i am trying to design two stages PV pumping system that consist of PV panels , boost converter , voltage source inverter , induction motor and centrifugal pump . i will use boost converter to track MPP of the PV generator but i can't find a good reference that tell me how to design boost converter that suitable to dynamic load such as induction motor . i attached my design but it gives very bad results.
If the power generated by PV is more or less than of induction motor with connected pump - than system becomes unbalanced: so you do not need MPPT but control to supply power that is needed for motor or you can implement energy storage.
i am using mppt to improve the efficiency of the system , where without MPPT the system will need more PV panels .
In order to design the boost converter you should consider a simplified model of your system. For instance you can replace PV with a voltage source and the VSI inverter as an other voltage source. Then you got a simple DC/DC boost converter. For designing it , you should be aware about the acceptable output voltage tolerance of the boost converter. You can find many examples in every power electronics' book such as: Power Electronics: Converters, Applications, and Design: Ned Mohan
i did already something like this to check the induction motor control, it works very good, but when i replace dc voltage source with PV panels and boost converter i have bad results. .
This article may help you through design of a boost converter operating as an MPPT.
http://dergipark.ulakbim.gov.tr/bajece/article/viewFile/5000102042/5000095126
In two-stage systems, the first stage (boost converter) is almost decoupled from the second stage (VSI) owing to the capacitive dc link. Therefore, if you adopt a good PI controller for the dc link voltage regulator, you can easily design the boost converter without being worried about the second stage. In this way you need only to be aware of the dc link voltage which is the output of the boost converter.
Dear Mohamed
Basically the factors that govern the design of boost converter are Current Ripple Factor(CRF), Voltage Ripple Factor(VRF) and the Switching Frequency(SF)...The CRF and VRF values as per IEC standards are 30% and 5%...With Switching frequency of 20KHz, duty cycle, ripple current and the value of inductor and capacitor can be calculated for your application.
Sinusoidal Pulse width Modulation technique control scheme can be applied for inverters. A high frequency triangular waveform compared with desired frequency sinusoidal reference waveform can generate the PWM signal for inverter.
first you should connect your system with regulated dc supply for testing and debugging purpose,after that you may connect with PV source...you can also use the closed loop controller for stable operation....
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