This paper proposed Novel power factor corrected ac dc rectifier typologies suitable for induction motor drive based elevator application. These converters make use of coupled induct or for power conversion and are capable of providing high voltage gain at low duty cycle and high efficiency. Feedback control loop controls the current flowing through the coupled induct or to achieve unity power factor. The TH D value of the current i approximately 4.8 % which is within the limits prescribed by various standards.
the use of coupled induct or, the voltage stress of the switches operating at high frequency is reduced, which reduces switching losses. The loss comparison with the conventional converters shows a reduction of at least 22 % of losses. The proposed scheme also results in reduction of the variable frequency drive’s dc link capacitance value. As an ultra capacitor bank is interfaced with the dc link through a bidirectional converter for improving efficiency and providing transient power requirements. This also helps in increasing the reliability and dynamic response of the system. The settling time for a step change in voltage reference is reduced by nearly 50%. MAT LAB/Sim u link simulations validates the proposed typologies and schemes.
Fig. 1 Block diagram of an elevator system
EXPECTED SIMULATION RESULTS:
Fig. 2(a) Input current and voltage of the proposed 1 p h rectifier system with PFC; (b)3 p h current for PFC operation of proposed rectifier configuration; (c) The dc link voltage step changes for 10μF and 500μF dc link capacitor; and (d) Ultra capacitor current.
Simulation studies proposed, analyzed and validated the Novel AC DC PW M rectifier typologies for 1 p h and 3 p h systems, based on high voltage gain dc dc converter principle. A major advantage of these typologies is that it is possible to achieve higher voltage gain at lower duty ratio. This paper maintained operation symmetry and achieved the Input power factor correction. The use of coupled induct or s enhances gain, but it also increases the ripple in the input current as there is an increase in turns ratio. Thus, there is a trade off between the achievable gain and the ripple.
The losses of the proposed converter are compared with the conventional ac dc converter, and observed the reduction of about 22% losses. The losses estimated through experimental studies also reduced from 29 W to 24 W with the use of proposed topology . This shows a reduction of 17% losses in experiments. Therefore, the proposed converter gives higher efficiency than the conventional ac-dc converters. And the use of an auxiliary storage reduced the dc link capacitance value from 500 μF to 10 μF for a 1 p h system. For the 3 p h system, the auxiliary unit is used as a support during the grid voltage sag condition thereby reducing the dc link capacitance requirement. A low value of dc link capacitance not only helps in reducing the size. And improving the reliability of system, also in improving the dynamic response of the system.
The paper presented the simulation results of the complete system . A detailed description of the thought process behind the development of the proposed converter is also presented. The same thought process is extended to the development of such converter typologies. The voltage stress on switch S 2 and S 3 reduces to 1 and 8th of its value as compared to the conventional topology. But, the value of peak current increases ‘n’ times. The increase in peak current increases the high frequency current ripple in the input side. However, the increase in the value of ‘n’ decreases the duty cycle. Therefore, increased the overall efficiency of the converter.
paper proposed the unidirectional ac dc typologies. But, they can be made bidirectional by connecting a controllable switch across the diodes. This scheme is useful for the scenarios where the loads are regenerating. These bidirectional typologies are used as dc ac converters to feed power into the grid. Thus, giving very wide and relevant scope of the proposed schemes.
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