Dc Converter Is A Device Used For Obtain Variable D.c

The most important advantage of AC drive system is that they can handle more power as compared to DC drive system. The AC drive system is now meeting the various advantages of DC drive system like fast torque response, speed accuracy, robust, simple in design, low cost, light and compact. Rashid has outlined several advantages of AC drives which are lightweight, inexpensive and have low maintenance compared to DC drives. For variable-speed applications, AC motors require power converters, AC voltage controllers in order to control frequency, voltage and current. These power controllers which are relatively complex, more expensive and require advanced feedback control techniques such as model reference, adaptive control, sliding mode control and field oriented control but performance of drive is increased. There are two types of AC drives namely, synchronous motor drives and induction motor drives. Induction motor drives are used in the proposed

Switching power converters offer an easy way to regulate both the frequency and magnitude of the voltage and current applied to a motor shown in fig(1). As a result much higher efficiency and performance can be achieved by these motor drives with less generated noises[3].

Change of converter operating point upon switching: The influence of AC voltage change on firing angles and tap-changer controls.

Simulation of the proposed converter & the results using MATLAB & Simulink can be seen in this

Because of its linear characteristics and ease of controlling it's speed by simple power electronic circuit. The main obstacle for this type of system which has prompted the researchers to focus their studies toward AC machine, such as induction and synchronous machine. The availability of the variable speed drives for induction motor made it dominated in industry. Despite this, the small efficiency in induction motor especially those which have low power rating. The PMBDCM with predominant performance is found to be the solution for the drawbacks of the AC and Induction motors. The characteristics of the PMBDCM is similar to the separately excited DC motor, the difference in controller of PMBDCM which is the same of AC motor controller [2] [6].

Single loop control methods allowed a single voltage control loop to regulate the output voltage. The input current shaping is accomplished in an open loop manner, the duty cycle patterns are predefined by considering in ideal PFC operation. One example in this control method is the duty phase control (DPC) proposed by Chen [42]. In this method, a phase shift is willingly introduced to the stored duty cycle patterns. The output voltage is regulated by adjusting this phase shift by using the output of the voltage error amplifier, which is named “the duty phase”. This approach simplified the control structure and eliminated the current loop, without the need to

Now a days, the switching power supply market is flourishing quickly. The trend is for DC-AC converters with low cost, higher efficiency, power saving that enable maximum features. In this project, a single-stage three-switch buck-boost inverter is designed, where stepping up, stepping down and inversion operation will takes place in single stage. This proposed inverter will overcome all the drawbacks of traditional one. Coupled inductor plays a very important role in energy transfer and eliminates the use of line frequency transformer. As the inverter having only three switches, the controlling of switches also easier than conventional one. And it has also advantages like compact design, reduced switching losses, component size, and cost.

D.C Motor is used for variable speed operation because in dc motor torque and flux that can be control independently and that is achieved by armature and field current control respectively. D.C motor has many advantages delivering high starting torque, ease of control and non linear performance. But due to certain disadvantage of dc machine such as mechanical commutator and brush holder required time to time maintenance [1] .So cost of the drive system is increases. But now D.C Motor is less used in industrial applications. Because of low cost, better performance and the requirement of maintenance is less as compared to D.C Motor it make the asynchronous motor advantageous in many industrial applications. SCIM are most widely used than all the rest of the electric motor as they have all the advantages of A.C Motors and are cheaper in cost as compared to slip ring induction motor. Because of absence of slip rings, brush maintenance duration and cost associated with the wear and tear of brush are minimized. Because of these advantages, the induction motor is used in element of most of the electrical drive system for all the conditions like starting, braking, change in speed and speed reversal. To achieve the maximum efficiency of the induction motor drive, so many techniques are developed in the last few years. Now a day’s high switching frequency converters are used for changing the frequency, phase and amplitude of the input to an A.C. Motor can be changed, hence the speed and motor torque can be controlled. With the help of power electronic it is possible to

Modren HVDC systems are having many advantages than HVAC sytems. Two AC systems are connected using a new VSC-MMC based Hybrid HVDC system in this paper which gives many advantages than the conventional HVDC systems and LCC-VSC Hybrid systems. The proposed system gives the fast dynamic response by using different control stratagies. The active and reactive power is controlled and the dc line voltage is maintained constant at inverter station. Under steady state and transient conditions the system performance is investigated by MATLAB simulations. The results show the feasibility of the hybrid system.

[1] Hung-Liang Cheng, Yao-Ching Hsieh, and Chi-Sean Lin, “Novel Single-stage HPF AC/DC Converter Featuring High Circuit Efficiency”, IEEE transactions on Industrial Electronics, vol. 58, no.2, august 2012.

This chapter deals with the classification and basic operation of electric variable speed drive system and scope, merits and demerits of DC and AC drives. Then AC induction motor drive is selected for complete description. Here AC drive system is presented with its components like inverters, position sensors and current controller.

Many of these conventional DC–DC converters have the disadvantages of operating at high duty-cycle, high switch voltage stress and high diode peak current. The conventional boost high step-up converter can provide very high voltage gain without operating at high duty-cycle by employing a coupled inductor, a switched capacitor and an additional diode. Non-isolated high step up converter overcomes this drawback. This converter reduces voltage stress on switch and diode by using additional one capacitor and rearranging components in conventional single switch high step-up converter. At the same time, the switch voltage stress is reduced greatly, which is helpful to reduce the conduction losses by using low power rated components and efficiency will increase. Single switch is used in the non-isolated high step up converter, thus reduce the entire cost of the converter. This non-isolated high step-up converter is used in many applications such as renewable energy system using low voltage energy sources such as fuel cells, solar panels,

Hence, the proposed variable switching frequency PWM reduces the switching instances within a fundamental cycle by lowering the effective switching frequency, while maintaining the output current ripple within a pre-defined range.

Space Vector PWM (SVPWM) refers to a special switching sequence of the upper three power transistors of a three-phase power inverter. It has been shown to generate less harmonic distortion in the output voltages and or currents applied to the phases of an AC motor and to provide more efficient use of supply voltage compared with sinusoidal modulation technique. The biggest difference from other PWM methods is that the SVPWM uses a vector as a reference. This gives the advantage of a better overview of the system.

The electrical power is alternating current but DC motors needs a rectifier to convert that into direct current.