depending on the modulation index value, the duration of stay within subsector 2,3 and 4 changes.

This paper investigates adjustable speed induction motor drive using 2-level and 3-level PWM.The result obtained is verified using Matlab simulation.This result compares the hamonic contect in between 2-level and 3-level by FFT analysis tool.To analyse the resulta a carrier based pwm was taken using 2- level and 3- level topology and a threephase bridge convetor with internally generated capability SPWM/SVPWM was intrduced. Carrier freqency18*60Hz, modulation index 0.9, output voltage freqency 60 Hz and ouput voltage phase 0 degre Was fixed. So corresponing to above values,the motor speed was 1800 rpm. Or 188.5 radian/sec, hence torque is 11.87Nm. A two pole squirrel cage motor was taken subjected to 400V dc source with modulation index0.9 prduces 220v rms.when motor starts, at 0.5s it reaches its steady speed 181 radian/sec or 1728 rpm. Now by discretizing the FFT tool displays the frequency spectrum of voltage and current waveforms. These signals are stored in workspace in the ASM structure with time variable generated by the Scope block. As my model is discretized, the signal saved in this structure is sampled at a fixed step and consequently satisfies the FFT tool requirements.It was observed that value of total harmonic distortion(THD) was 65.77 percent in 2-level and 35.11 percent in 3- level for SPWM invertor and 56.77 percent for SVPWM invertor.

Abstract—Different converter topologies have been introduced for high power applications in recent years. This paper shows Permanent Magnet Synchronous Motor in Hybrid electrical vehicle is proposed by an interface of boost converter, interleaved converter and inverter as an integrated circuit. An inverter/converter circuit is designed in such a way so as to operate or control the HEV during different modes of operation. The integrated circuit in HEV will operate as a boost converter or interleaved converter depending on the load condition. The proposed integrated circuit will reduce the current ripple and voltage ripple hence it will leads to reduction in switching, conduction losses, and thermal stress on the motor. The effectiveness of proposed integrated circuit is simulated in MATLAB/ Simulink. The simulation shows that the integrated circuit have a high efficiency and can be used at high power application.

In this paper a zero voltage switched active network (Fig. 1) used in combination with three-phase ac to dc diode rectifiers is presented. It is shown that by using proposed switching network in three-phase ac to dc boost converter, zero switching losses are obtained while maintaining a unity input power factor. Active network capacitor, Cs, diodes D7, and D8, maintain a zero voltage during turn-off of Q1, and Q2, Capacitor, Cs, discharges through the boost inductors of the circuit thus limiting the rate of rise of current during turn-on. Moreover, the advantage of the proposed active network is that it can maintain a zero voltage switching over the entire range of the duty cycle of the operation. Consequently, boost stage can be used directly to control the dc bus voltage by varying the duty cycle at Constant switching frequency. The resulting advantages include higher switching frequencies, and better efficiency. Finally the operation of the active switching network is verified experimentally on a prototype three-phase ac to dc converter.

Abstract—for very high voltage gain of a Photo-Voltaic system, this paper proposed a buck-boost inverter of single stage. DCM (Discontinuous conduction mode) and MPPT (maximum power point tracking) is employed to get one power factor. Minimization of switching losses is employed with only two switches and operated at very high frequency. Easy control capability, optimum size, affordable cost with high voltage gain made the system employable. AC voltage conversion is achieved along with boosting of DC voltage of Photo-Voltaic system of inverter. Obstacle shadow variations also reduced by means of having the possibility of reduced series connected modules; this ability is due to the high voltage gain. Since the proposed design has the two buck boost converter each one operates for only one half cycle and the Discontinuous conduction mode operates at unit power factor. Simulation results assure the proposed idea of the single stage interleaved inverter for high voltage gain applications.

Solid-state choppers due to various advantages are widely used in trolley cars, battery-operated vehicles, traction-motor control, and control of a large number of d.c motors from a common d.c bus with a considerable improvement of power factor, The basic Chopper circuit is shown below.

ABSTRACT: -- In this a fuzzy logic control technique has been proposed for power quality improvement by using UPQC The UPQC is controlled to regulate the WF terminal voltage, and to mitigate voltage fluctuations at the point of common coupling (PCC), caused by system load changes and pulsating WF generated power, respectively. In order to reduce the voltage fluctuations that may cause “flicker”, and improve WF terminal voltage regulation, several solutions have been posed. The voltage regulation at WF terminal is conducted using the UPQC series converter, by voltage injection “in phase” with PCC voltage. On the other hand, the shunt converter is used to filter the WF generated power to prevent voltage fluctuations, requiring active and reactive power handling capability. The sharing of active power between converters is managed through the common DC link. A customized internal fuzzy logic control scheme of the UPQC device was developed to regulate the voltage in the WF terminals, and to mitigate voltage fluctuations at grid side. Simulation results show the effectiveness of the proposed compensation strategy for the enhancement of Power Quality.

Abstract—This paper proposes a method for optimization of the harmonic performance of CHB inverter under Selective Harmonic Elimination PWM modulation (SHEPWM) control. The proposed optimization techniques are used to solve the set of non-linear transcendental trigonometrical equations. SHE were implemented to reduce the THD value. The set of non-linear transcendental equation is minimized by proposed Big Bang-Big Crunch optimization technique. The proposed topology is suitable for any number of levels. In this paper third, fifth, seventh and ninth level harmonics have been eliminated. Simulation work is done in MATLAB software and experimental results have been presented to validate the theory.

and high-power applications. For closed loop speed control operation, in current control loop, three phase stator current information is required. The current sensors and the associated accessories increase the complexity of the system, cost and size of the motor drives and decrease the reliability of the system and also more number of power electronics switches means more switching losses and costly. Therefore to overcome this problem a new drive system is proposed which uses four switches and two current sensor, less switches and less current sensors means less switching losses and low cost. In this paper, the PWM technique is therefore proposed to minimize the torque ripple and designed to overcome the disadvantages from other torque ripple

Abstract—This paper proposes direct torque control of induction motor simulation using conventional method and space vector pulse width modulation technique for ripple reduction. Direct Torque Control (DTC) is a control technique used in AC drive systems to obtain high performance torque control and thereby controlling the speed of induction motor. The

Abstract—This paper proposes direct torque control of induction motor simulation using conventional method and space vector pulse width modulation technique for ripple reduction. Direct Torque Control is a control technique used in AC drive systems to obtain high performance torque control and thereby controlling the speed of induction motor. The principle is based on simultaneous decoupling of stator flux and electromagnetic torque of AC drive system. DTC drives use hysteresis comparators and they suffer from high torque ripple and variable switching frequency problem. The proposed SVM based DTC reduces torque ripples. The basis of the SVM-DTC methodology is the calculation of the required voltage space vector to compensate the flux and torque errors and its generation using the SVM at each sample period. The performance of this method is demonstrated by simulation using MATLAB/Simulink software. Simulation results presented in this paper show the torque, flux linkage and stator current ripple decreases with the proposed SVM-DTC algorithm.

Abstract— This paper presents unipolar pulse width modulation technique with sinusoidal sampling and Space vector pulse width modulation are analyzed for three-phase Diode clamped multi-level inverter from the point of view of the Phase voltages, currents, voltage across the split capacitors and Total harmonic distortion. The necessary calculations for generation of PWM for the two modulation strategies have presented in detail. It is observed that the unipolar modulation ensures excellent, close to optimized pulse distribution results but THD is high compared to SVPWM. Theoretical investigations were confirmed by the digital simulations using MATLAB/SIMULINK software.

The conventional two levels Inverter have many limitations for high voltage and high power application. Multilevel inverter becomes very popular for high voltage and high power application. The multilevel inverter is started with the three level converters. The elementary concept of a multilevel converter to achieve higher power to use a series of power semiconductor switches with several lower voltage dc source to perform the power conversion by synthesizing a staircase voltage waveform. However, the output voltage is smoother with a three level converter, in which the output voltage has three possible values. This results in smaller harmonics, but on the other hand it has more components and is more complex to control. In this paper, study of different three level inverter topologies and SPWM technique is explain and SPWM technique has been applied to formulate the switching pattern for three level and five level H-Bridge inverter that minimize the harmonic distortion at the inverter output. This paper deals with comparison of simulation results of three levels and five